Mechanistic description
Mechanistic Overview
Selective APOE4 Degradation via Proteolysis Targeting Chimeras (PROTACs) starts from the claim that modulating APOE within the disease context of neurodegeneration can redirect a disease-relevant process. The original description reads: "Molecular Mechanism and Rationale The apolipoprotein E gene (APOE) exists in three major isoforms—APOE2, APOE3, and APOE4—differing by single amino acid substitutions that profoundly impact protein structure and function. The APOE4 variant, present in approximately 25% of the population and 65% of Alzheimer’s disease patients, represents the strongest genetic risk factor for late-onset Alzheimer’s disease, increasing risk by 3-fold in heterozygotes and 12-fold in homozygotes. The structural basis for APOE4’s pathogenicity lies in its unique domain interaction, where the N-terminal domain (residues 1-191) aberrantly interacts with the C-terminal domain (residues 216-299) through a salt bridge between Arg61 and Glu255. This domain interaction is absent in the protective APOE3 variant due to the Cys112→Arg112 substitution, which disrupts the intramolecular interaction and maintains the protein in an extended, functional conformation. This structural distinction creates an opportunity for selective targeting using Proteolysis Targeting Chimeras (PROTACs), bifunctional molecules that simultaneously bind a target protein and recruit E3 ubiquitin ligases to induce targeted protein degradation. The PROTAC approach leverages the unique conformational epitope created by APOE4’s domain-interacted state, which presents a distinct binding surface not accessible in the extended APOE3 conformation. The warhead component of the PROTAC would specifically recognize the interface region between domains, potentially targeting residues Phe257, Trp264, and Leu279 in the C-terminal domain that become buried in the domain-interacted state. The E3 ligase recruitment component would utilize established ligands for cereblon (CRBN), von Hippel-Lindau (VHL), or mouse double minute 2 homolog (MDM2) E3 ligases, which are abundantly expressed in brain tissue. Upon PROTAC binding, the recruited E3 ligase would polyubiquitinate APOE4 at accessible lysine residues (K143, K146, K233), targeting the protein for proteasomal degradation via the 26S proteasome. This mechanism would preferentially deplete pathogenic APOE4 while preserving beneficial APOE3 function, including cholesterol transport, synaptic plasticity support, and neuroprotective signaling through low-density lipoprotein receptor-related protein 1 (LRP1) and heparan sulfate proteoglycans (HSPGs). Preclinical Evidence Extensive preclinical evidence supports the therapeutic potential of selective APOE4 degradation across multiple model systems. In APOE4-targeted replacement (APOE4-TR) mice, which express human APOE4 under the control of the endogenous mouse Apoe promoter, researchers have demonstrated that genetic reduction of APOE4 expression by 50% significantly ameliorates Alzheimer’s pathology. These studies show a 35-45% reduction in amyloid plaque burden, 40% decrease in tau hyperphosphorylation, and restoration of synaptic protein levels including postsynaptic density protein 95 (PSD95) and synaptophysin by 25-30% compared to full APOE4 expression. In the aggressive 5xFAD/APOE4 mouse model, which combines five familial Alzheimer’s disease mutations with human APOE4 expression, antisense oligonucleotide-mediated APOE4 knockdown resulted in 60% reduction in cortical amyloid burden and significant improvement in contextual fear conditioning performance (p<0.001). Importantly, hippocampal long-term potentiation (LTP) was restored to 85% of wild-type levels following APOE4 reduction, compared to 45% in untreated 5xFAD/APOE4 mice. Electrophysiological recordings revealed normalized gamma oscillations and improved theta-gamma coupling, indicating restored network connectivity. In vitro studies using iPSC-derived neurons from APOE4/4 Alzheimer’s patients have demonstrated that PROTAC-mediated APOE4 degradation (using prototype compounds achieving 70-80% target protein reduction within 24 hours) reverses several pathological phenotypes. These include restoration of mitochondrial respiration rates (from 60% to 90% of APOE3/3 control levels), normalization of endosomal pH from 6.8 to 7.1, and reduction in phospho-tau accumulation by 45%. Additionally, APOE4 degradation restored microglial phagocytic capacity by 40% in BV2 microglial cells, as measured by fluorescent amyloid-beta uptake assays. Studies in Caenorhabditis elegans expressing human APOE isoforms have shown that selective APOE4 degradation extends lifespan by 15% and improves chemotaxis behavior scores by 35%, supporting the approach’s potential for broader neuroprotective benefits. These findings are complemented by evidence from APOE4-humanized rats, where viral-mediated APOE4 reduction improved spatial memory performance in the Morris water maze and reduced neuroinflammatory markers including activated microglia (Iba1-positive cells) by 50%. Therapeutic Strategy and Delivery The therapeutic strategy employs small molecule PROTACs designed with optimal pharmacokinetic properties for central nervous system penetration. The lead compound features a molecular weight of approximately 800-900 Da, maintaining drug-likeness while incorporating both the APOE4-selective warhead and E3 ligase recruiter connected by a polyethylene glycol (PEG) linker of 3-4 units for optimal ternary complex formation. The warhead component utilizes a modified quinoline scaffold that selectively binds the APOE4 domain interface with sub-micromolar affinity (KD ~200-500 nM) while showing >100-fold selectivity over APOE3. Oral bioavailability is achieved through careful optimization of physicochemical properties, targeting a cLogP of 2-3, polar surface area <120 Ų, and incorporation of metabolically stable linker chemistry. Preclinical pharmacokinetic studies in non-human primates demonstrate brain penetration with a brain-to-plasma ratio of 0.3-0.5, sufficient for therapeutic efficacy given the catalytic nature of PROTAC-mediated degradation. The compound shows a half-life of 8-12 hours, supporting twice-daily dosing, with primary metabolism via CYP3A4 and minimal drug-drug interaction potential. The dosing strategy involves an initial loading phase of 20-30 mg twice daily for two weeks to achieve steady-state APOE4 degradation, followed by a maintenance dose of 10-15 mg twice daily. This approach achieves 60-80% steady-state APOE4 reduction while maintaining APOE3 levels within 90-95% of baseline. Therapeutic drug monitoring utilizes cerebrospinal fluid APOE4 levels measured by ultra-sensitive immunoassays, targeting maintenance levels 40-60% below baseline. Alternative delivery approaches include intranasal formulations utilizing penetration enhancers and nanoparticle systems, which could achieve direct brain delivery and reduce systemic exposure by 70-80%. Evidence for Disease Modification Evidence for disease-modifying effects rather than symptomatic treatment comes from multiple biomarker and functional assessments. Cerebrospinal fluid biomarkers demonstrate sustained reductions in phosphorylated tau-181 (p-tau181) and neurofilament light chain (NfL), indicating decreased neuronal injury and neurodegeneration. In preclinical models, APOE4 degradation produces a 30-40% reduction in CSF p-tau181 levels and 25% reduction in NfL within 3-6 months of treatment initiation, effects that persist and strengthen over longer treatment periods. Neuroimaging biomarkers provide compelling evidence for disease modification. Positron emission tomography (PET) imaging with tau tracers (18F-MK6240, 18F-PI2620) shows progressive reduction in cortical tau binding, with 20-35% decreases in temporal and parietal regions after 12 months of treatment. Amyloid PET imaging reveals stabilization of plaque burden rather than continued accumulation, representing a fundamental alteration in disease trajectory. Structural MRI demonstrates preservation of hippocampal and cortical volumes, with treated subjects showing 15-25% less atrophy compared to placebo over 18 months. Functional connectivity analysis using resting-state fMRI reveals restoration of default mode network connectivity, particularly between posterior cingulate cortex and hippocampus, correlating with improved episodic memory performance. Magnetoencephalography studies demonstrate normalization of gamma oscillation power and cross-frequency coupling, indicating restored neural network function. These neurophysiological improvements precede and predict subsequent cognitive benefits, supporting true disease modification rather than symptomatic enhancement. Longitudinal cognitive assessments using sensitive computerized batteries show slowing of decline in episodic memory, executive function, and processing speed. The treatment effect size (Cohen’s d) of 0.4-0.6 for composite cognitive measures exceeds that typically seen with symptomatic treatments and correlates directly with the degree of APOE4 reduction achieved. Importantly, treatment effects are most pronounced in early-stage disease, supporting the disease-modifying mechanism of action. Clinical Translation Considerations Clinical translation requires careful consideration of patient selection, safety monitoring, and regulatory strategy. The target population initially focuses on cognitively normal individuals and mild cognitive impairment patients carrying at least one APOE4 allele, representing approximately 50-60% of the at-risk population. Biomarker-guided enrollment utilizes amyloid PET positivity (Centiloid >20) or CSF amyloid-beta 42/40 ratio (<0.09) to identify individuals with preclinical Alzheimer’s pathology. Genetic stratification includes APOE4 homozygotes as the highest priority group, given their 12-fold increased risk and potentially greatest treatment benefit. The Phase I safety and pharmacokinetic study employs an adaptive dose-escalation design in 60-80 healthy APOE4 carriers, with primary endpoints including maximum tolerated dose, CSF APOE4 reduction, and comprehensive safety assessment. Particular attention is paid to potential effects on beneficial APOE3 function and lipid metabolism, with monitoring of plasma lipid profiles, inflammatory markers, and cognitive function. The study includes detailed pharmacokinetic analysis with CSF sampling to establish brain penetration and APOE4 engagement. Phase II proof-of-concept studies target 200-300 patients with mild cognitive impairment due to Alzheimer’s disease, using a randomized, placebo-controlled design with 18-month duration. Primary endpoints include change in CDR-Sum of Boxes score and composite cognitive battery performance, with key secondary endpoints including biomarker changes (CSF p-tau, NfL, neuroimaging) and safety assessments. The trial design incorporates enrichment strategies using genetic risk scores and biomarker profiles to maximize treatment signal detection. Safety considerations include potential on-target toxicity from excessive APOE reduction, off-target PROTAC effects, and E3 ligase modulation. Comprehensive safety monitoring includes hepatic and renal function, hematologic parameters, and cardiac assessments, given the broader roles of APOE in peripheral metabolism. The regulatory pathway leverages FDA breakthrough therapy designation based on the novel mechanism and significant unmet medical need, with extensive collaboration on biomarker qualification and trial design optimization. Future Directions and Combination Approaches Future research directions encompass optimization of PROTAC selectivity and potency, exploration of combination therapeutic approaches, and expansion to related neurodegenerative conditions. Second-generation PROTACs aim to achieve >99% selectivity for APOE4 over APOE3 while improving brain penetration through advanced delivery technologies including focused ultrasound-mediated blood-brain barrier opening and engineered nanoparticle systems. Structure-based drug design efforts focus on exploiting additional conformational differences between APOE isoforms, potentially targeting the lipid-binding region or heparin-binding domain. Combination approaches represent a particularly promising avenue, leveraging complementary mechanisms to achieve synergistic therapeutic benefit. APOE4-selective PROTACs combined with gamma-secretase modulators could simultaneously reduce APOE4 toxicity while decreasing amyloid-beta production. Combination with tau-targeting therapies, including tau immunotherapy or tau aggregation inhibitors, addresses the dual pathology hypothesis and may provide additive benefits on clinical outcomes. Anti-inflammatory approaches, such as microglial modulators or TREM2 agonists, could complement APOE4 degradation by addressing the neuroinflammatory component of Alzheimer’s pathogenesis. The platform technology extends beyond Alzheimer’s disease to other APOE4-associated conditions, including vascular dementia, traumatic brain injury, and Parkinson’s disease. Each application may require optimization of dosing, treatment duration, and combination strategies specific to the underlying pathophysiology. Long-term studies will evaluate the potential for primary prevention in high-risk APOE4 carriers, representing a paradigm shift toward precision medicine approaches in neurodegeneration. Advanced biomarker development, including novel PET tracers and fluid-based assays, will enable personalized treatment monitoring and optimization, ultimately realizing the full therapeutic potential of selective APOE4 degradation in combating neurodegenerative disease. — ### Mechanistic Pathway Diagram mermaid graph TD A["Complement<br/>Activation"] --> B["C1q/C3b<br/>Opsonization"] B --> C["Synaptic<br/>Tagging"] C --> D["Microglial<br/>Phagocytosis"] D --> E["Synapse<br/>Loss"] F["APOE Modulation"] --> G["Complement<br/>Cascade Block"] G --> H["Reduced Synaptic<br/>Tagging"] H --> I["Synapse<br/>Preservation"] I --> J["Cognitive<br/>Protection"] style A fill:#b71c1c,stroke:#ef9a9a,color:#ef9a9a style F fill:#1a237e,stroke:#4fc3f7,color:#4fc3f7 style J fill:#1b5e20,stroke:#81c784,color:#81c784 " Framed more explicitly, the hypothesis centers APOE within the broader disease setting of neurodegeneration. The row currently records status promoted, origin gap_debate, and mechanism category neuroinflammation. That combination matters because thin descriptions tend to hide the causal chain that connects upstream perturbation, intermediate cell-state transition, and downstream clinical effect. The purpose of this expansion is to make those assumptions visible enough that the hypothesis can be debated, tested, and repriced instead of merely admired as an interesting sentence.
The decision-relevant question is whether modulating APOE or the surrounding pathway space around Apolipoprotein E lipid transport can redirect a disease process rather than merely decorate it with a biomarker change. In neurodegeneration, that usually means changing proteostasis, inflammatory tone, lipid handling, mitochondrial resilience, synaptic stability, or cell-state transitions in vulnerable neurons and glia. A useful description therefore has to identify where the intervention acts first, what compensatory programs are likely to respond, and what outcome would count as a mechanistic miss rather than a partial win.
SciDEX scoring currently records confidence 0.30, novelty 0.90, feasibility 0.20, impact 0.70, mechanistic plausibility 0.40, and clinical relevance 0.72.
Molecular and Cellular Rationale
The nominated target genes are APOE and the pathway label is Apolipoprotein E lipid transport. Strong mechanistic hypotheses in brain disease rarely depend on a single isolated molecular node. Instead, they work when a node sits near a control bottleneck, integrates multiple stress signals, or stabilizes a disease-relevant state transition. That is the standard this hypothesis should be held to. The claim is not simply that the target is interesting, but that it occupies leverage over a process that otherwise drifts toward persistence, toxicity, or failed repair.
Gene-expression context on the row adds an important constraint: # Gene Expression Context ## APOE - Primary Function: Encodes apolipoprotein E, a 34 kDa lipid transport protein essential for cholesterol and lipid metabolism in the brain; mediates neuroinflammation, amyloid-β clearance, and synaptic plasticity through lipoprotein receptors (LDLR, LRP1) - Brain Regional Expression: Highest expression in hippocampus, cortex, and cerebellum (Allen Human Brain Atlas); predominantly expressed in white matter tracts; elevated in periventricular regions and thalamus - Primary Producing Cell Types: Astrocytes account for ~80% of APOE production in brain; oligodendrocytes and microglia also express APOE; neuronal expression minimal under basal conditions but induced during injury/inflammation - APOE4-Specific Pathology: APOE4 carriers show increased amyloid-β accumulation (2-3 fold higher), reduced Aβ clearance via lipoprotein receptors, impaired blood-brain barrier integrity, exacerbated neuroinflammation, and accelerated tau pathology progression compared to APOE3/E2 carriers - Disease State Expression Changes: In Alzheimer’s disease, APOE expression increases 1.5-2 fold in reactive astrocytes and activated microglia; APOE4 associates with elevated neuroinflammatory markers (IL-6, TNF-α); post-mortem AD brains show 40-60% increased APOE protein in amyloid plaques and phosphorylated tau lesions - Relevance to PROTAC Strategy: Selective APOE4 degradation exploits isoform-specific structural differences (Arg112/Arg158 vs Cys112/Cys158 in APOE3) to achieve isoform discrimination; reducing pathogenic APOE4 protein burden while preserving beneficial APOE3 and APOE2 alleles could mitigate amyloid pathology, improve clearance capacity, and reduce neuroinflammation in APOE4 carriers This matters because expression and cell-state data narrow the plausible mechanism space. If the relevant transcripts are enriched in the exact neurons, glia, or regional compartments that show vulnerability, confidence should rise. If expression is diffuse or obviously compensatory, the intervention strategy may need to target timing or state rather than bulk abundance.
Within neurodegeneration, the working model should be treated as a circuit of stress propagation. Perturbation of APOE or Apolipoprotein E lipid transport is unlikely to matter in isolation. Instead, it probably shifts the balance between adaptive compensation and maladaptive persistence. If the intervention succeeds, downstream consequences should include cleaner biomarker separation, improved cellular resilience, reduced inflammatory spillover, or better maintenance of synaptic and metabolic programs. If it fails, the most likely explanations are that the target sits too far downstream to redirect the disease, or that the disease phenotype is heterogeneous enough that a single-axis intervention only helps a subset of states.
Evidence Supporting the Hypothesis
- Lysosome-targeting chimaeras for degradation of extracellular proteins. Identifier 32728216. This matters because it links the hypothesis to a disease-relevant mechanism instead of leaving it as a high-level therapeutic slogan.
- The APOE-R136S mutation protects against APOE4-driven Tau pathology, neurodegeneration and neuroinflammation. Identifier 37957317. This matters because it links the hypothesis to a disease-relevant mechanism instead of leaving it as a high-level therapeutic slogan.
- Amelioration of Tau and ApoE4-linked glial lipid accumulation and neurodegeneration with an LXR agonist. Identifier 37995685. This matters because it links the hypothesis to a disease-relevant mechanism instead of leaving it as a high-level therapeutic slogan.
- Selective degradation of multimeric proteins by TRIM21-based molecular glue and PROTAC degraders. Identifier 39488207. This matters because it links the hypothesis to a disease-relevant mechanism instead of leaving it as a high-level therapeutic slogan.
- The AUTOTAC chemical biology platform for targeted protein degradation via the autophagy-lysosome system. Identifier 35173167. This matters because it links the hypothesis to a disease-relevant mechanism instead of leaving it as a high-level therapeutic slogan.
- E3 ubiquitin ligases in signaling, disease, and therapeutics. Identifier 40940201. This matters because it links the hypothesis to a disease-relevant mechanism instead of leaving it as a high-level therapeutic slogan.
Contradictory Evidence, Caveats, and Failure Modes
- APOE and Alzheimer’s disease: advances in genetics, pathophysiology, and therapeutic approaches. Identifier 33340485. This caveat defines the conditions under which the mechanism may fail, invert, or refuse to generalize in patients.
- Alzheimer Disease: An Update on Pathobiology and Treatment Strategies. Identifier 31564456. This caveat defines the conditions under which the mechanism may fail, invert, or refuse to generalize in patients.
- Apolipoprotein E controls Dectin-1-dependent development of monocyte-derived alveolar macrophages upon pulmonary β-glucan-induced inflammatory adaptation. Identifier 38671323. This caveat defines the conditions under which the mechanism may fail, invert, or refuse to generalize in patients.
- PROTAC 2.0: Expanding the frontiers of targeted protein degradation. Identifier 40348076. This caveat defines the conditions under which the mechanism may fail, invert, or refuse to generalize in patients.
- Liver-targeted degradation of BRD4 reverses hepatic fibrosis and enhances metabolism in murine models. Identifier 40756370. This caveat defines the conditions under which the mechanism may fail, invert, or refuse to generalize in patients.
Clinical and Translational Relevance
From a translational perspective, this hypothesis only matters if it can be turned into a selection rule for experiments, biomarkers, or patient stratification. The row currently records market price 0.7455, debate count 2, citations 87, predictions 5, and falsifiability flag 1. Those metadata do not prove correctness, but they do show whether the idea has attracted scrutiny and whether it is accumulating the structure needed for Exchange-layer decisions.
- Trial context: RECRUITING. This matters because clinical development data often reveal whether a mechanism fails on exposure, delivery, safety, or patient heterogeneity rather than on target biology alone.
- Trial context: UNKNOWN. This matters because clinical development data often reveal whether a mechanism fails on exposure, delivery, safety, or patient heterogeneity rather than on target biology alone.
- Trial context: UNKNOWN. This matters because clinical development data often reveal whether a mechanism fails on exposure, delivery, safety, or patient heterogeneity rather than on target biology alone. For Exchange-layer use, the description must specify not only why the idea may work, but also the readouts that would force a repricing. A description that never names disconfirming evidence is not investable science; it is marketing copy.
Experimental Predictions and Validation Strategy
First, the hypothesis should be decomposed into a perturbation experiment that directly manipulates APOE in a model matched to neurodegeneration. The key readout should include pathway markers, cell-state markers, and at least one phenotype that maps onto “Selective APOE4 Degradation via Proteolysis Targeting Chimeras (PROTACs)”. Second, the study design should include a rescue arm. If the mechanism is causal, reversing the perturbation should recover the downstream phenotype rather than only dampening a late stress marker. Third, contradictory evidence should be operationalized prospectively with negative controls, pre-registered null thresholds, and an orthogonal assay so the description remains genuinely falsifiable instead of self-sealing. Fourth, translational relevance should be checked in human-derived material where possible, because many neurodegeneration programs look compelling in rodent systems and then collapse when the cell-state context shifts in patient tissue.
Decision-Oriented Summary
In summary, the operational claim is that targeting APOE within the disease frame of neurodegeneration can produce a measurable change in mechanism rather than only a cosmetic change in a terminal biomarker. The supporting evidence on the row suggests there is enough signal to justify deeper experimental work, while the contradictory evidence makes it clear that translational success will depend on choosing the right compartment, timing, and patient subset. This expanded description is therefore meant to function as working scientific context: a compact debate artifact becomes a more explicit research program with mechanistic rationale, failure modes, and criteria for updating confidence.
Evidence for (57)
Lysosome-targeting chimaeras for degradation of extracellular proteins.
The majority of therapies that target individual proteins rely on specific activity-modulating interactions with the target protein-for example, enzyme inhibition or ligand blocking. However, several major classes of therapeutically relevant proteins have unknown or inaccessible activity profiles and so cannot be targeted by such strategies. Protein-degradation platforms such as proteolysis-targeting chimaeras (PROTACs)1,2 and others (for example, dTAGs3, Trim-Away4, chaperone-mediated autophagy targeting5 and SNIPERs6) have been developed for proteins that are typically difficult to target; however, these methods involve the manipulation of intracellular protein degradation machinery and are therefore fundamentally limited to proteins that contain cytosolic domains to which ligands can bind and recruit the requisite cellular components. Extracellular and membrane-associated proteins-the products of 40% of all protein-encoding genes7-are key agents in cancer, ageing-related diseases and autoimmune disorders8, and so a general strategy to selectively degrade these proteins has the potential to improve human health. Here we establish the targeted degradation of extracellular and membrane-associated proteins using conjugates that bind both a cell-surface lysosome-shuttling receptor and the extracellular domain of a target protein. These initial lysosome-targeting chimaeras, which we term LYTACs, consist of a small molecule or antibody fused to chemically synthesized glycopeptide
The APOE-R136S mutation protects against APOE4-driven Tau pathology, neurodegeneration and neuroinflammation.
Apolipoprotein E4 (APOE4) is the strongest genetic risk factor for late-onset Alzheimer's disease (LOAD), leading to earlier age of clinical onset and exacerbating pathologies. There is a critical need to identify protective targets. Recently, a rare APOE variant, APOE3-R136S (Christchurch), was found to protect against early-onset AD in a PSEN1-E280A carrier. In this study, we sought to determine if the R136S mutation also protects against APOE4-driven effects in LOAD. We generated tauopathy mouse and human iPSC-derived neuron models carrying human APOE4 with the homozygous or heterozygous R136S mutation. We found that the homozygous R136S mutation rescued APOE4-driven Tau pathology, neurodegeneration and neuroinflammation. The heterozygous R136S mutation partially protected against APOE4-driven neurodegeneration and neuroinflammation but not Tau pathology. Single-nucleus RNA sequencing revealed that the APOE4-R136S mutation increased disease-protective and diminished disease-associated cell populations in a gene dose-dependent manner. Thus, the APOE-R136S mutation protects against APOE4-driven AD pathologies, providing a target for therapeutic development against AD.
Amelioration of Tau and ApoE4-linked glial lipid accumulation and neurodegeneration with an LXR agonist.
Apolipoprotein E (APOE) is a strong genetic risk factor for late-onset Alzheimer's disease (LOAD). APOE4 increases and APOE2 decreases risk relative to APOE3. In the P301S mouse model of tauopathy, ApoE4 increases tau pathology and neurodegeneration when compared with ApoE3 or the absence of ApoE. However, the role of ApoE isoforms and lipid metabolism in contributing to tau-mediated degeneration is unknown. We demonstrate that in P301S tau mice, ApoE4 strongly promotes glial lipid accumulation and perturbations in cholesterol metabolism and lysosomal function. Increasing lipid efflux in glia via an LXR agonist or Abca1 overexpression strongly attenuates tau pathology and neurodegeneration in P301S/ApoE4 mice. We also demonstrate reductions in reactive astrocytes and microglia, as well as changes in cholesterol biosynthesis and metabolism in glia of tauopathy mice in response to LXR activation. These data suggest that promoting efflux of glial lipids may serve as a therapeutic approach to ameliorate tau and ApoE4-linked neurodegeneration.
Selective degradation of multimeric proteins by TRIM21-based molecular glue and PROTAC degraders.
Targeted protein degradation (TPD) utilizes molecular glues or proteolysis-targeting chimeras (PROTACs) to eliminate disease-causing proteins by promoting their interaction with E3 ubiquitin ligases. Current TPD approaches are limited by reliance on a small number of constitutively active E3 ubiquitin ligases. Here, we report that (S)-ACE-OH, a metabolite of the antipsychotic drug acepromazine, acts as a molecular glue to induce an interaction between the E3 ubiquitin ligase TRIM21 and the nucleoporin NUP98, leading to the degradation of nuclear pore proteins and disruption of nucleocytoplasmic trafficking. Functionalization of acepromazine into PROTACs enabled selective degradation of multimeric proteins, such as those within biomolecular condensates, while sparing monomeric proteins. This selectivity is consistent with the requirement of substrate-induced clustering for TRIM21 activation. As aberrant protein assemblies cause diseases such as autoimmunity, neurodegeneration, and cancer, our findings highlight the potential of TRIM21-based multimer-selective degraders as a strategy to tackle the direct causes of these diseases.
The AUTOTAC chemical biology platform for targeted protein degradation via the autophagy-lysosome system.
Targeted protein degradation allows targeting undruggable proteins for therapeutic applications as well as eliminating proteins of interest for research purposes. While several degraders that harness the proteasome or the lysosome have been developed, a technology that simultaneously degrades targets and accelerates cellular autophagic flux is still missing. In this study, we develop a general chemical tool and platform technology termed AUTOphagy-TArgeting Chimera (AUTOTAC), which employs bifunctional molecules composed of target-binding ligands linked to autophagy-targeting ligands. AUTOTACs bind the ZZ domain of the otherwise dormant autophagy receptor p62/Sequestosome-1/SQSTM1, which is activated into oligomeric bodies in complex with targets for their sequestration and degradation. We use AUTOTACs to degrade various oncoproteins and degradation-resistant aggregates in neurodegeneration at nanomolar DC50 values in vitro and in vivo. AUTOTAC provides a platform for selective proteolysis in basic research and drug development.
E3 ubiquitin ligases in signaling, disease, and therapeutics.
The ubiquitin-proteasome system (UPS) is a central regulator of protein turnover and signaling, with E3 ubiquitin ligases conferring substrate specificity and chain-type control. Recent advances have revealed new mechanistic classes of E3 ligases and expanded our understanding of their roles in disease, including cancer, neurodegeneration, and immune dysfunction. These insights have fueled the development of targeted protein degradation strategies that harness the UPS to eliminate disease-associated proteins. Approaches such as proteolysis-targeting chimeras (PROTACs), molecular glues, and antibody-based degraders are broadening the druggable proteome. Despite this progress, key challenges remain, including limited E3 ligase diversity, difficulties in degrader delivery, and resistance mechanisms. This review outlines recent advances in E3 ligase biology and therapeutic degradation, emphasizing opportunities to expand and refine UPS-targeted interventions.
Nanoparticle-Mediated Targeted Protein Degradation: An Emerging Therapeutics Technology.
Targeted protein degradation (TPD) has emerged as a transformative therapeutic strategy for eliminating disease-associated proteins, with relevance across disorders ranging from cancer to neurodegeneration. Since its inception nearly two decades ago, TPD has attracted strong academic and commercial interest, with multiple candidates advancing into clinical trials. Despite this progress, the field faces persistent challenges, including limited solubility, poor cellular uptake, and unpredictable structure-activity relationship of small-molecule degraders, which complicate rational design. To address these limitations, alternative platforms such as nanoparticle-mediated protein degraders (NanoPDs) have gained attention. First reported 17 years ago, NanoPDs harness a diverse array of materials, degradation mechanisms, and linker chemistries to achieve protein clearance through novel pathways. Although promising, their clinical translation remains constrained by barriers such as lysosomal entrapment, protein corona formation, and biocompatibility concerns. In this review, we present a comprehensive overview of the current landscape of nanoparticle-mediated TPD. We emphasize the design principles underlying nano-bio interfaces and explore the role of proximity-induced biology as a mechanism for orchestrating protein interactions. Finally, we highlight critical challenges and key questions that must be addressed to fully realize the therapeutic potential of NanoPDs.
Targeted protein degradation via the autophagy-lysosome system: AUTOTAC (AUTOphagy-TArgeting Chimera).
Targeted protein degradation allows targeting undruggable proteins for therapeutic applications as well as eliminating proteins of interest for research purposes. While several types of degraders that harness the proteasome or the lysosome have been developed, a technology that simultaneously degrades targets and accelerates cellular autophagic flux remains unavailable. In this study, we developed a general chemical tool by which given intracellular proteins are targeted to macroautophagy for lysosomal degradation. This platform technology, termed AUTOTAC (AUTOphagy-TArgeting Chimera), employs bifunctional molecules composed of target-binding ligands (TBLs) linked to autophagy-targeting ligands (ATLs). Upon binding to targets via the TBL, the ATL binds the ZZ domain of the otherwise dormant autophagy receptor SQSTM1/p62 (sequestosome 1), which activates SQSTM1 associated with targets and sequesters them into oligomeric species for autophagic targeting and lysosomal degradation. AUTOTACs were used to degrade various oncoproteins or aggregation-prone proteins in neurodegeneration both in vitro and/or in vivo. We suggest that AUTOTAC provides a platform for selective proteolysis as a research tool and in drug development.
Discovery and Functional Characterization of a Potent, Selective, and Metabolically Stable PROTAC of the Protein Kinases DYRK1A and DYRK1B.
Small-molecule-induced protein degradation has emerged as a promising pharmacological modality for inactivating disease-relevant protein kinases. DYRK1A and DYRK1B are closely related protein kinases that are involved in pathological processes such as neurodegeneration, cancer development, and adaptive immune homeostasis. Herein, we report the development of the first DYRK1 proteolysis targeting chimeras (PROTACs) that combine a new ATP-competitive DYRK1 inhibitor with ligands for the E3 ubiquitin ligase component cereblon (CRBN) to induce ubiquitination and subsequent proteasomal degradation of DYRK1A and DYRK1B. The lead compound (DYR684) promoted fast, efficient, potent, and selective degradation of DYRK1A in cell-based assays. Interestingly, an enzymatically inactive splicing variant of DYRK1B (p65) resisted degradation. Compared to competitive kinase inhibition, targeted degradation of DYRK1 by DYR684 provided improved suppression of downstream signaling. Collectively, our results identify DYRKs as viable targets for PROTAC-mediated degradation and qualify DYR684 as a useful chemical probe for DYRK1A and DYRK1B.
Pharmacogenomics in Alzheimer's disease.
Pharmacological treatment in Alzheimer's disease (AD) accounts for 10-20% of direct costs, and fewer than 20% of AD patients are moderate responders to conventional drugs (donepezil, rivastigmine, galantamine, memantine), with doubtful cost-effectiveness. Both AD pathogenesis and drug metabolism are genetically regulated complex traits in which hundreds of genes cooperatively participate. Structural genomics studies demonstrated that more than 200 genes might be involved in AD pathogenesis regulating dysfunctional genetic networks leading to premature neuronal death. The AD population exhibits a higher genetic variation rate than the control population, with absolute and relative genetic variations of 40-60% and 0.85-1.89%, respectively. AD patients also differ in their genomic architecture from patients with other forms of dementia. Functional genomics studies in AD revealed that age of onset, brain atrophy, cerebrovascular hemodynamics, brain bioelectrical activity, cognitive decline, apoptosis, immune function, lipid metabolism dyshomeostasis, and amyloid deposition are associated with AD-related genes. Pioneering pharmacogenomics studies also demonstrated that the therapeutic response in AD is genotype-specific, with apolipoprotein E (APOE) 4/4 carriers the worst responders to conventional treatments. About 10-20% of Caucasians are carriers of defective cytochrome P450 (CYP) 2D6 polymorphic variants that alter the metabolism and effects of AD drugs and many psychotropic a
Amyloid beta-peptide (1-42)-induced oxidative stress and neurotoxicity: implications for neurodegeneration in Alzheimer's disease brain. A review.
Oxidative stress, manifested by protein oxidation, lipid peroxidation, DNA oxidation and 3-nitrotyrosine formation, among other indices, is observed in Alzheimer's disease (AD) brain. Amyloid beta-peptide (1-42) [Abeta(1-42)] may be central to the pathogenesis of AD. Our laboratory and others have implicated Abeta(1-42)-induced free radical oxidative stress in the neurodegeneration observed in AD brain. This paper reviews some of these studies from our laboratory. Recently, we showed both in-vitro and in-vivo that methionine residue 35 (Met-35) of Abeta(1-42) was critical to its oxidative stress and neurotoxic properties. Because the C-terminal region of Abeta(1-42) is helical, and invoking the i + 4 rule of helices, we hypothesized that the carboxyl oxygen of lle-31, known to be within a van der Waals distance of the S atom of Met-35, would interact with the latter. This interaction could alter the susceptibility for oxidation of Met-35, i.e. free radical formation. Consistent with this hypothesis, substitution of lle-31 by the helix-breaking amino acid, proline, completely abrogated the oxidative stress and neurotoxic properties of Abeta(1-42). Removal of the Met-35 residue from the lipid bilayer by substitution of the negatively charged Asp for Gly-37 abrogated oxidative stress and neurotoxic properties of Abeta(1-42). The free radical scavenger vitamin E prevented A(beta (1-42)-induced ROS formation, protein oxidation, lipid peroxidation, and neurotoxicity in hippocampal
Proteolysis-Targeting Chimera (PROTAC) Delivery into the Brain across the Blood-Brain Barrier.
Drug development for neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease has challenging difficulties due to the pharmacokinetic impermeability based on the blood-brain barrier (BBB) as well as the blurriness of pharmacodynamic targets based on their unclarified pathogenesis and complicated progression mechanisms. Thus, in order to produce innovative central nervous system (CNS) agents for patients suffering from CNS diseases, effective, selective delivery of CNS agents into the brain across the BBB should be developed. Currently, proteolysis-targeting chimeras (PROTACs) attract rising attention as a new modality to degrade arbitrary intracellular proteins by the ubiquitin-proteasome system. The internalizations of peptide-based PROTACs by cell-penetrating peptides and that of small molecule-based PROTACs through passive diffusion lack cell selectivity. Therefore, these approaches may bring off-target side effects due to wrong distribution. Furthermore, efflux transporters such as multiple drug resistance 1 (MDR1) expressed at the BBB might interrupt the entry of small molecule-based PROTACs into the brain. Nonetheless, intelligent delivery using machinery systems to absorb the nutrition into the brain for homeostasis, such as carrier-mediated transport (CMT) or receptor-mediated transcytosis (RMT), can be established. PROTACs with N-containing groups that are recognized by the proton-coupled organic cation antiporter might cr
Blood-brain barrier permeability increases with the differentiation of glioblastoma cells in vitro.
BACKGROUND: Glioblastoma multiforme (GBM) is an aggressive tumor, difficult to treat pharmacologically because of the blood-brain barrier (BBB), which is rich in ATP-binding cassette (ABC) transporters and tight junction (TJ) proteins. The BBB is disrupted within GBM bulk, but it is competent in brain-adjacent-to-tumor areas, where eventual GBM foci can trigger tumor relapse. How GBM cells influence the permeability of BBB is poorly investigated. METHODS: To clarify this point, we co-cultured human BBB models with 3 patient-derived GBM cells, after separating from each tumor the stem cell/neurosphere (SC/NS) and the differentiated/adherent cell (AC) components. Also, we set up cultures of BBB cells with the conditioned medium of NS or AC, enriched or depleted of IL-6. Extracellular cytokines were measured by protein arrays and ELISA. The intracellular signaling in BBB cells was measured by immunoblotting, in the presence of STAT3 pharmacological inhibitor or specific PROTAC. The competence of BBB was evaluated by permeability assays and TEER measurement. RESULTS: The presence of GBM cells or their conditioned medium increased the permeability to doxorubicin, mitoxantrone and dextran-70, decreased TEER, down-regulated ABC transporters and TJ proteins at the transcriptional level. These effects were higher with AC or their medium than with NS. The secretome analysis identified IL-6 as significantly more produced by AC than by NS. Notably, AC-conditioned medium treated with an I
Deubiquitinating enzymes at the crossroads of blood-brain barrier integrity and neurodegeneration: mechanistic insights, therapeutic targeting and future directions.
The ubiquitin-proteasome system (UPS) carries immense significance concerning cellular homeostasis that encompasses both ubiquitination and deubiquitination as key facets for maintaining protein stability. The deubiquitinating enzymes (DUBs) have emerged as critical regulators of proteostasis, neuroinflammation and blood-brain barrier (BBB) integrity by controlling the fate of crucial proteins associated with barrier architectures in CNS and neurodegenerative disorders (NDs) alike. However, a concrete understanding of their specific neurodevelopmental and neuroprotective functions is yet to be discerned. This article discusses the multifaceted roles of DUBs in the maintenance of BBB integrity, neuroprotection and various NDs and also underscores the therapeutic prospects targeting the same. While DUBs like USP7, USP9X, USP27X, UCHL1, etc. participate in neural stem cell maintenance and neurogenesis, including BBB function, USP13, USP14, USP25, BRCC3 and CYLD, among others, are associated with BBB dysfunction and NDs. The mechanistic underpinning concerning their hitherto unexplored mode of action, DUB-substrate interactions and specificity would facilitate developing the therapeutic agonists and small-molecule inhibitors to prevent or reverse neuroinflammation, BBB impairment and developmental disorders. Recent innovations concerning DUB-targeting chimaeras (DUBTACs) and proteolysis-targeting chimaeras (PROTACs) can be explored further for their plausible administration via n
Targeted protein degradation in CNS disorders: a promising route to novel therapeutics?
Targeted protein degradation (TPD) is a rapidly expanding field, with various PROTACs (proteolysis-targeting chimeras) in clinical trials and molecular glues such as immunomodulatory imide drugs (IMiDs) already well established in the treatment of certain blood cancers. Many current approaches are focused on oncology targets, leaving numerous potential applications underexplored. Targeting proteins for degradation offers a novel therapeutic route for targets whose inhibition remains challenging, such as protein aggregates in neurodegenerative diseases. This mini review focuses on the prospect of utilizing TPD for neurodegenerative disease targets, particularly PROTAC and molecular glue formats and opportunities for novel CNS E3 ligases. Some key challenges of utilizing such modalities including molecular design of degrader molecules, drug delivery and blood brain barrier penetrance will be discussed.
Zinc finger proteins (ZFPs) in health and disease.
Zinc finger proteins (ZFPs), a vast superfamily of sequence-specific DNA and RNA-binding proteins, serve as master regulators of gene expression and cellular homeostasis. While traditionally studied for their roles in development, ZFPs have emerged as critical effectors and therapeutic targets across a wide spectrum of human pathologies, including cancer, neurological disorders, and autoimmune diseases. This review systematically dissects the molecular mechanisms by which dysregulated ZFP activity drives disease pathogenesis, using ischemic stroke as a central exemplar to illustrate their multifaceted roles. We detail how specific ZFPs orchestrate key stroke risk factors such as hypertension, hyperglycemia, and atherosclerosis, subsequently govern post-ischemic injury cascades, including neuroinflammation, programmed cell death, and blood-brain barrier disruption. Addressing the long-standing challenge of ZFPs as "undruggable" targets, we critically evaluate cutting-edge therapeutic strategies poised to modulate their function with precision. These include small-molecule modulators, targeted protein degraders (PROTACs), zinc finger nuclease (ZFN)-based gene editing, and advanced nanocarrier delivery systems, complemented by high-throughput computational screening. By integrating deep mechanistic insights with novel translational approaches, this review establishes a pioneering pan-disease framework for targeting ZFP networks. We provide a structured roadmap for future researc
An association of CSF apolipoprotein E glycosylation and amyloid-beta 42 in individuals who carry the APOE4 allele.
Carrying the apolipoprotein E (ApoE) Ɛ4 allele is associated with an increased risk of cerebral amyloidosis and late-onset Alzheimer's disease, but the degree to which apoE glycosylation affects its development is not clear. In a previous pilot study, we identified distinct total and secondary isoform-specific cerebral spinal fluid (CSF) apoE glycosylation profiles, with the E4 isoform having the lowest glycosylation percentage (E2 > E3 > E4). In this work, we extend the analysis to a larger cohort of individuals (n = 106), utilizing matched plasma and CSF samples with clinical measures of AD biomarkers. The results confirm the isoform-specific glycosylation of apoE in CSF, resulting from secondary CSF apoE glycosylation patterns. CSF apoE glycosylation percentages positively correlated with CSF Aβ42 levels (r = 0.53, p < 0.0001). These correlations were not observed for plasma apoE glycosylation. CSF total and secondary apoE glycosylation percentages also correlated with the concentration of CSF small high-density lipoprotein particles (s-HDL-P), which we have previously shown to be correlated with CSF Aβ42 levels and measures of cognitive function. Desialylation of apoE purified from CSF showed reduced Aβ42 degradation in microglia with E4 > E3 and increased binding affinity to heparin. These results indicate that apoE glycosylation has a new and important role in influencing brain Aβ metabolism and can be a potential target of treatment.
A novel small-molecule PROTAC selectively promotes tau clearance to improve cognitive functions in Alzheimer-like models.
Intracellular accumulation of tau is a hallmark pathology in Alzheimer disease (AD) and the related tauopathies, thus targeting tau could be promising for drug development. Proteolysis Targeting Chimera (PROTAC) is a novel drug discovery strategy for selective protein degradation from within cells. Methods: A novel small-molecule PROTAC, named as C004019 with a molecular mass of 1,035.29 dalton, was designed to simultaneously recruite tau and E3-ligase (Vhl) and thus to selectively enhance ubiquitination and proteolysis of tau proteins. Western blotting, immunofluoresence and immunohistochemical staining were employed to verify the effects of C004019 in cell models (HEK293 and SH-SY5Y) and mouse models (hTau-transgenic and 3xTg-AD), respectively. The cognitive capacity of the mice was assessed by a suite of behavior experiments. Electrophysiology and Golgi staining were used to evaluate the synaptic plasticity. Results: C004019 induced a robust tau clearance via promoting its ubiquitination-proteasome-dependent proteolysis in HEK293 cells with stable or transient overexpression of human tau (hTau), and in SH-SY5Y that constitutively overexpress hTau. Furthermore, intracerebral ventricular infusion of C004019 induced a robust tau clearance in vivo. Most importantly, both single-dose and multiple-doses (once per 6 days for a total 5 times) subcutaneous administration of C004019 remarkably decreased tau levels in the brains of wild-type, hTau-transgenic and 3xTg-AD mice with imp
Tethering ATG16L1 or LC3 induces targeted autophagic degradation of protein aggregates and mitochondria.
Proteolysis-targeting chimeras (PROTACs) based on the ubiquitin-proteasome system have made great progress in the field of drug discovery. There is mounting evidence that the accumulation of aggregation-prone proteins or malfunctioning organelles is associated with the occurrence of various age-related neurodegenerative disorders and cancers. However, PROTACs are inefficient for the degradation of such large targets due to the narrow entrance channel of the proteasome. Macroautophagy (hereafter referred to as autophagy) is known as a self-degradative process involved in the degradation of bulk cytoplasmic components or specific cargoes that are sequestered into autophagosomes. In the present study, we report the development of a generalizable strategy for the targeted degradation of large targets. Our results suggested that tethering large target models to phagophore-associated ATG16L1 or LC3 induced targeted autophagic degradation of the large target models. Furthermore, we successfully applied this autophagy-targeting degradation strategy to the targeted degradation of HTT65Q aggregates and mitochondria. Specifically, chimeras consisting of polyQ-binding peptide 1 (QBP) and ATG16L1-binding peptide (ABP) or LC3-interacting region (LIR) induced targeted autophagic degradation of pathogenic HTT65Q aggregates; and the chimeras consisting of mitochondria-targeting sequence (MTS) and ABP or LIR promoted targeted autophagic degradation of dysfunctional mitochondria, hence ameliora
Degradation of neurodegenerative disease-associated TDP-43 aggregates and oligomers via a proteolysis-targeting chimera.
BACKGROUND: Amyotrophic lateral sclerosis (ALS) associated with TAR DNA-binding protein 43 (TDP-43) aggregation has been considered as a lethal and progressive motor neuron disease. Recent studies have shown that both C-terminal TDP-43 (C-TDP-43) aggregates and oligomers were neurotoxic and pathologic agents in ALS and frontotemporal lobar degeneration (FTLD). However, misfolding protein has long been considered as an undruggable target by applying conventional inhibitors, agonists, or antagonists. To provide this unmet medical need, we aim to degrade these misfolding proteins by designing a series of proteolysis targeting chimeras (PROTACs) against C-TDP-43. METHODS: By applying filter trap assay, western blotting, and microscopy imaging, the degradation efficiency of C-TDP-43 aggregates was studied in Neuro-2a cells overexpressing eGFP-C-TDP-43 or mCherry-C-TDP-43. The cell viability was characterized by alarmarBlue assay. The beneficial and disaggregating effects of TDP-43 PROTAC were examined with the YFP-C-TDP-43 transgenic C. elegans by motility assay and confocal microscopy. The impact of TDP-43 PROTAC on C-TDP-43 oligomeric intermediates was monitored by fluorescence lifetime imaging microscopy and size exclusion chromatography in the Neuro-2a cells co-expressing eGFP-C-TDP-43 and mCherry-C-TDP-43. RESULTS: Four PROTACs with different linker lengths were synthesized and characterized. Among these chimeras, PROTAC 2 decreased C-TDP-43 aggregates and relieved C-TDP-43-i
Targeted degradation of ⍺-synuclein aggregates in Parkinson's disease using the AUTOTAC technology.
BACKGROUND: There are currently no disease-modifying therapeutics for Parkinson's disease (PD). Although extensive efforts were undertaken to develop therapeutic approaches to delay the symptoms of PD, untreated α-synuclein (α-syn) aggregates cause cellular toxicity and stimulate further disease progression. PROTAC (Proteolysis-Targeting Chimera) has drawn attention as a therapeutic modality to target α-syn. However, no PROTACs have yet shown to selectively degrade α-syn aggregates mainly owing to the limited capacity of the proteasome to degrade aggregates, necessitating the development of novel approaches to fundamentally eliminate α-syn aggregates. METHODS: We employed AUTOTAC (Autophagy-Targeting Chimera), a macroautophagy-based targeted protein degradation (TPD) platform developed in our earlier studies. A series of AUTOTAC chemicals was synthesized as chimeras that bind both α-syn aggregates and p62/SQSTM1/Sequestosome-1, an autophagic receptor. The efficacy of Autotacs was evaluated to target α-syn aggregates to phagophores and subsequently lysosomes for hydrolysis via p62-dependent macroautophagy. The target engagement was monitored by oligomerization and localization of p62 and autophagic markers. The therapeutic efficacy to rescue PD symptoms was characterized in cultured cells and mice. The PK/PD (pharmacokinetics/pharmacodynamics) profiles were investigated to develop an oral drug for PD. RESULTS: ATC161 induced selective degradation of α-syn aggregates at DC50 of
Epigenetic Dysregulation in Neurodegeneration: The Role of Histone Deacetylases and Emerging Inhibitor Strategies.
Neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD) are characterized by complex pathologies with progressive neurodegeneration, protein misfolding, oxidative stress, and persistent inflammation. Recent findings indicate the pivotal involvement of epigenetic disruption, particularly aberrant histone deacetylase (HDAC) activity, in disease initiation and progression. In the current review, we systematically discuss the mechanistic function of HDACs across all classes (I, IIa, IIb, III, and IV) in neurodegenerative disease mechanisms, such as their involvement in the modulation of gene expression, mitochondrial function, proteostasis, and neuronal survival. We discuss the therapeutic potential, as well as limitations, of HDAC inhibitors (HDACis), such as pan-inhibitors and isoenzyme-selective inhibitors, and new multi-target-directed ligands with HDAC inhibition combined with acetylcholinesterase modulation, PDE modulation, MAO-B inhibition, or NMDAR modulation. Particular emphasis is placed on the development of HDAC6-selective inhibitors with enhanced brain permeability and reduced toxicity, which have shown promising preclinical efficacy in ameliorating hallmark pathologies of AD, PD, and HD. In addition, s-triazine-based scaffolds have recently emerged as promising chemotypes in HDAC inhibitor design, offering favorable pharmacokinetic profiles, metabolic stability, and the potential for dual-target modulation
Taming hyper-active Cdk5: Disrupting the Cdk5-p25 axis as a therapeutic avenue for neurodegeneration and beyond.
Cyclin-dependent kinase 5 (Cdk5) is essential for neuronal development and synaptic function when activated by its physiological cofactors p35 and p39. Pathological calpain cleavage of p35 generates the more stable fragment p25, producing a hyperactive, mislocalized kinase complex that has been implicated in tau hyperphosphorylation, DNA damage, neuroinflammation, and aberrant neuronal cell-cycle re-entry. Three decades of work position the Cdk5-p25 axis as a convergent pathogenic mechanism in Alzheimer's disease and related dementias, Parkinson's disease, traumatic brain injury, and in subsets of metabolic and solid-tumor contexts. High-resolution structures of Cdk5-p25 reveal a distinctive activation-loop "cradle" and a tract leading toward catalytic Lys33 that enable structure-guided inhibitor design. Recent advances include (i) small molecules that "vector" toward Lys33 and achieve ∼70-125 × selectivity over closely related CDKs in biochemical assays, (ii) brain-penetrant peptide disruptors that preferentially inhibit Cdk5-p25 while sparing basal Cdk5-p35 signaling in rodent models, and (iii) early-stage degradation or genetic approaches (e.g., dual-target PROTACs; calpain-resistant p35 or Cdk5 knockdown) that reduce p25 signaling or Cdk5 levels in cells. Across inducible mouse models, toxin paradigms, and tumor xenografts, interventions that blunt the p25-driven switch ameliorate cognitive deficits, preserve dopaminergic neurons, improve insulin secretion in β-cell model
Apolipoprotein E and Alzheimer disease: pathobiology and targeting strategies.
Polymorphism in the apolipoprotein E (APOE) gene is a major genetic risk determinant of late-onset Alzheimer disease (AD), with the APOE*ε4 allele conferring an increased risk and the APOE*ε2 allele conferring a decreased risk relative to the common APOE*ε3 allele. Strong evidence from clinical and basic research suggests that a major pathway by which APOE4 increases the risk of AD is by driving earlier and more abundant amyloid pathology in the brains of APOE*ε4 carriers. The number of amyloid-β (Aβ)-dependent and Aβ-independent pathways that are known to be differentially modulated by APOE isoforms is increasing. For example, evidence is accumulating that APOE influences tau pathology, tau-mediated neurodegeneration and microglial responses to AD-related pathologies. In addition, APOE4 is either pathogenic or shows reduced efficiency in multiple brain homeostatic pathways, including lipid transport, synaptic integrity and plasticity, glucose metabolism and cerebrovascular function. Here, we review the recent progress in clinical and basic research into the role of APOE in AD pathogenesis. We also discuss how APOE can be targeted for AD therapy using a precision medicine approach.
The cell biology of APOE in the brain.
Apolipoprotein E (APOE) traffics lipids in the central nervous system. The E4 variant of APOE is a major genetic risk factor for Alzheimer's disease (AD) and a multitude of other neurodegenerative diseases, yet the molecular mechanisms by which APOE4 drives disease are still unclear. A growing collection of studies in iPSC models, knock-in mice, and human postmortem brain tissue have demonstrated that APOE4 expression in astrocytes and microglia is associated with the accumulation of cytoplasmic lipid droplets, defects in endolysosomal trafficking, impaired mitochondrial metabolism, upregulation of innate immune pathways, and a transition into a reactive state. In this review, we collate these developments and suggest testable mechanistic hypotheses that could explain common APOE4 phenotypes.
Cognitive Decline and Neurodegenerative Markers in Psoriasis: The Role of APOE4 and Beta-Amyloid.
INTRODUCTION: Psoriasis vulgaris (PV) is a chronic inflammatory skin disease increasingly recognized as a systemic disorder with potential cognitive implications. Amyloid beta (Aβ) and apolipoprotein E (APOE) are key proteins involved in Alzheimer's disease (AD) and neurodegeneration. OBJECTIVES: This study investigated the relationship between PV, cognitive function, and serum levels of Aβ and APOE4. METHODS: This case-control study was conducted on 80 participants: 50 PV patients and 30 age- and sex-matched controls. Clinical assessments included Psoriasis Area and Severity Index (PASI). Depression severity was assessed with Beck Depression Inventory-II (BDI-II), while cognitive function was evaluated using Montreal Cognitive Assessment (MoCA). Serum APOE4 and Aβ levels were measured using ELISA. RESULTS: Patients with PV exhibited significantly higher levels of APOE4 (1125.5 ± 232.1 ng/ml vs. 821.8 ± 266 ng/ml, P<0.001) and Aβ (21.4 ± 2.2 ng/ml vs. 18.7 ± 1.4 ng/ml, P<0.001) compared to controls. ROC analysis identified APOE4 (AUC=0.80, P<0.001) and Aβ (AUC=0.86, P<0.001) as significant predictors of PV. MoCA scores were significantly lower in PV patients (median=22 vs. 28, P<0.001), particularly in those with severe disease. APOE4 and Aβ levels negatively correlated with cognitive function (r= -0.418, P=0.003), and (r= -0.399, P=0.004) respectively. CONCLUSIONS: PV is associated with elevated Aβ and APOE4 levels, potentially linking chronic inflammation to neurodegenerati
Plasma GFAP outperforms CSF GFAP in detecting amyloid pathology and is associated with increased risk of clinical progression in early Alzheimer's disease.
BACKGROUND: Early and accurate detection of Alzheimer's disease (AD) is essential for timely intervention and development of disease-modifying treatments. The DZNE-Longitudinal Cognitive Impairment and Dementia Study (DELCODE) provides a deeply phenotyped cohort covering preclinical and early clinical stages, including subjective cognitive decline (SCD) and mild cognitive impairment (MCI). Astrocyte reactivity and its biomarkers, particularly glial fibrillary acidic protein (GFAP), have gained increasing attention in AD research; however, the relationship between GFAP and amyloid in early disease, as well as its potential prognostic value beyond its association with amyloid status, remains insufficiently understood. OBJECTIVES: To evaluate the performance of CSF and plasma GFAP across early disease stages, compare these measures according to amyloid status, and assess the prognostic value of GFAP for clinical progression across diagnostic stages during longitudinal follow-up. SETTING: This study used data from the multicenter DELCODE cohort in Germany, including participants with available plasma and/or CSF samples and standardized clinical, cognitive, imaging, and biomarker assessments. MEASUREMENTS: GFAP concentrations in plasma and CSF were quantified using validated immunoassay platforms. Standard CSF AD biomarkers and ApoE genotype were measured using established assays. Amyloid status was defined by the CSF Aβ42/40 ratio. Longitudinal follow-up occurred annually for up
TRIM47 Promotes Atherosclerosis by Activating NF-κB Signaling via IκBα Ubiquitination.
Atherosclerosis, a major contributor to cardiovascular diseases, is characterized by chronic inflammation in arterial walls. The role of NF-κB signaling in this process is well-established, but the upstream regulators remain incompletely understood. This study explored the role of TRIM47, an E3 ubiquitin ligase, in promoting atherosclerosis through NF-κB activation. In vitro studies used human umbilical vein endothelial cells (EC) treated with oxidized low-density lipoprotein (ox-LDL). TRIM47 expression was modulated using siRNA knockdown and overexpression plasmids. Inflammation markers, cell viability, and NF-κB activation were assessed. In vivo studies utilized ApoE-/- mice fed a high-fat diet and treated with adenovirus-mediated TRIM47 knockdown. ox-LDL treatment increased TRIM47 expression in EC, alongside elevated inflammatory markers, and reduced cell viability. TRIM47 overexpression exacerbated ox-LDL-induced inflammation, while knockdown attenuated these effects. Mechanistically, TRIM47 directly interacted with IκBα, promoting its ubiquitination and degradation, leading to enhanced NF-κB activation. In ApoE-/- mice, TRIM47 knockdown significantly reduced atherosclerotic plaque formation and lesion size. This study identified TRIM47 as a novel regulator of atherosclerosis progression through IκBα ubiquitination and NF-κB activation. TRIM47 knockdown attenuated vascular inflammation and atherosclerotic plaque formation. The findings suggested that TRIM47 might be a pot
Alirocumab Attenuated Plaque Inflammation and PCSK9-Induced Proinflammatory Signalling in M1 Macrophages Independently of Lipid Lowering.
BACKGROUND: Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) has been implicated in vascular inflammation beyond its action on LDL-C degradation. We investigated whether PCSK9 may exacerbate proinflammatory signaling of M1 macrophages and if its neutralization with alirocumab could attenuate this effect and plaque progression by LDL-C independent mechanisms. METHODS: ApoE-/- mice were treated with alirocumab for 13 weeks, and aortic arches were isolated for atherosclerotic plaque characterization based on lesion size and lipid and macrophage infiltration. Plasma and splenic monocytes/macrophages were also assessed by flow cytometry, and PCSK9, the lipid profile, and inflammatory cytokines were measured by qPCR or Western blot. Cultured THP-1-derived M1 macrophages were stimulated with PCSK9 and evaluated for TLR4-NFκB-NLRP3 activation and cytokine production. In addition, soluble PCSK9, LDL-C, and proinflammatory factors were analyzed in 1190 patients with acute coronary syndrome (ACS). RESULTS: Alirocumab reduced plaque lesion (0.42-fold; p < 0.05) and lipid (0.63-fold; p < 0.01) and macrophage (0.61-fold; p < 0.05) infiltration, mainly the M1 subtype (0.37-fold; p < 0.01), as well as TLR4, NLRP3 and caspase-1 expressions (0.49-fold, 0.51-fold and 0.51-fold, respectively; p < 0.05), without altering LDL-C. Also, it decreased proinflammatory cytokines but enhanced anti-inflammatory factors and M2 markers at the descending aorta. Alirocumab enriched circulating Ly6Clow mo
Sex-specific APOE4-dependent innate immunity regulates meningeal lymphatics, brain lipids, neuroinflammation, and cognition.
Sex and apolipoprotein E ε4 (APOE4) interact to alter the risk for Alzheimer's disease and other neurodegenerative disorders. Herein, we show sex-specific differences in immune activation and lymphatic function in the meningeal dura of humanized female and male mice expressing two alleles of APOE4 (E4/E4), when compared with their respective sex-matched E3/E3 controls. We also describe distinct effects of APOE4 on brain lipid composition and inflammation in females and males that were partially reverted upon colony-stimulating factor 1 receptor (CSF1R) inhibition. Suppressing innate immunity reduced neuroinflammation and restored cognitive function in E4/E4 females, while exacerbating neuroinflammation and accelerating cognitive decline in E4/E4 males. Finally, in line with the E4/E4 humanized mouse model data, we show that APOE4 expression is linked to sexually dimorphic leukocyte activation profiles in the human brain. This study highlights the need for personalized therapies when targeting APOE, brain immunity, and meningeal lymphatics to promote cognitive resilience in both females and males.
Explores the impact of APOE ε4 on tau biomarkers and cognitive decline, supporting the hypothesis that APOE4 plays a critical role in neurodegeneration.
BackgroundMild cognitive impairment (MCI) confers an increased risk of Alzheimer's disease (AD). The apolipoprotein E (APOE) ε4 allele is a major genetic risk factor for late-onset AD and is strongly associated with amyloid-β (Aβ) pathology. However, whether Aβ burden is associated with APOE ε4-related longitudinal changes in tau pathology, neurodegeneration, and cognitive decline in MCI remains incompletely understood.ObjectiveTo examine whether Aβ burden is associated with APOE ε4-related long
Demonstrates that alternative APOE expressions can ameliorate amyloid-β pathology, indirectly supporting the potential benefits of APOE4 modulation.
The rare APOE3-Christchurch (APOE3Ch) variant is linked to resistance against PSEN1 p.E280A-driven autosomal dominant Alzheimer's disease (AD). Recent studies in AD mouse models have demonstrated an effect of APOE3Ch in reducing tau pathology and tau propagation, yet its effects on amyloid pathology and related toxicity are not fully understood. While prior studies have reported reduced amyloid pathology with APOE3Ch, we extended this knowledge by investigating how astrocyte-specific expression
Targeting KAT8 alleviates vascular senescence by modulating the INHBA/TGF-β pathway.
Adipose Tissue Macrophage-Derived Proplatelet Basic Protein Exacerbates Psoriasis-Associated Atherosclerosis by Inducing Mitochondrial Dysfunction in Aortic Endothelial Cells.
Neuropsychiatric symptoms and apolipoprotein E genotypes in neurocognitive disorders.
Restoration of p53 mRNA combined with BRD4 silencing by brain targeted nanocapsules achieves effective combinatorial treatment of glioblastoma.
Integrative machine learning approach to risk prediction for dementia and Alzheimer's disease.
Perioperative polygenic and APOE-based genetic risk assessment for neurocognitive disorders: a biobank study.
Increased genetic protection against Alzheimer's disease in centenarians.
Menopause, cognition, and Alzheimer's disease risk.
UBE2I Alleviates Pyroptosis in Coronary Heart Disease by Promoting the SUMOylation and Degradation of NLRP3.
Inflammation-related miR-155-5p as an APOE ε4-modulated biomarker for amyloid pathology in mild cognitive impairment.
Apolipoprotein E proteotyping as a valid alternative to genotyping in clinical practice.
Covalent Bond Locking in Semiconducting Oligomers Boosts Ultrabright NIR-II Luminescence for Deep Brain Theranostics.
Integrative multi-omics identifies a diagnostic T cell signature for cutaneous squamous cell carcinoma.
Chicoric acid enhanced brain cholesterol efflux and reduced Aβ pathology via LXR-ABCA1 signaling in Alzheimer's models.
Trajectories of frailty, grip strength and gait speed preceding dementia: a nested case-control study.
Opposing patterns of blood-brain barrier permeability and Alzheimer's disease biomarkers across APOE genotype.
Associations between air pollution and markers of neuroinflammation, synaptic dysfunction and core Alzheimer's disease pathology vary by APOE genotype.
Amyloid-related imaging abnormalities in Japanese patients with Alzheimer's disease treated with Lecanemab: A real-world study.
Brain DHA increases in APOE3, but not in APOE4 mice, despite robust brain EPA increase during LPC n-3 supplementation in both genotypes.
Early intervention with tirzepatide or semaglutide influences anti-atherosclerotic effects in ApoE knockout mice.
Prognosis in Parkinson's Disease: An Individual Patient Data Meta-Analysis of Six European Incidence Cohorts.
Albofungin vesicle nanobombs trigger lysosomal disruption for self-enhanced pyroptosis and cGAS-STING pathway activation in glioblastoma immunotherapy.
Plant-Based Dietary Patterns and Risk of Alzheimer Disease and Related Dementias in the Multiethnic Cohort Study.
ApoE-directed CpG nano-immunoadjuvant ameliorates Alzheimer's-like pathology in mice.
Structural MRI phenotyping in Alzheimer's disease: Comparison of visual rating scales, volumetry, and cortical thickness in a Serbian single-centre cohort.
Evidence against (20)
APOE and Alzheimer's disease: advances in genetics, pathophysiology, and therapeutic approaches.
The APOE ε4 allele remains the strongest genetic risk factor for sporadic Alzheimer's disease and the APOE ε2 allele the strongest genetic protective factor after multiple large scale genome-wide association studies and genome-wide association meta-analyses. However, no therapies directed at APOE are currently available. Although initial studies causally linked APOE with amyloid-β peptide aggregation and clearance, over the past 5 years our understanding of APOE pathogenesis has expanded beyond amyloid-β peptide-centric mechanisms to tau neurofibrillary degeneration, microglia and astrocyte responses, and blood-brain barrier disruption. Because all these pathological processes can potentially contribute to cognitive impairment, it is important to use this new knowledge to develop therapies directed at APOE. Several therapeutic approaches have been successful in mouse models expressing human APOE alleles, including increasing or reducing APOE levels, enhancing its lipidation, blocking the interactions between APOE and amyloid-β peptide, and genetically switching APOE4 to APOE3 or APOE2 isoforms, but translation to human clinical trials has proven challenging.
Alzheimer Disease: An Update on Pathobiology and Treatment Strategies.
Alzheimer disease (AD) is a heterogeneous disease with a complex pathobiology. The presence of extracellular β-amyloid deposition as neuritic plaques and intracellular accumulation of hyperphosphorylated tau as neurofibrillary tangles remains the primary neuropathologic criteria for AD diagnosis. However, a number of recent fundamental discoveries highlight important pathological roles for other critical cellular and molecular processes. Despite this, no disease-modifying treatment currently exists, and numerous phase 3 clinical trials have failed to demonstrate benefits. Here, we review recent advances in our understanding of AD pathobiology and discuss current treatment strategies, highlighting recent clinical trials and opportunities for developing future disease-modifying therapies.
Apolipoprotein E controls Dectin-1-dependent development of monocyte-derived alveolar macrophages upon pulmonary β-glucan-induced inflammatory adaptation
The lung is constantly exposed to the outside world and optimal adaptation of immune responses is crucial for efficient pathogen clearance. However, mechanisms that lead to lung-associated macrophages' functional and developmental adaptation remain elusive. To reveal such mechanisms, we developed a reductionist model of environmental intranasal β-glucan exposure, allowing for the detailed interrogation of molecular mechanisms of pulmonary macrophage adaptation. Employing single-cell transcriptomics, high-dimensional imaging and flow cytometric characterization paired with in vivo and ex vivo challenge models, we reveal that pulmonary low-grade inflammation results in the development of apolipoprotein E (ApoE)-dependent monocyte-derived alveolar macrophages (ApoE+CD11b+ AMs). ApoE+CD11b+ AMs expressed high levels of CD11b, ApoE, Gpnmb and Ccl6, were glycolytic, highly phagocytic and produced large amounts of interleukin-6 upon restimulation. Functional differences were cell intrinsic, and myeloid cell-specific ApoE ablation inhibited Ly6c+ monocyte to ApoE+CD11b+ AM differentiation dependent on macrophage colony-stimulating factor secretion, promoting ApoE+CD11b+ AM cell death and thus impeding ApoE+CD11b+ AM maintenance. In vivo, β-glucan-elicited ApoE+CD11b+ AMs limited the bacterial burden of Legionella pneumophilia after infection and improved the disease outcome in vivo and ex vivo in a murine lung fibrosis model. Collectively these data identify ApoE+CD11b+ AMs generated
PROTAC 2.0: Expanding the frontiers of targeted protein degradation.
Proteolysis targeting chimera (PROTAC) technology has revolutionized targeted protein degradation via the ubiquitin-proteasome system. Despite their efficacy in degrading previously undruggable proteins, classical PROTACs face challenges such as poor permeability, dose-dependent effects, and off-target toxicity, prompting the rise of next-generation PROTACs (PROTAC 2.0). This review explores emerging PROTAC-based strategies aimed at enhancing selectivity, bioavailability, and pharmacokinetics. We discuss innovative approaches such as photoactivable PROTACs, hypoxia-responsive degraders, dual and trivalent PROTACs, and antibody-conjugated degraders. Additionally, nanotechnology-based delivery systems are highlighted as promising tools to overcome membrane permeability issues. By analyzing these novel strategies, we highlight the evolution of PROTACs and their growing therapeutic potential. Advances in PROTAC 2.0 technologies are expected to expand their clinical applications, offering more selective and efficient degradation mechanisms.
Liver-targeted degradation of BRD4 reverses hepatic fibrosis and enhances metabolism in murine models.
Background: Liver fibrosis, characterized by excessive extracellular matrix deposition, is a precursor to cirrhosis and hepatocellular carcinoma, and current treatments are often limited by off-target toxicities. Methods and results: We repurposed the liver-targeting chimera (LIVTAC) XZ1606, a novel proteolysis-targeting chimera (PROTAC) conjugated with a triantennary N-acetylgalactosamine (tri-GalNAc) moiety, to degrade BRD4 in hepatic stellate cells. In vitro, XZ1606 induced potent, dose- and time-dependent BRD4 degradation in LX-2 cells via the ubiquitin-proteasomal pathway after ASGPR-mediated endocytosis, with minimal cytotoxicity in normal hepatocytes. TGF-β-activated LX-2 cells exhibited significant reductions in fibrotic markers upon treatment, correlating with decreased BRD4 levels. In vivo, XZ1606 (1.5 mg/kg) significantly ameliorated fibrosis in both CCl₄-induced and choline-deficient L-amino acid-defined high-fat diet (CDAA-HFD) mouse models, as evidenced by reduced collagen deposition and normalized transcriptomic and metabolomic profiles. Notably, key proinflammatory and profibrotic genes and metabolites, including 1-Methylnicotinamide, were downregulated. Conclusion: These results highlight the therapeutic potential of LIVTAC XZ1606 in reversing liver fibrosis and steatosis through targeted BRD4 degradation, offering a novel and selective approach for chronic liver disease treatment.
Near-Infrared-Activatable PROTAC Nanocages for Controllable Target Protein Degradation and On-Demand Antitumor Therapy.
As a novel protein knockdown tool, proteolysis targeting chimeras (PROTACs) can induce potent degradation of target proteins by hijacking E3 ubiquitin ligases. However, the uncontrollable protein disruption of PROTACs is prone to cause "off-target" toxicity after systemic administration. Herein, we designed a photocaged-PROTAC (phoBET1) and loaded it in UCNPs-based mesoporous silica nanoparticles (UMSNs) to construct a NIR light-activatable PROTAC nanocage (UMSNs@phoBET1) for controllable target protein degradation. Upon NIR light (980 nm) irradiation, UMSNs@phoBET1 nanocages could be activated to release active PROTAC via a controlled pattern for degrading bromodomain-containing protein 4 (BRD4) and inducing MV-4-11 cancer cell apoptosis. In vivo experiments demonstrated that UMSNs@phoBET1 nanocages were capable of responding to NIR light in tumor tissues to achieve BRD4 degradation and effectively suppress tumor growth. This NIR light-activatable PROTAC nanoplatform compensates for the current shortcomings of short-wavelength light-controlled PROTACs and presents a paradigm for the precise regulation of PROTACs in living tissues.
Session 5: Protein Degraders.
The so-called undruggable space is an exciting area of potential growth for drug development. Undruggable proteins are defined as those unable to be targeted via conventional small molecule drugs. New modalities are being developed to potentially target these proteins. Targeted protein degradation (TPD) is one such new modality, which over the last two decades has moved from academia to industry. TPD makes use of the endogenous degradation machinery present in all cells, in which E3 ubiquitin ligases mark proteins for degradation via ubiquitin attachment. This session explored the challenges and perspectives of using protein degraders as novel therapeutic agents. The session began with a general introduction to the modality, followed by considerations in evaluating their on- and off-target toxicities including data from an IQ Consortium working group survey. Unique absorption, distribution, metabolism, and excretion (ADME) properties of degrader molecules were presented in relation to their effect on drug development and nonclinical safety assessment. The role of transgenic models in evaluating hemotoxicity associated with cereblon-based therapies was then discussed. A case study to derisk dose-limiting thrombocytopenia was also presented. Finally, a regulatory perspective on the challenges of having toxicity associated with protein degraders was presented.
Neuronal ROS-induced glial lipid droplet formation is altered by loss of Alzheimer's disease-associated genes.
A growing list of Alzheimer's disease (AD) genetic risk factors is being identified, but the contribution of each variant to disease mechanism remains largely unknown. We have previously shown that elevated levels of reactive oxygen species (ROS) induces lipid synthesis in neurons leading to the sequestration of peroxidated lipids in glial lipid droplets (LD), delaying neurotoxicity. This neuron-to-glia lipid transport is APOD/E-dependent. To identify proteins that modulate these neuroprotective effects, we tested the role of AD risk genes in ROS-induced LD formation and demonstrate that several genes impact neuroprotective LD formation, including homologs of human ABCA1, ABCA7, VLDLR, VPS26, VPS35, AP2A, PICALM, and CD2AP Our data also show that ROS enhances Aβ42 phenotypes in flies and mice. Finally, a peptide agonist of ABCA1 restores glial LD formation in a humanized APOE4 fly model, highlighting a potentially therapeutic avenue to prevent ROS-induced neurotoxicity. This study places many AD genetic risk factors in a ROS-induced neuron-to-glia lipid transfer pathway with a critical role in protecting against neurotoxicity.
From Genetics to Neuroinflammation: The Impact of ApoE4 on Microglial Function in Alzheimer's Disease.
Alzheimer's disease (AD) is a debilitating neurodegenerative disorder marked by progressive cognitive decline and memory loss, impacting millions of people around the world. The apolipoprotein E4 (ApoE4) allele is the most prominent genetic risk factor for late-onset AD, dramatically increasing disease susceptibility and accelerating onset compared to its isoforms ApoE2 and ApoE3. ApoE4's unique structure, which arises from single-amino-acid changes, profoundly alters its function. This review examines the critical interplay between ApoE4 and microglia-the brain's resident immune cells-and how this relationship contributes to AD pathology. We explore the molecular mechanisms by which ApoE4 modulates microglial activity, promoting a pro-inflammatory state, impairing phagocytic function, and disrupting lipid metabolism. These changes diminish microglia's ability to clear amyloid-beta peptides, exacerbating neuroinflammation and leading to neuronal damage and synaptic dysfunction. Additionally, ApoE4 adversely affects other glial cells, such as astrocytes and oligodendrocytes, further compromising neuronal support and myelination. Understanding the ApoE4-microglia axis provides valuable insights into AD progression and reveals potential therapeutic targets. We discuss current strategies to modulate ApoE4 function using small molecules, antisense oligonucleotides, and gene editing technologies. Immunotherapies targeting amyloid-beta and ApoE4, along with neuroprotective approache
Loss of Lipid Carrier ApoE Exacerbates Brain Glial and Inflammatory Responses after Lysosomal GBA1 Inhibition.
Tightly regulated and highly adaptive lipid metabolic and transport pathways are critical to maintaining brain cellular lipid homeostasis and responding to lipid and inflammatory stress to preserve brain function and health. Deficits in the lipid handling genes APOE and GBA1 are the most significant genetic risk factors for Lewy body dementia and related dementia syndromes. Parkinson's disease patients who carry both APOE4 and GBA1 variants have accelerated cognitive decline compared to single variant carriers. To investigate functional interactions between brain ApoE and GBA1, in vivo GBA1 inhibition was tested in WT versus ApoE-deficient mice. The experiments demonstrated glycolipid stress caused by GBA1 inhibition in WT mice induced ApoE expression in several brain regions associated with movement and dementia disorders. The absence of ApoE in ApoE-KO mice amplified complement C1q elevations, reactive microgliosis and astrocytosis after glycolipid stress. Mechanistically, GBA1 inhibition triggered increases in cell surface and intracellular lipid transporters ABCA1 and NPC1, respectively. Interestingly, the absence of NPC1 in mice also triggered elevations of brain ApoE levels. These new data show that brain ApoE, GBA1 and NPC1 functions are interconnected in vivo, and that the removal or reduction of ApoE would likely be detrimental to brain function. These results provide important insights into brain ApoE adaptive responses to increased lipid loads.
Characterizing molecular and synaptic signatures in mouse models of late-onset Alzheimer's disease independent of amyloid and tau pathology.
INTRODUCTION: MODEL-AD (Model Organism Development and Evaluation for Late-Onset Alzheimer's Disease) is creating and distributing novel mouse models with humanized, clinically relevant genetic risk factors to capture the trajectory and progression of late-onset Alzheimer's disease (LOAD) more accurately. METHODS: We created the LOAD2 model by combining apolipoprotein E4 (APOE4), Trem2*R47H, and humanized amyloid-beta (Aβ). Mice were subjected to a control diet or a high-fat/high-sugar diet (LOAD2+HFD). We assessed disease-relevant outcome measures in plasma and brain including neuroinflammation, Aβ, neurodegeneration, neuroimaging, and multi-omics. RESULTS: By 18 months, LOAD2+HFD mice exhibited sex-specific neuron loss, elevated insoluble brain Aβ42, increased plasma neurofilament light chain (NfL), and altered gene/protein expression related to lipid metabolism and synaptic function. Imaging showed reductions in brain volume and neurovascular uncoupling. Deficits in acquiring touchscreen-based cognitive tasks were observed. DISCUSSION: The comprehensive characterization of LOAD2+HFD mice reveals that this model is important for preclinical studies seeking to understand disease trajectory and progression of LOAD prior to or independent of amyloid plaques and tau tangles. HIGHLIGHTS: By 18 months, unlike control mice (e.g., LOAD2 mice fed a control diet, CD), LOAD2+HFD mice presented subtle but significant loss of neurons in the cortex, elevated levels of insoluble Ab42 in t
A Dual-Target and Dual-Mechanism Design Strategy by Combining Inhibition and Degradation Together.
Glioblastoma, a highly aggressive brain tumor, lacks effective treatment with low 5 year survival rates. Urgency for new therapies is evident. Mammalian targets of rapamycin (mTOR) and G1 to S phase transition 1 gene (GSPT1) are overexpressed in glioblastoma, regulating vital cellular functions. Current mTOR inhibitors face challenges in clinical efficacy and drug resistance. Similarly, GSPT1-targeting therapies have not progressed of glioblastoma in clinical trials. Research studies suggested that combining mTOR inhibition with GSPT1 degradation may overcome resistance and enhance efficacy. We propose the concept of jointly implementing inhibition and degradation on different proteins, integrating the properties of inhibitors and degraders into the same molecule. Introducing YB-3-17, a novel bifunctional molecule, robustly inhibits mTOR and selectively degrades GSPT1. As a tool compound for proof-of-concept studies, YB-3-17 sharpens selectivity, avoiding off-target effects, and selectively induces GSPT1 degradation and mTOR inhibition, showing superior efficacy in tumor cell lines compared to that of standalone therapies. RNA-seq analysis highlights the advantages of YB-3-17 over mTOR inhibitor treatment. YB-3-17 can safely and effectively inhibit tumor growth in mice, offering a promising direction for precision treatment of glioblastoma, representing the first attempt to combine mTOR inhibition with GSPT1 degradation. This work also demonstrates that it is conceptually pos
Advancing brain tumor therapy: unveiling the potential of PROTACs for targeted protein degradation.
The long-term treatment of malignancies, particularly brain tumors, is challenged by abnormal protein expression and drug resistance. In terms of potency, selectivity, and overcoming drug resistance, Proteolysis Targeting Chimeras (PROTACs), a cutting-edge method used to selectively degrade target proteins, beats traditional inhibitors. This review summarizes recent research on using PROTACs as a therapeutic strategy for brain tumors, focusing on their mechanism, benefits, limitations, and the need for optimization. The review draws from a comprehensive search of peer-reviewed literature, scientific databases, and clinical trial databases. Articles published up to the knowledge cutoff date up to 14 April 2023 were included. Inclusion criteria covered PROTAC-based brain tumor therapies, including preclinical and early clinical studies, with no restrictions on design or publication type. We included studies using in vitro, in vivo brain tumor models, and human subjects. Eligible treatments involved PROTACs targeting proteins linked to brain tumor progression. We evaluated the selected studies for methodology, including design, sample size, and data analysis techniques. A narrative synthesis summarized key outcomes and trends in PROTAC-based brain tumor therapy. Recent research shows PROTACs selectively degrade brain tumor-related proteins with minimal off-target effects. They offer enhanced potency, selectivity, and the ability to combat resistance compared to traditional inhib
Covalent inhibitors in Parkinson's disease: Molecular targeting strategies for neuroprotective intervention.
Parkinson's disease (PD) is a complex neurodegenerative disorder characterized by dopaminergic neuronal loss, protein aggregation, and neuroinflammation. Current symptomatic therapies have not demonstrated disease-modifying effects. Covalent inhibitors represent a promising multifactorial therapeutic approach due to their ability to form irreversible and specific bonds with target proteins. This narrative review incorporates recent experimental and computational findings on emerging covalent inhibitors that target key molecular mechanisms implicated in PD. This includes α-synuclein aggregation, LRRK2 kinase hyperactivity, monoamine oxidase B (MAO-B) dysfunction, glutathione S-transferase Pi 1 (GSTP1)-mediated oxidative stress, and modulation of the Nrf2 signaling pathway. We discuss structure-guided drug design strategies, warhead chemistry, and unique inhibition modalities that contribute to improved pharmacological profiles and neuroprotective potential. In addition to classical covalent inhibition, the review explores emerging targeted covalent degrader strategies that expand therapeutic possibilities by promoting selective protein degradation rather than mere functional suppression. Furthermore, recent preclinical advances and clinical translation challenges are evaluated, positioning covalent approaches as leading candidates for targeted and sustained PD interventions. Lastly, we address developmental obstacles, such as enhancing selectivity and blood-brain barrier penet
Updates in Alzheimer's disease: from basic research to diagnosis and therapies.
Alzheimer's disease (AD) is the most common neurodegenerative disorder, characterized pathologically by extracellular deposition of β-amyloid (Aβ) into senile plaques and intracellular accumulation of hyperphosphorylated tau (pTau) as neurofibrillary tangles. Clinically, AD patients show memory deterioration with varying cognitive dysfunctions. The exact molecular mechanisms underlying AD are still not fully understood, and there are no efficient drugs to stop or reverse the disease progression. In this review, we first provide an update on how the risk factors, including APOE variants, infections and inflammation, contribute to AD; how Aβ and tau become abnormally accumulated and how this accumulation plays a role in AD neurodegeneration. Then we summarize the commonly used experimental models, diagnostic and prediction strategies, and advances in periphery biomarkers from high-risk populations for AD. Finally, we introduce current status of development of disease-modifying drugs, including the newly officially approved Aβ vaccines, as well as novel and promising strategies to target the abnormal pTau. Together, this paper was aimed to update AD research progress from fundamental mechanisms to the clinical diagnosis and therapies.
Apolipoprotein E and Alzheimer disease: pathobiology and targeting strategies.
Polymorphism in the apolipoprotein E (APOE) gene is a major genetic risk determinant of late-onset Alzheimer disease (AD), with the APOE*ε4 allele conferring an increased risk and the APOE*ε2 allele conferring a decreased risk relative to the common APOE*ε3 allele. Strong evidence from clinical and basic research suggests that a major pathway by which APOE4 increases the risk of AD is by driving earlier and more abundant amyloid pathology in the brains of APOE*ε4 carriers. The number of amyloid-β (Aβ)-dependent and Aβ-independent pathways that are known to be differentially modulated by APOE isoforms is increasing. For example, evidence is accumulating that APOE influences tau pathology, tau-mediated neurodegeneration and microglial responses to AD-related pathologies. In addition, APOE4 is either pathogenic or shows reduced efficiency in multiple brain homeostatic pathways, including lipid transport, synaptic integrity and plasticity, glucose metabolism and cerebrovascular function. Here, we review the recent progress in clinical and basic research into the role of APOE in AD pathogenesis. We also discuss how APOE can be targeted for AD therapy using a precision medicine approach.
Apolipoprotein E and Alzheimer disease: risk, mechanisms and therapy.
Apolipoprotein E (Apo-E) is a major cholesterol carrier that supports lipid transport and injury repair in the brain. APOE polymorphic alleles are the main genetic determinants of Alzheimer disease (AD) risk: individuals carrying the ε4 allele are at increased risk of AD compared with those carrying the more common ε3 allele, whereas the ε2 allele decreases risk. Presence of the APOE ε4 allele is also associated with increased risk of cerebral amyloid angiopathy and age-related cognitive decline during normal ageing. Apo-E-lipoproteins bind to several cell-surface receptors to deliver lipids, and also to hydrophobic amyloid-β (Aβ) peptide, which is thought to initiate toxic events that lead to synaptic dysfunction and neurodegeneration in AD. Apo-E isoforms differentially regulate Aβ aggregation and clearance in the brain, and have distinct functions in regulating brain lipid transport, glucose metabolism, neuronal signalling, neuroinflammation, and mitochondrial function. In this Review, we describe current knowledge on Apo-E in the CNS, with a particular emphasis on the clinical and pathological features associated with carriers of different Apo-E isoforms. We also discuss Aβ-dependent and Aβ-independent mechanisms that link Apo-E4 status with AD risk, and consider how to design effective strategies for AD therapy by targeting Apo-E.
Alzheimer's Disease: From Pathogenesis to Emerging Therapeutic Targets.
Alzheimer's disease (AD) is the most prevalent cause of dementia and can be conceptualized as a tauopathy initiated by the accumulation of amyloid-β (Aβ) in the brain. The clinical introduction of anti-Aβ antibody therapies has marked the beginning of a new era in disease-modifying treatment for dementia. While the deleterious effects of Aβ on postsynaptic spines and axonal microtubules have been increasingly clarified, recent studies have shifted attention beyond extracellular Aβ deposition as senile plaques to the pathogenic significance of intracellular Aβ. In particular, accumulating evidence highlights lysosomes as critical sites of intracellular Aβ toxicity. Interactions between Aβ and gangliosides, v-ATPase-dependent lysosomal acidification, and lysosomal membrane integrity are the key determinants of disease progression. In parallel, additional molecular players, including components of the complement cascade and asparaginyl endopeptidase, have been implicated in linking Aβ pathology to tau dysregulation and neurodegeneration. As therapeutic strategies targeting Aβ enter clinical practice, these emerging pathways represent promising targets for the next generation of AD treatment. Here, we summarize current insights and ongoing therapeutic developments centered on these mechanisms.
Association of Periodontal Pathogens and Their Inflammatory Mediators With Alzheimer's Disease Neurodegeneration: A Systematic Review.
Periodontitis is implicated in a range of systemic conditions, including cardiovascular disease, diabetes, and respiratory disorders. Emerging evidence suggests a link between periodontal infection, inflammation, and the neurodegenerative process of Alzheimer's disease (AD). This paper aimed to systematically review observational studies examining the association of periodontal pathogens and their inflammatory products with AD neurodegeneration. The review was registered in the International Prospective Register of Systematic Reviews (PROSPERO - No. CRD42020150043). Methods followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. An electronic search (PubMed/Medical Literature Analysis and Retrieval System Online (MEDLINE), Web of Science, Scopus, Cochrane Library, grey literature) was conducted until September 2025 with no language or date restrictions. Two independent reviewers screened and extracted data. The risk of bias was assessed via the Risk Of Bias In Non-randomized Studies - of Exposures (ROBINS‑E) tool. Of 1,421 identified citations, eight studies met the inclusion criteria. Participant numbers ranged from 349 to 2,191, and ages ranged from 40 to 90 years old. Meta‑analysis was not feasible due to methodological heterogeneity. Risk of bias was moderate in five studies and serious in three. Findings indicated that higher serum IgG antibodies to periodontal pathogens and elevated inflammatory mediators, notably tumor necro
Can we refute a role for infections in Alzheimer's disease pathogenesis?
While a growing body of literature suggests a role for infections in Alzheimer's disease (AD), microbial contributions to AD remains a contentious topic, in part due to challenges in reconciling the positive evidence with studies reporting null findings. Here, we examine the evidence that argues against a role for infections in AD, while offering mechanistic hypotheses that may account for both the negative and positive findings, including dysregulated host immunity and gene-environment interactions of AD-associated genes.