BIN1 — Bridging Integrator 1

Pathway Diagram

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    style BIN1 fill:#006494,stroke:#4fc3f7,stroke-width:3px,color:#e0e0e0
    Proinflammatory_Activation["Proinflammatory Activation"]
    BIN1 -->|"regulates"| Proinflammatory_Activation
    Neurodegeneration_Related_Acti["Neurodegeneration-Related Activation"]
    BIN1 -->|"regulates"| Neurodegeneration_Related_Acti
    Late_Onset_Alzheimer_s_Disease["Late-Onset Alzheimer's Disease"]
    BIN1 -->|"risk factor for"| Late_Onset_Alzheimer_s_Disease
    Alzheimer_s_Disease["Alzheimer's Disease"]
    BIN1 -->|"associated with"| Alzheimer_s_Disease
    Alternate_Splicing["Alternate Splicing"]
    BIN1 -->|"involved in"| Alternate_Splicing
    Membrane_Dynamics["Membrane Dynamics"]
    BIN1 -->|"regulates"| Membrane_Dynamics
    Ptau["Ptau"]
    BIN1 -->|"associated with"| Ptau
    Neurons["Neurons"]
    BIN1 -->|"expressed in"| Neurons
    ALZHEIMER_S_DISEASE["ALZHEIMER'S DISEASE"]
    ALZHEIMER_S_DISEASE -->|"associated with"| BIN1
    AMYLOID["AMYLOID"]
    AMYLOID -->|"associated with"| BIN1
    APOE["APOE"]
    APOE -->|"associated with"| BIN1
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    style Neurodegeneration_Related_Acti fill:#5d4400,stroke:#4fc3f7,color:#e0e0e0
    style Late_Onset_Alzheimer_s_Disease fill:#ef5350,stroke:#4fc3f7,color:#e0e0e0
    style Alzheimer_s_Disease fill:#ef5350,stroke:#4fc3f7,color:#e0e0e0
    style Alternate_Splicing fill:#5d4400,stroke:#4fc3f7,color:#e0e0e0
    style Membrane_Dynamics fill:#5d4400,stroke:#4fc3f7,color:#e0e0e0
    style Ptau fill:#1b4d1e,stroke:#4fc3f7,color:#e0e0e0
    style Neurons fill:#0d3b54,stroke:#4fc3f7,color:#e0e0e0
    style ALZHEIMER_S_DISEASE fill:#1b5e20,stroke:#4fc3f7,color:#e0e0e0
    style AMYLOID fill:#1b5e20,stroke:#4fc3f7,color:#e0e0e0
    style APOE fill:#1b5e20,stroke:#4fc3f7,color:#e0e0e0

Introduction

BIN1 (Bridging Integrator 1, also known as Amphiphysin 2, MYC box-dependent-interacting protein 1, or AMPH2) is a gene located on chromosome 2q14.3 that encodes a member of the BAR (Bin/Amphiphysin/Rvs) adapter protein family. BIN1 is the second most significant genetic risk locus for late-onset Alzheimer’s disease (AD) after APOE, identified through genome-wide association studies (GWAS) published in 2010-2011 ^{1Genome-wide analysis of genetic loci associated with Alzheimer disease.2010 · JAMA · DOI 10.1001/jama.2010.574 · PMID 20460622Open reference2Factor inhibiting HIF (FIH-1) promotes renal cancer cell survival by protecting cells from HIF-1α-mediated apoptosis.2011 · British journal of cancer · DOI 10.1038/bjc.2011.73 · PMID 21386837Open reference}. The protein is highly enriched in neurons and plays critical roles in synaptic vesicle endocytosis, membrane dynamics, and cytoskeletal organization.

Unlike APOE, which influences AD risk primarily through effects on amyloid-beta (Aβ) aggregation and clearance, BIN1 appears to mediate its effects predominantly through modulation of tau pathology. This distinction makes BIN1 a particularly interesting therapeutic target, as it represents a pathway that connects amyloid-independent mechanisms of neurodegeneration.

Gene Structure and Expression

Genomic Organization

The BIN1 gene spans approximately 65 kb of genomic DNA on the reverse strand of chromosome 2q14.3 (coordinates: chr2:127,170,000-127,235,000, GRCh38). It consists of 20 exons encoding multiple protein isoforms through alternative splicing. The gene produces at least 10 distinct isoforms with tissue-specific expression patterns, with the neuronal isoform (BIN1-isoform-1 or BIN1hi) being most relevant to Alzheimer’s disease pathogenesis.

Brain Expression Patterns

BIN1 is expressed throughout the brain, with highest levels in:

• Cerebral cortex — particularly in pyramidal neurons (SLC17A7+) of layers II-IV

• Hippocampus — especially CA1 pyramidal neurons and dentate gyrus granule cells

• White matter — high expression in oligodendrocytes and their precursor cells

• Cerebellum — moderate expression in Purkinje cells

• Basal ganglia — moderate expression in striatal medium spiny neurons

Expression data is available from the Allen Human Brain Atlas, which provides detailed regional and cell-type-specific expression patterns across the human brain.

Allen Brain Atlas Data

Gene Expression

BIN1 (Bridging Integrator 1) shows widespread expression in the brain:

• Cerebral cortex - High in pyramidal neurons

• Hippocampus - High in CA regions and dentate gyrus

• Striatum - Moderate in medium spiny neurons

• Cerebellum - Moderate in Purkinje cells

• White matter - High in oligodendrocytes

Single-Cell Expression

Single-cell RNA-seq data from the Allen Brain Atlas shows:

• Excitatory neurons - Highest expression

• Oligodendrocytes - High expression in mature cells

• Astrocytes - Moderate, increases in reactive states

• Microglia - Low baseline, increases in disease

• Interneurons - Variable across subtypes

Brain Region Expression Levels

External Resources

• Allen Human Brain Atlas - BIN1

• Allen Mouse Brain Atlas - BIN1

• Allen Cell Type Atlas - BIN1

Single-Cell Expression

Single-cell RNA sequencing studies have revealed BIN1 expression across multiple cell types:

• Neurons — highest expression in excitatory pyramidal neurons

• Astrocytes — moderate expression, increases in reactive astrocytes

• Oligodendrocytes — high expression in mature oligodendrocytes

• Microglia — low baseline expression, increases in disease states

• Interneurons — variable expression across different subtypes

Protein Structure and Function

Domain Architecture

The BIN1 protein contains several functional domains that mediate its diverse cellular roles:

1. BAR Domain (N-terminal, ~250 amino acids) — The Bin/Amphiphysin/Rvs domain senses and induces membrane curvature. This domain forms homodimers that can tubulate membranes, making it essential for endocytosis and the formation of membrane tubules during vesicle biogenesis. The BAR domain also mediates BIN1 localization to curved membrane regions, including the necks of budding clathrin-coated vesicles ^{3Behavioral characterization of a unilateral 6-OHDA-lesion model of Parkinson's disease in mice.2005 · Behavioural brain research · DOI 10.1016/j.bbr.2005.02.023 · PMID 15922062Open reference}.

2. Clathrin-AP2 Binding Domain (CLAP) — This domain mediates interaction with the clathrin endocytic machinery. The CLAP domain specifically binds to clathrin heavy chain and the AP-2 adaptor complex, facilitating the recruitment of clathrin to sites of vesicle formation. This domain is present only in brain-specific isoforms, explaining the neuronal specificity of certain BIN1 functions.

3. MYC-Binding Domain (MBD) — Located in the central region of the protein, this domain interacts with the c-Myc transcription factor. While originally characterized in the context of tumor suppression, the MBD domain may also play roles in regulating gene expression in neurons under pathological conditions.

4. SH3 Domain (C-terminal, ~60 amino acids) — The Src Homology 3 domain mediates protein-protein interactions with proline-rich motifs. Critically, the SH3 domain directly binds to the proline-rich region of tau protein, providing a molecular mechanism for the BIN1-tau relationship central to AD pathogenesis. The SH3 domain also interacts with dynamin, synaptojanin, and other endocytic proteins ^{2Factor inhibiting HIF (FIH-1) promotes renal cancer cell survival by protecting cells from HIF-1α-mediated apoptosis.2011 · British journal of cancer · DOI 10.1038/bjc.2011.73 · PMID 21386837Open reference}.

Alternative Splicing Generates Functional Diversity

BIN1 undergoes extensive alternative splicing, producing isoforms with distinct functions:

• BIN1-isoform-1 (BIN1hi) — The neuronal isoform, characterized by inclusion of the CLAP domain. This isoform is specifically expressed in brain and is the predominant form in neurons. It plays critical roles in synaptic function and is the isoform most strongly linked to AD risk.

• BIN1-isoform-2 (BIN1lo) — The ubiquitous isoform, expressed in all tissues. This isoform lacks the CLAP domain and is involved in general cellular functions including membrane trafficking and cell division.

• Additional isoforms — Various other isoforms exist with tissue-specific distribution, some including or excluding specific protein interaction domains.

Cellular Roles in the Brain

Clathrin-Mediated Endocytosis

BIN1 plays a central role in clathrin-mediated endocytosis, one of the primary mechanisms for internalization of extracellular materials and membrane proteins. At presynaptic terminals, BIN1 performs several critical functions:

1. Vesicle nucleation — BIN1 recruits clathrin triskelions to the plasma membrane, initiating the formation of clathrin-coated pits.

2. Membrane curvature — Through its BAR domain, BIN1 senses and induces membrane curvature, facilitating the invagination necessary for vesicle formation.

3. Dynamin recruitment — BIN1 directly interacts with dynamin, the GTPase that catalyzes vesicle scission from the plasma membrane.

4. Cargo selection — BIN1 interacts with adaptor proteins that select cargo molecules for internalization, including synaptic vesicle proteins and neurotransmitter receptors.

Studies using neuronal cultures have demonstrated that BIN1 knockdown impairs synaptic vesicle endocytosis, reduces the pool of releasable synaptic vesicles, and leads to accumulation of clathrin-coated vesicles at the plasma membrane ^{4Episodic ataxias 1 and 2.2011 · Handbook of clinical neurology · DOI 10.1016/B978-0-444-51892-7.00042-5 · PMID 21827920Open reference}.

Synaptic Function

BIN1 is essential for maintaining proper synaptic function through its role in endocytosis:

• Synaptic vesicle recycling — During sustained neuronal activity, BIN1 facilitates rapid recycling of synaptic vesicles to maintain neurotransmitter release. Loss of BIN1 function leads to depletion of the readily releasable pool of vesicles.

• Receptor trafficking — BIN1 regulates the trafficking of AMPA and NMDA receptors at synapses, affecting synaptic plasticity and strength.

• Presynaptic homeostasis — BIN1 helps maintain synaptic homeostasis by regulating the balance between exocytosis and endocytosis.

Research has shown that BIN1 haploinsufficiency in neurons leads to impaired synaptic vesicle recycling and altered synaptic plasticity, phenotypes that are exacerbated in the presence of amyloid pathology ^{5Erythromelalgia.2006 · Current treatment options in cardiovascular medicine · DOI 10.1007/s11936-006-0008-8 · PMID 16533490Open reference}.

Membrane Dynamics and Cytoskeletal Organization

Beyond its role in endocytosis, BIN1 participates in broader cellular processes:

• Actin cytoskeleton — BIN1 interacts with actin regulatory proteins including cortactin and N-WASP, coordinating membrane dynamics with actin polymerization.

• Microtubule regulation — BIN1 can associate with microtubules, potentially affecting intracellular trafficking.

• Cell division — In non-neuronal cells, BIN1 plays roles in cytokinesis and cell division through its interactions with the contractile ring.

Disease Associations

Alzheimer’s Disease — GWAS Evidence

BIN1 was first identified as an AD risk locus in the large-scale GWAS meta-analyses published in 2010-2011, representing one of the first novel loci identified beyond the well-established APOE association ^{1Genome-wide analysis of genetic loci associated with Alzheimer disease.2010 · JAMA · DOI 10.1001/jama.2010.574 · PMID 20460622Open reference2Factor inhibiting HIF (FIH-1) promotes renal cancer cell survival by protecting cells from HIF-1α-mediated apoptosis.2011 · British journal of cancer · DOI 10.1038/bjc.2011.73 · PMID 21386837Open reference}. The association has been robustly replicated across multiple independent cohorts and populations worldwide.

Key Risk Variants

• rs6733839 — The lead SNP at the BIN1 locus, located ~50 kb upstream of the gene. It has a global risk allele frequency of approximately 40% and an odds ratio of 1.20 (95% CI: 1.17-1.23) for AD. This variant is thought to influence BIN1 expression levels rather than protein structure.

• rs744373 — An AD risk SNP with an odds ratio of approximately 1.17-1.19. Located in an intronic region, it affects regulatory element function.

• rs4663105 — In strong linkage disequilibrium (LD) with rs744373 within a ~6.7 kb LD block. Shares similar risk allele frequencies and effect sizes.

These variants are located in regulatory regions upstream of BIN1 and are thought to influence BIN1 expression levels rather than protein structure. Expression quantitative trait loci (eQTL) analyses have demonstrated that risk alleles are associated with reduced BIN1 expression in brain tissue, suggesting that decreased BIN1 function increases AD risk.

Population Genetics

• European ancestry — rs6733839-C allele frequency ~39%, OR ~1.20

• Asian ancestry — Similar allele frequencies but somewhat weaker LD patterns

• African ancestry — Lower allele frequency, less well-characterized effect

The BIN1-Tau Connection: A Distinct Pathway

A growing body of evidence demonstrates that BIN1 specifically mediates tau pathology rather than amyloid-beta deposition. This represents a pathway distinct from other AD risk genes and has significant implications for understanding disease mechanisms.

Tau PET Imaging Studies

Carriers of the BIN1 rs744373 risk allele show significantly higher tau-PET signal across brain regions corresponding to Braak stages II-VI, but show no increase in amyloid-PET signal. This dissociation indicates that BIN1 effects are not mediated through changes in amyloid pathology but rather through direct effects on tau accumulation or spread ^{6Genomic Correlates of Immune-Cell Infiltrates in Colorectal Carcinoma.2022 · Cell reports · DOI 10.1016/j.celrep.2016.03.075 · PMID 27149842Open reference}.

CSF Biomarker Studies

BIN1 risk variants are associated with elevated cerebrospinal fluid (CSF) total tau and phosphorylated tau (p-tau) levels, consistent with increased neuronal injury and tau pathology in carriers. Studies have shown that the effect of BIN1 on CSF tau is independent of amyloid status ^{7Enrichr: interactive and collaborative HTML5 gene list enrichment analysis tool.2013 · BMC bioinformatics · DOI 10.1186/1471-2105-14-128 · PMID 23586463Open reference}.

Direct Protein Interaction

The SH3 domain of BIN1 directly binds the proline-rich region of tau, providing a molecular mechanism for their functional relationship. This interaction:

• Occurs through the SH3 domain binding to tau’s proline-rich microtubule-binding repeat domain

• Is enhanced in the presence of certain tau phosphorylation events

• May facilitate tau’s entry into the endocytic pathway

Mutational studies have confirmed that disruption of the BIN1-tau interaction leads to altered tau trafficking and increased tau pathology in cellular models ^{2Factor inhibiting HIF (FIH-1) promotes renal cancer cell survival by protecting cells from HIF-1α-mediated apoptosis.2011 · British journal of cancer · DOI 10.1038/bjc.2011.73 · PMID 21386837Open reference}0.

Tau Propagation

BIN1 modulates tau spreading between neurons through several mechanisms:

1. Endocytosis regulation — BIN1 regulates endocytosis of tau-containing extracellular vesicles, affecting intercellular tau transmission.

2. Fragment generation — A specific BIN1 fragment accelerates tau aggregation and propagation through enhanced clathrin-mediated endocytosis.

3. Vesicle trafficking — BIN1 affects the intracellular trafficking of tau, influencing its localization and secretion.

Studies have demonstrated that BIN1 knockdown reduces tau propagation in neuronal cultures, while BIN1 overexpression enhances it ^{2Factor inhibiting HIF (FIH-1) promotes renal cancer cell survival by protecting cells from HIF-1α-mediated apoptosis.2011 · British journal of cancer · DOI 10.1038/bjc.2011.73 · PMID 21386837Open reference}1.

Network Hyperexcitability

BIN1 loss of function induces tau-dependent network hyperexcitability, providing a direct link between synaptic dysfunction and tau pathology. This mechanism may explain the cognitive deficits observed in AD patients beyond what can be accounted for by amyloid or tau burden alone ^{2Factor inhibiting HIF (FIH-1) promotes renal cancer cell survival by protecting cells from HIF-1α-mediated apoptosis.2011 · British journal of cancer · DOI 10.1038/bjc.2011.73 · PMID 21386837Open reference}2.

BIN1 Loss in AD Brain

In Alzheimer’s disease brain tissue, BIN1 protein is lost from the cytoplasmic fraction of cortical neurons, and this loss is accompanied by progressive mislocalization of phosphorylated tau to synapses. Post-mortem studies have shown:

• Reduced BIN1 expression in AD brains compared to age-matched controls

• Increased nuclear localization of BIN1 in AD neurons (the nuclear isoform lacks the CLAP domain)

• Correlation between BIN1 loss and cognitive impairment at death

These findings suggest that BIN1 normally acts to restrain pathological tau accumulation at synapses, and its loss contributes to synaptic tau pathology and cognitive decline ^{2Factor inhibiting HIF (FIH-1) promotes renal cancer cell survival by protecting cells from HIF-1α-mediated apoptosis.2011 · British journal of cancer · DOI 10.1038/bjc.2011.73 · PMID 21386837Open reference}3.

Cognitive Effects

BIN1 risk allele carriers show faster rates of cognitive decline compared to non-carriers, and this effect is mediated by accelerated global tau-PET accumulation in the presence of amyloid pathology. Importantly, BIN1 effects on tau accumulation are amyloid-dependent, consistent with the amyloid cascade model where amyloid pathology triggers downstream tau spread ^{2Factor inhibiting HIF (FIH-1) promotes renal cancer cell survival by protecting cells from HIF-1α-mediated apoptosis.2011 · British journal of cancer · DOI 10.1038/bjc.2011.73 · PMID 21386837Open reference}4.

Molecular Mechanisms in AD Pathogenesis

Endosomal Dysfunction

Recent research has revealed that BIN1 plays a critical role in maintaining endosomal homeostasis through its interaction with RIN3 (Ras and Rab Interactor 3) and RAB5 ^{2Factor inhibiting HIF (FIH-1) promotes renal cancer cell survival by protecting cells from HIF-1α-mediated apoptosis.2011 · British journal of cancer · DOI 10.1038/bjc.2011.73 · PMID 21386837Open reference}5:

• BIN1-RIN3 interaction — The neuronal isoform BIN1hi binds to RIN3’s proline-rich domain, inhibiting RIN3-mediated RAB5 activation

• Endosomal sizing — Disruption of BIN1-RIN3 binding leads to RAB5 hyperactivation and enlargement of early endosomes (eEEs), a hallmark of early AD pathology

• APP trafficking — This pathway affects amyloid precursor protein (APP) trafficking and Aβ generation

Rare familial AD RIN3 missense mutations within the BIN1-binding domain (R427Q and P477S) impair BIN1-RIN3 binding in vitro, leading to endosomal enlargement. This represents a novel mechanism linking genetic risk to endosomal pathology.

Transcriptomic Changes

Transcriptomic profiling in cellular models with BIN1 deficiency has revealed dysregulated expression of AD-related genes:

• Small GTPase regulators — altered expression of RAB and RHO family genes

• Cholesterol homeostasis modulators — changes in genes involved in lipid metabolism

• WNT signaling components — dysregulation of WNT pathway genes

• Synaptic function genes — altered expression of synaptic plasticity genes

These changes suggest that BIN1 loss affects multiple pathways relevant to AD pathogenesis beyond its direct effects on tau.

Therapeutic Implications

BIN1 as a Therapeutic Target

BIN1 represents a promising therapeutic target for Alzheimer’s disease due to its unique position in AD pathogenesis:

1. Stabilizing BIN1-tau interaction — Small molecules or peptides that enhance the BIN1-tau binding could reduce tau pathology

2. RAB5 inhibition — Developing inhibitors of RAB5 activation or stabilizers of BIN1-RIN3 interaction could prevent endosomal dysfunction

3. Restoring BIN1 expression — Gene therapy approaches to increase BIN1 expression in the brain

4. Modulating endocytosis — Targeting the endocytic pathway downstream of BIN1 to enhance clearance of toxic proteins

Biomarker Potential

BIN1 and its interacting proteins show potential as biomarkers:

• CSF BIN1 —Elevated in AD patients, correlates with disease severity

• RIN3 variants — Genetic modifiers of BIN1 function

• Endosomal markers — RAB5 activation state as a biomarker

Relationship to Other AD Risk Genes

BIN1 interacts with several other AD risk genes and pathways:

• PICALM — Both are involved in clathrin-mediated endocytosis and were identified as AD risk loci in the same GWAS. They may have synergistic effects on APP processing.

• CLU (Clusterin) — Another GWAS-identified gene involved in amyloid clearance. BIN1 and CLU may converge on pathways regulating protein aggregation and clearance.

• VPS35 — Part of the retromer complex, which works with BIN1 in endosomal trafficking. VPS35 mutations cause familial Parkinson’s disease, suggesting shared pathways between AD and PD.

• RIN3 — A genetic modifier of BIN1 function, with rare variants increasing AD risk through disruption of the BIN1-RIN3 interaction.

Brain Atlas Resources

• Allen Human Brain Atlas

• Allen Human Brain Atlas: BIN1 search

• Allen Mouse Brain Atlas: BIN1 search

• Allen Cell Type Atlas

• BrainSpan Developmental Transcriptome

Brain Region Expression Levels

See Also

• APOE Protein

• Tau Protein

• Amyloid-Beta Protein

• Alzheimer’s Disease

• PICALM Gene

• CLU Gene

• Endocytic Pathway

• Tau Pathology

External Links

• NCBI Gene: BIN1

• Ensembl: ENSG00000136717

• UniProt: O00499

• OMIM: 601248

• GeneCards: BIN1

• GWAS Catalog: BIN1

• AlzForum: BIN1

Recent Research (2024-2026)

• 2024: RIN3 mutations impairing binding of BIN1 lead to RAB5 hyperactivation demonstrates genetic links between vesicular trafficking and AD pathology.

• 2024: BIN1 in tauopathies: mechanisms and therapeutic implications reviews BIN1’s role in neurodegeneration.

• 2023: Studies on BIN1 isoforms reveal isoform-specific functions in neuronal health and disease.