casp3

Introduction

Pathway Diagram

flowchart TD
    CASP3["CASP3<br/>Gene"]
    CASPASE3["CASPASE-3<br/>Protein"]
    APOPTOSIS["Apoptotic<br/>Cell Death"]
    
    ALS["Amyotrophic<br/>Lateral Sclerosis"]
    MS["Multiple<br/>Sclerosis"]
    NEURODEGENERATION["Neuronal<br/>Death"]
    
    LRRK2["LRRK2<br/>Kinase"]
    OPTN["OPTINEURIN<br/>Autophagy Receptor"]
    SQSTM1["SQSTM1/p62<br/>Autophagy Adapter"]
    
    AKT1["AKT1<br/>Survival Kinase"]
    AUTOPHAGY["Autophagy<br/>Pathway"]
    ATG16L1["ATG16L1<br/>Autophagy Protein"]
    
    STING1["STING<br/>Innate Immunity"]
    CGAS["cGAS<br/>DNA Sensor"]
    INFLAMMATION["Neuroinflammation"]
    
    CASP3 -->|"encodes"| CASPASE3
    CASPASE3 -->|"executes"| APOPTOSIS
    APOPTOSIS -->|"drives"| NEURODEGENERATION
    
    NEURODEGENERATION -->|"contributes to"| ALS
    NEURODEGENERATION -->|"contributes to"| MS
    
    LRRK2 -->|"interacts with"| CASP3
    OPTN -->|"interacts with"| CASP3
    SQSTM1 -->|"interacts with"| CASP3
    
    CASP3 -->|"regulates"| AKT1
    CASP3 -->|"regulates"| ATG16L1
    ATG16L1 -->|"promotes"| AUTOPHAGY
    AUTOPHAGY -->|"protects against"| NEURODEGENERATION
    
    CASP3 -->|"regulates"| CGAS
    STING1 -->|"interacts with"| CASP3
    CGAS -->|"activates"| INFLAMMATION
    INFLAMMATION -->|"promotes"| NEURODEGENERATION
    
    style CASP3 fill:#006494
    style CASPASE3 fill:#006494
    style APOPTOSIS fill:#ef5350
    style NEURODEGENERATION fill:#ef5350
    style ALS fill:#5d4400
    style MS fill:#5d4400
    style AUTOPHAGY fill:#1b5e20
    style AKT1 fill:#1b5e20
    style LRRK2 fill:#4a1a6b
    style OPTN fill:#4a1a6b
    style SQSTM1 fill:#4a1a6b
    style ATG16L1 fill:#4a1a6b
    style INFLAMMATION fill:#ef5350
    style STING1 fill:#4a1a6b
    style CGAS fill:#4a1a6b

Caspase 3 (Casp3) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

Caspase 3 (CASP3) is an executioner caspase that executes the final stages of apoptosis. It is encoded by the CASP3 gene located on chromosome 4q34 and is one of the most studied caspases in neurodegeneration research. As the principal executioner caspase, caspase-3 is responsible for the proteolytic dismantling of cellular components during programmed cell death. However, emerging research reveals that caspase-3 also has critical non-apoptotic functions in synaptic plasticity, learning, and memory. ^{1Neuronal caspase-3 signaling: Not only cell death2010 · DOI 10.1038/cdd2009180Open reference2Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer's disease2003}

Gene Information

Protein Structure and Function

Domain Architecture

Caspase-3 is synthesized as an inactive zymogen (procaspase-3) consisting of: ^{1Neuronal caspase-3 signaling: Not only cell death2010 · DOI 10.1038/cdd2009180Open reference}

1. Prodomain (N-terminal): Short prodomain (~30 amino acids) that lacks a CARD or DED domain, distinguishing caspase-3 from initiator caspases

2. Large Subunit (p20, ~20 kDa): Contains the catalytic cysteine residue (Cys163) and substrate-binding pocket

3. Small Subunit (p11, ~11 kDa): Completes the active site configuration

4. Linker Region: Contains the interdomain linker with cleavage sites (Asp9, Asp28, Asp175)

Activation Mechanism

Caspase-3 requires proteolytic cleavage for activation and is activated by both apoptotic pathways:

1. Intrinsic pathway: Mitochondrial MOMP → cytochrome c release → apoptosome formation → caspase-9 activation → caspase-3 cleavage

2. Extrinsic pathway: Death receptor activation → DISC formation → caspase-8 activation → caspase-3 cleavage

The cleavage process:

• First cleavage: separates prodomain from the large subunit

• Second cleavage: separates large and small subunits

• Active enzyme: heterotetramer (p17/p11)₂

Substrate Specificity

Activated caspase-3 cleaves over 600 known substrates: ^{4Caspase-3 in synaptic function and dysfunction2016 · DOI 10.1007/s12035-016-9712-8Open reference}

• DNA repair proteins: PARP, DNA-PKcs, XRCC1

• Structural proteins: Lamin A/C, β-catenin, tubulin, actin

• Signal transduction: PKC isoforms, Akt, BAD

• Anti-apoptotic proteins: Bcl-2, Mcl-1, XIAP

• Synaptic proteins: PSD-95, Synaptophysin, AMPA receptor subunits

Non-Apoptotic Functions

Caspase-3 has critical functions beyond cell death: ^{5Caspase-3 activation in Parkinson's disease models2020 · DOI 10.1038/s41531-020-00122-5Open reference}

Synaptic Plasticity

• Long-term depression (LTD): Local caspase-3 activation at synapses mediates AMPA receptor internalization

• Synaptic pruning: Developmental and activity-dependent synapse elimination

• Learning and memory: Caspase-3 is required for memory consolidation in certain paradigms

Cellular Processes

• Cell cycle regulation: Caspase-3 can cleave cell cycle proteins

• Differentiation: Role in neural progenitor cell differentiation

• Migration: Affects neuronal migration during development

Important: Complete inhibition of caspase-3 may disrupt normal synaptic function, complicating therapeutic targeting.

Role in Neurodegeneration

Alzheimer’s Disease

Caspase-3 plays multiple roles in AD pathogenesis: ^{6Activation of caspase-3 in the brains of patients with Alzheimer's disease19992Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer's disease20037Caspase-3 cleavage of tau generates toxic fragments2018 · DOI 10.1186/s40478-018-0536-4Open reference}

1. Synaptic loss: Cleaves synaptic proteins including PSD-95, synaptophysin, leading to synaptic dysfunction and loss ^{4Caspase-3 in synaptic function and dysfunction2016 · DOI 10.1007/s12035-016-9712-8Open reference}

2. Tau cleavage: Generates truncated tau fragments that form aggregates more readily than full-length tau ^{2Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer's disease2003}0

   • Cleavage at Asp421 generates Δtau421

   • Truncated tau spreads between neurons in a prion-like manner

3. Amyloid effects: Activated by Aβ toxicity through both intrinsic and extrinsic pathways

4. DNA damage: Cleaves PARP, leading to energy depletion and bioenergetic failure ^{2Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer's disease2003}1

5. Apoptotic execution: Final executioner of the apoptotic cascade

Molecular Cascade in AD

• Aβ oligomers bind to neuronal receptors

• Calcium dysregulation and mitochondrial stress

• Activation of initiator caspases (caspase-8, -9)

• Caspase-3 activation and substrate cleavage

• Synaptic dysfunction precedes neuronal loss

Parkinson’s Disease

In PD, caspase-3 mediates dopaminergic neuron death: ^{2Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer's disease2003}2

1. Mitochondrial dysfunction: Complex I inhibition leads to MOMP and caspase-3 activation

2. α-Synuclein toxicity: Oligomeric α-synuclein triggers caspase-3 activation

3. Oxidative stress: ROS accumulation damages mitochondria, triggering apoptosis

4. Neuroinflammation: Activated microglia release pro-inflammatory cytokines that sensitize neurons to apoptosis

5. Evidence: Active caspase-3 is elevated in PD substantia nigra

Dopaminergic Neuron Vulnerability

• High metabolic demand with limited antioxidant capacity

• Low Bcl-2 family anti-apoptotic proteins

• Exposure to dopamine oxidation products

• Age-related mitochondrial decline

ALS

Caspase-3 is elevated in ALS and contributes to motor neuron death: ^{2Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer's disease2003}3

• Motor neurons show caspase-3 activation

• Contributes to neuromuscular junction denervation

• Activated by excitotoxicity and mitochondrial dysfunction

• Cleaves key structural proteins in motor neurons

Stroke and TBI

Following cerebral ischemia or trauma: ^{2Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer's disease2003}4

• Executes necrotic and apoptotic cell death

• Cleaves neuronal cytoskeletal proteins

• Contributes to blood-brain barrier disruption

• Caspase-3 inhibitors show neuroprotective effects in preclinical models

Huntington’s Disease

• Mutant huntingtin triggers mitochondrial dysfunction

• Caspase-3 activation in striatal neurons

• Contributes to medium spiny neuron loss

Therapeutic Targeting

Caspase-3 inhibitors have been extensively studied: ^{2Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer's disease2003}5^{2Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer's disease2003}6

Challenges

• Non-apoptotic functions: Complete inhibition disrupts synaptic plasticity

• BBB penetration: Most inhibitors don’t cross the blood-brain barrier

• Timing: Intervention likely needs to occur early in disease

• Selectivity: Pan-caspase inhibitors have broader side effects

Alternative Approaches

• Upstream targeting: Inhibit initiator caspases or upstream activators

• Substrate protection: Develop peptides that prevent caspase-3 from cleaving critical substrates

• Gene therapy: Dominant-negative caspase-3 constructs

Substrate-Specific Inhibition

Targeting specific caspase-3 substrates offers a promising strategy: ^{2Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer's disease2003}7

• Tau protection: Peptides that block caspase-3 cleavage of tau

• Synaptic protein preservation: Inhibiting cleavage of PSD-95, synaptophysin

• Nuclear substrate protection: Preventing PARP cleavage and DNA damage

• Combination approaches: Multiple substrate protection strategies

Clinical Development Status

Caspase-3 inhibitors in the drug development pipeline: ^{2Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer's disease2003}8

• Preclinical candidates: Multiple selective inhibitors in development

• Delivery methods: Focus on BBB-penetrant small molecules

• Combination therapies: Dual caspase-3 and amyloid/tau targeting

• Biomarker integration: Patient selection based on caspase-3 activity

Ferroptosis Cross-Talk

Caspase-3 has been implicated in ferroptosis, a form of regulated necrosis: ^{2Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer's disease2003}9

• Molecular intersection: Caspase-3 can influence ferroptosis pathways

• GPX4 regulation: Cross-talk with key ferroptosis regulators

• Therapeutic implications: Combined targeting approaches

• Disease relevance: Implications for neurodegeneration

Structural Biology

Active Site Architecture

The caspase-3 active site provides targets for drug design: ^{3Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson's disease2000}0

• Catalytic cysteine: Cys163 performs nucleophilic attack

• Substrate binding pocket: Recognizes DEVD tetrapeptide sequence

• Dimer interface: Active enzyme functions as a dimer

• Allosteric regulation: Substrate binding induces conformational changes

Substrate Recognition

Caspase-3 cleaves over 600 known substrates with distinct specificities: ^{3Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson's disease2000}1

• Optimal sequence: Tetrapeptide recognition (DEVD)

• Extended binding: Additional contacts beyond P4-P1

• Substrate diversity: Proteins, lipids, and nucleic acids

• Cleavage consequences: Activation, inactivation, or relocalization

Cellular and Molecular Mechanisms

Synaptic caspase-3 Activity

Local caspase-3 activation at synapses mediates critical functions: ^{3Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson's disease2000}2^{3Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson's disease2000}3

• LTD induction: AMPA receptor internalization through caspase-3 cleavage

• Synaptic pruning: Developmental and activity-dependent elimination

• Memory consolidation: Required for certain memory paradigms

• Spatial regulation: Local translation and activation at dendritic spines

Nuclear Events

Caspase-3 translocates to the nucleus during apoptosis: ^{3Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson's disease2000}4

• PARP cleavage: Generates death-inducing DNA fragments

• Chromatin condensation: Nuclear lamina breakdown

• Transcriptional effects: Alters gene expression programs

• DNA repair inhibition: Impairs cellular repair capacity

Mitochondrial Cross-Talk

Caspase-3 interacts with mitochondrial proteins: ^{3Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson's disease2000}5

• Pro-apoptotic effects: Cleaves anti-apoptotic proteins

• Cytochrome c release: Amplifies intrinsic pathway

• Energy depletion: PARP cleavage causes NAD+ loss

• Bioenergetic failure: ATP depletion terminates survival programs

Neuroinflammation Role

Caspase-3 in neuroinflammatory processes: ^{3Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson's disease2000}6

• Microglial activation: Regulates inflammatory responses

• Cytokine processing: Can process inflammatory mediators

• Immune cell death: Controls peripheral immune infiltration

• Dual roles: Both pro-inflammatory and protective functions

Inflammatory Cascade Regulation

Caspase-3 contributes to neuroinflammation through multiple pathways: ^{3Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson's disease2000}7

• Cytokine activation: Processing of inflammatory interleukins

• Microglial survival: Regulation of activated microglia

• Blood-brain barrier: Effects on BBB integrity

• Peripheral immune modulation: Cross-talk with systemic immunity

Imaging and Diagnostics

Caspase-3 Activity Imaging

Advanced imaging techniques for caspase-3: ^{3Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson's disease2000}8

• Fluorescent probes: Activatable imaging agents

• PET tracers: Radiolabeled caspase-3 inhibitors

• Optical imaging: Intraoperative guidance

• Longitudinal monitoring: Tracking disease progression

Diagnostic Applications

Clinical diagnostic potential:

• Early detection: Identifying pre-symptomatic changes

• Disease progression: Monitoring caspase-3 activity over time

• Treatment response: Predicting therapeutic efficacy

• Patient stratification: Selecting patients for caspase-targeted therapy

Therapeutic Delivery Strategies

Blood-Brain Barrier Penetration

Overcoming delivery challenges: ^{3Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson's disease2000}9

• Lipid-based carriers: Improving brain penetration

• Nanoparticle approaches: Targeted delivery systems

• Intranasal delivery: Direct nose-to-brain pathways

• Focused ultrasound: BBB opening for enhanced delivery

Cell-Type Specific Targeting

Selective targeting strategies:

• Neuron-specific delivery: Leveraging neuronal receptors

• Viral vectors: AAV-mediated gene therapy

• Peptide conjugates: Cell-penetrating peptides

• Antibody-based approaches: Engineered antibodies

Genetic Associations

Polymorphisms

• rs12108497: May influence caspase-3 expression

• rs3749919: Associated with AD risk in some populations

Expression Changes

• CASP3 expression is elevated in AD brain, particularly in vulnerable regions

• Active caspase-3 levels are elevated in PD substantia nigra

• Increased in ALS motor neurons and spinal cord

Biomarker Potential

Caspase-3 cleavage products are being explored as biomarkers: ^{1Neuronal caspase-3 signaling: Not only cell death2010 · DOI 10.1038/cdd2009180Open reference}0

• CSF biomarkers: Caspase-3 cleaved fragments detectable in cerebrospinal fluid

• Blood biomarkers: Extracellular vesicles containing caspase-3 cleavage products

• Therapeutic monitoring: Caspase-3 activity may predict treatment response

Interaction Network

Caspase-3 interacts with multiple proteins in the cell death machinery:

Cross-Linking

Related Proteins

• Caspase-8 - Extrinsic pathway initiator

• Caspase-9 - Intrinsic pathway initiator

• Caspase-6 - Related effector caspase

• PARP1 - DNA repair enzyme substrate

Related Mechanisms

• Apoptosis - Programmed cell death pathway

• Synaptic Loss - Early event in AD

• Tau Pathology - NFT formation

• Neuroinflammation - Inflammatory processes

Related Diseases

• Alzheimer’s Disease

• Parkinson’s Disease

• ALS

• Huntington’s Disease

Disease Associations

Expression in the Brain

CASP3 is ubiquitously expressed in the brain: ^{1Neuronal caspase-3 signaling: Not only cell death2010 · DOI 10.1038/cdd2009180Open reference}3

• Neurons: All neuronal subtypes, highest expression in pyramidal neurons

• Astrocytes: Lower expression than neurons

• Microglia: Activated microglia show increased expression

• Oligodendrocytes: Variable expression

Region-Specific Patterns

• Hippocampus: High expression in CA1-CA3 and dentate gyrus

• Cortex: Layer 5 pyramidal neurons show high expression

• Substantia nigra: Dopaminergic neurons

• Cerebellum: Purkinje cells

Key Publications

^{1Neuronal caspase-3 signaling: Not only cell death2010 · DOI 10.1038/cdd2009180Open reference}4 Shimohama S, et al. Activation of caspase-3 in the brains of patients with Alzheimer’s disease. Biochem Biophys Res Commun. 1999.

^{1Neuronal caspase-3 signaling: Not only cell death2010 · DOI 10.1038/cdd2009180Open reference}5 Gamblin TC, et al. Caspase cleavage of tau: linking amyloid and neurofibrillary tangles in Alzheimer’s disease. Proc Natl Acad Sci USA. 2003.

^{1Neuronal caspase-3 signaling: Not only cell death2010 · DOI 10.1038/cdd2009180Open reference}6 Tatton NA. Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson’s disease. Exp Neurol. 2000.

^{1Neuronal caspase-3 signaling: Not only cell death2010 · DOI 10.1038/cdd2009180Open reference}7 D’Amelio M, et al. Neuronal caspase-3 signaling: Not only cell death. Cell Death & Differentiation. 2010.

See Also

• Apoptosis Pathway

• Alzheimer’s Disease

• Parkinson’s Disease

• Caspase 8

• Caspase 9

• PARP Gene

External Links

• NCBI Gene: CASP3

• UniProt: CASP3

• Ensembl: CASP3

• Allen Human Brain Atlas - CASP3 Expression

Background

The study of Caspase 3 (Casp3) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.