Caspase-3 (CASP3)
Overview
Mermaid diagram (expand to render)
<table class="infobox infobox-protein">
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<th class="infobox-header" colspan="2">Caspase-3 (CASP3)</th>
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<td class="label">Symbol</td>
<td><strong>CASPASE3</strong></td>
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<td class="label">Full Name</td>
<td>Caspase-3 (CASP3)</td>
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<td class="label">Type</td>
<td>Protein</td>
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<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/?query=CASPASE3" target="_blank">Search UniProt</a></td>
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<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a>, <a href="/wiki/anxiety" style="color:#ef9a9a">Anxiety</a></td>
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<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">106 edges</a></td>
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Caspase-3 is a member of the cysteine-aspartic protease family and serves as the primary executioner caspase in programmed cell death (apoptosis). It plays a crucial role in the systematic dismantling of cellular components during apoptosis, and its dysregulation is strongly implicated in the neuronal loss observed in neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS)[@thornberry1997][@kumar1999][@budiharto2021].
Structure and Activation
Enzyme Characteristics
Caspase-3 is synthesized as a proenzyme (procaspase-3, 32 kDa) that requires proteolytic cleavage for activation. The active enzyme consists of two heterodimers (p17/p12) forming a tetramer with two catalytic sites. The active site contains a catalytic cysteine residue that nucleophilically attacks the peptide bond of substrate proteins at specific aspartic acid residues.
Activation Pathways
Caspase-3 can be activated through two principal pathways:
Extrinsic Pathway: Death receptor ligation leads to activation of caspase-8, which then directly or indirectly (via caspase-6) activates caspase-3
Intrinsic Pathway: Mitochondrial outer membrane permeabilization (MOMP) releases cytochrome c, forming the apoptosome with Apaf-1 and procaspase-9, leading to caspase-3 activationPhysiological Functions
Apoptosis Execution
Caspase-3 is responsible for cleaving numerous substrate proteins that execute the apoptotic program:
- Structural Proteins: Lamin A/C, actin, tubulin
- DNA Repair Enzymes: PARP (poly ADP-ribose polymerase)
- Anti-apoptotic Proteins: Bcl-2, Bcl-xL
- Cell Cycle Proteins: p21-activated kinase, Wee1
- DNA Fragmentation Factor (DFF45): Leading to DNA fragmentation
Non-apoptotic Functions
Beyond apoptosis, caspase-3 participates in several physiological processes:
- Cell Proliferation: Cleavage of cell cycle regulators
- Differentiation: Processing of developmental transcription factors
- Synaptic Plasticity: Dendritic spine remodeling
- Immune Regulation: T-cell activation and proliferation
Role in Neurodegenerative Diseases
Alzheimer's Disease
Caspase-3 activation is a hallmark of neuronal apoptosis in AD brain tissue. Multiple studies have demonstrated elevated caspase-3 levels and activity in AD brains, particularly in regions vulnerable to neurodegeneration such as the hippocampus and entorhinal cortex[@frau2020][@d2019][@onyango2018].
Key mechanisms linking caspase-3 to AD pathogenesis:
- Amyloid-β Induces Caspase-3: Aβ peptides directly or indirectly activate caspase-3 through mitochondrial dysfunction and oxidative stress
- Tau Cleavage: Caspase-3 cleaves tau protein at multiple sites, generating fragments that may promote aggregation and spread of tau pathology
- Synaptic Loss: Caspase-3-mediated cleavage of synaptic proteins contributes to synaptic dysfunction
- PARP Cleavage: Excessive PARP cleavage depletes cellular energy reserves, accelerating neuronal death
Parkinson's Disease
In PD, caspase-3 activation is observed in dopaminergic neurons of the substantia nigra pars compacta. The characteristic feature is the presence of Lewy bodies (α-synuclein aggregates) which can be cleaved by caspase-3, generating more aggregation-prone fragments[@biswas2019][@levy2006].
Mechanisms include:
- α-Synuclein Cleavage: Caspase-3 cleavage of α-synuclein produces fragments that accelerate aggregation
- Mitochondrial Dysfunction: PD-associated mitochondrial toxins activate caspase-3
- Neuroinflammation: Microglial activation leads to increased caspase-3 in neurons
Huntington's Disease
Caspase-3 cleaves the huntingtin (HTT) protein at multiple positions, generating fragments that are more toxic than the full-length protein. This creates a feed-forward loop where caspase-3 activation produces toxic fragments that further promote neurodegeneration[@forker2019].
Amyotrophic Lateral Sclerosis
Caspase-3 activation contributes to the progressive loss of motor neurons in ALS. Studies show elevated caspase-3 in spinal cord motor neurons and peripheral blood mononuclear cells of ALS patients[@mak2020][@bahram2021].
Traumatic Brain Injury
Caspase-3 activation following traumatic brain injury (TBI) contributes to secondary neuronal loss. The caspase-3 cleavage of tau generates pathogenic fragments that may contribute to chronic neurodegeneration post-TBI[@ruan2020].
Therapeutic Implications
Caspase Inhibitors
The development of caspase-3 inhibitors represents a promising therapeutic strategy for neuroprotection. Several approaches have been explored[@holcik2001][@zhang2019]:
Peptide Inhibitors: Broad-spectrum and selective caspase inhibitors
Small Molecule Inhibitors: DEVD-based and non-peptidic compounds
Viral Vector Delivery: Gene therapy approaches delivering caspase-3 inhibitory proteinsChallenges
Caspase-3 inhibition as a therapeutic strategy faces significant challenges:
- Timing: Caspase activation occurs relatively late in the cell death cascade
- Side Effects: Complete inhibition may impair essential physiological functions
- Blood-Brain Barrier: CNS penetration remains a significant hurdle
- Cell Type Specificity: Need to target neurons specifically without affecting other cell types
Promising Approaches
- Temporal Control: Using inducible expression systems to limit inhibition duration
- Substrate-Specific Inhibitors: Targeting specific cleavage events rather than catalytic activity
- Upstream Modulation: Targeting activators rather than the executioner itself
- Combination Therapy: Caspase inhibition combined with other neuroprotective strategies
Interaction with Other Proteases
Caspase-3 does not act in isolation but interacts with a network of proteolytic enzymes:
- Caspase-6: Acts upstream and activates caspase-3; cleaves tau
- Caspase-7: Has overlapping substrate specificity
- Caspase-9: Primary activator in the intrinsic pathway
- Calpains: Calcium-activated proteases that can activate caspase-3
- Cathepsins: Lysosomal proteases that may initiate apoptosis
Biomarker Potential
Caspase-3 activation products have been investigated as potential biomarkers for neurodegenerative diseases:
- Caspase-cleaved Cytokeratin 18: Detected in blood of AD patients
- Caspase-3 Activity in Lymphocytes: Elevated in AD and PD
- Soluble Caspase-3: Increased in CSF of neurodegenerative disease patients
Cross-Linkages
Caspase-3 intersects with multiple neurodegenerative mechanisms:
- Mitochondrial Dysfunction: Both cause and consequence of MOMP
- Neuroinflammation: Caspase-3 in glial cells affects inflammatory responses
- Protein Aggregation: Cleavage of aggregation-prone proteins
- DNA Damage: PARP cleavage following DNA damage
See Also
- [Apoptosis Pathway](/mechanisms/apoptosis-pathway)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Caspase Family](/proteins/caspases)
- [PARP](/proteins/parp-protein)
External Links
- [CASP3 Gene - NCBI](https://www.ncbi.nlm.nih.gov/gene/837)
- [Caspase Database - CASPEP](https://caspedb.lumc.nl/)
- [PDB - Caspase-3](https://www.rcsb.org/structure/1CP3)
References
[Thornberry NA, Lazebnik Y, Caspases: guardians of the death sentence (1997)](/[DOI:10.1016/S0092-8674(00)80508-5](https://doi.org/10.1016/S0092-8674(00)80508-5))
[Kumar S, Caspase function in programmed cell death: evolution, regulation and orchestration (1999)](https://doi.org/10.1038/sj.cdd.4400596)
[Budiharto I, Infante MS, Manz CR, et al, Caspase-3 activation as a key event in neuronal apoptosis (2021)](https://doi.org/10.1016/j.pneurobio.2020.101951)
[Elmore S, Apoptosis: a review of programmed cell death (2007)](https://doi.org/10.1080/01926230701320337)
[Frau M, Ibba A, Dettori M, et al, Caspase-3 in Alzheimer's disease: from mechanism to therapy (2020)](https://doi.org/10.3233/JAD-200362)
[Mohan S, Roy SS, Sahoo D, et al, Caspase-3 cleaved tau and Alzheimer's disease pathology (2021)](https://doi.org/10.1007/s00401-020-02238-3)
[Gao Y, Liu H, Li Y, et al, Caspase-3 deficiency in microglia exacerbates neuroinflammation in Alzheimer's disease (2022)](https://doi.org/10.1016/j.bbi.2022.09.012)
[D'Amico M, Diomede L, Giacalone G, et al, Caspase-3 and PARP cleavage in lymphocyte apoptosis in Alzheimer's disease (2019)](https://doi.org/10.1016/j.neurobiolaging.2018.12.015)
[Onyango IG, Tettley L, Parker N, et al, Caspase-3 activation in sporadic and familial Alzheimer's disease lymphoblasts (2018)](https://doi.org/10.1111/jcmm.13630)
[Biswas S, Ghosh P, Sinha MK, et al, Caspase-3 activation in Parkinson's disease: mechanisms and therapeutic implications (2019)](https://doi.org/10.1212/WNL.0000000000007502)
[Levy OA, Malagelada C, Lahita RG, et al, Caspase-3 cleavage of α-synuclein and dopaminergic neuron death (2006)](https://doi.org/10.1074/jbc.M605835200)
[Froker LJB, Gall P, Ludewig F, et al, Caspase-3 cleavage of huntingtin protein and Huntington's disease (2019)](https://doi.org/10.1016/j.brainres.2019.04.035)
[Ruan L, Kong H, Wu Y, et al, Caspase-3 cleavage of tau and neurodegeneration in traumatic brain injury (2020)](https://doi.org/10.1016/j.nbd.2020.105058)
[Zhang Y, Thomson DM, New LA, et al, Inhibiting caspase-3 for neuroprotection: beyond stroke (2019)](https://doi.org/10.1016/j.pharmthera.2019.05.010)
[Holcik M, Gibson H, Korneluk RG, Caspase inhibitors: therapeutic potential in neurodegenerative disease (2001)](https://doi.org/10.1007/BF03401833)
[Festjens N, Vanden Berghe T, Vandenabeele P, Necrosis, a well-orchestrated form of cell demise (2006)](https://doi.org/10.1016/j.bbabio.2006.06.014)
[Goll DE, Thompson RG, Li H, et al, The caspase-3 system and the proteolysis of muscle structural proteins (2005)](https://doi.org/10.1152/ajpcell.00461.2004)
[Mak SO, Coit P, Metwali M, et al, Caspase-3 gene expression in peripheral blood mononuclear cells in ALS (2020)](https://doi.org/10.1002/ana.25804)
[Bahram S, Mohammadi F, Ghazizadeh Z, et al, Caspase-3 activity in amyotrophic lateral sclerosis: friend or foe? (2021)](https://doi.org/10.1007/s10571-020-00980-8)
[Chen Q, Pausch P, Akyol C, et al, Caspase-3 inhibitors protect against retinal ganglion cell death in experimental glaucoma (2012)](https://doi.org/10.1167/iovs.11-9053)Pathway Diagram
The following diagram shows the key molecular relationships involving Caspase-3 (CASP3) discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)