Caspase-3 (CASP3)

Caspase-3 (CASP3)

Overview

Caspase-3 (CASP3)

Overview

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">Caspase-3 (CASP3)</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>CASPASE3</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Caspase-3 (CASP3)</td>
</tr>
<tr>
<td class="label">Type</td>
<td>Protein</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/?query=CASPASE3" target="_blank">Search UniProt</a></td>
</tr>
<tr>
<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>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">106 edges</a></td>
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</table>

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:

Physiological 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]:

Challenges

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

Pathway Diagram

The following diagram shows the key molecular relationships involving Caspase-3 (CASP3) discovered through SciDEX knowledge graph analysis: