Caspase-7 Protein

Introduction

Caspase-7 is an executioner caspase in the caspase family of cysteine proteases that plays a central role in programmed cell death (apoptosis). It is one of the key effector caspases that executes the apoptotic program by cleaving a broad range of cellular substrates. In neurodegenerative diseases like Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis (ALS), caspase-7 activation contributes to neuronal loss through both apoptosis and non-apoptotic functions. Understanding caspase-7’s role in neurodegeneration is crucial for developing therapeutic strategies targeting cell death pathways.

Protein Infobox

Structure

Caspase-7 is synthesized as a zymogen (pro-caspase-7) that requires activation:

• Pro-domain: Contains a short N-terminal prodomain (~23 amino acids)

• Large subunit (p20): Contains the catalytic cysteine residue

• Small subunit (p12): Completes the active site formation

• Active form: The heterotetrameric active caspase-7 consists of two p20/p12 heterodimers

• Catalytic dyad: His237 and Cys277 form the catalytic dyad essential for protease activity

• Substrate-binding pocket: Recognizes the DEVD tetrapeptide sequence (caspase-7 preferred cleavage site)

Crystal structures of active caspase-7 (PDB: 1F1J, 3KAI) have revealed the dimeric architecture and substrate-binding mechanisms.

Normal Function

In healthy cells, caspase-7 participates in several important processes:

1. Apoptosis execution: Caspase-7 is activated by initiator caspases (caspase-8, caspase-9) via proteolytic cleavage

2. Substrate cleavage: Cleaves structural proteins (lamins, gelsolin), repair enzymes (PARP), and signaling molecules

3. Cell disassembly: Facilitates cellular dismantling during programmed cell death

4. Development: Essential for normal embryonic development (caspase-7 knockout mice are viable but show defects)

5. Immune regulation: Participates in immune cell homeostasis and cytokine processing

Role in Neurodegeneration

Alzheimer’s Disease

Caspase-7 is activated in AD brains and contributes to neuronal death:

• Amyloid-beta toxicity: Aβ exposure triggers caspase-7 activation in neurons

• Tau cleavage: Caspase-7 cleaves tau protein, generating toxic fragments that may propagate pathology

• Synaptic loss: Caspase-7 activation leads to synaptic protein degradation

• PARP cleavage: Excessive caspase-7 activation causes PARP cleavage, leading to energy depletion and cell death

Parkinson’s Disease

In PD, caspase-7 mediates dopaminergic neuron loss:

• Mitochondrial dysfunction: Mitochondrial toxins activate caspase-7

• Alpha-synuclein toxicity: Caspase-7 is activated by alpha-synuclein aggregates

• Neuroinflammation: Glial activation triggers caspase-7 in neighboring neurons

Amyotrophic Lateral Sclerosis

Caspase-7 contributes to motor neuron degeneration in ALS:

• Mutant SOD1 toxicity: Caspase-7 is activated in ALS models with mutant SOD1

• Excitotoxicity: Glutamate excitotoxicity triggers caspase-7 activation

• Axonal degeneration: Caspase-7 mediates axonal breakdown

Stroke and Traumatic Brain Injury

Caspase-7 activation following ischemia or trauma contributes to secondary neuronal damage.

Therapeutic Targeting

Caspase-7 is a therapeutic target for neurodegenerative diseases:

• Caspase inhibitors: Pan-caspase and caspase-7-selective inhibitors have been developed

• Neuroprotective strategies: Targeting upstream activators to prevent caspase-7 activation

• Peptide-based inhibitors: DEVD-based peptides can block caspase-7 activity

• Challenges: Broad caspase inhibition affects vital cellular functions

Key Publications

1. Wei et al., Caspase structure and function (2003)

2. Miller et al., Caspase-7 cleavage in Alzheimer’s disease (2000)

3. Burguillos et al., Caspase signalling controls microglia activation (2011)

4. LeBlanc, Caspase-6 in neurodegeneration (2003)

5. Gao et al., Caspase-7 activation in Parkinson’s disease (2005)

See Also

• CASP7 Gene

• Caspase-3 - Related executioner caspase

• Caspase-9 - Initiator caspase in intrinsic apoptosis

• Apoptosis Pathways - Cellular apoptosis mechanisms

• Alzheimer’s Disease - AD overview

• Parkinson’s Disease - PD overview

External Links

• UniProt: P55210

• PDB structures

• GeneCards: CASP7