Caspase 8 (Casp8) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Caspase 8 (CASP8) is an initiator caspase that plays a central role in the extrinsic (death receptor-mediated) apoptotic pathway. It is encoded by the CASP8 gene located on chromosome 2q33-q34 and is essential for transducing death signals from cell surface receptors to the intracellular apoptotic machinery.
| Caspase 8 | |
|---|---|
| Gene Symbol | CASP8 |
| Full Name | Caspase 8 |
| Chromosome | 2q33-q34 |
| NCBI Gene ID | 841 |
| OMIM | 601763 |
| Ensembl ID | ENSG00000164040 |
| UniProt ID | Q14790 |
Caspase-8 exists as an inactive zymogen (procaspase-8) in the cytoplasm. Upon engagement of death receptors (Fas/CD95, TRAIL-R1/R2, TNFR1), the adapter protein FADD (Fas-associated via death domain) recruits procaspase-8 to form the death-inducing signaling complex (DISC)[1].
Activation occurs through dimerization-induced autoproteolysis, generating the active heterotetrameric caspase-8 (p18/p10) complex. Active caspase-8 then cleaves and activates downstream executioner caspases (caspase-3, -6, -7), leading to apoptotic cell death[2].
Caspase-8 also has important non-apoptotic roles:
In Alzheimer's disease, caspase-8 is activated in response to amyloid-beta (Aβ) toxicity. Aβ oligomers induce caspase-8 activation through the extrinsic apoptotic pathway, contributing to synaptic loss and neuronal death. Studies show elevated caspase-8 levels in AD brain tissue[4]. Caspase-8 also cleaves tau protein, generating truncated tau fragments that may promote neurofibrillary tangle formation[5].
In Parkinson's disease, caspase-8 mediates dopaminergic neuron death triggered by:
Caspase-8 is critically involved in ischemic brain injury. Following cerebral ischemia, TNF-α and Fas ligand are upregulated, activating caspase-8 and the extrinsic apoptotic pathway. Caspase-8 inhibitors have shown neuroprotective effects in experimental stroke models[7].
Following TBI, caspase-8 mediates both acute neuronal death and delayed secondary injury processes. The extrinsic pathway contributes to contusion expansion and neuroinflammation.
Caspase-8 represents a potential therapeutic target for neurodegenerative disorders:
| Agent | Mechanism | Status | Disease |
|---|---|---|---|
| Z-IETD-FMK | Caspase-8 inhibitor | Preclinical | Stroke, TBI |
| CASP8 siRNA | Gene silencing | Research | AD, PD |
| Ac-DEVD-CHO | Caspase-3/8 inhibitor | Research | Neuroprotection |
Challenges: Systemic caspase inhibition may have adverse effects on immune function and embryonic development. Localized delivery approaches are being explored.
| Disease | Role | Evidence |
|---|---|---|
| Alzheimer's Disease | Neuronal apoptosis | Elevated caspase-8 in AD brain[4] |
| Parkinson's Disease | Dopaminergic neuron death | Activated in PD models[6] |
| Stroke | Ischemic injury | Mediates reperfusion injury[7] |
| Traumatic Brain Injury | Secondary damage | Elevated post-TBI |
| ALS | Motor neuron death | Activated in ALS models |
CASP8 is expressed in multiple brain regions:
Expression is upregulated in response to neuroinflammatory signals and cellular stress.
[1] Kischkel FC, et al. Cytotoxicity-dependent APO-1 (Fas/CD95)-associated proteins form a death-inducing signaling complex (DISC) with the receptor. EMBO J. 1995.
[2] Boatright KM, et al. A unified model for apical caspase activation. Mol Cell. 2003.
[3] Su H, et al. NF-κB requirement for B cell survival and plasma cell generation. J Immunol. 2005.
[4] Rohn TT, et al. Caspase activation in Alzheimer's disease. J Neurosci Res. 2001.
[5] Rissman RA, et al. Caspase-cleavage of tau is an early event in Alzheimer disease. J Clin Invest. 2004.
[6] Tatton NA. Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson's disease. Exp Neurol. 2000.
[7] Martin-Villalba A, et al. Therapeutic inhibition of caspase-8 reduces injury after stroke. Nat Med. 1999.
The study of Caspase 8 (Casp8) 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.
[1] Kischkel FC, et al. Cytotoxicity-dependent APO-1 (Fas/CD95)-associated proteins form a death-inducing signaling complex (DISC) with the receptor. EMBO J. 1995;14(22):5579-5588.
[2] Boatright KM, et al. A unified model for apical caspase activation. Mol Cell. 2003;11(3):529-541.
[3] Su H, et al. NF-κB requirement for B cell survival and plasma cell generation. J Immunol. 2005;175(9):6134-6142.
[4] Rohn TT, et al. Caspase activation in Alzheimer's disease. J Neurosci Res. 2001;66(4):573-582.
[5] Rissman RA, et al. Caspase-cleavage of tau is an early event in Alzheimer disease. J Clin Invest. 2004;114(1):121-130.
[6] Tatton NA. Increased caspase 3 and Bax immunoreactivity accompany nuclear GAPDH translocation and neuronal apoptosis in Parkinson's disease. Exp Neurol. 2000;166(1):29-43.
[7] Martin-Villalba A, et al. Therapeutic inhibition of caspase-8 reduces injury after stroke. Nat Med. 1999;5(5):554-559.