| Gene | [XIAP](/genes/xiap) |
| UniProt ID | [P98170](https://www.uniprot.org/uniprot/P98170) |
| PDB Structures | [1G3F](https://www.rcsb.org/structure/1G3F), [1I4O](https://www.rcsb.org/structure/1I4O) |
| Molecular Weight | 56.6 kDa |
| Amino Acids | 497 |
| Subcellular Location | Cytosol |
| Protein Family | IAP family (BIR domain) |
X-linked Inhibitor of Apoptosis Protein (XIAP), encoded by the XIAP gene on chromosome Xq25, is the most potent endogenous inhibitor of caspases and a key regulator of programmed cell death[1]. As a member of the inhibitor of apoptosis (IAP) protein family, XIAP contains baculoviral IAP repeat (BIR) domains that directly bind and inhibit caspases-3, -7, and -9, making it a critical determinant of cell survival under stress conditions[2].
In the nervous system, XIAP expression protects neurons from various apoptotic stimuli including oxidative stress, excitotoxicity, and protein aggregation[3]. Dysregulation of XIAP has been implicated in neurodegenerative diseases, where insufficient XIAP activity contributes to neuronal loss, while excessive XIAP may impair clearance of damaged cells[4].
XIAP is composed of three N-terminal BIR domains and a C-terminal RING finger domain[5]:
XIAP blocks the intrinsic apoptotic pathway through direct caspase inhibition[6]:
In neurons, XIAP provides survival advantages[7]:
XIAP modulates neuroinflammation via[8]:
XIAP has complex roles in AD[9]:
XIAP protects dopaminergic neurons[10]:
In HD models[11]:
XIAP affects motor neuron survival[12]:
XIAP upregulation is protective in SMA[13]:
SMAC mimetics displace caspases from XIAP to promote apoptosis[14]:
Approaches to boost XIAP neuroprotection[15]:
Key considerations for XIAP modulation[16]:
| Interactor | Function | Disease Relevance |
|---|---|---|
| Caspase-3 | Inhibition | Apoptosis |
| Caspase-7 | Inhibition | Apoptosis |
| Caspase-9 | Inhibition | Intrinsic apoptosis |
| SMAC/DIABLO | Antagonist | Apoptosis regulation |
| TAB1 | NF-κB activation | Inflammation |
| TAK1 | Kinase signaling | Inflammation |
| NOD2 | Bacterial sensing | Innate immunity |
| cIAP1/cIAP2 | Heterodimerization | IAP regulation |
XIAP is the most potent endogenous caspase inhibitor, playing a crucial role in regulating neuronal survival and death. Its ability to directly inhibit caspases-3, -7, and -9 makes it a key determinant of cellular fate under stress conditions. While XIAP overexpression can protect neurons in neurodegenerative disease models, the therapeutic window is complex due to its inflammatory functions and the need to balance neuroprotection with appropriate removal of damaged cells.
Deveraux QL, Reed JC. IAP family proteins—suppressors of apoptosis. Genes & Development. 1999. ↩︎
Salvesen GS, Duckett CS. IAP proteins: blocking the road to death's door. Nature Reviews Molecular Cell Biology. 2002. ↩︎
Liston P, Fong WG, Korneluk RG. The inhibitors of apoptosis: there is more to life than Bcl2. Oncogene. 2003. ↩︎
Galban S, Duckett CS. XIAP as a ubiquitin ligase in cellular signaling. Cell Death and Differentiation. 2010. ↩︎
Chai J, Shiozaki E, Srinivasula SM, et al. [Structural basis of caspase-7 inhibition by XIAP](https://doi.org/10.1016/S0092-8674(01). Cell. 2001. ↩︎
Riedl SJ, Renatus M, Schwarzenbacher R, et al. [Structural basis for the inhibition of caspase-3 by XIAP](https://doi.org/10.1016/S0092-8674(01). Cell. 2001. ↩︎
Perrelet D, Ferri A, MacKenzie AE, et al. XIAP overexpression in motor neurons in vivo is protective against excitotoxicity. Neurobiology of Disease. 2004. ↩︎
Krieg A, Correa RG, Garrison JB, et al. XIAP mediates NOD signaling via interaction with RIP2. PNAS. 2009. ↩︎
Schubert D. The potentiation of proteotoxic stress as a novel therapeutic approach for treating Alzheimer's disease. Advances in Pharmacology. 2012. ↩︎
Eberhardt O, Coelln RV, Kugler S, et al. Protection by synergistic effects of adenovirus-mediated X-chromosome-linked inhibitor of apoptosis and glial cell line-derived neurotrophic factor gene transfer in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of Parkinson's disease. Journal of Neuroscience. 2000. ↩︎
Hermel E, Gafni J, Propp SS, et al. Specific caspase interactions and amplification are involved in selective neuronal vulnerability in Huntington's disease. Cell Death and Differentiation. 2004. ↩︎
Inoue H, Tsukita K, Iwasato T, et al. The crucial role of caspase-9 in the disease progression of a transgenic ALS mouse model. EMBO Journal. 2003. ↩︎
Azzouz M, Le T, Ralph GS, et al. Lentivector-mediated SMN replacement in a mouse model of spinal muscular atrophy. Journal of Clinical Investigation. 2004. ↩︎
Fulda S, Vucic D. Targeting IAP proteins for therapeutic intervention in cancer. Nature Reviews Drug Discovery. 2012. ↩︎
Siegel RM. Caspases at the crossroads of immune-cell life and death. Nature Reviews Immunology. 2006. ↩︎
Gyrd-Hansen M, Meier P. IAPs: from caspase inhibitors to modulators of NF-κB, inflammation and cancer. Nature Reviews Cancer. 2010. ↩︎