COP9 signalosome complex subunit 8

COP9 signalosome complex subunit 8 (COPS8, also known as SGN8) is a 209-amino acid component of the COP9 signalosome (CSN), a multi-subunit complex that regulates ubiquitin-dependent protein degradation and cellular signaling (UniProt: Q99627). COPS8 functions as part of the CSN by mediating deneddylation of cullin subunits within SCF-type E3 ligase complexes, thereby modulating ubiquitin ligase activity. The complex additionally phosphorylates key signaling proteins including p53, c-jun, and IκBα, often in conjunction with kinases such as CK2 and PKD.

The CSN complex is implicated in developmental processes and cellular regulation across multiple tissues. No inherent disease phenotype is reported in the UniProt record, though dysregulation of the ubiquitin-proteasome system is a hallmark of neurodegenerative pathology.

COPS8 is upregulated in Alzheimer's Disease brain tissue relative to age-matched controls (Chaparral AD proteomics). Analysis of post-mortem AD brain samples using quantitative proteomics detected COPS8 elevation with a mean log2 fold-change of 0.85 across subcellular fractions, suggesting increased protein abundance in the disease state. This upregulation may reflect compensatory activation or altered protein quality control mechanisms in AD neurodegeneration.