COP9 signalosome complex subunit 3

COP9 signalosome complex subunit 3 (COPS3) is a 423-amino acid component of the COP9 signalosome (CSN), a multi-protein complex that regulates ubiquitin-mediated protein degradation (UniProt: Q9UNS2). The CSN complex mediates deneddylation of cullin subunits in SCF-type E3 ligase complexes, thereby modulating their activity. COPS3 also participates in phosphorylation of regulatory proteins including p53, c-jun, IκBα, and IRF8, potentially acting through association with CK2 and PKD kinases.

The protein functions in cellular and developmental processes linked to ubiquitin conjugation and protein quality control pathways central to neuronal homeostasis. No specific tissue-restricted expression or non-disease phenotypes are documented in the UniProt record.

COPS3 is upregulated in Alzheimer's disease brain tissue. In a comparative proteomics study of human post-mortem AD brain versus age-matched controls using TMT-labeled quantitative mass spectrometry across subcellular fractions, COPS3 showed increased abundance with a mean log2 fold-change of 0.78 (Chaparral AD proteomics). This elevation may reflect altered proteasomal degradation capacity or compensatory responses to protein misfolding characteristic of AD pathology.