COP9 signalosome complex subunit 4

COPS4 encodes the COP9 signalosome complex subunit 4 (SGN4), a component of the COP9 signalosome (CSN), a multi-subunit complex that regulates ubiquitin conjugation and protein degradation. The CSN mediates deneddylation of cullin subunits in E3 ligase complexes and participates in phosphorylation of key signaling proteins including p53, c-jun, and IκBα, modulating their stability and activity (UniProt: Q9BT78).

The protein functions broadly in cellular regulation across tissues with roles in ubiquitin-proteasome signaling and transcriptional control. No specific tissue localization or non-AD disease associations are documented in UniProt for COPS4.

COPS4 is associated with Alzheimer's Disease in this dataset. However, proteomic evidence from post-mortem AD brain versus age-matched controls shows ambiguous direction of change across the four subcellular fractions examined (P2, P3, S2, S3), with a mean log2 fold-change of 0.06 (Chaparral AD proteomics). This near-zero average suggests COPS4 abundance is largely preserved in AD brain tissue, though expression may vary by subcellular compartment.