COPS5 Protein, Human

The COPS5 protein serves as the probable protease subunit within the COP9 signalosome complex (CSN), a vital regulator involved in diverse cellular and developmental processes. Operating as a crucial component of the CSN complex, COPS5 plays a central role in the regulation of the ubiquitin conjugation pathway by facilitating the deneddylation of the cullin subunits within SCF-type E3 ligase complexes. This deneddylation activity results in the reduction of Ubl ligase activity, impacting complexes such as SCF, CSA, or DDB2. Moreover, the CSN complex, in association with CK2 and PKD kinases, is implicated in the phosphorylation of various substrates, including p53/TP53, c-jun/JUN, IkappaBalpha/NFKBIA, ITPK1, and IRF8. COPS5 likely functions as the catalytic center mediating the cleavage of Nedd8 from cullins within the complex, thereby influencing the regulatory landscape of protein degradation. Its direct interaction with numerous proteins regulated by the CSN complex underscores its key role in mediating cellular processes and highlights its involvement in the proteasomal degradation of BRSK2.