COPS8 also known as CSN8 is one of the eight subunits of COP9 signalosome, a highly conserved protein complex that functions as an important regulator in multiple signaling pathways. COPS8 is a core subunit of the COP9 signalosome that regulates cullin-RING E3 ubiquitin ligases by controlling cullin neddylation status and thereby influencing ubiquitin-dependent protein turnover. Through this activity, CSN8 contributes to proteostasis, cell-cycle progression, DNA damage responses, and stress-adaptive signaling by modulating the stability of key regulatory proteins. COPS8′s importance lies not only in its structural role within the complex but also in its involvement in the phosphorylation of key proteins such as p53, c-Jun, IκBα, and IRF-8. These phosphorylation events are critical for regulating cellular responses to stress and maintaining protein homeostasis, as they can either promote degradation or protect proteins from degradation by the ubiquitin-proteasome system.