GPS1 (G protein pathway suppressor 1) is an essential component of the COP9 signalosome (CSN) complex that regulates protein degradation pathways and cellular signaling 1. As part of the CSN, GPS1 mediates deneddylation of cullin subunits in E3 ligase complexes, thereby modulating ubiquitin-mediated protein degradation 1. The protein plays crucial roles in JNK signaling pathway regulation, where it enhances c-Jun NH2-terminal kinase activity and can be inhibited by interacting proteins like Asb-4 2. GPS1 also activates NF-κB signaling, which promotes influenza virus polymerase activity and viral replication 3. In cancer contexts, GPS1 expression is significantly elevated in breast cancer tissues compared to normal tissue, correlating with worse prognosis in certain breast cancer subtypes 4. The protein contributes to cancer progression through multiple mechanisms, including enhancement of cell proliferation, invasion, and migration 4. Additionally, GPS1 shows asymmetric distribution in early mammalian embryos, influencing lineage segregation during development 5. Clinical significance includes its potential as a diagnostic biomarker in breast cancer and possible therapeutic target, while rare mutations in GPS1 exon 9 have been identified in penile squamous cell carcinoma, though their driver role remains unclear 6.