Fig. 7. Model of possible interactions of KGB-1 and CSN-5 with GLH-1 in C. elegans. This model is based on data presented here, which suggest that CSN-5 protects GLH-1 from degradation. The MAPK docking site in GLH-1 is important for GLH-1/KGB-1 interactions. Kinase assays show that KGB-1 can phosphorylate GLH-1, perhaps at the conserved phosphodegron motif. In addition, GLH-1, CSN-5 and KGB-1 physically and functionally interact to allow cross-talk between CSN-5 and KGB-1, with CSN-5 antagonizing KGB-1 function and protecting GLH-1. While interacting with KGB-1 and GLH-1, CSN-5 might associate with the COP9 signalosome.