Phosphorylation of VACM-1/Cul5 by protein kinase A regulates its neddylation and antiproliferative effect.

Expression of the VACM-1/cul5 gene in endothelial and in cancer cell lines in vitro inhibits cellular proliferation and decreases phosphorylation of MAPK. Structure-function analysis of the VACM-1 protein sequence identified consensus sites specific for phosphorylation by protein kinases A and C (PKA and PKC) and a Nedd8 protein modification site. Mutations at the PKA-specific site in VACM-1/Cul5 ((S730A)VACM-1) sequence resulted in increased cellular growth and the appearance of a Nedd8-modified VACM-1/Cul5.