DHHC protein‐dependent palmitoylation protects regulator of G‐protein signaling 4 from proteasome degradation

Regulator of G‐protein signaling 4 (RGS4), an intracellular modulator of G‐protein coupled receptor (GPCR)‐mediated signaling, is regulated by multiple processes including palmitoylation and proteasome degradation. In the present study, we confirmed that RGS4 protein levels are regulated by the N‐end rule for proteasomal degradation via a Cys2‐dependent oxidation of RGS4. Western blot analysis showed that co‐expression of DHHC motif (Asp‐His‐His‐Cys) acyltransferases (DHHC3 or DHHC7), but not their acyltransferase‐inactive mutants, increased expression levels of wild‐type RGS4 but not its Cys2 to Ser mutant (RGS4C2S). Co‐immunoprecipitation assays demonstrated that DHHC3 interacts with and palmitoylates RGS4 but not RGS4C2S in vivo . A cycloheximide‐chase assay indicated that palmitoylation interferes with oxidation‐dependent degradation, thus prolonging the half‐life of RGS4 by over 8‐fold. More importantly, palmitoylated RGS4 blocked α 1A ‐adrenergic receptor‐stimulated intracellular Ca 2+ mobilization. Together, our findings revealed that DHHC proteins could regulate GPCR‐mediated signaling by increasing RGS4 stability. Supported by National Institute of Health (R011CA125661), Nebraska State LB595, National Basic Research Program of China (2004CB720000) and the National Natural Science Foundation of China (30900246).