DHHC5-mediated palmitoylation of S1P receptor subtype 1 determines G-protein coupling.

Sphingosine 1-phosphate (S1P) is a pleiotropic lipid mediator involved in the regulation of immune cell trafficking and vascular permeability acting mainly through G-protein-coupled S1P receptors (S1PRs). However, mechanism underlying how S1PRs are coupled with G-proteins remains unknown. Here we have uncovered that palmitoylation of a prototypical subtype S1PR is prerequisite for subsequent inhibitory G-protein (Gi) coupling. We have identified DHHC5 as an enzyme for palmitoylation of S1PR. Under basal conditions, S1PR was functionally associated with DHHC5 in the plasma membranes (PM) and was fully palmitoylated, enabling Gi coupling. Upon stimulation, the receptor underwent internalisation leaving DHHC5 in PM, resulting in depalmitoylation of S1PR. We also revealed that while physiological agonist S1P-induced endocytosed S1PR readily recycled back to PM, pharmacological FTY720-P-induced endocytosed S1PR-positive vesicles became associated with DHHC5 in the later phase, persistently transmitting Gi signals there. This indicates that FTY720-P switches off the S1P signal in PM, while switching on its signal continuously inside the cells. We propose that DHHC5-mediated palmitoylation of S1PR determines Gi coupling and its signalling in a spatio/temporal manner.