The role of acyl cycling in endogenous G protein localization.

Monomeric and heterotrimeric G proteins associate with membranes in part due to S-acylation, most often the reversible addition of palmitate (C16). An ongoing cycle of deacylation, shuttling through the cytosol and reacylation, is known to be important for the steady-state enrichment of monomeric G proteins at the plasma membrane, but it is not known whether heterotrimeric G proteins are similarly regulated. Here we study how deacylation and reacylation affect the subcellular distribution of endogenous heterotrimeric G proteins and compare this to endogenous HRas. Pharmacological inhibition of palmitoyl transferase (PAT) enzymes had almost no effect on the subcellular distribution of endogenous heterotrimers but redistributed endogenous HRas from the plasma membrane to intracellular membranes. Similarly, redirecting PAT enzymes to the outer nuclear membrane trapped a large fraction of endogenous HRas in this compartment, whereas endogenous heterotrimers were only minimally affected. Our results suggest that acyl cycling is not important for the steady-state subcellular distribution of heterotrimeric G proteins, and that heterotrimers do not have ready access to intracellular membrane compartments through the cytosol.