Individual S-acylated cysteines differentially contribute to H-Ras endomembrane traffcking and acylation/deacylation cycles

Abstract

S-acylation/deacylation cycles and vesicular transport are critical for an adequate subcellular distribution of S-acylated Ras proteins. H-Ras is dually acylated on cysteines 181 and 184, but it is unknown how these residues individually contribute to H-Ras traffcking. In this study, we characterized the acylation and deacylation rates and membrane traffcking of monoacylated H-Ras mutants to analyze their contributions to H-Ras plasma membrane and endomembrane distribution. We demonstrated that dually acylated H-Ras interacts with acylprotein thioesterases (APTs) 1 and 2 at the plasma membrane. Moreover, single-acylation mutants of H-Ras differed not only in their subcellular distribution, where both proteins localized to different extents at both the Golgi complex and plasma membrane, but also in their deacylation rates, which we showed to be due to different sensitivities to APT1 and APT2. Fluorescence photobleaching and photoactivation experiments also revealed that 1) although S-acylated, single-acylation mutants are incorporated with different effciencies into Golgi complex to plasma membrane vesicular carriers, and 2) the different deacylation rates of single-acylated H-Ras influence differentially its overall exchange between different compartments by nonvesicular transport. Taken together, our results show that individual S-acylation sites provide singular information about H-Ras subcellular distribution that is required for GTPase signaling.