Identification of G Protein α Subunit-Palmitoylating Enzyme

The heterotrimeric G protein alpha subunit (G alpha) is targeted to the cytoplasmic face of the plasma membrane through reversible lipid palmitoylation and relays signals from G-protein-coupled receptors (GPCRs) to its effectors. By screening 23 DHHC motif (Asp-His-His-Cys) palmitoyl acyl-transferases, we identified DHHC3 and DHHC7 as G alpha palmitoylating enzymes. DHHC3 and DHHC7 robustly palmitoylated G alpha(q), G alpha(s), and G alpha(i2) in HEK293T cells. Knockdown of DHHC3 and DHHC7 decreased G alpha(q/11) palmitoylation and relocalized it from the plasma membrane into the cytoplasm. Photoconversion analysis revealed that G alpha(q) rapidly shuttles between the plasma membrane and the Golgi apparatus, where DHHC3 specifically localizes. Fluorescence recovery after photobleaching studies showed that DHHC3 and DHHC7 are necessary for this continuous G alpha(q) shuttling. Furthermore, DHHC3 and DHHC7 knockdown blocked the alpha(1A)-adrenergic receptor/G alpha(q/11)-mediated signaling pathway. Together, our findings revealed that DHHC3 and DHHC7 regulate GPCR-mediated signal transduction by controlling G alpha localization to the plasma membrane.