S-Palmitoylation of a Novel Site in the β2-Adrenergic Receptor Associated with a Novel Intracellular Itinerary

We report here that a population of human (2)-adrenergic receptors ((2)AR), a canonical G protein-coupled receptor, traffics along a previously undescribed intracellular itinerary via the Golgi complex that is associated with the sequential S-palmitoylation and depalmitoylation of a previously undescribed site of modification, Cys-265 within the third intracellular loop. Basal S-palmitoylation of Cys-265 is negligible, but agonist-induced (2)AR activation results in enhanced S-palmitoylation, which requires phosphorylation by the cAMP-dependent protein kinase of Ser-261/Ser-262. Agonist-induced turnover of palmitate occurs predominantly on Cys-265. Cys-265 S-palmitoylation is mediated by the Golgi-resident palmitoyl transferases zDHHC9/14/18 and is followed by depalmitoylation by the plasma membrane-localized acyl-protein thioesterase APT1. Inhibition of depalmitoylation reveals that S-palmitoylation of Cys-265 may stabilize the receptor at the plasma membrane. In addition, (2)AR S-palmitoylated at Cys-265 are selectively preserved under a sustained adrenergic stimulation, which results in the down-regulation and degradation of AR. Cys-265 is not conserved in (1)AR, and S-palmitoylation of Cys-265 may thus be associated with functional differences between (2)AR and (1)AR, including relative resistance of (2)AR to down-regulation in multiple pathophysiologies. Trafficking via the Golgi complex may underlie new roles in G protein-coupled receptor biology.