C-Terminal Di-leucine Motif of Dopamine D(1) Receptor Plays an Important Role in Its Plasma Membrane Trafficking

The dopamine D(1) receptor (D(1)R), a G protein-coupled receptor, plays a critical role in regulating blood pressure through its actions on renal hemodynamics and epithelial ion transport, which are highly linked to its intracellular trafficking. In this study, we generated a series of C-terminal mutants of D(1)R that were tagged with or without enhanced yellow fluorescent protein, and analyzed the consequences of these mutants on the plasma membrane trafficking of D(1)R and cyclic AMP response to D(1)R stimulation. D(1)R with mutations within the endocytic recycling signal (amino acid residues 360–382) continued to be functional, albeit decreased relative to wild-type D(1)R. Mutation of the palmitoylation site (347C>S) of D(1)R did not impair its trafficking to the plasma membrane, but abolished its ability to increase cyclic AMP accumulation. In contrast, replacement of di-leucines (344–345L>A) by alanines resulted in the retention of D(1)R in the early endosome, decreased its glycosylation, and prevented its targeting to the plasma membrane. Our studies suggest that di-L motif at the C-terminus of D(1)R is critical for the glycosylation and cell surface targeting of D(1)R.