C-Terminal Di-leucine Motif of Dopamine D1 Receptor Plays an Important Role in Its Plasma Membrane Trafficking

摘要

The dopamine D1 receptor (D1R), 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 D1R that were tagged with or without enhanced yellow fluorescent protein, and analyzed the consequences of these mutants on the plasma membrane trafficking of D1R and cyclic AMP response to D1R stimulation. D1R with mutations within the endocytic recycling signal (amino acid residues 360–382) continued to be functional, albeit decreased relative to wild-type D1R. Mutation of the palmitoylation site (347C>S) of D1R 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 D1R 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 D1R is critical for the glycosylation and cell surface targeting of D1R.