N-linked Glycosylation on the N-terminus of the dopamine D-2 and D-3 receptors determines receptor association with specific microdomains in the plasma membrane

摘要

Numerous G protein-coupled receptors (GPCRs) are glycosylated at extracellular regions. The regulatory roles of glycosylation on receptor function vary across receptor types. In this study, we used the dopamine D-2 and D-3 receptors as an experimental model to understand the underlying principles governing the functional roles of glycosylation. We used the pharmacological inhibitor, tunicamycin, to inhibit glycosylation, generated chimeric D-2 and D-3 receptors by swapping their respective N-termini, and produced the glycosylation site mutant D-2 and D-3 receptors to study the roles of glycosylation on receptor functions, including cell surface expression, signaling, and internalization through specific microdomains. Our results demonstrate that glycosylation on the N-terminus of the D-3 receptor is involved in the development of desensitization and proper cell surface expression. In addition, glycosylation on the N-terminus mediates the internalization of D-2 and D-3 receptors within the caveolae and clathrin-coated pit microdomains of the plasma membrane, respectively, by regulating receptor interactions with caveolin-1 and clathrin. In conclusion, this study shows for the first time that glycosylation on the N-terminus of GPCRs is involved in endocytic pathway selection through specific microdomains. These data suggest that changes in the cellular environment that influence posttranslational modification could be an important determinant of intracellular GPCR trafficking. (C) 2014 Elsevier B.V. All rights reserved.