Localization of the Dopamine D2 Receptor in Lipid Raft Microdomains: Implications for Receptor Function

Abstract

The dopamine receptors are a subclass of G protein‐coupled receptors (GPCRs), including the D1‐like and D2‐like receptors, which have been implicated in working memory, motivation/reward, and motor activity. Antagonists to the D2‐like receptors inhibit the psychotic symptoms associated with schizophrenia and block the motor stimulant and rewarding properties of drugs of abuse. Accordingly, the molecular underpinnings of signaling through the D2‐like receptors are of great clinical interest. In the present study we sought to investigate the role of lipid raft microdomains in D2 receptor (D2R) function. Lipid rafts are regions of the plasma membrane enriched in glycosphingolipids and cholesterol, and have been implicated widely in the regulation of GPCR signaling. We demonstrate through sucrose gradient fractionation and indirect immunofluorescence that D2Rs co‐localize with markers for lipid rafts in HEK293 cells. We also show that endogenous D2R from striatal membranes localize within lipid rafts. We report that depletion of cholesterol with methyl‐beta‐cyclodextrin (MCD), an agent well characterized to disrupt lipid rafts, significantly impairs D2R‐mediated inhibition of cAMP production in HEK293 cells. The results of these studies demonstrate that the localization of D2Rs in lipid rafts regulates D2R‐induced activation of its cognate G proteins.