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Agonist-induced endocytosis and receptor phosphorylation mediate resensitization of dopamine D(2) receptors.

Authors
  • Cho, Dongim1
  • Zheng, Mei
  • Min, Chengchun
  • Ma, Lan
  • Kurose, Hitoshi
  • Park, Jae H
  • Kim, Kyeong-Man
  • 1 Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwang-Ju 500-757, Korea. , (North Korea)
Type
Published Article
Journal
Molecular Endocrinology
Publisher
The Endocrine Society
Publication Date
Mar 01, 2010
Volume
24
Issue
3
Pages
574–586
Identifiers
DOI: 10.1210/me.2009-0369
PMID: 20160122
Source
Medline
Language
English
License
Unknown

Abstract

The regulatory mechanisms and functional roles of agonist-induced internalization of G protein-coupled receptors (GPCRs) were analyzed using mutant dopamine D(2) receptors (D(2)Rs) in which all possible GPCR kinase (GRK) phosphorylation sites were mutated or the affinity for beta-arrestins was altered. Agonist-induced internalization of D(2)Rs involved a phosphorylation-dependent component, which was mediated by serine/threonine (S/T) residues in the second loop and T225 in the third loop, and a phosphorylation-independent component. GRK2-mediated enhancement of the internalization and inhibition of D(2)R signaling did not involve receptor phosphorylation, and only the former required the enzymatic activity of GRK2. The phosphorylation-deficient mutant (D(2)R-intracellular loop 2/3) recycled more slowly and showed more agonist-induced desensitization than did the wild-type D(2)R, suggesting that receptor phosphorylation mediates the recycling of the internalized receptors and enhances receptor resensitization. Blockade of the agonist-induced internalization of D(2)R-intracellular loop 2/3 provoked desensitization as in wild-type D(2)R, suggesting that certain cellular processes other than receptor dephosphorylation occurring within the endocytic vesicle are responsible for the resensitization of D(2)R. When dissociation between D(2)R and beta-arrestin was inhibited or when the expression of cellular beta-arrestins was decreased, agonist-induced desensitization of D(2)R did not occur, suggesting that dissociation from beta-arrestin is the main cellular process required for resensitization of D(2)R and is achieved through agonist-induced internalization. These results indicate that, in the regulation of some GPCRs, phosphorylation-independent association with beta-arrestin plays a major role in agonist-induced desensitization.

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