Apparent Loss-of-Function Mutant GPCRs Revealed as Constitutively Desensitized Receptors

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• 作者：Alyson M. Wilbanks ; Sté ; phane A. Laporte ; Laura M. Bohn ; Larry S. Barak ; and Marc G. Caron
• 刊名：Biochemistry
• 出版年：2002
• 出版时间：October 8, 2002
• 年：2002
• 卷：41
• 期：40
• 页码：11981 - 11989
• 全文大小：490K
• 年卷期：v.41,no.40(October 8, 2002)
• ISSN：1520-4995

文摘

The DRY motif is a triplet amino acid sequence (aspartic acid, arginine, and tyrosine) that ishighly conserved in G protein-coupled receptors (GPCRs). Recently, we have shown that a moleculardeterminant for nephrogenic diabetes insipidus, the vasopressin receptor with a substitution at the DRYmotif arginine (V2R R137H), is a constitutively desensitized receptor that is unable to couple to G proteinsdue to its constitutive association with s/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-arrestin [Barak, L. S. (2001) Proc. Natl. Acad. Sci. U.S.A. 98,93-98]. Additionally, the mutant receptors are localized in endocytic vesicles, identical to wild-typereceptors stimulated with agonist. In this study, we asked whether the constitutively desensitized phenotypeobserved in the V2R R137H represents a general paradigm that may be extended to other GPCRs. Weshow that arginine substitutions in the DRY motifs of the s/gifchars/alpha.gif" BORDER=0>_1B adrenergic receptor (s/gifchars/alpha.gif" BORDER=0>_1B-AR) and angiotensinII type 1A receptor (AT_1AR) result in receptors that are uncoupled from G proteins, associated withs/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-arrestins, and found localized in endocytic vesicles rather than at the plasma membrane in the absenceof agonists. The localization of the s/gifchars/alpha.gif" BORDER=0>_1B-ARs and AT_1ARs with arginine substitutions can be restored tothe plasma membrane by either using selective antagonists or preventing the endocytosis of the s/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-arrestin-receptor complexes. These results indicate that the arginine residue of the DRY motif is essential forpreserving the localization of the inactive receptor complex. Furthermore, constitutive desensitizationmay underlie some loss-of-function receptor phenotypes and represent an unappreciated mechanism ofhormonal resistance.