A Novel Interaction between Adrenergic Receptors and the α-Subunit of Eukaryotic Initiation Factor 2B*
- From the §Nina Ireland Laboratory, Departments of Psychiatry and Cellular and Molecular Pharmacology, University of California, San Francisco, California 94143-0984 and the ‡Howard Hughes Medical Institute and ‡Division of Cardiovascular Medicine, Stanford University Medical School, Stanford, California 94305
Abstract
The α-subunit of eukaryotic initiation factor 2B (eIF-2B), a guanine nucleotide exchange protein that functions in regulation of translation, was observed to associate with the carboxyl-terminal cytoplasmic domains of the α2A- and α2B-adrenergic receptors in a yeast two-hybrid screen of a cDNA library prepared from 293 cells. This protein association was confirmed in vitro by affinity chromatography and was shown to be specific for a subset of G protein-coupled receptors, including the α2A-, α2B-, α2C-, and β2-adrenergic receptors, but not the vasopressin (V2) receptor. Association of these proteins in vivo was confirmed by specific co-immunoprecipitation of eIF-2Bα with full-length β2-adrenergic receptors expressed in transfected 293 cells and by fluorescence microscopy showing co-localization of these proteins in intact cells. Remarkably, eIF-2Bα co-localized with receptors exclusively in regions of the plasma membrane that are in contact with the extracellular medium, but failed to associate with membranes making cell-cell contacts. Overexpression of eIF-2Bα in 293 cells caused a small (∼15%) but significant enhancement of β2-adrenergic receptor-mediated activation of adenylyl cyclase, without affecting forskolin or V2receptor-mediated activation. These observations suggest a new role for a previously identified guanine nucleotide exchange protein in membrane biology and cell signaling.
Footnotes
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↵* This work was supported by the Howard Hughes Medical Institute (to B. K. K.), National Institutes of Health Grant DA00218 (to M. v. Z.), and a grant-in-aid from the American Heart Association (to M. v. Z.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ These authors contributed equally to this work
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↵‖ Recipient of a postdoctoral fellowship from the American Heart Association, California Affiliate and of a research fellowship from the Deutsche Forschungsgemeinschaft.
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↵** Supported by Postdoctoral Training Grant HL07740-05 from the National Institutes of Health.
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↵§§ To whom correspondence should be addressed: Nina Ireland Laboratory, Dept. of Psychiatry, Box 0984-IRE, University of California, San Francisco, CA 94143-0984. Tel.: 415-476-7855; Fax: 415-476-7884; E-mail: zastrow{at}itsa.ucsf.edu.
- Received March 25, 1997.
- Revision received May 2, 1997.
