Identification of a GABAB Receptor Subunit, gb2, Required for Functional GABAB Receptor Activity*
- Gordon Y. K. NgtOaFNbFNc,
- Janet ClarkFNb,tOdFNe,
- Nathalie CoulombetOaFNb,
- Nathalie EthiertOf,
- Terence E. HeberttOf,
- Richard SullivantOa,
- Stacia KargmantOa,
- Anne ChateauneuftOa,
- Naohiro TsukamototOg,
- Terry McDonaldtOh,
- Paul Whitingi,
- Éva MezeytOj,
- Michael P. JohnsontOh,
- Qingyun LiutOh,
- Lee F. Kolakowski Jr.tOk,
- Jilly F. EvanstOh,
- Tom I. BonnertOd and
- Gary P. O’NeilltOa
- From tOaMerck Frosst Center for Therapeutic Research, Kirkland, Quebec H9H 3L1, Canada, the iMerck Sharp & Dohme Research Laboratories, Terlings Park, Harlow, Essex CM20 2QR, United Kingdom, tOgBanyu Pharmaceutical Co., Ltd., Tsukuba-shi, Ibaraki-ken 300-2611, Japan, tOhMerck & Co., Inc., West Point, Pennsylvania, 19486, tOfMontreal Heart Institute, Montreal, Quebec H1T 1C8, Canada, tOdNational Institutes of Mental Health, Section on Genetics and tOjNINDS, National Institutes of Health, Bethesda, Maryland 20892-4094, and the tOkDepartments of Pharmacology and Biochemistry, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78284
Abstract
G protein-coupled receptors are commonly thought to bind their cognate ligands and elicit functional responses primarily as monomeric receptors. In studying the recombinant γ-aminobutyric acid, type B (GABAB) receptor (gb1a) and a GABAB-like orphan receptor (gb2), we observed that both receptors are functionally inactive when expressed individually in multiple heterologous systems. Characterization of the tissue distribution of each of the receptors by in situhybridization histochemistry in rat brain revealed co-localization of gb1 and gb2 transcripts in many brain regions, suggesting the hypothesis that gb1 and gb2 may interact in vivo. In three established functional systems (inwardly rectifying K+channel currents in Xenopus oocytes, melanophore pigment aggregation, and direct cAMP measurements in HEK-293 cells), GABA mediated a functional response in cells coexpressing gb1a and gb2 but not in cells expressing either receptor individually. This GABA activity could be blocked with the GABAB receptor antagonist CGP71872. In COS-7 cells coexpressing gb1a and gb2 receptors, co-immunoprecipitation of gb1a and gb2 receptors was demonstrated, indicating that gb1a and gb2 act as subunits in the formation of a functional GABAB receptor.
Footnotes
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↵* 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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↵FNb These authors contributed equally to this work.
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↵FNc To whom correspondence should be addressed. Tel.: 514-428-3589; Fax: 514-428-4900; E-mail: gordon_ng{at}merck.com.
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↵FNe Supported by a Young Investigator Award from the National Alliance for Research on Schizophrenia and Depression.
- GABA
- γ-aminobutyric acid
- GPCR
- G protein-coupled receptor
- Kir
- inwardly rectifying K+ channel
- PCR
- polymerase chain reaction
- Received December 14, 1998.
- Revision received January 14, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
