Metabotropic Glutamate Receptor 5 Is a Disulfide-linked Dimer

doi:10.1074/jbc.271.45.28612

Metabotropic Glutamate Receptor 5 Is a Disulfide-linked Dimer*

From the Departments of ^‡ Ophthalmology and Visual Sciences and
^§ Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110

^¶ To whom correspondence should be addressed:
Dept. of Ophthalmology and Visual Sciences, Washington University School of Medicine, 660 South Euclid Ave., St. Louis, MO 63110
. Tel.: 314-362-2676; Fax: 314-362-3638; E-mail: romano{at}am.seer.wustl.edu.

Abstract

The sequences of the metabotropic glutamate receptors (mGluRs) show little homology with other members of the G protein-coupled receptor family and exhibit several distinctive features, including a large N-terminal extracellular domain with 17 cysteines in conserved positions. Here we demonstrate that mGluR5, as well as other mGluRs, behave as species approximately twice as large as expected from their sequence, but reducing conditions cause a decrease to the predicted molecular mass. Co-immunoprecipitation experiments using wild type and epitope-tagged receptors demonstrate that this is due to specific, disulfide-dependent dimerization of the receptor. The intermolecular disulfide that mediates dimerization occurs in the extracellular domain, within about 17 kDa from the N terminus.

Footnotes

↵* This work was supported in part by National Institutes of Health Grants AG11355, EY02687, EY09370, an unrestricted grant from Research to Prevent Blindness, and the McDonnell Center for Cellular and Molecular Neuroscience. 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.
↵¹ The abbreviations used are:

iGluR

ionotropic glutamate receptor

mGluR

metabotropic glutamate receptor

wt

wild type

HA

hemagglutinin

tHA

truncated HA

PBS

phosphate-buffered saline

DTT

dithiothreitol

PBP

periplasmic binding protein.
↵² C. Romano, I. Saito, and K. L. O'Malley, unpublished observation.
- Received August 16, 1996.