Activation of metabotropic glutamate receptor 1 dimers requires glutamate binding in both subunits.

Title

Activation of metabotropic glutamate receptor 1 dimers requires glutamate binding in both subunits.

Creator

Kammermeier Paul J; Yun June

Publisher

The Journal of pharmacology and experimental therapeutics

Date

2005
2005-02

Description

Group I metabotropic glutamate receptors (mGluRs) form stable, disulfide-linked homodimers. Lack of a verifiably monomeric mGluR1 mutant has led to difficulty in assessing the role of dimerization in the molecular mechanism of mGluR1 activation. The related GABA(B) receptor exhibits striking intradimer cross talk (ligand binding at one subunit effectively produces G protein activation at the other), but it is unclear whether group I mGluRs exhibit analogous cross talk. Signaling of heterologously expressed mGluR1 was examined in isolated rat sympathetic neurons by measuring glutamate-mediated inhibition of native calcium currents. To examine mGluR1 activity when only one dimer subunit has access to glutamate ligand, wildtype mGluR1 was coexpressed with mGluR1 Y74A, a mutant with impaired glutamate binding, and the activity of the heterodimer (mutant/wild type) was examined. The mGluR1 Y74A mutant alone had a dose-response curve that was shifted by about 2 orders of magnitude. The half-maximal dose of glutamate shifted from 1.3 (wild-type mGluR1) to about 450 (mGluR1 Y74A) microM. However, the maximal effect was similar. Wild-type mGluR1 was expressed with excess Y74A mGluR1 to generate a receptor population consisting largely of mutant homodimers and mutant/wild-type heterodimers but without detectable wild-type homodimers. Under these conditions, no glutamate-mediated calcium current inhibition was observed below approximately 300 microM glutamate, although wild-type mGluR1 protein was detectable with immunofluorescence. These data suggest that mutant/wild-type heterodimeric receptors are inactive at ligand concentrations favoring glutamate association with receptor dimers at only one subunit.

Subject

Blotting; Calcium Channels/drug effects/metabolism; DNA/biosynthesis/genetics; Dose-Response Relationship; Drug; Fluorescent Antibody Technique; Genes; Glutamic Acid/*metabolism; Humans; Membrane Potentials/drug effects; Metabotropic Glutamate/genetics/*metabolism; myc/genetics; Patch-Clamp Techniques; Plasmids/genetics; Receptors; Signal Transduction/drug effects; Superior Cervical Ganglion/cytology/drug effects/metabolism; Sympathetic Nervous System/cytology/drug effects/metabolism; Western

Rights

Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).

Pages

502–508

Issue

2

Volume

312

Citation

Kammermeier Paul J; Yun June, “Activation of metabotropic glutamate receptor 1 dimers requires glutamate binding in both subunits.,” NEOMED Bibliography Database, accessed October 20, 2021, https://neomed.omeka.net/items/show/4523.

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