The metabotropic glutamate G-protein-coupled receptors mGluR3 and mGluR1a are voltage-sensitive

Lily Ohana, Ofra Barchad, Itzchak Parnas, Hanna Parnas*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

66 Scopus citations

Abstract

G-protein-coupled receptors play a key role in signal transduction processes. Despite G-protein-coupled receptors being transmembrane proteins, the notion that they exhibit voltage sensitivity is rather novel. Here we examine whether two metabotropic glutamate receptors, mGluR3 and mGluR1a, both involved in fundamental physiological processes, exhibit, by themselves, voltage sensitivity. Measuring mGluR3-induced K+ currents and mGluR1a-induced Ca2+-activated Cl- currents in Xenopus oocytes, we show that the apparent affinity toward glutamate decreases (mGluR3) or increases (mGluR1a) upon depolarization. Measurements of binding of [3H] glutamate to oocytes expressing either mGluR3 or mGluR1a corroborated the electrophysiological results. Using the chimeric Gα subunit, we further show that the voltage sensitivity does not reside in the G-protein. To locate sites within the receptors that are involved in the voltage sensitivity, we used chimeric mGluR1a, where the intracellular loops that couple to the G-protein were replaced by those of mGluR3. The voltage sensitivity of the chimeric mGluR1a resembled that of mGluR3 and not that of the parental mGluR1a. The cumulative results indicate that the voltage sensitivity does not reside downstream to the activation of the receptors but rather in the mGluR3 and mGluR1a themselves. Furthermore, the intracellular loops play a crucial role in relaying changes in membrane potential to changes in the affinity of the receptors toward glutamate.

Original languageEnglish
Pages (from-to)24204-24215
Number of pages12
JournalJournal of Biological Chemistry
Volume281
Issue number34
DOIs
StatePublished - 25 Aug 2006

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