Structural Arrangement Produced by Concanavalin A Binding to Homomeric GluK2 Receptors.

Cuauhtemoc U Gonzalez,Elisa Carrillo,Vasanthi Jayaraman,Vladimir Berka

doi:10.3390/membranes11080613

Cuauhtemoc U Gonzalez, Elisa Carrillo + Show 2 more

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https://doi.org/10.3390/membranes11080613

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Abstract

Kainate receptors are members of the ionotropic glutamate receptor family. They form cation-specific transmembrane channels upon binding glutamate that desensitize in the continued presence of agonists. Concanavalin A (Con-A), a lectin, stabilizes the active open-channel state of the kainate receptor and reduces the extent of desensitization. In this study, we used single-molecule fluorescence resonance energy transfer (smFRET) to investigate the conformational changes underlying kainate receptor modulation by Con-A. These studies showed that Con-A binding to GluK2 homomeric kainate receptors resulted in closer proximity of the subunits at the dimer–dimer interface at the amino-terminal domain as well as between the subunits at the dimer interface at the agonist-binding domain. Additionally, the modulation of receptor functions by monovalent ions, which bind to the dimer interface at the agonist-binding domain, was not observed in the presence of Con-A. Based on these results, we conclude that Con-A modulation of kainate receptor function is mediated by a shift in the conformation of the kainate receptor toward a tightly packed extracellular domain.

Highlights

Kainate receptors belong to the family of cation-permeable channels known as ionotropic glutamate receptors
Given that the subunit interfaces played a role in conformational control of function, here we studied the conformational changes underlying the reduction in desensitization of kainate receptors by Concanavalin A (Con-A) by investigating the changes at the amino-terminal domain (ATD) and agonist-binding domain (ABD) subunit interfaces
For investigating changes at the dimer–dimer interface at the ATD we introduced a cysteine at site 266, referred to as GluK2-ATD

Summary

Introduction

Kainate receptors belong to the family of cation-permeable channels known as ionotropic glutamate receptors (iGluRs). Each subunit of the receptor can be separated into four major domains: the two extracellular domains, which comprise the amino-terminal domain (ATD) and the agonist-binding domain (ABD); the transmembrane segments; and the cytosolic carboxy-terminal domain [3,5,6]. It is through induced conformational changes occurring at these domains that agonists and other small molecules regulate channel activity [7,8,9]. Structural and spectroscopic measurements have provided significant insight into the conformational changes underlying kainate receptor activation and desensitization [6,7,9,10,11,12,13,14]

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