Subunit stoichiometry and arrangement in a heteromeric glutamate-gated chloride channel

Nurit Degani-Katzav, Revital Gortler, Lilach DGorodetzki, Yoav Paas

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

The invertebrate glutamate-gated chloride-selective receptors (GluClRs) are ion channels serving as targets for ivermectin (IVM), a broad-spectrum anthelmintic drug used to treat human parasitic diseases like river blindness and lymphatic filariasis. The native GluClR is a heteropentamer consisting of α and β subunit types, with yet unknown subunit stoichiometry and arrangement. Based on the recent crystal structure of a homomeric GluClαR, we introduced mutations at the intersubunit interfaces where Glu (the neurotransmitter) binds. By electrophysiological characterization of these mutants, we found heteromeric assemblies with two equivalent Glu-binding sites at β/α intersubunit interfaces, where the GluClβ and GluClα subunits, respectively, contribute the "principal" and "complementary" components of the putative Glu-binding pockets. We identified a mutation in the IVM-binding site (far away from the Glu-binding sites), which significantly increased the sensitivity of the heteromeric mutant receptor to both Glu and IVM, and improved the receptor subunits' cooperativity. We further characterized this heteromeric GluClR mutant as a receptor having a third Glu-binding site at an α/α intersubunit interface. Altogether, our data unveil heteromeric GluClR assemblies having three α and two β subunits arranged in a counterclockwise β-α-β-α-α fashion, as viewed from the extracellular side, with either two or three Glu-binding site interfaces.

Original languageEnglish
Pages (from-to)E644-E653
JournalProceedings of the National Academy of Sciences of the United States of America
Volume113
Issue number5
DOIs
StatePublished - 2 Feb 2016

Bibliographical note

We thank H. A. Lester for providing us with the initial GluClα subunit construct.

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