title: Subunit stoichiometry and arrangement in a heteromeric glutamate-gated chloride channel.
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.
authors.affiliation: Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences and The Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel.
authors.forename: Nurit
authors.initials: N
authors.lastname: Degani-Katzav
authors.affiliation: Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences and The Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel.
authors.forename: Revital
authors.initials: R
authors.lastname: Gortler
authors.affiliation: Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences and The Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel.
authors.forename: Lilach
authors.initials: L
authors.lastname: Gorodetzki
authors.affiliation: Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences and The Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel yoav.paas@biu.ac.il.
authors.forename: Yoav
authors.initials: Y
authors.lastname: Paas
mesh_terms: D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D018118:Chloride Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D009154:Mutation; D018408:Patch-Clamp Techniques
chemical_list: D018118:Chloride Channels; C109777:glutamate-gated chloride channels
keywords: Cys-loop receptors; allostery; ion channels; ivermectin; neurotransmitters