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Intermediate closed state for glycine receptor function revealed by cysteine cross-linking.
- Source :
-
Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2013 Oct 15; Vol. 110 (42), pp. 17113-8. Date of Electronic Publication: 2013 Oct 01. - Publication Year :
- 2013
-
Abstract
- Pentameric ligand-gated ion channels (pLGICs) mediate signal transmission by coupling the binding of extracellular ligands to the opening of their ion channel. Agonist binding elicits activation and desensitization of pLGICs, through several conformational states, that are, thus far, incompletely characterized at the structural level. We previously reported for GLIC, a prokaryotic pLGIC, that cross-linking of a pair of cysteines at both sides of the extracellular and transmembrane domain interface stabilizes a locally closed (LC) X-ray structure. Here, we introduced the homologous pair of cysteines on the human α1 glycine receptor. We show by electrophysiology that cysteine cross-linking produces a gain-of-function phenotype characterized by concomitant constitutive openings, increased agonist potency, and equalization of efficacies of full and partial agonists. However, it also produces a reduction of maximal currents at saturating agonist concentrations without change of the unitary channel conductance, an effect reversed by the positive allosteric modulator propofol. The cross-linking thus favors a unique closed state distinct from the resting and longest-lived desensitized states. Fitting the data according to a three-state allosteric model suggests that it could correspond to a LC conformation. Its plausible assignment to a gating intermediate or a fast-desensitized state is discussed. Overall, our data show that relative movement of two loops at the extracellular-transmembrane interface accompanies orthosteric agonist-mediated gating.
- Subjects :
- Allosteric Regulation drug effects
Allosteric Regulation physiology
Anesthetics, Intravenous chemistry
Anesthetics, Intravenous pharmacology
Animals
Crystallography, X-Ray
HEK293 Cells
Humans
Ion Channel Gating drug effects
Ion Transport physiology
Propofol chemistry
Propofol pharmacology
Protein Structure, Secondary
Protein Structure, Tertiary
Receptors, Glycine agonists
Receptors, Glycine genetics
Receptors, Glycine metabolism
Xenopus laevis
Ion Channel Gating physiology
Models, Molecular
Receptors, Glycine chemistry
Subjects
Details
- Language :
- English
- ISSN :
- 1091-6490
- Volume :
- 110
- Issue :
- 42
- Database :
- MEDLINE
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Type :
- Academic Journal
- Accession number :
- 24085847
- Full Text :
- https://doi.org/10.1073/pnas.1317009110