Allosteric and hyperekplexic mutant phenotypes investigated on an α1 glycine receptor transmembrane structure.
The glycine receptor (GlyR) is a pentameric ligand-gated ion channel (pLGIC) mediating inhibitory transmission in the nervous system. Its transmembrane domain (TMD) is the target of allosteric modulators such as general anesthetics and ethanol and is a major locus for hyperekplexic congenital mutations altering the allosteric transitions of activation or desensitization. We previously showed that the TMD of the human α1GlyR could be fused to the extracellular domain of GLIC, a bacterial pLGIC, to form a functional chimera called Lily. Here, we overexpress Lily in Schneider 2 insect cells and solve its structure by X-ray crystallography at 3.5 Å resolution. The TMD of the α1GlyR adopts a closed-channel conformation involving a single ring of hydrophobic residues at the center of the pore. Electrophysiological recordings show that the phenotypes of key allosteric mutations of the α1GlyR, scattered all along the pore, are qualitatively preserved in this chimera, including those that confer decreased sensitivity to agonists, constitutive activity, decreased activation kinetics, or increased desensitization kinetics. Combined structural and functional data indicate a pore-opening mechanism for the α1GlyR, suggesting a structural explanation for the effect of some key hyperekplexic allosteric mutations. The first X-ray structure of the TMD of the α1GlyR solved here using GLIC as a scaffold paves the way for mechanistic investigation and design of allosteric modulators of a human receptor.
Channel-Receptors Unit, Institut Pasteur, 75015 Paris, France; CNRS UMR 3571, 75015 Paris, France;
Gustavo
G
Moraga-Cid
Unité de Dynamique Structurale des Macromolécules, Institut Pasteur, 75015 Paris, France; CNRS UMR 3528, 75015 Paris, France;
Ludovic
L
Sauguet
Channel-Receptors Unit, Institut Pasteur, 75015 Paris, France; CNRS UMR 3571, 75015 Paris, France;
Christèle
C
Huon
Channel-Receptors Unit, Institut Pasteur, 75015 Paris, France; CNRS UMR 3571, 75015 Paris, France; Unité de Dynamique Structurale des Macromolécules, Institut Pasteur, 75015 Paris, France; CNRS UMR 3528, 75015 Paris, France;
Laurie
L
Malherbe
Plateforme de Production de Protéines Recombinantes, Institut Pasteur, 75015 Paris, France; and.
Christine
C
Girard-Blanc
Plateforme de Production de Protéines Recombinantes, Institut Pasteur, 75015 Paris, France; and.
Stéphane
S
Petres
Theoretical Biochemistry Laboratory, Institut de Biologie Physico-Chimique, CNRS UPR9080, Université Paris Diderot Sorbonne Paris Cité, 75015 Paris, France.
Samuel
S
Murail
Theoretical Biochemistry Laboratory, Institut de Biologie Physico-Chimique, CNRS UPR9080, Université Paris Diderot Sorbonne Paris Cité, 75015 Paris, France.
Antoine
A
Taly
Theoretical Biochemistry Laboratory, Institut de Biologie Physico-Chimique, CNRS UPR9080, Université Paris Diderot Sorbonne Paris Cité, 75015 Paris, France.
Marc
M
Baaden
Unité de Dynamique Structurale des Macromolécules, Institut Pasteur, 75015 Paris, France; CNRS UMR 3528, 75015 Paris, France; pjcorrin@pasteur.fr delarue@pasteur.fr.
Marc
M
Delarue
Channel-Receptors Unit, Institut Pasteur, 75015 Paris, France; CNRS UMR 3571, 75015 Paris, France; pjcorrin@pasteur.fr delarue@pasteur.fr.
Pierre-Jean
PJ
Corringer
D000494:Allosteric Regulation / Q000502:physiology; D000818:Animals; D018360:Crystallography, X-Ray; D004331:Drosophila melanogaster; D006801:Humans; D017434:Protein Structure, Tertiary; D018009:Receptors, Glycine / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship
D018009:Receptors, Glycine
allostery; glycine receptor; hyperekplexia