| Structural highlights
Disease
GLRA1_HUMAN Defects in GLRA1 are the cause of hyperekplexia, hereditary, type 1 (HKPX1) [MIM:149400. A neurologic disorder characterized by muscular rigidity of central nervous system origin, particularly in the neonatal period, and by an exaggerated startle response to unexpected acoustic or tactile stimuli.[1] [:][2] [3] [4] [5] [6] [7] [8] [9] [10]
Function
GLRA1_HUMAN The glycine receptor is a neurotransmitter-gated ion channel. Binding of glycine to its receptor increases the chloride conductance and thus produces hyperpolarization (inhibition of neuronal firing).GLIC_GLOVI Cationic channel with similar permeabilities for Na(+) and K(+), that is activated by an increase of the proton concentration on the extracellular side. Displays no permeability for chloride ions. Shows slow kinetics of activation, no desensitization and a single channel conductance of 8 pS. Might contribute to adaptation to external pH change.[11]
Publication Abstract from PubMed
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 alpha1GlyR 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 A resolution. The TMD of the alpha1GlyR 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 alpha1GlyR, 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 alpha1GlyR, suggesting a structural explanation for the effect of some key hyperekplexic allosteric mutations. The first X-ray structure of the TMD of the alpha1GlyR solved here using GLIC as a scaffold paves the way for mechanistic investigation and design of allosteric modulators of a human receptor.
Allosteric and hyperekplexic mutant phenotypes investigated on an alpha1 glycine receptor transmembrane structure.,Moraga-Cid G, Sauguet L, Huon C, Malherbe L, Girard-Blanc C, Petres S, Murail S, Taly A, Baaden M, Delarue M, Corringer PJ Proc Natl Acad Sci U S A. 2015 Mar 3;112(9):2865-70. doi:, 10.1073/pnas.1417864112. Epub 2015 Feb 17. PMID:25730860[12]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Shiang R, Ryan SG, Zhu YZ, Hahn AF, O'Connell P, Wasmuth JJ. Mutations in the alpha 1 subunit of the inhibitory glycine receptor cause the dominant neurologic disorder, hyperekplexia. Nat Genet. 1993 Dec;5(4):351-8. PMID:8298642 doi:https://dx.doi.org/10.1038/ng1293-351
- ↑ Langosch D, Laube B, Rundstrom N, Schmieden V, Bormann J, Betz H. Decreased agonist affinity and chloride conductance of mutant glycine receptors associated with human hereditary hyperekplexia. EMBO J. 1994 Sep 15;13(18):4223-8. PMID:7925268
- ↑ Schorderet DF, Pescia G, Bernasconi A, Regli F. An additional family with Startle disease and a G1192A mutation at the alpha 1 subunit of the inhibitory glycine receptor gene. Hum Mol Genet. 1994 Jul;3(7):1201. PMID:7981700
- ↑ Rees MI, Andrew M, Jawad S, Owen MJ. Evidence for recessive as well as dominant forms of startle disease (hyperekplexia) caused by mutations in the alpha 1 subunit of the inhibitory glycine receptor. Hum Mol Genet. 1994 Dec;3(12):2175-9. PMID:7881416
- ↑ Shiang R, Ryan SG, Zhu YZ, Fielder TJ, Allen RJ, Fryer A, Yamashita S, O'Connell P, Wasmuth JJ. Mutational analysis of familial and sporadic hyperekplexia. Ann Neurol. 1995 Jul;38(1):85-91. PMID:7611730 doi:https://dx.doi.org/10.1002/ana.410380115
- ↑ Milani N, Dalpra L, del Prete A, Zanini R, Larizza L. A novel mutation (Gln266-->His) in the alpha 1 subunit of the inhibitory glycine-receptor gene (GLRA1) in hereditary hyperekplexia. Am J Hum Genet. 1996 Feb;58(2):420-2. PMID:8571969
- ↑ Elmslie FV, Hutchings SM, Spencer V, Curtis A, Covanis T, Gardiner RM, Rees M. Analysis of GLRA1 in hereditary and sporadic hyperekplexia: a novel mutation in a family cosegregating for hyperekplexia and spastic paraparesis. J Med Genet. 1996 May;33(5):435-6. PMID:8733061
- ↑ Seri M, Bolino A, Galietta LJ, Lerone M, Silengo M, Romeo G. Startle disease in an Italian family by mutation (K276E): The alpha-subunit of the inhibiting glycine receptor. Hum Mutat. 1997;9(2):185-7. PMID:9067762 doi:<185::AID-HUMU14>3.0.CO;2-Z 10.1002/(SICI)1098-1004(1997)9:2<185::AID-HUMU14>3.0.CO;2-Z
- ↑ Vergouwe MN, Tijssen MA, Peters AC, Wielaard R, Frants RR. Hyperekplexia phenotype due to compound heterozygosity for GLRA1 gene mutations. Ann Neurol. 1999 Oct;46(4):634-8. PMID:10514101
- ↑ Saul B, Kuner T, Sobetzko D, Brune W, Hanefeld F, Meinck HM, Becker CM. Novel GLRA1 missense mutation (P250T) in dominant hyperekplexia defines an intracellular determinant of glycine receptor channel gating. J Neurosci. 1999 Feb 1;19(3):869-77. PMID:9920650
- ↑ Bocquet N, Prado de Carvalho L, Cartaud J, Neyton J, Le Poupon C, Taly A, Grutter T, Changeux JP, Corringer PJ. A prokaryotic proton-gated ion channel from the nicotinic acetylcholine receptor family. Nature. 2007 Jan 4;445(7123):116-9. Epub 2006 Dec 10. PMID:17167423 doi:10.1038/nature05371
- ↑ Moraga-Cid G, Sauguet L, Huon C, Malherbe L, Girard-Blanc C, Petres S, Murail S, Taly A, Baaden M, Delarue M, Corringer PJ. Allosteric and hyperekplexic mutant phenotypes investigated on an alpha1 glycine receptor transmembrane structure. Proc Natl Acad Sci U S A. 2015 Mar 3;112(9):2865-70. doi:, 10.1073/pnas.1417864112. Epub 2015 Feb 17. PMID:25730860 doi:https://dx.doi.org/10.1073/pnas.1417864112
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