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Giménez C, Pérez-Siles G, Martínez-Villarreal J, Arribas-González E, Jiménez E, Núñez E, de Juan-Sanz J, Fernández-Sánchez E, García-Tardón N, Ibáñez I, Romanelli V, Nevado J, James VM, Topf M, Chung SK, Thomas RH, Desviat LR, Aragón C, Zafra F, Rees MI, Lapunzina P, Harvey RJ, López-Corcuera B. A novel dominant hyperekplexia mutation Y705C alters trafficking and biochemical properties of the presynaptic glycine transporter GlyT2. J Biol Chem 2012; 287:28986-9002. [PMID: 22753417 PMCID: PMC3436537 DOI: 10.1074/jbc.m111.319244] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 06/18/2012] [Indexed: 11/06/2022] Open
Abstract
Hyperekplexia or startle disease is characterized by an exaggerated startle response, evoked by tactile or auditory stimuli, producing hypertonia and apnea episodes. Although rare, this orphan disorder can have serious consequences, including sudden infant death. Dominant and recessive mutations in the human glycine receptor (GlyR) α1 gene (GLRA1) are the major cause of this disorder. However, recessive mutations in the presynaptic Na(+)/Cl(-)-dependent glycine transporter GlyT2 gene (SLC6A5) are rapidly emerging as a second major cause of startle disease. In this study, systematic DNA sequencing of SLC6A5 revealed a new dominant GlyT2 mutation: pY705C (c.2114A→G) in transmembrane domain 11, in eight individuals from Spain and the United Kingdom. Curiously, individuals harboring this mutation show significant variation in clinical presentation. In addition to classical hyperekplexia symptoms, some individuals had abnormal respiration, facial dysmorphism, delayed motor development, or intellectual disability. We functionally characterized this mutation using molecular modeling, electrophysiology, [(3)H]glycine transport, cell surface expression, and cysteine labeling assays. We found that the introduced cysteine interacts with the cysteine pair Cys-311-Cys-320 in the second external loop of GlyT2. This interaction impairs transporter maturation through the secretory pathway, reduces surface expression, and inhibits transport function. Additionally, Y705C presents altered H(+) and Zn(2+) dependence of glycine transport that may affect the function of glycinergic neurotransmission in vivo.
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Affiliation(s)
- Cecilio Giménez
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
- the IdiPAZ-Hospital Universitario La Paz
| | - Gonzalo Pérez-Siles
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
| | - Jaime Martínez-Villarreal
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
- the IdiPAZ-Hospital Universitario La Paz
| | - Esther Arribas-González
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
- the IdiPAZ-Hospital Universitario La Paz
| | - Esperanza Jiménez
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
- the IdiPAZ-Hospital Universitario La Paz
| | - Enrique Núñez
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
- the IdiPAZ-Hospital Universitario La Paz
| | - Jaime de Juan-Sanz
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
- the IdiPAZ-Hospital Universitario La Paz
| | - Enrique Fernández-Sánchez
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
| | - Noemí García-Tardón
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
- the IdiPAZ-Hospital Universitario La Paz
| | - Ignacio Ibáñez
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
| | - Valeria Romanelli
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
- the Instituto de Genética Médica y Molecular, IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid 28046, Spain
| | - Julián Nevado
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
- the Instituto de Genética Médica y Molecular, IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid 28046, Spain
| | - Victoria M. James
- the Department of Pharmacology, University College London School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Maya Topf
- the Institute of Structural and Molecular Biology, Crystallography, Birkbeck College, London WC1E 7HX, United Kingdom, and
| | - Seo-Kyung Chung
- the Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Rhys H. Thomas
- the Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Lourdes R. Desviat
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
| | - Carmen Aragón
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
- the IdiPAZ-Hospital Universitario La Paz
| | - Francisco Zafra
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
- the IdiPAZ-Hospital Universitario La Paz
| | - Mark I. Rees
- the Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Pablo Lapunzina
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
- the Instituto de Genética Médica y Molecular, IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid 28046, Spain
| | - Robert J. Harvey
- the Department of Pharmacology, University College London School of Pharmacy, London WC1N 1AX, United Kingdom
| | - Beatriz López-Corcuera
- From the Departamento de Biología Molecular and Centro de Biología Molecular “Severo Ochoa,” (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Madrid 28049, Spain
- the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain
- the IdiPAZ-Hospital Universitario La Paz
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Kozuska JL, Paulsen IM. The Cys-loop pentameric ligand-gated ion channel receptors: 50 years on. Can J Physiol Pharmacol 2012; 90:771-82. [PMID: 22493950 DOI: 10.1139/y2012-018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This year, 2011, the Department of Pharmacology at the University of Alberta celebrated its 50th anniversary. This timeframe covers nearly the entire history of Cys-loop pentameric ligand-gated ion channel (pLGIC) research. In this review we consider how major technological advancements affected our current understanding of pLGICs, and highlight the contributions made by members of our department. The individual at the center of our story is Susan Dunn; her passing earlier this year has robbed the Department of Pharmacology and the research community of a most insightful colleague. Her dissection of ligand interactions with the nAChR, together with their interpretation, was the hallmark of her extensive collaborations with Michael Raftery. Here, we highlight some electrophysiological studies from her laboratory over the last few years, using the technique that she introduced to the department in Edmonton, the 2-electrode voltage-clamp of Xenopus oocytes. Finally, we discuss some single-channel studies of the anionic GlyR and GABA(A)R that prefaced the introduction of this technique to her laboratory.
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Affiliation(s)
- Janna L Kozuska
- Department of Pharmacology, University of Alberta, 9-55 Medical Sciences Building, Edmonton, AB T6G2H7, Canada.
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Yong Y, Dreyer JL. Distribution of six transplasma membrane NADH-dehydrogenases in rat brain tissue. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1995; 89:235-52. [PMID: 8612327 DOI: 10.1016/0165-3806(95)00124-v] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Transplasma membrane redox plays a significant role in cellular activation and growth. Six isoenzymes could be prepared from purified rat brain synaptic plasma membrane. Polyclonal antibodies have been prepared against six transplasma membrane oxydoreductases (PMO-I to PMO-VI) and the tissue distribution of the various iso-enzymes have been investigated in adult rat brains by means of immunohistochemistry. PMO-I is densely observed in layers I, IV and V of the parietal cortex, in CA1 of the hippocampus (except for the molecular layer), in the caudate putamen, in the dorsal, granular and ventral parts of the auditory nuclei, in some loci of the vestibular nuclei as well as in the deep cerebellar nucleus and in the granular layer of the cerebellar cortex. PMO-II is mainly located in the polymorphic layer of the dentate gyrus and in the deep cerebellar nucleus and in the granular layer of the cerebellar cortex. PMO-III is abundant in the piriform cortex, in the pyramidal layers of both CA1 and CA2, in the diagonal band of the basal ganglia, in the supraoptic nucleus and in various loci of the magnetocellular paraventricular nucleus of the hippothalamus as well as in the vestibular nuclei from the brain stem. In addition PMO-III is also densely present in motor nuclei (oculomotor, facial, hypoglossal and ambiguus nuclei), in the reticular formation and in the deep cerebellar nucleus as well as in the Purkinje layer of the cerebellar cortex. PMO-IV has a similar location but is less abundant in the vestibular nuclei of the sensory brain stem and in the motor nucleus. PMO-V in contrast is poorly present in most brain areas compared to the other iso-enzymes, apart of the Purkinje layer of the cerebellar cortex. Finally PMO-VI is mainly present in the oriens layer and in the stratum radiatum of the hippocampus formation, in the supraoptic and lateral magnocellular nucleus of the hypothalamus, in the mesencephalic trigeminal nucleus, in the ventral auditory nucleus and in the facial nucleus of the brain stem as well as in red nucleus of the reticular formation and in the Purkinje layer of the cerebellar cortex. These data show that the iso-enzymes are located in specific brain nuclei. The significance of the results in respect to the yet very poorly defined function of PMO's is discussed.
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Affiliation(s)
- Y Yong
- Department of Biochemistry, University of Fribourg, Switzerland
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Lei S, Okita DK, Conti-Fine BM. Binding of monoclonal antibodies against the carboxyl terminal segment of the nicotinic receptor delta subunit suggests an unusual transmembrane disposition of this sequence region. Biochemistry 1995; 34:6675-88. [PMID: 7756299 DOI: 10.1021/bi00020a013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Monoclonal antibodies (mAbs) specific for the carboxyl terminal region of the delta subunit of Torpedo nicotinic acetylcholine receptor (AChR), derived from mice immunized with AChR or a synthetic carboxyl terminal sequence of the delta subunit (C delta-mAbs), were used to determine the transmembrane disposition of their epitope(s) by immunoelectron microscopy, using AChR-rich postsynaptic membrane fragments from Torpedo electroplax. Some C delta-mAbs recognized only the cytoplasmic side of the membranes, some both sides to a similar extent, and others bound mostly, but not exclusively, to the cytoplasmic side. Binding of C delta-mAbs to the membranes was specifically blocked by synthetic peptides containing the carboxyl terminal region of the delta subunit. Control anti-AChR mAbs specific for the alpha or the delta subunits, whose epitopes have known transmembrane topology, uniquely recognized the expected side of the postsynaptic membrane. Residues involved in C delta-mAb binding were identified using single residue substituted peptide analogues of the sequence delta 481-501. All C delta-mAbs recognized epitopes within the same sequence segment, delta 485-493, at the carboxyl terminal of the AChR delta subunit. These results suggest that the delta subunit of the AChR might have alternative conformations, leading to exposure of the same sequence region on the extracellular or the cytoplasmic surface. Several Pro residues are present in this region. The alternative cis or trans conformation of one or more of them might result in different folding patterns of the carboxyl terminal sequence of the delta subunit, as described for a viral protein [Liddington, R. C., Yan, Y., Moulai, J., Sahli, R., Benjamin, T. L., & Harrison, S. C. (1991) Nature 354, 278-284.
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Affiliation(s)
- S Lei
- Department of Biochemistry, University of Minnesota, St. Paul 55108, USA
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Czajkowski C, DiPaola M, Bodkin M, Salazar-Jimenez G, Holtzman E, Karlin A. The intactness and orientation of acetylcholine receptor-rich membrane from Torpedo californica electric tissue. Arch Biochem Biophys 1989; 272:412-20. [PMID: 2751309 DOI: 10.1016/0003-9861(89)90235-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
By a mild and highly reproducible fractionation of Torpedo californica electric tissue, we prepared membrane which was 30 times enriched in nicotinic acetylcholine receptor (AChR). This preparation was neither alkali-stripped nor reconstituted and consequently contained nu (43-kDa protein), which is associated with the cytoplasmic aspect of the receptor. We tested this membrane for the presence of sealed vesicles and determined the orientation of these vesicles by combining three methods. Two of these methods were based on the accessibilities, in the presence and absence of detergent, of the extracellular acetylcholine binding site to alpha-bungarotoxin and of the intracellular nu to trypsin. These two methods are specific for AChR-containing membrane. The third method was morphometry of electron micrographs, by which we estimated the proportion of sequestered membrane. These methods taken together indicated that approximately 45% of the AChR-containing membrane was in the form of leaky vesicles or sheets, 33% was sealed right-side-out vesicles, 11% was sealed inside-out vesicles, and 11% was sequestered within multilamellar or multivesicular vesicles. The complexity of this membrane needs to be taken into account in sidedness studies of the AChR.
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Affiliation(s)
- C Czajkowski
- Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York, New York 10032
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White BH, Cohen JB. Photolabeling of membrane-bound Torpedo nicotinic acetylcholine receptor with the hydrophobic probe 3-trifluoromethyl-3-(m-[125I]iodophenyl)diazirine. Biochemistry 1988; 27:8741-51. [PMID: 3242605 DOI: 10.1021/bi00424a009] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The hydrophobic, photoactivatable probe 3-trifluoromethyl-3-(m-[125I]iodophenyl)diazirine ([125I]TID) was used to label acetylcholine receptor rich membranes purified from Torpedo californica electric organ. All four subunits of the acetylcholine receptor (AChR) were found to incorporate label, with the gamma-subunit incorporating approximately 4 times as much as each of the other subunits. Carbamylcholine, an agonist, and histrionicotoxin, a noncompetitive antagonist, both strongly inhibited labeling of all AChR subunits in a specific and dose-dependent manner. In contrast, the competitive antagonist alpha-bungarotoxin and the noncompetitive antagonist phencyclidine had only modest effects on [125I]TID labeling of the AChR. The regions of the AChR alpha-subunit that incorporate [125I]TID were mapped by Staphylococcus aureus V8 protease digestion. The carbamylcholine-sensitive site of labeling was localized to a 20-kDa V8 cleavage fragment that begins at Ser-173 and is of sufficient length to contain the three hydrophobic regions M1, M2, and M3. A 10-kDa fragment beginning at Asn-339 and containing the hydrophobic region M4 also incorporated [125I]TID but in a carbamylcholine-insensitive manner. Two further cleavage fragments, which together span about one-third of the alpha-subunit amino terminus, incorporated no detectable [125I]TID. The mapping results place constraints on suggested models of AChR subunit topology.
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Affiliation(s)
- B H White
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110
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Kosower EM. A structural and dynamic model for the nicotinic acetylcholine receptor. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 168:431-49. [PMID: 3311748 DOI: 10.1111/j.1432-1033.1987.tb13437.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Folding of the five polypeptide subunits (alpha 2 beta gamma delta) of the nicotinic acetylcholine receptor (AChR) into a functional structural model is described. The principles used to arrange the sequences into a structure include: (1) hydrophobicity----membrane-crossing segments; (2) amphipathic character----ion-carrying segments (ion channel with single group rotations); (3) molecular shape (elongated, pentagonal cylinder)----folding dimensions of exobilayer portion; (4) choice of acetylcholine binding sites----specific folding of exobilayer segments; (5) location of reducible disulfides (near agonist binding site)----additional specification of exobilayer arrangement; (6) genetic homology----consistency of functional group choices; (7) noncompetitive antagonist labeling----arrangement of bilayer helices. The AChR model is divided into three parts: (a) exobilayer consisting of 11 antiparallel beta-strands from each subunit; (b) bilayer consisting of four hydrophobic and one amphiphilic alpha-helix from each subunit; (c) cytoplasmic consisting of one (folded) loop from each subunit. The exobilayer strands can form a closed 'flower' (the 'resting state') which is opened ('activated') by agonists bound perpendicular to the strands. Rearrangement of the agonists to a strand-parallel position and partial closing of the 'flower' leads to a desensitized receptor. The actions of acetylcholine and succinoyl and suberoyl bis-cholines are clarified by the model. The opening and closing of the exobilayer 'flower' controls access to the ion channel which is composed of the five amphiphilic bilayer helices. A molecular mechanism for ion flow in the channel is given. Openings interrupted by short duration closings (50 microseconds) depend upon channel group motions. The unusual photolabeling of intrabilayer serines in alpha, beta and delta subunits but not in gamma subunits near the binding site for non-competitive antagonists is explained along with a mechanism for the action of these antagonists such as phencyclidine. The unusual alpha 192Cys-193Cys disulfide may have a special peptide arrangement, such as a cis-peptide bond to a following proline (G.A. Petsko and E.M. Kosower, unpublished results). The position of phosphorylatable sites and proline-rich segments are noted for the cytoplasmic loops. The dynamic behavior of the AChR channel and many different experimental results can be interpreted in terms of the model. An example is the lowering of ionic conductivity on substitution of bovine for Torpedo delta M2 segment. The model represents a useful construct for the design of experiments on AChR.
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Affiliation(s)
- E M Kosower
- Biophysical Organic Chemistry Unit, School of Chemistry, Sackler Faculty of Exact Sciences, Tel-Aviv University, Israel
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