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Boudkkazi S, Schwenk J, Nakaya N, Brechet A, Kollewe A, Harada H, Bildl W, Kulik A, Dong L, Sultana A, Zolles G, Schulte U, Tomarev S, Fakler B. A Noelin-organized extracellular network of proteins required for constitutive and context-dependent anchoring of AMPA-receptors. Neuron 2023; 111:2544-2556.e9. [PMID: 37591201 PMCID: PMC10441612 DOI: 10.1016/j.neuron.2023.07.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 04/21/2023] [Accepted: 07/20/2023] [Indexed: 08/19/2023]
Abstract
Information processing and storage in the brain rely on AMPA-receptors (AMPARs) and their context-dependent dynamics in synapses and extra-synaptic sites. We found that distribution and dynamics of AMPARs in the plasma membrane are controlled by Noelins, a three-member family of conserved secreted proteins expressed throughout the brain in a cell-type-specific manner. Noelin tetramers tightly assemble with the extracellular domains of AMPARs and interconnect them in a network-like configuration with a variety of secreted and membrane-anchored proteins including Neurexin1, Neuritin1, and Seizure 6-like. Knock out of Noelins1-3 profoundly reduced AMPARs in synapses onto excitatory and inhibitory (inter)neurons, decreased their density and clustering in dendrites, and abolished activity-dependent synaptic plasticity. Our results uncover an endogenous mechanism for extracellular anchoring of AMPARs and establish Noelin-organized networks as versatile determinants of constitutive and context-dependent neurotransmission.
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Affiliation(s)
- Sami Boudkkazi
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Jochen Schwenk
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Naoki Nakaya
- National Eye Institute, Section of Retinal Ganglion Cell Biology, National Institutes of Health, Bethesda, MD, USA
| | - Aline Brechet
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Astrid Kollewe
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Harumi Harada
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Wolfgang Bildl
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Akos Kulik
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Lijin Dong
- National Eye Institute, Genetic Engineering Facility, National Institutes of Health, Bethesda, MD, USA
| | - Afia Sultana
- National Eye Institute, Section of Retinal Ganglion Cell Biology, National Institutes of Health, Bethesda, MD, USA
| | - Gerd Zolles
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Uwe Schulte
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany; Signaling Research Centers BIOSS and CIBSS, University of Freiburg, Schänzlestr. 18, 79104 Freiburg, Germany; Logopharm GmbH, Schlossstr. 14, 79232 March-Buchheim, Germany
| | - Stanislav Tomarev
- National Eye Institute, Section of Retinal Ganglion Cell Biology, National Institutes of Health, Bethesda, MD, USA.
| | - Bernd Fakler
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany; Signaling Research Centers BIOSS and CIBSS, University of Freiburg, Schänzlestr. 18, 79104 Freiburg, Germany.
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Kollewe A, Schwarz Y, Oleinikov K, Raza A, Haupt A, Wartenberg P, Wyatt A, Boehm U, Ectors F, Bildl W, Zolles G, Schulte U, Bruns D, Flockerzi V, Fakler B. Subunit composition, molecular environment, and activation of native TRPC channels encoded by their interactomes. Neuron 2022; 110:4162-4175.e7. [PMID: 36257322 DOI: 10.1016/j.neuron.2022.09.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 08/15/2022] [Accepted: 09/23/2022] [Indexed: 12/24/2022]
Abstract
In the mammalian brain TRPC channels, a family of Ca2+-permeable cation channels, are involved in a variety of processes from neuronal growth and synapse formation to transmitter release, synaptic transmission and plasticity. The molecular appearance and operation of native TRPC channels, however, remained poorly understood. Here, we used high-resolution proteomics to show that TRPC channels in the rodent brain are macro-molecular complexes of more than 1 MDa in size that result from the co-assembly of the tetrameric channel core with an ensemble of interacting proteins (interactome). The core(s) of TRPC1-, C4-, and C5-containing channels are mostly heteromers with defined stoichiometries for each subtype, whereas TRPC3, C6, and C7 preferentially form homomers. In addition, TRPC1/C4/C5 channels may co-assemble with the metabotropic glutamate receptor mGluR1, thus guaranteeing both specificity and reliability of channel activation via the phospholipase-Ca2+ pathway. Our results unveil the subunit composition of native TRPC channels and resolve the molecular details underlying their activation.
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Affiliation(s)
- Astrid Kollewe
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Yvonne Schwarz
- Institute of Physiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany
| | - Katharina Oleinikov
- Institute of Physiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany
| | - Ahsan Raza
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, 66421 Homburg, Germany
| | - Alexander Haupt
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Philipp Wartenberg
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, 66421 Homburg, Germany
| | - Amanda Wyatt
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, 66421 Homburg, Germany
| | - Ulrich Boehm
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, 66421 Homburg, Germany
| | - Fabien Ectors
- Transgenic facility, FARAH Research Center, Faculty of Veterinary Medicine, University of Liège, 4000 Liège, Belgium
| | - Wolfgang Bildl
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Gerd Zolles
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany
| | - Uwe Schulte
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany; Signalling Research Centres BIOSS and CIBSS, Schänzlestr. 18, 79104 Freiburg, Germany
| | - Dieter Bruns
- Institute of Physiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany
| | - Veit Flockerzi
- Experimental and Clinical Pharmacology and Toxicology, PZMS, Saarland University, 66421 Homburg, Germany.
| | - Bernd Fakler
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104 Freiburg, Germany; Signalling Research Centres BIOSS and CIBSS, Schänzlestr. 18, 79104 Freiburg, Germany; Center for Basics in NeuroModulation, Breisacherstr. 4, 79106 Freiburg, Germany.
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Kollewe A, Chubanov V, Tseung FT, Correia L, Schmidt E, Rössig A, Zierler S, Haupt A, Müller CS, Bildl W, Schulte U, Nicke A, Fakler B, Gudermann T. The molecular appearance of native TRPM7 channel complexes identified by high-resolution proteomics. eLife 2021; 10:68544. [PMID: 34766907 PMCID: PMC8616561 DOI: 10.7554/elife.68544] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 11/08/2021] [Indexed: 12/22/2022] Open
Abstract
The transient receptor potential melastatin-subfamily member 7 (TRPM7) is a ubiquitously expressed membrane protein consisting of ion channel and protein kinase domains. TRPM7 plays a fundamental role in the cellular uptake of divalent cations such as Zn2+, Mg2+, and Ca2+, and thus shapes cellular excitability, plasticity, and metabolic activity. The molecular appearance and operation of TRPM7 channels in native tissues have remained unresolved. Here, we investigated the subunit composition of endogenous TRPM7 channels in rodent brain by multi-epitope affinity purification and high-resolution quantitative mass spectrometry (MS) analysis. We found that native TRPM7 channels are high-molecular-weight multi-protein complexes that contain the putative metal transporter proteins CNNM1-4 and a small G-protein ADP-ribosylation factor-like protein 15 (ARL15). Heterologous reconstitution experiments confirmed the formation of TRPM7/CNNM/ARL15 ternary complexes and indicated that complex formation effectively and specifically impacts TRPM7 activity. These results open up new avenues towards a mechanistic understanding of the cellular regulation and function of TRPM7 channels.
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Affiliation(s)
- Astrid Kollewe
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Vladimir Chubanov
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany
| | - Fong Tsuen Tseung
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany
| | - Leonor Correia
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany
| | - Eva Schmidt
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany
| | - Anna Rössig
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany
| | - Susanna Zierler
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany.,Institute of Pharmacology, Johannes Kepler University Linz, Linz, Austria
| | - Alexander Haupt
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Catrin Swantje Müller
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Wolfgang Bildl
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Uwe Schulte
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, Freiburg, Germany
| | - Annette Nicke
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany
| | - Bernd Fakler
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, Freiburg, Germany
| | - Thomas Gudermann
- Walther-Straub Institute of Pharmacology and Toxicology, LMU Munich, Munich, Germany.,German Center for Lung Research, Munich, Germany
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Schmidt N, Kollewe A, Constantin CE, Henrich S, Ritzau-Jost A, Bildl W, Saalbach A, Hallermann S, Kulik A, Fakler B, Schulte U. Neuroplastin and Basigin Are Essential Auxiliary Subunits of Plasma Membrane Ca2+-ATPases and Key Regulators of Ca2+ Clearance. Neuron 2017; 96:827-838.e9. [DOI: 10.1016/j.neuron.2017.09.038] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2017] [Revised: 07/31/2017] [Accepted: 09/22/2017] [Indexed: 12/21/2022]
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Bröker-Lai J, Kollewe A, Schindeldecker B, Pohle J, Nguyen Chi V, Mathar I, Guzman R, Schwarz Y, Lai A, Weißgerber P, Schwegler H, Dietrich A, Both M, Sprengel R, Draguhn A, Köhr G, Fakler B, Flockerzi V, Bruns D, Freichel M. Heteromeric channels formed by TRPC1, TRPC4 and TRPC5 define hippocampal synaptic transmission and working memory. EMBO J 2017; 36:2770-2789. [PMID: 28790178 DOI: 10.15252/embj.201696369] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 07/01/2017] [Accepted: 07/07/2017] [Indexed: 12/30/2022] Open
Abstract
Canonical transient receptor potential (TRPC) channels influence various neuronal functions. Using quantitative high-resolution mass spectrometry, we demonstrate that TRPC1, TRPC4, and TRPC5 assemble into heteromultimers with each other, but not with other TRP family members in the mouse brain and hippocampus. In hippocampal neurons from Trpc1/Trpc4/Trpc5-triple-knockout (Trpc1/4/5-/-) mice, lacking any TRPC1-, TRPC4-, or TRPC5-containing channels, action potential-triggered excitatory postsynaptic currents (EPSCs) were significantly reduced, whereas frequency, amplitude, and kinetics of quantal miniature EPSC signaling remained unchanged. Likewise, evoked postsynaptic responses in hippocampal slice recordings and transient potentiation after tetanic stimulation were decreased. In vivo, Trpc1/4/5-/- mice displayed impaired cross-frequency coupling in hippocampal networks and deficits in spatial working memory, while spatial reference memory was unaltered. Trpc1/4/5-/- animals also exhibited deficiencies in adapting to a new challenge in a relearning task. Our results indicate the contribution of heteromultimeric channels from TRPC1, TRPC4, and TRPC5 subunits to the regulation of mechanisms underlying spatial working memory and flexible relearning by facilitating proper synaptic transmission in hippocampal neurons.
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Affiliation(s)
- Jenny Bröker-Lai
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany
| | - Astrid Kollewe
- Institute of Physiology, University of Freiburg, Freiburg, Germany
| | - Barbara Schindeldecker
- Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Jörg Pohle
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany.,Physiology of Neural Networks, Psychiatry/Psychopharmacology, Central Institute of Mental Health, J5, Heidelberg University, Mannheim, Germany
| | - Vivan Nguyen Chi
- Institute of Physiology and Pathophysiology, Heidelberg University, Heidelberg, Germany
| | - Ilka Mathar
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany
| | - Raul Guzman
- Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Yvonne Schwarz
- Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Alan Lai
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany
| | - Petra Weißgerber
- Experimental and Clinical Pharmacology and Toxicology, Saarland University, Homburg, Germany
| | | | - Alexander Dietrich
- Walther-Straub-Institute for Pharmacology and Toxicology, Ludwig-Maximilians-University München, München, Germany
| | - Martin Both
- Institute of Physiology and Pathophysiology, Heidelberg University, Heidelberg, Germany
| | - Rolf Sprengel
- Max Planck Research Group of the Max Planck Institute for Medical Research at the Institute for Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
| | - Andreas Draguhn
- Institute of Physiology and Pathophysiology, Heidelberg University, Heidelberg, Germany
| | - Georg Köhr
- Physiology of Neural Networks, Psychiatry/Psychopharmacology, Central Institute of Mental Health, J5, Heidelberg University, Mannheim, Germany
| | - Bernd Fakler
- Institute of Physiology, University of Freiburg, Freiburg, Germany.,BIOSS, Center for Biological Signaling Studies, University of Freiburg, Freiburg, Germany‡
| | - Veit Flockerzi
- Experimental and Clinical Pharmacology and Toxicology, Saarland University, Homburg, Germany
| | - Dieter Bruns
- Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Marc Freichel
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany
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Takacs Z, Toups M, Kollewe A, Johnson E, Cuello L, Driessens G, Koide A, Ponte C, Perozo E, Gajewski T, Suarez-Kurtz G, Koide S, Strots O, Ostemeyer J, Goldstein S. Designer Ligands Specific for Kv1.3 Channels from a Scorpion Neurotoxin-Based Library. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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7
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Takacs Z, Toups M, Kollewe A, Johnson E, Cuello LG, Driessens G, Biancalana M, Koide A, Ponte CG, Perozo E, Gajewski TF, Suarez-Kurtz G, Koide S, Goldstein SAN. A designer ligand specific for Kv1.3 channels from a scorpion neurotoxin-based library. Proc Natl Acad Sci U S A 2009; 106:22211-6. [PMID: 20007782 PMCID: PMC2799710 DOI: 10.1073/pnas.0910123106] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Indexed: 02/03/2023] Open
Abstract
Venomous animals immobilize prey using protein toxins that act on ion channels and other targets of biological importance. Broad use of toxins for biomedical research, diagnosis, and therapy has been limited by inadequate target discrimination, for example, among ion channel subtypes. Here, a synthetic toxin is produced by a new strategy to be specific for human Kv1.3 channels, critical regulators of immune T cells. A phage display library of 11,200 de novo proteins is designed using the alpha-KTx scaffold of 31 scorpion toxin sequences known or predicted to bind to potassium channels. Mokatoxin-1 (moka1) is isolated by affinity selection on purified target. Moka1 blocks Kv1.3 at nanomolar levels that do not inhibit Kv1.1, Kv1.2, or KCa1.1. As a result, moka1 suppresses CD3/28-induced cytokine secretion by T cells without cross-reactive gastrointestinal hyperactivity. The 3D structure of moka1 rationalizes its specificity and validates the engineering approach, revealing a unique interaction surface supported on an alpha-KTx scaffold. This scaffold-based/target-biased strategy overcomes many obstacles to production of selective toxins.
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Affiliation(s)
- Zoltan Takacs
- Department of Pediatrics and Institute of Molecular Pediatric Sciences
| | - Megan Toups
- Department of Pediatrics and Institute of Molecular Pediatric Sciences
| | - Astrid Kollewe
- Department of Pediatrics and Institute of Molecular Pediatric Sciences
| | - Erik Johnson
- Department of Pediatrics and Institute of Molecular Pediatric Sciences
| | | | - Gregory Driessens
- Departments of Pathology and Medicine, Pritzker School of Medicine, University of Chicago, Chicago, IL 60637
| | | | - Akiko Koide
- Department of Biochemistry and Molecular Biology, and
| | - Cristiano G. Ponte
- Coordenação de Biotecnologia, Instituto Federal do Rio de Janeiro, Rio de Janeiro, 20270-021, Brazil; and
| | | | - Thomas F. Gajewski
- Departments of Pathology and Medicine, Pritzker School of Medicine, University of Chicago, Chicago, IL 60637
| | - Guilherme Suarez-Kurtz
- Divisão de Farmacologia, Instituto Nacional de Câncer, Rio de Janeiro, 20231-050, Brazil
| | - Shohei Koide
- Department of Biochemistry and Molecular Biology, and
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Kollewe A, Lau AY, Sullivan A, Benoît Roux, Goldstein SA. A structural model for K2P potassium channels based on 23 pairs of interacting sites and continuum electrostatics. J Gen Physiol 2009; 134:53-68. [PMID: 19564427 PMCID: PMC2712977 DOI: 10.1085/jgp.200910235] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 06/09/2009] [Indexed: 12/18/2022] Open
Abstract
K(2P)Ø, the two-pore domain potassium background channel that determines cardiac rhythm in Drosophila melanogaster, and its homologues that establish excitable membrane activity in mammals are of unknown structure. K(2P) subunits have two pore domains flanked by transmembrane (TM) spans: TM1-P1-TM2-TM3-P2-TM4. To establish spatial relationships in K(2P)Ø, we identified pairs of sites that display electrostatic compensation. Channels silenced by the addition of a charge in pore loop 1 (P1) or P2 were restored to function by countercharges at specific second sites. A three-dimensional homology model was determined using the crystal structure of K(V)1.2, effects of K(2P)Ø mutations to establish alignment, and compensatory charge-charge pairs. The model was refined and validated by continuum electrostatic free energy calculations and covalent linkage of introduced cysteines. K(2P) channels use two subunits arranged so that the P1 and P2 loops contribute to one pore, identical P loops face each other diagonally across the pore, and the channel complex has bilateral symmetry with a fourfold symmetric selectivity filter.
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Affiliation(s)
- Astrid Kollewe
- Institute for Molecular Pediatric Sciences, Department of Pediatrics, and Department of Biochemistry and Molecular Biology, The University of Chicago, Pritzker School of Medicine, Chicago, IL 60637
| | - Albert Y. Lau
- Institute for Molecular Pediatric Sciences, Department of Pediatrics, and Department of Biochemistry and Molecular Biology, The University of Chicago, Pritzker School of Medicine, Chicago, IL 60637
| | - Ashley Sullivan
- Institute for Molecular Pediatric Sciences, Department of Pediatrics, and Department of Biochemistry and Molecular Biology, The University of Chicago, Pritzker School of Medicine, Chicago, IL 60637
| | - Benoît Roux
- Institute for Molecular Pediatric Sciences, Department of Pediatrics, and Department of Biochemistry and Molecular Biology, The University of Chicago, Pritzker School of Medicine, Chicago, IL 60637
| | - Steve A.N. Goldstein
- Institute for Molecular Pediatric Sciences, Department of Pediatrics, and Department of Biochemistry and Molecular Biology, The University of Chicago, Pritzker School of Medicine, Chicago, IL 60637
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9
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Binz T, Bade S, Rummel A, Kollewe A, Alves J. Arg(362) and Tyr(365) of the botulinum neurotoxin type a light chain are involved in transition state stabilization. Biochemistry 2002; 41:1717-23. [PMID: 11827515 DOI: 10.1021/bi0157969] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The botulinum neurotoxin type A (BoNT/A) light chain (LC) acts as zinc endopeptidase. The X-ray structure of the toxin demonstrated that Zn(2+) is coordinated by His(222) and His(226) of the Zn(2+) binding motif HisGluXXHis and Glu(261), whereas Glu(223) coordinates the water molecule required for hydrolysis as the fourth ligand. Recent analysis of a cocrystal of the BoNT/B LC and its substrate synaptobrevin 2 suggested that Arg(362) and Tyr(365) of the homologous BoNT/A may be directly involved in catalysis. Their role and that of Glu(350) which is also found in the vicinity to the active site were analyzed by site-directed mutagenesis. Various replacements of Arg(362) and substitution of Tyr(365) with Phe resulted in 79- and 34-fold lower k(cat)/K(m) values, respectively. These changes were provoked by decreased catalytic rates (k(cat)) and not by alterations of ground state substrate binding as evidenced by largely unchanged K(d) and K(m) values. None of these mutations affected the overall secondary structure or zinc content of the LC. These findings suggest that the guanidino group of Arg(362) and the hydroxyl group of Tyr(365) together accomplish transition state stabilization as was proposed for thermolysin, being the prototypical member of the gluzincin superfamily of metalloproteases. Mutation of Glu(350) dramatically diminished the hydrolytic activity which must partly be attributed to an altered active site fine structure as demonstrated by an increased sensitivity toward heat-induced denaturing and a lower Zn(2+) binding affinity. Glu(350) apparently occupies a central position in the active site and presumably positions His(222) and Arg(362).
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Affiliation(s)
- Thomas Binz
- Department of Biochemistry and Department of Biophysical Chemistry, Medizinische Hochschule Hannover, Hannover, Germany.
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Wei S, Xu T, Ashery U, Kollewe A, Matti U, Antonin W, Rettig J, Neher E. Exocytotic mechanism studied by truncated and zero layer mutants of the C-terminus of SNAP-25. EMBO J 2000; 19:1279-89. [PMID: 10716928 PMCID: PMC305669 DOI: 10.1093/emboj/19.6.1279] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The highly conserved SNARE proteins, SNAP-25, syntaxin and synaptobrevin, form a tight ternary complex, which is essential for exocytosis. Crystallization of this complex revealed a four-helix bundle with an unusual hydrophilic layer (zero layer) in its center. In order to evaluate the role of this layer in different kinetic components of secretion, we used the Semliki Forest virus (SFV) system to infect adrenal chromaffin cells with SNAP-25 Q174L, a point mutant in the zero layer. Using combined flash photolysis of caged calcium and membrane capacitance measurements, we investigated its effect on the exocytotic burst and sustained phase of exocytosis with high time resolution. Cells expressing SNAP-25 Q174L displayed a selective reduction in the sustained phase, while the two components of the exocytotic burst remained unaffected. Furthermore, the exocytotic response to the second flash was significantly reduced, indicating a decrease in refilling kinetics. We therefore conclude that the zero layer is critical for the formation of SNARE complexes, but that it plays no role in the dynamic equilibrium between the two exocytosis-competent vesicle pools.
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Affiliation(s)
- S Wei
- Department of Membrane Biophysics, Max-Planck-Institute for Biophysical Chemistry, D-37077 Göttingen
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