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Porro A, Saponaro A, Castelli R, Introini B, Hafez Alkotob A, Ranjbari G, Enke U, Kusch J, Benndorf K, Santoro B, DiFrancesco D, Thiel G, Moroni A. A high affinity switch for cAMP in the HCN pacemaker channels. Nat Commun 2024; 15:843. [PMID: 38287019 PMCID: PMC10825183 DOI: 10.1038/s41467-024-45136-y] [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: 05/25/2023] [Accepted: 01/16/2024] [Indexed: 01/31/2024] Open
Abstract
Binding of cAMP to Hyperpolarization activated cyclic nucleotide gated (HCN) channels facilitates pore opening. It is unclear why the isolated cyclic nucleotide binding domain (CNBD) displays in vitro lower affinity for cAMP than the full-length channel in patch experiments. Here we show that HCN are endowed with an affinity switch for cAMP. Alpha helices D and E, downstream of the cyclic nucleotide binding domain (CNBD), bind to and stabilize the holo CNBD in a high affinity state. These helices increase by 30-fold cAMP efficacy and affinity measured in patch clamp and ITC, respectively. We further show that helices D and E regulate affinity by interacting with helix C of the CNBD, similarly to the regulatory protein TRIP8b. Our results uncover an intramolecular mechanism whereby changes in binding affinity, rather than changes in cAMP concentration, can modulate HCN channels, adding another layer to the complex regulation of their activity.
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Affiliation(s)
| | - Andrea Saponaro
- Department of Pharmacological and Biomolecular Sciences, University of Milan, Milano, Italy
| | | | - Bianca Introini
- Department of Biosciences, University of Milan, Milano, Italy
| | | | - Golnaz Ranjbari
- Department of Biosciences, University of Milan, Milano, Italy
| | - Uta Enke
- Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany
| | - Jana Kusch
- Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany
| | - Klaus Benndorf
- Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany
| | - Bina Santoro
- Department of Neuroscience, Zuckerman Institute, Columbia University, New York, NY, USA
| | | | - Gerhard Thiel
- Department of Biology, TU-Darmstadt, Darmstadt, Germany
| | - Anna Moroni
- Department of Biosciences, University of Milan, Milano, Italy.
- Institute of Biophysics Milan, Consiglio Nazionale delle Ricerche, Milano, Italy.
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2
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Yüksel S, Bonus M, Schwabe T, Pfleger C, Zimmer T, Enke U, Saß I, Gohlke H, Benndorf K, Kusch J. Uncoupling of Voltage- and Ligand-Induced Activation in HCN2 Channels by Glycine Inserts. Front Physiol 2022; 13:895324. [PMID: 36091400 PMCID: PMC9452628 DOI: 10.3389/fphys.2022.895324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Accepted: 06/20/2022] [Indexed: 11/24/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are tetramers that generate electrical rhythmicity in special brain neurons and cardiomyocytes. The channels are activated by membrane hyperpolarization. The binding of cAMP to the four available cyclic nucleotide-binding domains (CNBD) enhances channel activation. We analyzed in the present study the mechanism of how the effect of cAMP binding is transmitted to the pore domain. Our strategy was to uncouple the C-linker (CL) from the channel core by inserting one to five glycine residues between the S6 gate and the A′-helix (constructs 1G to 5G). We quantified in full-length HCN2 channels the resulting functional effects of the inserted glycines by current activation as well as the structural dynamics and statics using molecular dynamics simulations and Constraint Network Analysis. We show functionally that already in 1G the cAMP effect on activation is lost and that with the exception of 3G and 5G the concentration-activation relationships are shifted to depolarized voltages with respect to HCN2. The strongest effect was found for 4G. Accordingly, the activation kinetics were accelerated by all constructs, again with the strongest effect in 4G. The simulations reveal that the average residue mobility of the CL and CNBD domains is increased in all constructs and that the junction between the S6 and A′-helix is turned into a flexible hinge, resulting in a destabilized gate in all constructs. Moreover, for 3G and 4G, there is a stronger downward displacement of the CL-CNBD than in HCN2 and the other constructs, resulting in an increased kink angle between S6 and A′-helix, which in turn loosens contacts between the S4-helix and the CL. This is suggested to promote a downward movement of the S4-helix, similar to the effect of hyperpolarization. In addition, exclusively in 4G, the selectivity filter in the upper pore region and parts of the S4-helix are destabilized. The results provide new insights into the intricate activation of HCN2 channels.
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Affiliation(s)
- Sezin Yüksel
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Michele Bonus
- Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Tina Schwabe
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Christopher Pfleger
- Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Thomas Zimmer
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Uta Enke
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Inga Saß
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Holger Gohlke
- Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
- John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC), Institute of Biological Information Processing (IBI-7: Structural Biochemistry) and Institute of Bio- and Geosciences (IBG-4: Bioinformatics), Forschungszentrum Jülich GmbH, Jülich, Germany
- *Correspondence: Holger Gohlke, ; Klaus Benndorf, ; Jana Kusch,
| | - Klaus Benndorf
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
- *Correspondence: Holger Gohlke, ; Klaus Benndorf, ; Jana Kusch,
| | - Jana Kusch
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
- *Correspondence: Holger Gohlke, ; Klaus Benndorf, ; Jana Kusch,
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3
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Kondapuram M, Frieg B, Yüksel S, Schwabe T, Sattler C, Lelle M, Schweinitz A, Schmauder R, Benndorf K, Gohlke H, Kusch J. Functional and structural characterization of interactions between opposite subunits in HCN pacemaker channels. Commun Biol 2022; 5:430. [PMID: 35534535 PMCID: PMC9085832 DOI: 10.1038/s42003-022-03360-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 04/13/2022] [Indexed: 11/13/2022] Open
Abstract
Hyperpolarization-activated and cyclic nucleotide (HCN) modulated channels are tetrameric cation channels. In each of the four subunits, the intracellular cyclic nucleotide-binding domain (CNBD) is coupled to the transmembrane domain via a helical structure, the C-linker. High-resolution channel structures suggest that the C-linker enables functionally relevant interactions with the opposite subunit, which might be critical for coupling the conformational changes in the CNBD to the channel pore. We combined mutagenesis, patch-clamp technique, confocal patch-clamp fluorometry, and molecular dynamics (MD) simulations to show that residue K464 of the C-linker is relevant for stabilizing the closed state of the mHCN2 channel by forming interactions with the opposite subunit. MD simulations revealed that in the K464E channel, a rotation of the intracellular domain relative to the channel pore is induced, which is similar to the cAMP-induced rotation, weakening the autoinhibitory effect of the unoccupied CL-CNBD region. We suggest that this CL-CNBD rotation is considerably involved in activation-induced affinity increase but only indirectly involved in gate modulation. The adopted poses shown herein are in excellent agreement with previous structural results. Interactions between opposite subunits of HCN channels are relevant for stabilizing the auto-inhibited state of the channel. Like cAMP-binding, K464E-mutation breaks these interactions to favor a channel’s pre-activated state.
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Affiliation(s)
- Mahesh Kondapuram
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Benedikt Frieg
- John von Neumann-Institut für Computing (NIC), Jülich Supercomputing Centre (JSC), and Institut für Biologische Informationsprozesse (IBI-7: Strukturbiochemie), Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Sezin Yüksel
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Tina Schwabe
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Christian Sattler
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Marco Lelle
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Andrea Schweinitz
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Ralf Schmauder
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Klaus Benndorf
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany
| | - Holger Gohlke
- John von Neumann-Institut für Computing (NIC), Jülich Supercomputing Centre (JSC), and Institut für Biologische Informationsprozesse (IBI-7: Strukturbiochemie), Forschungszentrum Jülich GmbH, Jülich, Germany. .,Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany. .,Institut für Bio- und Geowissenschaften (IBG-4: Bioinformatik), Forschungszentrum Jülich GmbH, Jülich, Germany.
| | - Jana Kusch
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany.
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Lehmann J, Jørgensen ME, Fratz S, Müller HM, Kusch J, Scherzer S, Navarro-Retamal C, Mayer D, Böhm J, Konrad KR, Terpitz U, Dreyer I, Mueller TD, Sauer M, Hedrich R, Geiger D, Maierhofer T. Acidosis-induced activation of anion channel SLAH3 in the flooding-related stress response of Arabidopsis. Curr Biol 2021; 31:3575-3585.e9. [PMID: 34233161 DOI: 10.1016/j.cub.2021.06.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [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: 11/20/2020] [Revised: 02/03/2021] [Accepted: 06/08/2021] [Indexed: 10/20/2022]
Abstract
Plants, as sessile organisms, gained the ability to sense and respond to biotic and abiotic stressors to survive severe changes in their environments. The change in our climate comes with extreme dry periods but also episodes of flooding. The latter stress condition causes anaerobiosis-triggered cytosolic acidosis and impairs plant function. The molecular mechanism that enables plant cells to sense acidity and convey this signal via membrane depolarization was previously unknown. Here, we show that acidosis-induced anion efflux from Arabidopsis (Arabidopsis thaliana) roots is dependent on the S-type anion channel AtSLAH3. Heterologous expression of SLAH3 in Xenopus oocytes revealed that the anion channel is directly activated by a small, physiological drop in cytosolic pH. Acidosis-triggered activation of SLAH3 is mediated by protonation of histidine 330 and 454. Super-resolution microscopy analysis showed that the increase in cellular proton concentration switches SLAH3 from an electrically silent channel dimer into its active monomeric form. Our results show that, upon acidification, protons directly switch SLAH3 to its open configuration, bypassing kinase-dependent activation. Moreover, under flooding conditions, the stress response of Arabidopsis wild-type (WT) plants was significantly higher compared to SLAH3 loss-of-function mutants. Our genetic evidence of SLAH3 pH sensor function may guide the development of crop varieties with improved stress tolerance.
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Affiliation(s)
- Julian Lehmann
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Institute, Würzburg 97082, Germany; Department of Biotechnology and Biophysics, University of Würzburg, Biocenter -Am Hubland, Würzburg 97074, Germany
| | - Morten E Jørgensen
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Institute, Würzburg 97082, Germany
| | - Stefanie Fratz
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Institute, Würzburg 97082, Germany
| | - Heike M Müller
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Institute, Würzburg 97082, Germany
| | - Jana Kusch
- University Hospital Jena, Institute of Physiologie II, Kollegiengasse 9, Jena 07743, Germany
| | - Sönke Scherzer
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Institute, Würzburg 97082, Germany
| | - Carlos Navarro-Retamal
- Center for Bioinformatics, Simulation and Modeling (CBSM), Faculty of Engineering, Universidad de Talca, 2 Norte 685, Talca, Chile
| | - Dominik Mayer
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Institute, Würzburg 97082, Germany
| | - Jennifer Böhm
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Institute, Würzburg 97082, Germany
| | - Kai R Konrad
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Institute, Würzburg 97082, Germany
| | - Ulrich Terpitz
- Department of Biotechnology and Biophysics, University of Würzburg, Biocenter -Am Hubland, Würzburg 97074, Germany
| | - Ingo Dreyer
- Center for Bioinformatics, Simulation and Modeling (CBSM), Faculty of Engineering, Universidad de Talca, 2 Norte 685, Talca, Chile
| | - Thomas D Mueller
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Institute, Würzburg 97082, Germany
| | - Markus Sauer
- Department of Biotechnology and Biophysics, University of Würzburg, Biocenter -Am Hubland, Würzburg 97074, Germany
| | - Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Institute, Würzburg 97082, Germany.
| | - Dietmar Geiger
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Institute, Würzburg 97082, Germany
| | - Tobias Maierhofer
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Institute, Würzburg 97082, Germany.
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5
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Pfleger C, Kusch J, Kondapuram M, Schwabe T, Sattler C, Benndorf K, Gohlke H. Allosteric signaling in C-linker and cyclic nucleotide-binding domain of HCN2 channels. Biophys J 2021; 120:950-963. [PMID: 33515603 DOI: 10.1016/j.bpj.2021.01.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 01/04/2021] [Accepted: 01/19/2021] [Indexed: 12/22/2022] Open
Abstract
Opening of hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels is controlled by membrane hyperpolarization and binding of cyclic nucleotides to the tetrameric cyclic nucleotide-binding domain (CNBD), attached to the C-linker (CL) disk. Confocal patch-clamp fluorometry revealed pronounced cooperativity of ligand binding among protomers. However, by which pathways allosteric signal transmission occurs remained elusive. Here, we investigate how changes in the structural dynamics of the CL-CNBD of mouse HCN2 upon cAMP binding relate to inter- and intrasubunit signal transmission. Applying a rigidity-theory-based approach, we identify two intersubunit and one intrasubunit pathways that differ in allosteric coupling strength between cAMP-binding sites or toward the CL. These predictions agree with results from electrophysiological and patch-clamp fluorometry experiments. Our results map out distinct routes within the CL-CNBD that modulate different cAMP-binding responses in HCN2 channels. They signify that functionally relevant submodules may exist within and across structurally discernable subunits in HCN channels.
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Affiliation(s)
- Christopher Pfleger
- Mathematisch-Naturwissenschaftliche Fakultät, Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Jana Kusch
- Institute of Physiology II, Jena University Hospital, Jena, Germany
| | | | - Tina Schwabe
- Institute of Physiology II, Jena University Hospital, Jena, Germany
| | | | - Klaus Benndorf
- Institute of Physiology II, Jena University Hospital, Jena, Germany
| | - Holger Gohlke
- Mathematisch-Naturwissenschaftliche Fakultät, Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany; John von Neumann Institute for Computing, Jülich Supercomputing Centre, and Institute of Biological Information Processing (IBI-7, Structural Biochemistry), Forschungszentrum Jülich, Jülich, Germany.
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6
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Leypold T, Bonus M, Spiegelhalter F, Schwede F, Schwabe T, Gohlke H, Kusch J. N 6-modified cAMP derivatives that activate protein kinase A also act as full agonists of murine HCN2 channels. J Biol Chem 2019; 294:17978-17987. [PMID: 31615893 DOI: 10.1074/jbc.ra119.010246] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 10/15/2019] [Indexed: 11/06/2022] Open
Abstract
cAMP acts as a second messenger in many cellular processes. Three protein types mainly mediate cAMP-induced effects: PKA, exchange protein directly activated by cAMP (Epac), and cyclic nucleotide-modulated channels (cyclic nucleotide-gated or hyperpolarization-activated and cyclic nucleotide-modulated (HCN) channels). Discrimination among these cAMP signaling pathways requires specific targeting of only one protein. Previously, cAMP modifications at position N 6 of the adenine ring (PKA) and position 2'-OH of the ribose (Epac) have been used to produce target-selective compounds. However, cyclic nucleotide-modulated ion channels were usually outside of the scope of these previous studies. These channels are widely distributed, so possible channel cross-activation by PKA- or Epac-selective agonists warrants serious consideration. Here we demonstrate the agonistic effects of three PKA-selective cAMP derivatives, N 6-phenyladenosine-3',5'-cyclic monophosphate (N 6-Phe-cAMP), N 6-benzyladenosine-3',5'-cyclic monophosphate (N 6-Bn-cAMP), and N 6-benzoyl-adenosine-3',5'-cyclic monophosphate (N 6-Bnz-cAMP), on murine HCN2 pacemaker channels. Electrophysiological characterization in Xenopus oocytes revealed that these derivatives differ in apparent affinities depending on the modification type but that their efficacy and effects on HCN2 activation kinetics are similar to those of cAMP. Docking experiments suggested a pivotal role of Arg-635 at the entrance of the binding pocket in HCN2, either causing stabilizing cation-π interactions with the aromatic ring in N 6-Phe-cAMP or N 6-Bn-cAMP or a steric clash with the aromatic ring in N 6-Bnz-cAMP. A reduced apparent affinity of N 6-Phe-cAMP toward the variants R635A and R635E strengthened that notion. We conclude that some PKA activators also effectively activate HCN2 channels. Hence, when studying PKA-mediated cAMP signaling with cAMP derivatives in a native environment, activation of HCN channels should be considered.
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Affiliation(s)
- Tim Leypold
- Friedrich Schiller University, University Hospital Jena, Institute of Physiology II, Kollegiengasse 9, 07743 Jena, Germany
| | - Michele Bonus
- Institute for Pharmaceutical and Medical Chemistry, Heinrich Heine University, Universitätsstraβe 1, 40225 Düsseldorf, Germany
| | - Felix Spiegelhalter
- Friedrich Schiller University, University Hospital Jena, Institute of Physiology II, Kollegiengasse 9, 07743 Jena, Germany
| | | | - Tina Schwabe
- Friedrich Schiller University, University Hospital Jena, Institute of Physiology II, Kollegiengasse 9, 07743 Jena, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medical Chemistry, Heinrich Heine University, Universitätsstraβe 1, 40225 Düsseldorf, Germany.,John von Neumann Institute for Computing, Jülich Supercomputing Centre and Institute for Complex Systems - Structural Biochemistry (ICS 6), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Jana Kusch
- Friedrich Schiller University, University Hospital Jena, Institute of Physiology II, Kollegiengasse 9, 07743 Jena, Germany
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7
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Yüksel S, Kondapuram M, Schwabe T, Bonus M, Gohlke H, Schmauder R, Kusch J, Benndorf K. Uncoupling the cAMP Binding Domain from the Channel Gate in HCN2 Channels. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.618] [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: 10/27/2022] Open
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8
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Kondapuram M, Yüksel S, Schwabe T, Frieg B, Gohlke H, Schmauder R, Benndorf K, Kusch J. Opposing Subunits Interact to Stabilize the Closed State in HCN2 Channels. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.617] [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: 11/29/2022] Open
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9
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Ando T, Bhamidimarri SP, Brending N, Colin-York H, Collinson L, De Jonge N, de Pablo PJ, Debroye E, Eggeling C, Franck C, Fritzsche M, Gerritsen H, Giepmans BNG, Grunewald K, Hofkens J, Hoogenboom JP, Janssen KPF, Kaufman R, Klumpermann J, Kurniawan N, Kusch J, Liv N, Parekh V, Peckys DB, Rehfeldt F, Reutens DC, Roeffaers MBJ, Salditt T, Schaap IAT, Schwarz US, Verkade P, Vogel MW, Wagner R, Winterhalter M, Yuan H, Zifarelli G. The 2018 correlative microscopy techniques roadmap. J Phys D Appl Phys 2018; 51:443001. [PMID: 30799880 PMCID: PMC6372154 DOI: 10.1088/1361-6463/aad055] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 06/14/2018] [Accepted: 07/01/2018] [Indexed: 05/19/2023]
Abstract
Developments in microscopy have been instrumental to progress in the life sciences, and many new techniques have been introduced and led to new discoveries throughout the last century. A wide and diverse range of methodologies is now available, including electron microscopy, atomic force microscopy, magnetic resonance imaging, small-angle x-ray scattering and multiple super-resolution fluorescence techniques, and each of these methods provides valuable read-outs to meet the demands set by the samples under study. Yet, the investigation of cell development requires a multi-parametric approach to address both the structure and spatio-temporal organization of organelles, and also the transduction of chemical signals and forces involved in cell-cell interactions. Although the microscopy technologies for observing each of these characteristics are well developed, none of them can offer read-out of all characteristics simultaneously, which limits the information content of a measurement. For example, while electron microscopy is able to disclose the structural layout of cells and the macromolecular arrangement of proteins, it cannot directly follow dynamics in living cells. The latter can be achieved with fluorescence microscopy which, however, requires labelling and lacks spatial resolution. A remedy is to combine and correlate different readouts from the same specimen, which opens new avenues to understand structure-function relations in biomedical research. At the same time, such correlative approaches pose new challenges concerning sample preparation, instrument stability, region of interest retrieval, and data analysis. Because the field of correlative microscopy is relatively young, the capabilities of the various approaches have yet to be fully explored, and uncertainties remain when considering the best choice of strategy and workflow for the correlative experiment. With this in mind, the Journal of Physics D: Applied Physics presents a special roadmap on the correlative microscopy techniques, giving a comprehensive overview from various leading scientists in this field, via a collection of multiple short viewpoints.
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Affiliation(s)
- Toshio Ando
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan
| | | | | | - H Colin-York
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, OX3 9DS Oxford, United Kingdom
| | | | - Niels De Jonge
- INM-Leibniz Institute for New Materials, 66123 Saarbrücken, Germany
- Saarland University, 66123 Saarbrücken, Germany
| | - P J de Pablo
- Dpto. Física de la Materia Condensada Universidad Autónoma de Madrid 28049, Madrid, Spain
- Instituto de Física de la Materia Condensada IFIMAC, Universidad Autónoma de Madrid 28049, Madrid, Spain
| | - Elke Debroye
- KU Leuven, Department of Chemistry, B-3001 Heverlee, Belgium
| | - Christian Eggeling
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, OX3 9DS Oxford, United Kingdom
- Institute of Applied Optics, Friedrich-Schiller University, Jena, Germany
- Leibniz Institute of Photonic Technology (IPHT), Jena, Germany
| | - Christian Franck
- Department of Mechanical Engineering, University of Wisconsin-Madison, 1513 University Ave, Madison, WI 53706, United States of America
| | - Marco Fritzsche
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, OX3 9DS Oxford, United Kingdom
- Kennedy Institute for Rheumatology, University of Oxford, Oxford, United Kingdom
| | - Hans Gerritsen
- Debye Institute, Utrecht University, Utrecht, Netherlands
| | - Ben N G Giepmans
- Department of Cell Biology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - Kay Grunewald
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
- Centre of Structural Systems Biology Hamburg and University of Hamburg, Hamburg, Germany
- Heinrich-Pette-Institute, Leibniz Institute of Virology, Hamburg, Germany
| | - Johan Hofkens
- KU Leuven, Department of Chemistry, B-3001 Heverlee, Belgium
| | | | | | - Rainer Kaufman
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
- Centre of Structural Systems Biology Hamburg and University of Hamburg, Hamburg, Germany
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Judith Klumpermann
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584CX Utrecht, Netherlands
| | - Nyoman Kurniawan
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | | | - Nalan Liv
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Heidelberglaan 100, 3584CX Utrecht, Netherlands
| | - Viha Parekh
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Diana B Peckys
- Faculty of Medicine, Saarland University, 66421 Homburg, Germany
| | - Florian Rehfeldt
- University of Göttingen, Third Institute of Physics-Biophysics, 37077 Göttingen, Germany
| | - David C Reutens
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | | | - Tim Salditt
- University of Göttingen, Institute for X-Ray Physics, 37077 Göttingen, Germany
| | - Iwan A T Schaap
- SmarAct GmbH, Schütte-Lanz-Str. 9, D-26135 Oldenburg, Germany
| | - Ulrich S Schwarz
- Institute for Theoretical Physics and BioQuant, Heidelberg University, Heidelberg, Germany
| | - Paul Verkade
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Michael W Vogel
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Richard Wagner
- Department of Life Sciences & Chemistry, Jacobs University, Bremen, Germany
| | | | - Haifeng Yuan
- KU Leuven, Department of Chemistry, B-3001 Heverlee, Belgium
| | - Giovanni Zifarelli
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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10
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Nache V, Wongsamitkul N, Kusch J, Zimmer T, Schwede F, Benndorf K. Erratum: Corrigendum: Deciphering the function of the CNGB1b subunit in olfactory CNG channels. Sci Rep 2018; 8:47000. [PMID: 29952375 PMCID: PMC6021846 DOI: 10.1038/srep47000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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11
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Sunkara MR, Schwabe T, Ehrlich G, Kusch J, Benndorf K. All four subunits of HCN2 channels contribute to the activation gating in an additive but intricate manner. J Gen Physiol 2018; 150:1261-1271. [PMID: 29959170 PMCID: PMC6122924 DOI: 10.1085/jgp.201711935] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 04/25/2018] [Accepted: 06/14/2018] [Indexed: 01/25/2023] Open
Abstract
HCN pacemaker channels are dually gated by hyperpolarizing voltages and cyclic nucleotide binding. Sunkara et al. show that each of the four binding sites promotes channel opening, most likely by exerting a turning momentum on the tetrameric intracellular gating ring. Hyperpolarization-activated cyclic nucleotide–modulated (HCN) channels are tetramers that elicit electrical rhythmicity in specialized brain neurons and cardiomyocytes. The channels are dually activated by voltage and binding of cyclic adenosine monophosphate (cAMP) to their four cyclic nucleotide-binding domains (CNBDs). Here we analyze the effects of cAMP binding to different concatemers of HCN2 channel subunits, each having a defined number of functional CNBDs. We show that each liganded CNBD promotes channel activation in an additive manner and that, in the special case of two functional CNBDs, functionality does not depend on the arrangement of the subunits. Correspondingly, the reverse process of deactivation is slowed by progressive liganding, but only if four and three ligands as well as two ligands in trans position (opposite to each other) are bound. In contrast, two ligands bound in cis positions (adjacent to each other) and a single bound ligand do not affect channel deactivation. These results support an activation mechanism in which each single liganded CNBD causes a turning momentum on the tetrameric ring-like structure formed by all four CNBDs and that at least two liganded subunits in trans positions are required to maintain activation.
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Affiliation(s)
- Mallikarjuna Rao Sunkara
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Tina Schwabe
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Gunter Ehrlich
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Jana Kusch
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Klaus Benndorf
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
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12
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Rao Sunkara M, Kusch J, Benndorf K. Role of Individual Camp Binding Sites on Relieving the Autoinhibition in HCN Channels. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.2256] [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: 11/28/2022] Open
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13
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Thon S, Schulz E, Kusch J, Benndorf K. Conformational Flip of Nonactivated HCN2 Channel Subunits Evoked by Cyclic Nucleotides. Biophys J 2016; 109:2268-76. [PMID: 26636938 PMCID: PMC4675818 DOI: 10.1016/j.bpj.2015.08.054] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 08/21/2015] [Accepted: 08/24/2015] [Indexed: 12/11/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are tetrameric proteins that evoke electrical rhythmicity in specialized neurons and cardiomyocytes. The channels are activated by hyperpolarizing voltage but are also receptors for the intracellular ligand adenosine-3',5'-cyclic monophosphate (cAMP) that enhances activation but is unable to activate the channels alone. Using fcAMP, a fluorescent derivative of cAMP, we analyzed the effect of ligand binding on HCN2 channels not preactivated by voltage. We identified a conformational flip of the channel as an intermediate state following the ligand binding and quantified it kinetically. Globally fitting the time courses of ligand binding and unbinding revealed modest cooperativity among the subunits in the conformational flip. The intensity of this cooperativity, however, was only moderate compared to channels preactivated by hyperpolarizing voltage. These data provide kinetic information about conformational changes proceeding in nonactivated HCN2 channels when cAMP binds. Moreover, our approach bears potential for analyzing the function of any other membrane receptor if a potent fluorescent ligand is available.
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Affiliation(s)
- Susanne Thon
- Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany
| | - Eckhard Schulz
- Fachhochschule Schmalkalden, Fakultät Elektrotechnik, Blechhammer, Schmalkalden, Germany
| | - Jana Kusch
- Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany
| | - Klaus Benndorf
- Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany.
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14
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Nache V, Wongsamitkul N, Kusch J, Zimmer T, Schwede F, Benndorf K. Deciphering the function of the CNGB1b subunit in olfactory CNG channels. Sci Rep 2016; 6:29378. [PMID: 27405959 PMCID: PMC4942689 DOI: 10.1038/srep29378] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 06/15/2016] [Indexed: 11/29/2022] Open
Abstract
Olfactory cyclic nucleotide-gated (CNG) ion channels are key players in the signal transduction cascade of olfactory sensory neurons. The second messengers cAMP and cGMP directly activate these channels, generating a depolarizing receptor potential. Olfactory CNG channels are composed of two CNGA2 subunits and two modulatory subunits, CNGA4, and CNGB1b. So far the exact role of the modulatory subunits for channel activation is not fully understood. By measuring ligand binding and channel activation simultaneously, we show that in functional heterotetrameric channels not only the CNGA2 subunits and the CNGA4 subunit but also the CNGB1b subunit binds cyclic nucleotides and, moreover, also alone translates this signal to open the pore. In addition, we show that the CNGB1b subunit is the most sensitive subunit in a heterotetrameric channel to cyclic nucleotides and that it accelerates deactivation to a similar extent as does the CNGA4 subunit. In conclusion, the CNGB1b subunit participates in ligand-gated activation of olfactory CNG channels and, particularly, contributes to rapid termination of odorant signal in an olfactory sensory neuron.
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Affiliation(s)
- Vasilica Nache
- Institute of Physiology II, Jena University Hospital, Friedrich Schiller University Jena, D-07743 Jena, Germany
| | - Nisa Wongsamitkul
- Institute of Physiology II, Jena University Hospital, Friedrich Schiller University Jena, D-07743 Jena, Germany
| | - Jana Kusch
- Institute of Physiology II, Jena University Hospital, Friedrich Schiller University Jena, D-07743 Jena, Germany
| | - Thomas Zimmer
- Institute of Physiology II, Jena University Hospital, Friedrich Schiller University Jena, D-07743 Jena, Germany
| | - Frank Schwede
- BIOLOG Life Science Institute, Flughafendamm 9A, D-28199 Bremen, Germany
| | - Klaus Benndorf
- Institute of Physiology II, Jena University Hospital, Friedrich Schiller University Jena, D-07743 Jena, Germany
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15
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Kesters D, Brams M, Nys M, Wijckmans E, Spurny R, Voets T, Tytgat J, Kusch J, Ulens C. Structure of the SthK carboxy-terminal region reveals a gating mechanism for cyclic nucleotide-modulated ion channels. PLoS One 2015; 10:e0116369. [PMID: 25625648 PMCID: PMC4308110 DOI: 10.1371/journal.pone.0116369] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Accepted: 12/09/2014] [Indexed: 11/19/2022] Open
Abstract
Cyclic nucleotide-sensitive ion channels are molecular pores that open in response to cAMP or cGMP, which are universal second messengers. Binding of a cyclic nucleotide to the carboxyterminal cyclic nucleotide binding domain (CNBD) of these channels is thought to cause a conformational change that promotes channel opening. The C-linker domain, which connects the channel pore to this CNBD, plays an important role in coupling ligand binding to channel opening. Current structural insight into this mechanism mainly derives from X-ray crystal structures of the C-linker/CNBD from hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels. However, these structures reveal little to no conformational changes upon comparison of the ligand-bound and unbound form. In this study, we take advantage of a recently identified prokaryote ion channel, SthK, which has functional properties that strongly resemble cyclic nucleotide-gated (CNG) channels and is activated by cAMP, but not by cGMP. We determined X-ray crystal structures of the C-linker/CNBD of SthK in the presence of cAMP or cGMP. We observe that the structure in complex with cGMP, which is an antagonist, is similar to previously determined HCN channel structures. In contrast, the structure in complex with cAMP, which is an agonist, is in a more open conformation. We observe that the CNBD makes an outward swinging movement, which is accompanied by an opening of the C-linker. This conformation mirrors the open gate structures of the Kv1.2 channel or MthK channel, which suggests that the cAMP-bound C-linker/CNBD from SthK represents an activated conformation. These results provide a structural framework for better understanding cyclic nucleotide modulation of ion channels, including HCN and CNG channels.
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Affiliation(s)
- Divya Kesters
- Laboratory of Structural Neurobiology, KU Leuven, Herestraat 49, PB601, Leuven, B-3000, Belgium
| | - Marijke Brams
- Laboratory of Structural Neurobiology, KU Leuven, Herestraat 49, PB601, Leuven, B-3000, Belgium
| | - Mieke Nys
- Laboratory of Structural Neurobiology, KU Leuven, Herestraat 49, PB601, Leuven, B-3000, Belgium
| | - Eveline Wijckmans
- Laboratory of Structural Neurobiology, KU Leuven, Herestraat 49, PB601, Leuven, B-3000, Belgium
| | - Radovan Spurny
- Laboratory of Structural Neurobiology, KU Leuven, Herestraat 49, PB601, Leuven, B-3000, Belgium
| | - Thomas Voets
- Laboratory of Ion Channel Research, KU Leuven, Herestraat 49, PB802, Leuven, B-3000, Belgium
| | - Jan Tytgat
- Laboratory of Toxicology and Pharmacology, KU Leuven, Herestraat 49, PB922, Leuven, B-3000, Belgium
| | - Jana Kusch
- University Hospital Jena, Institute of Physiologie II, Kollegiengasse 9, 07743, Jena, Germany
| | - Chris Ulens
- Laboratory of Structural Neurobiology, KU Leuven, Herestraat 49, PB601, Leuven, B-3000, Belgium
- * E-mail:
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16
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Ladha A, Benndorf K, Kusch J. Stepchild Nicotine: Effect of the Name-Giving Agonist on Muscle-Type Nicotinic Acetylcholine Receptor. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.2350] [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: 10/24/2022] Open
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17
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Kusch J, Zifarelli G. Patch-clamp fluorometry: electrophysiology meets fluorescence. Biophys J 2014; 106:1250-7. [PMID: 24655500 DOI: 10.1016/j.bpj.2014.02.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 12/23/2013] [Accepted: 02/06/2014] [Indexed: 12/26/2022] Open
Abstract
Ion channels and transporters are membrane proteins whose functions are driven by conformational changes. Classical biophysical techniques provide insight into either the structure or the function of these proteins, but a full understanding of their behavior requires a correlation of both these aspects in time. Patch-clamp and voltage-clamp fluorometry combine spectroscopic and electrophysiological techniques to simultaneously detect conformational changes and ionic currents across the membrane. Since its introduction, patch-clamp fluorometry has been responsible for invaluable advances in our knowledge of ion channel biophysics. Over the years, the technique has been applied to many different ion channel families to address several biophysical questions with a variety of spectroscopic approaches and electrophysiological configurations. This review illustrates the strength and the flexibility of patch-clamp fluorometry, demonstrating its potential as a tool for future research.
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Affiliation(s)
- Jana Kusch
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany.
| | - Giovanni Zifarelli
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy.
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18
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Schmidt A, Lenzig P, Oslender-Bujotzek A, Kusch J, Dias Lucas S, Gründer S, Wiemuth D. The bile acid-sensitive ion channel (BASIC) is activated by alterations of its membrane environment. PLoS One 2014; 9:e111549. [PMID: 25360526 PMCID: PMC4216111 DOI: 10.1371/journal.pone.0111549] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 10/06/2014] [Indexed: 01/26/2023] Open
Abstract
The bile acid-sensitive ion channel (BASIC) is a member of the DEG/ENaC family of ion channels. Channels of this family are characterized by a common structure, their physiological functions and modes of activation, however, are diverse. Rat BASIC is expressed in brain, liver and intestinal tract and activated by bile acids. The physiological function of BASIC and its mechanism of bile acid activation remain a puzzle. Here we addressed the question whether amphiphilic bile acids activate BASIC by directly binding to the channel or indirectly by altering the properties of the surrounding membrane. We show that membrane-active substances other than bile acids also affect the activity of BASIC and that activation by bile acids and other membrane-active substances is non-additive, suggesting that BASIC is sensitive for changes in its membrane environment. Furthermore based on results from chimeras between BASIC and ASIC1a, we show that the extracellular and the transmembrane domains are important for membrane sensitivity.
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Affiliation(s)
- Axel Schmidt
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Pia Lenzig
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | | | - Jana Kusch
- Institute of Physiology II, University Hospital Jena, Friedrich-Schiller-University Jena, Jena, Germany
| | - Susana Dias Lucas
- Instituto de Investigação do Medicamento (iMed.ULisboa), Faculdade de Farmácia, Universidade de Lisboa, Lisboa, Portugal
| | - Stefan Gründer
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Dominik Wiemuth
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
- * E-mail:
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19
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Kusch J, Brams M, Ulens C. A Family of HCN Channel Homologs in Bacteria. Biophys J 2014. [DOI: 10.1016/j.bpj.2013.11.4181] [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: 11/30/2022] Open
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20
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Benndorf K, Kusch J, Schulz E. Probability Fluxes and Transition Paths in a Markovian Model Describing Complex Subunit Cooperativity in HCN2 Channels. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.1569] [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: 11/15/2022] Open
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21
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Kusch J, Rose J, Fischer T, Thon S, Benndorf K. Voltage- and Camp-Dependent Gating in Heterotetrameric HCN2/4-Pacemaker Channels. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.1564] [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: 10/27/2022] Open
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22
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Benndorf K, Kusch J, Schulz E. Probability fluxes and transition paths in a Markovian model describing complex subunit cooperativity in HCN2 channels. PLoS Comput Biol 2012; 8:e1002721. [PMID: 23093920 PMCID: PMC3475657 DOI: 10.1371/journal.pcbi.1002721] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Accepted: 08/16/2012] [Indexed: 01/15/2023] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are voltage-gated tetrameric cation channels that generate electrical rhythmicity in neurons and cardiomyocytes. Activation can be enhanced by the binding of adenosine-3',5'-cyclic monophosphate (cAMP) to an intracellular cyclic nucleotide binding domain. Based on previously determined rate constants for a complex Markovian model describing the gating of homotetrameric HCN2 channels, we analyzed probability fluxes within this model, including unidirectional probability fluxes and the probability flux along transition paths. The time-dependent probability fluxes quantify the contributions of all 13 transitions of the model to channel activation. The binding of the first, third and fourth ligand evoked robust channel opening whereas the binding of the second ligand obstructed channel opening similar to the empty channel. Analysis of the net probability fluxes in terms of the transition path theory revealed pronounced hysteresis for channel activation and deactivation. These results provide quantitative insight into the complex interaction of the four structurally equal subunits, leading to non-equality in their function.
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Affiliation(s)
- Klaus Benndorf
- Friedrich-Schiller-Universität Jena, Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany.
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23
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Nache V, Zimmer T, Wongsamitkul N, Schmauder R, Kusch J, Reinhardt L, Bönigk W, Seifert R, Biskup C, Schwede F, Benndorf K. Differential regulation by cyclic nucleotides of the CNGA4 and CNGB1b subunits in olfactory cyclic nucleotide-gated channels. Sci Signal 2012; 5:ra48. [PMID: 22786723 DOI: 10.1126/scisignal.2003110] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Olfactory cyclic nucleotide-gated (CNG) ion channels are essential contributors to signal transduction of olfactory sensory neurons. The activity of the channels is controlled by the cyclic nucleotides guanosine 3',5'-monophosphate (cGMP) and adenosine 3',5'-monophosphate (cAMP). The olfactory CNG channels are composed of two CNGA2 subunits, one CNGA4 and one CNGB1b subunit, each containing a cyclic nucleotide-binding domain. Using patch-clamp fluorometry, we measured ligand binding and channel activation simultaneously and showed that cGMP activated olfactory CNG channels not only by binding to the two CNGA2 subunits but also by binding to the CNGA4 subunit. In a channel in which the CNGA2 subunits were compromised for ligand binding, cGMP binding to CNGA4 was sufficient to partly activate the channel. In contrast, in heterotetrameric channels, the CNGB1b subunit did not bind cGMP, but channels with this subunit showed activation by cAMP. Thus, the modulatory subunits participate actively in translating ligand binding to activation of heterotetrameric olfactory CNG channels and enable the channels to differentiate between cyclic nucleotides.
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Affiliation(s)
- Vasilica Nache
- Institute of Physiology II, University Hospital Jena, Friedrich-Schiller-University Jena, D-07740 Jena, Germany
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24
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Kusch J, Thon S, Schulz E, Biskup C, Nache V, Zimmer T, Seifert R, Schwede F, Benndorf K. Functional Dimeric Organization of the Tetrameric HCN2 Pacemaker Channel. Biophys J 2012. [DOI: 10.1016/j.bpj.2011.11.726] [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: 11/30/2022] Open
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25
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Benndorf K, Kusch J, Thon S, Schulz E. How to Define Cooperativity for the Ligand-Induced Gating of HCN2 Channels? Biophys J 2012. [DOI: 10.1016/j.bpj.2011.11.718] [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: 11/30/2022] Open
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26
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Kusch J, Thon S, Schulz E, Biskup C, Nache V, Zimmer T, Seifert R, Schwede F, Benndorf K. How subunits cooperate in cAMP-induced activation of homotetrameric HCN2 channels. Nat Chem Biol 2011; 8:162-9. [PMID: 22179066 DOI: 10.1038/nchembio.747] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Accepted: 10/06/2011] [Indexed: 02/03/2023]
Abstract
Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are tetrameric membrane proteins that generate electrical rhythmicity in specialized neurons and cardiomyocytes. The channels are primarily activated by voltage but are receptors as well, binding the intracellular ligand cyclic AMP. The molecular mechanism of channel activation is still unknown. Here we analyze the complex activation mechanism of homotetrameric HCN2 channels by confocal patch-clamp fluorometry and kinetically quantify all ligand binding steps and closed-open isomerizations of the intermediate states. For the binding affinity of the second, third and fourth ligand, our results suggest pronounced cooperativity in the sequence positive, negative and positive, respectively. This complex interaction of the subunits leads to a preferential stabilization of states with zero, two or four ligands and suggests a dimeric organization of the activation process: within the dimers the cooperativity is positive, whereas it is negative between the dimers.
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Affiliation(s)
- Jana Kusch
- Institut für Physiologie II, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
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27
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Kusch J, Schmauder R, Biskup C, Nache V, Benndorf K. Analysis and Minimization of Ligand Concentration Errors at the Internal Face of Excised Patches. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.775] [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: 11/30/2022] Open
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28
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Nache V, Zimmer T, Kusch J, Biskup C, Schmauder R, Schulz E, Seifert R, Bönigk W, Schwede F, Benndorf K. Differential Contribution of the Olfactory CNG Channel Subunits to the Activation Process. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.769] [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: 11/24/2022] Open
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29
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Kusch J, Zimmer T, Holschuh J, Biskup C, Schulz E, Nache V, Benndorf K. Role of the S4-S5 linker in CNG channel activation. Biophys J 2011; 99:2488-96. [PMID: 20959089 DOI: 10.1016/j.bpj.2010.07.041] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2010] [Revised: 06/22/2010] [Accepted: 07/19/2010] [Indexed: 10/18/2022] Open
Abstract
Cyclic nucleotide-gated (CNG) channels mediate sensory signal transduction in retinal and olfactory cells. The channels are activated by the binding of cyclic nucleotides to a cyclic nucleotide-binding domain (CNBD) in the C-terminus that is located at the intracellular side. The molecular events translating the ligand binding to the pore opening are still unknown. We investigated the role of the S4-S5 linker in the activation process by quantifying its interaction with other intracellular regions. To this end, we constructed chimeric channels in which the N-terminus, the S4-S5 linker, the C-linker, and the CNBD of the retinal CNGA1 subunit were systematically replaced by the respective regions of the olfactory CNGA2 subunit. Macroscopic concentration-response relations were analyzed, yielding the apparent affinity to cGMP and the Hill coefficient. The degree of functional coupling of intracellular regions in the activation gating was determined by thermodynamic double-mutant cycle analysis. We observed that all four intracellular regions, including the relatively short S4-S5 linker, are involved in controlling the apparent affinity of the channel to cGMP and, moreover, in determining the degree of cooperativity between the subunits, as derived from the Hill coefficient. The interaction energies reveal an interaction of the S4-S5 linker with both the N-terminus and the C-linker, but no interaction with the CNBD.
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Affiliation(s)
- Jana Kusch
- Universitätsklinikum Jena, Institut für Physiologie II, Germany
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30
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Neugebauer J, Kistler F, Kistler S, Züdorf G, Freyer D, Ritter L, Dreiseidler T, Kusch J, Zöller JE. CAD/CAM-produced surgical guides: Optimizing the treatment workflow. Int J Comput Dent 2011; 14:93-103. [PMID: 21877375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The increased availability of devices for 3D radiological diagnosis allows the more frequent use of CAD/CAM-produced surgical guides for implant placement. The conventional workflow requires a complex logistic chain which is time-consuming and costly. In a pilot study, the workflow of directly milled surgical guides was evaluated. These surgical guides were designed based on the fusion of an optical impression and the radiological data. The clinical use showed that the surgical guides could be accurately placed on the residual dentition without tipping movements. The conventional surgical guides were used as a control for the manual check of the deviation of the implant axis. The direct transfer of the digital planning data allows the fabrication of surgical guides in an external center without the need of physical transport, which reduces the logistic effort and expense of the central fabrication of surgical guides.
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Affiliation(s)
- J Neugebauer
- Department of Craniomaxillofacial and Plastic Surgery, University of Cologne, Germany.
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31
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Kusch J, Biskup C, Thon S, Schulz E, Nache V, Zimmer T, Schwede F, Benndorf K. Interdependence of receptor activation and ligand binding in HCN2 pacemaker channels. Neuron 2010; 67:75-85. [PMID: 20624593 DOI: 10.1016/j.neuron.2010.05.022] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/25/2010] [Indexed: 10/19/2022]
Abstract
HCN pacemaker channels are tetramers mediating rhythmicity in neuronal and cardiac cells. The activity of these channels is controlled by both membrane voltage and the ligand cAMP, binding to each of the four channel subunits. The molecular mechanism underlying channel activation and the relationship between the two activation stimuli are still unknown. Using patch-clamp fluorometry and a fluorescent cAMP analog, we show that full ligand-induced activation appears already with only two ligands bound to the tetrameric channel. Kinetic analysis of channel activation and ligand binding suggests direct interaction between the voltage sensor and the cyclic nucleotide-binding domain, bypassing the pore. By exploiting the duality of activation in HCN2 channels by voltage and ligand binding, we quantify the increase of the binding affinity and overall free energy for binding upon channel activation, proving thus the principle of reciprocity between ligand binding and conformational change in a receptor protein.
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Affiliation(s)
- Jana Kusch
- Institut für Physiologie II, Universitätsklinikum Jena, Jena, Germany
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32
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Kusch J, Thon S, Biskup C, Schulz E, Zimmer T, Benndorf K. Voltage Gated Trapping of fcAMP in HCN2 Channels. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.3881] [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: 11/25/2022] Open
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33
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Kusch J, Zimmer T, Holschuh J, Biskup C, Schulz E, Nache V, Benndorf K. Interaction Energies between Intracellular Regions in CNG Channel Activation. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.3875] [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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34
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Nache V, Kusch J, Biskup C, Zimmer T, Schulz E, Hagen V, Schwede F, Bönigk W, Benndorf K. Ligand Binding and Activation Gating in CNGA2A4B1b Channels. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.3872] [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: 11/26/2022] Open
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35
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Biskup C, Kusch J, Schulz E, Nache V, Schwede F, Lehmann F, Hagen V, Benndorf K. Relating ligand binding to activation gating in CNGA2 channels. Nature 2007; 446:440-3. [PMID: 17322905 DOI: 10.1038/nature05596] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2006] [Accepted: 01/12/2007] [Indexed: 11/09/2022]
Abstract
Cyclic nucleotide-gated (CNG) ion channels mediate sensory signal transduction in photoreceptors and olfactory cells. Structurally, CNG channels are heterotetramers composed of either two or three homologue subunits. Although it is well established that activation is a cooperative process of these subunits, it remains unknown whether the cooperativity is generated by the ligand binding, the gating, or both, and how the subunits interact. In this study, the action of homotetrameric olfactory-type CNGA2 channels was studied in inside-out membrane patches by simultaneously determining channel activation and ligand binding, using the fluorescent cGMP analogue 8-DY547-cGMP as the ligand. At concentrations of 8-DY547-cGMP < 1 microM, steady-state binding was larger than steady-state activation, whereas at higher concentrations it was smaller, generating a crossover of the steady-state relationships. Global analysis of these relationships together with multiple activation time courses following cGMP jumps showed that four ligands bind to the channels and that there is significant interaction between the binding sites. Among the binding steps, the second is most critical for channel opening: its association constant is three orders of magnitude smaller than the others and it triggers a switch from a mostly closed to a maximally open state. These results contribute to unravelling the role of the subunits in the cooperative mechanism of CNGA2 channel activation and could be of general relevance for the action of other ion channels and receptors.
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Affiliation(s)
- Christoph Biskup
- Institut für Physiologie II, Friedrich-Schiller-Universität Jena, D 07740 Jena, Germany
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36
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Abstract
We expressed rod-type homotetrameric cyclic nucleotide-gated (CNGA1) channels in Xenopus oocytes and studied activation by photolysis-induced jumps of the 3',5'-cyclic guanosine monophosphate (cGMP) concentration and by voltage steps. cGMP jumps to increasing concentrations up to the EC50 value of 46.5 microM decelerate the activation gating, indicative that even at concentrations of cGMP << EC50 binding is not rate limiting. Above the EC50 value, activation by cGMP jumps is again accelerated to the higher concentrations. At the same cGMP concentration, the speed of the activation gating by depolarizing voltage steps is roughly similar to that by cGMP jumps. Permeating ions passing the pore more slowly (Rb+ > K+ > Na+) slow down the activation time course. At the single-channel level, cGMP jumps to high concentrations cause openings directly to the main open level without passing sublevels. From these results it is concluded that at both low and high cGMP the gating of homotetrameric CNGA1 channels is not rate-limited by the cGMP binding but by conformational changes of the channel which are voltage dependent and include movements in the pore region.
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Affiliation(s)
- Vasilica Nache
- Institut für Physiologie II, Friedrich-Schiller-Universität Jena, Jena, Germany
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37
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Nache V, Schulz E, Zimmer T, Kusch J, Biskup C, Koopmann R, Hagen V, Benndorf K. Activation of olfactory-type cyclic nucleotide-gated channels is highly cooperative. J Physiol 2005; 569:91-102. [PMID: 16081488 PMCID: PMC1464204 DOI: 10.1113/jphysiol.2005.092304] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [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: 12/19/2022] Open
Abstract
Cyclic nucleotide-gated (CNG) ion channels play a key role in the sensory transduction of vision and olfaction. The channels are opened by the binding of cyclic nucleotides. Native olfactory CNG channels are heterotetramers of CNGA2, CNGA4, and CNGB1b subunits. Upon heterologous expression, only CNGA2 subunits can form functional homotetrameric channels. It is presently not known how the binding of the ligands to the four subunits is translated to channel opening. We studied activation of olfactory CNG channels by photolysis-induced jumps of cGMP or cAMP, two cyclic nucleotides with markedly different apparent affinity. It is shown that at equal degree of activation, the activation time course of homotetrameric channels is similar with cGMP and cAMP and it is also similar in homo- and heterotetrameric channels with the same cyclic nucleotide. Kinetic models were globally fitted to activation time courses of homotetrameric channels. While all models containing equivalent binding sites failed, a model containing three binding sites with a ligand affinity high-low-high described the data adequately. Only the second binding step switches from a very low to a very high open probability. We propose a unique gating mechanism for homotetrameric and heterotetrameric channels that involves only three highly cooperative binding steps.
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Affiliation(s)
- Vasilica Nache
- Institut für Physiologie II, Friedrich-Schiller-Universität Jena, Germany
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38
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Abstract
Cyclic nucleotide-gated (CNG) channels are tetrameric non-specific cation channels. They mediate the receptor potentials in photoreceptors and cells of the olfactory epithelium and they are activated by the binding of cyclic nucleotides such as cGMP and cAMP. Previous studies in homotetrameric CNGA1 channels, activated with covalently bound cGMP, presented evidence that partially liganded channels cause partial channel opening (Ruiz & Karpen, 1997, 1999). Here, homotetrameric CNGA1 channels were expressed in Xenopus oocytes. Conductance and gating of these channels were studied as a function of the concentration of freely diffusible cGMP and with different permeating ions. At saturating cGMP the current levels distributed around a single mean in a Gaussian fashion and the open times were long. At low cGMP, however, the current levels were heterogeneous: they were smaller than those at saturating cGMP, equal, or larger. The open times were short. Ions generating the larger single-channel currents (Na(+) > K(+) > Rb(+)) concomitantly increased the heterogeneity of current levels and decreased the open probability and open times. The results suggest that the activation of CNGA1 channels by cGMP and ions staying longer in the pore is associated with less extensive and less frequent conformational fluctuations of the channel pore.
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Affiliation(s)
- Jana Kusch
- Institut für Physiologie II, Friedrich-Schiller-Universität Jena, 07740 Jena, Germany
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39
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Abstract
The alpha subunits of CNG channels of retinal photoreceptors (rod) and olfactory neurons (olf) are proteins that consist of a cytoplasmic NH(2) terminus, a transmembrane core region (including the segments S1-S6), and a cytoplasmic COOH terminus. The COOH terminus contains a cyclic nucleotide monophosphate binding domain NBD) that is linked by the C-linker (CL) to the core region. The binding of cyclic nucleotides to the NBD promotes channel opening by an allosteric mechanism. We examined why the sensitivity to cGMP is 22 times higher in olf than in rod by constructing chimeric channels and determining the [cGMP] causing half maximum channel activity (EC(50)). The characteristic difference in the EC(50) value between rod and olf was introduced by the NH(2) terminus and the core-CL region, whereas the NBD showed a paradoxical effect. The difference of the free energy difference Delta(DeltaG) was determined for each of these three regions with all possible combinations of the other two regions. For rod regions with respect to corresponding olf regions, the open channel conformation was destabilized by the NH(2) terminus (Delta(DeltaG) = -1.0 to -2.0 RT) and the core-CL region (Delta(DeltaG) = -2.0 to -2.9 RT), whereas it was stabilized by the NBD (Delta(DeltaG) = 0.3 to 1.1 RT). The NH(2) terminus deletion mutants of rod and olf differed by Delta(DeltaG) of only 0.9 RT, whereas the wild-type channels differed by the much larger value of 3.1 RT. The results show that in rod and olf, the NH(2) terminus, the core-CL region, and the NBD differ by characteristic Delta(DeltaG) values that do not depend on the specific composition of the other two regions and that the NH(2) terminus generates the main portion of Delta(DeltaG) between the wild-type channels.
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Affiliation(s)
- Holger Möttig
- Institut für Physiologie, Abteilung Herz-Kreislauf-Physiologie, Friedrich-Schiller-Universität Jena, 07740 Jena, Germany
| | - Jana Kusch
- Institut für Physiologie, Abteilung Herz-Kreislauf-Physiologie, Friedrich-Schiller-Universität Jena, 07740 Jena, Germany
| | - Thomas Zimmer
- Institut für Physiologie, Abteilung Herz-Kreislauf-Physiologie, Friedrich-Schiller-Universität Jena, 07740 Jena, Germany
| | - Annette Scholle
- Institut für Physiologie, Abteilung Herz-Kreislauf-Physiologie, Friedrich-Schiller-Universität Jena, 07740 Jena, Germany
| | - Klaus Benndorf
- Institut für Physiologie, Abteilung Herz-Kreislauf-Physiologie, Friedrich-Schiller-Universität Jena, 07740 Jena, Germany
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40
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Affiliation(s)
- J Kusch
- Department of Biology, University of Kaiserslautern, Germany
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41
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Willmann R, Kusch J, Sultan KR, Schneider AG, Pette D. Muscle LIM protein is upregulated in fast skeletal muscle during transition toward slower phenotypes. Am J Physiol Cell Physiol 2001; 280:C273-9. [PMID: 11208521 DOI: 10.1152/ajpcell.2001.280.2.c273] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [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: 11/22/2022]
Abstract
Muscle LIM protein (MLP) is constitutively expressed in slow, but undetectable in fast, muscles of the rat. Here we show that MLP was upregulated at both the mRNA and protein levels under experimental conditions leading to transitions from fast to slower phenotypes. Chronic low-frequency stimulation and mechanical overloading by synergist removal both induced fast-to-slow shifts in myosin heavy chain (MHC) isoforms and expression of MLP in fast muscles. High amounts of MLP mRNA and protein were also present in fast muscles of the myotonic, hyperactive ADR mouse. Hypothyroidism evoked shifts in myosin composition toward slower isoforms and increased the MLP protein content of soleus (SOL) muscle but failed to induce MLP in fast muscles. Unweighting by hindlimb suspension elicited slow-to-fast transitions in MHC expression without altering MLP levels in SOL muscle. Hyperthyroidism shifted the MHC pattern toward faster isoforms but did not affect MLP content in SOL muscle. We conclude that alterations in MLP expression are associated with transitions from fast to slower phenotypes but not with slow-to-fast muscle fiber transitions.
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Affiliation(s)
- R Willmann
- Department of Biology, University of Konstanz, D-78457 Konstanz, Germany
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42
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Kusch J, Stremmel M, Breiner HW, Adams V, Schweikert M, Schmidt H. The Toxic Symbiont Caedibacter caryophila in the Cytoplasm of Paramecium novaurelia. Microb Ecol 2000; 40:330-335. [PMID: 12035091 DOI: 10.1007/s002480000034] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/1999] [Accepted: 05/20/1999] [Indexed: 05/23/2023]
Abstract
Endosymbiotic bacteria were observed to inhabit the cytoplasm of the freshwater ciliate Paramecium novaurelia. Transmission electron microscopy and toxicity tests with sensitive paramecia showed that the endosymbionts belong to the genus Caedibacter. The bacteria conferred a killer trait to their host paramecia. The production of a proteinaceous inclusion body ("R-body") in the bacterial cell makes them toxic to other paramecia after they become enclosed in food vacuoles. R-bodies of Caedibacter sp were associated with phages, which are known in most other Caedibacter species to code for the R-body proteins. The killer-effect of P. novaurelia on sensitive P. caudatum strains was of the "paralysis" type, which is a characteristic of the symbiont species Caedibacter caryophila. Until now C. caryophila was known to inhabit the macronucleus of Paramecium caudatum only. Sequencing of the 16S rRNA-gene proved that Caedibacter sp from the cytoplasm of P. novaurelia belongs to the species C. caryophila as well. The rDNA-sequence of 1695 bp length differed in a total of only 1 bp from the corresponding gene in C. caryophila from the macronucleus of P. caudatum. The results indicate that the infection of specific host cell compartments may depend on host genes, but not on different traits of the infecting symbiont species. The occurrence of killer and sensitive paramecia strains together in one pond is discussed with respect to the competitive advantage of the killer trait.
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Affiliation(s)
- J. Kusch
- Department of Ecology, University of Kaiserslautern, Germany
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43
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Mueller MS, Harnasch M, Kolb C, Kusch J, Sadowski T, Sedlacek R. The murine ortholog of matrix metalloproteinase 19: its cloning, gene organization, and expression. Gene 2000; 256:101-11. [PMID: 11054540 DOI: 10.1016/s0378-1119(00)00369-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [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: 11/20/2022]
Abstract
We have isolated a murine cDNA orthologous to the human matrix metalloproteinase 19 (hMMP-19). The murine MMP-19 cDNA was amplified by RT-PCR using specific primers whose DNA sequences were derived from both murine MMP-19 genomic DNA and partial cDNA sequences. The murine MMP-19 (mMMP-19) is 79% identical to the human ortholog and encodes a protein of 527 amino acids with a deduced molecular mass of 59.1kDa. Analyzing the exon/intron junctions we revealed that the murine MMP-19 gene consists of nine exons and eight introns, and thus differs from the gene organization of other matrix metalloproteinases. Furthermore, a 587bp fragment of the mMMP-19 promoter containing a TATA box and an AP-1 binding motif was cloned, and 3.3kb transcripts of the MMP-19 gene were identified in liver, kidney, spleen, and colon. Finally, immunostaining of murine heart cryosections showed that mMMP-19, like its human counterpart, is expressed in the arterial tunica media of large blood vessels. By cloning mMMP-19 and unraveling its genomic structure, we have obtained valuable information for further study of the function of this MMP in vivo.
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MESH Headings
- 3T3 Cells
- Amino Acid Sequence
- Animals
- Base Sequence
- Cloning, Molecular
- DNA/chemistry
- DNA/genetics
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- DNA, Complementary/isolation & purification
- Ecdysterone/analogs & derivatives
- Ecdysterone/pharmacology
- Exons
- Gene Expression
- Gene Expression Regulation, Enzymologic/drug effects
- Genes/genetics
- Humans
- Immunohistochemistry
- Introns
- Matrix Metalloproteinases, Secreted
- Metalloendopeptidases/genetics
- Metalloendopeptidases/metabolism
- Mice
- Mice, Inbred BALB C
- Molecular Sequence Data
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Regulatory Sequences, Nucleic Acid
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Tissue Distribution
- Tumor Cells, Cultured
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Affiliation(s)
- M S Mueller
- University of Konstanz, Department of Immunology, Postfach M662, Konstanz, Germany
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Görtz HD, Kuhlmann HW, Möllenbeck M, Tiedtke A, Kusch J, Schmidt HJ, Miyake A. Intra- and intercellular communication systems in ciliates. Naturwissenschaften 1999; 86:422-34. [PMID: 10501690 DOI: 10.1007/s001140050646] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Intracellular signaling and cell-cell interactions are basic features of living organisms. Ciliated protozoa show complex mechanisms of intracellular signaling, as is demonstrated for the phagosomal pathway. Although unicellular, ciliates also communicate with other cells, for example, with invading or symbiotic micro-organisms, some of which are dwelling in the nuclei. In predator-prey interactions chemical signals (kairomones) released by certain predators induce defensive morphological or behavioral changes in the prey ciliates. In intercellular communication sensu strictu ciliate cells communicate with each other, for example, in sexual propagation. A variety of sexual signals have been found to function in preconjugant interaction. Many phenomena of cellular communication in ciliates appear to be similar to those found in multicellular organisms.
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Affiliation(s)
- H D Görtz
- Biologisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany.
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45
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Kusch J. Adaptation of inducible defense in Euplotes daidaleos (Ciliophora) to predation risks by various predators. Microb Ecol 1995; 30:79-88. [PMID: 24185414 DOI: 10.1007/bf00184515] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/1994] [Revised: 12/01/1994] [Indexed: 06/02/2023]
Abstract
The extent of induced morphological defense in Euplotes daidaleos correlates to this ciliate's predation risk from the defense-inducing predator species. Euplotes daidaleos responded by morphological transformation only to organisms that are able to feed on typically formed Euplotes cells (63 ± 5 μm cell width in E. daidaleos). Three of those potential predator species caused defensive changes to various degrees (Student's t-test, P < 0.1 to P < 0.0001): Lembadion bullinum (Ciliata) induced 82 ± 6 μm cell width in E. daidaleos; Chaetogaster diastrophus (Oligochaeta) induced 85 = 6 μm width; and Stenostomum sphagnetorum (Turbellaria) induced 89 ± 8 μm width (at a density of 10 predators per milliliter, respectively). At higher predator densities (50 or 100 organisms per milliliter), Euplotes developed a correspondingly larger width (to a maximum of 103 ± 10 μm in the presence of S. sphagnetorum). Euplotes did not respond to organisms (e.g., Blepharisma japonicum, Colpidium campylum, Didinium nasutum, Paramecium caudatum, Spirostomum ambiguum, Stentor coeruleus) that cannot feed on this ciliate species. Daphnia longispina and Bursaria truncatella predators, which can feed on large prey of ≥125, or ≥200 μm in diameter, respectively, also had no effect on the morphology of Euplotes. The extent of defense in Euplotes that was induced by 10 predators per milliliter during 24 h decreased the predation risk from those predators to 67% in the presence of S. sphagnetorum, to 50% with L. bullinum, and to 15% with C. diastrophus, compared to the typical form of Euplotes. In a natural population, the defensive form of E. daidaleos was found with average cell widths of 88 ± 8 μm. The results indicate that predator-induced defense in natural Euplotes populations is beneficial to this prey and that it is adapted to the predation abilities of Euplotes predators, whereby energetical costs related to defensive changes may be saved.
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Affiliation(s)
- J Kusch
- Institute for General Zoology and Genetics, University of Münster, Germany
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