1
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Shigedomi K, Osada S, Jelokhani-Niaraki M, Kodama H. Systematic Design and Validation of Ion Channel Stabilization of Amphipathic α-Helical Peptides Incorporating Tryptophan Residues. ACS OMEGA 2021; 6:723-732. [PMID: 33553860 PMCID: PMC7853622 DOI: 10.1021/acsomega.0c05254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 12/17/2020] [Indexed: 05/27/2023]
Abstract
Aromatic interactions such as π-π interaction and cation-π interaction are present in membrane proteins and play important roles in both structure and function. To systematically investigate the effect of aromatic residues on the structural stability and ion permeability of peptide-formed ion channels, we designed several peptides with one or two tryptophan (Trp) residues incorporated at different positions in amphipathic α-helical peptides. Circular dichroism (CD) studies revealed the preferable position of Trp residues for self-association in these designed peptides. Systematically designed di-substituted peptides with two Trps at each helix termini demonstrated intermolecular Trp-Trp interactions caused by aggregation. In the presence of liposomes, Trp on the hydrophilic face of the peptide enhanced interaction with the lipid membrane to increase the amphipathic α-helical contents. Appropriate incorporation and positioning of Trp enabled peptides to form more stable channels and had notable effects with Trp di-substituted peptides. The ion channel forming capability of a series of these peptides showed that the cation-π interactions between Trp and Lys residues in adjacent transmembrane helices contribute to remarkable stabilization of the channel structure.
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Affiliation(s)
- Keita Shigedomi
- Department
of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Satoshi Osada
- Department
of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Masoud Jelokhani-Niaraki
- Department
of Chemistry and Biochemistry, Wilfrid Laurier
University, Waterloo, Ontario N2L3C5, Canada
| | - Hiroaki Kodama
- Department
of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
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2
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Bignucolo O, Bernèche S. The Voltage-Dependent Deactivation of the KvAP Channel Involves the Breakage of Its S4 Helix. Front Mol Biosci 2020; 7:162. [PMID: 32850956 PMCID: PMC7403406 DOI: 10.3389/fmolb.2020.00162] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Accepted: 06/24/2020] [Indexed: 11/13/2022] Open
Abstract
Voltage-gated potassium channels (Kv) allow ion permeation upon changes of the membrane electrostatic potential (Vm). Each subunit of these tetrameric channels is composed of six transmembrane helices, of which the anti-parallel helix bundle S1-S4 constitutes the voltage-sensor domain (VSD) and S5-S6 forms the pore domain. Here, using 82 molecular dynamics (MD) simulations involving 266 replicated VSDs, we report novel responses of the archaebacterial potassium channel KvAP to membrane polarization. We show that the S4 α-helix, which is straight in the experimental crystal structure solved under depolarized conditions (Vm ∼ 0), breaks into two segments when the cell membrane is hyperpolarized (Vm << 0), and reversibly forms a single straight helix following depolarization (Vm = 0). The outermost segment of S4 translates along the normal to the membrane, bringing new perspective to previously paradoxical accessibility experiments that were initially thought to imply the displacement of the whole VSD across the membrane. The novel model is applied through steered and unbiased MD simulations to the recently solved whole structure of KvAP. The simulations show that the resting state involves a re-orientation of the S5 α-helix by ∼ 5-6 degrees in respect to the normal of the bilayer, which could result in the constriction and closure of the selectivity filter. Our findings support the idea that the breakage of S4 under (hyper)polarization is a general feature of Kv channels with a non-swapped topology.
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Affiliation(s)
- Olivier Bignucolo
- Biozentrum, University of Basel, Basel, Switzerland.,SIB Swiss Institute of Bioinformatics, Basel/Lausanne, Switzerland
| | - Simon Bernèche
- Biozentrum, University of Basel, Basel, Switzerland.,SIB Swiss Institute of Bioinformatics, Basel/Lausanne, Switzerland
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3
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Tryptophan-mediated Dimerization of the TssL Transmembrane Anchor Is Required for Type VI Secretion System Activity. J Mol Biol 2018; 430:987-1003. [DOI: 10.1016/j.jmb.2018.02.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 01/29/2018] [Accepted: 02/11/2018] [Indexed: 11/23/2022]
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4
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Mazzolini M, Arcangeletti M, Marchesi A, Napolitano LMR, Grosa D, Maity S, Anselmi C, Torre V. The gating mechanism in cyclic nucleotide-gated ion channels. Sci Rep 2018; 8:45. [PMID: 29311674 PMCID: PMC5758780 DOI: 10.1038/s41598-017-18499-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 12/04/2017] [Indexed: 11/09/2022] Open
Abstract
Cyclic nucleotide-gated (CNG) channels mediate transduction in several sensory neurons. These channels use the free energy of CNs' binding to open the pore, a process referred to as gating. CNG channels belong to the superfamily of voltage-gated channels, where the motion of the α-helix S6 controls gating in most of its members. To date, only the open, cGMP-bound, structure of a CNG channel has been determined at atomic resolution, which is inadequate to determine the molecular events underlying gating. By using electrophysiology, site-directed mutagenesis, chemical modification, and Single Molecule Force Spectroscopy, we demonstrate that opening of CNGA1 channels is initiated by the formation of salt bridges between residues in the C-linker and S5 helix. These events trigger conformational changes of the α-helix S5, transmitted to the P-helix and leading to channel opening. Therefore, the superfamily of voltage-gated channels shares a similar molecular architecture but has evolved divergent gating mechanisms.
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Affiliation(s)
- Monica Mazzolini
- International School for Advanced Studies, Trieste, 34136, Italy.
| | | | - Arin Marchesi
- INSERM U1006, Aix-Marseille Université, Parc Scientifique et Technologique de Luminy, Marseille, 13009, France
| | - Luisa M R Napolitano
- International School for Advanced Studies, Trieste, 34136, Italy
- Structural Biology Laboratory, Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Trieste, 34149, Italy
| | - Debora Grosa
- International School for Advanced Studies, Trieste, 34136, Italy
| | - Sourav Maity
- International School for Advanced Studies, Trieste, 34136, Italy
| | - Claudio Anselmi
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Vincent Torre
- International School for Advanced Studies, Trieste, 34136, Italy.
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5
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Sforna L, Megaro A, Pessia M, Franciolini F, Catacuzzeno L. Structure, Gating and Basic Functions of the Ca2+-activated K Channel of Intermediate Conductance. Curr Neuropharmacol 2018; 16:608-617. [PMID: 28875832 PMCID: PMC5997868 DOI: 10.2174/1570159x15666170830122402] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 07/21/2017] [Accepted: 07/22/2017] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND The KCa3.1 channel is the intermediate-conductance member of the Ca2+- activated K channel superfamily. It is widely expressed in excitable and non-excitable cells, where it plays a major role in a number of cell functions. This paper aims at illustrating the main structural, biophysical and modulatory properties of the KCa3.1 channel, and providing an account of experimental data on its role in volume regulation and Ca2+ signals. METHODS Research and online content related to the structure, structure/function relationship, and physiological role of the KCa3.1 channel are reviewed. RESULTS Expressed in excitable and non-excitable cells, the KCa3.1 channel is voltage independent, its opening being exclusively gated by the binding of intracellular Ca2+ to calmodulin, a Ca2+- binding protein constitutively associated with the C-terminus of each KCa3.1 channel α subunit. The KCa3.1 channel activates upon high affinity Ca2+ binding, and in highly coordinated fashion giving steep Hill functions and relatively low EC50 values (100-350 nM). This high Ca2+ sensitivity is physiologically modulated by closely associated kinases and phosphatases. The KCa3.1 channel is normally activated by global Ca2+ signals as resulting from Ca2+ released from intracellular stores, or by the refilling influx through store operated Ca2+ channels, but cases of strict functional coupling with Ca2+-selective channels are also found. KCa3.1 channels are highly expressed in many types of cells, where they play major roles in cell migration and death. The control of these complex cellular processes is achieved by KCa3.1 channel regulation of the driving force for Ca2+ entry from the extracellular medium, and by mediating the K+ efflux required for cell volume control. CONCLUSION Much work remains to be done to fully understand the structure/function relationship of the KCa3.1 channels. Hopefully, this effort will provide the basis for a beneficial modulation of channel activity under pathological conditions.
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Affiliation(s)
| | | | | | - Fabio Franciolini
- Address correspondence to these authors at the Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Pascoli, 8-06123, Perugia; Tel: 39.075.585.5751; E-mails: and
| | - Luigi Catacuzzeno
- Address correspondence to these authors at the Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Pascoli, 8-06123, Perugia; Tel: 39.075.585.5751; E-mails: and
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6
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Heer FT, Posson DJ, Wojtas-Niziurski W, Nimigean CM, Bernèche S. Mechanism of activation at the selectivity filter of the KcsA K + channel. eLife 2017; 6:25844. [PMID: 28994652 PMCID: PMC5669632 DOI: 10.7554/elife.25844] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 10/05/2017] [Indexed: 12/26/2022] Open
Abstract
Potassium channels are opened by ligands and/or membrane potential. In voltage-gated K+ channels and the prokaryotic KcsA channel, conduction is believed to result from opening of an intracellular constriction that prevents ion entry into the pore. On the other hand, numerous ligand-gated K+ channels lack such gate, suggesting that they may be activated by a change within the selectivity filter, a narrow region at the extracellular side of the pore. Using molecular dynamics simulations and electrophysiology measurements, we show that ligand-induced conformational changes in the KcsA channel removes steric restraints at the selectivity filter, thus resulting in structural fluctuations, reduced K+ affinity, and increased ion permeation. Such activation of the selectivity filter may be a universal gating mechanism within K+ channels. The occlusion of the pore at the level of the intracellular gate appears to be secondary. Potassium channels are proteins found in almost all living organisms and are vital for many different biological processes. These proteins contain a pore that allows potassium ions to flow through cell membranes, but only when the channel is open. Most channels have a narrowing at the inward side of the pore, which was proposed to form a gate that controls the flow of ions. This gate only opens when the channel activates. Nearer the outward side of the pore is another narrow region called the selectivity filter. This region interacts selectively with potassium ions as they pass through the channel. Not all channels form a tight constriction at the inward end of their pore, yet they still only allow potassium ions to flow through when activated. This suggested that these channels might instead use the selectivity filter as a gate. It would also mean that whilst different potassium channels have similar structures, they do not share a common gating mechanism that controls the flow of ions. Heer et al. studied the bacterial channel called KcsA, which was thought to control the flow of potassium ions via a traditional inward gate. Computer simulations based on this protein’s structure, and experiments with purified KcsA in artificial membranes, showed that the selectivity filter was also involved when KcsA was activated. When the activated channel changed shape, the selectivity filter – which had been constrained by regions forming the pore – could now move and allow potassium ions to flow through the pore. Heer et al. confirmed using a mutant KcsA that the motion of the inward side of the pore upon activation affected the movement of the selectivity filter gate as predicted by the simulation. These findings show that the KcsA channel opens and closes at the selectivity filter. The changes at the inward side of the pore, previously believed to be the gate, firstly enable the selectivity filter to serve as a gate while also forming a secondary gate. Heer et al. propose that most if not all potassium channels may also use this mechanism. These findings illustrate that molecular simulations can be powerful for predicting how changes in the structure of a protein will affect its behavior. This and future studies of other potassium channels will help scientists to better understand the subtle differences between the diverse range of channels found across different organisms.
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Affiliation(s)
- Florian T Heer
- SIB Swiss Institute of Bioinformatics, University of Basel, Basel, Switzerland.,Biozentrum, University of Basel, Basel, Switzerland
| | - David J Posson
- Department of Anesthesiology, Weill Cornell Medical College, New York, United States.,Department of Physiology and Biophysics, Weill Cornell Medical College, New York, United States
| | - Wojciech Wojtas-Niziurski
- SIB Swiss Institute of Bioinformatics, University of Basel, Basel, Switzerland.,Biozentrum, University of Basel, Basel, Switzerland
| | - Crina M Nimigean
- Department of Anesthesiology, Weill Cornell Medical College, New York, United States.,Department of Physiology and Biophysics, Weill Cornell Medical College, New York, United States.,Department of Biochemistry, Weill Cornell Medical College, New York, United States
| | - Simon Bernèche
- SIB Swiss Institute of Bioinformatics, University of Basel, Basel, Switzerland.,Biozentrum, University of Basel, Basel, Switzerland
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7
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Nguyen HM, Singh V, Pressly B, Jenkins DP, Wulff H, Yarov-Yarovoy V. Structural Insights into the Atomistic Mechanisms of Action of Small Molecule Inhibitors Targeting the KCa3.1 Channel Pore. Mol Pharmacol 2017; 91:392-402. [PMID: 28126850 PMCID: PMC5363711 DOI: 10.1124/mol.116.108068] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 01/19/2017] [Indexed: 12/13/2022] Open
Abstract
The intermediate-conductance Ca2+-activated K+ channel (KCa3.1) constitutes an attractive pharmacological target for immunosuppression, fibroproliferative disorders, atherosclerosis, and stroke. However, there currently is no available crystal structure of this medically relevant channel that could be used for structure-assisted drug design. Using the Rosetta molecular modeling suite we generated a molecular model of the KCa3.1 pore and tested the model by first confirming previously mapped binding sites and visualizing the mechanism of TRAM-34 (1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole), senicapoc (2,2-bis-(4-fluorophenyl)-2-phenylacetamide), and NS6180 (4-[[3-(trifluoromethyl)phenyl]methyl]-2H-1,4-benzothiazin-3(4H)-one) inhibition at the atomistic level. All three compounds block ion conduction directly by fully or partially occupying the site that would normally be occupied by K+ before it enters the selectivity filter. We then challenged the model to predict the receptor sites and mechanisms of action of the dihydropyridine nifedipine and an isosteric 4-phenyl-pyran. Rosetta predicted receptor sites for nifedipine in the fenestration region and for the 4-phenyl-pyran in the pore lumen, which could both be confirmed by site-directed mutagenesis and electrophysiology. While nifedipine is thus not a pore blocker and might be stabilizing the channel in a nonconducting conformation or interfere with gating, the 4-phenyl-pyran was found to be a classical pore blocker that directly inhibits ion conduction similar to the triarylmethanes TRAM-34 and senicapoc. The Rosetta KCa3.1 pore model explains the mechanism of action of several KCa3.1 blockers at the molecular level and could be used for structure-assisted drug design.
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Affiliation(s)
- Hai M Nguyen
- Department of Pharmacology (H.M.N, V.S., B.P., D.P.J., H.W.) and Department of Physiology and Membrane Biology (V. Y.-Y.), School of Medicine, University of California at Davis, Davis, California
| | - Vikrant Singh
- Department of Pharmacology (H.M.N, V.S., B.P., D.P.J., H.W.) and Department of Physiology and Membrane Biology (V. Y.-Y.), School of Medicine, University of California at Davis, Davis, California
| | - Brandon Pressly
- Department of Pharmacology (H.M.N, V.S., B.P., D.P.J., H.W.) and Department of Physiology and Membrane Biology (V. Y.-Y.), School of Medicine, University of California at Davis, Davis, California
| | - David Paul Jenkins
- Department of Pharmacology (H.M.N, V.S., B.P., D.P.J., H.W.) and Department of Physiology and Membrane Biology (V. Y.-Y.), School of Medicine, University of California at Davis, Davis, California
| | - Heike Wulff
- Department of Pharmacology (H.M.N, V.S., B.P., D.P.J., H.W.) and Department of Physiology and Membrane Biology (V. Y.-Y.), School of Medicine, University of California at Davis, Davis, California
| | - Vladimir Yarov-Yarovoy
- Department of Pharmacology (H.M.N, V.S., B.P., D.P.J., H.W.) and Department of Physiology and Membrane Biology (V. Y.-Y.), School of Medicine, University of California at Davis, Davis, California
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8
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Tseng TW, Lee LW, Luo TT, Chien PH, Liu YH, Lee SL, Wang CM, Lu KL. Gate-opening upon CO2 adsorption on a metal–organic framework that mimics a natural stimuli-response system. Dalton Trans 2017; 46:14728-14732. [PMID: 28956887 DOI: 10.1039/c7dt03119j] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A dynamic d-champhorate-based protuberant-grid-type framework, undergoes gate opening and closing processes that were triggered by the stimuli of the adsorption or desorption of CO2. It is able to specifically recognize CO2 over than N2 and H2 and shows a high CO2 uptake of 90 mg g−1 under 35 bar at 298 K.
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Affiliation(s)
- T. W. Tseng
- Department of Chemical Engineering and Biotechnology
- National Taipei University of Technology
- Taipei 106
- Taiwan
| | - L. W. Lee
- Institute of Chemistry Academia Sinica
- Taipei 115
- Taiwan
| | - T. T. Luo
- Department of Chemical Engineering and Biotechnology
- National Taipei University of Technology
- Taipei 106
- Taiwan
| | - P. H. Chien
- Department of Chemistry
- Fu Jen Catholic University
- New Taipei City 242
- Taiwan
| | - Y. H. Liu
- Department of Chemistry
- Fu Jen Catholic University
- New Taipei City 242
- Taiwan
| | - S. L. Lee
- Institute of Materials Science and Engineering
- National Central University
- Taoyuan 320
- Taiwan
| | - C. M. Wang
- Department of Bioscience and Biotechnology
- National Taiwan Ocean University
- Keelung 202
- Taiwan
| | - K. L. Lu
- Institute of Chemistry Academia Sinica
- Taipei 115
- Taiwan
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9
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Giese MH, Gardner A, Hansen A, Sanguinetti MC. Molecular mechanisms of Slo2 K + channel closure. J Physiol 2016; 595:2321-2336. [PMID: 27682982 DOI: 10.1113/jp273225] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 09/20/2016] [Indexed: 01/02/2023] Open
Abstract
KEY POINTS Intracellular Na+ -activated Slo2 potassium channels are in a closed state under normal physiological conditions, although their mechanisms of ion permeation gating are not well understood. A cryo-electron microscopy structure of Slo2.2 suggests that the ion permeation pathway of these channels is closed by a single constriction of the inner pore formed by the criss-crossing of the cytoplasmic ends of the S6 segments (the S6 bundle crossing) at a conserved Met residue. Functional characterization of mutant Slo2 channels suggests that hydrophobic interactions between Leu residues in the upper region of the S6 segments contribute to stabilizing the inner pore in a non-conducting state. Mutation of the conserved Met residues in the S6 segments to the negatively-charged Glu did not induce constitutive opening of Slo2.1 or Slo2.2, suggesting that ion permeation of Slo2 channels is not predominantly gated by the S6 bundle crossing. ABSTRACT Large conductance K+ -selective Slo2 channels are in a closed state unless activated by elevated [Na+ ]i . Our previous studies suggested that the pore helix/selectivity filter serves as the activation gate in Slo2 channels. In the present study, we evaluated two other potential mechanisms for stabilization of Slo2 channels in a closed state: (1) dewetting and collapse of the inner pore (hydrophobic gating) and (2) constriction of the inner pore by tight criss-crossing of the cytoplasmic ends of the S6 α-helical segments. Slo2 channels contain two conserved Leu residues in each of the four S6 segments that line the inner pore region nearest the bottom of the selectivity filter. To evaluate the potential role of these residues in hydrophobic gating, Leu267 and Leu270 in human Slo2.1 were each replaced by 15 different residues. The relative conductance of mutant channels was highly dependent on hydrophilicity and volume of the amino acid substituted for Leu267 and was maximal with L267H. Consistent with their combined role in hydrophobic gating, replacement of both Leu residues with the isosteric but polar residue Asn (L267N/L270N) stabilized channels in a fully open state. In a recent cryo-electron microscopy structure of chicken Slo2.2, the ion permeation pathway of the channel is closed by a constriction of the inner pore formed by criss-crossing of the S6 segments at a conserved Met. Inconsistent with the S6 segment crossing forming the activation gate, replacement of the homologous Met residues in human Slo2.1 or Slo2.2 with the negatively-charged Glu did not induce constitutive channel opening.
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Affiliation(s)
- M Hunter Giese
- Nora Eccles Harrison Cardiovascular Research & Training Institute
| | - Alison Gardner
- Nora Eccles Harrison Cardiovascular Research & Training Institute
| | - Angela Hansen
- Nora Eccles Harrison Cardiovascular Research & Training Institute
| | - Michael C Sanguinetti
- Nora Eccles Harrison Cardiovascular Research & Training Institute.,Department of Internal Medicine, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, UT, USA
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10
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Peng B, Ding XY, Sun C, Liu W, Zhang JZH, Zhao X. The effect of POPC acyl chains packing by aromatic amino acid methyl esters investigated by ATR-FTIR combined with QM calculations. RSC Adv 2016. [DOI: 10.1039/c6ra05903a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The packing of POPC acyl chains can be influenced by aromatic amino acid methyl esters significantly, thus the HCCH motif is packed closed to the other one of an adjacent acyl chain with enhancement by dispersion interactions.
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Affiliation(s)
- Bo Peng
- Shanghai Key Laboratory of Magnetic Resonance
- Department of Physics
- School of Physics and Materials Science
- East China Normal University
- Shanghai 200062
| | - Xiao-Yan Ding
- Shanghai Key Laboratory of Magnetic Resonance
- Department of Physics
- School of Physics and Materials Science
- East China Normal University
- Shanghai 200062
| | - Chao Sun
- Shanghai Key Laboratory of Magnetic Resonance
- Department of Physics
- School of Physics and Materials Science
- East China Normal University
- Shanghai 200062
| | - Wei Liu
- State Key Laboratory of Precision Spectroscopy
- Department of Physics
- School of Physics and Materials Science
- East China Normal University
- Shanghai 200062
| | - John Z. H. Zhang
- State Key Laboratory of Precision Spectroscopy
- Department of Physics
- School of Physics and Materials Science
- East China Normal University
- Shanghai 200062
| | - Xin Zhao
- Shanghai Key Laboratory of Magnetic Resonance
- Department of Physics
- School of Physics and Materials Science
- East China Normal University
- Shanghai 200062
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11
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Suzuki T, Hansen A, Sanguinetti MC. Hydrophobic interactions between the S5 segment and the pore helix stabilizes the closed state of Slo2.1 potassium channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:783-92. [PMID: 26724206 DOI: 10.1016/j.bbamem.2015.12.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 11/26/2015] [Accepted: 12/21/2015] [Indexed: 11/28/2022]
Abstract
Under normal physiological conditions, Slo2.1K(+) channels are in a closed state unless activated by an elevation in [Na(+)]i. Fenamates such as niflumic acid also activate Slo2.1. Previous studies suggest that activation of Slo2.1 channels is mediated by a conformational change in the selectivity filter, and not a widening of the aperture formed by the S6 segment bundle crossing as occurs in voltage-gated K(+) channels. It is unclear how binding of Na(+) or fenamates is allosterically linked to opening of the presumed selectivity filter activation gate in Slo2.1. Here we examined the role of the S5 transmembrane segment in the activation of Slo2.1. Channels were heterologously expressed in Xenopus laevis oocytes and whole cell currents measured with the voltage-clamp technique. Ala substitution of five residues located on a single face of the S5 α-helical segment induced constitutive channel activity. Leu-209, predicted to face towards Phe-240 in the pore helix was investigated by further mutagenesis. Mutation of Leu-209 to Glu or Gln induced maximal channel activation as did the combined mutation to Ala of all three hydrophobic S5 residues predicted to be adjacent to Phe-240. Together these results suggest that hydrophobic interactions between residues in S5 and the C-terminal end of the pore helix stabilize Slo2.1 channels in a closed state.
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Affiliation(s)
- Tomoyuki Suzuki
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA
| | - Angela Hansen
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA
| | - Michael C Sanguinetti
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA; Department of Internal Medicine, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, UT 84112, USA.
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12
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Coleman N, Brown BM, Oliván-Viguera A, Singh V, Olmstead MM, Valero MS, Köhler R, Wulff H. New positive Ca2+-activated K+ channel gating modulators with selectivity for KCa3.1. Mol Pharmacol 2014; 86:342-57. [PMID: 24958817 DOI: 10.1124/mol.114.093286] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Small-conductance (KCa2) and intermediate-conductance (KCa3.1) calcium-activated K(+) channels are voltage-independent and share a common calcium/calmodulin-mediated gating mechanism. Existing positive gating modulators like EBIO, NS309, or SKA-31 activate both KCa2 and KCa3.1 channels with similar potency or, as in the case of CyPPA and NS13001, selectively activate KCa2.2 and KCa2.3 channels. We performed a structure-activity relationship (SAR) study with the aim of optimizing the benzothiazole pharmacophore of SKA-31 toward KCa3.1 selectivity. We identified SKA-111 (5-methylnaphtho[1,2-d]thiazol-2-amine), which displays 123-fold selectivity for KCa3.1 (EC50 111 ± 27 nM) over KCa2.3 (EC50 13.7 ± 6.9 μM), and SKA-121 (5-methylnaphtho[2,1-d]oxazol-2-amine), which displays 41-fold selectivity for KCa3.1 (EC50 109 nM ± 14 nM) over KCa2.3 (EC50 4.4 ± 1.6 μM). Both compounds are 200- to 400-fold selective over representative KV (KV1.3, KV2.1, KV3.1, and KV11.1), NaV (NaV1.2, NaV1.4, NaV1.5, and NaV1.7), as well as CaV1.2 channels. SKA-121 is a typical positive-gating modulator and shifts the calcium-concentration response curve of KCa3.1 to the left. In blood pressure telemetry experiments, SKA-121 (100 mg/kg i.p.) significantly lowered mean arterial blood pressure in normotensive and hypertensive wild-type but not in KCa3.1(-/-) mice. SKA-111, which was found in pharmacokinetic experiments to have a much longer half-life and to be much more brain penetrant than SKA-121, not only lowered blood pressure but also drastically reduced heart rate, presumably through cardiac and neuronal KCa2 activation when dosed at 100 mg/kg. In conclusion, with SKA-121, we generated a KCa3.1-specific positive gating modulator suitable for further exploring the therapeutical potential of KCa3.1 activation.
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Affiliation(s)
- Nichole Coleman
- Department of Pharmacology (N.C., B.M.B., V.S., H.W.), School of Medicine, and Department of Chemistry (M.M.O.), University of California, Davis, California; Aragon Institute of Health Sciences, Instituto de Investigación Sanitaria, Fundación Agencia Aragonesa para la Investigación y el Desarrollo, Zaragoza, Spain (A.O.-V., R.K.); and Grupo de Investigación del Medio Ambiente del Centro de Estudios Superiores, Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego, Spain (M.S.V.)
| | - Brandon M Brown
- Department of Pharmacology (N.C., B.M.B., V.S., H.W.), School of Medicine, and Department of Chemistry (M.M.O.), University of California, Davis, California; Aragon Institute of Health Sciences, Instituto de Investigación Sanitaria, Fundación Agencia Aragonesa para la Investigación y el Desarrollo, Zaragoza, Spain (A.O.-V., R.K.); and Grupo de Investigación del Medio Ambiente del Centro de Estudios Superiores, Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego, Spain (M.S.V.)
| | - Aida Oliván-Viguera
- Department of Pharmacology (N.C., B.M.B., V.S., H.W.), School of Medicine, and Department of Chemistry (M.M.O.), University of California, Davis, California; Aragon Institute of Health Sciences, Instituto de Investigación Sanitaria, Fundación Agencia Aragonesa para la Investigación y el Desarrollo, Zaragoza, Spain (A.O.-V., R.K.); and Grupo de Investigación del Medio Ambiente del Centro de Estudios Superiores, Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego, Spain (M.S.V.)
| | - Vikrant Singh
- Department of Pharmacology (N.C., B.M.B., V.S., H.W.), School of Medicine, and Department of Chemistry (M.M.O.), University of California, Davis, California; Aragon Institute of Health Sciences, Instituto de Investigación Sanitaria, Fundación Agencia Aragonesa para la Investigación y el Desarrollo, Zaragoza, Spain (A.O.-V., R.K.); and Grupo de Investigación del Medio Ambiente del Centro de Estudios Superiores, Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego, Spain (M.S.V.)
| | - Marilyn M Olmstead
- Department of Pharmacology (N.C., B.M.B., V.S., H.W.), School of Medicine, and Department of Chemistry (M.M.O.), University of California, Davis, California; Aragon Institute of Health Sciences, Instituto de Investigación Sanitaria, Fundación Agencia Aragonesa para la Investigación y el Desarrollo, Zaragoza, Spain (A.O.-V., R.K.); and Grupo de Investigación del Medio Ambiente del Centro de Estudios Superiores, Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego, Spain (M.S.V.)
| | - Marta Sofia Valero
- Department of Pharmacology (N.C., B.M.B., V.S., H.W.), School of Medicine, and Department of Chemistry (M.M.O.), University of California, Davis, California; Aragon Institute of Health Sciences, Instituto de Investigación Sanitaria, Fundación Agencia Aragonesa para la Investigación y el Desarrollo, Zaragoza, Spain (A.O.-V., R.K.); and Grupo de Investigación del Medio Ambiente del Centro de Estudios Superiores, Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego, Spain (M.S.V.)
| | - Ralf Köhler
- Department of Pharmacology (N.C., B.M.B., V.S., H.W.), School of Medicine, and Department of Chemistry (M.M.O.), University of California, Davis, California; Aragon Institute of Health Sciences, Instituto de Investigación Sanitaria, Fundación Agencia Aragonesa para la Investigación y el Desarrollo, Zaragoza, Spain (A.O.-V., R.K.); and Grupo de Investigación del Medio Ambiente del Centro de Estudios Superiores, Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego, Spain (M.S.V.)
| | - Heike Wulff
- Department of Pharmacology (N.C., B.M.B., V.S., H.W.), School of Medicine, and Department of Chemistry (M.M.O.), University of California, Davis, California; Aragon Institute of Health Sciences, Instituto de Investigación Sanitaria, Fundación Agencia Aragonesa para la Investigación y el Desarrollo, Zaragoza, Spain (A.O.-V., R.K.); and Grupo de Investigación del Medio Ambiente del Centro de Estudios Superiores, Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego, Spain (M.S.V.)
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