1
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Wubulikasimu A, He Z, Long Y, Yuan F, Hou W, Liao Q, Chen H, Rong M. Molecular mechanism of HNTX-I activates the intermediate-conductance Ca 2+-activated K + (IK) channels. Int J Biol Macromol 2023:125197. [PMID: 37285887 DOI: 10.1016/j.ijbiomac.2023.125197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 05/30/2023] [Accepted: 05/31/2023] [Indexed: 06/09/2023]
Abstract
The IK channel, a potassium ion channel regulated by calcium ions and voltages in a bidirectional manner, has been implicated in a range of diseases. However, there are currently few compounds available that can target the IK channel with high potency and specificity. Hainantoxin-I (HNTX-I) is the first peptide activator of IK channel discovered so far, but its activity is not ideal, and the underlying mechanism interaction between HNTX-I toxin and IK channel remains unclear. Thus, our study aimed to enhance the potency of IK channel activating peptides derived from HNTX-I and elucidate the molecular mechanism underlying the interaction between HNTX-I and the IK channel. By employing virtual alanine scanning mutagenesis, we generated 11 HNTX-I mutants using site-directed mutagenesis to pinpoint specific residues crucial for the HNTX-I and IK channel interaction. Subsequently, we identified key residues on the IK channel that are involved in the interaction with HNTX-I. Additionally, molecular docking was employed to guide the molecular engineering process and clarify the binding interface between HNTX-I and the IK channel. Our results demonstrate that HNTX-I primarily acts on the IK channel via the N-terminal amino acid, and its interaction with the IK channel is mediated by electrostatic and hydrophobic interactions, specifically the amino acid residues at positions 1, 3, 5, and 7 on HNTX-I. This study provides valuable insights into the peptide toxins that may serve as potential templates for the development of activators with enhanced potency and selectivity for the IK channel.
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Affiliation(s)
- Atikan Wubulikasimu
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Ziyan He
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Yanping Long
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Fuchu Yuan
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Wenqian Hou
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Qiong Liao
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Haiyan Chen
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha 410081, People's Republic of China.
| | - Mingqiang Rong
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha 410081, People's Republic of China.
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2
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Vera OD, Wulff H, Braun AP. Endothelial KCa channels: Novel targets to reduce atherosclerosis-driven vascular dysfunction. Front Pharmacol 2023; 14:1151244. [PMID: 37063294 PMCID: PMC10102451 DOI: 10.3389/fphar.2023.1151244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 03/24/2023] [Indexed: 04/03/2023] Open
Abstract
Elevated levels of cholesterol in the blood can induce endothelial dysfunction, a condition characterized by impaired nitric oxide production and decreased vasodilatory capacity. Endothelial dysfunction can promote vascular disease, such as atherosclerosis, where macrophages accumulate in the vascular intima and fatty plaques form that impair normal blood flow in conduit arteries. Current pharmacological strategies to treat atherosclerosis mostly focus on lipid lowering to prevent high levels of plasma cholesterol that induce endothelial dysfunction and atherosclerosis. While this approach is effective for most patients with atherosclerosis, for some, lipid lowering is not enough to reduce their cardiovascular risk factors associated with atherosclerosis (e.g., hypertension, cardiac dysfunction, stroke, etc.). For such patients, additional strategies targeted at reducing endothelial dysfunction may be beneficial. One novel strategy to restore endothelial function and mitigate atherosclerosis risk is to enhance the activity of Ca2+-activated K+ (KCa) channels in the endothelium with positive gating modulator drugs. Here, we review the mechanism of action of these small molecules and discuss their ability to improve endothelial function. We then explore how this strategy could mitigate endothelial dysfunction in the context of atherosclerosis by examining how KCa modulators can improve cardiovascular function in other settings, such as aging and type 2 diabetes. Finally, we consider questions that will need to be addressed to determine whether KCa channel activation could be used as a long-term add-on to lipid lowering to augment atherosclerosis treatment, particularly in patients where lipid-lowering is not adequate to improve their cardiovascular health.
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Affiliation(s)
- O. Daniel Vera
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Heike Wulff
- Department of Pharmacology, School of Medicine, University of California, Davis, CA, United States
| | - Andrew P. Braun
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- *Correspondence: Andrew P. Braun,
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3
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Lin Y, Zhao YJ, Zhang HL, Hao WJ, Zhu RD, Wang Y, Hu W, Zhou RP. Regulatory role of KCa3.1 in immune cell function and its emerging association with rheumatoid arthritis. Front Immunol 2022; 13:997621. [PMID: 36275686 PMCID: PMC9580404 DOI: 10.3389/fimmu.2022.997621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 09/16/2022] [Indexed: 11/25/2022] Open
Abstract
Rheumatoid arthritis (RA) is a common autoimmune disease characterized by chronic inflammation. Immune dysfunction is an essential mechanism in the pathogenesis of RA and directly linked to synovial inflammation and cartilage/bone destruction. Intermediate conductance Ca2+-activated K+ channel (KCa3.1) is considered a significant regulator of proliferation, differentiation, and migration of immune cells by mediating Ca2+ signal transduction. Earlier studies have demonstrated abnormal activation of KCa3.1 in the peripheral blood and articular synovium of RA patients. Moreover, knockout of KCa3.1 reduced the severity of synovial inflammation and cartilage damage to a significant extent in a mouse collagen antibody-induced arthritis (CAIA) model. Accumulating evidence implicates KCa3.1 as a potential therapeutic target for RA. Here, we provide an overview of the KCa3.1 channel and its pharmacological properties, discuss the significance of KCa3.1 in immune cells and feasibility as a drug target for modulating the immune balance, and highlight its emerging role in pathological progression of RA.
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Affiliation(s)
- Yi Lin
- Department of Clinical Pharmacology, The Second Hospital of Anhui Medical University, Hefei, China
- Inflammation and Immune Mediated Diseases Laboratory of Anhui Province, Anhui Institute of Innovative Drugs, School of Pharmacy, Anhui Medical University, Hefei, China
| | - Ying-Jie Zhao
- Department of Clinical Pharmacology, The Second Hospital of Anhui Medical University, Hefei, China
| | - Hai-Lin Zhang
- Department of Clinical Pharmacology, The Second Hospital of Anhui Medical University, Hefei, China
- Inflammation and Immune Mediated Diseases Laboratory of Anhui Province, Anhui Institute of Innovative Drugs, School of Pharmacy, Anhui Medical University, Hefei, China
| | - Wen-Juan Hao
- Department of Clinical Pharmacology, The Second Hospital of Anhui Medical University, Hefei, China
- Inflammation and Immune Mediated Diseases Laboratory of Anhui Province, Anhui Institute of Innovative Drugs, School of Pharmacy, Anhui Medical University, Hefei, China
| | - Ren-Di Zhu
- Department of Clinical Pharmacology, The Second Hospital of Anhui Medical University, Hefei, China
- Inflammation and Immune Mediated Diseases Laboratory of Anhui Province, Anhui Institute of Innovative Drugs, School of Pharmacy, Anhui Medical University, Hefei, China
| | - Yan Wang
- Department of Clinical Pharmacology, The Second Hospital of Anhui Medical University, Hefei, China
- Inflammation and Immune Mediated Diseases Laboratory of Anhui Province, Anhui Institute of Innovative Drugs, School of Pharmacy, Anhui Medical University, Hefei, China
| | - Wei Hu
- Department of Clinical Pharmacology, The Second Hospital of Anhui Medical University, Hefei, China
- The Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Anhui Medical University, Hefei, China
- *Correspondence: Wei Hu, ; Ren-Peng Zhou,
| | - Ren-Peng Zhou
- Department of Clinical Pharmacology, The Second Hospital of Anhui Medical University, Hefei, China
- The Key Laboratory of Anti-inflammatory and Immune Medicine, Ministry of Education, Anhui Medical University, Hefei, China
- *Correspondence: Wei Hu, ; Ren-Peng Zhou,
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4
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Sarkar S. Microglial ion channels: Key players in non-cell autonomous neurodegeneration. Neurobiol Dis 2022; 174:105861. [PMID: 36115552 PMCID: PMC9617777 DOI: 10.1016/j.nbd.2022.105861] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 08/26/2022] [Accepted: 09/12/2022] [Indexed: 12/03/2022] Open
Abstract
Neuroinflammation is a critical pathophysiological hallmark of neurodegenerative disorders, including Alzheimer’s disease (AD), Parkinson’s disease (PD), and traumatic brain injury (TBI). Microglia, the first responders of the brain, are the drivers of this neuroinflammation. Microglial activation, leading to induction of pro-inflammatory factors, like Interleukin 1-β (IL-1β), Tumor necrosis factor-α (TNFα), nitrites, and others, have been shown to induce neurodegeneration. Non-steroidal anti-inflammatory drugs (NSAIDs) have been shown to reduce the risk of developing PD, but the mechanism underlying the microglial activation is still under active research. Recently, microglial ion channels have come to the forefront as potential drug targets in multiple neurodegenerative disorders, including AD and PD. Microglia expresses a variety of ion channels, including potassium channels, calcium channels, chloride channels, sodium channels, and proton channels. The diversity of channels present on microglia is responsible for the dynamic nature of these immune cells of the brain. These ion channels regulate microglial proliferation, chemotaxis, phagocytosis, antigen recognition and presentation, apoptosis, and cell signaling leading to inflammation, among other critical functions. Understanding the role of these ion channels and the signaling mechanism these channels regulate under pathological conditions is an active area of research. This review will be focusing on the roles of different microglial ion channels, and their potential role in regulating microglial functions in neurodegenerative disorders.
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Affiliation(s)
- Souvarish Sarkar
- Dept. of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
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5
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Dwivedi D, Bhalla US. Physiology and Therapeutic Potential of SK, H, and M Medium AfterHyperPolarization Ion Channels. Front Mol Neurosci 2021; 14:658435. [PMID: 34149352 PMCID: PMC8209339 DOI: 10.3389/fnmol.2021.658435] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 04/13/2021] [Indexed: 12/19/2022] Open
Abstract
SK, HCN, and M channels are medium afterhyperpolarization (mAHP)-mediating ion channels. The three channels co-express in various brain regions, and their collective action strongly influences cellular excitability. However, significant diversity exists in the expression of channel isoforms in distinct brain regions and various subcellular compartments, which contributes to an equally diverse set of specific neuronal functions. The current review emphasizes the collective behavior of the three classes of mAHP channels and discusses how these channels function together although they play specialized roles. We discuss the biophysical properties of these channels, signaling pathways that influence the activity of the three mAHP channels, various chemical modulators that alter channel activity and their therapeutic potential in treating various neurological anomalies. Additionally, we discuss the role of mAHP channels in the pathophysiology of various neurological diseases and how their modulation can alleviate some of the symptoms.
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Affiliation(s)
- Deepanjali Dwivedi
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bengaluru, India.,Department of Neurobiology, Harvard Medical School, Boston, MA, United States.,Stanley Center at the Broad, Cambridge, MA, United States
| | - Upinder S Bhalla
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bengaluru, India
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6
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Shim H, Brown BM, Singh L, Singh V, Fettinger JC, Yarov-Yarovoy V, Wulff H. The Trials and Tribulations of Structure Assisted Design of K Ca Channel Activators. Front Pharmacol 2019; 10:972. [PMID: 31616290 PMCID: PMC6764326 DOI: 10.3389/fphar.2019.00972] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Accepted: 07/29/2019] [Indexed: 11/13/2022] Open
Abstract
Calcium-activated K+ channels constitute attractive targets for the treatment of neurological and cardiovascular diseases. To explain why certain 2-aminobenzothiazole/oxazole-type KCa activators (SKAs) are KCa3.1 selective we previously generated homology models of the C-terminal calmodulin-binding domain (CaM-BD) of KCa3.1 and KCa2.3 in complex with CaM using Rosetta modeling software. We here attempted to employ this atomistic level understanding of KCa activator binding to switch selectivity around and design KCa2.2 selective activators as potential anticonvulsants. In this structure-based drug design approach we used RosettaLigand docking and carefully compared the binding poses of various SKA compounds in the KCa2.2 and KCa3.1 CaM-BD/CaM interface pocket. Based on differences between residues in the KCa2.2 and KCa.3.1 models we virtually designed 168 new SKA compounds. The compounds that were predicted to be both potent and KCa2.2 selective were synthesized, and their activity and selectivity tested by manual or automated electrophysiology. However, we failed to identify any KCa2.2 selective compounds. Based on the full-length KCa3.1 structure it was recently demonstrated that the C-terminal crystal dimer was an artefact and suggested that the "real" binding pocket for the KCa activators is located at the S4-S5 linker. We here confirmed this structural hypothesis through mutagenesis and now offer a new, corrected binding site model for the SKA-type KCa channel activators. SKA-111 (5-methylnaphtho[1,2-d]thiazol-2-amine) is binding in the interface between the CaM N-lobe and the S4-S5 linker where it makes van der Waals contacts with S181 and L185 in the S45A helix of KCa3.1.
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Affiliation(s)
- Heesung Shim
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States.,Department of Chemistry, University of California, Davis, Davis, CA, United States
| | - Brandon M Brown
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Latika Singh
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Vikrant Singh
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States
| | - James C Fettinger
- Department of Chemistry, University of California, Davis, Davis, CA, United States
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Heike Wulff
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States
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7
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Brown BM, Shim H, Christophersen P, Wulff H. Pharmacology of Small- and Intermediate-Conductance Calcium-Activated Potassium Channels. Annu Rev Pharmacol Toxicol 2019; 60:219-240. [PMID: 31337271 DOI: 10.1146/annurev-pharmtox-010919-023420] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The three small-conductance calcium-activated potassium (KCa2) channels and the related intermediate-conductance KCa3.1 channel are voltage-independent K+ channels that mediate calcium-induced membrane hyperpolarization. When intracellular calcium increases in the channel vicinity, it calcifies the flexible N lobe of the channel-bound calmodulin, which then swings over to the S4-S5 linker and opens the channel. KCa2 and KCa3.1 channels are highly druggable and offer multiple binding sites for venom peptides and small-molecule blockers as well as for positive- and negative-gating modulators. In this review, we briefly summarize the physiological role of KCa channels and then discuss the pharmacophores and the mechanism of action of the most commonly used peptidic and small-molecule KCa2 and KCa3.1 modulators. Finally, we describe the progress that has been made in advancing KCa3.1 blockers and KCa2.2 negative- and positive-gating modulators toward the clinic for neurological and cardiovascular diseases and discuss the remaining challenges.
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Affiliation(s)
- Brandon M Brown
- Department of Pharmacology, University of California, Davis, California 95616, USA;
| | - Heesung Shim
- Department of Pharmacology, University of California, Davis, California 95616, USA;
| | | | - Heike Wulff
- Department of Pharmacology, University of California, Davis, California 95616, USA;
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8
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Ohya S, Kito H. Ca 2+-Activated K + Channel K Ca3.1 as a Therapeutic Target for Immune Disorders. Biol Pharm Bull 2018; 41:1158-1163. [PMID: 30068864 DOI: 10.1248/bpb.b18-00078] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In lymphoid and myeloid cells, membrane hyperpolarization by the opening of K+ channels increases the activity of Ca2+ release-activated Ca2+ (CRAC) channels and transient receptor potential (TRP) Ca2+ channels. The intermediate-conductance Ca2+-activated K+ channel KCa3.1 plays an important role in cell proliferation, differentiation, migration, and cytokine production in innate and adaptive immune systems. KCa3.1 is therefore an attractive therapeutic target for allergic, inflammatory, and autoimmune disorders. In the past several years, studies have provided new insights into 1) KCa3.1 pharmacology and its auxiliary regulators; 2) post-transcriptional and proteasomal regulation of KCa3.1; 3) KCa3.1 as a regulator of immune cell migration, cytokine production, and phenotypic polarization; 4) the role of KCa3.1 in the phosphorylation and nuclear translocation of Smad2/3; and 5) KCa3.1 as a therapeutic target for cancer immunotherapy. In this review, we have assembled a comprehensive overview of current research on the physiological and pathophysiological significance of KCa3.1 in the immune system.
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Affiliation(s)
- Susumu Ohya
- Department of Pharmacology, Graduate School of Medical Sciences, Nagoya City University
| | - Hiroaki Kito
- Department of Pharmacology, Graduate School of Medical Sciences, Nagoya City University
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9
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Kshatri AS, Gonzalez-Hernandez A, Giraldez T. Physiological Roles and Therapeutic Potential of Ca 2+ Activated Potassium Channels in the Nervous System. Front Mol Neurosci 2018; 11:258. [PMID: 30104956 PMCID: PMC6077210 DOI: 10.3389/fnmol.2018.00258] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 07/06/2018] [Indexed: 12/21/2022] Open
Abstract
Within the potassium ion channel family, calcium activated potassium (KCa) channels are unique in their ability to couple intracellular Ca2+ signals to membrane potential variations. KCa channels are diversely distributed throughout the central nervous system and play fundamental roles ranging from regulating neuronal excitability to controlling neurotransmitter release. The physiological versatility of KCa channels is enhanced by alternative splicing and co-assembly with auxiliary subunits, leading to fundamental differences in distribution, subunit composition and pharmacological profiles. Thus, understanding specific KCa channels’ mechanisms in neuronal function is challenging. Based on their single channel conductance, KCa channels are divided into three subtypes: small (SK, 4–14 pS), intermediate (IK, 32–39 pS) and big potassium (BK, 200–300 pS) channels. This review describes the biophysical characteristics of these KCa channels, as well as their physiological roles and pathological implications. In addition, we also discuss the current pharmacological strategies and challenges to target KCa channels for the treatment of various neurological and psychiatric disorders.
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Affiliation(s)
- Aravind S Kshatri
- Department of Basic Medical Sciences, Medical School, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologias Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Alberto Gonzalez-Hernandez
- Department of Basic Medical Sciences, Medical School, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologias Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Teresa Giraldez
- Department of Basic Medical Sciences, Medical School, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologias Biomedicas, Universidad de La Laguna, Tenerife, Spain
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10
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Lee CH, MacKinnon R. Activation mechanism of a human SK-calmodulin channel complex elucidated by cryo-EM structures. Science 2018; 360:508-513. [PMID: 29724949 DOI: 10.1126/science.aas9466] [Citation(s) in RCA: 123] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 03/16/2018] [Indexed: 12/17/2022]
Abstract
Small-conductance Ca2+-activated K+ (SK) channels mediate neuron excitability and are associated with synaptic transmission and plasticity. They also regulate immune responses and the size of blood cells. Activation of SK channels requires calmodulin (CaM), but how CaM binds and opens SK channels has been unclear. Here we report cryo-electron microscopy (cryo-EM) structures of a human SK4-CaM channel complex in closed and activated states at 3.4- and 3.5-angstrom resolution, respectively. Four CaM molecules bind to one channel tetramer. Each lobe of CaM serves a distinct function: The C-lobe binds to the channel constitutively, whereas the N-lobe interacts with the S4-S5 linker in a Ca2+-dependent manner. The S4-S5 linker, which contains two distinct helices, undergoes conformational changes upon CaM binding to open the channel pore. These structures reveal the gating mechanism of SK channels and provide a basis for understanding SK channel pharmacology.
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Affiliation(s)
- Chia-Hsueh Lee
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA.
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11
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Cho LTY, Alexandrou AJ, Torella R, Knafels J, Hobbs J, Taylor T, Loucif A, Konopacka A, Bell S, Stevens EB, Pandit J, Horst R, Withka JM, Pryde DC, Liu S, Young GT. An Intracellular Allosteric Modulator Binding Pocket in SK2 Ion Channels Is Shared by Multiple Chemotypes. Structure 2018; 26:533-544.e3. [PMID: 29576321 DOI: 10.1016/j.str.2018.02.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 12/03/2017] [Accepted: 02/23/2018] [Indexed: 01/22/2023]
Abstract
Small conductance potassium (SK) ion channels define neuronal firing rates by conducting the after-hyperpolarization current. They are key targets in developing therapies where neuronal firing rates are dysfunctional, such as in epilepsy, Parkinson's, and amyotrophic lateral sclerosis (ALS). Here, we characterize a binding pocket situated at the intracellular interface of SK2 and calmodulin, which we show to be shared by multiple small-molecule chemotypes. Crystallization of this complex revealed that riluzole (approved for ALS) and an analog of the anti-ataxic agent (4-chloro-phenyl)-[2-(3,5-dimethyl-pyrazol-1-yl)-pyrimidin-4-yl]-amine (CyPPA) bind to and allosterically modulate via this site. Solution-state nuclear magnetic resonance demonstrates that riluzole, NS309, and CyPPA analogs bind at this bipartite pocket. We demonstrate, by patch-clamp electrophysiology, that both classes of ligand interact with overlapping but distinct residues within this pocket. These data define a clinically important site, laying the foundations for further studies of the mechanism of action of riluzole and related molecules.
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Affiliation(s)
- Lily T-Y Cho
- Pfizer Neuroscience and Pain Research Unit, Granta Park, Great Abington, Cambridge CB21 6GS, UK
| | - Aristos J Alexandrou
- Pfizer Neuroscience and Pain Research Unit, Granta Park, Great Abington, Cambridge CB21 6GS, UK
| | - Rubben Torella
- Pfizer Worldwide Medicinal Chemistry, Neuroscience and Pain Research Unit, Granta Park, Great Abington, Cambridge CB21 6GS, UK
| | - John Knafels
- Pfizer Structural Biology and Biophysics, Groton, Eastern Point Road, Groton, CT 06340, USA
| | - Jake Hobbs
- Pfizer Neuroscience and Pain Research Unit, Granta Park, Great Abington, Cambridge CB21 6GS, UK
| | - Toni Taylor
- Pfizer Neuroscience and Pain Research Unit, Granta Park, Great Abington, Cambridge CB21 6GS, UK
| | - Alex Loucif
- Pfizer Neuroscience and Pain Research Unit, Granta Park, Great Abington, Cambridge CB21 6GS, UK
| | - Agnieszka Konopacka
- Pfizer Neuroscience and Pain Research Unit, Granta Park, Great Abington, Cambridge CB21 6GS, UK
| | - Sigourney Bell
- Pfizer Neuroscience and Pain Research Unit, Granta Park, Great Abington, Cambridge CB21 6GS, UK
| | - Edward B Stevens
- Pfizer Neuroscience and Pain Research Unit, Granta Park, Great Abington, Cambridge CB21 6GS, UK
| | - Jay Pandit
- Pfizer Structural Biology and Biophysics, Groton, Eastern Point Road, Groton, CT 06340, USA
| | - Reto Horst
- Pfizer Structural Biology and Biophysics, Groton, Eastern Point Road, Groton, CT 06340, USA
| | - Jane M Withka
- Pfizer Structural Biology and Biophysics, Groton, Eastern Point Road, Groton, CT 06340, USA
| | - David C Pryde
- Pfizer Worldwide Medicinal Chemistry, Neuroscience and Pain Research Unit, Granta Park, Great Abington, Cambridge CB21 6GS, UK
| | - Shenping Liu
- Pfizer Structural Biology and Biophysics, Groton, Eastern Point Road, Groton, CT 06340, USA.
| | - Gareth T Young
- Pfizer Neuroscience and Pain Research Unit, Granta Park, Great Abington, Cambridge CB21 6GS, UK.
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12
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Mathew John C, Khaddaj Mallat R, George G, Kim T, Mishra RC, Braun AP. Pharmacologic targeting of endothelial Ca 2+-activated K + channels: A strategy to improve cardiovascular function. Channels (Austin) 2018; 12:126-136. [PMID: 29577810 PMCID: PMC5972810 DOI: 10.1080/19336950.2018.1454814] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 03/15/2018] [Indexed: 12/17/2022] Open
Abstract
Endothelial small and intermediate-conductance, Ca2+-activated K+ channels (KCa2.3 and KCa3.1, respectively) play an important role in the regulation of vascular function and systemic blood pressure. Growing evidence indicates that they are intimately involved in agonist-evoked vasodilation of small resistance arteries throughout the circulation. Small molecule activators of KCa2.x and 3.1 channels, such as SKA-31, can acutely inhibit myogenic tone in isolated resistance arteries, induce effective vasodilation in intact vascular beds, such as the coronary circulation, and acutely decrease systemic blood pressure in vivo. The blood pressure-lowering effect of SKA-31, and early indications of improvement in endothelial dysfunction suggest that endothelial KCa channel activators could eventually be developed into a new class of endothelial targeted agents to combat hypertension or atherosclerosis. This review summarises recent insights into the activation of endothelial Ca2+ activated K+ channels in various vascular beds, and how tools, such as SKA-31, may be beneficial in disease-related conditions.
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Affiliation(s)
- Cini Mathew John
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Rayan Khaddaj Mallat
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Grace George
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Taeyeob Kim
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Ramesh C. Mishra
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Andrew P. Braun
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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13
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Affiliation(s)
- Brandon M Brown
- a Department of Pharmacology , University of California, Davis , Davis , CA , USA
| | - Heesung Shim
- a Department of Pharmacology , University of California, Davis , Davis , CA , USA
| | - Heike Wulff
- a Department of Pharmacology , University of California, Davis , Davis , CA , USA
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