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Lee N, Kim S, Lee NY, Jo H, Jeong P, Pagire HS, Pagire SH, Ahn JH, Jin MS, Park CS. Activation mechanism and novel binding sites of the BK Ca channel activator CTIBD. Life Sci Alliance 2024; 7:e202402621. [PMID: 39089879 PMCID: PMC11294680 DOI: 10.26508/lsa.202402621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 07/12/2024] [Accepted: 07/15/2024] [Indexed: 08/04/2024] Open
Abstract
The large-conductance calcium-activated potassium (BKCa) channel, which is crucial for urinary bladder smooth muscle relaxation, is a potential target for overactive bladder treatment. Our prior work unveiled CTIBD as a promising BKCa channel activator, altering V 1/2 and G max This study investigates CTIBD's activation mechanism, revealing its independence from the Ca2+ and membrane voltage sensing of the BKCa channel. Cryo-electron microscopy disclosed that two CTIBD molecules bind to hydrophobic regions on the extracellular side of the lipid bilayer. Key residues (W22, W203, and F266) are important for CTIBD binding, and their replacement with alanine reduces CTIBD-mediated channel activation. The triple-mutant (W22A/W203A/F266A) channel showed the smallest V 1/2 shift with a minimal impact on activation and deactivation kinetics by CTIBD. At the single-channel level, CTIBD treatment was much less effective at increasing P o in the triple mutant, mainly because of a drastically increased dissociation rate compared with the WT. These findings highlight CTIBD's mechanism, offering crucial insights for developing small-molecule treatments for BKCa-related pathophysiological conditions.
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Affiliation(s)
- Narasaem Lee
- https://ror.org/024kbgz78 School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Subin Kim
- https://ror.org/024kbgz78 School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Na Young Lee
- https://ror.org/024kbgz78 School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Heeji Jo
- https://ror.org/024kbgz78 School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | | | - Haushabhau S Pagire
- https://ror.org/024kbgz78 Department of Chemistry, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Suvarna H Pagire
- https://ror.org/024kbgz78 Department of Chemistry, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Jin Hee Ahn
- https://ror.org/024kbgz78 Department of Chemistry, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Mi Sun Jin
- https://ror.org/024kbgz78 School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Chul-Seung Park
- https://ror.org/024kbgz78 School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
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2
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Barenco-Marins TS, Seara FAC, Ponte CG, Nascimento JHM. Pulmonary Circulation Under Pressure: Pathophysiological and Therapeutic Implications of BK Channel. Cardiovasc Drugs Ther 2023:10.1007/s10557-023-07503-7. [PMID: 37624526 DOI: 10.1007/s10557-023-07503-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 08/10/2023] [Indexed: 08/26/2023]
Abstract
The large-conductance Ca2+-activated K+ (BK) channel is widely expressed in the pulmonary blood vessels and plays a significant role in regulating pulmonary vascular tonus. It opens under membrane depolarization, increased intracellular Ca+2 concentration, and chronic hypoxia, resulting in massive K+ efflux, membrane hyperpolarization, decreased L-type Ca+2 channel opening, and smooth muscle relaxation. Several reports have demonstrated an association between BK channel dysfunction and pulmonary hypertension (PH) development. Decreased BK channel subunit expression and impaired regulation by paracrine hormones result in decreased BK channel opening, increased pulmonary vascular resistance, and pulmonary arterial pressure being the cornerstone of PH. The resulting right ventricular pressure overload ultimately leads to ventricular remodeling and failure. Therefore, it is unsurprising that the BK channel has arisen as a potential target for treating PH. Recently, a series of selective, synthetic BK channel agonists have proven effective in attenuating the pathophysiological progression of PH without adverse effects in animal models.
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Affiliation(s)
- Thais S Barenco-Marins
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal Do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
- Programa de Pós-Graduação Em Cardiologia, Universidade Federal Do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Fernando A C Seara
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal Do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
- Instituto de Ciências Biológicas E da Saúde, Universidade Federal Rural Do Rio de Janeiro, Seropédica, RJ, Brazil.
- Programa de Pós-Graduação Multicêntrico Em Ciências Fisiológicas, Sociedade Brasileira de Fisiologia, São Paulo, Brazil.
| | - Cristiano G Ponte
- Instituto Federal de Educação, Ciências e Tecnologia do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Jose H M Nascimento
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal Do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
- Programa de Pós-Graduação Em Cardiologia, Universidade Federal Do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
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3
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Silvestro M, Iannone LF, Orologio I, Tessitore A, Tedeschi G, Geppetti P, Russo A. Migraine Treatment: Towards New Pharmacological Targets. Int J Mol Sci 2023; 24:12268. [PMID: 37569648 PMCID: PMC10418850 DOI: 10.3390/ijms241512268] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/28/2023] [Accepted: 07/29/2023] [Indexed: 08/13/2023] Open
Abstract
Migraine is a debilitating neurological condition affecting millions of people worldwide. Until a few years ago, preventive migraine treatments were based on molecules with pleiotropic targets, developed for other indications, and discovered by serendipity to be effective in migraine prevention, although often burdened by tolerability issues leading to low adherence. However, the progresses in unravelling the migraine pathophysiology allowed identifying novel putative targets as calcitonin gene-related peptide (CGRP). Nevertheless, despite the revolution brought by CGRP monoclonal antibodies and gepants, a significant percentage of patients still remains burdened by an unsatisfactory response, suggesting that other pathways may play a critical role, with an extent of involvement varying among different migraine patients. Specifically, neuropeptides of the CGRP family, such as adrenomedullin and amylin; molecules of the secretin family, such as pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP); receptors, such as transient receptor potential (TRP) channels; intracellular downstream determinants, such as potassium channels, but also the opioid system and the purinergic pathway, have been suggested to be involved in migraine pathophysiology. The present review provides an overview of these pathways, highlighting, based on preclinical and clinical evidence, as well as provocative studies, their potential role as future targets for migraine preventive treatment.
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Affiliation(s)
- Marcello Silvestro
- Headache Centre, Department of Advanced Medical and Surgical Sciences, University of Campania “Luigi Vanvitelli”, 80138 Naples, Italy; (I.O.); (A.T.); (G.T.)
- Advanced MRI Neuroimaging Centre, Department of Advanced Medical and Surgical Sciences, University of Campania “Luigi Vanvitelli”, 80138 Naples, Italy;
| | - Luigi Francesco Iannone
- Headache Centre and Clinical Pharmacology Unit, Careggi University Hospital Florence, 50134 Florence, Italy; (L.F.I.); (P.G.)
| | - Ilaria Orologio
- Headache Centre, Department of Advanced Medical and Surgical Sciences, University of Campania “Luigi Vanvitelli”, 80138 Naples, Italy; (I.O.); (A.T.); (G.T.)
| | - Alessandro Tessitore
- Headache Centre, Department of Advanced Medical and Surgical Sciences, University of Campania “Luigi Vanvitelli”, 80138 Naples, Italy; (I.O.); (A.T.); (G.T.)
- Advanced MRI Neuroimaging Centre, Department of Advanced Medical and Surgical Sciences, University of Campania “Luigi Vanvitelli”, 80138 Naples, Italy;
| | - Gioacchino Tedeschi
- Headache Centre, Department of Advanced Medical and Surgical Sciences, University of Campania “Luigi Vanvitelli”, 80138 Naples, Italy; (I.O.); (A.T.); (G.T.)
- Advanced MRI Neuroimaging Centre, Department of Advanced Medical and Surgical Sciences, University of Campania “Luigi Vanvitelli”, 80138 Naples, Italy;
| | - Pierangelo Geppetti
- Headache Centre and Clinical Pharmacology Unit, Careggi University Hospital Florence, 50134 Florence, Italy; (L.F.I.); (P.G.)
| | - Antonio Russo
- Advanced MRI Neuroimaging Centre, Department of Advanced Medical and Surgical Sciences, University of Campania “Luigi Vanvitelli”, 80138 Naples, Italy;
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4
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Involvement of Potassium Channel Signalling in Migraine Pathophysiology. Pharmaceuticals (Basel) 2023; 16:ph16030438. [PMID: 36986537 PMCID: PMC10057509 DOI: 10.3390/ph16030438] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 02/28/2023] [Accepted: 03/06/2023] [Indexed: 03/17/2023] Open
Abstract
Migraine is a primary headache disorder ranked as the leading cause of years lived with disability among individuals younger than 50 years. The aetiology of migraine is complex and might involve several molecules of different signalling pathways. Emerging evidence implicates potassium channels, predominantly ATP-sensitive potassium (KATP) channels and large (big) calcium-sensitive potassium (BKCa) channels in migraine attack initiation. Basic neuroscience revealed that stimulation of potassium channels activated and sensitized trigeminovascular neurons. Clinical trials showed that administration of potassium channel openers caused headache and migraine attack associated with dilation of cephalic arteries. The present review highlights the molecular structure and physiological function of KATP and BKCa channels, presents recent insights into the role of potassium channels in migraine pathophysiology, and discusses possible complementary effects and interdependence of potassium channels in migraine attack initiation.
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5
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Jiang L, Li J, Reilly S, Xin H, Guo N, Zhang X. Role of organellar Ca2+-activated K+ channels in disease development. Life Sci 2023; 316:121433. [PMID: 36708987 DOI: 10.1016/j.lfs.2023.121433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 01/16/2023] [Accepted: 01/19/2023] [Indexed: 01/27/2023]
Abstract
The organellar Ca2+-activated K+ channels share a similar ability to transfer the alteration of Ca2+ concentration to membrane conductance of potassium. Multiple effects of Ca2+-activated K+ channels on cell metabolism and complex signaling pathways during organ development have been explored. The organellar Ca2+-activated K+ channels are able to control the ionic equilibrium and are always associated with oxidative stress in different organelles and the whole cells. Some drugs targeting Ca2+-activated K+ channels have been tested for various diseases in clinical trials. In this review, the known roles of organellar Ca2+-activated K+ channels were described, and their effects on different diseases, particularly on diabetes, cardiovascular diseases, and neurological diseases were discussed. It was attempted to summarize the currently known operational modes with the involvement of organellar Ca2+-activated K+ channels. This review may assist scholars to more comprehensively understand organellar Ca2+-activated K+ channels and related diseases.
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Affiliation(s)
- Lan Jiang
- Department of Pharmacology, School of Pharmacy, Fudan University, Shanghai, China
| | - Jiawei Li
- Department of Pharmacology, School of Pharmacy, Fudan University, Shanghai, China
| | - Svetlana Reilly
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Hong Xin
- Department of Pharmacology, School of Pharmacy, Fudan University, Shanghai, China
| | - Nan Guo
- Department of Pharmacy, Minhang hospital, Fudan University, Shanghai, China.
| | - Xuemei Zhang
- Department of Pharmacology, School of Pharmacy, Fudan University, Shanghai, China.
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6
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Ancatén-González C, Segura I, Alvarado-Sánchez R, Chávez AE, Latorre R. Ca 2+- and Voltage-Activated K + (BK) Channels in the Nervous System: One Gene, a Myriad of Physiological Functions. Int J Mol Sci 2023; 24:3407. [PMID: 36834817 PMCID: PMC9967218 DOI: 10.3390/ijms24043407] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 01/18/2023] [Accepted: 01/21/2023] [Indexed: 02/11/2023] Open
Abstract
BK channels are large conductance potassium channels characterized by four pore-forming α subunits, often co-assembled with auxiliary β and γ subunits to regulate Ca2+ sensitivity, voltage dependence and gating properties. BK channels are abundantly expressed throughout the brain and in different compartments within a single neuron, including axons, synaptic terminals, dendritic arbors, and spines. Their activation produces a massive efflux of K+ ions that hyperpolarizes the cellular membrane. Together with their ability to detect changes in intracellular Ca2+ concentration, BK channels control neuronal excitability and synaptic communication through diverse mechanisms. Moreover, increasing evidence indicates that dysfunction of BK channel-mediated effects on neuronal excitability and synaptic function has been implicated in several neurological disorders, including epilepsy, fragile X syndrome, mental retardation, and autism, as well as in motor and cognitive behavior. Here, we discuss current evidence highlighting the physiological importance of this ubiquitous channel in regulating brain function and its role in the pathophysiology of different neurological disorders.
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Affiliation(s)
- Carlos Ancatén-González
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
- Programa de Doctorado en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Ignacio Segura
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Rosangelina Alvarado-Sánchez
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
- Doctorado en Ciencias Mención Biofísica y Biología Computacional, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Andrés E. Chávez
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
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7
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Potassium channelopathies associated with epilepsy-related syndromes and directions for therapeutic intervention. Biochem Pharmacol 2023; 208:115413. [PMID: 36646291 DOI: 10.1016/j.bcp.2023.115413] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 01/06/2023] [Accepted: 01/09/2023] [Indexed: 01/15/2023]
Abstract
A number of mutations to members of several CNS potassium (K) channel families have been identified which result in rare forms of neonatal onset epilepsy, or syndromes of which one prominent characteristic is a form of epilepsy. Benign Familial Neonatal Convulsions or Seizures (BFNC or BFNS), also referred to as Self-Limited Familial Neonatal Epilepsy (SeLNE), results from mutations in 2 members of the KV7 family (KCNQ) of K channels; while generally self-resolving by about 15 weeks of age, these mutations significantly increase the probability of generalized seizure disorders in the adult, in some cases they result in more severe developmental syndromes. Epilepsy of Infancy with Migrating Focal Seizures (EIMSF), or Migrating Partial Seizures of Infancy (MMPSI), is a rare severe form of epilepsy linked primarily to gain of function mutations in a member of the sodium-dependent K channel family, KCNT1 or SLACK. Finally, KCNMA1 channelopathies, including Liang-Wang syndrome (LIWAS), are rare combinations of neurological symptoms including seizure, movement abnormalities, delayed development and intellectual disabilities, with Liang-Wang syndrome an extremely serious polymalformative syndrome with a number of neurological sequelae including epilepsy. These are caused by mutations in the pore-forming subunit of the large-conductance calcium-activated K channel (BK channel) KCNMA1. The identification of these rare but significant channelopathies has resulted in a resurgence of interest in their treatment by direct pharmacological or genetic modulation. We will briefly review the genetics, biophysics and pharmacology of these K channels, their linkage with the 3 syndromes described above, and efforts to more effectively target these syndromes.
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8
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Ca 2+-Activated K + Channels and the Regulation of the Uteroplacental Circulation. Int J Mol Sci 2023; 24:ijms24021349. [PMID: 36674858 PMCID: PMC9867535 DOI: 10.3390/ijms24021349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 01/06/2023] [Accepted: 01/08/2023] [Indexed: 01/13/2023] Open
Abstract
Adequate uteroplacental blood supply is essential for the development and growth of the placenta and fetus during pregnancy. Aberrant uteroplacental perfusion is associated with pregnancy complications such as preeclampsia, fetal growth restriction (FGR), and gestational diabetes. The regulation of uteroplacental blood flow is thus vital to the well-being of the mother and fetus. Ca2+-activated K+ (KCa) channels of small, intermediate, and large conductance participate in setting and regulating the resting membrane potential of vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) and play a critical role in controlling vascular tone and blood pressure. KCa channels are important mediators of estrogen/pregnancy-induced adaptive changes in the uteroplacental circulation. Activation of the channels hyperpolarizes uteroplacental VSMCs/ECs, leading to attenuated vascular tone, blunted vasopressor responses, and increased uteroplacental blood flow. However, the regulation of uteroplacental vascular function by KCa channels is compromised in pregnancy complications. This review intends to provide a comprehensive overview of roles of KCa channels in the regulation of the uteroplacental circulation under physiological and pathophysiological conditions.
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9
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Ochoa SV, Otero L, Aristizabal-Pachon AF, Hinostroza F, Carvacho I, Torres YP. Hypoxic Regulation of the Large-Conductance, Calcium and Voltage-Activated Potassium Channel, BK. Front Physiol 2022; 12:780206. [PMID: 35002762 PMCID: PMC8727448 DOI: 10.3389/fphys.2021.780206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 11/15/2021] [Indexed: 11/15/2022] Open
Abstract
Hypoxia is a condition characterized by a reduction of cellular oxygen levels derived from alterations in oxygen balance. Hypoxic events trigger changes in cell-signaling cascades, oxidative stress, activation of pro-inflammatory molecules, and growth factors, influencing the activity of various ion channel families and leading to diverse cardiovascular diseases such as myocardial infarction, ischemic stroke, and hypertension. The large-conductance, calcium and voltage-activated potassium channel (BK) has a central role in the mechanism of oxygen (O2) sensing and its activity has been related to the hypoxic response. BK channels are ubiquitously expressed, and they are composed by the pore-forming α subunit and the regulatory subunits β (β1–β4), γ (γ1–γ4), and LINGO1. The modification of biophysical properties of BK channels by β subunits underly a myriad of physiological function of these proteins. Hypoxia induces tissue-specific modifications of BK channel α and β subunits expression. Moreover, hypoxia modifies channel activation kinetics and voltage and/or calcium dependence. The reported effects on the BK channel properties are associated with events such as the increase of reactive oxygen species (ROS) production, increases of intracellular Calcium ([Ca2+]i), the regulation by Hypoxia-inducible factor 1α (HIF-1α), and the interaction with hemeproteins. Bronchial asthma, chronic obstructive pulmonary diseases (COPD), and obstructive sleep apnea (OSA), among others, can provoke hypoxia. Untreated OSA patients showed a decrease in BK-β1 subunit mRNA levels and high arterial tension. Treatment with continuous positive airway pressure (CPAP) upregulated β1 subunit mRNA level, decreased arterial pressures, and improved endothelial function coupled with a reduction in morbidity and mortality associated with OSA. These reports suggest that the BK channel has a role in the response involved in hypoxia-associated hypertension derived from OSA. Thus, this review aims to describe the mechanisms involved in the BK channel activation after a hypoxic stimulus and their relationship with disorders like OSA. A deep understanding of the molecular mechanism involved in hypoxic response may help in the therapeutic approaches to treat the pathological processes associated with diseases involving cellular hypoxia.
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Affiliation(s)
- Sara V Ochoa
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia.,Semillero de Investigación, Biofísica y Fisiología de Canales Iónicos, Pontificia Universidad Javeriana, Bogotá, Colombia
| | - Liliana Otero
- Center of Dental Research Dentistry Faculty, Pontificia Universidad Javeriana, Bogotá, Colombia
| | | | - Fernando Hinostroza
- Department of Biology and Chemistry, Faculty of Basic Sciences, Universidad Católica del Maule, Talca, Chile.,Centro de Investigación de Estudios Avanzados del Maule, CIEAM, Vicerrectoría de Investigación y Postgrado, Universidad Católica del Maule, Talca, Chile.,Facultad de Ciencias de la Salud, Centro de Investigación en Neuropsicología y Neurociencias Cognitivas, Universidad Católica del Maule, Talca, Chile
| | - Ingrid Carvacho
- Department of Biology and Chemistry, Faculty of Basic Sciences, Universidad Católica del Maule, Talca, Chile
| | - Yolima P Torres
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia.,Semillero de Investigación, Biofísica y Fisiología de Canales Iónicos, Pontificia Universidad Javeriana, Bogotá, Colombia
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10
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Wu Y, Xu M, Wang P, Syeda AKR, Huang P, Dong XP. Lysosomal potassium channels. Cell Calcium 2022; 102:102536. [PMID: 35016151 DOI: 10.1016/j.ceca.2022.102536] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 01/04/2022] [Accepted: 01/05/2022] [Indexed: 12/21/2022]
Abstract
The lysosome is an important membrane-bound acidic organelle that is regarded as the degradative center as well as multifunctional signaling hub. It digests unwanted macromolecules, damaged organelles, microbes, and other materials derived from endocytosis, autophagy, and phagocytosis. To function properly, the ionic homeostasis and membrane potential of the lysosome are strictly regulated by transporters and ion channels. As the most abundant cation inside the cell, potassium ions (K+) are vital for lysosomal membrane potential and lysosomal calcium (Ca2+) signaling. However, our understanding about how lysosomal K+homeostasis is regulated and what are the functions of K+in the lysosome is very limited. Currently, two lysosomal K+channels have been identified: large-conductance Ca2+-activated K+channel (BK) and transmembrane Protein 175 (TMEM175). In this review, we summarize recent development in our understanding of K+ homeostasis and K+channels in the lysosome. We hope to guide the readers into a more in-depth discussion of lysosomal K+ channels in lysosomal physiology and human diseases.
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Affiliation(s)
- Yi Wu
- Collaborative Innovation Center for Biomedicine, Shanghai University of Medicine and Health Sciences, 279 Zhouzhu Rd, Shanghai 201318, China; School of Pharmacy, Shanghai University of Medicine and Health Sciences, 279 Zhouzhu Rd, Shanghai 201318, China
| | - Mengnan Xu
- Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, Nova NS B3H 4R2, Canada
| | - Pingping Wang
- Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, Nova NS B3H 4R2, Canada
| | - Alia Kazim Rizvi Syeda
- Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, Nova NS B3H 4R2, Canada
| | - Peng Huang
- Collaborative Innovation Center for Biomedicine, Shanghai University of Medicine and Health Sciences, 279 Zhouzhu Rd, Shanghai 201318, China; School of Clinical Medicine, Shanghai University of Medicine and Health Sciences, 279 Zhouzhu Rd, Shanghai 201318, China.
| | - Xian-Ping Dong
- Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, Nova NS B3H 4R2, Canada.
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11
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Estrogen-Induced Uterine Vasodilation in Pregnancy and Preeclampsia. MATERNAL-FETAL MEDICINE 2022; 4:52-60. [PMID: 35072088 PMCID: PMC8772435 DOI: 10.1097/fm9.0000000000000132] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 11/09/2021] [Indexed: 12/02/2022] Open
Abstract
Normal pregnancy is associated with dramatically increased estrogen biosynthesis whose role is believed to raise uterine blood flow to facilitate the bi-directional maternal-fetal exchanges of gases (O2 and CO2), to deliver nutrients, and exhaust wastes to support fetal development and survival. Constrained uterine blood flow in pregnancy is a leading cause of preeclampsia with fetal growth restriction, rendering investigations of uterine hemodynamics to hold a high promise to inform pathways as targets for therapeutic interventions for preeclampsia. The mechanisms of estrogen-induced uterine vasodilation in pregnancy have long been attributed to enhanced endothelium production of nitric oxide, but clinical trials targeting this pathway that dominates uterine hemodynamics have achieved no to little success. Emerging evidence has recently shown a novel proangiogenic vasodilatory role of hydrogen sulfide in regulating uterine hemodynamics in pregnancy and preeclampsia, provoking a new field of perinatal research in searching for alternative pathways for pregnancy disorders especially preeclampsia and intrauterine growth restriction. This minireview is intended to summarize the nitric oxide pathway and to discuss the emerging hydrogen sulfide pathway in modulating estrogen-induced uterine vasodilation in pregnancy and preeclampsia.
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12
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Jackson WF. Calcium-Dependent Ion Channels and the Regulation of Arteriolar Myogenic Tone. Front Physiol 2021; 12:770450. [PMID: 34819877 PMCID: PMC8607693 DOI: 10.3389/fphys.2021.770450] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 10/11/2021] [Indexed: 11/25/2022] Open
Abstract
Arterioles in the peripheral microcirculation regulate blood flow to and within tissues and organs, control capillary blood pressure and microvascular fluid exchange, govern peripheral vascular resistance, and contribute to the regulation of blood pressure. These important microvessels display pressure-dependent myogenic tone, the steady state level of contractile activity of vascular smooth muscle cells (VSMCs) that sets resting arteriolar internal diameter such that arterioles can both dilate and constrict to meet the blood flow and pressure needs of the tissues and organs that they perfuse. This perspective will focus on the Ca2+-dependent ion channels in the plasma and endoplasmic reticulum membranes of arteriolar VSMCs and endothelial cells (ECs) that regulate arteriolar tone. In VSMCs, Ca2+-dependent negative feedback regulation of myogenic tone is mediated by Ca2+-activated K+ (BKCa) channels and also Ca2+-dependent inactivation of voltage-gated Ca2+ channels (VGCC). Transient receptor potential subfamily M, member 4 channels (TRPM4); Ca2+-activated Cl− channels (CaCCs; TMEM16A/ANO1), Ca2+-dependent inhibition of voltage-gated K+ (KV) and ATP-sensitive K+ (KATP) channels; and Ca2+-induced-Ca2+ release through inositol 1,4,5-trisphosphate receptors (IP3Rs) participate in Ca2+-dependent positive-feedback regulation of myogenic tone. Calcium release from VSMC ryanodine receptors (RyRs) provide negative-feedback through Ca2+-spark-mediated control of BKCa channel activity, or positive-feedback regulation in cooperation with IP3Rs or CaCCs. In some arterioles, VSMC RyRs are silent. In ECs, transient receptor potential vanilloid subfamily, member 4 (TRPV4) channels produce Ca2+ sparklets that activate IP3Rs and intermediate and small conductance Ca2+ activated K+ (IKCa and sKCa) channels causing membrane hyperpolarization that is conducted to overlying VSMCs producing endothelium-dependent hyperpolarization and vasodilation. Endothelial IP3Rs produce Ca2+ pulsars, Ca2+ wavelets, Ca2+ waves and increased global Ca2+ levels activating EC sKCa and IKCa channels and causing Ca2+-dependent production of endothelial vasodilator autacoids such as NO, prostaglandin I2 and epoxides of arachidonic acid that mediate negative-feedback regulation of myogenic tone. Thus, Ca2+-dependent ion channels importantly contribute to many aspects of the regulation of myogenic tone in arterioles in the microcirculation.
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Affiliation(s)
- William F Jackson
- Department of Pharmacology and Toxicology, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, United States
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13
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Sancho M, Kyle BD. The Large-Conductance, Calcium-Activated Potassium Channel: A Big Key Regulator of Cell Physiology. Front Physiol 2021; 12:750615. [PMID: 34744788 PMCID: PMC8567177 DOI: 10.3389/fphys.2021.750615] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/29/2021] [Indexed: 12/01/2022] Open
Abstract
Large-conductance Ca2+-activated K+ channels facilitate the efflux of K+ ions from a variety of cells and tissues following channel activation. It is now recognized that BK channels undergo a wide range of pre- and post-translational modifications that can dramatically alter their properties and function. This has downstream consequences in affecting cell and tissue excitability, and therefore, function. While finding the “silver bullet” in terms of clinical therapy has remained elusive, ongoing research is providing an impressive range of viable candidate proteins and mechanisms that associate with and modulate BK channel activity, respectively. Here, we provide the hallmarks of BK channel structure and function generally, and discuss important milestones in the efforts to further elucidate the diverse properties of BK channels in its many forms.
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Affiliation(s)
- Maria Sancho
- Department of Pharmacology, University of Vermont, Burlington, VT, United States
| | - Barry D Kyle
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
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14
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Rockman ME, Vouga AG, Rothberg BS. Molecular mechanism of BK channel activation by the smooth muscle relaxant NS11021. J Gen Physiol 2021; 152:151593. [PMID: 32221543 PMCID: PMC7266150 DOI: 10.1085/jgp.201912506] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 02/12/2020] [Indexed: 12/31/2022] Open
Abstract
Large-conductance Ca2+-activated K+ channels (BK channels) are activated by cytosolic calcium and depolarized membrane potential under physiological conditions. Thus, these channels control electrical excitability in neurons and smooth muscle by gating K+ efflux and hyperpolarizing the membrane in response to Ca2+ signaling. Altered BK channel function has been linked to epilepsy, dyskinesia, and other neurological deficits in humans, making these channels a key target for drug therapies. To gain insight into mechanisms underlying pharmacological modulation of BK channel gating, here we studied mechanisms underlying activation of BK channels by the biarylthiourea derivative, NS11021, which acts as a smooth muscle relaxant. We observe that increasing NS11021 shifts the half-maximal activation voltage for BK channels toward more hyperpolarized voltages, in both the presence and nominal absence of Ca2+, suggesting that NS11021 facilitates BK channel activation primarily by a mechanism that is distinct from Ca2+ activation. 30 µM NS11021 slows the time course of BK channel deactivation at −200 mV by ∼10-fold compared with 0 µM NS11021, while having little effect on the time course of activation. This action is most pronounced at negative voltages, at which the BK channel voltage sensors are at rest. Single-channel kinetic analysis further shows that 30 µM NS11021 increases open probability by 62-fold and increases mean open time from 0.15 to 0.52 ms in the nominal absence of Ca2+ at voltages less than −60 mV, conditions in which BK voltage sensors are largely in the resting state. We could therefore account for the major activating effects of NS11021 by a scheme in which the drug primarily shifts the pore-gate equilibrium toward the open state.
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Affiliation(s)
- Michael E Rockman
- Department of Medical Genetics and Molecular Biochemistry, Temple University Lewis Katz School of Medicine, Philadelphia, PA
| | - Alexandre G Vouga
- Department of Medical Genetics and Molecular Biochemistry, Temple University Lewis Katz School of Medicine, Philadelphia, PA
| | - Brad S Rothberg
- Department of Medical Genetics and Molecular Biochemistry, Temple University Lewis Katz School of Medicine, Philadelphia, PA
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15
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Vouga AG, Rockman ME, Yan J, Jacobson MA, Rothberg BS. State-dependent inhibition of BK channels by the opioid agonist loperamide. J Gen Physiol 2021; 153:212539. [PMID: 34357374 PMCID: PMC8352719 DOI: 10.1085/jgp.202012834] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 04/19/2021] [Accepted: 07/08/2021] [Indexed: 12/20/2022] Open
Abstract
Large-conductance Ca2+-activated K+ (BK) channels control a range of physiological functions, and their dysfunction is linked to human disease. We have found that the widely used drug loperamide (LOP) can inhibit activity of BK channels composed of either α-subunits (BKα channels) or α-subunits plus the auxiliary γ1-subunit (BKα/γ1 channels), and here we analyze the molecular mechanism of LOP action. LOP applied at the cytosolic side of the membrane rapidly and reversibly inhibited BK current, an effect that appeared as a decay in voltage-activated BK currents. The apparent affinity for LOP decreased with hyperpolarization in a manner consistent with LOP behaving as an inhibitor of open, activated channels. Increasing LOP concentration reduced the half-maximal activation voltage, consistent with relative stabilization of the LOP-inhibited open state. Single-channel recordings revealed that LOP did not reduce unitary BK channel current, but instead decreased BK channel open probability and mean open times. LOP elicited use-dependent inhibition, in which trains of brief depolarizing steps lead to accumulated reduction of BK current, whereas single brief depolarizing steps do not. The principal effects of LOP on BK channel gating are described by a mechanism in which LOP acts as a state-dependent pore blocker. Our results suggest that therapeutic doses of LOP may act in part by inhibiting K+ efflux through intestinal BK channels.
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Affiliation(s)
- Alexandre G Vouga
- Department of Medical Genetics and Molecular Biochemistry, Temple University Lewis Katz School of Medicine, Philadelphia, PA
| | - Michael E Rockman
- Department of Medical Genetics and Molecular Biochemistry, Temple University Lewis Katz School of Medicine, Philadelphia, PA
| | - Jiusheng Yan
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX
| | - Marlene A Jacobson
- Moulder Center for Drug Discovery Research, Temple University School of Pharmacy, Philadelphia PA
| | - Brad S Rothberg
- Department of Medical Genetics and Molecular Biochemistry, Temple University Lewis Katz School of Medicine, Philadelphia, PA
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16
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Abstract
K+ channels enable potassium to flow across the membrane with great selectivity. There are four K+ channel families: voltage-gated K (Kv), calcium-activated (KCa), inwardly rectifying K (Kir), and two-pore domain potassium (K2P) channels. All four K+ channels are formed by subunits assembling into a classic tetrameric (4x1P = 4P for the Kv, KCa, and Kir channels) or tetramer-like (2x2P = 4P for the K2P channels) architecture. These subunits can either be the same (homomers) or different (heteromers), conferring great diversity to these channels. They share a highly conserved selectivity filter within the pore but show different gating mechanisms adapted for their function. K+ channels play essential roles in controlling neuronal excitability by shaping action potentials, influencing the resting membrane potential, and responding to diverse physicochemical stimuli, such as a voltage change (Kv), intracellular calcium oscillations (KCa), cellular mediators (Kir), or temperature (K2P).
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17
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Bazard P, Frisina RD, Acosta AA, Dasgupta S, Bauer MA, Zhu X, Ding B. Roles of Key Ion Channels and Transport Proteins in Age-Related Hearing Loss. Int J Mol Sci 2021; 22:6158. [PMID: 34200434 PMCID: PMC8201059 DOI: 10.3390/ijms22116158] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 05/30/2021] [Accepted: 05/31/2021] [Indexed: 12/25/2022] Open
Abstract
The auditory system is a fascinating sensory organ that overall, converts sound signals to electrical signals of the nervous system. Initially, sound energy is converted to mechanical energy via amplification processes in the middle ear, followed by transduction of mechanical movements of the oval window into electrochemical signals in the cochlear hair cells, and finally, neural signals travel to the central auditory system, via the auditory division of the 8th cranial nerve. The majority of people above 60 years have some form of age-related hearing loss, also known as presbycusis. However, the biological mechanisms of presbycusis are complex and not yet fully delineated. In the present article, we highlight ion channels and transport proteins, which are integral for the proper functioning of the auditory system, facilitating the diffusion of various ions across auditory structures for signal transduction and processing. Like most other physiological systems, hearing abilities decline with age, hence, it is imperative to fully understand inner ear aging changes, so ion channel functions should be further investigated in the aging cochlea. In this review article, we discuss key various ion channels in the auditory system and how their functions change with age. Understanding the roles of ion channels in auditory processing could enhance the development of potential biotherapies for age-related hearing loss.
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Affiliation(s)
- Parveen Bazard
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (A.A.A.); (S.D.); (M.A.B.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA
| | - Robert D. Frisina
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (A.A.A.); (S.D.); (M.A.B.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA
- Department Communication Sciences and Disorders, College of Behavioral & Communication Sciences, Tampa, FL 33620, USA
| | - Alejandro A. Acosta
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (A.A.A.); (S.D.); (M.A.B.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA
| | - Sneha Dasgupta
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (A.A.A.); (S.D.); (M.A.B.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA
| | - Mark A. Bauer
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (A.A.A.); (S.D.); (M.A.B.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA
| | - Xiaoxia Zhu
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (A.A.A.); (S.D.); (M.A.B.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA
| | - Bo Ding
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (A.A.A.); (S.D.); (M.A.B.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA
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18
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Cheng P, Qiu Z, Du Y. Potassium channels and autism spectrum disorder: An overview. Int J Dev Neurosci 2021; 81:479-491. [PMID: 34008235 DOI: 10.1002/jdn.10123] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 05/08/2021] [Accepted: 05/11/2021] [Indexed: 11/07/2022] Open
Abstract
Autism spectrum disorder (ASD) comprises a group of neurodevelopmental disorders characterized by impaired social interaction and communication, and restricted, repetitive patterns of behaviors, interests, or activities. It had been demonstrated that potassium channels played a key role in regulating neuronal excitability, which was closely associated with neurological diseases including epilepsy, ataxia, myoclonus, and psychiatric disorders. In recent years, a growing body of evidence from whole-genome sequencing and whole-exome sequencing had identified several ASD susceptibility genes of potassium channels in ASD subjects. Genetically dysfunction of potassium channels may be involved in altered neuronal excitability and abnormal brain function in the pathogenesis of ASD. This review summarizes current findings on the features of ASD-risk genes (KCND2, KCNQ2, KCNQ3, KCNH5, KCNJ2, KCNJ10, and KCNMA1) and further expatiate their potential role in the pathogenicity of ASD.
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Affiliation(s)
- Peipei Cheng
- Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zilong Qiu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China.,Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai, China
| | - Yasong Du
- Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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19
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Abstract
Potassium channels are the most diverse and ubiquitous family of ion channels found in cells. The Ca2+ and voltage gated members form a subfamily that play a variety of roles in both excitable and non-excitable cells and are further classified on the basis of their single channel conductance to form the small conductance (SK), intermediate conductance (IK) and big conductance (BK) K+ channels.In this chapter, we will focus on the mechanisms underlying the gating of BK channels, whose function is modified in different tissues by different splice variants as well as the expanding array of regulatory accessory subunits including β, γ and LINGO subunits. We will examine how BK channels are modified by these regulatory subunits and describe how the channel gating is altered by voltage and Ca2+ whilst setting this in context with the recently published structures of the BK channel. Finally, we will discuss how BK and other calcium-activated channels are modulated by novel ion channel modulators and describe some of the challenges associated with trying to develop compounds with sufficient efficacy, potency and selectivity to be of therapeutic benefit.
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20
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Hydrogen Sulfide Relaxes Human Uterine Artery via Activating Smooth Muscle BK Ca Channels. Antioxidants (Basel) 2020; 9:antiox9111127. [PMID: 33202933 PMCID: PMC7697977 DOI: 10.3390/antiox9111127] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 10/29/2020] [Accepted: 11/06/2020] [Indexed: 12/16/2022] Open
Abstract
Opening of large conductance calcium-activated and voltage-dependent potassium (BKCa) channels hyperpolarizes plasma membranes of smooth muscle (SM) to cause vasodilation, underling a key mechanism for mediating uterine artery (UA) dilation in pregnancy. Hydrogen sulfide (H2S) has been recently identified as a new UA vasodilator, yet the mechanism underlying H2S-induced UA dilation is unknown. Here, we tested whether H2S activated BKCa channels in human UA smooth muscle cells (hUASMC) to mediate UA relaxation. Multiple BKCa subunits were found in human UA in vitro and hUASMC in vitro, and high β1 and γ1 proteins were localized in SM cells in human UA. Baseline outward currents, recorded by whole-cell and single-channel patch clamps, were significantly inhibited by specific BKCa blockers iberiotoxin (IBTX) or tetraethylammonium, showing specific BKCa activity in hUASMC. H2S dose (NaHS, 1–1000 µM)-dependently potentiated BKCa currents and open probability. Co-incubation with a Ca2+ blocker nifedipine (5 µM) or a chelator (ethylene glycol-bis (β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA), 5 mM) did not alter H2S-potentiated BKCa currents and open probability. NaHS also dose-dependently relaxed phenylephrine pre-constricted freshly prepared human UA rings, which was inhibited by IBTX. Thus, H2S stimulated human UA relaxation at least partially via activating SM BKCa channels independent of extracellular Ca2+.
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21
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Catacuzzeno L, Sforna L, Esposito V, Limatola C, Franciolini F. Ion Channels in Glioma Malignancy. Rev Physiol Biochem Pharmacol 2020; 181:223-267. [DOI: 10.1007/112_2020_44] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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22
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Xu J, Ma HH, Liu ZM, Zheng W, Lai XY, Zhu H, Liu J, Zhou Y, Zhou XM. Expression and alternative splicing analysis of a large-conductance calcium-activated potassium channel gene in Plutella xylostella. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2020; 105:e21720. [PMID: 32557681 DOI: 10.1002/arch.21720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 05/20/2020] [Accepted: 05/21/2020] [Indexed: 06/11/2023]
Abstract
The large-conductance calcium-activated potassium channel (BKCa ) plays an important role in the regulation of insect neural circuits and locomotion, and thus is a potential target of insecticides. In this study, iberiotoxin, an inhibitor of BKCa , was found to prolong the anesthetic time of ethyl acetate on Plutella xylostella larvae. Therefore, the coding sequence of slowpoke gene coding the alpha subunit of BKCa was cloned to investigate the function of this channel in P. xylostella, and the gene expression profile in the developmental stages and tissues was also characterized. The total length of pxslo DNA was more than 19.9 kb, which harbored four alternative splicing sites (ASP-A, ASP-C, ASP-E, and ASP-G), and the coding sequence of pxslo with the highest frequency of splicing (GenBank ID: MN938456) was 3,405 base pair. The characterized PxSlo protein contained conserved domains previously identified in other insects. Quantitative reverse transcription-polymerase chain reaction analysis showed that pxslo was expressed in all the developmental stages of P. xylostella, with the highest level in adults. In the larval stage, pxslo was mainly expressed in the head and epidermis, while a limited protein was expressed in the midgut. In the adult stage, pxslo was highly expressed in the head, followed by in the ovarian tubule, and was not expressed in the testis or wings. These results suggest that BKCa plays an important physiological role in P. xylostella and provides useful information for the functional study and screening of BKCa inhibitors.
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Affiliation(s)
- Jie Xu
- College of Plant Protection, Graduate School of Hunan Agricultural University, Changsha, China
| | - Hai-Hao Ma
- Hunan Agricultural Biotechnology Research Institute, Hunan Academy of Agricultural Sciences, Changsha, China
| | - Zhe-Ming Liu
- Hunan Agricultural Biotechnology Research Institute, Hunan Academy of Agricultural Sciences, Changsha, China
| | - Wei Zheng
- Hunan Agricultural Biotechnology Research Institute, Hunan Academy of Agricultural Sciences, Changsha, China
| | - Xiao-Yi Lai
- Hunan Agricultural Biotechnology Research Institute, Hunan Academy of Agricultural Sciences, Changsha, China
| | - Hang Zhu
- Hunan Agricultural Biotechnology Research Institute, Hunan Academy of Agricultural Sciences, Changsha, China
| | - Jia Liu
- Hunan Agricultural Biotechnology Research Institute, Hunan Academy of Agricultural Sciences, Changsha, China
| | - Yong Zhou
- Hunan Agricultural Biotechnology Research Institute, Hunan Academy of Agricultural Sciences, Changsha, China
| | - Xiao-Mao Zhou
- College of Plant Protection, Graduate School of Hunan Agricultural University, Changsha, China
- Hunan Agricultural Biotechnology Research Institute, Hunan Academy of Agricultural Sciences, Changsha, China
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Szteyn K, Singh H. BK Ca Channels as Targets for Cardioprotection. Antioxidants (Basel) 2020; 9:antiox9080760. [PMID: 32824463 PMCID: PMC7463653 DOI: 10.3390/antiox9080760] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/09/2020] [Accepted: 08/13/2020] [Indexed: 12/16/2022] Open
Abstract
The large-conductance calcium- and voltage-activated K+ channel (BKCa) are encoded by the Kcnma1 gene. They are ubiquitously expressed in neuronal, smooth muscle, astrocytes, and neuroendocrine cells where they are known to play an important role in physiological and pathological processes. They are usually localized to the plasma membrane of the majority of the cells with an exception of adult cardiomyocytes, where BKCa is known to localize to mitochondria. BKCa channels couple calcium and voltage responses in the cell, which places them as unique targets for a rapid physiological response. The expression and activity of BKCa have been linked to several cardiovascular, muscular, and neurological defects, making them a key therapeutic target. Specifically in the heart muscle, pharmacological and genetic activation of BKCa channels protect the heart from ischemia-reperfusion injury and also facilitate cardioprotection rendered by ischemic preconditioning. The mechanism involved in cardioprotection is assigned to the modulation of mitochondrial functions, such as regulation of mitochondrial calcium, reactive oxygen species, and membrane potential. Here, we review the progress made on BKCa channels and cardioprotection and explore their potential roles as therapeutic targets for preventing acute myocardial infarction.
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Tarasenko O, Voytenko S, Koval L, Lykhmus O, Kalashnyk O, Skok M. Unusual properties of α7 nicotinic acetylcholine receptor ion channels in B lymphocyte-derived SP-2/0 cells. Int Immunopharmacol 2020; 82:106373. [PMID: 32163855 DOI: 10.1016/j.intimp.2020.106373] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 02/25/2020] [Accepted: 03/02/2020] [Indexed: 12/30/2022]
Abstract
This study demonstrates the presence of α7 nicotinic acetylcholine receptors (nAChR) in B lymphocyte-derived SP-2/0 cells by means of flow cytometry and immunocytochemistry. According to lectin and sandwich ELISA, the α7 subunits expressed in SP-2/0 cells are more glycosylated compared to those expressed in the brain or normal B lymphocytes and are combined with β2 subunits. At zero and negative pipette potentials, either acetylcholine or α7-specific agonist PNU282987 stimulated the ion channel activity in SP-2/0 cells revealed by single channel patch-clamp recordings. The conductivity was within the range of 19 to 39 pS and reversal potential was between -17 mV and +28 mV, the currents were potentiated by α7-specific positive allosteric modulator PNU120596 and were partially blocked by α7-specific antagonist methyllicaconitine (MLA). However, they were oriented downwards suggesting that the channels mediated the cation outflux rather than influx. As shown by Ca2+ imaging studies, PNU282987 did not stimulate immediate Ca2+ influx into SP-2/0 cells. Instead, Ca2+ influx through Ca-release-activated channels (CRACs) was observed within minutes after either PNU282987 or MLA application. It is concluded that SP-2/0 express α7β2 nAChRs, which mediate the cation outflux under negative pipette potentials applied, possibly, due to depolarized membrane or negative surface charge formed by carbohydrate residues. In addition, α7β2 nAChRs may influence CRACs in ion-independent way.
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Affiliation(s)
| | - Sergiy Voytenko
- Bogomoletz Institute of Physiology, 4, Bogomoletz Str, 01024 Kyiv, Ukraine
| | - Lyudmyla Koval
- Palladin Institute of Biochemistry, 9, Leontovycha Str., 01030 Kyiv, Ukraine.
| | - Olena Lykhmus
- Palladin Institute of Biochemistry, 9, Leontovycha Str., 01030 Kyiv, Ukraine
| | - Olena Kalashnyk
- Palladin Institute of Biochemistry, 9, Leontovycha Str., 01030 Kyiv, Ukraine
| | - Maryna Skok
- Palladin Institute of Biochemistry, 9, Leontovycha Str., 01030 Kyiv, Ukraine.
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25
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Selvaraj C, Selvaraj G, Kaliamurthi S, Cho WC, Wei DQ, Singh SK. Ion Channels as Therapeutic Targets for Type 1 Diabetes Mellitus. Curr Drug Targets 2020; 21:132-147. [PMID: 31538892 DOI: 10.2174/1389450119666190920152249] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 08/06/2019] [Accepted: 08/07/2019] [Indexed: 02/07/2023]
Abstract
Ion channels are integral proteins expressed in almost all living cells and are involved in muscle contraction and nutrient transport. They play a critical role in the normal functioning of the excitable tissues of the nervous system and regulate the action potential and contraction events. Dysfunction of genes encodes ion channel proteins, which disrupt the channel function and lead to a number of diseases, among which is type 1 diabetes mellitus (T1DM). Therefore, understanding the complex mechanism of ion channel receptors is necessary to facilitate the diagnosis and management of treatment. In this review, we summarize the mechanism of important ion channels and their potential role in the regulation of insulin secretion along with the limitations of ion channels as therapeutic targets. Furthermore, we discuss the recent investigations of the mechanism regulating the ion channels in pancreatic beta cells, which suggest that ion channels are active participants in the regulation of insulin secretion.
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Affiliation(s)
- Chandrabose Selvaraj
- Department of Bioinformatics, Computer-Aided Drug Design, and Molecular Modeling Lab, Science Block, Alagappa University, Karaikudi, Tamil Nadu, 630004, India
| | - Gurudeeban Selvaraj
- Center of Interdisciplinary Sciences-Computational Life Sciences, College of Food Science and Engineering, Henan University of Technology, Zhengzhou, 450001, China
- Peng Cheng Laboratory, Vanke Cloud City Phase I Building 8, Xili Street, Nanshan District, Shenzhen, Guangdong, 518055, China
| | - Satyavani Kaliamurthi
- Center of Interdisciplinary Sciences-Computational Life Sciences, College of Food Science and Engineering, Henan University of Technology, Zhengzhou, 450001, China
- Peng Cheng Laboratory, Vanke Cloud City Phase I Building 8, Xili Street, Nanshan District, Shenzhen, Guangdong, 518055, China
| | - William C Cho
- Department of Clinical Oncology, Queen Elizabeth Hospital, Kowloon, Hong Kong
| | - Dong-Qing Wei
- Center of Interdisciplinary Sciences-Computational Life Sciences, College of Food Science and Engineering, Henan University of Technology, Zhengzhou, 450001, China
- Peng Cheng Laboratory, Vanke Cloud City Phase I Building 8, Xili Street, Nanshan District, Shenzhen, Guangdong, 518055, China
- Department of Bioinformatics, The State Key Laboratory of Microbial Metabolism, College of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Sanjeev Kumar Singh
- Department of Bioinformatics, Computer-Aided Drug Design, and Molecular Modeling Lab, Science Block, Alagappa University, Karaikudi, Tamil Nadu, 630004, India
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26
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Moldenhauer HJ, Matychak KK, Meredith AL. Comparative gain-of-function effects of the KCNMA1-N999S mutation on human BK channel properties. J Neurophysiol 2019; 123:560-570. [PMID: 31851553 PMCID: PMC7052641 DOI: 10.1152/jn.00626.2019] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
KCNMA1, encoding the voltage- and calcium-activated potassium channel, has a pivotal role in brain physiology. Mutations in KCNMA1 are associated with epilepsy and/or dyskinesia (PNKD3). Two KCNMA1 mutations correlated with these phenotypes, D434G and N999S, were previously identified as producing gain-of-function (GOF) effects on BK channel activity. Three new patients have been reported harboring N999S, one carrying a second mutation, R1128W, but the effects of these mutations have not yet been reported under physiological K+ conditions or compared to D434G. In this study, we characterize N999S, the novel N999S/R1128W double mutation, and D434G in a brain BK channel splice variant, comparing the effects on BK current properties under a physiological K+ gradient with action potential voltage commands. N999S, N999S/R1128W, and D434G cDNAs were expressed in HEK293T cells and characterized by patch-clamp electrophysiology. N999S BK currents were shifted to negative potentials, with faster activation and slower deactivation compared with wild type (WT) and D434G. The double mutation N999S/R1128W did not show any additional changes in current properties compared with N999S alone. The antiepileptic drug acetazolamide was assessed for its ability to directly modulate WT and N999S channels. Neither the WT nor N999S channels were sensitive to the antiepileptic drug acetazolamide, but both were sensitive to the inhibitor paxilline. We conclude that N999S is a strong GOF mutation that surpasses the D434G phenotype, without mitigation by R1128W. Acetazolamide has no direct modulatory action on either WT or N999S channels, indicating that its use may not be contraindicated in patients harboring GOF KCNMA1 mutations.NEW & NOTEWORTHY KCNMA1-linked channelopathy is a new neurological disorder characterized by mutations in the BK voltage- and calcium-activated potassium channel. The epilepsy- and dyskinesia-associated gain-of-function mutations N999S and D434G comprise the largest number of patients in the cohort. This study provides the first direct comparison between D434G and N999S BK channel properties as well as a novel double mutation, N999S/R1128W, from another patient, defining the functional effects during an action potential stimulus.
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Affiliation(s)
- Hans J Moldenhauer
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Katia K Matychak
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland.,Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland
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27
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Plante AE, Lai MH, Lu J, Meredith AL. Effects of Single Nucleotide Polymorphisms in Human KCNMA1 on BK Current Properties. Front Mol Neurosci 2019; 12:285. [PMID: 31849601 PMCID: PMC6901604 DOI: 10.3389/fnmol.2019.00285] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 11/12/2019] [Indexed: 12/14/2022] Open
Abstract
BK Ca2+-activated K+ channels are important regulators of membrane excitability. Multiple regulatory mechanisms tailor BK current properties across tissues, such as alternative splicing, posttranslational modifications, and auxiliary subunits. Another potential mechanism for modulating BK channel activity is genetic variation due to single nucleotide polymorphisms (SNPs). The gene encoding the human BK α subunit, KCNMA1, contains hundreds of SNPs. However, the variation in BK channel activity due to SNPs is not well studied. Here, we screened the effects of four SNPs (A138V, C495G, N599D, and R800W) on BK currents in HEK293T cells, selected based on predicted protein pathogenicity or disease linkage. We found that the SNPs C495G and R800W had the largest effects on BK currents, affecting the conductance–voltage relationship across multiple Ca2+ conditions in the context of two BK channel splice variants. In symmetrical K+, C495G shifted the V1/2 to more hyperpolarized potentials (by −15 to −20 mV) and accelerated activation, indicating C495G confers some gain-of-function properties. R800W shifted the V1/2 to more depolarized potentials (+15 to +35 mV) and slowed activation, conferring loss-of-function properties. Moreover, the C495G and R800W effects on current properties were found to persist with posttranslational modifications. In contrast, A138V and N599D had smaller and more variable effects on current properties. Neither application of alkaline phosphatase to patches, which results in increased BK channel activity attributed to channel dephosphorylation, nor bidirectional redox modulations completely abrogated SNP effects on BK currents. Lastly, in physiological K+, C495G increased the amplitude of action potential (AP)-evoked BK currents, while R800W had a more limited effect. However, the introduction of R800W in parallel with the epilepsy-linked mutation D434G (D434G/R800W) decreased the amplitude of AP-evoked BK currents compared with D434G alone. These results suggest that in a physiological context, C495G could increase BK activation, while the effects of the loss-of-function SNP R800W could oppose the gain-of-function effects of an epilepsy-linked mutation. Together, these results implicate naturally occurring human genetic variation as a potential modifier of BK channel activity across a variety of conditions.
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Affiliation(s)
- Amber E Plante
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Michael H Lai
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Jessica Lu
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
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28
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Bailey CS, Moldenhauer HJ, Park SM, Keros S, Meredith AL. KCNMA1-linked channelopathy. J Gen Physiol 2019; 151:1173-1189. [PMID: 31427379 PMCID: PMC6785733 DOI: 10.1085/jgp.201912457] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 08/13/2019] [Indexed: 12/20/2022] Open
Abstract
Bailey et al. review a new neurological channelopathy associated with KCNMA1, encoding the BK voltage- and Ca2+-activated K+ channel. KCNMA1 encodes the pore-forming α subunit of the “Big K+” (BK) large conductance calcium and voltage-activated K+ channel. BK channels are widely distributed across tissues, including both excitable and nonexcitable cells. Expression levels are highest in brain and muscle, where BK channels are critical regulators of neuronal excitability and muscle contractility. A global deletion in mouse (KCNMA1−/−) is viable but exhibits pathophysiology in many organ systems. Yet despite the important roles in animal models, the consequences of dysfunctional BK channels in humans are not well characterized. Here, we summarize 16 rare KCNMA1 mutations identified in 37 patients dating back to 2005, with an array of clinically defined pathological phenotypes collectively referred to as “KCNMA1-linked channelopathy.” These mutations encompass gain-of-function (GOF) and loss-of-function (LOF) alterations in BK channel activity, as well as several variants of unknown significance (VUS). Human KCNMA1 mutations are primarily associated with neurological conditions, including seizures, movement disorders, developmental delay, and intellectual disability. Due to the recent identification of additional patients, the spectrum of symptoms associated with KCNMA1 mutations has expanded but remains primarily defined by brain and muscle dysfunction. Emerging evidence suggests the functional BK channel alterations produced by different KCNMA1 alleles may associate with semi-distinct patient symptoms, such as paroxysmal nonkinesigenic dyskinesia (PNKD) with GOF and ataxia with LOF. However, due to the de novo origins for the majority of KCNMA1 mutations identified to date and the phenotypic variability exhibited by patients, additional evidence is required to establish causality in most cases. The symptomatic picture developing from patients with KCNMA1-linked channelopathy highlights the importance of better understanding the roles BK channels play in regulating cell excitability. Establishing causality between KCNMA1-linked BK channel dysfunction and specific patient symptoms may reveal new treatment approaches with the potential to increase therapeutic efficacy over current standard regimens.
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Affiliation(s)
- Cole S Bailey
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Hans J Moldenhauer
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Su Mi Park
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Sotirios Keros
- Department of Pediatrics, University of South Dakota Sanford School of Medicine, Sioux Falls, SD
| | - Andrea L Meredith
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD
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29
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Bukiya AN, Dopico AM. Regulation of BK Channel Activity by Cholesterol and Its Derivatives. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1115:53-75. [DOI: 10.1007/978-3-030-04278-3_3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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30
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Miranda P, Holmgren M, Giraldez T. Voltage-dependent dynamics of the BK channel cytosolic gating ring are coupled to the membrane-embedded voltage sensor. eLife 2018; 7:40664. [PMID: 30526860 PMCID: PMC6301790 DOI: 10.7554/elife.40664] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 12/11/2018] [Indexed: 12/21/2022] Open
Abstract
In humans, large conductance voltage- and calcium-dependent potassium (BK) channels are regulated allosterically by transmembrane voltage and intracellular Ca2+. Divalent cation binding sites reside within the gating ring formed by two Regulator of Conductance of Potassium (RCK) domains per subunit. Using patch-clamp fluorometry, we show that Ca2+ binding to the RCK1 domain triggers gating ring rearrangements that depend on transmembrane voltage. Because the gating ring is outside the electric field, this voltage sensitivity must originate from coupling to the voltage-dependent channel opening, the voltage sensor or both. Here we demonstrate that alterations of the voltage sensor, either by mutagenesis or regulation by auxiliary subunits, are paralleled by changes in the voltage dependence of the gating ring movements, whereas modifications of the relative open probability are not. These results strongly suggest that conformational changes of RCK1 domains are specifically coupled to the voltage sensor function during allosteric modulation of BK channels.
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Affiliation(s)
- Pablo Miranda
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Miguel Holmgren
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Teresa Giraldez
- Departamento de Ciencias Medicas Basicas, Universidad de La Laguna, San Cristóbal de La Laguna, Spain.,Instituto de Tecnologias Biomedicas, Universidad de La Laguna, San Cristóbal de La Laguna, Spain
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31
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Bollinger WL, Sial N, Dawson-Scully K. BK channels and a cGMP-dependent protein kinase (PKG) function through independent mechanisms to regulate the tolerance of synaptic transmission to acute oxidative stress at the Drosophila larval neuromuscular junction. J Neurogenet 2018; 32:246-255. [DOI: 10.1080/01677063.2018.1500571] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Wesley L. Bollinger
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, FL, USA
| | - Nadia Sial
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, FL, USA
- Brain Institute Research Scholars Program, Florida Atlantic University, Boca Raton, FL, USA
| | - Ken Dawson-Scully
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, FL, USA
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32
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Abstract
Voltage-gated calcium (CaV) channels are associated with β and α2δ auxiliary subunits. This review will concentrate on the function of the α2δ protein family, which has four members. The canonical role for α2δ subunits is to convey a variety of properties on the CaV1 and CaV2 channels, increasing the density of these channels in the plasma membrane and also enhancing their function. More recently, a diverse spectrum of non-canonical interactions for α2δ proteins has been proposed, some of which involve competition with calcium channels for α2δ or increase α2δ trafficking and others which mediate roles completely unrelated to their calcium channel function. The novel roles for α2δ proteins which will be discussed here include association with low-density lipoprotein receptor-related protein 1 (LRP1), thrombospondins, α-neurexins, prion proteins, large conductance (big) potassium (BK) channels, and N-methyl-d-aspartate (NMDA) receptors.
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Affiliation(s)
- Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
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33
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Rajendran VM, Sandle GI. Colonic Potassium Absorption and Secretion in Health and Disease. Compr Physiol 2018; 8:1513-1536. [PMID: 30215859 PMCID: PMC9769410 DOI: 10.1002/cphy.c170030] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The colon has large capacities for K+ absorption and K+ secretion, but its role in maintaining K+ homeostasis is often overlooked. For many years, passive diffusion and/or solvent drag were thought to be the primary mechanisms for K+ absorption in human and animal colon. However, it is now clear that apical H+ ,K+ -ATPase, in coordination with basolateral K+ -Cl- cotransport and/or K+ and Cl- channels operating in parallel, mediate electroneutral K+ absorption in animal colon. We now know that K+ absorption in rat colon reflects ouabain-sensitive and ouabain-insensitive apical H+ ,K+ -ATPase activities. Ouabain-insensitive and ouabain-sensitive H+ ,K+ -ATPases are localized in surface and crypt cells, respectively. Colonic H+ ,K+ -ATPase consists of α- (HKCα ) and β- (HKCβ ) subunits which, when coexpressed, exhibit ouabain-insensitive H+ ,K+ -ATPase activity in HEK293 cells, while HKCα coexpressed with the gastric β-subunit exhibits ouabain-sensitive H+ ,K+ -ATPase activity in Xenopus oocytes. Aldosterone enhances apical H+ ,K+ -ATPase activity, HKCα specific mRNA and protein expression, and K+ absorption. Active K+ secretion, on the other hand, is mediated by apical K+ channels operating in a coordinated way with the basolateral Na+ -K+ -2Cl- cotransporter. Both Ca2+ -activated intermediate conductance K+ (IK) and large conductance K+ (BK) channels are located in the apical membrane of colonic epithelia. IK channel-mediated K+ efflux provides the driving force for Cl- secretion, while BK channels mediate active (e.g., cAMP-activated) K+ secretion. BK channel expression and activity are increased in patients with end-stage renal disease and ulcerative colitis. This review summarizes the role of apical H+ ,K+ -ATPase in K+ absorption, and apical BK channel function in K+ secretion in health and disease. © 2018 American Physiological Society. Compr Physiol 8:1513-1536, 2018.
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Affiliation(s)
| | - Geoffrey I. Sandle
- Leeds Institute of Biomedical and Clinical Sciences, St James’s University Hospital, Leeds LS9 7TF, UK
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34
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Zhuang Z, Xiao J, Chen X, Hu X, Li R, Chen S, Feng X, Shen S, Ma HP, Zhuang J, Cai H. G protein pathway suppressor 2 enhanced the renal large-conductance Ca 2+-activated potassium channel expression via inhibiting ERK1/2 signaling pathway. Am J Physiol Renal Physiol 2018; 315:F503-F511. [PMID: 29767559 DOI: 10.1152/ajprenal.00041.2018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
G protein pathway suppressor 2 (GPS2) is a multifunctional protein and transcriptional regulation factor that is involved in the G protein MAPK signaling pathway. It has been shown that the MAPK signaling pathway plays an important role in the regulation of renal large-conductance Ca2+-activated potassium (BK) channels. In this study, we investigated the effects of GPS2 on BK channel activity and protein expression. In human embryonic kidney (HEK) BK stably expressing cells transfected with either GPS2 or its vector control, a single-cell recording showed that GPS2 significantly increased BK channel activity ( NPo), increasing BK open probability ( Po), and channel number ( N) compared with the control. In Cos-7 cells and HEK 293 T cells, GPS2 overexpression significantly enhanced the total protein expression of BK in a dose-dependent manner. Knockdown of GPS2 expression significantly decreased BK protein expression, while increasing ERK1/2 phosphorylation. Knockdown of ERK1/2 expression reversed the GPS2 siRNA-mediated inhibition of BK protein expression in Cos-7 cells. Pretreatments of Cos-7 cells with either the lysosomal inhibitor bafilomycin A1 or the proteasomal inhibitor MG132 partially reversed the inhibitory effects of GPS2 siRNA on BK protein expression. In addition, feeding a high-potassium diet significantly increased both GPS2 and BK protein abundance in mice. These data suggest that GPS2 enhances BK channel activity and its protein expression by reducing ERK1/2 signaling-mediated degradation of the channel.
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Affiliation(s)
- Zhizhi Zhuang
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China.,Renal Division, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia
| | - Jia Xiao
- Renal Division, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Xiangya Hospital, Central South University, Hunan, China
| | - Xinxin Chen
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China.,Renal Division, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia
| | - Xiaohan Hu
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China
| | - Ruidian Li
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China
| | - Shan Chen
- Renal Division, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia
| | - Xiuyan Feng
- Renal Division, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Xiangya Hospital, Central South University, Hunan, China
| | - Saier Shen
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China
| | - He-Ping Ma
- Department of Physiology, Emory University School of Medicine , Atlanta, Georgia
| | - Jieqiu Zhuang
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China
| | - Hui Cai
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China.,Renal Division, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Section of Nephrology, Atlanta Veterans Administration Medical Center, Decatur, Georgia
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35
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Zhu Y, Ye P, Chen SL, Zhang DM. Functional regulation of large conductance Ca 2+-activated K + channels in vascular diseases. Metabolism 2018; 83:75-80. [PMID: 29373813 DOI: 10.1016/j.metabol.2018.01.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Revised: 01/03/2018] [Accepted: 01/18/2018] [Indexed: 12/17/2022]
Abstract
The large conductance Ca2+-activated potassium channels, the BK channels, is widely expressed in various tissues and activated in a Ca2+- and voltage-dependent manner. The activation of BK channels hyperpolarizes vascular smooth muscle cell membrane potential, resulting in vasodilation. Under pathophysiological conditions, such as diabetes mellitus and hypertension, impaired BK channel function exacerbates vascular vasodilation and leads to organ ischemia. The vascular BK channel is composed of 4 pore-forming subunits, BK-α together with 4 auxiliary subunits: β1 subunits (BK-β1) or γ1 subunits (BK-γ1). Recent studies have shown that down-regulation of the BK β1 subunit in diabetes mellitus induced vascular dysfunction; however, the molecular mechanism of these vascular diseases is not well understood. In this review, we summarize the potential mechanisms regarding BK channelopathy and the potential therapeutic targets of BK channels for vascular diseases.
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Affiliation(s)
- Yanrong Zhu
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China
| | - Peng Ye
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China
| | - Shao-Liang Chen
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China
| | - Dai-Min Zhang
- Department of Cardiology, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu 210006, China.
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36
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Dopico AM, Bukiya AN, Jaggar JH. Calcium- and voltage-gated BK channels in vascular smooth muscle. Pflugers Arch 2018; 470:1271-1289. [PMID: 29748711 DOI: 10.1007/s00424-018-2151-y] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 04/27/2018] [Indexed: 02/04/2023]
Abstract
Ion channels in vascular smooth muscle regulate myogenic tone and vessel contractility. In particular, activation of calcium- and voltage-gated potassium channels of large conductance (BK channels) results in outward current that shifts the membrane potential toward more negative values, triggering a negative feed-back loop on depolarization-induced calcium influx and SM contraction. In this short review, we first present the molecular basis of vascular smooth muscle BK channels and the role of subunit composition and trafficking in the regulation of myogenic tone and vascular contractility. BK channel modulation by endogenous signaling molecules, and paracrine and endocrine mediators follows. Lastly, we describe the functional changes in smooth muscle BK channels that contribute to, or are triggered by, common physiological conditions and pathologies, including obesity, diabetes, and systemic hypertension.
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Affiliation(s)
- Alex M Dopico
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, 71 South Manassas St., Memphis, TN, 38163, USA.
| | - Anna N Bukiya
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, 71 South Manassas St., Memphis, TN, 38163, USA
| | - Jonathan H Jaggar
- Department of Physiology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, USA
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37
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Zhang FX, Gadotti VM, Souza IA, Chen L, Zamponi GW. BK Potassium Channels Suppress Cavα2δ Subunit Function to Reduce Inflammatory and Neuropathic Pain. Cell Rep 2018; 22:1956-1964. [DOI: 10.1016/j.celrep.2018.01.073] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 10/25/2017] [Accepted: 01/24/2018] [Indexed: 01/10/2023] Open
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38
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Molecular determinants of Ca 2+ sensitivity at the intersubunit interface of the BK channel gating ring. Sci Rep 2018; 8:509. [PMID: 29323236 PMCID: PMC5765161 DOI: 10.1038/s41598-017-19029-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 12/19/2017] [Indexed: 12/31/2022] Open
Abstract
The large-conductance calcium-activated K+ (BK) channel contains two intracellular tandem Ca2+-sensing RCK domains (RCK1 and RCK2), which tetramerize into a Ca2+ gating ring that regulates channel opening by conformational expansion in response to Ca2+ binding. Interestingly, the gating ring’s intersubunit assembly interface harbors the RCK2 Ca2+-binding site, known as the Ca2+ bowl. The gating ring’s assembly interface is made in part by intersubunit coordination of a Ca2+ ion between the Ca2+ bowl and an RCK1 Asn residue, N449, and by apparent intersubunit electrostatic interactions between E955 in RCK2 and R786 and R790 in the RCK2 of the adjacent subunit. To understand the role of the intersubunit assembly interface in Ca2+ gating, we performed mutational analyses of these putative interacting residues in human BK channels. We found that N449, despite its role in Ca2+ coordination, does not set the channel’s Ca2+ sensitivity, whereas E955 is a determinant of Ca2+ sensitivity, likely through intersubunit electrostatic interactions. Our findings provide evidence that the intersubunit assembly interface contains molecular determinants of Ca2+-sensitivity in BK channels.
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39
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Zhou Y, Yang H, Cui J, Lingle CJ. Threading the biophysics of mammalian Slo1 channels onto structures of an invertebrate Slo1 channel. J Gen Physiol 2017; 149:985-1007. [PMID: 29025867 PMCID: PMC5677106 DOI: 10.1085/jgp.201711845] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 09/20/2017] [Indexed: 11/24/2022] Open
Abstract
Zhou et al. consider the biophysics of large-conductance Ca2+-activated Slo1 channels in the context of Aplysia Slo1 structures. For those interested in the machinery of ion channel gating, the Ca2+ and voltage-activated BK K+ channel provides a compelling topic for investigation, by virtue of its dual allosteric regulation by both voltage and intracellular Ca2+ and because its large-single channel conductance facilitates detailed kinetic analysis. Over the years, biophysical analyses have illuminated details of the allosteric regulation of BK channels and revealed insights into the mechanism of BK gating, e.g., inner cavity size and accessibility and voltage sensor-pore coupling. Now the publication of two structures of an Aplysia californica BK channel—one liganded and one metal free—promises to reinvigorate functional studies and interpretation of biophysical results. The new structures confirm some of the previous functional inferences but also suggest new perspectives regarding cooperativity between Ca2+-binding sites and the relationship between voltage- and Ca2+-dependent gating. Here we consider the extent to which the two structures explain previous functional data on pore-domain properties, voltage-sensor motions, and divalent cation binding and activation of the channel.
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Affiliation(s)
- Yu Zhou
- Department of Anesthesiology, Washington University School of Medicine, St. Louis MO
| | - Huanghe Yang
- Department of Biochemistry, Duke University School of Medicine, Durham, NC
| | - Jianmin Cui
- Department of Biomedical Engineering, Washington University, St. Louis, MO
| | - Christopher J Lingle
- Department of Anesthesiology, Washington University School of Medicine, St. Louis MO
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40
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Tykocki NR, Boerman EM, Jackson WF. Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles. Compr Physiol 2017; 7:485-581. [PMID: 28333380 DOI: 10.1002/cphy.c160011] [Citation(s) in RCA: 222] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body's tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. © 2017 American Physiological Society. Compr Physiol 7:485-581, 2017.
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Affiliation(s)
- Nathan R Tykocki
- Department of Pharmacology, University of Vermont, Burlington, Vermont, USA
| | - Erika M Boerman
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, USA
| | - William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA
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41
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Zhang G, Geng Y, Jin Y, Shi J, McFarland K, Magleby KL, Salkoff L, Cui J. Deletion of cytosolic gating ring decreases gate and voltage sensor coupling in BK channels. J Gen Physiol 2017; 149:373-387. [PMID: 28196879 PMCID: PMC5339509 DOI: 10.1085/jgp.201611646] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Revised: 10/28/2016] [Accepted: 12/28/2016] [Indexed: 12/26/2022] Open
Abstract
Both cellular depolarization and intracellular Ca2+ can gate open large conductance Ca2+-activated K+ channels. Zhang et al. show that the intracellular gating ring, which forms the Ca2+-sensing machinery of the channel, is also required for activated voltage sensors to effectively gate open the pore. Large conductance Ca2+-activated K+ channels (BK channels) gate open in response to both membrane voltage and intracellular Ca2+. The channel is formed by a central pore-gate domain (PGD), which spans the membrane, plus transmembrane voltage sensors and a cytoplasmic gating ring that acts as a Ca2+ sensor. How these voltage and Ca2+ sensors influence the common activation gate, and interact with each other, is unclear. A previous study showed that a BK channel core lacking the entire cytoplasmic gating ring (Core-MT) was devoid of Ca2+ activation but retained voltage sensitivity (Budelli et al. 2013. Proc. Natl. Acad. Sci. USA. http://dx.doi.org/10.1073/pnas.1313433110). In this study, we measure voltage sensor activation and pore opening in this Core-MT channel over a wide range of voltages. We record gating currents and find that voltage sensor activation in this truncated channel is similar to WT but that the coupling between voltage sensor activation and gating of the pore is reduced. These results suggest that the gating ring, in addition to being the Ca2+ sensor, enhances the effective coupling between voltage sensors and the PGD. We also find that removal of the gating ring alters modulation of the channels by the BK channel’s β1 and β2 subunits.
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Affiliation(s)
- Guohui Zhang
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO 63130
| | - Yanyan Geng
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Yakang Jin
- Department of Pharmacology, Soochow University College of Pharmaceutical Sciences, Suzhou 215123, China
| | - Jingyi Shi
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO 63130
| | - Kelli McFarland
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO 63130
| | - Karl L Magleby
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Lawrence Salkoff
- Department of Anatomy and Neurobiology (Department of Neuroscience), Washington University School of Medicine in St. Louis, St. Louis, MO 63110.,Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110
| | - Jianmin Cui
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO 63130 .,Department of Pharmacology, Soochow University College of Pharmaceutical Sciences, Suzhou 215123, China
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42
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Kaczmarek LK, Aldrich RW, Chandy KG, Grissmer S, Wei AD, Wulff H. International Union of Basic and Clinical Pharmacology. C. Nomenclature and Properties of Calcium-Activated and Sodium-Activated Potassium Channels. Pharmacol Rev 2017; 69:1-11. [PMID: 28267675 PMCID: PMC11060434 DOI: 10.1124/pr.116.012864] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024] Open
Abstract
A subset of potassium channels is regulated primarily by changes in the cytoplasmic concentration of ions, including calcium, sodium, chloride, and protons. The eight members of this subfamily were originally all designated as calcium-activated channels. More recent studies have clarified the gating mechanisms for these channels and have documented that not all members are sensitive to calcium. This article describes the molecular relationships between these channels and provides an introduction to their functional properties. It also introduces a new nomenclature that differentiates between calcium- and sodium-activated potassium channels.
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Affiliation(s)
- Leonard K Kaczmarek
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Richard W Aldrich
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - K George Chandy
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Stephan Grissmer
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Aguan D Wei
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Heike Wulff
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
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43
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Interactions of divalent cations with calcium binding sites of BK channels reveal independent motions within the gating ring. Proc Natl Acad Sci U S A 2016; 113:14055-14060. [PMID: 27872281 DOI: 10.1073/pnas.1611415113] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Large-conductance voltage- and calcium-activated K+ (BK) channels are key physiological players in muscle, nerve, and endocrine function by integrating intracellular Ca2+ and membrane voltage signals. The open probability of BK channels is regulated by the intracellular concentration of divalent cations sensed by a large structure in the BK channel called the "gating ring," which is formed by four tandems of regulator of conductance for K+ (RCK1 and RCK2) domains. In contrast to Ca2+ that binds to both RCK domains, Mg2+, Cd2+, or Ba2+ interact preferentially with either one or the other. Interaction of cations with their binding sites causes molecular rearrangements of the gating ring, but how these motions occur remains elusive. We have assessed the separate contributions of each RCK domain to the cation-induced gating-ring structural rearrangements, using patch-clamp fluorometry. Here we show that Mg2+ and Ba2+ selectively induce structural movement of the RCK2 domain, whereas Cd2+ causes motions of RCK1, in all cases substantially smaller than those elicited by Ca2+ By combining divalent species interacting with unique sites, we demonstrate that RCK1 and RCK2 domains move independently when their specific binding sites are occupied. Moreover, binding of chemically distinct cations to both RCK domains is additive, emulating the effect of fully occupied Ca2+ binding sites.
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Giacoppo JDOS, Carregal JB, Junior MC, Cunha EFFD, Ramalho TC. Towards the understanding of tetrahydroquinolines action in Aedes aegypti: larvicide or adulticide? MOLECULAR SIMULATION 2016. [DOI: 10.1080/08927022.2016.1239823] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
| | - Juliano B. Carregal
- Department of Chemistry, Federal University of São João del Rey, Divinópolis, Brazil
| | - Moacyr C. Junior
- Department of Chemistry, Federal University of São João del Rey, Divinópolis, Brazil
| | | | - Teodorico C. Ramalho
- Department of Chemistry, Federal University of Lavras, Lavras, Brazil
- Center for Basic and Applied Research, University Hradec Kralove, Hradec Kralove, Czech Republic
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Zhang J, Li M, Zhang Z, Zhu R, Olcese R, Stefani E, Toro L. The mitochondrial BK Ca channel cardiac interactome reveals BK Ca association with the mitochondrial import receptor subunit Tom22, and the adenine nucleotide translocator. Mitochondrion 2016; 33:84-101. [PMID: 27592226 DOI: 10.1016/j.mito.2016.08.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 08/29/2016] [Accepted: 08/30/2016] [Indexed: 10/21/2022]
Abstract
Mitochondrial BKCa channel, mitoBKCa, regulates mitochondria function in the heart but information on its protein partnerships in cardiac mitochondria is missing. A directed proteomic approach discovered the novel interaction of BKCa with Tom22, a component of the mitochondrion outer membrane import system, and the adenine nucleotide translocator (ANT). The expressed protein partners co-immunoprecipitated and co-segregated into mitochondrial fractions in HEK293T cells. The BKCa 50 amino acid splice insert, DEC, facilitated BKCa interaction with ANT. Further, BKCa transmembrane domain was required for the association with both Tom22 and ANT. The results serve as a working framework to understand mitoBKCa import and functional relationships.
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Affiliation(s)
- Jin Zhang
- Department of Anesthesiology, Division of Molecular Medicine, University of California, Los Angeles, Los Angeles, CA, USA; Department of Molecular & Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Min Li
- Department of Anesthesiology, Division of Molecular Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Zhu Zhang
- Department of Anesthesiology, Division of Molecular Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Ronghui Zhu
- Department of Anesthesiology, Division of Molecular Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Riccardo Olcese
- Department of Anesthesiology, Division of Molecular Medicine, University of California, Los Angeles, Los Angeles, CA, USA; Department of Physiology, University of California, Los Angeles, Los Angeles, CA, USA; Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, USA; Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, CA, USA
| | - Enrico Stefani
- Department of Anesthesiology, Division of Molecular Medicine, University of California, Los Angeles, Los Angeles, CA, USA; Department of Physiology, University of California, Los Angeles, Los Angeles, CA, USA; Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, USA; Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, CA, USA
| | - Ligia Toro
- Department of Anesthesiology, Division of Molecular Medicine, University of California, Los Angeles, Los Angeles, CA, USA; Department of Molecular & Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA; Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, USA; Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, CA, USA.
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46
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Potassium Channels in Regulation of Vascular Smooth Muscle Contraction and Growth. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2016; 78:89-144. [PMID: 28212804 DOI: 10.1016/bs.apha.2016.07.001] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Potassium channels importantly contribute to the regulation of vascular smooth muscle (VSM) contraction and growth. They are the dominant ion conductance of the VSM cell membrane and importantly determine and regulate membrane potential. Membrane potential, in turn, regulates the open-state probability of voltage-gated Ca2+ channels (VGCC), Ca2+ influx through VGCC, intracellular Ca2+, and VSM contraction. Membrane potential also affects release of Ca2+ from internal stores and the Ca2+ sensitivity of the contractile machinery such that K+ channels participate in all aspects of regulation of VSM contraction. Potassium channels also regulate proliferation of VSM cells through membrane potential-dependent and membrane potential-independent mechanisms. VSM cells express multiple isoforms of at least five classes of K+ channels that contribute to the regulation of contraction and cell proliferation (growth). This review will examine the structure, expression, and function of large conductance, Ca2+-activated K+ (BKCa) channels, intermediate-conductance Ca2+-activated K+ (KCa3.1) channels, multiple isoforms of voltage-gated K+ (KV) channels, ATP-sensitive K+ (KATP) channels, and inward-rectifier K+ (KIR) channels in both contractile and proliferating VSM cells.
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47
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Abstract
Ion channels regulate ion flow by opening and closing their pore gates. K(+) channels commonly possess two pore gates, one at the intracellular end for fast channel activation/deactivation and the other at the selectivity filter for slow C-type inactivation/recovery. The large-conductance calcium-activated potassium (BK) channel lacks a classic intracellular bundle-crossing activation gate and normally show no C-type inactivation. We hypothesized that the BK channel's activation gate may spatially overlap or coexist with the C-type inactivation gate at or near the selectivity filter. We induced C-type inactivation in BK channels and studied the relationship between activation/deactivation and C-type inactivation/recovery. We observed prominent slow C-type inactivation/recovery in BK channels by an extreme low concentration of extracellular K(+) together with a Y294E/K/Q/S or Y279F mutation whose equivalent in Shaker channels (T449E/K/D/Q/S or W434F) caused a greatly accelerated rate of C-type inactivation or constitutive C-inactivation. C-type inactivation in most K(+) channels occurs upon sustained membrane depolarization or channel opening and then recovers during hyperpolarized membrane potentials or channel closure. However, we found that the BK channel C-type inactivation occurred during hyperpolarized membrane potentials or with decreased intracellular calcium ([Ca(2+)]i) and recovered with depolarized membrane potentials or elevated [Ca(2+)]i Constitutively open mutation prevented BK channels from C-type inactivation. We concluded that BK channel C-type inactivation is closed state-dependent and that its extents and rates inversely correlate with channel-open probability. Because C-type inactivation can involve multiple conformational changes at the selectivity filter, we propose that the BK channel's normal closing may represent an early conformational stage of C-type inactivation.
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48
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β1-subunit-induced structural rearrangements of the Ca2+- and voltage-activated K+ (BK) channel. Proc Natl Acad Sci U S A 2016; 113:E3231-9. [PMID: 27217576 DOI: 10.1073/pnas.1606381113] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Large-conductance Ca(2+)- and voltage-activated K(+) (BK) channels are involved in a large variety of physiological processes. Regulatory β-subunits are one of the mechanisms responsible for creating BK channel diversity fundamental to the adequate function of many tissues. However, little is known about the structure of its voltage sensor domain. Here, we present the external architectural details of BK channels using lanthanide-based resonance energy transfer (LRET). We used a genetically encoded lanthanide-binding tag (LBT) to bind terbium as a LRET donor and a fluorophore-labeled iberiotoxin as the LRET acceptor for measurements of distances within the BK channel structure in a living cell. By introducing LBTs in the extracellular region of the α- or β1-subunit, we determined (i) a basic extracellular map of the BK channel, (ii) β1-subunit-induced rearrangements of the voltage sensor in α-subunits, and (iii) the relative position of the β1-subunit within the α/β1-subunit complex.
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49
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Abstract
BK channels are universal regulators of cell excitability, given their exceptional unitary conductance selective for K(+), joint activation mechanism by membrane depolarization and intracellular [Ca(2+)] elevation, and broad expression pattern. In this chapter, we discuss the structural basis and operational principles of their activation, or gating, by membrane potential and calcium. We also discuss how the two activation mechanisms interact to culminate in channel opening. As members of the voltage-gated potassium channel superfamily, BK channels are discussed in the context of archetypal family members, in terms of similarities that help us understand their function, but also seminal structural and biophysical differences that confer unique functional properties.
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Affiliation(s)
- A Pantazis
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, United States
| | - R Olcese
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, United States.
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50
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Shipston MJ, Tian L. Posttranscriptional and Posttranslational Regulation of BK Channels. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 128:91-126. [PMID: 27238262 DOI: 10.1016/bs.irn.2016.02.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Large conductance calcium- and voltage-activated potassium (BK) channels are ubiquitously expressed and play an important role in the regulation of an eclectic array of physiological processes. Their diverse functional role requires channels with a wide variety of properties even though the pore-forming α-subunit is encoded by a single gene, KCNMA1. To achieve this, BK channels exploit some of the most fundamental posttranscriptional and posttranslational mechanisms that allow proteomic diversity to be generated from a single gene. These include mechanisms that diversify mRNA variants and abundance such as alternative pre-mRNA splicing, editing, and control by miRNA. The BK channel is also subject to a diverse array of posttranslational modifications including protein phosphorylation, lipidation, glycosylation, and ubiquitination to control the number, properties, and regulation of BK channels in specific cell types. Importantly, "cross talk" between these posttranscriptional and posttranslational modifications typically converge on disordered domains of the BK channel α-subunit. This allows both wide physiological diversity to be generated and a diversity of mechanisms to allow conditional regulation of BK channels and is emerging as an important determinant of BK channel function in health and disease.
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Affiliation(s)
- M J Shipston
- Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, University of Edinburgh, Edinburgh, United Kingdom.
| | - L Tian
- Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, University of Edinburgh, Edinburgh, United Kingdom
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