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Echeverría F, Gonzalez-Sanabria N, Alvarado-Sanchez R, Fernández M, Castillo K, Latorre R. Large conductance voltage-and calcium-activated K + (BK) channel in health and disease. Front Pharmacol 2024; 15:1373507. [PMID: 38584598 PMCID: PMC10995336 DOI: 10.3389/fphar.2024.1373507] [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: 01/19/2024] [Accepted: 03/12/2024] [Indexed: 04/09/2024] Open
Abstract
Large Conductance Voltage- and Calcium-activated K+ (BK) channels are transmembrane pore-forming proteins that regulate cell excitability and are also expressed in non-excitable cells. They play a role in regulating vascular tone, neuronal excitability, neurotransmitter release, and muscle contraction. Dysfunction of the BK channel can lead to arterial hypertension, hearing disorders, epilepsy, and ataxia. Here, we provide an overview of BK channel functioning and the implications of its abnormal functioning in various diseases. Understanding the function of BK channels is crucial for comprehending the mechanisms involved in regulating vital physiological processes, both in normal and pathological conditions, controlled by BK. This understanding may lead to the development of therapeutic interventions to address BK channelopathies.
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Affiliation(s)
- Felipe Echeverría
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Naileth Gonzalez-Sanabria
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Rosangelina Alvarado-Sanchez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Miguel Fernández
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Karen Castillo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
- Centro de Investigación de Estudios Avanzados del Maule, Vicerrectoría de Investigación y Postgrado, Universidad Católica del Maule, Talca, Chile
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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2
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Cordero Padilla K, Monefeldt GA, Guevárez Galán A, Marrero HG, Lloret-Torres ME, Velázquez-Marrero C. BK ZERO isoform HEK293 stably transfected cell lines differing 3'UTRs to assess miR-9 regulation. PLoS One 2024; 19:e0298966. [PMID: 38502673 PMCID: PMC10950231 DOI: 10.1371/journal.pone.0298966] [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: 09/26/2023] [Accepted: 01/30/2024] [Indexed: 03/21/2024] Open
Abstract
Research has identified the large conductance voltage- and calcium-activated potassium channel (BK) as a key regulator of neuronal excitability genetically associated to behavioral alcohol tolerance. Sensitivity to ethanol at the molecular level is characterized by acute potentiation of channel activity. BK isoforms show variations in alcohol sensitivity and are differentially distributed on the plasma membrane surface in response to prolonged exposure. MicroRNA (MiRNA) targeting of alcohol-sensitive isoforms coupled with active internalization of BK channels in response to ethanol are believed to be key in establishing homeostatic adaptations that produce persistent changes within the plasma membrane of neurons. In fact, microRNA 9 (miR-9) upregulated expression is a key event in persistent alcohol tolerance mediating acute EtOH desensitization of BK channels. The exact nature of these interactions remains a current topic of discussion. To further study the effects of miR-9 on the expression and distribution of BK channel isoforms we designed an experimental model by transfecting human BK channel isoforms ZERO heterologous constructs in human embryonic kidney cells 293 (HEK293) cells respectively expressing 2.1 (miR-9 responsive), 2.2 (unresponsive) and control (no sequence) 3'untranslated region (3'UTR) miRNA recognition sites. We used imaging techniques to characterize the stably transfected monoclonal cell lines, and electrophysiology to validate channel activity. Finally, we used immunocytochemistry to validate isoform responsiveness to miR-9. Our findings suggest the cell lines were successfully transfected to express either the 2.1 or 2.2 version of ZERO. Patch clamp recordings confirm that these channels retain their functionality and immunohistochemistry shows differential responses to miR-9, making these cells viable for use in future alcohol dependence studies.
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Affiliation(s)
- Katherine Cordero Padilla
- Department of Anatomy and Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
- Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
- Windsor University School of Medicine, St. Kitts, West Indies
| | - Gerardo Alvarado Monefeldt
- Department of Biology, University of Puerto Rico Cayey Campus, Cayey, Puerto Rico
- Samuel Merritt University, Oakland, California, United States of America
| | - Adriel Guevárez Galán
- Department of Anatomy and Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
- Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
- Department of Biology, University of Puerto Rico Bayamón Campus, Bayamón, Puerto Rico
| | - Hector G. Marrero
- Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
| | - Mario E. Lloret-Torres
- Department of Anatomy and Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
- Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
| | - Cristina Velázquez-Marrero
- Department of Anatomy and Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
- Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico
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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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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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5
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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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Zahra A, Liu R, Han W, Meng H, Wang Q, Wang Y, Campbell SL, Wu J. K Ca-Related Neurological Disorders: Phenotypic Spectrum and Therapeutic Indications. Curr Neuropharmacol 2023; 21:1504-1518. [PMID: 36503451 PMCID: PMC10472807 DOI: 10.2174/1570159x21666221208091805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 07/21/2022] [Accepted: 07/23/2022] [Indexed: 12/14/2022] Open
Abstract
Although potassium channelopathies have been linked to a wide range of neurological conditions, the underlying pathogenic mechanism is not always clear, and a systematic summary of clinical manifestation is absent. Several neurological disorders have been associated with alterations of calcium-activated potassium channels (KCa channels), such as loss- or gain-of-function mutations, post-transcriptional modification, etc. Here, we outlined the current understanding of the molecular and cellular properties of three subtypes of KCa channels, including big conductance KCa channels (BK), small conductance KCa channels (SK), and the intermediate conductance KCa channels (IK). Next, we comprehensively reviewed the loss- or gain-of-function mutations of each KCa channel and described the corresponding mutation sites in specific diseases to broaden the phenotypic-genotypic spectrum of KCa-related neurological disorders. Moreover, we reviewed the current pharmaceutical strategies targeting KCa channels in KCa-related neurological disorders to provide new directions for drug discovery in anti-seizure medication.
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Affiliation(s)
- Aqeela Zahra
- School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China
- Department of Zoology, University of Sialkot, Sialkot 51310, Pakistan
| | - Ru Liu
- Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
- Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing 100070, China
- National Clinical Research Center for Neurological Diseases, Beijing 100070, China
| | - Wenzhe Han
- School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China
| | - Hui Meng
- School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China
| | - Qun Wang
- Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
- National Clinical Research Center for Neurological Diseases, Beijing 100070, China
| | - YunFu Wang
- School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China
| | - Susan L. Campbell
- Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, United States
| | - Jianping Wu
- School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, China
- Beijing Tiantan Hospital, Capital Medical University, Beijing 100070, China
- Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing 100070, China
- National Clinical Research Center for Neurological Diseases, Beijing 100070, China
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7
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Al‐Karagholi MA, Hakbilen CC, Ashina M. The role of high-conductance calcium-activated potassium channel in headache and migraine pathophysiology. Basic Clin Pharmacol Toxicol 2022; 131:347-354. [PMID: 36028922 PMCID: PMC9826089 DOI: 10.1111/bcpt.13787] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 07/17/2022] [Accepted: 08/25/2022] [Indexed: 01/11/2023]
Abstract
Migraine is a common, neurovascular headache disorder with a complex molecular interplay. The involvement of ion channels in the pathogenesis of migraine gathered considerable attention with the findings that different ion channels subfamilies are expressed in trigeminovascular system, the physiological substrate of migraine pain, and several ion channel openers investigated in clinical trials with diverse primary endpoints caused headache as a frequent side effect. High-conductance (big) calcium-activated potassium (BKCa ) channel is expressed in the cranial arteries and the trigeminal pain pathway. Recent clinical research revealed that infusion of BKCa channel opener MaxiPost caused vasodilation, headache and migraine attack. Thus, BKCa channel is involved in pathophysiological mechanisms underlying headache and migraine, and targeting BKCa channel presents a new potential strategy for migraine treatment.
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Affiliation(s)
- Mohammad Al‐Mahdi Al‐Karagholi
- Danish Headache Center, Department of Neurology, Rigshospitalet Glostrup, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Cemile Ceren Hakbilen
- Danish Headache Center, Department of Neurology, Rigshospitalet Glostrup, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Messoud Ashina
- Danish Headache Center, Department of Neurology, Rigshospitalet Glostrup, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
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8
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Abstract
In neurosecretion, allosteric communication between voltage sensors and Ca2+ binding in BK channels is crucially involved in damping excitatory stimuli. Nevertheless, the voltage-sensing mechanism of BK channels is still under debate. Here, based on gating current measurements, we demonstrate that two arginines in the transmembrane segment S4 (R210 and R213) function as the BK gating charges. Significantly, the energy landscape of the gating particles is electrostatically tuned by a network of salt bridges contained in the voltage sensor domain (VSD). Molecular dynamics simulations and proton transport experiments in the hyperpolarization-activated R210H mutant suggest that the electric field drops off within a narrow septum whose boundaries are defined by the gating charges. Unlike Kv channels, the charge movement in BK appears to be limited to a small displacement of the guanidinium moieties of R210 and R213, without significant movement of the S4.
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Wiggers A, Ashina H, Hadjikhani N, Sagare A, Zlokovic BV, Lauritzen M, Ashina M. Brain barriers and their potential role in migraine pathophysiology. J Headache Pain 2022; 23:16. [PMID: 35081902 PMCID: PMC8903554 DOI: 10.1186/s10194-021-01365-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 11/29/2021] [Indexed: 12/19/2022] Open
Abstract
Migraine is a ubiquitous neurologic disease that afflicts people of all ages. Its molecular pathogenesis involves peptides that promote intracranial vasodilation and modulate nociceptive transmission upon release from sensory afferents of cells in the trigeminal ganglion and parasympathetic efferents of cells in the sphenopalatine ganglion. Experimental data have confirmed that intravenous infusion of these vasoactive peptides induce migraine attacks in people with migraine, but it remains a point of scientific contention whether their site of action lies outside or within the central nervous system. In this context, it has been hypothesized that transient dysfunction of brain barriers before or during migraine attacks might facilitate the passage of migraine-inducing peptides into the central nervous system. Here, we review evidence suggestive of brain barrier dysfunction in migraine pathogenesis and conclude with lessons learned in order to provide directions for future research efforts.
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González-Sanabria N, Echeverría F, Segura I, Alvarado-Sánchez R, Latorre R. BK in Double-Membrane Organelles: A Biophysical, Pharmacological, and Functional Survey. Front Physiol 2021; 12:761474. [PMID: 34764886 PMCID: PMC8577798 DOI: 10.3389/fphys.2021.761474] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 09/29/2021] [Indexed: 12/04/2022] Open
Abstract
In the 1970s, calcium-activated potassium currents were recorded for the first time. In 10years, this Ca2+-activated potassium channel was identified in rat skeletal muscle, chromaffin cells and characterized in skeletal muscle membranes reconstituted in lipid bilayers. This calcium- and voltage-activated potassium channel, dubbed BK for “Big K” due to its large ionic conductance between 130 and 300 pS in symmetric K+. The BK channel is a tetramer where the pore-forming α subunit contains seven transmembrane segments. It has a modular architecture containing a pore domain with a highly potassium-selective filter, a voltage-sensor domain and two intracellular Ca2+ binding sites in the C-terminus. BK is found in the plasma membrane of different cell types, the inner mitochondrial membrane (mitoBK) and the nuclear envelope’s outer membrane (nBK). Like BK channels in the plasma membrane (pmBK), the open probability of mitoBK and nBK channels are regulated by Ca2+ and voltage and modulated by auxiliary subunits. BK channels share common pharmacology to toxins such as iberiotoxin, charybdotoxin, paxilline, and agonists of the benzimidazole family. However, the precise role of mitoBK and nBK remains largely unknown. To date, mitoBK has been reported to play a role in protecting the heart from ischemic injury. At the same time, pharmacology suggests that nBK has a role in regulating nuclear Ca2+, membrane potential and expression of eNOS. Here, we will discuss at the biophysical level the properties and differences of mitoBK and nBK compared to those of pmBK and their pharmacology and function.
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Affiliation(s)
- Naileth González-Sanabria
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Felipe Echeverría
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Ignacio Segura
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Rosangelina Alvarado-Sánchez
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Ramon Latorre
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
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Uray IP, Uray K. Mechanotransduction at the Plasma Membrane-Cytoskeleton Interface. Int J Mol Sci 2021; 22:11566. [PMID: 34768998 PMCID: PMC8584042 DOI: 10.3390/ijms222111566] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/19/2021] [Accepted: 10/21/2021] [Indexed: 02/08/2023] Open
Abstract
Mechanical cues are crucial for survival, adaptation, and normal homeostasis in virtually every cell type. The transduction of mechanical messages into intracellular biochemical messages is termed mechanotransduction. While significant advances in biochemical signaling have been made in the last few decades, the role of mechanotransduction in physiological and pathological processes has been largely overlooked until recently. In this review, the role of interactions between the cytoskeleton and cell-cell/cell-matrix adhesions in transducing mechanical signals is discussed. In addition, mechanosensors that reside in the cell membrane and the transduction of mechanical signals to the nucleus are discussed. Finally, we describe two examples in which mechanotransduction plays a significant role in normal physiology and disease development. The first example is the role of mechanotransduction in the proliferation and metastasis of cancerous cells. In this system, the role of mechanotransduction in cellular processes, including proliferation, differentiation, and motility, is described. In the second example, the role of mechanotransduction in a mechanically active organ, the gastrointestinal tract, is described. In the gut, mechanotransduction contributes to normal physiology and the development of motility disorders.
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Affiliation(s)
- Iván P. Uray
- Department of Clinical Oncology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary;
| | - Karen Uray
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
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12
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Lu T, Lee HC. Coronary Large Conductance Ca 2+-Activated K + Channel Dysfunction in Diabetes Mellitus. Front Physiol 2021; 12:750618. [PMID: 34744789 PMCID: PMC8567020 DOI: 10.3389/fphys.2021.750618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/14/2021] [Indexed: 11/24/2022] Open
Abstract
Diabetes mellitus (DM) is an independent risk of macrovascular and microvascular complications, while cardiovascular diseases remain a leading cause of death in both men and women with diabetes. Large conductance Ca2+-activated K+ (BK) channels are abundantly expressed in arteries and are the key ionic determinant of vascular tone and organ perfusion. It is well established that the downregulation of vascular BK channel function with reduced BK channel protein expression and altered intrinsic BK channel biophysical properties is associated with diabetic vasculopathy. Recent efforts also showed that diabetes-associated changes in signaling pathways and transcriptional factors contribute to the downregulation of BK channel expression. This manuscript will review our current understandings on the molecular, physiological, and biophysical mechanisms that underlie coronary BK channelopathy in diabetes mellitus.
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Affiliation(s)
- Tong Lu
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, United States
| | - Hon-Chi Lee
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, United States
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13
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Al-Karagholi MAM, Ghanizada H, Waldorff Nielsen CA, Skandarioon C, Snellman J, Lopez-Lopez C, Hansen JM, Ashina M. Opening of BKCa channels causes migraine attacks: a new downstream target for the treatment of migraine. Pain 2021; 162:2512-2520. [PMID: 34252916 DOI: 10.1097/j.pain.0000000000002238] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 02/08/2021] [Indexed: 11/25/2022]
Abstract
ABSTRACT Migraine is a common and frequently disabling neurological disorder, but the initiating migraine mechanisms are still poorly understood. Potassium channel opening may cause migraine, and we therefore examined the migraine-inducing effect of MaxiPost, a large (big)-conductance calcium-activated potassium (BKCa) channel opener, on migraine induction and cephalic vasodilation in individuals with migraine. Twenty-six patients with migraine without aura were randomly allocated to receive an infusion of MaxiPost or placebo on 2 study days separated by at least 1 week. The primary endpoint was the difference in incidence of migraine attacks after MaxiPost compared with placebo. The secondary endpoints were the difference in incidence of headaches and the difference in area under the curve for headache intensity scores (0-12 hours), for middle cerebral artery blood flow velocity (VMCA) (0-2 hours), and for superficial temporal artery and radial artery diameter. Twenty-two patients completed the study. Twenty-one of 22 (95%) developed migraine attacks after MaxiPost compared with none after placebo (P < 0.0001); the difference of incidence is 95% (95% confidence interval 86%-100%). The incidence of headache over the 12-hour observation period was higher after MaxiPost day (n = 22) than after placebo (n = 7) (P < 0.0001). We found a significant increase of VMCA and superficial temporal and radial arteries' diameter. Because BKCa channel opening initiates migraine attacks, we suggest that BKCa channel blockers could be potential candidates for novel antimigraine drugs.
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Affiliation(s)
- Mohammad Al-Mahdi Al-Karagholi
- Department of Neurology, Danish Headache Center, Rigshospitalet-Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Hashmat Ghanizada
- Department of Neurology, Danish Headache Center, Rigshospitalet-Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Cherie Amalie Waldorff Nielsen
- Department of Neurology, Danish Headache Center, Rigshospitalet-Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Camilla Skandarioon
- Department of Neurology, Danish Headache Center, Rigshospitalet-Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | | | - Jakob Møller Hansen
- Department of Neurology, Danish Headache Center, Rigshospitalet-Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Danish Knowledge Center on Headache Disorders, Rigshospitalet-Glostrup, Denmark
| | - Messoud Ashina
- Department of Neurology, Danish Headache Center, Rigshospitalet-Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Novartis Pharma AG, Basel, Switzerland
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14
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Wang X, Xiao Q, Zhu Y, Qi H, Qu D, Yao Y, Jia Y, Guo J, Cheng J, Ji Y, Li G, Tao J. Glycosylation of β1 subunit plays a pivotal role in the toxin sensitivity and activation of BK channels. J Venom Anim Toxins Incl Trop Dis 2021; 27:e20200182. [PMID: 34149831 PMCID: PMC8183112 DOI: 10.1590/1678-9199-jvatitd-2020-0182] [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] [Indexed: 11/22/2022] Open
Abstract
Background: The accessory β1 subunits, regulating the pharmacological and biophysical properties of BK channels, always undergo post-translational modifications, especially glycosylation. To date, it remains elusive whether the glycosylation contributes to the regulation of BK channels by β1 subunits. Methods: Herein, we combined the electrophysiological approach with molecular mutations and biochemical manipulation to investigate the function roles of N-glycosylation in β1 subunits. Results: The results show that deglycosylation of β1 subunits through double-site mutations (β1 N80A/N142A or β1 N80Q/N142Q) could significantly increase the inhibitory potency of iberiotoxin, a specific BK channel blocker. The deglycosylated channels also have a different sensitivity to martentoxin, another BK channel modulator with some remarkable effects as reported before. On the contrary to enhancing effects of martentoxin on glycosylated BK channels under the presence of cytoplasmic Ca2+, deglycosylated channels were not affected by the toxin. However, the deglycosylated channels were surprisingly inhibited by martentoxin under the absence of cytoplasmic Ca2+, while the glycosylated channels were not inhibited under this same condition. In addition, wild type BK (α+β1) channels treated with PNGase F also showed the same trend of pharmacological results to the mutants. Similar to this modulation of glycosylation on BK channel pharmacology, the deglycosylated forms of the channels were activated at a faster speed than the glycosylated ones. However, the V1/2 and slope were not changed by the glycosylation. Conclusion: The present study reveals that glycosylation is an indispensable determinant of the modulation of β1-subunit on BK channel pharmacology and its activation. The loss of glycosylation of β1 subunits could lead to the dysfunction of BK channel, resulting in a pathological state.
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Affiliation(s)
- Xiaoli Wang
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China
| | - Qian Xiao
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yudan Zhu
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Hong Qi
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China
| | - Dongxiao Qu
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yu Yao
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China
| | - Yuxiang Jia
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China
| | - Jingkan Guo
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China.,Xinhua Translational Institute for Cancer Pain, Shanghai, China
| | - Jiwei Cheng
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China.,Putuo Clinical Medical School, Anhui Medical University, Shanghai, China
| | - Yonghua Ji
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China.,Xinhua Translational Institute for Cancer Pain, Shanghai, China
| | - Guoyi Li
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China.,Putuo Clinical Medical School, Anhui Medical University, Shanghai, China
| | - Jie Tao
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China.,Putuo Clinical Medical School, Anhui Medical University, Shanghai, China
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15
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Lee N, Lim BH, Lee KS, Shin J, Pagire HS, Pagire SH, Ahn JH, Lee SW, Kang TM, Park CS. Identification and Characterization of a Novel Large-Conductance Calcium-Activated Potassium Channel Activator, CTIBD, and Its Relaxation Effect on Urinary Bladder Smooth Muscle. Mol Pharmacol 2020; 99:114-124. [PMID: 33268552 DOI: 10.1124/molpharm.120.000106] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 11/11/2020] [Indexed: 12/14/2022] Open
Abstract
The large-conductance calcium-activated potassium channel (BKCa channel) is expressed on various tissues and is involved in smooth muscle relaxation. The channel is highly expressed on urinary bladder smooth muscle cells and regulates the repolarization phase of the spontaneous action potentials that control muscle contraction. To discover novel chemical activators of the BKCa channel, we screened a chemical library containing 8364 chemical compounds using a cell-based fluorescence assay. A chemical compound containing an isoxazolyl benzene skeleton (compound 1) was identified as a potent activator of the BKCa channel and was structurally optimized through a structure-activity relationship study to obtain 4-(4-(4-chlorophenyl)-3-(trifluoromethyl)isoxazol-5-yl)benzene-1,3-diol (CTIBD). When CTIBD was applied to the treated extracellular side of the channel, the conductance-voltage relationship of the channel shifted toward a negative value, and the maximum conductance increased in a concentration-dependent manner. CTIBD altered the gating kinetics of the channel by dramatically slowing channel closing without effecting channel opening. The effects of CTIBD on bladder muscle relaxation and micturition function were tested in rat tissue and in vivo. CTIBD concentration-dependently reduced acetylcholine-induced contraction of urinary bladder smooth muscle strips. In an acetic acid-induced overactive bladder (OAB) model, intraperitoneal injection of 20 mg/kg CTIBD effectively restored frequent voiding contraction and lowered voiding volume without affecting other bladder function parameters. Thus, our results indicate that CTIBD and its derivatives are novel chemical activators of the bladder BKCa channel and potential candidates for OAB therapeutics. SIGNIFICANCE STATEMENT: The novel BKCa channel activator CTIBD was identified and characterized in this study. CTIBD directly activates the BKCa channel and relaxes urinary bladder smooth muscle of rat, so CTIBD can be a potential candidate for overactive bladder therapeutics.
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Affiliation(s)
- Narasaem Lee
- School of Life Sciences, Center for AI-applied High Efficiency Drug Discovery and Integrated Institute of Biomedical Research (N.L., C.-S.P.) and Department of Chemistry (H.S.P., S.H.P., J.H.A.), Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea; Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, South Korea (B.H.L., K.-S.L., J.S., S.W.L.); and Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, South Korea (T.M.K.)
| | - Bong Hee Lim
- School of Life Sciences, Center for AI-applied High Efficiency Drug Discovery and Integrated Institute of Biomedical Research (N.L., C.-S.P.) and Department of Chemistry (H.S.P., S.H.P., J.H.A.), Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea; Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, South Korea (B.H.L., K.-S.L., J.S., S.W.L.); and Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, South Korea (T.M.K.)
| | - Kyu-Sung Lee
- School of Life Sciences, Center for AI-applied High Efficiency Drug Discovery and Integrated Institute of Biomedical Research (N.L., C.-S.P.) and Department of Chemistry (H.S.P., S.H.P., J.H.A.), Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea; Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, South Korea (B.H.L., K.-S.L., J.S., S.W.L.); and Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, South Korea (T.M.K.)
| | - Jimin Shin
- School of Life Sciences, Center for AI-applied High Efficiency Drug Discovery and Integrated Institute of Biomedical Research (N.L., C.-S.P.) and Department of Chemistry (H.S.P., S.H.P., J.H.A.), Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea; Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, South Korea (B.H.L., K.-S.L., J.S., S.W.L.); and Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, South Korea (T.M.K.)
| | - Haushabhau S Pagire
- School of Life Sciences, Center for AI-applied High Efficiency Drug Discovery and Integrated Institute of Biomedical Research (N.L., C.-S.P.) and Department of Chemistry (H.S.P., S.H.P., J.H.A.), Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea; Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, South Korea (B.H.L., K.-S.L., J.S., S.W.L.); and Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, South Korea (T.M.K.)
| | - Suvarna H Pagire
- School of Life Sciences, Center for AI-applied High Efficiency Drug Discovery and Integrated Institute of Biomedical Research (N.L., C.-S.P.) and Department of Chemistry (H.S.P., S.H.P., J.H.A.), Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea; Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, South Korea (B.H.L., K.-S.L., J.S., S.W.L.); and Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, South Korea (T.M.K.)
| | - Jin Hee Ahn
- School of Life Sciences, Center for AI-applied High Efficiency Drug Discovery and Integrated Institute of Biomedical Research (N.L., C.-S.P.) and Department of Chemistry (H.S.P., S.H.P., J.H.A.), Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea; Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, South Korea (B.H.L., K.-S.L., J.S., S.W.L.); and Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, South Korea (T.M.K.)
| | - Sung Won Lee
- School of Life Sciences, Center for AI-applied High Efficiency Drug Discovery and Integrated Institute of Biomedical Research (N.L., C.-S.P.) and Department of Chemistry (H.S.P., S.H.P., J.H.A.), Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea; Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, South Korea (B.H.L., K.-S.L., J.S., S.W.L.); and Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, South Korea (T.M.K.)
| | - Tong Mook Kang
- School of Life Sciences, Center for AI-applied High Efficiency Drug Discovery and Integrated Institute of Biomedical Research (N.L., C.-S.P.) and Department of Chemistry (H.S.P., S.H.P., J.H.A.), Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea; Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, South Korea (B.H.L., K.-S.L., J.S., S.W.L.); and Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, South Korea (T.M.K.)
| | - Chul-Seung Park
- School of Life Sciences, Center for AI-applied High Efficiency Drug Discovery and Integrated Institute of Biomedical Research (N.L., C.-S.P.) and Department of Chemistry (H.S.P., S.H.P., J.H.A.), Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea; Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, South Korea (B.H.L., K.-S.L., J.S., S.W.L.); and Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, South Korea (T.M.K.)
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16
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Wawrzkiewicz-Jałowiecka A, Trybek P, Borys P, Dworakowska B, Machura Ł, Bednarczyk P. Differences in Gating Dynamics of BK Channels in Cellular and Mitochondrial Membranes from Human Glioblastoma Cells Unraveled by Short- and Long-Range Correlations Analysis. Cells 2020; 9:E2305. [PMID: 33076484 PMCID: PMC7602617 DOI: 10.3390/cells9102305] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 10/09/2020] [Accepted: 10/12/2020] [Indexed: 02/04/2023] Open
Abstract
The large-conductance voltage- and Ca2+-activated K+ channels (BK) are encoded in humans by the Kcnma1 gene. Nevertheless, BK channel isoforms in different locations can exhibit functional heterogeneity mainly due to the alternative splicing during the Kcnma1 gene transcription. Here, we would like to examine the existence of dynamic diversity of BK channels from the inner mitochondrial and cellular membrane from human glioblastoma (U-87 MG). Not only the standard characteristics of the spontaneous switching between the functional states of the channel is discussed, but we put a special emphasis on the presence and strength of correlations within the signal describing the single-channel activity. The considered short- and long-range memory effects are here analyzed as they can be interpreted in terms of the complexity of the switching mechanism between stable conformational states of the channel. We calculate the dependencies of mean dwell-times of (conducting/non-conducting) states on the duration of the previous state, Hurst exponents by the rescaled range R/S method and detrended fluctuation analysis (DFA), and use the multifractal extension of the DFA (MFDFA) for the series describing single-channel activity. The obtained results unraveled statistically significant diversity in gating machinery between the mitochondrial and cellular BK channels.
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Affiliation(s)
- Agata Wawrzkiewicz-Jałowiecka
- Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, 44-100 Gliwice, Poland;
| | - Paulina Trybek
- Faculty of Science and Technology, University of Silesia in Katowice, 41-500 Chorzow, Poland;
| | - Przemysław Borys
- Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, 44-100 Gliwice, Poland;
| | - Beata Dworakowska
- Institute of Biology, Department of Physics and Biophysics, Warsaw University of Life Sciences—SGGW, 02-787 Warszawa, Poland; (B.D.); (P.B.)
| | - Łukasz Machura
- Institute of Physics, Faculty of Science and Technology, University of Silesia in Katowice, 41-500 Chorzow, Poland;
| | - Piotr Bednarczyk
- Institute of Biology, Department of Physics and Biophysics, Warsaw University of Life Sciences—SGGW, 02-787 Warszawa, Poland; (B.D.); (P.B.)
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17
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Al-Karagholi MAM, Gram C, Nielsen CAW, Ashina M. Targeting BK Ca Channels in Migraine: Rationale and Perspectives. CNS Drugs 2020; 34:325-335. [PMID: 32060729 DOI: 10.1007/s40263-020-00706-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Large (big)-conductance calcium-activated potassium (BKCa) channels are expressed in migraine-related structures such as the cranial arteries, trigeminal ganglion and trigeminal spinal nucleus, and they play a substantial role in vascular tonus and neuronal excitability. Using synthetic BKCa channels openers was associated with headache as a frequent adverse effect in healthy volunteers. Additionally, BKCa channels are downstream molecules in migraine signalling pathways that are activated by several compounds known to provoke migraine, including calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase-activating polypeptide (PACAP) and glyceryl trinitrate (GTN). Also, there is a high affinity and a close coupling between BKCa channels and ATP-sensitive potassium (KATP) channels, the role of which has recently been established in migraine pathophysiology. These observations raise the question as to whether direct BKCa channel activation can provoke migraine in migraine patients, and whether the BKCa channel could be a potential novel anti-migraine target. Hence, randomized and placebo-controlled clinical studies on BKCa channel openers or blockers in migraine patients are needed.
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Affiliation(s)
- Mohammad Al-Mahdi Al-Karagholi
- Danish Headache Center, Department of Neurology, University of Copenhagen, Valdemar Hansen Vej 5, 2600, Glostrup, Denmark
| | - Christian Gram
- Danish Headache Center, Department of Neurology, University of Copenhagen, Valdemar Hansen Vej 5, 2600, Glostrup, Denmark
| | - Cherie Amalie Waldorff Nielsen
- Danish Headache Center, Department of Neurology, University of Copenhagen, Valdemar Hansen Vej 5, 2600, Glostrup, Denmark
| | - Messoud Ashina
- Danish Headache Center, Department of Neurology, University of Copenhagen, Valdemar Hansen Vej 5, 2600, Glostrup, Denmark. .,Glostrup Research Park, Rigshospitalet Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Glostrup, Denmark.
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18
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Yeste M, Llavanera M, Pérez G, Scornik F, Puig-Parri J, Brugada R, Bonet S, Pinart E. Elucidating the Role of K + Channels during In Vitro Capacitation of Boar Spermatozoa: Do SLO1 Channels Play a Crucial Role? Int J Mol Sci 2019; 20:E6330. [PMID: 31847486 PMCID: PMC6940911 DOI: 10.3390/ijms20246330] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/05/2019] [Accepted: 12/13/2019] [Indexed: 01/16/2023] Open
Abstract
This study sought to identify and localize SLO1 channels in boar spermatozoa by immunoblotting and immunofluorescence, and to determine their physiological role during in vitro sperm capacitation. Sperm samples from 14 boars were incubated in a capacitation medium for 300 min in the presence of paxilline (PAX), a specific SLO1-channel blocker, added either at 0 min or after 240 min of incubation. Negative controls were incubated in capacitation medium, and positive controls in capacitation medium plus tetraethyl ammonium (TEA), a general K+-channel blocker, also added at 0 min or after 240 min of incubation. In all samples, acrosome exocytosis was triggered with progesterone after 240 min of incubation. Sperm motility and kinematics, integrity of plasma and acrosome membranes, membrane lipid disorder, intracellular calcium levels and acrosin activity were evaluated after 0, 60, 120, 180, 240, 250, 270 and 300 min of incubation. In boar spermatozoa, SLO1 channels were found to have 80 kDa and be localized in the anterior postacrosomal region and the mid and principal piece of the tail; their specific blockage through PAX resulted in altered calcium levels and acrosome exocytosis. As expected, TEA blocker impaired in vitro sperm capacitation, by altering sperm motility and kinematics and calcium levels. In conclusion, SLO1 channels are crucial for the acrosome exocytosis induced by progesterone in in vitro capacitated boar spermatozoa.
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Affiliation(s)
- Marc Yeste
- Unit of Cell Biology, Biotechnology of Animal and Human Reproduction (TechnoSperm), Department of Biology, Faculty of Sciences, Institute of Food and Agricultural Technology, University of Girona, E-17003 Girona, Spain; (M.Y.); (M.L.); (J.P.-P.); (S.B.)
| | - Marc Llavanera
- Unit of Cell Biology, Biotechnology of Animal and Human Reproduction (TechnoSperm), Department of Biology, Faculty of Sciences, Institute of Food and Agricultural Technology, University of Girona, E-17003 Girona, Spain; (M.Y.); (M.L.); (J.P.-P.); (S.B.)
| | - Guillermo Pérez
- Department of Medical Sciences, Faculty of Medicine, University of Girona, E-17003 Girona, Spain; (G.P.); (F.S.); (R.B.)
- Cardiovascular Genetics Group, Girona Biomedical Research Institute (IDIBGI), E-17190 Girona, Spain
- Biomedical Research Networking Center on Cardiovascular Diseases (CIBERCV), E-28029 Madrid, Spain
| | - Fabiana Scornik
- Department of Medical Sciences, Faculty of Medicine, University of Girona, E-17003 Girona, Spain; (G.P.); (F.S.); (R.B.)
- Cardiovascular Genetics Group, Girona Biomedical Research Institute (IDIBGI), E-17190 Girona, Spain
- Biomedical Research Networking Center on Cardiovascular Diseases (CIBERCV), E-28029 Madrid, Spain
| | - Josep Puig-Parri
- Unit of Cell Biology, Biotechnology of Animal and Human Reproduction (TechnoSperm), Department of Biology, Faculty of Sciences, Institute of Food and Agricultural Technology, University of Girona, E-17003 Girona, Spain; (M.Y.); (M.L.); (J.P.-P.); (S.B.)
| | - Ramon Brugada
- Department of Medical Sciences, Faculty of Medicine, University of Girona, E-17003 Girona, Spain; (G.P.); (F.S.); (R.B.)
- Cardiovascular Genetics Group, Girona Biomedical Research Institute (IDIBGI), E-17190 Girona, Spain
- Biomedical Research Networking Center on Cardiovascular Diseases (CIBERCV), E-28029 Madrid, Spain
- Cardiology Service, Hospital Josep Trueta, E-17003 Girona, Spain
| | - Sergi Bonet
- Unit of Cell Biology, Biotechnology of Animal and Human Reproduction (TechnoSperm), Department of Biology, Faculty of Sciences, Institute of Food and Agricultural Technology, University of Girona, E-17003 Girona, Spain; (M.Y.); (M.L.); (J.P.-P.); (S.B.)
| | - Elisabeth Pinart
- Unit of Cell Biology, Biotechnology of Animal and Human Reproduction (TechnoSperm), Department of Biology, Faculty of Sciences, Institute of Food and Agricultural Technology, University of Girona, E-17003 Girona, Spain; (M.Y.); (M.L.); (J.P.-P.); (S.B.)
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19
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Clusin WT, Wu TH, Shi LF, Kao PN. Further studies of ion channels in the electroreceptor of the skate through deep sequencing, cloning and cross species comparisons. Gene 2019; 718:143989. [PMID: 31326551 DOI: 10.1016/j.gene.2019.143989] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Revised: 06/23/2019] [Accepted: 07/17/2019] [Indexed: 11/25/2022]
Abstract
Our comparative studies seek to understand the structure and function of ion channels in cartilaginous fish that can detect very low voltage gradients in seawater. The principal channels of the electroreceptor include a calcium activated K channel whose α subunit is Kcnma1, and a voltage-dependent calcium channel, Cacna1d. It has also been suggested based on physiological and pharmacological evidence that a voltage-gated K channel is present in the basal membranes of the receptor cells which modulates synaptic transmitter release. Large conductance calcium-activated K channels (BK) are comprised of four α subunits, encoded by Kcnma1 and modulatory β subunits of the Kcnmb class. We recently cloned and published the skate Kcnma1 gene and most of Kcnmb4 using purified mRNA of homogenized electroreceptors. Bellono et al. have recently performed RNA sequencing (RNA-seq) on purified mRNA from skate electroreceptors and found several ion channels including Kcnma1. We searched the Bellono et al. RNA-seq repository for additional channels and subunits. Our most significant findings are the presence of two Shaker type voltage dependent K channel sequences which are grouped together as isoforms in the data repository. The larger of these is a skate ortholog of the voltage dependent fast potassium channel Kv1.1, which is expressed at appreciable levels. The second ortholog is similar to Kv1.5 but has fewer N-terminal amino acids than other species. The sequence for Kv1.5 in the skate is very strongly aligned with the recently reported sequence for potassium channels in the electroreceptors of the cat shark, S. retifer, which also modulate synaptic transmission. The latter channel was designated as Kv1.3 in the initial report, but we suggest that these channels are actually orthologs of each other, and that Kv1.5 is the prevailing designation. We also found a beta subunit sequence (Kcnab2) which may co-assemble with one or both of the voltage gated channels. The new channels and subunits were verified by RT-PCR and the Kv1.1 sequence was confirmed by cloning. We also searched the RNA-seq repository for accessory subunits of Kcnma1, and found a computer-generated assembly that contained a complete sequence of its β subunit, Kcnmb2. Skate Kcnmb2 has a total of 279 amino acids, with 51 novel amino acids at the N-terminus which may play a specific physiological role. This sequence was confirmed by PCR and cloning. However, skate Kcnmb2 is expressed at low levels in the electroreceptor compared to Kcnma1 and skate Kcnmb1 is absent. The evolutionary origin of the newly described K channels and their subunits was studied by alignments with mammalian sequences, including human, and also those in related fish: the whale shark (R. typus), the ghost shark (C.milii), and (S. retifer). There are also orthologous K channels of the lamprey, which has electroreceptors. Tree building and bootstrap programs were used to confirm phylogenetic inferences. Further research should focus on the subcellular locations of these channels, their gating behavior, and the effects of accessory subunits on gating.
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Affiliation(s)
- William T Clusin
- Department of Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94305, United States of America.
| | - Ting-Hsuan Wu
- Department of Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94305, United States of America
| | - Ling-Fang Shi
- Department of Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94305, United States of America
| | - Peter N Kao
- Department of Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94305, United States of America
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20
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Liu S, Gao X, Wu X, Yu Y, Yu Z, Zhao S, Zhao H. BK channels regulate calcium oscillations in ventricular myocytes on different substrate stiffness. Life Sci 2019; 235:116802. [PMID: 31472150 DOI: 10.1016/j.lfs.2019.116802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 08/26/2019] [Accepted: 08/28/2019] [Indexed: 01/29/2023]
Abstract
Substrate stiffness is essential for cell functions, but the mechanisms by which cell sense mechanical cues are still unclear. Here we show that the frequency and the amplitude of spontaneous Ca2+ oscillations were greater in chick cardiomyocytes cultured on the stiff substrates than that on the soft substrates. The spontaneous Ca2+ oscillations were increased on stiff substrates. However, an eliminated dependence of the Ca2+ oscillations on substrate stiffness was observed after applying blocker of the large-conductance Ca2+-activated K+ (BK) channels. In addition, the activity of BK channels in cardiomyocytes cultured on the stiff substrates was decreased. These results provide compelling evidences to show that BK channels are crucial in substrate stiffness-dependent regulation of the Ca2+ oscillation in cardiomyocytes.
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Affiliation(s)
- Sisi Liu
- Institute of Biomechanics and Medical Engineering, School of Aerospace Engineering, Tsinghua University, Beijing 100084, PR China
| | - Xiaohui Gao
- Department of Microbial Pathogenesis, Yale School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA
| | - Xiaoan Wu
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Yang Yu
- Institute of Biomechanics and Medical Engineering, School of Aerospace Engineering, Tsinghua University, Beijing 100084, PR China
| | - Zhang Yu
- Institute of Biomechanics and Medical Engineering, School of Aerospace Engineering, Tsinghua University, Beijing 100084, PR China
| | - Sui Zhao
- Affiliated High School of Tsinghua University, Beijing 100084, PR China
| | - Hucheng Zhao
- Institute of Biomechanics and Medical Engineering, School of Aerospace Engineering, Tsinghua University, Beijing 100084, PR China.
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21
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Xin F, Cheng Y, Ren J, Zhang S, Liu P, Zhao H, Huang H, Wang W. The extracellular loop of the auxiliary β1-subunit is involved in the regulation of BKCa channel mechanosensitivity. Am J Physiol Cell Physiol 2018; 315:C485-C493. [DOI: 10.1152/ajpcell.00037.2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The large conductance Ca2+-activated potassium (BKCa) channel is activated by stretch. The stress-regulated exon (STREX) in α-subunits is known to affect the mechanosensitivity of BKCa channels. However, in human colonic smooth muscle cells (HCoSMCs), we found that the α-subunits without STREX (ZERO-BK) and β1-subunits could be detected yet the cells were mechanosensitive. Whether the β1-subunit is involved in the regulation of BKCa mechanosensitivity is unclear. In the present study, ZERO-BK and β1-subunits were individually expressed or coexpressed in HEK293 cells and cell-attached patch-clamp techniques were used to measure BKCa currents defining mechanosensitivity. Single-channel patch-clamp recordings from HEK293 cells cotransfected with ZERO-BK and β1-subunits showed stretch sensitivity, but there was no mechanosensitivity in HEK293 cells transfected only with ZERO-BK. We also showed that expression of the β1-subunit could increase mechanosensitivity of the STREX-type α-subunits (STREX-BK). To identify the domain in β1-subunits responsible for affecting stretch sensitivity, we expressed β1- LoopDel (chimeric β1-subunits without the extracellular loop) or β1- C TermDel (chimeric β1-subunits without COOH terminus) with ZERO-BK in HEK293 cells. The data showed that deletion of the extracellular loop but not the COOH terminus of β1-subunits virtually abolished the mechanosensitivity. These results suggest that the extracellular loop of the β1-subunit is involved in the regulation of BKCa channel mechanosensitivity and that role is independent of STREX.
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Affiliation(s)
- Fang Xin
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
| | - Yuan Cheng
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
| | - Jie Ren
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
- Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Diseases, Capital Medical University, Beijing, People’s Republic of China
| | - Sitao Zhang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
| | - Ping Liu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
| | - Haiyan Zhao
- Yanjing Medical College, Capital Medical University, Beijing, People’s Republic of China
| | - Haixia Huang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
- Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Diseases, Capital Medical University, Beijing, People’s Republic of China
| | - Wei Wang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
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22
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Sclip A, Acuna C, Luo F, Südhof TC. RIM-binding proteins recruit BK-channels to presynaptic release sites adjacent to voltage-gated Ca 2+-channels. EMBO J 2018; 37:embj.201798637. [PMID: 29967030 PMCID: PMC6092624 DOI: 10.15252/embj.201798637] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 06/01/2018] [Accepted: 06/04/2018] [Indexed: 12/31/2022] Open
Abstract
The active zone of presynaptic nerve terminals organizes the neurotransmitter release machinery, thereby enabling fast Ca2+-triggered synaptic vesicle exocytosis. BK-channels are Ca2+-activated large-conductance K+-channels that require close proximity to Ca2+-channels for activation and control Ca2+-triggered neurotransmitter release by accelerating membrane repolarization during action potential firing. How BK-channels are recruited to presynaptic Ca2+-channels, however, is unknown. Here, we show that RBPs (for RIM-binding proteins), which are evolutionarily conserved active zone proteins containing SH3- and FN3-domains, directly bind to BK-channels. We find that RBPs interact with RIMs and Ca2+-channels via their SH3-domains, but to BK-channels via their FN3-domains. Deletion of RBPs in calyx of Held synapses decreased and decelerated presynaptic BK-currents and depleted BK-channels from active zones. Our data suggest that RBPs recruit BK-channels into a RIM-based macromolecular active zone complex that includes Ca2+-channels, synaptic vesicles, and the membrane fusion machinery, thereby enabling tight spatio-temporal coupling of Ca2+-influx to Ca2+-triggered neurotransmitter release in a presynaptic terminal.
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Affiliation(s)
- Alessandra Sclip
- Department of Cellular and Molecular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, USA
| | - Claudio Acuna
- Department of Cellular and Molecular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, USA.,CH Schaller Foundation and Institute of Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
| | - Fujun Luo
- Department of Cellular and Molecular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, USA.,School of Life Sciences, Guangzhou University, Guangzhou, China
| | - Thomas C Südhof
- Department of Cellular and Molecular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA, USA
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23
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Xin F, Huang H, Liu P, Ren J, Zhang S, Cheng Y, Wang W. Inhibition of ZERO-BK by PKC is involved in carbachol-induced enhancement of rat colon smooth muscle motility. Neurogastroenterol Motil 2018; 30:e13312. [PMID: 29488290 DOI: 10.1111/nmo.13312] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 01/18/2018] [Indexed: 02/04/2023]
Abstract
BACKGROUND Muscarinic acetylcholine receptor (mAChR) activation is an important factor to enhance the motility of gastrointestinal (GI) smooth muscle. Large conductance Ca2+ -activated potassium (BK) channels are widely expressed in GI smooth muscle. Roles of BK in carbachol (a mAChR agonist) induced enhancement of GI motility and the molecular mechanisms remains unknown and were investigated in this study. METHODS Colonic smooth muscle (CSM) strip was perfused to record motility in vitro. The patch-clamp technique was used to record BK currents. RT-PCR was used to detect the expression of BK channels in rat CSM tissues. Two different types BK channels were constructed in HEK293 cells to investigate the regulation mechanism. Paired t tests were set with a P < .05 regarded as significant. KEY RESULTS Carbachol enhanced CSM contraction through M3 receptor (M3 R) were attenuated by IbTX, an inhibitor of BK. Carbachol inhibited BK currents in CSM cells and Go6983, an inhibitor of protein kinase C (PKC), reversed the effect. PKC activator, phorbol 12-myristate 13-acetate (PMA), inhibited BK currents. Two types of BK channels (ZERO-BK and STREX-BK) were detected in CSM. ZERO- but not STREX-BK channels expressed in HEK293 cells were inhibited by PMA. CONCLUSION Our results provide strong evidence that inhibition of ZERO-BK but not STREX-BK channels via PKC pathway is involved in the enhancement of CSM motility by mAChR activation. Besides the activation of BK by an increase in intracellular calcium, inhibition of BK played an important role in GI motility regulation during mAChR activation.
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Affiliation(s)
- F Xin
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - H Huang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - P Liu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - J Ren
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - S Zhang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - Y Cheng
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
| | - W Wang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China
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24
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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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25
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Tanner MR, Pennington MW, Chamberlain BH, Huq R, Gehrmann EJ, Laragione T, Gulko PS, Beeton C. Targeting KCa1.1 Channels with a Scorpion Venom Peptide for the Therapy of Rat Models of Rheumatoid Arthritis. J Pharmacol Exp Ther 2018; 365:227-236. [PMID: 29453198 DOI: 10.1124/jpet.117.245118] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 02/14/2018] [Indexed: 12/21/2022] Open
Abstract
Fibroblast-like synoviocytes (FLSs) are a key cell type involved in rheumatoid arthritis (RA) progression. We previously identified the KCa1.1 potassium channel (Maxi-K, BK, Slo 1, KCNMA1) as a regulator of FLSs and found that KCa1.1 inhibition reduces disease severity in RA animal models. However, systemic KCa1.1 block causes multiple side effects. In this study, we aimed to determine whether the KCa1.1 β1-3-specific venom peptide blocker iberiotoxin (IbTX) reduces disease severity in animal models of RA without inducing major side effects. We used immunohistochemistry to identify IbTX-sensitive KCa1.1 subunits in joints of rats with a model of RA. Patch-clamp and functional assays were used to determine whether IbTX can regulate FLSs through targeting KCa1.1. We then tested the efficacy of IbTX in ameliorating disease in two rat models of RA. Finally, we determined whether IbTX causes side effects including incontinence or tremors in rats, compared with those treated with the small-molecule KCa1.1 blocker paxilline. IbTX-sensitive subunits of KCa1.1 were expressed by FLSs in joints of rats with experimental arthritis. IbTX inhibited KCa1.1 channels expressed by FLSs from patients with RA and by FLSs from rat models of RA and reduced FLS invasiveness. IbTX significantly reduced disease severity in two rat models of RA. Unlike paxilline, IbTX did not induce tremors or incontinence in rats. Overall, IbTX inhibited KCa1.1 channels on FLSs and treated rat models of RA without inducing side effects associated with nonspecific KCa1.1 blockade and could become the basis for the development of a new treatment of RA.
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Affiliation(s)
- Mark R Tanner
- Department of Molecular Physiology and Biophysics (M.R.T., B.H.C., R.H., E.J.G., C.B.), Interdepartmental Graduate Program in Translational Biology and Molecular Medicine (M.R.T.), and Biology of Inflammation Center and Center for Drug Discovery (C.B.), Baylor College of Medicine, Houston, Texas; Peptides International Inc., Louisville, Kentucky (M.W.P.); and Division of Rheumatology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York (T.L., P.S.G.)
| | - Michael W Pennington
- Department of Molecular Physiology and Biophysics (M.R.T., B.H.C., R.H., E.J.G., C.B.), Interdepartmental Graduate Program in Translational Biology and Molecular Medicine (M.R.T.), and Biology of Inflammation Center and Center for Drug Discovery (C.B.), Baylor College of Medicine, Houston, Texas; Peptides International Inc., Louisville, Kentucky (M.W.P.); and Division of Rheumatology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York (T.L., P.S.G.)
| | - Brayden H Chamberlain
- Department of Molecular Physiology and Biophysics (M.R.T., B.H.C., R.H., E.J.G., C.B.), Interdepartmental Graduate Program in Translational Biology and Molecular Medicine (M.R.T.), and Biology of Inflammation Center and Center for Drug Discovery (C.B.), Baylor College of Medicine, Houston, Texas; Peptides International Inc., Louisville, Kentucky (M.W.P.); and Division of Rheumatology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York (T.L., P.S.G.)
| | - Redwan Huq
- Department of Molecular Physiology and Biophysics (M.R.T., B.H.C., R.H., E.J.G., C.B.), Interdepartmental Graduate Program in Translational Biology and Molecular Medicine (M.R.T.), and Biology of Inflammation Center and Center for Drug Discovery (C.B.), Baylor College of Medicine, Houston, Texas; Peptides International Inc., Louisville, Kentucky (M.W.P.); and Division of Rheumatology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York (T.L., P.S.G.)
| | - Elizabeth J Gehrmann
- Department of Molecular Physiology and Biophysics (M.R.T., B.H.C., R.H., E.J.G., C.B.), Interdepartmental Graduate Program in Translational Biology and Molecular Medicine (M.R.T.), and Biology of Inflammation Center and Center for Drug Discovery (C.B.), Baylor College of Medicine, Houston, Texas; Peptides International Inc., Louisville, Kentucky (M.W.P.); and Division of Rheumatology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York (T.L., P.S.G.)
| | - Teresina Laragione
- Department of Molecular Physiology and Biophysics (M.R.T., B.H.C., R.H., E.J.G., C.B.), Interdepartmental Graduate Program in Translational Biology and Molecular Medicine (M.R.T.), and Biology of Inflammation Center and Center for Drug Discovery (C.B.), Baylor College of Medicine, Houston, Texas; Peptides International Inc., Louisville, Kentucky (M.W.P.); and Division of Rheumatology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York (T.L., P.S.G.)
| | - Pércio S Gulko
- Department of Molecular Physiology and Biophysics (M.R.T., B.H.C., R.H., E.J.G., C.B.), Interdepartmental Graduate Program in Translational Biology and Molecular Medicine (M.R.T.), and Biology of Inflammation Center and Center for Drug Discovery (C.B.), Baylor College of Medicine, Houston, Texas; Peptides International Inc., Louisville, Kentucky (M.W.P.); and Division of Rheumatology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York (T.L., P.S.G.)
| | - Christine Beeton
- Department of Molecular Physiology and Biophysics (M.R.T., B.H.C., R.H., E.J.G., C.B.), Interdepartmental Graduate Program in Translational Biology and Molecular Medicine (M.R.T.), and Biology of Inflammation Center and Center for Drug Discovery (C.B.), Baylor College of Medicine, Houston, Texas; Peptides International Inc., Louisville, Kentucky (M.W.P.); and Division of Rheumatology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York (T.L., P.S.G.)
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26
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Pratt CP, Kuljis DA, Homanics GE, He J, Kolodieznyi D, Dudem S, Hollywood MA, Barth AL, Bruchez MP. Tagging of Endogenous BK Channels with a Fluorogen-Activating Peptide Reveals β4-Mediated Control of Channel Clustering in Cerebellum. Front Cell Neurosci 2017; 11:337. [PMID: 29163049 PMCID: PMC5671578 DOI: 10.3389/fncel.2017.00337] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2017] [Accepted: 10/12/2017] [Indexed: 01/10/2023] Open
Abstract
BK channels are critical regulators of neuronal activity, controlling firing, neurotransmitter release, cerebellar function, and BK channel mutations have been linked to seizure disorders. Modulation of BK channel gating is well characterized, regulated by accessory subunit interactions, intracellular signaling pathways, and membrane potential. In contrast, the role of intracellular trafficking mechanisms in controlling BK channel function, especially in live cells, has been less studied. Fluorogen-activating peptides (FAPs) are well-suited for trafficking and physiological studies due to the binding of malachite green (MG)-based dyes with sub-nanomolar affinity to the FAP, resulting in bright, photostable, far-red fluorescence. Cell-excluded MG dyes enable the selective tagging of surface protein and tracking through endocytic pathways. We used CRISPR to insert the FAP at the extracellular N-terminus of BKα in the first exon of its native locus, enabling regulation by the native promoter elements and tag incorporation into multiple splice isoforms. Motor coordination was found to be normal; however, BK channel expression seems to be reduced in some locations. Alternate start site selection or post-translational proteolytic processing resulted in incomplete FAP tagging of the BKα proteins in brain tissues. In Purkinje cell somata, FAP revealed BK channel clustering previously only observed by electron microscopy. Measurement of these clusters in β4+/- and β4-/- mice showed that puncta number and cluster fluorescence intensity on the soma are reduced in β4-/- knockout animals. This novel mouse line provides a versatile fluorescent platform for studying endogenous BK channels in living and fixed tissues. Future studies could apply this line to ex vivo neuronal cultures to study live-cell channel trafficking.
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Affiliation(s)
- Christopher P Pratt
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, United States.,Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA, United States.,Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, PA, United States
| | - Dika A Kuljis
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, United States
| | - Gregg E Homanics
- Department of Anesthesiology, University of Pittsburgh, Pittsburgh, PA, United States.,Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA, United States.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Jianjun He
- Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA, United States.,Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, United States
| | - Dmytro Kolodieznyi
- Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA, United States.,Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, United States
| | - Srikanth Dudem
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - Mark A Hollywood
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - Alison L Barth
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, United States.,Center for the Neural Basis of Cognition, Carnegie Mellon University, Pittsburgh, PA, United States
| | - Marcel P Bruchez
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, United States.,Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, PA, United States.,Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, United States
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27
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Maqoud F, Cetrone M, Mele A, Tricarico D. Molecular structure and function of big calcium-activated potassium channels in skeletal muscle: pharmacological perspectives. Physiol Genomics 2017; 49:306-317. [DOI: 10.1152/physiolgenomics.00121.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 02/08/2017] [Accepted: 04/10/2017] [Indexed: 11/22/2022] Open
Abstract
The large-conductance Ca2+-activated K+ (BK) channel is broadly expressed in various mammalian cells and tissues such as neurons, skeletal muscles (sarco-BK), and smooth muscles. These channels are activated by changes in membrane electrical potential and by increases in the concentration of intracellular calcium ion (Ca2+). The BK channel is subjected to many mechanisms that add diversity to the BK channel α-subunit gene. These channels are indeed subject to alternative splicing, auxiliary subunits modulation, posttranslational modifications, and protein-protein interactions. BK channels can be modulated by diverse molecules that may induce either an increase or decrease in channel activity. The linkage of these channels to many intracellular metabolites and pathways, as well as their modulation by extracellular natural agents, have been found to be relevant in many physiological processes. BK channel diversity is obtained by means of alternative splicing and modulatory β- and γ-subunits. The association of the α-subunit with β- or with γ-subunits can change the BK channel phenotype, functional diversity, and pharmacological properties in different tissues. In the case of the skeletal muscle BK channel (sarco-BK channel), we established that the main mechanism regulating BK channel diversity is the alternative splicing of the KCNMA1/slo1 gene encoding for the α-subunit generating different splicing isoform in the muscle phenotypes. This finding helps to design molecules selectively targeting the skeletal muscle subtypes. The use of drugs selectively targeting the skeletal muscle BK channels is a promising strategy in the treatment of familial disorders affecting muscular skeletal apparatus including hyperkalemia and hypokalemia periodic paralysis.
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Affiliation(s)
- Fatima Maqoud
- Department of Pharmacy-Drug Science, University of Bari, Bari, Italy
- Faculty of Science, Chouaib Doukkali University, El Jadida, Morocco
| | - Michela Cetrone
- Istituto Tumori Giovanni Paolo II, Istituto di Ricovero e Cura a Carattere Scientifico, National Cancer Institute, Bari, Italy; and
| | - Antonietta Mele
- Department of Pharmacy-Drug Science, University of Bari, Bari, Italy
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28
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Latorre R, Castillo K, Carrasquel-Ursulaez W, Sepulveda RV, Gonzalez-Nilo F, Gonzalez C, Alvarez O. Molecular Determinants of BK Channel Functional Diversity and Functioning. Physiol Rev 2017; 97:39-87. [DOI: 10.1152/physrev.00001.2016] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Large-conductance Ca2+- and voltage-activated K+ (BK) channels play many physiological roles ranging from the maintenance of smooth muscle tone to hearing and neurosecretion. BK channels are tetramers in which the pore-forming α subunit is coded by a single gene ( Slowpoke, KCNMA1). In this review, we first highlight the physiological importance of this ubiquitous channel, emphasizing the role that BK channels play in different channelopathies. We next discuss the modular nature of BK channel-forming protein, in which the different modules (the voltage sensor and the Ca2+ binding sites) communicate with the pore gates allosterically. In this regard, we review in detail the allosteric models proposed to explain channel activation and how the models are related to channel structure. Considering their extremely large conductance and unique selectivity to K+, we also offer an account of how these two apparently paradoxical characteristics can be understood consistently in unison, and what we have learned about the conduction system and the activation gates using ions, blockers, and toxins. Attention is paid here to the molecular nature of the voltage sensor and the Ca2+ binding sites that are located in a gating ring of known crystal structure and constituted by four COOH termini. Despite the fact that BK channels are coded by a single gene, diversity is obtained by means of alternative splicing and modulatory β and γ subunits. We finish this review by describing how the association of the α subunit with β or with γ subunits can change the BK channel phenotype and pharmacology.
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Affiliation(s)
- Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Karen Castillo
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Willy Carrasquel-Ursulaez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Romina V. Sepulveda
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Fernando Gonzalez-Nilo
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Carlos Gonzalez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Osvaldo Alvarez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
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29
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Abstract
Large conductance Ca(2+)- and voltage-activated K(+) (BK) channels are widely distributed in the postnatal central nervous system (CNS). BK channels play a pleiotropic role in regulating the activity of brain and spinal cord neural circuits by providing a negative feedback mechanism for local increases in intracellular Ca(2+) concentrations. In neurons, they regulate the timing and duration of K(+) influx such that they can either increase or decrease firing depending on the cellular context, and they can suppress neurotransmitter release from presynaptic terminals. In addition, BK channels located in astrocytes and arterial myocytes modulate cerebral blood flow. Not surprisingly, both loss and gain of BK channel function have been associated with CNS disorders such as epilepsy, ataxia, mental retardation, and chronic pain. On the other hand, the neuroprotective role played by BK channels in a number of pathological situations could potentially be leveraged to correct neurological dysfunction.
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30
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Pratt CP, He J, Wang Y, Barth AL, Bruchez MP. Fluorogenic Green-Inside Red-Outside (GIRO) Labeling Approach Reveals Adenylyl Cyclase-Dependent Control of BKα Surface Expression. Bioconjug Chem 2015; 26:1963-71. [PMID: 26301573 PMCID: PMC4576318 DOI: 10.1021/acs.bioconjchem.5b00409] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
The
regulation of surface levels of protein is critical for proper
cell function and influences properties including cell adhesion, ion
channel contributions to current flux, and the sensitivity of surface
receptors to ligands. Here we demonstrate a two-color labeling system
in live cells using a single fluorogen activating peptide (FAP) based
fusion tag, which enables the rapid and simultaneous quantification
of surface and internal proteins. In the nervous system, BK channels
can regulate neural excitability and neurotransmitter release, and
the surface trafficking of BK channels can be modulated by signaling
cascades and assembly with accessory proteins. Using this labeling
approach, we examine the dynamics of BK channel surface expression
in HEK293 cells. Surface pools of the pore-forming BKα subunit
were stable, exhibiting a plasma membrane half-life of >10 h. Long-term
activation of adenylyl cyclase by forskolin reduced BKα surface
levels by 30%, an effect that could not be attributed to increased
bulk endocytosis of plasma membrane proteins. This labeling approach
is compatible with microscopic imaging and flow cytometry, providing
a solid platform for examining protein trafficking in living cells.
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Affiliation(s)
- Christopher P Pratt
- Department of Biological Sciences, ‡Department of Chemistry, §Molecular Biosensor and Imaging Center, and #Center for the Neural Basis of Cognition, Carnegie Mellon University , 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Jianjun He
- Department of Biological Sciences, ‡Department of Chemistry, §Molecular Biosensor and Imaging Center, and #Center for the Neural Basis of Cognition, Carnegie Mellon University , 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Yi Wang
- Department of Biological Sciences, ‡Department of Chemistry, §Molecular Biosensor and Imaging Center, and #Center for the Neural Basis of Cognition, Carnegie Mellon University , 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Alison L Barth
- Department of Biological Sciences, ‡Department of Chemistry, §Molecular Biosensor and Imaging Center, and #Center for the Neural Basis of Cognition, Carnegie Mellon University , 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Marcel P Bruchez
- Department of Biological Sciences, ‡Department of Chemistry, §Molecular Biosensor and Imaging Center, and #Center for the Neural Basis of Cognition, Carnegie Mellon University , 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
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Kyle BD, Braun AP. The regulation of BK channel activity by pre- and post-translational modifications. Front Physiol 2014; 5:316. [PMID: 25202279 PMCID: PMC4141542 DOI: 10.3389/fphys.2014.00316] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 08/02/2014] [Indexed: 11/17/2022] Open
Abstract
Large conductance, Ca2+-activated K+ (BK) channels represent an important pathway for the outward flux of K+ ions from the intracellular compartment in response to membrane depolarization, and/or an elevation in cytosolic free [Ca2+]. They are functionally expressed in a range of mammalian tissues (e.g., nerve and smooth muscles), where they can either enhance or dampen membrane excitability. The diversity of BK channel activity results from the considerable alternative mRNA splicing and post-translational modification (e.g., phosphorylation) of key domains within the pore-forming α subunit of the channel complex. Most of these modifications are regulated by distinct upstream cell signaling pathways that influence the structure and/or gating properties of the holo-channel and ultimately, cellular function. The channel complex may also contain auxiliary subunits that further affect channel gating and behavior, often in a tissue-specific manner. Recent studies in human and animal models have provided strong evidence that abnormal BK channel expression/function contributes to a range of pathologies in nerve and smooth muscle. By targeting the upstream regulatory events modulating BK channel behavior, it may be possible to therapeutically intervene and alter BK channel expression/function in a beneficial manner.
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Affiliation(s)
- Barry D Kyle
- Department of Physiology and Pharmacology, Cumming School of Medicine, Libin Cardiovascular Research Institute, University of Calgary Calgary, AB, Canada
| | - Andrew P Braun
- Department of Physiology and Pharmacology, Cumming School of Medicine, Libin Cardiovascular Research Institute, University of Calgary Calgary, AB, Canada
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Large conductance Ca2+-activated K+ channel (BKCa) α-subunit splice variants in resistance arteries from rat cerebral and skeletal muscle vasculature. PLoS One 2014; 9:e98863. [PMID: 24921651 PMCID: PMC4055454 DOI: 10.1371/journal.pone.0098863] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 05/07/2014] [Indexed: 11/19/2022] Open
Abstract
Previous studies report functional differences in large conductance Ca2+ activated-K+ channels (BKCa) of smooth muscle cells (VSMC) from rat cerebral and cremaster muscle resistance arteries. The present studies aimed to determine if this complexity in BKCa activity may, in part, be due to splice variants in the pore-forming α-subunit. BKCa variants in the intracellular C terminus of the α-subunit, and their relative expression to total α-subunit, were examined by qPCR. Sequencing of RT-PCR products showed two α-subunit variants, ZERO and STREX, to be identical in cremaster and cerebral arteries. Levels of STREX mRNA expression were, however, significantly higher in cremaster VSMCs (28.9±4.2% of total α-BKCa) compared with cerebral vessels (16.5±0.9%). Further, a low level of BKCa SS4 α-subunit variant was seen in cerebral arteries, while undetectable in cremaster arteries. Protein biotinylation assays, in expression systems and arterial preparations, were used to determine whether differences in splice variant mRNA expression affect surface membrane/cytosolic location of the channel. In AD-293 and CHO-K1 cells, rat STREX was more likely to be located at the plasma membrane compared to ZERO, although the great majority of channel protein was in the membrane in both cases. Co-expression of β1-BKCa subunit with STREX or ZERO did not influence the dominant membrane expression of α-BKCa subunits, whereas in the absence of α-BKCa, a significant proportion of β1-subunit remained cytosolic. Biotinylation assays of cremaster and cerebral arteries showed that differences in STREX/ZERO expression do not alter membrane/cytosolic distribution of the channel under basal conditions. These data, however, revealed that the amount of α-BKCa in cerebral arteries is approximately 20X higher than in cremaster vessels. Thus, the data support the major functional differences in BKCa activity in cremaster, as compared to cerebral VSMCs, being related to total α-BKCa expression, regardless of differences in splice variant expression.
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Liu H, Xin T, He W, Li F, Su ZQ. Myelinated Ah-type trigeminal ganglion neurons in female rats: neuroexcitability, chemosensitivity to histamine, and potential clinical impact. Neurosci Lett 2014; 567:74-9. [PMID: 24686179 DOI: 10.1016/j.neulet.2014.03.039] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 02/19/2014] [Accepted: 03/07/2014] [Indexed: 12/14/2022]
Abstract
Migraine is a chronic neurological disorder characterized by recurrent moderate-to-severe headaches often associated with numerous autonomic nervous system symptoms, and it is more prevalent in women. To fully understand the underlying mechanism, standard electrophysiology was performed with trigeminal ganglion neurons (TGNs) isolated from adult rats of both genders using the whole-cell patch clamp technique to test the distribution, neuroexcitability, and chemosensitivity to histamine. In addition to traditionally classified A- and C-type TGNs, myelinated Ah-type TGNs were also observed in females. The electrophysiological features showed low firing threshold and the capability to fire repetitively upon stimulation. Ah-type neurons also functionally expressed persistent TTX-R Na(+) channels with more hyperpolarized activating voltage. Iberiotoxin and NS11021 significantly altered the discharge profiles of Ah-type TGNs. Finally, Ah-type TGNs showed a more potent reaction to histamine, with relatively larger inward currents and membrane depolarization compared with C-types. These data provide evidence of the gender-specific distribution of myelinated Ah-type TGNs in adult female rats, characterized by a low threshold and high frequency of firing that are at least partially attributable to persistent TTX-R Na(+) and BK-KCa channel expression and potent chemosensitivity to histamine, suggesting that Ah-type TGNs may play a key role in gender differences in migraine.
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Affiliation(s)
- Hua Liu
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China; Department of Neurology, The Fourth Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Ting Xin
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Wei He
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Fang Li
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Zhi-Qiang Su
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China.
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Large conductance calcium-activated potassium channels: their expression and modulation of glutamate release from nerve terminals isolated from rat trigeminal caudal nucleus and cerebral cortex. Neurochem Res 2014; 39:901-10. [PMID: 24667981 DOI: 10.1007/s11064-014-1287-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 03/11/2014] [Accepted: 03/14/2014] [Indexed: 12/24/2022]
Abstract
Large conductance, calcium-activated potassium channels [big potassium (BK) channel] consist of a tetramer of pore-forming α-subunit and distinct accessory β-subunits (β1-4) that modify the channel's properties. In this study, we analyzed the effects of BK channel activators and blockers on glutamate and γ-aminobutyric acid (GABA) release from synaptosomes isolated from the cerebral cortices or trigeminal caudal nuclei (TCN) of rats. Real-time polymerase chain reaction was used to characterize BK channel α and β(1-4) subunit expression in the cortex and in the trigeminal ganglia (TG), whose neurons project primary terminal afferents into the TCN. Immunocytochemistry was used to localize these subunits on cortical and TCN synaptosomes. The BK channels regulating [(3)H]D-aspartate release from primary afferent nerve terminals projecting into the TCN displayed limited sensitivity to iberiotoxin, whereas those expressed on cortical synaptosomes were highly sensitive to this toxin. BK channels did not appear to be present on GABAergic nerve terminals from the TCN since [(3)H]-γ-aminobutyric acid release in this model was unaffected by BK channel activators or blockers. Gene expression studies revealed expression levels of the α subunit in the TG that were only 31.2 ± 2.1% of those found in cortical tissues. The β4 subunit was the accessory subunit expressed most abundantly in both the cortex and TG. Levels of β1 and β2 were low in both these areas although β2 expression in the TG was higher than that found in the cortex. Immunocytochemistry experiments showed that co-localization of α and β4 subunits (the accessory subunit most abundantly expressed in both brain areas) was more common in TCN synaptosomes than in cortical synaptosomes. On the basis of these findings, it is reasonable to hypothesize that BK channels expressed on glutamatergic terminals in the TCN and cortex have distinct pharmacological profiles, which probably reflect different α and β subunit combinations. Channels in the cortex seem to be composed mainly of α subunits and to a lesser degree by α and β4 subunits, whereas in the TG the α + β4 combination seems to prevail (although α and/or α + β2 channels cannot be excluded). In light of the BK channels' selective control of excitatory transmission and their pharmacological diversity, their effects on primary glutamatergic afferents projecting to TCN represent a potential target for drug therapy of migraines and other types of orofacial pain.
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Bosch Calero C, Selga E, Brugada R, Scornik FS, Pérez GJ. The smooth muscle-type β1 subunit potentiates activation by DiBAC4(3) in recombinant BK channels. Channels (Austin) 2013; 8:95-102. [PMID: 24299688 DOI: 10.4161/chan.27212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Large-conductance Ca(2+)-activated (BK) channels, expressed in a variety of tissues, play a fundamental role in regulating and maintaining arterial tone. We recently demonstrated that the slow voltage indicator DiBAC4(3) does not depend, as initially proposed, on the β 1 or β 4 subunits to activate native arterial smooth muscle BK channels. Using recombinant mslo BK channels, we now show that the β 1 subunit is not essential to this activation but exerts a large potentiating effect. DiBAC4(3) promotes concentration-dependent activation of BK channels and slows deactivation kinetics, changes that are independent of Ca(2+). Kd values for BK channel activation by DiBAC4(3) in 0 mM Ca(2+) are approximately 20 μM (α) and 5 μM (α+β 1), and G-V curves shift up to -40 mV and -110 mV, respectively. β1 to β2 mutations R11A and C18E do not interfere with the potentiating effect of the subunit. Our findings should help refine the role of the β 1 subunit in cardiovascular pharmacology.
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Affiliation(s)
- Cristina Bosch Calero
- Cardiovascular Genetics Center; Institut d'Investigació Biomèdica de Girona (IDIBGI) and School of Medicine; University of Girona (UdG); Girona, Spain
| | - Elisabet Selga
- Cardiovascular Genetics Center; Institut d'Investigació Biomèdica de Girona (IDIBGI) and School of Medicine; University of Girona (UdG); Girona, Spain
| | - Ramon Brugada
- Cardiovascular Genetics Center; Institut d'Investigació Biomèdica de Girona (IDIBGI) and School of Medicine; University of Girona (UdG); Girona, Spain
| | - Fabiana S Scornik
- Cardiovascular Genetics Center; Institut d'Investigació Biomèdica de Girona (IDIBGI) and School of Medicine; University of Girona (UdG); Girona, Spain
| | - Guillermo J Pérez
- Cardiovascular Genetics Center; Institut d'Investigació Biomèdica de Girona (IDIBGI) and School of Medicine; University of Girona (UdG); Girona, Spain
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36
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Takahashi K, Naruse K. Stretch-activated BK channel and heart function. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2013; 110:239-44. [PMID: 23281538 DOI: 10.1016/j.pbiomolbio.2012.08.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The heart is an organ that is exposed to extreme dynamic mechanical stimuli. From birth till death, the heart indefinitely repeats periodic contraction and dilation, i.e., shortening and elongation of cardiomyocytes. Mechanical stretch elicits a change in heart rate and may cause arrhythmia if it is excessive. Thus, mechanosensitivity is crucial to heart function. The molecule that is substantially involved in mechanosensitivity is a stretch-activated ion channel. Among several ion channels believed to be activated by stretch in the heart, the stretch-activated KCa (SAKCA) channel, a member of the group of large conductance (Big Potassium, BK) channels, shows a mechanosensitive (MS) response to membrane stretch. As BK channels respond to voltage and intracellular calcium concentration with large conductance, they are considered to be involved in repolarization after depolarization. Some BK channels are known to be activated by stretch and are expressed in a number of cells, including human osteoblasts and guinea pig intestinal neurons. The SAKCA channel was found to be sensitive to stretch in the chick heart. Given that the cardiomyocyte is unremittingly exposed to contraction and dilation and that it generates action potential and its contractility is modulated by intracellular calcium concentration, the SAKCA channel, which is dependent voltage and calcium, may be involved in action potential generation. It was recently reported that a BK channel is involved in the modulation of heart rate in the mouse. Further studies regarding the role of MS BK channels, including SAKCA, in the modulation of heart rate and contractility are expected.
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Affiliation(s)
- Ken Takahashi
- Department of Cardiovascular Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
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37
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The interface between membrane-spanning and cytosolic domains in Ca²+-dependent K+ channels is involved in β subunit modulation of gating. J Neurosci 2013; 33:11253-61. [PMID: 23825428 DOI: 10.1523/jneurosci.0620-13.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Large-conductance, voltage-, and Ca²⁺-dependent K⁺ (BK) channels are broadly expressed in various tissues to modulate neuronal activity, smooth muscle contraction, and secretion. BK channel activation depends on the interactions among the voltage sensing domain (VSD), the cytosolic domain (CTD), and the pore gate domain (PGD) of the Slo1 α-subunit, and is further regulated by accessory β subunits (β1-β4). How β subunits fine-tune BK channel activation is critical to understand the tissue-specific functions of BK channels. Multiple sites in both Slo1 and the β subunits have been identified to contribute to the interaction between Slo1 and the β subunits. However, it is unclear whether and how the interdomain interactions among the VSD, CTD, and PGD are altered by the β subunits to affect channel activation. Here we show that human β1 and β2 subunits alter interactions between bound Mg²⁺ and gating charge R213 and disrupt the disulfide bond formation at the VSD-CTD interface of mouse Slo1, indicating that the β subunits alter the VSD-CTD interface. Reciprocally, mutations in the Slo1 that alter the VSD-CTD interaction can specifically change the effects of the β1 subunit on the Ca²⁺ activation and of the β2 subunit on the voltage activation. Together, our data suggest a novel mechanism by which the β subunits modulated BK channel activation such that a β subunit may interact with the VSD or the CTD and alter the VSD-CTD interface of the Slo1, which enables the β subunit to have effects broadly on both voltage and Ca²⁺-dependent activation.
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38
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Selga E, Pérez-Serra A, Moreno-Asso A, Anderson S, Thomas K, Desai M, Brugada R, Pérez GJ, Scornik FS. Molecular heterogeneity of large-conductance calcium-activated potassium channels in canine intracardiac ganglia. Channels (Austin) 2013; 7:322-8. [PMID: 23807090 PMCID: PMC3989361 DOI: 10.4161/chan.25485] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Large conductance calcium-activated potassium (BK) channels are widely expressed in the nervous system. We have recently shown that principal neurons from canine intracardiac ganglia (ICG) express a paxilline- and TEA-sensitive BK current, which increases neuronal excitability. In the present work, we further explore the molecular constituents of the BK current in canine ICG. We found that the β1 and β4 regulatory subunits are expressed in ICG. Single channel voltage-dependence at different calcium concentrations suggested that association of the BKα with a particular β subunit was not enough to explain the channel activity in this tissue. Indeed, we detected the presence of several splice variants of the BKα subunit. In conclusion, BK channels in canine ICG may result from the arrangement of different BKα splice variants, plus accessory β subunits. The particular combinations expressed in canine IC neurons likely rule the excitatory role of BK current in this tissue.
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Affiliation(s)
- Elisabet Selga
- Cardiovascular Genetics Center; Institut d'Investigació Biomèdica de Girona (IdIBGi); Department of Medical Sciences; School of Medicine; University of Girona (UdG); Girona, Spain
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39
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Scornik FS, Bucciero RS, Wu Y, Selga E, Bosch Calero C, Brugada R, Pérez GJ. DiBAC₄(3) hits a "sweet spot" for the activation of arterial large-conductance Ca²⁺-activated potassium channels independently of the β₁-subunit. Am J Physiol Heart Circ Physiol 2013; 304:H1471-82. [PMID: 23542916 DOI: 10.1152/ajpheart.00939.2012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The voltage-sensitive dye bis-(1,3-dibutylbarbituric acid)trimethine oxonol [DiBAC₄(3)] has been reported as a novel large-conductance Ca²⁺-activated K⁺ (BK) channel activator with selectivity for its β₁- or β₄-subunits. In arterial smooth muscle, BK channels are formed by a pore-forming α-subunit and a smooth muscle-abundant regulatory β₁-subunit. This tissue specificity has driven extensive pharmacological research aimed at regulating arterial tone. Using animals with a disruption of the gene for the β₁-subunit, we explored the effects of DiBAC₄(3) in native channels from arterial smooth muscle. We tested the hypothesis that, in native BK channels, activation by DiBAC₄(3) relies mostly on its α-subunit. We studied BK channels from wild-type and transgenic β₁-knockout mice in excised patches. BK channels from brain arteries, with or without the β₁-subunit, were similarly activated by DiBAC₄(3). In addition, we found that saturating concentrations of DiBAC₄(3) (~30 μM) promote an unprecedented persistent activation of the channel that negatively shifts its voltage dependence by as much as -300 mV. This "sweet spot" for persistent activation is independent of Ca²⁺ and/or the β₁₋₄-subunits and is fully achieved when DiBAC₄(3) is applied to the intracellular side of the channel. Arterial BK channel response to DiBAC₄(3) varies across species and/or vascular beds. DiBAC₄(3) unique effects can reveal details of BK channel gating mechanisms and help in the rational design of BK channel activators.
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Affiliation(s)
- Fabiana S Scornik
- Cardiovascular Genetics Center, Institut de Investigació Biomèdica de Girona, and Department of Medical Sciences, School of Medicine, University of Girona, Girona, Spain
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40
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Zhang J, Halm ST, Halm DR. Role of the BK channel (KCa1.1) during activation of electrogenic K+ secretion in guinea pig distal colon. Am J Physiol Gastrointest Liver Physiol 2012; 303:G1322-34. [PMID: 23064759 PMCID: PMC3532550 DOI: 10.1152/ajpgi.00325.2012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Secretagogues acting at a variety of receptor types activate electrogenic K(+) secretion in guinea pig distal colon, often accompanied by Cl(-) secretion. Distinct blockers of K(Ca)1.1 (BK, Kcnma1), iberiotoxin (IbTx), and paxilline inhibited the negative short-circuit current (I(sc)) associated with K(+) secretion. Mucosal addition of IbTx inhibited epinephrine-activated I(sc) ((epi)I(sc)) and transepithelial conductance ((epi)G(t)) consistent with K(+) secretion occurring via apical membrane K(Ca)1.1. The concentration dependence of IbTx inhibition of (epi)I(sc) yielded an IC(50) of 193 nM, with a maximal inhibition of 51%. Similarly, IbTx inhibited (epi)G(t) with an IC(50) of 220 nM and maximal inhibition of 48%. Mucosally added paxilline (10 μM) inhibited (epi)I(sc) and (epi)G(t) by ∼50%. IbTx and paxilline also inhibited I(sc) activated by mucosal ATP, supporting apical K(Ca)1.1 as a requirement for this K(+) secretagogue. Responses to IbTx and paxilline indicated that a component of K(+) secretion occurred during activation of Cl(-) secretion by prostaglandin-E(2) and cholinergic stimulation. Analysis of K(Ca)1.1α mRNA expression in distal colonic epithelial cells indicated the presence of the ZERO splice variant and three splice variants for the COOH terminus. The presence of the regulatory β-subunits K(Ca)β1 and K(Ca)β4 also was demonstrated. Immunolocalization supported the presence of K(Ca)1.1α in apical and basolateral membranes of surface and crypt cells. Together these results support a cellular mechanism for electrogenic K(+) secretion involving apical membrane K(Ca)1.1 during activation by several secretagogue types, but the observed K(+) secretion likely required the activity of additional K(+) channel types in the apical membrane.
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Affiliation(s)
- Jin Zhang
- Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine, Dayton, Ohio
| | - Susan T. Halm
- Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine, Dayton, Ohio
| | - Dan R. Halm
- Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine, Dayton, Ohio
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41
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Kamp MA, Dibué M, Schneider T, Steiger HJ, Hänggi D. Calcium and potassium channels in experimental subarachnoid hemorrhage and transient global ischemia. Stroke Res Treat 2012; 2012:382146. [PMID: 23251831 PMCID: PMC3518967 DOI: 10.1155/2012/382146] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 10/27/2012] [Indexed: 11/23/2022] Open
Abstract
Healthy cerebrovascular myocytes express members of several different ion channel families which regulate resting membrane potential, vascular diameter, and vascular tone and are involved in cerebral autoregulation. In animal models, in response to subarachnoid blood, a dynamic transition of ion channel expression and function is initiated, with acute and long-term effects differing from each other. Initial hypoperfusion after exposure of cerebral vessels to oxyhemoglobin correlates with a suppression of voltage-gated potassium channel activity, whereas delayed cerebral vasospasm involves changes in other potassium channel and voltage-gated calcium channels expression and function. Furthermore, expression patterns and function of ion channels appear to differ between main and small peripheral vessels, which may be key in understanding mechanisms behind subarachnoid hemorrhage-induced vasospasm. Here, changes in calcium and potassium channel expression and function in animal models of subarachnoid hemorrhage and transient global ischemia are systematically reviewed and their clinical significance discussed.
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Affiliation(s)
- Marcel A. Kamp
- Department for Neurosurgery, Medical Faculty, Heinrich Heine University, Moorenstraße 5, 40225 Düsseldorf, Germany
- Institute for Neurophysiology, University of Cologne, Robert-Koch-Straße 39, 50931 Cologne, Germany
| | - Maxine Dibué
- Department for Neurosurgery, Medical Faculty, Heinrich Heine University, Moorenstraße 5, 40225 Düsseldorf, Germany
- Institute for Neurophysiology, University of Cologne, Robert-Koch-Straße 39, 50931 Cologne, Germany
- Center of Molecular Medicine, Cologne, Germany
| | - Toni Schneider
- Institute for Neurophysiology, University of Cologne, Robert-Koch-Straße 39, 50931 Cologne, Germany
- Center of Molecular Medicine, Cologne, Germany
| | - Hans-Jakob Steiger
- Department for Neurosurgery, Medical Faculty, Heinrich Heine University, Moorenstraße 5, 40225 Düsseldorf, Germany
| | - Daniel Hänggi
- Department for Neurosurgery, Medical Faculty, Heinrich Heine University, Moorenstraße 5, 40225 Düsseldorf, Germany
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Scheff NN, Gold MS. Sex differences in the inflammatory mediator-induced sensitization of dural afferents. J Neurophysiol 2011; 106:1662-8. [PMID: 21753025 DOI: 10.1152/jn.00196.2011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Approximately 20% of the adult population suffers from migraine. This debilitating pain disorder is three times more prevalent in women than in men. To begin to evaluate the underlying mechanisms that may contribute to this sex difference, we tested the hypothesis that there is a sex difference in the inflammatory mediator (IM)-induced sensitization of dural afferents. Acutely dissociated retrogradely labeled dural afferents from adult Sprague-Dawley rats were examined with whole cell patch-clamp recordings. Baseline passive and active electrophysiological properties of dural afferents from both sexes were comparable. However, while IM-induced increases in the excitability of dural afferents from male and female rats were also comparable, the proportion of dural afferents from female rats sensitized by IM (~100%) was significantly greater than that of dural afferents from male rats (~50%). This appeared to be due to differences downstream of IM receptors, as tetrodotoxin-resistant sodium current was increased by IM in a majority of male dural afferents (13/14). These data indicate that there are both quantitative and qualitative differences in the IM-induced sensitization of dural afferents that may contribute to the sex difference in the manifestation of migraine.
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Affiliation(s)
- N N Scheff
- The Center for Neuroscience at the University of Pittsburgh, PA 15213, USA
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Wang W, Huang H, Hou D, Liu P, Wei H, Fu X, Niu W. Mechanosensitivity of STREX-lacking BKCa channels in the colonic smooth muscle of the mouse. Am J Physiol Gastrointest Liver Physiol 2010; 299:G1231-40. [PMID: 20864656 DOI: 10.1152/ajpgi.00268.2010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Stretch sensitivity of Ca²(+)-activated large-conductance K(+) channels (BK(Ca)) has been observed in a variety of cell types and considered to be a potential mechanism in mechanoelectric transduction (MET). Mechanical stress is a major stimulator for the smooth muscle in the gastrointestinal (GI) tract. However, much about the role and mechanism of MET in GI smooth muscles remains unknown. The BK(Ca) shows a functional diversity due to intensive Slo I alternative splicing and different α/β-subunit assembly in various cells. The stress-regulated exon (STREX) insert is suggested to be an indispensable domain for the mechanosensitivity of BK(Ca). The purpose of this study was to determine whether the BK(Ca) in colonic myocytes of the adult mouse is sensitive to mechanical stimulation and whether the STREX insert is a crucial segment for the BK(Ca) mechanosensitivity. The α- and β1-subunit mRNAs and the α-subunit protein of the BK(Ca) channels were detected in the colonic muscularis. We found that the BK(Ca) STREX-lacking variant was abundantly expressed in the smooth muscle, whereas the STREX variant was not detectable. We demonstrated that the STREX-lacking BK(Ca) channels were also sensitive to membrane stretch. We suggest that in addition to the STREX domain, there are other additional structures in the channel responsible for mechanically coupling with the cell membrane.
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Affiliation(s)
- Wei Wang
- Dept. of Physiology, Capital Medical Univ., Beijing, PR China
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Poulsen AN, Jansen-Olesen I, Olesen J, Klaerke DA. Neuronal fast activating and meningeal silent modulatory BK channel splice variants cloned from rat. Pflugers Arch 2010; 461:65-75. [PMID: 20938677 DOI: 10.1007/s00424-010-0887-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 09/20/2010] [Accepted: 09/23/2010] [Indexed: 12/25/2022]
Abstract
The big conductance calcium-activated K(+) channel (BK) is involved in regulating neuron and smooth muscle cell excitability. Functional diversity of BK is generated by alpha-subunit splice variation and co-expression with beta subunits. Here, we present six different splice combinations cloned from rat brain or cerebral vascular/meningeal tissues, of which at least three variants were previously uncharacterized (X1, X2(92), and X2(188)). An additional variant was identified by polymerase chain reaction but not cloned. Expression in Xenopus oocytes showed that the brain-specific X1 variant displays reduced current, faster activation, and less voltage sensitivity than the insert-less Zero variant. Other cloned variants Strex and Slo27,3 showed slower activation than Zero. The X1 variant contains sequence inserts in the S1-S2 extracellular loop (8 aa), between intracellular domains RCK1 and RCK2 (4 aa at SS1) and upstream of the calcium "bowl" (27 aa at SS4). Two other truncated variants, X2(92) and X2(188), lacking the intracellular C-terminal (stop downstream of S6), were cloned from cerebral vascular/meningeal tissue. They appear non-functional as no current expression was observed, but the X2(92) appeared to slow the activation of the Zero variant when co-expressed. Positive protein expression of X2(92) was observed in oocytes by immunoblotting and fluorescence using a yellow fluorescent protein-tagged construct. The functional characteristics of the X1 variant may be important for a subpopulation of BK channels in the brain, while the "silent" truncated variants X2(92) and X2(188) may play a role as modulators of other BK channel variants in a way similar to well known beta subunits.
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Affiliation(s)
- Asser Nyander Poulsen
- Department of Animal and Veterinary Basic Sciences, Faculty of Life Sciences, University of Copenhagen, Groennegaardsvej 7, Frederiksberg C, Denmark.
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Abstract
The control of force production in vascular smooth muscle is critical to the normal regulation of blood flow and pressure, and altered regulation is common to diseases such as hypertension, heart failure, and ischemia. A great deal has been learned about imbalances in vasoconstrictor and vasodilator signals, e.g., angiotensin, endothelin, norepinephrine, and nitric oxide, that regulate vascular tone in normal and disease contexts. In contrast there has been limited study of how the phenotypic state of the vascular smooth muscle cell may influence the contractile response to these signaling pathways dependent upon the developmental, tissue-specific (vascular bed) or disease context. Smooth, skeletal, and cardiac muscle lineages are traditionally classified into fast or slow sublineages based on rates of contraction and relaxation, recognizing that this simple dichotomy vastly underrepresents muscle phenotypic diversity. A great deal has been learned about developmental specification of the striated muscle sublineages and their phenotypic interconversions in the mature animal under the control of mechanical load, neural input, and hormones. In contrast there has been relatively limited study of smooth muscle contractile phenotypic diversity. This is surprising given the number of diseases in which smooth muscle contractile dysfunction plays a key role. This review focuses on smooth muscle contractile phenotypic diversity in the vascular system, how it is generated, and how it may determine vascular function in developmental and disease contexts.
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Affiliation(s)
- Steven A Fisher
- Department of Medicine, and Cardiovascular Research Institute, Case Western Reserve University, Cleveland, Ohio 44106-7290, USA.
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Kim JM, Beyer R, Morales M, Chen S, Liu LQ, Duncan RK. Expression of BK-type calcium-activated potassium channel splice variants during chick cochlear development. J Comp Neurol 2010; 518:2554-69. [PMID: 20503427 DOI: 10.1002/cne.22352] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The appearance of large-conductance, calcium-activated potassium (BK) current is a hallmark of functional maturation in auditory hair cells. Acquisition of this fast-activating current enables high-frequency, graded receptor potentials in all vertebrates and an electrical tuning mechanism in nonmammals. The gene encoding BK alpha subunits is highly alternatively spliced, and the resulting variations in channel isoforms may contribute to functional diversity at the onset of hearing. We examined the tissue specificity of nine BK alpha alternative exons and investigated changes in expression during chick cochlear development using quantitative polymerase chain reaction (qPCR). Each alternative was widely expressed in several tissues except for an insert near the C-terminus Ca(2+) sensing domain, which appeared brain-specific. The only alternative form in the membrane-bound core of the channel was expressed in brain and muscle but was undetected in cochlea. Of the remaining variants, three increased in expression prior to the onset of hearing and acquisition of BK currents. These three variants cause decreased Ca(2+) sensitivity or increased intracellular retention, traits that would not easily explain the advent of calcium-sensitive currents at embryonic day (E)18-19. Expression levels of other variants were mature and stable by E15, days before currents were acquired. Surface expression of C-terminal isoforms was examined using patch-clamp electrophysiology and immunocytochemistry. C-terminal variants that exhibit robust surface expression appeared in the membrane at E18, even though transcripts were unchanged during development starting from E12. These results indicate that delays in protein synthesis and trafficking/scaffolding of channel subunits underlie the late acquisition of BK currents in cochlear hair cells.
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Affiliation(s)
- Jung-Min Kim
- Kresge Hearing Research Institute, University of Michigan, Ann Arbor, Michigan 48109, USA
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Vang A, Mazer J, Casserly B, Choudhary G. Activation of endothelial BKCa channels causes pulmonary vasodilation. Vascul Pharmacol 2010; 53:122-9. [PMID: 20470901 DOI: 10.1016/j.vph.2010.05.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 04/28/2010] [Accepted: 05/06/2010] [Indexed: 12/21/2022]
Abstract
BACKGROUND Large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels cause hyperpolarization and can regulate vascular tone. In this study, we evaluated the effect of endothelial BK(Ca) activation on pulmonary vascular tone. METHODS The presence of BK(Ca) channels in lung microvascular endothelial cells (LMVEC) and rat lung tissue was confirmed by RT-PCR, immunoblotting and immunohistochemistry. Isolated pulmonary artery (PA) rings and isolated ventilated-perfused rat lungs were used to assay the effects of BK(Ca) channel activation on endothelium-dependent vasodilation. RESULTS Immunoblotting and RT-PCR revealed the presence of BK(Ca) channel alpha- and beta(4)-subunits in LMVEC. Immunohistochemical staining showed BK(Ca) channel alpha-subunit expression in vascular endothelium in rat lungs. In arterial ring studies, BK(Ca) channel activation by NS1619 enhanced endothelium-dependent vasodilation that was attenuated by tetraethylammonium and iberiotoxin. In addition, activation of BK(Ca) channels by C-type natriuretic peptide caused endothelial-dependent vasodilation that was blocked by iberiotoxin, L-NAME, and lanthanum. Furthermore, BK(Ca) activation by NS1619 caused a dose-dependent reduction in PA pressures that was attenuated by L-NAME. In vitro, BK(Ca) channel activation in LMVEC caused hyperpolarization and increased NO production. CONCLUSIONS Pulmonary endothelium expresses BK(Ca) channels. Activation of endothelial BK(Ca) channels causes hyperpolarization and NO mediated endothelium-dependent vasodilation in micro- and macrovasculature in the lung.
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Affiliation(s)
- Alexander Vang
- Vascular Research Laboratory, Providence VA Medical Center, Providence, RI 02908, USA
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Localization of large conductance calcium-activated potassium channels and their effect on calcitonin gene-related peptide release in the rat trigemino-neuronal pathway. Neuroscience 2010; 167:1091-102. [PMID: 20211697 DOI: 10.1016/j.neuroscience.2010.02.063] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 02/09/2010] [Accepted: 02/23/2010] [Indexed: 11/24/2022]
Abstract
Large conductance calcium-activated potassium (BK(Ca)) channels are membrane proteins contributing to electrical propagation through neurons. Calcitonin gene-related peptide (CGRP) is a neuropeptide found in the trigeminovascular system (TGVS). Both BK(Ca) channels and CGRP are involved in migraine pathophysiology. Here we study the expression and localization of BK(Ca) channels and CGRP in the rat trigeminal ganglion (TG) and the trigeminal nucleus caudalis (TNC) as these structures are involved in migraine pain. Also the effect of the BK(Ca) channel blocker iberiotoxin and the BK(Ca) channel opener NS11021 on CGRP release from isolated TG and TNC was investigated. By RT-PCR, BK(Ca) channel mRNA was detected in the TG and the TNC. A significant difference in BK(Ca) channel mRNA transcript levels were found using qPCR between the TNC as compared to the TG. The BK(Ca) channel protein was more expressed in the TNC as compared to the TG shown by western blotting. Immunohistochemistry identified BK(Ca) channels in the nerve cell bodies of the TG and the TNC. The beta2- and beta4-subunit proteins were found in the TG and the TNC. They were both more expressed in the TNC as compared to TG shown by western blotting. In isolated TNC, the BK(Ca) channel blocker iberiotoxin induced a concentration-dependent release of CGRP that was attenuated by the BK(Ca) channel opener NS11021. No effect on basal CGRP release was found by NS11021 in isolated TG or TNC or by iberiotoxin in TG. In conclusion, we found both BK(Ca) channel mRNA and protein expression in the TG and the TNC. The BK(Ca) channel protein and the modulatory beta2- and beta4-subunt proteins were more expressed in the TNC than in the TG. Iberiotoxin induced an increase in CGRP release from the TNC that was attenuated by NS11021. Thus, BK(Ca) channels might have a role in trigeminovascular pain transmission.
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Kita M, Yunoki T, Takimoto K, Miyazato M, Kita K, de Groat WC, Kakizaki H, Yoshimura N. Effects of bladder outlet obstruction on properties of Ca2+-activated K+ channels in rat bladder. Am J Physiol Regul Integr Comp Physiol 2010; 298:R1310-9. [PMID: 20200132 DOI: 10.1152/ajpregu.00523.2009] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In this study, we investigated the effects of bladder outlet obstruction (BOO) on the expression and function of large conductance (BK) and small conductance (SK) Ca(2+)-activated K(+) channels in detrusor smooth muscle. The bladder from adult female Sprague-Dawley rats with 6-wk BOO were used. The mRNA expression of the BK channel alpha-subunit, beta1-, beta2-, and beta4-subunits and SK1, SK2, and SK3 channels were investigated using real-time RT-PCR. All subunits except for the BK-beta2, SK2, and SK3 channels were predominantly expressed in the detrusor smooth muscle rather than in the mucosa. The mRNA expression of the BK channel alpha-subunit was not significantly changed in obstructed bladders. However, the expression of the BK channel beta1-subunit and the SK3 channel was remarkably increased in obstructed bladders. On the other hand, the expression of the BK channel beta4-subunit was decreased as the severity of BOO-induced bladder overactivity progressed. In detrusor smooth muscle strips from obstructed bladders, blockade of BK channels by iberiotoxin (IbTx) or charybdotoxin (CTx) and blockade of SK channels by apamin increased the amplitude of spontaneous contractions. These blockers also increased the contractility and affinity of these strips for carbachol during cumulative applications. The facilitatory effects elicited by these K(+) channel blockers were larger in the strips from obstructed bladders compared with control bladders. These results suggest that long-term exposure to BOO for 6 wk enhances the function of both BK and SK types of Ca(2+)-activated K(+) channels in the detrusor smooth muscle to induce an inhibition of bladder contractility, which might be a compensatory mechanism to reduce BOO-induced bladder overactivity.
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Affiliation(s)
- Masafumi Kita
- Department of Urology, University of Pittsburgh School of Medicine, 3471 Fifth Ave., Pittsburgh, PA 15213, USA.
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Hill MA, Yang Y, Ella SR, Davis MJ, Braun AP. Large conductance, Ca2+-activated K+ channels (BKCa) and arteriolar myogenic signaling. FEBS Lett 2010; 584:2033-42. [PMID: 20178789 DOI: 10.1016/j.febslet.2010.02.045] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2009] [Accepted: 02/15/2010] [Indexed: 12/22/2022]
Abstract
Myogenic, or pressure-induced, vasoconstriction is critical for local blood flow autoregulation. Underlying this vascular smooth muscle (VSM) response are events including membrane depolarization, Ca(2+) entry and mobilization, and activation of contractile proteins. Large conductance, Ca(2+)-activated K(+) channel (BK(Ca)) has been implicated in several of these steps including, (1) channel closure causing membrane depolarization, and (2) channel opening causing hyperpolarization to oppose excessive pressure-induced vasoconstriction. As multiple mechanisms regulate BK(Ca) activity (subunit composition, membrane potential (Em) and Ca(2+) levels, post-translational modification) tissue level diversity is predicted. Importantly, heterogeneity in BK(Ca) channel activity may contribute to tissue-specific differences in regulation of myogenic vasoconstriction, allowing local hemodynamics to be matched to metabolic requirements. Knowledge of such variability will be important to exploiting the BK(Ca) channel as a therapeutic target and understanding systemic effects of its pharmacological manipulation.
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Affiliation(s)
- Michael A Hill
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, USA.
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