1
|
Vaithianathan T, Schneider EH, Bukiya AN, Dopico AM. Cholesterol and PIP 2 Modulation of BK Ca Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1422:217-243. [PMID: 36988883 PMCID: PMC10683925 DOI: 10.1007/978-3-031-21547-6_8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Ca2+/voltage-gated, large conductance K+ channels (BKCa) are formed by homotetrameric association of α (slo1) subunits. Their activity, however, is suited to tissue-specific physiology largely due to their association with regulatory subunits (β and γ types), chaperone proteins, localized signaling, and the channel's lipid microenvironment. PIP2 and cholesterol can modulate BKCa activity independently of downstream signaling, yet activating Ca2+i levels and regulatory subunits control ligand action. At physiological Ca2+i and voltages, cholesterol and PIP2 reduce and increase slo1 channel activity, respectively. Moreover, slo1 proteins provide sites that seem to recognize cholesterol and PIP2: seven CRAC motifs in the slo1 cytosolic tail and a string of positively charged residues (Arg329, Lys330, Lys331) immediately after S6, respectively. A model that could explain the modulation of BKCa activity by cholesterol and/or PIP2 is hypothesized. The roles of additional sites, whether in slo1 or BKCa regulatory subunits, for PIP2 and/or cholesterol to modulate BKCa function are also discussed.
Collapse
Affiliation(s)
- Thirumalini Vaithianathan
- Department Pharmacology, Addiction Science, and Toxicology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, USA
| | - Elizabeth H Schneider
- Department Pharmacology, Addiction Science, and Toxicology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, USA
| | - Anna N Bukiya
- Department Pharmacology, Addiction Science, and Toxicology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, USA
| | - Alex M Dopico
- Department Pharmacology, Addiction Science, and Toxicology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, USA.
| |
Collapse
|
2
|
Qi XL, Jo H, Wang XY, Ji TT, Lin HX, Park CS, Cui YM. Synthesis and BK channel-opening activity of 2-amino-1,3-thiazole derivatives. Bioorg Med Chem Lett 2021; 43:128083. [PMID: 33964448 DOI: 10.1016/j.bmcl.2021.128083] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/23/2021] [Accepted: 05/01/2021] [Indexed: 11/28/2022]
Abstract
A series of 2-amino-5-arylmethyl- or 5-heteroarylmethyl-1,3-thiazole derivatives were synthesized and evaluated for BK channel-opening activities in cell-based fluorescence assay and electrophysiological recording. The assay results indicated that the activities of the investigated compounds were influenced by the physicochemical properties of the substituent at benzene ring.
Collapse
Affiliation(s)
- Xiao-Lei Qi
- Department of Chemistry, Innovative Drug Research Center, College of Sciences, Shanghai University, Shanghai 200444, China
| | - Heeji Jo
- School of Life Sciences and National Leading Research Laboratory, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea
| | - Xue-Ying Wang
- Department of Chemistry, Innovative Drug Research Center, College of Sciences, Shanghai University, Shanghai 200444, China
| | - Tong-Tong Ji
- Department of Chemistry, Innovative Drug Research Center, College of Sciences, Shanghai University, Shanghai 200444, China
| | - Hai-Xia Lin
- Department of Chemistry, Innovative Drug Research Center, College of Sciences, Shanghai University, Shanghai 200444, China
| | - Chul-Seung Park
- School of Life Sciences and National Leading Research Laboratory, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea.
| | - Yong-Mei Cui
- Department of Chemistry, Innovative Drug Research Center, College of Sciences, Shanghai University, Shanghai 200444, China.
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
Łukasiak A, Skup A, Chlopicki S, Łomnicka M, Kaczara P, Proniewski B, Szewczyk A, Wrzosek A. SERCA, complex I of the respiratory chain and ATP-synthase inhibition are involved in pleiotropic effects of NS1619 on endothelial cells. Eur J Pharmacol 2016; 786:137-147. [PMID: 27262382 DOI: 10.1016/j.ejphar.2016.05.039] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 05/17/2016] [Accepted: 05/30/2016] [Indexed: 01/10/2023]
Abstract
A large conductance potassium (BKCa) channel opener, NS1619 (1,3-dihydro-1- [2-hydroxy-5-(trifluoromethyl) phenyl]-5-(trifluoromethyl)-2H-benzimidazole-2-one), is well known for its protective effects against ischemia-reperfusion injury; however, the exact mode of its action remains unclear. The aim of this study was to characterize the effect of NS1619 on endothelial cells. The endothelial cell line EA.hy926, guinea pig hearts and submitochondrial particles isolated from the heart were used. In the isolated guinea pig hearts, which were perfused using the Langendorff technique, NS1619 caused a dose-dependent increase in coronary flow that was inhibited by L-NAME. In EA.hy926 cells, NS1619 also caused a dose-dependent increase in the intracellular calcium ion concentration [Ca(2+)]i, as measured using the FURA-2 fluorescent probe. Moreover, NS1619 decreased the oxygen consumption rate in EA.hy926 cells, as assessed using a Clark-type oxygen electrode. However, when NS1619 was applied in the presence of oligomycin, the oxygen consumption increased. NS1619 also decreased the mitochondrial membrane potential, as measured using a JC-1 fluorescent probe in the presence and absence of oligomycin. Additionally, the application of NS1619 to submitochondrial particles inhibited ATP synthase. In summary, NS1619 has pleiotropic actions on EA.hy926 cells and acts not only as an opener of the BKCa channel in EA.hy926 cells but also as an inhibitor of the respiratory chain component, sarcoplasmic reticulum ATPase, which leads to the release of Ca(2+) from the endoplasmic reticulum. Furthermore, NS1619 has the oligomycin-like property of inhibiting mitochondrial ATP synthase.
Collapse
Affiliation(s)
- Agnieszka Łukasiak
- Department of Biophysics, Warsaw University of Life Sciences SGGW, 159 Nowoursynowska St., 02-776 Warsaw, Poland.
| | - Agata Skup
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteura St., 02-093 Warsaw, Poland
| | - Stefan Chlopicki
- Jagiellonian Centre for Experimental Therapeutics (JCET), Jagiellonian University, 14 Bobrzynskiego St., 30-348 Krakow, Poland; Chair of Pharmacology, Jagiellonian University, Medical College, 16 Grzegorzecka, 31-531 Krakow, Poland
| | - Magdalena Łomnicka
- Chair of Pharmacology, Jagiellonian University, Medical College, 16 Grzegorzecka, 31-531 Krakow, Poland
| | - Patrycja Kaczara
- Jagiellonian Centre for Experimental Therapeutics (JCET), Jagiellonian University, 14 Bobrzynskiego St., 30-348 Krakow, Poland
| | - Bartosz Proniewski
- Jagiellonian Centre for Experimental Therapeutics (JCET), Jagiellonian University, 14 Bobrzynskiego St., 30-348 Krakow, Poland
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteura St., 02-093 Warsaw, Poland
| | - Antoni Wrzosek
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteura St., 02-093 Warsaw, Poland
| |
Collapse
|
5
|
Geng Y, Magleby KL. Single-channel kinetics of BK (Slo1) channels. Front Physiol 2015; 5:532. [PMID: 25653620 PMCID: PMC4300911 DOI: 10.3389/fphys.2014.00532] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 12/31/2014] [Indexed: 11/16/2022] Open
Abstract
Single-channel kinetics has proven a powerful tool to reveal information about the gating mechanisms that control the opening and closing of ion channels. This introductory review focuses on the gating of large conductance Ca2+- and voltage-activated K+ (BK or Slo1) channels at the single-channel level. It starts with single-channel current records and progresses to presentation and analysis of single-channel data and the development of gating mechanisms in terms of discrete state Markov (DSM) models. The DSM models are formulated in terms of the tetrameric modular structure of BK channels, consisting of a central transmembrane pore-gate domain (PGD) attached to four surrounding transmembrane voltage sensing domains (VSD) and a large intracellular cytosolic domain (CTD), also referred to as the gating ring. The modular structure and data analysis shows that the Ca2+ and voltage dependent gating considered separately can each be approximated by 10-state two-tiered models with five closed states on the upper tier and five open states on the lower tier. The modular structure and joint Ca2+ and voltage dependent gating are consistent with a 50 state two-tiered model with 25 closed states on the upper tier and 25 open states on the lower tier. Adding an additional tier of brief closed (flicker states) to the 10-state or 50-state models improved the description of the gating. For fixed experimental conditions a channel would gate in only a subset of the potential number of states. The detected number of states and the correlations between adjacent interval durations are consistent with the tiered models. The examined models can account for the single-channel kinetics and the bursting behavior of gating. Ca2+ and voltage activate BK channels by predominantly increasing the effective opening rate of the channel with a smaller decrease in the effective closing rate. Ca2+ and depolarization thus activate by mainly destabilizing the closed states.
Collapse
Affiliation(s)
- Yanyan Geng
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine Miami, FL, USA
| | - Karl L Magleby
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine Miami, FL, USA ; Neuroscience Program, University of Miami Miller School of Medicine Miami, FL, USA
| |
Collapse
|
6
|
Smith FJ, Pau VP, Cingolani G, Rothberg BS. Structural basis of allosteric interactions among Ca2+-binding sites in a K+ channel RCK domain. Nat Commun 2013; 4:2621. [DOI: 10.1038/ncomms3621] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 09/16/2013] [Indexed: 12/24/2022] Open
|
7
|
Geng Y, Wang X, Magleby KL. Lack of negative slope in I-V plots for BK channels at positive potentials in the absence of intracellular blockers. ACTA ACUST UNITED AC 2013; 141:493-7. [PMID: 23530138 PMCID: PMC3607821 DOI: 10.1085/jgp.201210955] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Large-conductance, voltage- and Ca(2+)-activated K(+) (BK) channels display near linear current-voltage (I-V) plots for voltages between -100 and +100 mV, with an increasing sublinearity for more positive potentials. As is the case for many types of channels, BK channels are blocked at positive potentials by intracellular Ca(2+) and Mg(2+). This fast block progressively reduces single-channel conductance with increasing voltage, giving rise to a negative slope in the I-V plots beyond about +120 mV, depending on the concentration of the blockers. In contrast to these observations of pronounced differences in the magnitudes and shapes of I-V plots in the absence and presence of intracellular blockers, Schroeder and Hansen (2007. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.200709802) have reported identical I-V plots in the absence and presence of blockers for BK channels, with both plots having reduced conductance and negative slopes, as expected for blockers. Schroeder and Hansen included both Ca(2+) and Mg(2+) in the intracellular solution rather than a single blocker, and they also studied BK channels expressed from α plus β1 subunits, whereas most previous studies used only α subunits. Although it seems unlikely that these experimental differences would account for the differences in findings between previous studies and those of Schroeder and Hansen, we repeated the experiments using BK channels comprised of α plus β1 subunits with joint application of 2.5 mM Ca(2+) plus 2.5 mM Mg(2+), as Schroeder and Hansen did. In contrast to the findings of Schroeder and Hansen of identical I-V plots, we found marked differences in the single-channel I-V plots in the absence and presence of blockers. Consistent with previous studies, we found near linear I-V plots in the absence of blockers and greatly reduced currents and negative slopes in the presence of blockers. Hence, studies of conductance mechanisms for BK channels should exclude intracellular Ca(2+)/Mg(2+), as they can reduce conductance and induce negative slopes.
Collapse
Affiliation(s)
- Yanyan Geng
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
| | | | | |
Collapse
|
8
|
Shen M, Zhao L, Wu RX, Yue SQ, Pei JM. The vasorelaxing effect of resveratrol on abdominal aorta from rats and its underlying mechanisms. Vascul Pharmacol 2013; 58:64-70. [DOI: 10.1016/j.vph.2012.07.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2012] [Revised: 06/18/2012] [Accepted: 07/11/2012] [Indexed: 11/28/2022]
|
9
|
Rothberg BS. The BK channel: a vital link between cellular calcium and electrical signaling. Protein Cell 2012; 3:883-92. [PMID: 22996175 PMCID: PMC4875380 DOI: 10.1007/s13238-012-2076-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Accepted: 08/23/2012] [Indexed: 10/27/2022] Open
Abstract
Large-conductance Ca²⁺-activated K⁺ channels (BK channels) constitute an key physiological link between cellular Ca²⁺ signaling and electrical signaling at the plasma membrane. Thus these channels are critical to the control of action potential firing and neurotransmitter release in several types of neurons, as well as the dynamic control of smooth muscle tone in resistance arteries, airway, and bladder. Recent advances in our understanding of K⁺ channel structure and function have led to new insight toward the molecular mechanisms of opening and closing (gating) of these channels. Here we will focus on mechanisms of BK channel gating by Ca²⁺, transmembrane voltage, and auxiliary subunit proteins.
Collapse
Affiliation(s)
- Brad S Rothberg
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA.
| |
Collapse
|
10
|
Large conductance, calcium- and voltage-gated potassium (BK) channels: regulation by cholesterol. Pharmacol Ther 2012; 135:133-50. [PMID: 22584144 DOI: 10.1016/j.pharmthera.2012.05.002] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 04/09/2012] [Indexed: 11/21/2022]
Abstract
Cholesterol (CLR) is an essential component of eukaryotic plasma membranes. CLR regulates the membrane physical state, microdomain formation and the activity of membrane-spanning proteins, including ion channels. Large conductance, voltage- and Ca²⁺-gated K⁺ (BK) channels link membrane potential to cell Ca²⁺ homeostasis. Thus, they control many physiological processes and participate in pathophysiological mechanisms leading to human disease. Because plasmalemma BK channels cluster in CLR-rich membrane microdomains, a major driving force for studying BK channel-CLR interactions is determining how membrane CLR controls the BK current phenotype, including its pharmacology, channel sorting, distribution, and role in cell physiology. Since both BK channels and CLR tissue levels play a pathophysiological role in human disease, identifying functional and structural aspects of the CLR-BK channel interaction may open new avenues for therapeutic intervention. Here, we review the studies documenting membrane CLR-BK channel interactions, dissecting out the many factors that determine the final BK current response to changes in membrane CLR content. We also summarize work in reductionist systems where recombinant BK protein is studied in artificial lipid bilayers, which documents a direct inhibition of BK channel activity by CLR and builds a strong case for a direct interaction between CLR and the BK channel-forming protein. Bilayer lipid-mediated mechanisms in CLR action are also discussed. Finally, we review studies of BK channel function during hypercholesterolemia, and underscore the many consequences that the CLR-BK channel interaction brings to cell physiology and human disease.
Collapse
|
11
|
Singh AK, McMillan J, Bukiya AN, Burton B, Parrill AL, Dopico AM. Multiple cholesterol recognition/interaction amino acid consensus (CRAC) motifs in cytosolic C tail of Slo1 subunit determine cholesterol sensitivity of Ca2+- and voltage-gated K+ (BK) channels. J Biol Chem 2012; 287:20509-21. [PMID: 22474334 DOI: 10.1074/jbc.m112.356261] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Large conductance, Ca(2+)- and voltage-gated K(+) (BK) channel proteins are ubiquitously expressed in cell membranes and control a wide variety of biological processes. Membrane cholesterol regulates the activity of membrane-associated proteins, including BK channels. Cholesterol modulation of BK channels alters action potential firing, colonic ion transport, smooth muscle contractility, endothelial function, and the channel alcohol response. The structural bases underlying cholesterol-BK channel interaction are unknown. Such interaction is determined by strict chemical requirements for the sterol molecule, suggesting cholesterol recognition by a protein surface. Here, we demonstrate that cholesterol action on BK channel-forming Cbv1 proteins is mediated by their cytosolic C tail domain, where we identified seven cholesterol recognition/interaction amino acid consensus motifs (CRAC4 to 10), a distinct feature of BK proteins. Cholesterol sensitivity is provided by the membrane-adjacent CRAC4, where Val-444, Tyr-450, and Lys-453 are required for cholesterol sensing, with hydrogen bonding and hydrophobic interactions participating in cholesterol location and recognition. However, cumulative truncations or Tyr-to-Phe substitutions in CRAC5 to 10 progressively blunt cholesterol sensitivity, documenting involvement of multiple CRACs in cholesterol-BK channel interaction. In conclusion, our study provides for the first time the structural bases of BK channel cholesterol sensitivity; the presence of membrane-adjacent CRAC4 and the long cytosolic C tail domain with several other CRAC motifs, which are not found in other members of the TM6 superfamily of ion channels, very likely explains the unique cholesterol sensitivity of BK channels.
Collapse
Affiliation(s)
- Aditya K Singh
- Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
| | | | | | | | | | | |
Collapse
|
12
|
Vaithianathan T, Narayanan D, Asuncion-Chin MT, Jeyakumar LH, Liu J, Fleischer S, Jaggar JH, Dopico AM. Subtype identification and functional characterization of ryanodine receptors in rat cerebral artery myocytes. Am J Physiol Cell Physiol 2010; 299:C264-78. [PMID: 20445169 PMCID: PMC2928634 DOI: 10.1152/ajpcell.00318.2009] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Accepted: 05/04/2010] [Indexed: 11/22/2022]
Abstract
Ryanodine receptors (RyRs) regulate contractility in resistance-size cerebral artery smooth muscle, yet their molecular identity, subcellular location, and phenotype in this tissue remain unknown. Following rat resistance-size cerebral artery myocyte sarcoplasmic reticulum (SR) purification and incorporation into POPE-POPS-POPC (5:3:2; wt/wt) bilayers, unitary conductances of 110 +/- 8, 334 +/- 15, and 441 +/- 27 pS in symmetric 300 mM Cs(+) were usually detected. The most frequent (34/40 bilayers) conductance (334 pS) decreased to
Collapse
Affiliation(s)
- Thirumalini Vaithianathan
- Department Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
| | | | | | | | | | | | | | | |
Collapse
|
13
|
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.
Collapse
Affiliation(s)
- Alexander Vang
- Vascular Research Laboratory, Providence VA Medical Center, Providence, RI 02908, USA
| | | | | | | |
Collapse
|
14
|
Liang CF, Au ALS, Leung SWS, Ng KFJ, Félétou M, Kwan YW, Man RYK, Vanhoutte PM. Endothelium-derived nitric oxide inhibits the relaxation of the porcine coronary artery to natriuretic peptides by desensitizing big conductance calcium-activated potassium channels of vascular smooth muscle. J Pharmacol Exp Ther 2010; 334:223-31. [PMID: 20332186 DOI: 10.1124/jpet.110.166652] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The present experiments investigated whether endothelium-derived mediators modulate the effect of natriuretic peptides in porcine coronary arteries. Rings with and without endothelium were suspended in organ chambers for isometric tension recording. Concentration-relaxation curves to C-type natriuretic peptide (CNP) and atrial natriuretic peptide (ANP) were obtained during contractions to endothelin-1. Removal of the endothelium potentiated relaxations to both CNP and ANP. N(omega)-nitro-L-arginine methyl ester potentiated relaxations to natriuretic peptides only in arteries with endothelium. Sodium nitroprusside (SNP) inhibited the response to the natriuretic peptides only in the absence of the endothelium. In rings with endothelium, 1H-[1,2,4]oxadiazolo [4,3-a]quinoxalin-1-one (ODQ) and 4H-8-bromo-1,2,4-oxadiazolo[3,4-d]benz[b][1,4]oxazin-1-one (NS2028) potentiated CNP-mediated relaxations. Iberiotoxin (IBTX) reduced the response only in rings without endothelium. Glybenclamide inhibited the relaxations in both the presence and absence of endothelium. CNP-induced relaxations were reduced by 8-bromoguanosine 3',5'-cGMP (8-bromo-cGMP) to the same extent in rings with and without endothelium. There was no significant difference between the increased cGMP content caused by CNP in porcine coronary arteries with or without endothelium. In patch-clamp studies in porcine coronary arterial smooth muscle cells, the natriuretic peptide-mediated enhancement of the IBTX-sensitive big conductance calcium-activated potassium channel (BK(Ca)) amplitude was reversed by SNP and 8-bromo-cGMP. These findings demonstrate that, in the porcine coronary artery, the opening of BK(Ca) and ATP-dependent potassium channels of the vascular smooth muscle contributes to CNP-mediated relaxations. Endothelium-derived and exogenous NO inhibit the direct relaxing effect of natriuretic peptides by desensitizing the response of the BK(Ca)s of the vascular smooth muscle to the generation of cGMP.
Collapse
Affiliation(s)
- Chao Fan Liang
- Department of Pharmacology and Pharmacy, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, China
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Abstract
Large conductance, Ca(2+)-activated potassium (BK) channels are widely expressed throughout the animal kingdom and play important roles in many physiological processes, such as muscle contraction, neural transmission and hearing. These physiological roles derive from the ability of BK channels to be synergistically activated by membrane voltage, intracellular Ca(2+) and other ligands. Similar to voltage-gated K(+) channels, BK channels possess a pore-gate domain (S5-S6 transmembrane segments) and a voltage-sensor domain (S1-S4). In addition, BK channels contain a large cytoplasmic C-terminal domain that serves as the primary ligand sensor. The voltage sensor and the ligand sensor allosterically control K(+) flux through the pore-gate domain in response to various stimuli, thereby linking cellular metabolism and membrane excitability. This review summarizes the current understanding of these structural domains and their mutual interactions in voltage-, Ca(2+)- and Mg(2+)-dependent activation of the channel.
Collapse
Affiliation(s)
- J Cui
- Department of Biomedical Engineering and Cardiac Bioelectricity and Arrhythmia Center, Washington University, 1 Brookings Drive, St. Louis, Missouri 63130, USA.
| | | | | |
Collapse
|
16
|
Parfenova LV, Abarca-Heidemann K, Crane BM, Rothberg BS. Molecular architecture and divalent cation activation of TvoK, a prokaryotic potassium channel. J Biol Chem 2007; 282:24302-9. [PMID: 17588939 PMCID: PMC4259576 DOI: 10.1074/jbc.m703650200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
RCK (regulator of conductance of potassium) domains form a family of ligand-binding domains found in many prokaryotic K+ channels and transport proteins. Although many RCK domains contain an apparent nucleotide binding motif, some are known instead to bind Ca2+, which can then facilitate channel opening. Here we report on the molecular architecture and ligand activation properties of an RCK-containing potassium channel cloned from the prokaryote Thermoplasma volcanium. This channel, called TvoK, is of an apparent molecular mass and subunit composition that is consistent with the hetero-octameric configuration hypothesized for the related MthK (Methanobacterium thermoautotrophicum potassium) channel, in which four channel-tethered RCK domains coassemble with four soluble (untethered) RCK domains. The expression of soluble TvoK RCK subunits arises from an unconventional UUG start codon within the TvoK gene; silent mutagenesis of this alternative start codon abolishes expression of the soluble form of the TvoK RCK domain. Using single channel recording of purified, reconstituted TvoK, we found that the channel is activated by Ca2+ as well as Mg2+, Mn2+, and Ni2+. This non-selective divalent activation is in contrast with the activation properties of MthK, which is selectively activated by Ca2+. Transplantation of the TvoK RCK domain into MthK generates a channel that can be activated by Mg2+, illustrating that the Mg2+ binding site is likely contained within the RCK domain. We present a working hypothesis for TvoK gating in which the binding of either Ca2+ or Mg2+ can contribute approximately 5 kcal/mol toward stabilization of the open conformation of the channel.
Collapse
Affiliation(s)
- Lyubov V Parfenova
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229, USA
| | | | | | | |
Collapse
|
17
|
Peers C, Wyatt CN. The role of maxiK channels in carotid body chemotransduction. Respir Physiol Neurobiol 2006; 157:75-82. [PMID: 17157084 DOI: 10.1016/j.resp.2006.10.010] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2006] [Revised: 10/27/2006] [Accepted: 10/28/2006] [Indexed: 01/10/2023]
Abstract
MaxiK channels are a unique class of K(+) channels activated by both voltage and intracellular Ca(2+). Derived from a single gene, their diversity arises from extensive splicing, and their wide distribution has led to their implication in a large variety of cellular functions. In the carotid body, they have been proposed to contribute to the resting membrane potential of type I cells, and also to be O(2) sensitive. Thus, they have been suggested to have an important role in hypoxic chemotransduction. Their O(2) sensitivity is preserved when the channels are expressed in HEK 293 cells, permitting detailed studies of candidate mechanisms underlying hypoxic inhibition of maxiK channels. In this article, we review evidence for and against an important role for maxiK channels in chemotransduction. We also consider different mechanisms proposed to account for hypoxic channel inhibition and suggest that, although our understanding of this important physiological process has advanced significantly in recent years, there remain important, unanswered questions as to the importance of maxiK in carotid body chemoreception.
Collapse
Affiliation(s)
- Chris Peers
- School of Medicine, University of Leeds, Leeds, UK.
| | | |
Collapse
|
18
|
Shah VN, Chagot B, Chazin WJ. Calcium-Dependent Regulation of Ion Channels. CALCIUM BINDING PROTEINS 2006; 1:203-212. [PMID: 28757812 PMCID: PMC5531595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Calcium plays an important role in regulating hundreds of biological processes due to its primary role as one of the most ubiquitous second messengers. As a result, the levels of calcium are tightly regulated as are the peak and trough calcium concentrations during a calcium signal. Calcium levels are controlled via a variety of feedback mechanisms and exchangers/transporters. Here the role of calcium in the feedback regulation of ion channel function is reviewed, with an emphasis on the molecular mechanisms governing calcium-dependent function. In particular, the role of calcium in the regulation of voltage-gated sodium, calcium, and potassium channels are reviewed as well as its effects on the ryanodine receptor.
Collapse
Affiliation(s)
| | | | - Walter J. Chazin
- Correspondence to: Walter J. Chazin; Vanderbilt University; Center for Structural Biology; 5140 BIOSCI/Medical Research Building III; Nashville, Tennessee 37232-8725 USA; Tel.: 615.936.2210; Fax: 615.936.2211;
| |
Collapse
|
19
|
Wei AD, Gutman GA, Aldrich R, Chandy KG, Grissmer S, Wulff H. International Union of Pharmacology. LII. Nomenclature and Molecular Relationships of Calcium-Activated Potassium Channels. Pharmacol Rev 2005; 57:463-72. [PMID: 16382103 DOI: 10.1124/pr.57.4.9] [Citation(s) in RCA: 269] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Affiliation(s)
- Aguan D Wei
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | | | | | | | | | | |
Collapse
|