1
|
Lee N, Kim S, Lee NY, Jo H, Jeong P, Pagire HS, Pagire SH, Ahn JH, Jin MS, Park CS. Activation mechanism and novel binding sites of the BK Ca channel activator CTIBD. Life Sci Alliance 2024; 7:e202402621. [PMID: 39089879 PMCID: PMC11294680 DOI: 10.26508/lsa.202402621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 07/12/2024] [Accepted: 07/15/2024] [Indexed: 08/04/2024] Open
Abstract
The large-conductance calcium-activated potassium (BKCa) channel, which is crucial for urinary bladder smooth muscle relaxation, is a potential target for overactive bladder treatment. Our prior work unveiled CTIBD as a promising BKCa channel activator, altering V 1/2 and G max This study investigates CTIBD's activation mechanism, revealing its independence from the Ca2+ and membrane voltage sensing of the BKCa channel. Cryo-electron microscopy disclosed that two CTIBD molecules bind to hydrophobic regions on the extracellular side of the lipid bilayer. Key residues (W22, W203, and F266) are important for CTIBD binding, and their replacement with alanine reduces CTIBD-mediated channel activation. The triple-mutant (W22A/W203A/F266A) channel showed the smallest V 1/2 shift with a minimal impact on activation and deactivation kinetics by CTIBD. At the single-channel level, CTIBD treatment was much less effective at increasing P o in the triple mutant, mainly because of a drastically increased dissociation rate compared with the WT. These findings highlight CTIBD's mechanism, offering crucial insights for developing small-molecule treatments for BKCa-related pathophysiological conditions.
Collapse
Affiliation(s)
- Narasaem Lee
- https://ror.org/024kbgz78 School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Subin Kim
- https://ror.org/024kbgz78 School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Na Young Lee
- https://ror.org/024kbgz78 School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Heeji Jo
- https://ror.org/024kbgz78 School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | | | - Haushabhau S Pagire
- https://ror.org/024kbgz78 Department of Chemistry, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Suvarna H Pagire
- https://ror.org/024kbgz78 Department of Chemistry, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Jin Hee Ahn
- https://ror.org/024kbgz78 Department of Chemistry, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Mi Sun Jin
- https://ror.org/024kbgz78 School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Chul-Seung Park
- https://ror.org/024kbgz78 School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| |
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
de Morais Campos R, Lima LMALL, da Silva AG, Santiago RO, Paz IA, Cabral PHB, Santos CF, Fonteles MC, do Nascimento NRF. Rutin ameliorates nitrergic and endothelial dysfunction on vessels and corpora cavernosa of diabetic animals. Res Vet Sci 2023; 161:163-172. [PMID: 37406575 DOI: 10.1016/j.rvsc.2023.06.020] [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: 12/03/2021] [Revised: 06/19/2023] [Accepted: 06/23/2023] [Indexed: 07/07/2023]
Abstract
Endothelial dysfunction is an early complication of diabetes and it is related to both micro- and macroangiopathies. In addition, >70% of diabetic patients develop autonomic neuropathies. Increased oxidative stress has a major role in the development of both nitrergic and endothelial dysfunction. The aim of this work is to evaluate whether rutin, a potent antioxidant, could ameliorate nitrergic and/or endothelial dysfunction in diabetic animals. Primary and secondary treatment protocols with rutin were investigated on rat aortic rings and the mesenteric arteriolar bed, and on rabbit aortic rings and corpora cavernosa (RbCC) from both euglycemic and alloxan-diabetic animals. Acetylcholine endothelium-dependent and sodium nitroprusside endothelium-independent relaxations were compared in tissues from euglycemic or diabetic animals. Electrical field stimulation (EFS)-induced relaxation was performed only in the RbCC. Endothelial-dependent relaxations were blunted by 40% in vessels and neuronal relaxation was blunted by 50% in RbCC taken from diabetic animals when compared to euglycemic animals. Pre-treatment with rutin restored both neuronal and endothelial dependent relaxations in diabetic animals towards the values achieved in control euglycemic tissues. Rutin was able to ameliorate both endothelial dysfunction and nitrergic neuropathy in animal experimental models. Rutin could be a lead compound in the primary or secondary preventive ancillary treatment of endothelial and nitrergic dysfunction in the course of diabetes.
Collapse
Affiliation(s)
| | | | - Ariana Gomes da Silva
- Superior Institute of Biomedical Sciences, Ceará State University, Fortaleza, Ceará, Brazil
| | | | - Iury Araújo Paz
- Superior Institute of Biomedical Sciences, Ceará State University, Fortaleza, Ceará, Brazil
| | | | | | | | | |
Collapse
|
4
|
Ca 2+-Sensitive Potassium Channels. MOLECULES (BASEL, SWITZERLAND) 2023; 28:molecules28020885. [PMID: 36677942 PMCID: PMC9861210 DOI: 10.3390/molecules28020885] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/07/2023] [Accepted: 01/10/2023] [Indexed: 01/18/2023]
Abstract
The Ca2+ ion is used ubiquitously as an intracellular signaling molecule due to its high external and low internal concentration. Many Ca2+-sensing ion channel proteins have evolved to receive and propagate Ca2+ signals. Among them are the Ca2+-activated potassium channels, a large family of potassium channels activated by rises in cytosolic calcium in response to Ca2+ influx via Ca2+-permeable channels that open during the action potential or Ca2+ release from the endoplasmic reticulum. The Ca2+ sensitivity of these channels allows internal Ca2+ to regulate the electrical activity of the cell membrane. Activating these potassium channels controls many physiological processes, from the firing properties of neurons to the control of transmitter release. This review will discuss what is understood about the Ca2+ sensitivity of the two best-studied groups of Ca2+-sensitive potassium channels: large-conductance Ca2+-activated K+ channels, KCa1.1, and small/intermediate-conductance Ca2+-activated K+ channels, KCa2.x/KCa3.1.
Collapse
|
5
|
Lim XR, Drumm BT, Sergeant GP, Hollywood MA, Thornbury KD. Ca 2+ -activated Cl - channels (TMEM16A) underlie spontaneous electrical activity in isolated mouse corpus cavernosum smooth muscle cells. Physiol Rep 2022; 10:e15504. [PMID: 36394209 PMCID: PMC9669617 DOI: 10.14814/phy2.15504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 10/17/2022] [Indexed: 11/18/2022] Open
Abstract
Penile detumescence is maintained by tonic contraction of corpus cavernosum smooth muscle cells (CCSMC), but the underlying mechanisms have not been fully elucidated. The purpose of this study was to characterize the mechanisms underlying activation of TMEM16A Ca2+ -activated Cl- channels in freshly isolated murine CCSMC. Male C57BL/6 mice aged 10-18 weeks were euthanized via intraperitoneal injection of sodium pentobarbital (100 mg.kg-1 ). Whole-cell patch clamp, pharmacological, and immunocytochemical experiments were performed on isolated CCSM. Tension measurements were performed in whole tissue. TMEM16A expression in murine corpus cavernosum was confirmed using immunocytochemistry. Isolated CCSMC developed spontaneous transient inward currents (STICs) under voltage clamp and spontaneous transient depolarizations (STDs) in current clamp mode of the whole cell, perforated patch clamp technique. STICs reversed close to the predicted Cl- equilibrium potential and both STICs and STDs were blocked by the TMEM16A channel blockers, Ani9 and CaCC(inh)-A01. These events were also blocked by GSK7975A (ORAI inhibitor), cyclopiazonic acid (CPA, sarcoplasmic reticulum [SR] Ca2+- ATPase blocker), tetracaine (RyR blocker), and 2APB (IP3 R blocker), suggesting that they were dependent on Ca2+ release from intracellular Ca2+ stores. Nifedipine (L-type Ca2+ channel blocker) did not affect STICs, but reduced the duration of STDs. Phenylephrine induced transient depolarizations and transient inward currents which were blocked by Ani9. Similarly, phenylephrine induced phasic contractions of intact corpus cavernosum muscle strips and these events were also inhibited by Ani9. This study suggests that contraction of CCSM is regulated by activation of TMEM16A channels and therefore inhibition of these channels could lead to penile erection.
Collapse
Affiliation(s)
- Xin Rui Lim
- Smooth Muscle Research CentreDundalk Institute of TechnologyDublinIreland
| | - Bernard T. Drumm
- Smooth Muscle Research CentreDundalk Institute of TechnologyDublinIreland
| | - Gerard P. Sergeant
- Smooth Muscle Research CentreDundalk Institute of TechnologyDublinIreland
| | - Mark A. Hollywood
- Smooth Muscle Research CentreDundalk Institute of TechnologyDublinIreland
| | - Keith D. Thornbury
- Smooth Muscle Research CentreDundalk Institute of TechnologyDublinIreland
| |
Collapse
|
6
|
Slayden AV, Dyer CL, Ma D, Li W, Bukiya AN, Parrill AL, Dopico AM. Discovery of agonist-antagonist pairs for the modulation of Ca [2]+ and voltage-gated K + channels of large conductance that contain beta1 subunits. Bioorg Med Chem 2022; 68:116876. [PMID: 35716586 PMCID: PMC10464842 DOI: 10.1016/j.bmc.2022.116876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/31/2022] [Accepted: 06/03/2022] [Indexed: 11/02/2022]
Abstract
Large conductance, calcium/voltage-gated potassium channels (BK) regulate critical body processes, including neuronal, secretory and smooth muscle (SM) function. While BK-forming alpha subunits are ubiquitous, accessory beta1 subunits are highly expressed in SM. This makes beta1 an attractive target for pharmaceutical development to treat SM disorders, such as hypertension or cerebrovascular spasm. Compounds activating BK via beta1 have been identified, yet they exhibit low potency and off-target effects while antagonists that limit agonist activity via beta 1 remain unexplored. Beta1-dependent BK ligand-based pharmacophore modeling and ZINC database searches identified 15 commercially available hits. Concentration-response curves on BK alpha + beta1 subunit-mediated currents were obtained in CHO cells. One potent (EC50 = 20 nM) and highly efficacious activator (maximal activation = ×10.3 of control) was identified along with a potent antagonist (KB = 3.02 nM), both of which were dependent on beta1. Our study provides the first proof-of-principle that an agonist/antagonist pair can be used to control beta1-containing BK activity.
Collapse
Affiliation(s)
- Alexandria V Slayden
- Department of Pharmacology, Addiction Science and Toxicology, College of Medicine, The University of Tennessee Health Science Center, Memphis TN, 38103, USA
| | - Christy L Dyer
- Department of Chemistry, The University of Memphis, Memphis TN, 38152, USA
| | - Dejian Ma
- Department of Pharmaceutical Sciences, College of Pharmacy, The University of Tennessee Health Science Center, Memphis TN, 38163, USA
| | - Wei Li
- Department of Pharmaceutical Sciences, College of Pharmacy, The University of Tennessee Health Science Center, Memphis TN, 38163, USA
| | - Anna N Bukiya
- Department of Pharmacology, Addiction Science and Toxicology, College of Medicine, The University of Tennessee Health Science Center, Memphis TN, 38103, USA
| | - Abby L Parrill
- Department of Chemistry, The University of Memphis, Memphis TN, 38152, USA
| | - Alex M Dopico
- Department of Pharmacology, Addiction Science and Toxicology, College of Medicine, The University of Tennessee Health Science Center, Memphis TN, 38103, USA.
| |
Collapse
|
7
|
Zhao W, Sun J, Yao LY, Hang D, Li YQ, Chen CP, Zhou YW, Chen X, Tao T, Wei LS, Zheng YY, Ge X, Li CJ, Xin ZC, Pan Y, Wang XZ, He WQ, Zhang XN, Yao B, Zhu MS. MYPT1 reduction is a pathogenic factor of erectile dysfunction. Commun Biol 2022; 5:744. [PMID: 35879418 PMCID: PMC9314386 DOI: 10.1038/s42003-022-03716-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 07/14/2022] [Indexed: 11/09/2022] Open
Abstract
Erectile dysfunction (ED) is closely associated with smooth muscle dysfunction, but its underlying mechanisms remains incompletely understood. We here reported that the reduced expression of myosin phosphatase target subunit 1 (MYPT1), the main regulatory unit of myosin light chain phosphatase, was critical for the development of vasculogenic ED. Male MYPT1 knockout mice had reduced fertility and the penises displayed impaired erections as evidenced by reduced intracavernous pressure (ICP). The penile smooth muscles of the knockout mice displayed enhanced response to G-Protein Couple Receptor agonism and depolarization contractility and resistant relaxation. We further identified a natural compound lotusine that increased the MYPT1 expression by inhibiting SIAH1/2 E3 ligases-mediated protein degradation. This compound sufficiently restored the ICP and improved histological characters of the penile artery of Mypt1 haploinsufficiency mice. In diabetic ED mice (db/db), the decreased expression of MYPT1 was measured, and ICP was improved by lotusine treatment. We conclude that the reduction of MYPT1 is the major pathogenic factor of vasculogenic ED. The restoration of MYPT1 by lotusine improved the function of injured penile smooth muscles, and could be a novel strategy for ED therapy.
Collapse
Affiliation(s)
- Wei Zhao
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China
| | - Jie Sun
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China
| | - Liang-Yu Yao
- Department of Urology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Dong Hang
- Department of Epidemiology and Biostatistics, School of Public Health, Nanjing Medical University, Nanjing, China
| | - Ye-Qiong Li
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China
| | - Cai-Ping Chen
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, China
| | - Yu-Wei Zhou
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China
| | - Xin Chen
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China
| | - Tao Tao
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China
| | - Li-Sha Wei
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China
| | - Yan-Yan Zheng
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China
| | - Xie Ge
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China
| | - Chao-Jun Li
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China
| | - Zhong-Cheng Xin
- Andrology Center, Peking University First Hospital, Peking University, Beijing, China
| | - Yang Pan
- School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Xin-Zhu Wang
- School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Wei-Qi He
- Cambridge-Suda (CAM-SU) Genomic Resource Center, Soochow University, Suzhou, China
| | - Xue-Na Zhang
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China.
| | - Bing Yao
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China.
| | - Min-Sheng Zhu
- Jinling Hospital Department of Reproductive Medical Center affiliated Sch Med, State Key Laboratory of Pharmaceutical Biotechnology and Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China.
| |
Collapse
|
8
|
Comerma-Steffensen S, Prat-Duran J, Mogensen S, Fais R, Pinilla E, Simonsen U. Erectile Dysfunction and Altered Contribution of KCa1.1 and KCa2.3 Channels in the Penile Tissue of Type-2 Diabetic db/db Mice. J Sex Med 2022; 19:697-710. [PMID: 37057569 DOI: 10.1016/j.jsxm.2022.02.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 01/15/2022] [Accepted: 02/19/2022] [Indexed: 11/17/2022]
Abstract
BACKGROUND Activation of endothelial small conductance calcium-activated K+ channels (KCa2.3) and intermediate conductance calcium-activated K+ channels (KCa3.1) leads to vascular relaxation. We found endothelial KCa2.3 down-regulation in the corpus cavernosum diminishes erectile function. AIM We hypothesized that in type-2 diabetic mice, the function of KCa2.3 and KCa1.1 channels is impaired in erectile tissue. METHODS Erectile function was measured, and corpus cavernosum strips were mounted for functional studies and processed for qPCR and immunoblotting. OUTCOMES Effects of type 2 diabetes on erectile function, expression and function of calcium-activated potassium channels. RESULTS In anesthetized diabetic db/db mice, erectile function was markedly decreased compared to non-diabetic heterozygous db/+ mice, and the impairment was even more pronounced compared to normal C57BL/6 mice. qPCR revealed KCa2.3 and KCa1.1α channel expressions were upregulated in corpus cavernosum from db/db mice. Immunoblotting showed down-regulation of KCa2.3 channels in the corpus cavernosum from db/db mice. Acetylcholine relaxations were impaired while relaxations induced by the nitric oxide, donor SNP were unaltered in corpus cavernosum from db/db compared to C57BL/6 and db/+ mice. Apamin, a blocker of KCa2 channels, inhibited acetylcholine relaxation in corpus cavernosum from all experimental groups. In the presence of apamin, acetylcholine relaxation was markedly decreased in corpus cavernosum from db/db vs C57BL/6 and db/+ mice. An opener of KCa2 and KCa3.1 channels, NS309, potentiated acetylcholine relaxations in corpus cavernosum from db/+ and db/db mice. Iberiotoxin, a blocker of KCa1.1 channels, inhibited acetylcholine relaxation in corpus cavernosum from db/+ mice, while there was no effect in tissue from db/db mice. CLINICAL TRANSLATION Erectile function in diabetic db/db mice was severely affected compared to heterozygous and control mice, findings suggesting the non-diabetic db/+ and diabetic db/db mice for translational purpose can be used for drug testing on, respectively, moderate and severe erectile dysfunction. The altered expressions and impaired acetylcholine relaxation in the presence of apamin compared to C57BL/6 mice may suggest decreased KCa1.1 channel function may underpin impaired endothelium-dependent relaxation and erectile dysfunction in diabetic db/db mice. STRENGTHS & LIMITATIONS The present study provides a mouse model for type 2 diabetes to test moderate and severe erectile dysfunction drugs. Decreased KCa1.1 channel function contributes to erectile dysfunction, and it is a limitation that it is not supported by electrophysiological measurements. CONCLUSION Our results suggest that the contribution of iberiotoxin-sensitive KCa1.1 channels to relaxation is reduced in the corpus cavernosum, while apamin-sensitive KCa2.3 channels appear upregulated. The impaired KCa1.1 channel function may contribute to the impaired erectile function in diabetic db/db mice.
Collapse
Affiliation(s)
- Simon Comerma-Steffensen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Department of Biomedical Sciences/Animal Physiology, Veterinary Faculty, Central University of Venezuela, Maracay, Aragua, Venezuela
| | | | - Susie Mogensen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Rafael Fais
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Pharmacology Department, Ribeirao Preto Medical School, Sao Paulo University, Brasil
| | | | - Ulf Simonsen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| |
Collapse
|
9
|
Lim XR, Bradley E, Griffin CS, Hollywood MA, Sergeant GP, Thornbury KD. Fast voltage-dependent sodium (Na V ) currents are functionally expressed in mouse corpus cavernosum smooth muscle cells. Br J Pharmacol 2021; 179:1082-1101. [PMID: 34767251 DOI: 10.1111/bph.15728] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 10/17/2021] [Accepted: 10/19/2021] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND AND PURPOSE Corpus cavernosum smooth muscle (CCSM) exhibits phasic contractions that are coordinated by ion channels. Mouse models are commonly used to study erectile dysfunction, but there are few published electrophysiological studies of mouse CCSM. We describe, for the first time, voltage-dependent sodium (NaV ) currents in mouse CCSM and investigate their function. EXPERIMENTAL APPROACH Electrophysiological, pharmacological, and immunocytochemical studies on isolated CCSM cells. Tension measurements in whole tissue. KEY RESULTS A fast, voltage-dependent sodium current was induced by depolarising steps. Steady-state activation and inactivation curves revealed a window current between -60 and -30 mV. Two populations of NaV currents, ('TTX-sensitive') and ('TTX-insensitive'), were distinguished. TTX-sensitive current showed 48% block with the NaV -subtype-specific blockers ICA-121431 (NaV 1.1-1.3), PF-05089771 (NaV 1.7), and 4,9-anhydro-TTX (NaV 1.6). TTX-insensitive current was insensitive to A803467, a NaV 1.8 blocker. Immunocytochemistry confirmed the expression of NaV 1.5 and NaV 1.4 in freshly dispersed CCSM cells. Veratridine, a NaV activator, reduced time-dependent inactivation of the current and increased the duration of evoked action potentials. Veratridine induced phasic contractions in CCSM strips. This effect was reversible with TTX and nifedipine but not by KB-R7943. CONCLUSION AND IMPLICATIONS We report, for the first time, a fast voltage-dependent sodium current in mouse CCSM. Stimulation of this current increases the contractility of corpus cavernosum in vitro, suggesting that it may contribute to the mechanisms of detumescence, and potentially serve as a clinically relevant target for pharmaceutical intervention in erectile dysfunction. Further work will be necessary to define its role.
Collapse
Affiliation(s)
| | | | | | | | | | - Keith D Thornbury
- Smooth Muscle Research Centre Dundalk Institute of Technology, Dublin, Ireland
| |
Collapse
|
10
|
He C, Li X, Wang M, Zhang S, Liu H. Deletion of BK channels decreased skeletal and cardiac muscle function but increased smooth muscle contraction in rats. Biochem Biophys Res Commun 2021; 570:8-14. [PMID: 34271438 DOI: 10.1016/j.bbrc.2021.07.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 07/07/2021] [Indexed: 12/28/2022]
Abstract
Large conductance calcium-activated potassium channel (BK channel) is widely expressed in skeletal muscle, myocardium, smooth muscle and other muscle tissues. Mutation, abnormal expression and altered activity of BK channel are linked to muscle-related diseases such as dyskinesia, epilepsy and erectile dysfunction. In order to compare the effects of BK channel on different muscle tissues, we constructed BK channel gene knockout rats (BK-/- rats). HE staining, open field and grip strength tests, ultrasound, blood pressure measurement and vascular tension test were utilized to explore the effects of BK channel deletion on the structure and function changes in skeletal muscle, myocardium, and vascular smooth muscle (VSM). It was found that compared with wild-type rats, the BK-/- rats showed decreased skeletal muscle fiber area, grip, movement distance and speed at 2 and 12 months of ages. At heart, the muscle fiber area, cardiac systolic/diastolic function and heart rate decreased in BK-/- rats. The wall of the left ventricle became thin. However, the vascular wall of BK-/- rats thickened, the pulse wave velocity was increased, and the VSM contraction was enhanced. Unexpectedly, both systolic and diastolic blood pressure were reduced in BK-/- rats, while pulse pressure difference was increased. These results suggest that BK channel may have different effects on different types of muscle tissue, and it should be noted that different parts of muscle tissue may have different effects when BK channel-related drugs are used.
Collapse
Affiliation(s)
- Chunyu He
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China; Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Disease, Beijing, 100069, China
| | - Xiaoyue Li
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China; Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Disease, Beijing, 100069, China
| | - Meili Wang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China; Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Disease, Beijing, 100069, China
| | - Suli Zhang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China; Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Disease, Beijing, 100069, China.
| | - Huirong Liu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China; Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Disease, Beijing, 100069, China.
| |
Collapse
|
11
|
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.
Collapse
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.)
| |
Collapse
|
12
|
Szteyn K, Singh H. BK Ca Channels as Targets for Cardioprotection. Antioxidants (Basel) 2020; 9:antiox9080760. [PMID: 32824463 PMCID: PMC7463653 DOI: 10.3390/antiox9080760] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/09/2020] [Accepted: 08/13/2020] [Indexed: 12/16/2022] Open
Abstract
The large-conductance calcium- and voltage-activated K+ channel (BKCa) are encoded by the Kcnma1 gene. They are ubiquitously expressed in neuronal, smooth muscle, astrocytes, and neuroendocrine cells where they are known to play an important role in physiological and pathological processes. They are usually localized to the plasma membrane of the majority of the cells with an exception of adult cardiomyocytes, where BKCa is known to localize to mitochondria. BKCa channels couple calcium and voltage responses in the cell, which places them as unique targets for a rapid physiological response. The expression and activity of BKCa have been linked to several cardiovascular, muscular, and neurological defects, making them a key therapeutic target. Specifically in the heart muscle, pharmacological and genetic activation of BKCa channels protect the heart from ischemia-reperfusion injury and also facilitate cardioprotection rendered by ischemic preconditioning. The mechanism involved in cardioprotection is assigned to the modulation of mitochondrial functions, such as regulation of mitochondrial calcium, reactive oxygen species, and membrane potential. Here, we review the progress made on BKCa channels and cardioprotection and explore their potential roles as therapeutic targets for preventing acute myocardial infarction.
Collapse
|
13
|
Diniz AFA, Ferreira RC, de Souza ILL, da Silva BA. Ionic Channels as Potential Therapeutic Targets for Erectile Dysfunction: A Review. Front Pharmacol 2020; 11:1120. [PMID: 32848741 PMCID: PMC7396897 DOI: 10.3389/fphar.2020.01120] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 07/10/2020] [Indexed: 12/12/2022] Open
Abstract
Erectile dysfunction (ED) is a prevalent condition, especially in men over 40 years old, characterized by the inability to obtain and/or maintain penile erection sufficient for satisfactory sexual intercourse. Several psychological and/or organic factors are involved in the etiopathogenesis of ED. In this context, we gathered evidence of the involvement of Large-conductance, Ca2+-activated K+ channels (BKCa), Small-conductance, Ca2+-activated K+ channels (SKCa), KCNQ-encoded voltage-dependent K+ channels (KV7), Transient Receptor Potential channels (TRP), and Calcium-activated Chloride channels (CaCC) dysfunctions on ED. In addition, the use of modulating agents of these channels are involved in relaxation of the cavernous smooth muscle cell and, consequent penile erection, suggesting that these channels are promising therapeutic targets for the treatment of erectile dysfunction.
Collapse
Affiliation(s)
- Anderson Fellyp Avelino Diniz
- Programa de Pós-Graduação em Produtos Naturais e Sintéticos Bioativos, Universidade Federal da Paraíba, João Pessoa, Brazil
| | - Rafael Carlos Ferreira
- Programa de Pós-Graduação em Produtos Naturais e Sintéticos Bioativos, Universidade Federal da Paraíba, João Pessoa, Brazil
| | - Iara Leão Luna de Souza
- Departamento de Ciências Biológicas e da Saúde, Universidade Estadual de Roraima, Boa Vista, Brazil
| | - Bagnólia Araújo da Silva
- Programa de Pós-Graduação em Produtos Naturais e Sintéticos Bioativos, Universidade Federal da Paraíba, João Pessoa, Brazil
| |
Collapse
|
14
|
Plante AE, Lai MH, Lu J, Meredith AL. Effects of Single Nucleotide Polymorphisms in Human KCNMA1 on BK Current Properties. Front Mol Neurosci 2019; 12:285. [PMID: 31849601 PMCID: PMC6901604 DOI: 10.3389/fnmol.2019.00285] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 11/12/2019] [Indexed: 12/14/2022] Open
Abstract
BK Ca2+-activated K+ channels are important regulators of membrane excitability. Multiple regulatory mechanisms tailor BK current properties across tissues, such as alternative splicing, posttranslational modifications, and auxiliary subunits. Another potential mechanism for modulating BK channel activity is genetic variation due to single nucleotide polymorphisms (SNPs). The gene encoding the human BK α subunit, KCNMA1, contains hundreds of SNPs. However, the variation in BK channel activity due to SNPs is not well studied. Here, we screened the effects of four SNPs (A138V, C495G, N599D, and R800W) on BK currents in HEK293T cells, selected based on predicted protein pathogenicity or disease linkage. We found that the SNPs C495G and R800W had the largest effects on BK currents, affecting the conductance–voltage relationship across multiple Ca2+ conditions in the context of two BK channel splice variants. In symmetrical K+, C495G shifted the V1/2 to more hyperpolarized potentials (by −15 to −20 mV) and accelerated activation, indicating C495G confers some gain-of-function properties. R800W shifted the V1/2 to more depolarized potentials (+15 to +35 mV) and slowed activation, conferring loss-of-function properties. Moreover, the C495G and R800W effects on current properties were found to persist with posttranslational modifications. In contrast, A138V and N599D had smaller and more variable effects on current properties. Neither application of alkaline phosphatase to patches, which results in increased BK channel activity attributed to channel dephosphorylation, nor bidirectional redox modulations completely abrogated SNP effects on BK currents. Lastly, in physiological K+, C495G increased the amplitude of action potential (AP)-evoked BK currents, while R800W had a more limited effect. However, the introduction of R800W in parallel with the epilepsy-linked mutation D434G (D434G/R800W) decreased the amplitude of AP-evoked BK currents compared with D434G alone. These results suggest that in a physiological context, C495G could increase BK activation, while the effects of the loss-of-function SNP R800W could oppose the gain-of-function effects of an epilepsy-linked mutation. Together, these results implicate naturally occurring human genetic variation as a potential modifier of BK channel activity across a variety of conditions.
Collapse
Affiliation(s)
- Amber E Plante
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Michael H Lai
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Jessica Lu
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| |
Collapse
|
15
|
Bailey CS, Moldenhauer HJ, Park SM, Keros S, Meredith AL. KCNMA1-linked channelopathy. J Gen Physiol 2019; 151:1173-1189. [PMID: 31427379 PMCID: PMC6785733 DOI: 10.1085/jgp.201912457] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 08/13/2019] [Indexed: 12/20/2022] Open
Abstract
Bailey et al. review a new neurological channelopathy associated with KCNMA1, encoding the BK voltage- and Ca2+-activated K+ channel. KCNMA1 encodes the pore-forming α subunit of the “Big K+” (BK) large conductance calcium and voltage-activated K+ channel. BK channels are widely distributed across tissues, including both excitable and nonexcitable cells. Expression levels are highest in brain and muscle, where BK channels are critical regulators of neuronal excitability and muscle contractility. A global deletion in mouse (KCNMA1−/−) is viable but exhibits pathophysiology in many organ systems. Yet despite the important roles in animal models, the consequences of dysfunctional BK channels in humans are not well characterized. Here, we summarize 16 rare KCNMA1 mutations identified in 37 patients dating back to 2005, with an array of clinically defined pathological phenotypes collectively referred to as “KCNMA1-linked channelopathy.” These mutations encompass gain-of-function (GOF) and loss-of-function (LOF) alterations in BK channel activity, as well as several variants of unknown significance (VUS). Human KCNMA1 mutations are primarily associated with neurological conditions, including seizures, movement disorders, developmental delay, and intellectual disability. Due to the recent identification of additional patients, the spectrum of symptoms associated with KCNMA1 mutations has expanded but remains primarily defined by brain and muscle dysfunction. Emerging evidence suggests the functional BK channel alterations produced by different KCNMA1 alleles may associate with semi-distinct patient symptoms, such as paroxysmal nonkinesigenic dyskinesia (PNKD) with GOF and ataxia with LOF. However, due to the de novo origins for the majority of KCNMA1 mutations identified to date and the phenotypic variability exhibited by patients, additional evidence is required to establish causality in most cases. The symptomatic picture developing from patients with KCNMA1-linked channelopathy highlights the importance of better understanding the roles BK channels play in regulating cell excitability. Establishing causality between KCNMA1-linked BK channel dysfunction and specific patient symptoms may reveal new treatment approaches with the potential to increase therapeutic efficacy over current standard regimens.
Collapse
Affiliation(s)
- Cole S Bailey
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Hans J Moldenhauer
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Su Mi Park
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Sotirios Keros
- Department of Pediatrics, University of South Dakota Sanford School of Medicine, Sioux Falls, SD
| | - Andrea L Meredith
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD
| |
Collapse
|
16
|
Thornbury KD, Hollywood MA, Sergeant GP. Ion Channels and Intracellular Calcium Signalling in Corpus Cavernosum. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1124:171-194. [PMID: 31183827 DOI: 10.1007/978-981-13-5895-1_7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The corpus cavernosum smooth muscle is important for both erection of the penis and for maintaining penile flaccidity. Most of the time, the smooth muscle cells are in a contracted state, which limits filling of the corpus sinuses with blood. Occasionally, however, they relax in a co-ordinated manner, allowing filling to occur. This results in an erection. When contractions of the corpus cavernosum are measured, it can be deduced that the muscle cells work together in a syncytium, for not only do they spontaneously contract in a co-ordinated manner, but they also synchronously relax. It is challenging to understand how they achieve this.In this review we will attempt to explain the activity of the corpus cavernosum, firstly by summarising current knowledge regarding the role of ion channels and how they influence tone, and secondly by presenting data on the intracellular Ca2+ signals that interact with the ion channels. We propose that spontaneous Ca2+ waves act as a primary event, driving transient depolarisation by activating Ca2+-activated Cl- channels. Depolarisation then facilitates Ca2+ influx via L-type voltage-dependent Ca2+ channels. We propose that the spontaneous Ca2+ oscillations depend on Ca2+ release from both ryanodine- and inositol trisphosphate (IP3)-sensitive stores and that modulation by signalling molecules is achieved mainly by interactions with the IP3-sensitive mechanism. This pacemaker mechanism is inhibited by nitric oxide (acting through cyclic GMP) and enhanced by noradrenaline. By understanding these mechanisms better, it might be possible to design new treatments for erectile dysfunction.
Collapse
Affiliation(s)
- Keith D Thornbury
- Smooth Muscle Research Centre, Regional Development Centre, Dundalk Institute of Technology, Dundalk, Co. Louth, Ireland.
| | - Mark A Hollywood
- Smooth Muscle Research Centre, Regional Development Centre, Dundalk Institute of Technology, Dundalk, Co. Louth, Ireland
| | - Gerard P Sergeant
- Smooth Muscle Research Centre, Regional Development Centre, Dundalk Institute of Technology, Dundalk, Co. Louth, Ireland
| |
Collapse
|
17
|
Abstract
The large-conductance calcium- and voltage-activated K+ (BK) channel has a requirement of high intracellular free Ca2+ concentrations for its activation in neurons under physiological conditions. The Ca2+ sources for BK channel activation are not well understood. In this study, we showed by coimmunopurification and colocalization analyses that BK channels form complexes with NMDA receptors (NMDARs) in both rodent brains and a heterologous expression system. The BK-NMDAR complexes are broadly present in different brain regions. The complex formation occurs between the obligatory BKα and GluN1 subunits likely via a direct physical interaction of the former's intracellular S0-S1 loop with the latter's cytosolic regions. By patch-clamp recording on mouse brain slices, we observed BK channel activation by NMDAR-mediated Ca2+ influx in dentate gyrus granule cells. BK channels modulate excitatory synaptic transmission via functional coupling with NMDARs at postsynaptic sites of medial perforant path-dentate gyrus granule cell synapses. A synthesized peptide of the BKα S0-S1 loop region, when loaded intracellularly via recording pipette, abolished the NMDAR-mediated BK channel activation and effect on synaptic transmission. These findings reveal the broad expression of the BK-NMDAR complexes in brain, the potential mechanism underlying the complex formation, and the NMDAR-mediated activation and function of postsynaptic BK channels in neurons.
Collapse
|
18
|
Molecular determinants of Ca 2+ sensitivity at the intersubunit interface of the BK channel gating ring. Sci Rep 2018; 8:509. [PMID: 29323236 PMCID: PMC5765161 DOI: 10.1038/s41598-017-19029-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 12/19/2017] [Indexed: 12/31/2022] Open
Abstract
The large-conductance calcium-activated K+ (BK) channel contains two intracellular tandem Ca2+-sensing RCK domains (RCK1 and RCK2), which tetramerize into a Ca2+ gating ring that regulates channel opening by conformational expansion in response to Ca2+ binding. Interestingly, the gating ring’s intersubunit assembly interface harbors the RCK2 Ca2+-binding site, known as the Ca2+ bowl. The gating ring’s assembly interface is made in part by intersubunit coordination of a Ca2+ ion between the Ca2+ bowl and an RCK1 Asn residue, N449, and by apparent intersubunit electrostatic interactions between E955 in RCK2 and R786 and R790 in the RCK2 of the adjacent subunit. To understand the role of the intersubunit assembly interface in Ca2+ gating, we performed mutational analyses of these putative interacting residues in human BK channels. We found that N449, despite its role in Ca2+ coordination, does not set the channel’s Ca2+ sensitivity, whereas E955 is a determinant of Ca2+ sensitivity, likely through intersubunit electrostatic interactions. Our findings provide evidence that the intersubunit assembly interface contains molecular determinants of Ca2+-sensitivity in BK channels.
Collapse
|
19
|
Comerma-Steffensen SG, Carvacho I, Hedegaard ER, Simonsen U. Small and Intermediate Calcium-Activated Potassium Channel Openers Improve Rat Endothelial and Erectile Function. Front Pharmacol 2017; 8:660. [PMID: 28993731 PMCID: PMC5619997 DOI: 10.3389/fphar.2017.00660] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 09/05/2017] [Indexed: 12/13/2022] Open
Abstract
Modulation of endothelial calcium-activated potassium (KCa) channels has been proposed as an approach to restore endothelial function. The present study investigated whether novel openers of KCa channels with small (KCa2.x) and intermediate (KCa3.1) conductance, NS309 and NS4591, improve endothelium-dependent relaxation and erectile function. Rat corpus cavernosum (CC) strips were mounted for isometric tension recording and processed for immunoblotting. Mean arterial pressure (MAP), intracavernosal pressure (ICP), and electrocardiographic (ECG) measurements were conducted in anesthetized rats. Immunoblotting revealed the presence of KCa2.3 and large KCa conductance (KCa1.1) channels in the corpus cavernosum. NS309 and NS4591 increased current in CC endothelial cells in whole cell patch clamp experiments. Relaxation induced by NS309 (<1 μM) was inhibited by endothelial cell removal and high extracellular potassium. An inhibitor of nitric oxide (NO) synthase, and blockers of KCa2.x and KCa1.1 channels, apamin and iberiotoxin also inhibited NS309 relaxation. Incubation with NS309 (0.5 μM) markedly enhanced acetylcholine relaxation. Basal erectile function (ICP/MAP) increased during administration of NS309. Increases in ICP/MAP after cavernous nerve stimulation with NS309 were unchanged, whereas NS4591 significantly improved erectile function. Administration of NS309 and NS4591 caused small changes in the electrocardiogram, but neither arrhythmic events nor prolongation of the QTc interval were observed. The present study suggests that openers of KCa2.x and KCa3.1 channels improve endothelial and erectile function. The effects of NS309 and NS4591 on heart rate and ECG are small, but will require additional safety studies before evaluating whether activation of KCa2.3 channels has a potential for treatment of erectile dysfunction.
Collapse
Affiliation(s)
- Simon G. Comerma-Steffensen
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus UniversityAarhus, Denmark
- Animal Physiology, Department of Biomedical Sciences, Veterinary Sciences Faculty, Central University of VenezuelaMaracay, Venezuela
| | - Ingrid Carvacho
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus UniversityAarhus, Denmark
- Department of Biology and Chemistry, Faculty of Basic Sciences, Universidad Católica del MauleTalca, Chile
| | - Elise R. Hedegaard
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus UniversityAarhus, Denmark
| | - Ulf Simonsen
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus UniversityAarhus, Denmark
| |
Collapse
|
20
|
Zhang ZY, Qian LL, Wang RX. Molecular Mechanisms Underlying Renin-Angiotensin-Aldosterone System Mediated Regulation of BK Channels. Front Physiol 2017; 8:698. [PMID: 28955251 PMCID: PMC5601423 DOI: 10.3389/fphys.2017.00698] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 08/30/2017] [Indexed: 12/21/2022] Open
Abstract
Large-conductance calcium-activated potassium channels (BK channels) belong to a family of Ca2+-sensitive voltage-dependent potassium channels and play a vital role in various physiological activities in the human body. The renin-angiotensin-aldosterone system is acknowledged as being vital in the body's hormone system and plays a fundamental role in the maintenance of water and electrolyte balance and blood pressure regulation. There is growing evidence that the renin-angiotensin-aldosterone system has profound influences on the expression and bioactivity of BK channels. In this review, we focus on the molecular mechanisms underlying the regulation of BK channels mediated by the renin-angiotensin-aldosterone system and its potential as a target for clinical drugs.
Collapse
Affiliation(s)
- Zhen-Ye Zhang
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical UniversityWuxi, China
| | - Ling-Ling Qian
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical UniversityWuxi, China
| | - Ru-Xing Wang
- Department of Cardiology, Wuxi People's Hospital Affiliated to Nanjing Medical UniversityWuxi, China
| |
Collapse
|
21
|
Hannigan KI, Griffin CS, Large RJ, Sergeant GP, Hollywood MA, McHale NG, Thornbury KD. The role of Ca 2+-activated Cl - current in tone generation in the rabbit corpus cavernosum. Am J Physiol Cell Physiol 2017; 313:C475-C486. [PMID: 28835432 DOI: 10.1152/ajpcell.00025.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 08/03/2017] [Accepted: 08/09/2017] [Indexed: 11/22/2022]
Abstract
Rabbit corpus cavernosum smooth muscle (RCCSM) cells express ion channels that produce Ca2+-activated Cl- (IClCa) current, but low sensitivity to conventional antagonists has made its role in tone generation difficult to evaluate. We have reexamined this question using two new generation IClCa blockers, T16Ainh-A01 and CaCCinh-A01. Isolated RCCSM cells were studied using the perforated patch method. Current-voltage protocols revealed that both L-type Ca2+ current and IClCa T16Ainh-A01 and CaCCinh-A01 (10 μM) reduced IClCa by ~85%, while 30 μM abolished it. L-type Ca2+ current was unaffected by 10 μM CaCCinh-A01 but was reduced by 50% at 30 μM CaCCinh-A01, 46% at 10 μM T16Ainh-A01, and 78% at 30 μM T16Ainh-A01. Both drugs reduced spontaneous isometric tension in RCCSM strips, by 60-70% at 10 μM and >90% at 30 μM. Phenylephrine (PE)-enhanced tension was also reduced (ED50 = 3 μM, CaCCinh-A01; 14 μM, T16Ainh-A01). CaCCinh-A01 at 10 μM had little effect on 60 mM KCl contractures, though they were reduced by 30 μM CaCCinh-A01 and T16Ainh-A01 (10 μM and 30 μM) consistent with their effects on L-type Ca2+ current. Both drugs also reversed the stimulatory effect of PE on intracellular Ca2+ waves, studied with laser scanning confocal microscopy in isolated RCCSM cells. In conclusion, although both drugs were effective blockers of IClCa, the effect of T16Ainh-A01 on L-type Ca2+ current precludes its use for evaluating the role of IClCa in tone generation. However, 10 μM CaCCinh-A01 selectively blocked IClCa versus L-type Ca2+ current and reduced spontaneous and PE-induced tone, suggesting that IClCa is important in maintaining penile detumescence.
Collapse
Affiliation(s)
- Karen I Hannigan
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - Caoimhin S Griffin
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - Roddy J Large
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - Gerard P Sergeant
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - Mark A Hollywood
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - Noel G McHale
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - Keith D Thornbury
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| |
Collapse
|
22
|
Choo SH, Lee SW, Chae MR, Kang SJ, Sung HH, Han DH, Chun JN, Park JK, Kim CY, Kim HK, So I. Effects of eupatilin on the contractility of corpus cavernosal smooth muscle through nitric oxide-independent pathways. Andrology 2017; 5:1016-1022. [PMID: 28719725 DOI: 10.1111/andr.12397] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 05/26/2017] [Accepted: 06/09/2017] [Indexed: 12/19/2022]
Abstract
Eupatilin (5,7-dihydroxy-3,4,6-trimethoxyflavone) is one of the main compounds present in Artemisia species. Eupatilin has both antioxidative and anti-inflammatory properties and a relaxation effect on vascular contraction regardless of endothelial function. We evaluated the relaxant effects of eupatilin on the corpus cavernosum (CC) of rabbits and the underlying mechanisms of its activity in human corpus cavernosum smooth muscle (CCSM) cells. Isolated rabbit CC strips were mounted in an organ bath system. A conventional whole-cell patch clamp technique was used to measure activation of calcium-sensitive K+ -channel currents in human CCSM cells. The relaxation effect of eupatilin was evaluated by cumulative addition (10-5 m ~ 3 × 10-4 m) to CC strips precontracted with 10-5 m phenylephrine. Western blotting analysis was performed to measure myosin phosphatase targeting subunit 1 (MYPT1) and protein kinase C-potentiated inhibitory protein for heterotrimeric myosin light chain phosphatase of 17-kDa (CPI-17) expression and to evaluate the effect of eupatilin on the RhoA/Rho-kinase pathway. Eupatilin effectively relaxed the phenylephrine-induced tone in the rabbit CC strips in a concentration-dependent manner with an estimated EC50 value of 1.2 ± 1.6 × 10-4 m (n = 8, p < 0.05). Iberiotoxin and tetraethylammonium significantly reduced the relaxation effect (n = 8, p < 0.001 and p = 0.003, respectively). Removal of the endothelium or the presence of L-NAME or indomethacin did not affect the relaxation effect of eupatilin. In CCSM cells, the extracellular application of eupatilin 10-4 m significantly increased the outward currents, and the eupatilin-stimulated currents were significantly attenuated by treatment with 10-7 m iberiotoxin (n = 13, p < 0.05). Eupatilin reduced the phosphorylation level of MYPT1 at Thr853 of MLCP and CPI-17 at Thr38. Eupatilin-induced relaxation of the CCSM cells via NO-independent pathways. The relaxation effects of eupatilin on CCSM cells were partially due to activation of BKCa channels and inhibition of RhoA/Rho-kinase.
Collapse
Affiliation(s)
- S H Choo
- Department of Urology, Ajou University School of Medicine, Suwon, Korea
| | - S W Lee
- Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - M R Chae
- Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - S J Kang
- Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - H H Sung
- Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - D H Han
- Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - J N Chun
- Department of Physiology and Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea
| | - J K Park
- Department of Urology, Institute for Medical Sciences, Medical School, Chonbuk National University, Research Institute and Clinical Trial Center of Medical Device of Chonbuk National University Hospital, Jeonju, Korea
| | - C Y Kim
- College of Pharmacy and Institute of Pharmaceutical Science and Technology, Hanyang University, Ansan, Korea
| | - H K Kim
- College of Pharmacy, Kyungsung University, Busan, Korea
| | - I So
- Department of Physiology, Seoul National University College of Medicine, Seoul, Korea
| |
Collapse
|
23
|
Comerma-Steffensen S, Kun A, Hedegaard ER, Mogensen S, Aalkjaer C, Köhler R, Mønster Christensen B, Simonsen U. Down-regulation of K Ca2.3 channels causes erectile dysfunction in mice. Sci Rep 2017. [PMID: 28630432 PMCID: PMC5476588 DOI: 10.1038/s41598-017-04188-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Modulation of endothelial calcium-activated K+ channels has been proposed as an approach to restore arterial endothelial cell function in disease. We hypothesized that small-conductance calcium-activated K+ channels (KCa2.3 or SK3) contributes to erectile function. The research was performed in transgenic mice with overexpression (KCa2.3T/T(−Dox)) or down-regulation (KCa2.3T/T(+Dox)) of the KCa2.3 channels and wild-type C57BL/6-mice (WT). QPCR revealed that KCa2.3 and KCa1.1 channels were the most abundant in mouse corpus cavernosum. KCa2.3 channels were found by immunoreactivity and electron microscopy in the apical-lateral membrane of endothelial cells in the corpus cavernosum. Norepinephrine contraction was enhanced in the corpus cavernosum of KCa2.3T/T(+Dox)versus KCa2.3T/T(−Dox) mice, while acetylcholine relaxation was only reduced at 0.3 µM and relaxations in response to the nitric oxide donor sodium nitroprusside were unaltered. An opener of KCa2 channels, NS309 induced concentration-dependent relaxations of corpus cavernosum. Mean arterial pressure was lower in KCa2.3T/T(−Dox) mice compared with WT and KCa2.3T/T(+Dox) mice. In anesthetized mice, cavernous nerve stimulation augmented in frequency/voltage dependent manner erectile function being lower in KCa2.3T/T(+Dox) mice at low frequencies. Our findings suggest that down-regulation of KCa2.3 channels contributes to erectile dysfunction, and that pharmacological activation of KCa2.3 channels may have the potential to restore erectile function.
Collapse
Affiliation(s)
- Simon Comerma-Steffensen
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Aarhus, Denmark.
| | - Attila Kun
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Aarhus, Denmark
| | - Elise R Hedegaard
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Aarhus, Denmark
| | - Susie Mogensen
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Aarhus, Denmark
| | | | - Ralf Köhler
- Aragon Agency for Investigation and Development (ARAID), Translational Research Unit, Miguel Servet University Hospital, Zaragoza, Spain
| | | | - Ulf Simonsen
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Aarhus, Denmark
| |
Collapse
|
24
|
Senbel AM, Abd Elmoneim HM, Sharabi FM, Mohy El-Din MM. Neuronal Voltage Gated Potassium Channels May Modulate Nitric Oxide Synthesis in Corpus Cavernosum. Front Pharmacol 2017; 8:297. [PMID: 28603495 PMCID: PMC5445172 DOI: 10.3389/fphar.2017.00297] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Accepted: 05/10/2017] [Indexed: 11/24/2022] Open
Abstract
Potassium channels (K+Ch) in corpus cavernosum play an important role in the regulation of erection. Nitric oxide (NO) acts through opening of K+Ch leading to hyperpolarization and relaxation. Aim : This study aims to update knowledge about the role of voltage-gated K+Ch (KV) channels in erectile machinery and investigate their role in the control of NO action &/or synthesis in the corpus cavernosum. Methods : Tension studies using isolated rabbit corpus cavernosum (CC) strips and rat anococcygeus muscle were conducted. Results are expressed as mean ± SEM. Results : Electric field stimulation (EFS, 2–16 Hz) evoked frequency-dependent relaxations of the PE (phenylephrine)-precontracted CC strips. At 2 Hz, EFS-induced relaxation amounted to 73.17 ± 2.55% in presence 4-AP (10−3 M) compared to 41.98 ± 1.45% as control. None of the other selective K+Ch blockers tested inhibited EFS-induced relaxation. 4-AP (10−3M) significantly attenuated ACh-induced relaxation of rabbit CC where dose-response curve was clearly shifted upward, and attenuated SNP- induced relaxation, for example, to 49.28 ± 4.52% compared to 65.53 ± 3.01% as control at 10−6 M SNP. The potentiatory effect of 4-AP on EFS was abolished or reversed in presence of NG-nitro-L-arginine (L-NNA, non-selective nitric oxide synthase inhibitor, 10−5M, and 2 × 10−4M). Same results were observed in rat anococcygeus muscle which is a part of the erectile machinery in rats. Conclusion : This study provides evidence for the presence of prejunctional voltage-gated K+Ch in CC, the blockade of which may increase the neuronal synthesis of NO.
Collapse
Affiliation(s)
- Amira M Senbel
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Alexandria UniversityAlexandria, Egypt
| | - Heba M Abd Elmoneim
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Alexandria UniversityAlexandria, Egypt
| | - Fouad M Sharabi
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Alexandria UniversityAlexandria, Egypt
| | - Mahmoud M Mohy El-Din
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Alexandria UniversityAlexandria, Egypt
| |
Collapse
|
25
|
Halm ST, Bottomley MA, Almutairi MM, Di Fulvio M, Halm DR. Survival and growth of C57BL/6J mice lacking the BK channel, Kcnma1: lower adult body weight occurs together with higher body fat. Physiol Rep 2017; 5:5/4/e13137. [PMID: 28242822 PMCID: PMC5328773 DOI: 10.14814/phy2.13137] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 12/23/2016] [Accepted: 01/02/2017] [Indexed: 11/29/2022] Open
Abstract
Big conductance potassium (BK) channels contribute to K+ flow and electrical behavior in many cell types. Mice made null for the gene (Kcnma1) producing the BK channel (BKKO) exhibit numerous deficits in physiological functions. Breeding mice lacking a single allele of Kcnma1 (C57BL/6J background) had litter sizes of approximately eight pups. For the period of maternal care (P0–P21), pup deaths peaked at P1 with a second less severe interval of death peaking near P13. Early deaths were twice as likely during a 20‐month period of building construction compared with the quiescent period after cessation of construction. Births during construction were not consistent with Mendelian predictions indicating the likelihood of a specific disadvantage induced by this environmental stressor. Later BKKO pup deaths (~P13) also were more numerous than Mendelian expectations. After weaning, weight gain was slower for BKKO mice compared with wild‐type littermates: 5 g less for male BKKO mice and 4 g less for female BKKO mice. Body composition determined by quantitative magnetic resonance indicated a higher fat proportion for wild‐type female mice compared with males, as well as a higher hydration ratio. Both male and female BKKO mice showed higher fat proportions than wild‐type, with female BKKO mice exhibiting greater variation. Together, these results indicate that BKKO mice suffered disadvantages that lead to prenatal and perinatal death. A metabolic difference likely related to glucose handling led to the smaller body size and distinct composition for BKKO mice, suggesting a diversion of energy supplies from growth to fat storage.
Collapse
Affiliation(s)
- Susan T Halm
- Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine, Dayton, Ohio
| | - Michael A Bottomley
- Department of Mathematics and Statistics, Statistical Consulting Center, Wright State University, Dayton, Ohio
| | - Mohammed M Almutairi
- Department of Pharmacology and Toxicology, Wright State University Boonshoft School of Medicine, Dayton, Ohio
| | - Maurico Di Fulvio
- Department of Pharmacology and Toxicology, 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
| |
Collapse
|
26
|
Affiliation(s)
- Gail A Robertson
- a Department of Neuroscience , University of Wisconsin School of Medicine and Public Health , Madison , WI , USA
| |
Collapse
|
27
|
Lee S, Chae MR, Lee BC, Kim YC, Choi JS, Lee SW, Cheong JH, Park CS. Urinary Bladder-Relaxant Effect of Kurarinone Depending on Potentiation of Large-Conductance Ca2+-Activated K+ Channels. Mol Pharmacol 2016; 90:140-50. [DOI: 10.1124/mol.115.102939] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 05/31/2016] [Indexed: 01/27/2023] Open
|
28
|
Hoshi T, Heinemann SH. Modulation of BK Channels by Small Endogenous Molecules and Pharmaceutical Channel Openers. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 128:193-237. [PMID: 27238265 DOI: 10.1016/bs.irn.2016.03.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Voltage- and Ca(2+)-activated K(+) channels of big conductance (BK channels) are abundantly found in various organs and their relevance for smooth muscle tone and neuronal signaling is well documented. Dysfunction of BK channels is implicated in an array of human diseases involving many organs including the nervous, pulmonary, cardiovascular, renal, and urinary systems. In humans a single gene (KCNMA1) encodes the pore-forming α subunit (Slo1) of BK channels, but the channel properties are variable because of alternative splicing, tissue- and subcellular-specific auxiliary subunits (β, γ), posttranslational modifications, and a multitude of endogenous signaling molecules directly affecting the channel function. Initiatives to develop drugs capable of activating BK channels (channel openers) therefore need to consider the tissue-specific variability of BK channel structure and the potential interference with endogenously produced regulatory factors. The atomic structural basis of BK channel function is only beginning to be revealed. However, building on detailed knowledge of BK channel function, including its single-channel characteristics, voltage- and Ca(2+) dependence of channel gating, and modulation by diffusible messengers, a multi-tier allosteric model of BK channel gating (Horrigan and Aldrich (HA) model) has become a valuable tool in studying modulation of the channel. Using the conceptual framework of the HA model, we here review the functional impact of endogenous modulatory factors and select small synthetic compounds that regulate BK channel activity. Furthermore, we devise experimental approaches for studying BK channel-drug interactions with the aim to classify BK-modulating substances according to their molecular mode of action.
Collapse
Affiliation(s)
- T Hoshi
- University of Pennsylvania, Philadelphia, PA, United States.
| | - S H Heinemann
- Friedrich Schiller University Jena & Jena University Hospital, Jena, Germany
| |
Collapse
|
29
|
Krishnamoorthy-Natarajan G, Koide M. BK Channels in the Vascular System. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 128:401-38. [PMID: 27238270 DOI: 10.1016/bs.irn.2016.03.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Autoregulation of blood flow is essential for the preservation of organ function to ensure continuous supply of oxygen and essential nutrients and removal of metabolic waste. This is achieved by controlling the diameter of muscular arteries and arterioles that exhibit a myogenic response to changes in arterial blood pressure, nerve activity and tissue metabolism. Large-conductance voltage and Ca(2+)-dependent K(+) channels (BK channels), expressed exclusively in smooth muscle cells (SMCs) in the vascular wall of healthy arteries, play a critical role in regulating the myogenic response. Activation of BK channels by intracellular, local, and transient ryanodine receptor-mediated "Ca(2+) sparks," provides a hyperpolarizing influence on the SMC membrane potential thereby decreasing the activity of voltage-dependent Ca(2+) channels and limiting Ca(2+) influx to promote SMC relaxation and vasodilation. The BK channel α subunit, a large tetrameric protein with each monomer consisting of seven-transmembrane domains, a long intracellular C-terminal tail and an extracellular N-terminus, associates with the β1 and γ subunits in vascular SMCs. The BK channel is regulated by factors originating within the SMC or from the endothelium, perivascular nerves and circulating blood, that significantly alter channel gating properties, Ca(2+) sensitivity and expression of the α and/or β1 subunit. The BK channel thus serves as a central receiving dock that relays the effects of the changes in several such concomitant autocrine and paracrine factors and influences cardiovascular health. This chapter describes the primary mechanism of regulation of myogenic response by BK channels and the alterations to this mechanism wrought by different vasoactive mediators.
Collapse
Affiliation(s)
| | - M Koide
- University of Vermont, Burlington, VT, United States
| |
Collapse
|
30
|
Li B, Gao TM. Functional Role of Mitochondrial and Nuclear BK Channels. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 128:163-91. [PMID: 27238264 DOI: 10.1016/bs.irn.2016.03.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BK channels are important for the regulation of many cell functions. The significance of plasma membrane BK channels in the control of action potentials, resting membrane potential, and neurotransmitter release is well established; however, the composition and functions of mitochondrial and nuclear BK (nBK) channels are largely unknown. In this chapter, we summarize the recent findings on the subcellular localization, biophysical, and pharmacological properties of mitochondrial and nBK channels and discuss their molecular identity and physiological functions.
Collapse
Affiliation(s)
- B Li
- State Key Laboratory of Organ Failure Research, Key Laboratory of Psychiatric Disorders of Guangdong Province, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
| | - T-M Gao
- State Key Laboratory of Organ Failure Research, Key Laboratory of Psychiatric Disorders of Guangdong Province, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China.
| |
Collapse
|
31
|
Modulation of BK Channel Function by Auxiliary Beta and Gamma Subunits. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 128:51-90. [PMID: 27238261 DOI: 10.1016/bs.irn.2016.03.015] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The large-conductance, Ca(2+)- and voltage-activated K(+) (BK) channel is ubiquitously expressed in mammalian tissues and displays diverse biophysical or pharmacological characteristics. This diversity is in part conferred by channel modulation with different regulatory auxiliary subunits. To date, two distinct classes of BK channel auxiliary subunits have been identified: β subunits and γ subunits. Modulation of BK channels by the four auxiliary β (β1-β4) subunits has been well established and intensively investigated over the past two decades. The auxiliary γ subunits, however, were identified only very recently, which adds a new dimension to BK channel regulation and improves our understanding of the physiological functions of BK channels in various tissues and cell types. This chapter will review the current understanding of BK channel modulation by auxiliary β and γ subunits, especially the latest findings.
Collapse
|
32
|
Jepps TA, Olesen SP, Greenwood IA, Dalsgaard T. Molecular and functional characterization of Kv 7 channels in penile arteries and corpus cavernosum of healthy and metabolic syndrome rats. Br J Pharmacol 2016; 173:1478-90. [PMID: 26802314 DOI: 10.1111/bph.13444] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 01/13/2016] [Accepted: 01/15/2016] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND AND PURPOSE KCNQ-encoded voltage-dependent potassium channels (Kv 7) are involved in the regulation of vascular tone. In this study we evaluated the influence of Kv 7 channel activation on smooth muscle relaxation in rat penile arteries and corpus cavernosum from normal and spontaneously hypertensive, heart failure-prone (SHHF) rats - a rat model of human metabolic syndrome. EXPERIMENTAL APPROACH Quantitative PCR and immunohistochemistry were used to determine the expression of KCNQ isoforms in penile tissue. Isometric tension was measured in intracavernous arterial rings and corpus cavernosum strips isolated from normal and SHHF rats. KEY RESULTS Transcripts for KCNQ3, KCNQ4 and KCNQ5 were detected in penile arteries and corpus cavernosum. KCNQ1 was only found in corpus cavernosum. Immunofluorescence signals to Kv 7.4 and Kv 7.5 were found in penile arteries, penile veins and corpus cavernosum. The Kv 7.2-7.5 activators, ML213 and BMS204352, relaxed pre-contracted penile arteries and corpus cavernosum independently of nitric oxide synthase or endothelium-derived hyperpolarization. Relaxations to sildenafil, a PDE5 inhibitor, and sodium nitroprusside (SNP), an nitric oxide donor, were reduced by blocking Kv 7 channels with linopirdine in penile arteries and corpus cavernosum. In SHHF rat penile arteries and corpus cavernosum, relaxations to ML213 and BMS204352 were attenuated, and the blocking effect of linopirdine on sildenafil-induced and SNP-induced relaxations reduced. KCNQ3, KCNQ4 and KCNQ5 were down-regulated, and KCNQ1 was up-regulated in corpus cavernosum from SHHF rats. KCNQ1-5 transcripts remained unchanged in penile arteries from SHHF rats. CONCLUSIONS AND IMPLICATIONS These data suggest that Kv 7 channels play a role in erectile function and contribute to the pathophysiology of erectile dysfunction, an early indicator of cardiovascular disease.
Collapse
Affiliation(s)
- T A Jepps
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - S P Olesen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - I A Greenwood
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,The Vascular Biology Research Centre, Institute of Cardiovascular and Cell Sciences, St George's, London, UK
| | - T Dalsgaard
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
33
|
Hannigan KI, Large RJ, Bradley E, Hollywood MA, Sergeant GP, McHale NG, Thornbury KD. Effect of a novel BKCa opener on BKCa currents and contractility of the rabbit corpus cavernosum. Am J Physiol Cell Physiol 2016; 310:C284-92. [DOI: 10.1152/ajpcell.00273.2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 11/23/2015] [Indexed: 11/22/2022]
Abstract
Large-conductance Ca2+-activated K+ (BKCa) channels are thought to play a key role in the regulation of corpus cavernosum smooth muscle (CCSM) excitability. Few BKCa channel openers have been accepted for clinical development. The effect of the novel BKCa channel opener GoSlo-SR5-130 on electrical activity in isolated rabbit CCSM cells and mechanical activity in strips of rabbit CCSM was examined. Single-channel currents were observed in inside-out patches. These channels were sensitive to Ca2+, blocked by penitrem A, and had a conductance of 291 ± 20 pS ( n = 7). In the presence of GoSlo-SR5-130, the number of open BKCa channels increased. Using voltage-ramp protocols, GoSlo-SR5-130 caused currents to activate at more negative potentials in a concentration-dependent manner, shifting the half-maximal activation voltage potential to the left on the voltage axis. Therefore, BKCa channels were open within the physiological range of membrane potentials in the presence of GoSlo-SR5-130. GoSlo-SR5-130 also resulted in an increase in the activity of spontaneous transient outward currents in myocytes isolated from CCSM, and this effect was reversed by iberiotoxin. In current-clamp mode, GoSlo-SR5-130 hyperpolarized the cell membrane. Isometric tension recording of strips of rabbit corpus cavernosum showed that GoSlo-SR5-130 inhibited spontaneous contractions in a concentration-dependent manner. This effect was reversed in the presence of iberiotoxin, suggesting that GoSlo-SR5-130 exerts its effect through BKCa channels. These findings suggest that GoSlo-SR5-130 is an effective tool for the study of BKCa channels and that these channels can modulate CCSM activity and are possible targets for the treatment of erectile dysfunction.
Collapse
Affiliation(s)
- K. I. Hannigan
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - R. J. Large
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - E. Bradley
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - M. A. Hollywood
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - G. P. Sergeant
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - N. G. McHale
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - K. D. Thornbury
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| |
Collapse
|
34
|
Zemen BG, Lai MH, Whitt JP, Khan Z, Zhao G, Meredith AL. Generation of Kcnma1fl-tdTomato, a conditional deletion of the BK channel α subunit in mouse. Physiol Rep 2015; 3:e12612. [PMID: 26537348 PMCID: PMC4673641 DOI: 10.14814/phy2.12612] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 10/09/2015] [Accepted: 10/13/2015] [Indexed: 11/24/2022] Open
Abstract
BK large conductance calcium-activated K(+) channels (KC a1.1) are expressed widely across many tissues, contributing to systemic regulation of cardiovascular, neurological, and other specialized physiological functions. The pore-forming α subunit is encoded by the Kcnma1 gene, originally named mSlo1 in mouse and slowpoke in Drosophila. Global deletion in mouse (Kcnma1(-/-)) produces a plethora of defects in neuron and muscle excitability, as well as other phenotypes related to channel function in nonexcitable cells. While homozygous null mice are viable, the ubiquitous loss of BK function has complicated the interpretation of phenotypes involving the interaction of multiple cell types which independently express BK channels. Here, we report the generation of a targeted allele for conditional inactivation of Kcnma1 using the Cre-loxP system (Kcnma1(fl)-tdTomato). Cre-mediated recombination generates a null allele, and BK currents were not detectable in neurons and muscle cells from Nestin-Cre; Kcnma1(fl/fl) and SM22α-Cre; Kcnma1(fl/fl) mice, respectively. tdTomato expression was detected in Cre-expressing tissues, but not in Cre-negative controls. These data demonstrate the utility of Kcnma1(fl)-tdTomato for conditional deletion of the BK channel, facilitating the understanding of tissue-specific contributions to physiological function in vivo.
Collapse
Affiliation(s)
- Betsir G Zemen
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Michael H Lai
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Joshua P Whitt
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Zulqarnain Khan
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Guiling Zhao
- Center of BioMedical Engineering and Technology and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| |
Collapse
|
35
|
Toro L, Li M, Zhang Z, Singh H, Wu Y, Stefani E. MaxiK channel and cell signalling. Pflugers Arch 2014; 466:875-86. [PMID: 24077696 DOI: 10.1007/s00424-013-1359-0] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 09/09/2013] [Accepted: 09/10/2013] [Indexed: 01/23/2023]
Abstract
The large-conductance Ca2+- and voltage-activated K+ (MaxiK, BK, BKCa, Slo1, KCa1.1) channel role in cell signalling is becoming apparent as we learn how the channel interacts with a multiplicity of proteins not only at the plasma membrane but also in intracellular organelles including the endoplasmic reticulum, nucleus, and mitochondria. In this review, we focus on the interactions of MaxiK channels with seven-transmembrane G protein-coupled receptors and discuss information suggesting that, the channel big C-terminus may act as the nucleus of signalling molecules including kinases relevant for cell death and survival. Increasing evidence indicates that the channel is able to associate with a variety of receptors including β-adrenergic receptors, G protein-coupled estrogen receptors, acetylcholine receptors, thromboxane A2 receptors, and angiotensin II receptors, which highlights the varied functions that the channel has (or may have) not only in regulating contraction/relaxation of muscle cells or neurotransmission in the brain but also in cell metabolism, proliferation, migration, and gene expression. In line with this view, MaxiK channels have been implicated in obesity and in brain, prostate, and mammary cancers. A better understanding on the molecular mechanisms underlying or triggered by MaxiK channel abnormalities like overexpression in certain cancers may lead to new therapeutics to prevent devastating diseases.
Collapse
|
36
|
Sung HH, Choo SH, Han DH, Chae MR, Kang SJ, Park CS, So I, Park JK, Lee SW. Effect of the novel BKCa channel opener LDD175 on the modulation of corporal smooth muscle tone. J Sex Med 2014; 12:29-38. [PMID: 25385091 DOI: 10.1111/jsm.12744] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
INTRODUCTION The BKCa channel has been reported to play an important role in erectile function. Recently, novel BKCa channel activator, LDD175, was introduced. AIM This study aims to investigate whether LDD175 relaxes corporal smooth muscle (CSM) via BKCa channel activation. METHODS After isolation of CSM strip from a male rabbit model, contraction studies using organ bath was performed. Isolating human tissue and cell cultures, electrophysiological studies were done via whole-cell patch-clamp recording. MAIN OUTCOME MEASURES Vasodilatory effects of LDD175 were evaluated by cumulative addition ranging from 10(-7) to 10(-4) M in corpus cavernosal strips after precontraction with 10(-5) M phenylephrine via organ bath system. Using cultured human CSM cells, patch-clamp recording was performed. Erectile function was measured by in vivo rat cavernous nerve stimulation. RESULTS LDD175 caused an endothelium-independent relaxation of corporal tissues, and this effect was abolished by pretreatment with iberiotoxin. The relaxation effect of 10(-4) M LDD175 was greater than that of 10(-6) M udenafil (54.0 ± 3.1% vs. 34.5 ± 3.9%, P < 0.05); 10(-5) M LDD175 with 10(-6) M udenafil caused a greater relaxation effect on strips than 10(-5) M LDD175 or 10(-6) M udenafil alone (50.7%, 34.1%, vs. 20.7%, respectively, P < 0.001). In patch-clamp recordings, LDD175 increased K(+) currents in a dose-dependent manner, and washout of LDD175 or the addition of iberiotoxin fully reversed the increase. Intravenous LDD175 improved erectile function measured by area under the curve (AUC) of the intracavernosal pressure (ICP)/arterial blood pressure (ABP) ratio (1,612.1 ± 135.6 vs. 1,093.7 ± 123.1, P < 0.05). There was no difference between 10 mg/kg LDD175 and 1 mg/kg udenafil regarding maximal ICP, maximal ICP/ABP ratio, and the AUC of the ICP/ABP ratio (P > 0.05). CONCLUSIONS LDD175 leads to an endothelium-independent relaxation of erectile tissue, primarily through the opening of BKCa channels. The results suggest that LDD175 might be a new candidate treatment for erectile dysfunction.
Collapse
Affiliation(s)
- Hyun Hwan Sung
- The Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, Korea
| | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Bentzen BH, Olesen SP, Rønn LCB, Grunnet M. BK channel activators and their therapeutic perspectives. Front Physiol 2014; 5:389. [PMID: 25346695 PMCID: PMC4191079 DOI: 10.3389/fphys.2014.00389] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 09/19/2014] [Indexed: 01/05/2023] Open
Abstract
The large conductance calcium- and voltage-activated K+ channel (KCa1.1, BK, MaxiK) is ubiquitously expressed in the body, and holds the ability to integrate changes in intracellular calcium and membrane potential. This makes the BK channel an important negative feedback system linking increases in intracellular calcium to outward hyperpolarizing potassium currents. Consequently, the channel has many important physiological roles including regulation of smooth muscle tone, neurotransmitter release and neuronal excitability. Additionally, cardioprotective roles have been revealed in recent years. After a short introduction to the structure, function and regulation of BK channels, we review the small organic molecules activating BK channels and how these tool compounds have helped delineate the roles of BK channels in health and disease.
Collapse
Affiliation(s)
- Bo H Bentzen
- Department of Biomedical Sciences, Faculty of Health Sciences, Danish Arrhythmia Research Centre, University of Copenhagen Copenhagen, Denmark ; Acesion Pharma Copenhagen, Denmark
| | - Søren-Peter Olesen
- Department of Biomedical Sciences, Faculty of Health Sciences, Danish Arrhythmia Research Centre, University of Copenhagen Copenhagen, Denmark
| | | | - Morten Grunnet
- Acesion Pharma Copenhagen, Denmark ; H. Lundbeck A/S Copenhagen, Denmark
| |
Collapse
|
38
|
Ge L, Hoa NT, Wilson Z, Arismendi-Morillo G, Kong XT, Tajhya RB, Beeton C, Jadus MR. Big Potassium (BK) ion channels in biology, disease and possible targets for cancer immunotherapy. Int Immunopharmacol 2014; 22:427-43. [PMID: 25027630 PMCID: PMC5472047 DOI: 10.1016/j.intimp.2014.06.040] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 06/27/2014] [Accepted: 06/30/2014] [Indexed: 11/18/2022]
Abstract
The Big Potassium (BK) ion channel is commonly known by a variety of names (Maxi-K, KCNMA1, slo, stretch-activated potassium channel, KCa1.1). Each name reflects a different physical property displayed by this single ion channel. This transmembrane channel is found on nearly every cell type of the body and has its own distinctive roles for that tissue type. The BKα channel contains the pore that releases potassium ions from intracellular stores. This ion channel is found on the cell membrane, endoplasmic reticulum, Golgi and mitochondria. Complex splicing pathways produce different isoforms. The BKα channels can be phosphorylated, palmitoylated and myristylated. BK is composed of a homo-tetramer that interacts with β and γ chains. These accessory proteins provide a further modulating effect on the functions of BKα channels. BK channels play important roles in cell division and migration. In this review, we will focus on the biology of the BK channel, especially its role, and its immune response towards cancer. Recent proteomic studies have linked BK channels with various proteins. Some of these interactions offer further insight into the role that BK channels have with cancers, especially with brain tumors. This review shows that BK channels have a complex interplay with intracellular components of cancer cells and still have plenty of secrets to be discovered.
Collapse
Affiliation(s)
- Lisheng Ge
- Research Service, VA Long Beach Healthcare System, 5901 E. 7th Street, Long Beach, CA 90822, USA
| | - Neil T Hoa
- Research Service, VA Long Beach Healthcare System, 5901 E. 7th Street, Long Beach, CA 90822, USA
| | - Zechariah Wilson
- Research Service, VA Long Beach Healthcare System, 5901 E. 7th Street, Long Beach, CA 90822, USA
| | | | - Xiao-Tang Kong
- Department of Neuro-Surgery, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Rajeev B Tajhya
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Christine Beeton
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Martin R Jadus
- Research Service, VA Long Beach Healthcare System, 5901 E. 7th Street, Long Beach, CA 90822, USA; Pathology and Laboratory Medicine Service, VA Long Beach Healthcare System, 5901 E. 7th Street, Long Beach, CA 90822, USA; Neuro-Oncology Program, Chao Comprehensive Cancer Center, University of California, Irvine, Orange, CA 92868, USA; Pathology and Laboratory Medicine, Med Sci I, University of California, Irvine, CA 92697, USA.
| |
Collapse
|
39
|
Lai MH, Wu Y, Gao Z, Anderson ME, Dalziel JE, Meredith AL. BK channels regulate sinoatrial node firing rate and cardiac pacing in vivo. Am J Physiol Heart Circ Physiol 2014; 307:H1327-38. [PMID: 25172903 DOI: 10.1152/ajpheart.00354.2014] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Large-conductance Ca(2+)- and voltage-activated K(+) (BK) channels play prominent roles in shaping muscle and neuronal excitability. In the cardiovascular system, BK channels promote vascular relaxation and protect against ischemic injury. Recently, inhibition of BK channels has been shown to lower heart rate in intact rodents and isolated hearts, suggesting a novel role in heart function. However, the underlying mechanism is unclear. In the present study, we recorded ECGs from mice injected with paxilline (PAX), a membrane-permeable BK channel antagonist, and examined changes in cardiac conduction. ECGs revealed a 19 ± 4% PAX-induced reduction in heart rate in wild-type but not BK channel knockout (Kcnma1(-/-)) mice. The heart rate decrease was associated with slowed cardiac pacing due to elongation of the sinus interval. Action potential firing recorded from isolated sinoatrial node cells (SANCs) was reduced by 55 ± 15% and 28 ± 9% by application of PAX (3 μM) and iberiotoxin (230 nM), respectively. Furthermore, baseline firing rates from Kcnma1(-/-) SANCs were 33% lower than wild-type SANCs. The slowed firing upon BK current inhibition or genetic deletion was due to lengthening of the diastolic depolarization phase of the SANC action potential. Finally, BK channel immunoreactivity and PAX-sensitive currents were identified in SANCs with HCN4 expression and pacemaker current, respectively, and BK channels cloned from SANCs recapitulated similar activation as the PAX-sensitive current. Together, these data localize BK channels to SANCs and demonstrate that loss of BK current decreases SANC automaticity, consistent with slowed sinus pacing after PAX injection in vivo. Furthermore, these findings suggest BK channels are potential therapeutic targets for disorders of heart rate.
Collapse
Affiliation(s)
- Michael H Lai
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland; Fischell Department of Bioengineering, University of Maryland, College Park, Maryland
| | - Yuejin Wu
- Department of Internal Medicine and the François M. Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa
| | - Zhan Gao
- Department of Internal Medicine and the François M. Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa
| | - Mark E Anderson
- Department of Internal Medicine and the François M. Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa; Department of Physiology and Molecular Biophysics, University of Iowa, Iowa City, Iowa; and
| | - Julie E Dalziel
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland; Fischell Department of Bioengineering, University of Maryland, College Park, Maryland;
| |
Collapse
|
40
|
Shipston MJ. S-acylation dependent post-translational cross-talk regulates large conductance calcium- and voltage- activated potassium (BK) channels. Front Physiol 2014; 5:281. [PMID: 25140154 PMCID: PMC4122160 DOI: 10.3389/fphys.2014.00281] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 07/09/2014] [Indexed: 01/14/2023] Open
Abstract
Mechanisms that control surface expression and/or activity of large conductance calcium-activated potassium (BK) channels are important determinants of their (patho)physiological function. Indeed, BK channel dysfunction is associated with major human disorders ranging from epilepsy to hypertension and obesity. S-acylation (S-palmitoylation) represents a major reversible, post-translational modification controlling the properties and function of many proteins including ion channels. Recent evidence reveals that both pore-forming and regulatory subunits of BK channels are S-acylated and control channel trafficking and regulation by AGC-family protein kinases. The pore-forming α-subunit is S-acylated at two distinct sites within the N- and C-terminus, each site being regulated by different palmitoyl acyl transferases (zDHHCs) and acyl thioesterases (APTs). S-acylation of the N-terminus controls channel trafficking and surface expression whereas S-acylation of the C-terminal domain determines regulation of channel activity by AGC-family protein kinases. S-acylation of the regulatory β4-subunit controls ER exit and surface expression of BK channels but does not affect ion channel kinetics at the plasma membrane. Furthermore, a significant number of previously identified BK-channel interacting proteins have been shown, or are predicted to be, S-acylated. Thus, the BK channel multi-molecular signaling complex may be dynamically regulated by this fundamental post-translational modification and thus S-acylation likely represents an important determinant of BK channel physiology in health and disease.
Collapse
Affiliation(s)
- Michael J Shipston
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh Edinburgh, UK
| |
Collapse
|
41
|
Shelton EL, Ector G, Galindo CL, Hooper CW, Brown N, Wilkerson I, Pfaltzgraff ER, Paria BC, Cotton RB, Stoller JZ, Reese J. Transcriptional profiling reveals ductus arteriosus-specific genes that regulate vascular tone. Physiol Genomics 2014; 46:457-66. [PMID: 24790087 DOI: 10.1152/physiolgenomics.00171.2013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Failure of the ductus arteriosus (DA) to close at birth can lead to serious complications. Conversely, certain profound congenital cardiac malformations require the DA to be patent until corrective surgery can be performed. In each instance, clinicians have a very limited repertoire of therapeutic options at their disposal - indomethacin or ibuprofen to close a patent DA (PDA) and prostaglandin E1 to maintain patency of the DA. Neither treatment is specific to the DA and both may have deleterious off-target effects. Therefore, more therapeutic options specifically targeted to the DA should be considered. We hypothesized the DA possesses a unique genetic signature that would set it apart from other vessels. A microarray was used to compare the genetic profiles of the murine DA and ascending aorta (AO). Over 4,000 genes were differentially expressed between these vessels including a subset of ion channel-related genes. Specifically, the alpha and beta subunits of large-conductance calcium-activated potassium (BKCa) channels are enriched in the DA. Gain- and loss-of-function studies showed inhibition of BKCa channels caused the DA to constrict, while activation caused DA relaxation even in the presence of O2. This study identifies subsets of genes that are enriched in the DA that may be used to develop DA-specific drugs. Ion channels that regulate DA tone, including BKCa channels, are promising targets. Specifically, BKCa channel agonists like NS1619 maintain DA patency even in the presence of O2 and may be clinically useful.
Collapse
Affiliation(s)
- Elaine L Shelton
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee;
| | - Gerren Ector
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Cristi L Galindo
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee; and
| | - Christopher W Hooper
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Naoko Brown
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Irene Wilkerson
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Elise R Pfaltzgraff
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Bibhash C Paria
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Robert B Cotton
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Jason Z Stoller
- Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Jeff Reese
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee; Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee
| |
Collapse
|
42
|
Tar MT, Martinez LR, Nosanchuk JD, Davies KP. The effect of methamphetamine on an animal model of erectile function. Andrology 2014; 2:531-6. [PMID: 24706617 DOI: 10.1111/j.2047-2927.2014.00212.x] [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: 08/15/2013] [Revised: 01/27/2014] [Accepted: 02/26/2014] [Indexed: 12/01/2022]
Abstract
In the US methamphetamine is considered a first-line treatment for attention-deficit hyperactivity disorder. It is also a common drug of abuse. Reports in patients and abusers suggest its use results in impotence. The efficacy of phosphodiesterase-5 inhibitors (PDE5i) to restore erectile function in these patient groups also has not been determined. In these studies, we determined if the rat is a suitable animal model for the physiological effects of methamphetamine on erectile function, and if a PDE5i (tadalafil) has an effect on erectile function following methamphetamine treatment. In acute phase studies, erectile function was measured in male Sprague-Dawley rats, before and after administration of 10 mg/kg methamphetamine i.p. Chronically treated animals received escalating doses of methamphetamine [2.5 mg/kg (1st week), 5 mg/kg (2nd week), and 10 mg/kg (3rd week)] i.p. daily for 3 weeks and erectile function compared with untreated controls. The effect of co-administration of tadalafil was also investigated in rats acutely and chronically treated with methamphetamine. Erectile function was determined by measuring the intracorporal pressure/blood pressure ratio (ICP/BP) following cavernous nerve stimulation. In both acute and chronic phase studies, we observed a significant increase in the rates of spontaneous erections after methamphetamine administration. In addition, following stimulation of the cavernous nerve at 4 and 6 mA, there was a significant decrease in the ICP/BP ratio (approximately 50%), indicative of impaired erectile function. Tadalafil treatment reversed this effect. In chronically treated animals, the ICP/BP ratio following 4 and 6 mA stimulation decreased by approximately 50% compared with untreated animals and erectile dysfunction (ED) was also reversed by tadalafil. Overall, our data suggest that the rat is a suitable animal model to study the physiological effect of methamphetamine on erectile function. Our work also provides a rationale for treating patients that report ED associated with therapeutics-containing methamphetamine or amphetamine with PDE5i.
Collapse
Affiliation(s)
- M T Tar
- Department of Urology, Albert Einstein College of Medicine, Bronx, NY, USA
| | | | | | | |
Collapse
|
43
|
Yi F, Wang H, Chai Q, Wang X, Shen WK, Willis MS, Lee HC, Lu T. Regulation of large conductance Ca2+-activated K+ (BK) channel β1 subunit expression by muscle RING finger protein 1 in diabetic vessels. J Biol Chem 2014; 289:10853-10864. [PMID: 24570002 DOI: 10.1074/jbc.m113.520940] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The large conductance Ca(2+)-activated K(+) (BK) channel, expressed abundantly in vascular smooth muscle cells (SMCs), is a key determinant of vascular tone. BK channel activity is tightly regulated by its accessory β1 subunit (BK-β1). However, BK channel function is impaired in diabetic vessels by increased ubiquitin/proteasome-dependent BK-β1 protein degradation. Muscle RING finger protein 1 (MuRF1), a muscle-specific ubiquitin ligase, is implicated in many cardiac and skeletal muscle diseases. However, the role of MuRF1 in the regulation of vascular BK channel and coronary function has not been examined. In this study, we hypothesized that MuRF1 participated in BK-β1 proteolysis, leading to the down-regulation of BK channel activation and impaired coronary function in diabetes. Combining patch clamp and molecular biological approaches, we found that MuRF1 expression was enhanced, accompanied by reduced BK-β1 expression, in high glucose-cultured human coronary SMCs and in diabetic vessels. Knockdown of MuRF1 by siRNA in cultured human SMCs attenuated BK-β1 ubiquitination and increased BK-β1 expression, whereas adenoviral expression of MuRF1 in mouse coronary arteries reduced BK-β1 expression and diminished BK channel-mediated vasodilation. Physical interaction between the N terminus of BK-β1 and the coiled-coil domain of MuRF1 was demonstrated by pulldown assay. Moreover, MuRF1 expression was regulated by NF-κB. Most importantly, pharmacological inhibition of proteasome and NF-κB activities preserved BK-β1 expression and BK-channel-mediated coronary vasodilation in diabetic mice. Hence, our results provide the first evidence that the up-regulation of NF-κB-dependent MuRF1 expression is a novel mechanism that leads to BK channelopathy and vasculopathy in diabetes.
Collapse
Affiliation(s)
- Fu Yi
- Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905; Department of Cardiology, Xijing Hospital, Fourth Military Medical University, Xian 710032, China
| | - Huan Wang
- Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Qiang Chai
- Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Xiaoli Wang
- Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Win-Kuang Shen
- Department of Internal Medicine, Mayo Clinic, Scottsdale, Arizona 85259
| | - Monte S Willis
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Hon-Chi Lee
- Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905
| | - Tong Lu
- Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905.
| |
Collapse
|
44
|
Hoshi T, Pantazis A, Olcese R. Transduction of voltage and Ca2+ signals by Slo1 BK channels. Physiology (Bethesda) 2013; 28:172-89. [PMID: 23636263 DOI: 10.1152/physiol.00055.2012] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Large-conductance Ca2+ -and voltage-gated K+ channels are activated by an increase in intracellular Ca2+ concentration and/or depolarization. The channel activation mechanism is well described by an allosteric model encompassing the gate, voltage sensors, and Ca2+ sensors, and the model is an excellent framework to understand the influences of auxiliary β and γ subunits and regulatory factors such as Mg2+. Recent advances permit elucidation of structural correlates of the biophysical mechanism.
Collapse
Affiliation(s)
- T Hoshi
- Department of Physiology, The University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | | | | |
Collapse
|
45
|
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.
Collapse
Affiliation(s)
- Ken Takahashi
- Department of Cardiovascular Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
| | | |
Collapse
|
46
|
Irnaten M, Barry RC, Wallace DM, Docherty NG, Quill B, Clark AF, O'Brien CJ. Elevated maxi-K+ ion channel current in glaucomatous lamina cribrosa cells. Exp Eye Res 2013; 115:224-9. [DOI: 10.1016/j.exer.2013.07.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 07/03/2013] [Accepted: 07/19/2013] [Indexed: 10/26/2022]
|
47
|
Regulation of large conductance calcium- and voltage-activated potassium (BK) channels by S-palmitoylation. Biochem Soc Trans 2013; 41:67-71. [PMID: 23356260 DOI: 10.1042/bst20120226] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BK (large conductance calcium- and voltage-activated potassium) channels are important determinants of physiological control in the nervous, endocrine and vascular systems with channel dysfunction associated with major disorders ranging from epilepsy to hypertension and obesity. Thus the mechanisms that control channel surface expression and/or activity are important determinants of their (patho)physiological function. BK channels are S-acylated (palmitoylated) at two distinct sites within the N- and C-terminus of the pore-forming α-subunit. Palmitoylation of the N-terminus controls channel trafficking and surface expression whereas palmitoylation of the C-terminal domain determines regulation of channel activity by AGC-family protein kinases. Recent studies are beginning to reveal mechanistic insights into how palmitoylation controls channel trafficking and cross-talk with phosphorylation-dependent signalling pathways. Intriguingly, each site of palmitoylation is regulated by distinct zDHHCs (palmitoyl acyltransferases) and APTs (acyl thioesterases). This supports that different mechanisms may control substrate specificity by zDHHCs and APTs even within the same target protein. As palmitoylation is dynamically regulated, this fundamental post-translational modification represents an important determinant of BK channel physiology in health and disease.
Collapse
|
48
|
Lee BC, Kim HJ, Park SH, Phuong TTT, Kang TM, Park CS. Development of cell-based assay system that utilizes a hyperactive channel mutant for high-throughput screening of BKCa channel modulators. J Biotechnol 2013; 167:41-6. [DOI: 10.1016/j.jbiotec.2013.06.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2013] [Revised: 05/22/2013] [Accepted: 06/11/2013] [Indexed: 01/16/2023]
|
49
|
González-Corrochano R, La Fuente J, Cuevas P, Fernández A, Chen M, Sáenz de Tejada I, Angulo J. Ca2+ -activated K+ channel (KCa) stimulation improves relaxant capacity of PDE5 inhibitors in human penile arteries and recovers the reduced efficacy of PDE5 inhibition in diabetic erectile dysfunction. Br J Pharmacol 2013; 169:449-61. [PMID: 23441682 PMCID: PMC3651669 DOI: 10.1111/bph.12143] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 01/31/2013] [Accepted: 02/17/2013] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND AND PURPOSE We have evaluated the influence of calcium-activated potassium channels (KCa ) activation on cGMP-mediated relaxation in human penile tissues from non-diabetic and diabetic patients, and on the effects of PDE5 inhibitors on erectile responses in control and diabetic rats. EXPERIMENTAL APPROACH Cavernosal tissues were collected from organ donors and from patients with erectile dysfunction (ED). Relaxations of corpus cavernosum strips (HCC) and penile resistance arteries (HPRA) obtained from these specimens were evaluated. Intracavernosal pressure (ICP) increases to cavernosal nerve electrical stimulation were determined in anaesthetized diabetic and non-diabetic rats. KEY RESULTS Concentration-dependent vasodilation to the PDE5 inhibitor, sildenafil, in HPRA was sensitive to endothelium removal, NO/cGMP pathway inhibition and KCa blockade. Accordingly, activation of KCa with NS-8 (10 μM) significantly potentiated sildenafil-induced relaxations in HPRA (EC50 0.49 ± 0.22 vs. 5.21 ± 0.63 μM). In HCC, sildenafil-induced relaxation was unaffected by KCa blockade or activation. Potentiating effects in HPRA were reproduced with an alternative PDE5 inhibitor (tadalafil) and KCa activator (NS1619) and prevented by removing the endothelium. Large-conductance KCa (BK) and intermediate-conductance KCa (IK) contribute to NS-8-induced effects and were immunodetected in human and rat penile arteries. NS-8 potentiated sildenafil-induced enhancement of erectile responses in rats. Activation of KCa recovered the impaired relaxation to sildenafil in diabetic HPRA while sildenafil completely reversed diabetes-induced ED in rats only when combined with KCa activation. CONCLUSIONS AND IMPLICATIONS Activation of KCa improves vasodilatory capacity of PDE5 inhibitors in diabetic and non-diabetic HPRA, resulting in the recovery of erectile function in diabetic rats. These results suggest a therapeutic potential for KCa activation in diabetic ED.
Collapse
Affiliation(s)
- R González-Corrochano
- Servicio de Histología-Investigación, Instituto Ramón y Cajal de Investigación Sanitaria, Hospital Universitario Ramón y Cajal, Madrid, Spain
| | | | | | | | | | | | | |
Collapse
|
50
|
Greenwood H, Bartlett DB. Meeting report: British Society for Research on Ageing (BSRA) annual scientific meeting 2012, Aston University, Birmingham, 3rd to 4th July 2012. LONGEVITY & HEALTHSPAN 2013; 2:6. [PMID: 24472617 PMCID: PMC3922932 DOI: 10.1186/2046-2395-2-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 03/20/2013] [Indexed: 11/23/2022]
Abstract
The focus of the British Society for Research on Ageing (BSRA) annual scientific meeting 2012 was aging mechanisms and mitigants. The themes covered included epigenetics, stem cells and regeneration, aging pathways and molecules, the aging bladder and bowel, as well as updates from the New Dynamics of Ageing (NDA) programme. The topics incorporated new directions for staple aging research in caloric restriction (CR), inflammation, immunesenescence, neurodegeneration, homeostasis and stress resistance, as well as newer research areas such as bioengineering of tissues, including the internal anal sphincter and thymus.
Collapse
Affiliation(s)
- Hannah Greenwood
- MRC-ARUK Centre for Musculoskeletal Ageing Research, School of Immunity and Infection, University of Birmingham, Birmingham, B15 2TT, UK.
| | | |
Collapse
|