1
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Kshatri A, Rivero-Pérez B, Giraldez T. Subunit-specific inhibition of BK channels by piperine. Biophys J 2023:S0006-3495(23)00558-1. [PMID: 37700524 DOI: 10.1016/j.bpj.2023.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Revised: 08/03/2023] [Accepted: 09/08/2023] [Indexed: 09/14/2023] Open
Abstract
Piperine is the principal alkaloid present in black pepper and is well-known for its diverse pharmacological effects, including inhibition of different ion channels. Large conductance Ca2+-activated K+ channels (BK) are widely expressed across several tissues and play a vital role in many physiological functions. In this study, we investigated the pharmacological effects of piperine on various BK channel subunit compositions (BKα, BKαβ1,4, BKαγ1,3) expressed in HEK293T cells. Piperine in zero Ca2+ reversibly inhibited currents from the pore-forming BKα channels in a dose-dependent manner with a half-maximal inhibitory concentration (IC50) of 4.8 μM. Elevating the internal Ca2+ concentration from 0 to 100 μM significantly attenuated the inhibitory effects of piperine on BKα channels. The mutation G311S in the pore domain failed to alter the modulatory effects of piperine, whereas deletion of the entire cytoplasmic domain from BKα channels ablated its inhibitory effects. Addition of either BKβ1 or β4 regulatory subunits did not alter the efficacy of piperine on BKα channels. Interestingly, co-expression of either BKγ1 or BKγ3 subunits greatly diminished the ability of piperine to inhibit BKα channels. Our findings demonstrate that piperine is a potent natural modulator of BKα/BKαβ1,4 subunits but not BKαγ1,3 subunits. The mechanism of piperine modulation appeared to be allosteric and differs from that of other BK pore blockers (paxilline, peptide toxins, and quaternary ammonium compounds). Together, our results unravel the potential of piperine to inhibit BK channels, providing a new tool to explore mechanisms underlying the effects of regulatory subunits.
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Affiliation(s)
- Aravind Kshatri
- Department of Basic Medical Sciences, Medical School, Universidad de La Laguna, Tenerife, Spain; Instituto de Tecnologias Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Belinda Rivero-Pérez
- Department of Basic Medical Sciences, Medical School, Universidad de La Laguna, Tenerife, Spain; Instituto de Tecnologias Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Teresa Giraldez
- Department of Basic Medical Sciences, Medical School, Universidad de La Laguna, Tenerife, Spain; Instituto de Tecnologias Biomedicas, Universidad de La Laguna, Tenerife, Spain.
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2
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Kuzmenkov AI, Gigolaev AM, Pinheiro-Junior EL, Peigneur S, Tytgat J, Vassilevski AA. Methionine-isoleucine dichotomy at a key position in scorpion toxins inhibiting voltage-gated potassium channels. Toxicon 2023; 231:107181. [PMID: 37301298 DOI: 10.1016/j.toxicon.2023.107181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 06/06/2023] [Accepted: 06/06/2023] [Indexed: 06/12/2023]
Abstract
Previous studies have identified some key amino acid residues in scorpion toxins blocking potassium channels. In particular, the most numerous toxins belonging to the α-KTx family and affecting voltage-gated potassium channels (KV) present a conserved K-C-X-N motif in the C-terminal half of their sequence. Here, we show that the X position of this motif is almost always occupied by either methionine or isoleucine. We compare the activity of three pairs of peptides that differ just by this residue on a panel of KV1 channels and find that toxins bearing methionine affect preferentially KV1.1 and 1.6 isoforms. The refined K-C-M/I-N motif stands out as the principal structural element of α-KTx conferring high affinity and selectivity to KV channels.
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Affiliation(s)
- Alexey I Kuzmenkov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia.
| | - Andrei M Gigolaev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia
| | | | - Steve Peigneur
- Toxicology and Pharmacology, KU Leuven, Leuven, 3000, Belgium
| | - Jan Tytgat
- Toxicology and Pharmacology, KU Leuven, Leuven, 3000, Belgium
| | - Alexander A Vassilevski
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia.
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3
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Sancho M, Kyle BD. The Large-Conductance, Calcium-Activated Potassium Channel: A Big Key Regulator of Cell Physiology. Front Physiol 2021; 12:750615. [PMID: 34744788 PMCID: PMC8567177 DOI: 10.3389/fphys.2021.750615] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/29/2021] [Indexed: 12/01/2022] Open
Abstract
Large-conductance Ca2+-activated K+ channels facilitate the efflux of K+ ions from a variety of cells and tissues following channel activation. It is now recognized that BK channels undergo a wide range of pre- and post-translational modifications that can dramatically alter their properties and function. This has downstream consequences in affecting cell and tissue excitability, and therefore, function. While finding the “silver bullet” in terms of clinical therapy has remained elusive, ongoing research is providing an impressive range of viable candidate proteins and mechanisms that associate with and modulate BK channel activity, respectively. Here, we provide the hallmarks of BK channel structure and function generally, and discuss important milestones in the efforts to further elucidate the diverse properties of BK channels in its many forms.
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Affiliation(s)
- Maria Sancho
- Department of Pharmacology, University of Vermont, Burlington, VT, United States
| | - Barry D Kyle
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
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4
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Abstract
K+ channels enable potassium to flow across the membrane with great selectivity. There are four K+ channel families: voltage-gated K (Kv), calcium-activated (KCa), inwardly rectifying K (Kir), and two-pore domain potassium (K2P) channels. All four K+ channels are formed by subunits assembling into a classic tetrameric (4x1P = 4P for the Kv, KCa, and Kir channels) or tetramer-like (2x2P = 4P for the K2P channels) architecture. These subunits can either be the same (homomers) or different (heteromers), conferring great diversity to these channels. They share a highly conserved selectivity filter within the pore but show different gating mechanisms adapted for their function. K+ channels play essential roles in controlling neuronal excitability by shaping action potentials, influencing the resting membrane potential, and responding to diverse physicochemical stimuli, such as a voltage change (Kv), intracellular calcium oscillations (KCa), cellular mediators (Kir), or temperature (K2P).
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5
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Wang X, Xiao Q, Zhu Y, Qi H, Qu D, Yao Y, Jia Y, Guo J, Cheng J, Ji Y, Li G, Tao J. Glycosylation of β1 subunit plays a pivotal role in the toxin sensitivity and activation of BK channels. J Venom Anim Toxins Incl Trop Dis 2021; 27:e20200182. [PMID: 34149831 PMCID: PMC8183112 DOI: 10.1590/1678-9199-jvatitd-2020-0182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Background: The accessory β1 subunits, regulating the pharmacological and biophysical properties of BK channels, always undergo post-translational modifications, especially glycosylation. To date, it remains elusive whether the glycosylation contributes to the regulation of BK channels by β1 subunits. Methods: Herein, we combined the electrophysiological approach with molecular mutations and biochemical manipulation to investigate the function roles of N-glycosylation in β1 subunits. Results: The results show that deglycosylation of β1 subunits through double-site mutations (β1 N80A/N142A or β1 N80Q/N142Q) could significantly increase the inhibitory potency of iberiotoxin, a specific BK channel blocker. The deglycosylated channels also have a different sensitivity to martentoxin, another BK channel modulator with some remarkable effects as reported before. On the contrary to enhancing effects of martentoxin on glycosylated BK channels under the presence of cytoplasmic Ca2+, deglycosylated channels were not affected by the toxin. However, the deglycosylated channels were surprisingly inhibited by martentoxin under the absence of cytoplasmic Ca2+, while the glycosylated channels were not inhibited under this same condition. In addition, wild type BK (α+β1) channels treated with PNGase F also showed the same trend of pharmacological results to the mutants. Similar to this modulation of glycosylation on BK channel pharmacology, the deglycosylated forms of the channels were activated at a faster speed than the glycosylated ones. However, the V1/2 and slope were not changed by the glycosylation. Conclusion: The present study reveals that glycosylation is an indispensable determinant of the modulation of β1-subunit on BK channel pharmacology and its activation. The loss of glycosylation of β1 subunits could lead to the dysfunction of BK channel, resulting in a pathological state.
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Affiliation(s)
- Xiaoli Wang
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China
| | - Qian Xiao
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yudan Zhu
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Hong Qi
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China
| | - Dongxiao Qu
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yu Yao
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China
| | - Yuxiang Jia
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China
| | - Jingkan Guo
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China.,Xinhua Translational Institute for Cancer Pain, Shanghai, China
| | - Jiwei Cheng
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China.,Putuo Clinical Medical School, Anhui Medical University, Shanghai, China
| | - Yonghua Ji
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China.,Xinhua Translational Institute for Cancer Pain, Shanghai, China
| | - Guoyi Li
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China.,Putuo Clinical Medical School, Anhui Medical University, Shanghai, China
| | - Jie Tao
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China.,Putuo Clinical Medical School, Anhui Medical University, Shanghai, China
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6
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Liu X, Tao J, Zhang S, Lan W, Wang C, Ji Y, Cao C. Selective Blockade of Neuronal BK (α + β4) Channels Preventing Epileptic Seizure. J Med Chem 2019; 63:216-230. [DOI: 10.1021/acs.jmedchem.9b01241] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Xinlian Liu
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
- University of Chinese Academy of Science, No. 19A, Yuquan Road, Shijingshan District, Beijing 100049, China
| | - Jie Tao
- Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, 164 Lanxi Road, Putuo District, Shanghai 200062, China
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, 99 Shangda Road,
BaoShan District, Shanghai 200444, China
| | - Shuzhang Zhang
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, 99 Shangda Road,
BaoShan District, Shanghai 200444, China
| | - Wenxian Lan
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Chunxi Wang
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Yonghua Ji
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, 99 Shangda Road,
BaoShan District, Shanghai 200444, China
- Xinhua Hospital (Chongming) Affiliated to Shanghai JiaoTong University School of Medicine, Shanghai Chongming Xinhua Translational Medical Institute for Cancer Pain, 25 Nanmen Port Street, Chongming Branch, Shanghai 202150, China
| | - Chunyang Cao
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
- University of Chinese Academy of Science, No. 19A, Yuquan Road, Shijingshan District, Beijing 100049, China
- Institute of Drug Discovery Technology, Ningbo University, No 818 Fenghua Road, Ningbo, Zhejiang 313211, China
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7
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Gurrola GB, Guijarro JI, Delepierre M, Mendoza RLL, Cid-Uribe JI, Coronas FV, Possani LD. Cn29, a novel orphan peptide found in the venom of the scorpion Centruroides noxius: Structure and function. Toxicon 2019; 167:184-191. [PMID: 31226259 DOI: 10.1016/j.toxicon.2019.06.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 05/22/2019] [Accepted: 06/13/2019] [Indexed: 02/07/2023]
Abstract
A peptide (Cn29) from the venom of the scorpion Centruroides noxius (about 2% of the soluble venom) was purified and its primary and three-dimensional structures were determined. The peptide contains 27 amino acids with primary sequence: LCLSCRGGDYDCRVKGTCENGKCVCGS. The peptide is tightly packed by three disulfide linkages formed between C2-C23, C5-C18 and C12-C25. Since the native peptide was obtained in limited amounts, the full synthetic peptide was prepared using the standard F-moc-based solid phase synthesis method of Merrifield. The native and synthetic peptides were shown to be identical by sequencing, HPLC separation and mass spectrometry. The solution structure of the peptide solved from NMR data shows that it consists of a well-defined N-terminal region without regular secondary structure extending from Leu 1 to Asp 9, followed by a short helical fragment from Tyr10 to Val14 and two short β strands (Thr17-Glu19 and Lys22-Val24). The primary and tertiary structures of Cn29 are different from all other scorpion peptides described in the literature. Transcriptome analysis of RNA obtained from C. noxius confirmed the expression of a gene coding for Cn29 in its venom gland. Initial experiments were conducted to identify its possible function: lethality tests in mice and insects as well as ion-channel binding using in vitro electrophysiological assays. None of the physiological or biological tests displayed any activity for this peptide, which at present is considered to be another orphan peptide found in scorpion venoms. The peptide is thus the first example of a novel structural component present in scorpion venoms.
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Affiliation(s)
- G B Gurrola
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Av, Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, 62210, Mexico
| | - J I Guijarro
- Biological NMR Technological Platform, Institut Pasteur, CNRS UMR3528, Paris, France
| | | | - R L L Mendoza
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Av, Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, 62210, Mexico
| | - J I Cid-Uribe
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Av, Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, 62210, Mexico
| | - F V Coronas
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Av, Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, 62210, Mexico
| | - L D Possani
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Av, Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, 62210, Mexico.
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8
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Bajaj S, Han J. Venom-Derived Peptide Modulators of Cation-Selective Channels: Friend, Foe or Frenemy. Front Pharmacol 2019; 10:58. [PMID: 30863305 PMCID: PMC6399158 DOI: 10.3389/fphar.2019.00058] [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: 06/16/2018] [Accepted: 01/18/2019] [Indexed: 01/31/2023] Open
Abstract
Ion channels play a key role in our body to regulate homeostasis and conduct electrical signals. With the help of advances in structural biology, as well as the discovery of numerous channel modulators derived from animal toxins, we are moving toward a better understanding of the function and mode of action of ion channels. Their ubiquitous tissue distribution and the physiological relevancies of their opening and closing suggest that cation channels are particularly attractive drug targets, and years of research has revealed a variety of natural toxins that bind to these channels and alter their function. In this review, we provide an introductory overview of the major cation ion channels: potassium channels, sodium channels and calcium channels, describe their venom-derived peptide modulators, and how these peptides provide great research and therapeutic value to both basic and translational medical research.
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Affiliation(s)
- Saumya Bajaj
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Jingyao Han
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
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9
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Jiménez-Vargas JM, Possani LD, Luna-Ramírez K. Arthropod toxins acting on neuronal potassium channels. Neuropharmacology 2017; 127:139-160. [PMID: 28941737 DOI: 10.1016/j.neuropharm.2017.09.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 09/13/2017] [Accepted: 09/15/2017] [Indexed: 01/01/2023]
Abstract
Arthropod venoms are a rich mixture of biologically active compounds exerting different physiological actions across diverse phyla and affecting multiple organ systems including the central nervous system. Venom compounds can inhibit or activate ion channels, receptors and transporters with high specificity and affinity providing essential insights into ion channel function. In this review, we focus on arthropod toxins (scorpions, spiders, bees and centipedes) acting on neuronal potassium channels. A brief description of the K+ channels classification and structure is included and a compendium of neuronal K+ channels and the arthropod toxins that modify them have been listed. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Affiliation(s)
- Juana María Jiménez-Vargas
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Avenida Universidad, 2001, Colonia Chamilpa, Apartado Postal 510-3, Cuernavaca 62210, Mexico
| | - Lourival D Possani
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Avenida Universidad, 2001, Colonia Chamilpa, Apartado Postal 510-3, Cuernavaca 62210, Mexico
| | - Karen Luna-Ramírez
- Illawarra Health and Medical Research Institute, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.
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10
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The Slo(w) path to identifying the mitochondrial channels responsible for ischemic protection. Biochem J 2017; 474:2067-2094. [PMID: 28600454 DOI: 10.1042/bcj20160623] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 02/10/2017] [Accepted: 02/13/2017] [Indexed: 12/19/2022]
Abstract
Mitochondria play an important role in tissue ischemia and reperfusion (IR) injury, with energetic failure and the opening of the mitochondrial permeability transition pore being the major causes of IR-induced cell death. Thus, mitochondria are an appropriate focus for strategies to protect against IR injury. Two widely studied paradigms of IR protection, particularly in the field of cardiac IR, are ischemic preconditioning (IPC) and volatile anesthetic preconditioning (APC). While the molecular mechanisms recruited by these protective paradigms are not fully elucidated, a commonality is the involvement of mitochondrial K+ channel opening. In the case of IPC, research has focused on a mitochondrial ATP-sensitive K+ channel (mitoKATP), but, despite recent progress, the molecular identity of this channel remains a subject of contention. In the case of APC, early research suggested the existence of a mitochondrial large-conductance K+ (BK, big conductance of potassium) channel encoded by the Kcnma1 gene, although more recent work has shown that the channel that underlies APC is in fact encoded by Kcnt2 In this review, we discuss both the pharmacologic and genetic evidence for the existence and identity of mitochondrial K+ channels, and the role of these channels both in IR protection and in regulating normal mitochondrial function.
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11
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Latorre R, Castillo K, Carrasquel-Ursulaez W, Sepulveda RV, Gonzalez-Nilo F, Gonzalez C, Alvarez O. Molecular Determinants of BK Channel Functional Diversity and Functioning. Physiol Rev 2017; 97:39-87. [DOI: 10.1152/physrev.00001.2016] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Large-conductance Ca2+- and voltage-activated K+ (BK) channels play many physiological roles ranging from the maintenance of smooth muscle tone to hearing and neurosecretion. BK channels are tetramers in which the pore-forming α subunit is coded by a single gene ( Slowpoke, KCNMA1). In this review, we first highlight the physiological importance of this ubiquitous channel, emphasizing the role that BK channels play in different channelopathies. We next discuss the modular nature of BK channel-forming protein, in which the different modules (the voltage sensor and the Ca2+ binding sites) communicate with the pore gates allosterically. In this regard, we review in detail the allosteric models proposed to explain channel activation and how the models are related to channel structure. Considering their extremely large conductance and unique selectivity to K+, we also offer an account of how these two apparently paradoxical characteristics can be understood consistently in unison, and what we have learned about the conduction system and the activation gates using ions, blockers, and toxins. Attention is paid here to the molecular nature of the voltage sensor and the Ca2+ binding sites that are located in a gating ring of known crystal structure and constituted by four COOH termini. Despite the fact that BK channels are coded by a single gene, diversity is obtained by means of alternative splicing and modulatory β and γ subunits. We finish this review by describing how the association of the α subunit with β or with γ subunits can change the BK channel phenotype and pharmacology.
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Affiliation(s)
- Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Karen Castillo
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Willy Carrasquel-Ursulaez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Romina V. Sepulveda
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Fernando Gonzalez-Nilo
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Carlos Gonzalez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Osvaldo Alvarez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
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12
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Kaczmarek LK, Aldrich RW, Chandy KG, Grissmer S, Wei AD, Wulff H. International Union of Basic and Clinical Pharmacology. C. Nomenclature and Properties of Calcium-Activated and Sodium-Activated Potassium Channels. Pharmacol Rev 2017; 69:1-11. [PMID: 28267675 PMCID: PMC11060434 DOI: 10.1124/pr.116.012864] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024] Open
Abstract
A subset of potassium channels is regulated primarily by changes in the cytoplasmic concentration of ions, including calcium, sodium, chloride, and protons. The eight members of this subfamily were originally all designated as calcium-activated channels. More recent studies have clarified the gating mechanisms for these channels and have documented that not all members are sensitive to calcium. This article describes the molecular relationships between these channels and provides an introduction to their functional properties. It also introduces a new nomenclature that differentiates between calcium- and sodium-activated potassium channels.
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Affiliation(s)
- Leonard K Kaczmarek
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Richard W Aldrich
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - K George Chandy
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Stephan Grissmer
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Aguan D Wei
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Heike Wulff
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
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13
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Housley DM, Housley GD, Liddell MJ, Jennings EA. Scorpion toxin peptide action at the ion channel subunit level. Neuropharmacology 2016; 127:46-78. [PMID: 27729239 DOI: 10.1016/j.neuropharm.2016.10.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 09/06/2016] [Accepted: 10/06/2016] [Indexed: 12/19/2022]
Abstract
This review categorizes functionally validated actions of defined scorpion toxin (SCTX) neuropeptides across ion channel subclasses, highlighting key trends in this rapidly evolving field. Scorpion envenomation is a common event in many tropical and subtropical countries, with neuropharmacological actions, particularly autonomic nervous system modulation, causing significant mortality. The primary active agents within scorpion venoms are a diverse group of small neuropeptides that elicit specific potent actions across a wide range of ion channel classes. The identification and functional characterisation of these SCTX peptides has tremendous potential for development of novel pharmaceuticals that advance knowledge of ion channels and establish lead compounds for treatment of excitable tissue disorders. This review delineates the unique specificities of 320 individual SCTX peptides that collectively act on 41 ion channel subclasses. Thus the SCTX research field has significant translational implications for pathophysiology spanning neurotransmission, neurohumoral signalling, sensori-motor systems and excitation-contraction coupling. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Affiliation(s)
- David M Housley
- College of Medicine and Dentistry, Cairns Campus, James Cook University, Cairns, Queensland 4878, Australia; Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia.
| | - Gary D Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Michael J Liddell
- Centre for Tropical Environmental and Sustainability Science and College of Science & Engineering, Cairns Campus, James Cook University, Cairns, Queensland 4878, Australia
| | - Ernest A Jennings
- College of Medicine and Dentistry, Cairns Campus, James Cook University, Cairns, Queensland 4878, Australia; Centre for Biodiscovery and Molecular Development of Therapeutics, James Cook University, Queensland 4878, Australia; Australian Institute of Tropical Health and Medicine, James Cook University, Cairns Campus, QLD, Australia
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14
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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.
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15
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Yu M, Liu SL, Sun PB, Pan H, Tian CL, Zhang LH. Peptide toxins and small-molecule blockers of BK channels. Acta Pharmacol Sin 2016; 37:56-66. [PMID: 26725735 DOI: 10.1038/aps.2015.139] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 10/13/2015] [Indexed: 12/21/2022] Open
Abstract
Large conductance, Ca(2+)-activated potassium (BK) channels play important roles in the regulation of neuronal excitability and the control of smooth muscle contractions. BK channels can be activated by changes in both the membrane potential and intracellular Ca(2+) concentrations. Here, we provide an overview of the structural and pharmacological properties of BK channel blockers. First, the properties of different venom peptide toxins from scorpions and snakes are described, with a focus on their characteristic structural motifs, including their disulfide bond formation pattern, the binding interface between the toxin and BK channel, and the functional consequence of the blockage of BK channels by these toxins. Then, some representative non-peptide blockers of BK channels are also described, including their molecular formula and pharmacological effects on BK channels. The detailed categorization and descriptions of these BK channel blockers will provide mechanistic insights into the blockade of BK channels. The structures of peptide toxins and non-peptide compounds could provide templates for the design of new channel blockers, and facilitate the optimization of lead compounds for further therapeutic applications in neurological disorders or cardiovascular diseases.
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16
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Nikouee A, Khabiri M, Cwiklik L. Scorpion toxins prefer salt solutions. J Mol Model 2015; 21:287. [PMID: 26475740 DOI: 10.1007/s00894-015-2822-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 09/15/2015] [Indexed: 11/26/2022]
Abstract
There is a wide variety of ion channel types with various types of blockers, making research in this field very complicated. To reduce this complexity, it is essential to study ion channels and their blockers independently. Scorpion toxins, a major class of blockers, are charged short peptides with high affinities for potassium channels. Their high selectivity and inhibitory properties make them an important pharmacological tool for treating autoimmune or nervous system disorders. Scorpion toxins typically have highly charged surfaces and-like other proteins-an intrinsic ability to bind ions (Friedman J Phys Chem B 115(29):9213-9223, 1996; Baldwin Biophys J 71(4):2056-2063, 1996; Vrbka et al. Proc Natl Acad Sci USA 103(42):15440-15444, 2006a; Vrbka et al. J Phys Chem B 110(13):7036-43, 2006b). Thus, their effects on potassium channels are usually investigated in various ionic solutions. In this work, computer simulations of protein structures were performed to analyze the structural properties of the key residues (i.e., those that are presumably involved in contact with the surfaces of the ion channels) of 12 scorpion toxins. The presence of the two most physiologically abundant cations, Na(+) and K(+), was considered. The results indicated that the ion-binding properties of the toxin residues vary. Overall, all of the investigated toxins had more stable structures in ionic solutions than in water. We found that both the number and length of elements in the secondary structure varied depending on the ionic solution used (i.e., in the presence of NaCl or KCl). This study revealed that the ionic solution should be chosen carefully before performing experiments on these toxins. Similarly, the influence of these ions should be taken into consideration in the design of toxin-based pharmaceuticals.
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Affiliation(s)
- Azadeh Nikouee
- Institute of Applied Physiology, Ulm University, Ulm, Germany
| | - Morteza Khabiri
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610, Prague 6, Czech Republic.
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, 48109, USA.
| | - Lukasz Cwiklik
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610, Prague 6, Czech Republic
- J. Heyrovský Institute of Physical Chemistry Academy of Sciences of the Czech Republic v.v.i., Dolejskova 3, 18223, Prague 8, Czech Republic
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17
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Sánchez-Carranza O, Torres-Rodríguez P, Darszon A, Treviño CL, López-González I. Pharmacology of hSlo3 channels and their contribution in the capacitation-associated hyperpolarization of human sperm. Biochem Biophys Res Commun 2015; 466:554-9. [PMID: 26381170 DOI: 10.1016/j.bbrc.2015.09.073] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 09/12/2015] [Indexed: 01/01/2023]
Abstract
Slo3 channels (mSlo3) primarily mediate mouse sperm K(+) currents and are essential for the capacitation-associated hyperpolarization (CAH). Whether Slo3 and/or Slo1, two Slo family K(+) channels are functionally expressed in human sperm is controversial. Our recent pharmacological studies of the human sperm CAH suggested the participation of both. Lack of a detailed pharmacology of heterologously expressed human Slo3 (hSlo3) prevented precisely identifying the K(+) channel(s) involved. In the present report, we compare the pharmacological profile of expressed hSlo3 in CHO cells with that of the CAH to advance this matter. Whole-cell patch-clamp recordings showed that hSlo3 currents are inhibited: significantly by progesterone, Ba(2+) and quinidine; partially by Penitrem A and Charybdotoxin; and poorly by Iberiotoxin and Slotoxin. Surprisingly, hSlo3 currents were resistant to Clofilium and 60 mM TEA(+) which inhibit mSlo3. Pharmacological comparison of the CAH and hSlo3 profiles indicates in addition to hSlo3, other K(+) channels, possibly Slo1, may participate in CAH. The pharmacological profile of heterologously expressed hSlo3 channels differs from that of mSlo3 K(+) channels, consistent with species-specific differences observed among other sperm ion channels. While the pharmacological correlation analysis of the hSlo3 currents and the CAH confirmed the participation of hSlo3 channels, it suggests that additional K(+) channels may be involved, in particular Slo1 channels.
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Affiliation(s)
- Oscar Sánchez-Carranza
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Paulina Torres-Rodríguez
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Alberto Darszon
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico
| | - Claudia L Treviño
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico.
| | - Ignacio López-González
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, Mexico.
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Maher J, Hunter AC, Mabley JG, Lippiat J, Allen MC. Smooth muscle relaxation and activation of the large conductance Ca(++)-activated K+ (BK(Ca)) channel by novel oestrogens. Br J Pharmacol 2015; 169:1153-65. [PMID: 23586466 DOI: 10.1111/bph.12211] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 02/25/2013] [Accepted: 03/24/2013] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE Oestrogens can interact directly with membrane receptors and channels and can activate vascular BK(Ca) channels. We hypothesized that novel oestrogen derivatives could relax smooth muscle by an extracllular effect on the α and β1 subunits of the BK(Ca) channel, rather than at an intracellular site. EXPERIMENTAL APPROACH We studied the effects of novel oestrogens on the tension of pre-contracted isolated rat aortic rings, and on the electrophysiological properties of HEK 293 cells expressing the hSloα or hSloα+β1 subunits. Two of the derivatives incorporated a quaternary ammonium side-chain making them membrane impermeable. KEY RESULTS Oestrone, oestrone oxime and Quat DME-oestradiol relaxed pre-contracted rat aorta, but only Quat DME-oestradiol-induced relaxation was iberiotoxin sensitive. However, only potassium currents recorded in HEK 293 cells over-expressing both hSloα and hSloβ1 were activated by oestrone, oestrone oxime and Quat DME-oestradiol. CONCLUSION AND IMPLICATIONS The novel oestrogens were able to relax smooth muscle, but through different mechanisms. In particular, oestrone oxime required the presence of the endothelium to exert much of its effect, whilst Quat DME-oestradiol depended both on NO and BK(Ca) channel activation. The activation of BK(Ca) currents in HEK 293 cells expressing hSloα+β1 by Quat DME-oestradiol is consistent with an extracellular binding site between the two subunits. The binding site resides between the extracellular N terminal of the α subunit and the extracellular loop between TM1 and 2 of the β1 subunit. Membrane-impermeant Quat DME-oestradiol lacks an exchangeable hydrogen on the A ring obviating antioxidant activity.
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Affiliation(s)
- J Maher
- School of Pharmacy and Biomolecular Science, University of Brighton, Brighton, UK
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19
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Tanner MR, Hu X, Huq R, Tajhya RB, Sun L, Khan FS, Laragione T, Horrigan FT, Gulko PS, Beeton C. KCa1.1 inhibition attenuates fibroblast-like synoviocyte invasiveness and ameliorates disease in rat models of rheumatoid arthritis. Arthritis Rheumatol 2015; 67:96-106. [PMID: 25252152 DOI: 10.1002/art.38883] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2014] [Accepted: 09/11/2014] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Fibroblast-like synoviocytes (FLS) participate in joint inflammation and damage in rheumatoid arthritis (RA) and its animal models. The purpose of this study was to define the importance of KCa1.1 (BK, Maxi-K, Slo1, KCNMA1) channel expression and function in FLS and to establish these channels as potential new targets for RA therapy. METHODS We compared KCa1.1 expression levels in FLS from rats with pristane-induced arthritis (PIA) and in FLS from healthy rats. We then used ex vivo functional assays combined with small interfering RNA-induced knockdown, overexpression, and functional modulation of KCa1.1 in PIA FLS. Finally, we determined the effectiveness of modulating KCa1.1 in 2 rat models of RA, moderate PIA and severe collagen-induced arthritis (CIA). RESULTS We found that PIA FLS expressed the KCa1.1 channel as their major potassium channel, as has been found in FLS from patients with RA. In contrast, FLS from healthy rats expressed fewer of these channels. Inhibiting the function or expression of KCa1.1 ex vivo reduced proliferation and invasive properties of, as well as protease production by, PIA FLS, whereas opening native KCa1.1 or overexpressing the channel enhanced the invasiveness of both FLS from rats with PIA and FLS from healthy rats. Treatment with a KCa1.1 channel blocker at the onset of clinical signs stopped disease progression in the PIA and CIA models, reduced joint and bone damage, and inhibited FLS invasiveness and proliferation. CONCLUSION Our results demonstrate a critical role of KCa1.1 channels in the regulation of FLS invasiveness and suggest that KCa1.1 channels represent potential therapeutic targets in RA.
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20
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Torres YP, Granados ST, Latorre R. Pharmacological consequences of the coexpression of BK channel α and auxiliary β subunits. Front Physiol 2014; 5:383. [PMID: 25346693 PMCID: PMC4193333 DOI: 10.3389/fphys.2014.00383] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 09/16/2014] [Indexed: 01/03/2023] Open
Abstract
Coded by a single gene (Slo1, KCM) and activated by depolarizing potentials and by a rise in intracellular Ca(2+) concentration, the large conductance voltage- and Ca(2+)-activated K(+) channel (BK) is unique among the superfamily of K(+) channels. BK channels are tetramers characterized by a pore-forming α subunit containing seven transmembrane segments (instead of the six found in voltage-dependent K(+) channels) and a large C terminus composed of two regulators of K(+) conductance domains (RCK domains), where the Ca(2+)-binding sites reside. BK channels can be associated with accessory β subunits and, although different BK modulatory mechanisms have been described, greater interest has recently been placed on the role that the β subunits may play in the modulation of BK channel gating due to its physiological importance. Four β subunits have currently been identified (i.e., β1, β2, β3, and β4) and despite the fact that they all share the same topology, it has been shown that every β subunit has a specific tissue distribution and that they modify channel kinetics as well as their pharmacological properties and the apparent Ca(2+) sensitivity of the α subunit in different ways. Additionally, different studies have shown that natural, endogenous, and synthetic compounds can modulate BK channels through β subunits. Considering the importance of these channels in different pathological conditions, such as hypertension and neurological disorders, this review focuses on the mechanisms by which these compounds modulate the biophysical properties of BK channels through the regulation of β subunits, as well as their potential therapeutic uses for diseases such as those mentioned above.
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Affiliation(s)
- Yolima P Torres
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana Bogotá, Colombia
| | - Sara T Granados
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana Bogotá, Colombia ; Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
| | - Ramón Latorre
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso Valparaíso, Chile
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21
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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.
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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.
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López-González I, Torres-Rodríguez P, Sánchez-Carranza O, Solís-López A, Santi CM, Darszon A, Treviño CL. Membrane hyperpolarization during human sperm capacitation. Mol Hum Reprod 2014; 20:619-29. [PMID: 24737063 DOI: 10.1093/molehr/gau029] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Sperm capacitation is a complex and indispensable physiological process that spermatozoa must undergo in order to acquire fertilization capability. Spermatozoa from several mammalian species, including mice, exhibit a capacitation-associated plasma membrane hyperpolarization, which is necessary for the acrosome reaction to occur. Despite its importance, this hyperpolarization event has not been adequately examined in human sperm. In this report we used flow cytometry to show that a subpopulation of human sperm indeed undergo a plasma membrane hyperpolarization upon in vitro capacitation. This hyperpolarization correlated with two other well-characterized capacitation parameters, namely an increase in intracellular pH and Ca(2+) concentration, measured also by flow cytometry. We found that sperm membrane hyperpolarization was completely abolished in the presence of a high external K(+) concentration (60 mM), indicating the participation of K(+) channels. In order to identify, which of the potential K(+) channels were involved in this hyperpolarization, we used different K(+) channel inhibitors including charybdotoxin, slotoxin and iberiotoxin (which target Slo1) and clofilium (a more specific blocker for Slo3). All these K(+) channel antagonists inhibited membrane hyperpolarization to a similar extent, suggesting that both members of the Slo family may potentially participate. Two very recent papers recorded K(+) currents in human sperm electrophysiologically, with some contradictory results. In the present work, we show through immunoblotting that Slo3 channels are present in the human sperm membrane. In addition, we found that human Slo3 channels expressed in CHO cells were sensitive to clofilium (50 μM). Considered altogether, our data indicate that Slo1 and Slo3 could share the preponderant role in the capacitation-associated hyperpolarization of human sperm in contrast to what has been previously reported for mouse sperm, where Slo3 channels are the main contributors to the hyperpolarization event.
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Affiliation(s)
- I López-González
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - P Torres-Rodríguez
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - O Sánchez-Carranza
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - A Solís-López
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - C M Santi
- Department of Anatomy and Neurobiology, Washington University School of Medicine, 660 S Euclid Ave, St. Louis, MO 63110, USA
| | - A Darszon
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - C L Treviño
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
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23
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Li M, Chang S, Yang L, Shi J, McFarland K, Yang X, Moller A, Wang C, Zou X, Chi C, Cui J. Conopeptide Vt3.1 preferentially inhibits BK potassium channels containing β4 subunits via electrostatic interactions. J Biol Chem 2014; 289:4735-42. [PMID: 24398688 DOI: 10.1074/jbc.m113.535898] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
BK channel β subunits (β1-β4) modulate the function of channels formed by slo1 subunits to produce tissue-specific phenotypes. The molecular mechanism of how the homologous β subunits differentially alter BK channel functions and the role of different BK channel functions in various physiologic processes remain unclear. By studying channels expressed in Xenopus laevis oocytes, we show a novel disulfide-cross-linked dimer conopeptide, Vt3.1 that preferentially inhibits BK channels containing the β4 subunit, which is most abundantly expressed in brain and important for neuronal functions. Vt3.1 inhibits the currents by a maximum of 71%, shifts the G-V relation by 45 mV approximately half-saturation concentrations, and alters both open and closed time of single channel activities, indicating that the toxin alters voltage dependence of the channel. Vt3.1 contains basic residues and inhibits voltage-dependent activation by electrostatic interactions with acidic residues in the extracellular loops of the slo1 and β4 subunits. These results suggest a large interaction surface between the slo1 subunit of BK channels and the β4 subunit, providing structural insight into the molecular interactions between slo1 and β4 subunits. The results also suggest that Vt3.1 is an excellent tool for studying β subunit modulation of BK channels and for understanding the physiological roles of BK channels in neurophysiology.
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Affiliation(s)
- Min Li
- From the Institute of Protein Research, Tongji University, Shanghai 200092, China
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Rendón-Anaya M, Delaye L, Possani LD, Herrera-Estrella A. Global transcriptome analysis of the scorpion Centruroides noxius: new toxin families and evolutionary insights from an ancestral scorpion species. PLoS One 2012; 7:e43331. [PMID: 22912855 PMCID: PMC3422302 DOI: 10.1371/journal.pone.0043331] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 07/19/2012] [Indexed: 02/05/2023] Open
Abstract
Scorpion venoms have been studied for decades, leading to the identification of hundreds of different toxins with medical and pharmacological implications. However, little emphasis has been given to the description of these arthropods from cellular and evolutionary perspectives. In this report, we describe a transcriptomic analysis of the Mexican scorpion Centruroides noxius Hoffmann, performed with a pyrosequencing platform. Three independent sequencing experiments were carried out, each including three different cDNA libraries constructed from RNA extracted from the whole body of the scorpion after telson removal, and from the venom gland before and after venom extraction. Over three million reads were obtained and assembled in almost 19000 isogroups. Within the telson-specific sequences, 72 isogroups (0.4% of total unique transcripts) were found to be similar to toxins previously reported in other scorpion species, spiders and sea anemones. The annotation pipeline also revealed the presence of important elements of the small non-coding RNA processing machinery, as well as microRNA candidates. A phylogenomic analysis of concatenated essential genes evidenced differential evolution rates in this species, particularly in ribosomal proteins and proteasome components. Additionally, statistical comparison of transcript abundance before and after venom extraction showed that 3% and 2% of the assembled isogroups had higher expression levels in the active and replenishing gland, respectively. Thus, our sequencing and annotation strategies provide a general view of the cellular and molecular processes that take place in these arthropods, allowed the discovery of new pharmacological and biotechnological targets and uncovered several regulatory and metabolic responses behind the assembly of the scorpion venom. The results obtained in this report represent the first high-throughput study that thoroughly describes the universe of genes that are expressed in the scorpion Centruroides noxius Hoffmann, a highly relevant organism from medical and evolutionary perspectives.
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Affiliation(s)
- Martha Rendón-Anaya
- Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados (CINVESTAV), Irapuato, Guanajuato, México
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México
| | - Luis Delaye
- Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados (CINVESTAV), Irapuato, Guanajuato, México
| | - Lourival D. Possani
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México
- * E-mail: (AH-E); (LDP)
| | - Alfredo Herrera-Estrella
- Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados (CINVESTAV), Irapuato, Guanajuato, México
- * E-mail: (AH-E); (LDP)
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Towards therapeutic applications of arthropod venom k(+)-channel blockers in CNS neurologic diseases involving memory acquisition and storage. J Toxicol 2012; 2012:756358. [PMID: 22701481 PMCID: PMC3373146 DOI: 10.1155/2012/756358] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Accepted: 02/08/2012] [Indexed: 12/31/2022] Open
Abstract
Potassium channels are the most heterogeneous and widely distributed group of ion channels and play important functions in all cells, in both normal and pathological mechanisms, including learning and memory processes. Being fundamental for many diverse physiological processes, K+-channels are recognized as potential therapeutic targets in the treatment of several Central Nervous System (CNS) diseases, such as multiple sclerosis, Parkinson's and Alzheimer's diseases, schizophrenia, HIV-1-associated dementia, and epilepsy. Blockers of these channels are therefore potential candidates for the symptomatic treatment of these neuropathies, through their neurological effects. Venomous animals have evolved a wide set of toxins for prey capture and defense. These compounds, mainly peptides, act on various pharmacological targets, making them an innumerable source of ligands for answering experimental paradigms, as well as for therapeutic application. This paper provides an overview of CNS K+-channels involved in memory acquisition and storage and aims at evaluating the use of highly selective K+-channel blockers derived from arthropod venoms as potential therapeutic agents for CNS diseases involving learning and memory mechanisms.
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Abstract
INTRODUCTION Epilepsies are disorders of neuronal excitability characterized by spontaneous and recurrent seizures. Ion channels are critical for regulating neuronal excitability and, therefore, can contribute significantly to epilepsy pathophysiology. In particular, large conductance, Ca2+-activated K+ (BKCa) channels play an important role in seizure etiology. These channels are activated by both membrane depolarization and increased intracellular Ca2+. This unique coupling of Ca2+ signaling to membrane depolarization is important in controlling neuronal hyperexcitability, as outward K+ current through BKCa channels hyperpolarizes neurons. AREAS COVERED BKCa channel structure-function and the role of these channels in epilepsy pathophysiology. EXPERT OPINION Loss-of-function BKCa channel mutations contribute to neuronal hyperexcitability that can lead to temporal lobe epilepsy, tonic-clonic seizures and alcohol withdrawal seizures. Similarly, BKCa channel blockade can trigger seizures and status epilepticus. Paradoxically, some mutations in BKCa channel subunit can give rise to channel gain-of-function that leads to development of idiopathic epilepsy (primarily absence epilepsy). Seizures themselves also enhance BKCa channel currents associated with neuronal hyperexcitability, and blocking BKCa channels suppresses generalized tonic-clonic seizures. Thus, both loss-of-function and gain-of-function BKCa channels might serve as molecular targets for drugs to suppress certain seizure phenotypes including temporal lobe seizures and absence seizures, respectively.
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Affiliation(s)
- Prosper N'Gouemo
- Georgetown University Medical Center, Interdisciplinary Program in Neuroscience and Department of Pediatrics, Washington, DC 20057, USA.
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Gao B, Peigneur S, Dalziel J, Tytgat J, Zhu S. Molecular divergence of two orthologous scorpion toxins affecting potassium channels. Comp Biochem Physiol A Mol Integr Physiol 2011; 159:313-21. [PMID: 21466856 DOI: 10.1016/j.cbpa.2011.03.027] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 03/25/2011] [Accepted: 03/28/2011] [Indexed: 11/26/2022]
Abstract
Alpha-KTxs are a diverse group of scorpion short-chain peptide toxins that affect animal potassium channels. We report the biochemical purification, gene cloning, and functional characterization of a new α-KTx named MeuTx3B, from venom of the scorpion Mesobuthus eupeus. MeuTx3B is an orthologue of BmTx3B/Martentoxin (α-KTx16 subfamily) from Mesobuthus martensii that differs by three amino acid substitutions. We found that despite their orthologous relationship, MeuTx3B and BmTx3B exhibit different post-transcriptional processing patterns due to nucleotide mutations in their untranslated regions (UTRs). Our results show that MeuTx3B also differs functionally from BmTx3B in that it lacks inhibitory activity on large conductance calcium-activated potassium channels (BK), implicating the amino acids of difference in conferring the inhibitory activity of BmTx3B. Furthermore, we show that MeuTx3B (2μM) partially inhibits human voltage-gated potassium channel Kv1.3. By using codon-substitution models, we detected signals of positive selection that could drive adaptive evolution of MeuTx3B and related toxins in the functional region associated with pharmacological diversification of toxins in the α-KTx 1 and 16 subfamilies.
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Affiliation(s)
- Bin Gao
- Group of Animal Innate Immunity, State Key Laboratory of Integrated Management of Pest Insects & Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
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Jacobson DA, Mendez F, Thompson M, Torres J, Cochet O, Philipson LH. Calcium-activated and voltage-gated potassium channels of the pancreatic islet impart distinct and complementary roles during secretagogue induced electrical responses. J Physiol 2010; 588:3525-37. [PMID: 20643768 DOI: 10.1113/jphysiol.2010.190207] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Glucose-induced β-cell action potential (AP) repolarization is regulated by potassium efflux through voltage gated (Kv) and calcium activated (K(Ca)) potassium channels. Thus, ablation of the primary Kv channel of the β-cell, Kv2.1, causes increased AP duration. However, Kv2.1(-/-) islet electrical activity still remains sensitive to the potassium channel inhibitor tetraethylammonium. Therefore, we utilized Kv2.1(-/-) islets to characterize Kv and K(Ca) channels and their respective roles in modulating the β-cell AP. The remaining Kv current present in Kv2.1(-/-) β-cells is inhibited with 5 μM CP 339818. Inhibition of the remaining Kv current in Kv2.1(-/-) mouse β-cells increased AP firing frequency by 39.6% but did not significantly enhance glucose stimulated insulin secretion (GSIS). The modest regulation of islet AP frequency by CP 339818 implicates other K(+) channels, possibly K(Ca) channels, in regulating AP repolarization. Blockade of the K(Ca) channel BK with slotoxin increased β-cell AP amplitude by 28.2%, whereas activation of BK channels with isopimaric acid decreased β-cell AP amplitude by 30.6%. Interestingly, the K(Ca) channel SK significantly contributes to Kv2.1(-/-) mouse islet AP repolarization. Inhibition of SK channels decreased AP firing frequency by 66% and increased AP duration by 67% only when Kv2.1 is ablated or inhibited and enhanced GSIS by 2.7-fold. Human islets also express SK3 channels and their β-cell AP frequency is significantly accelerated by 4.8-fold with apamin. These results uncover important repolarizing roles for both Kv and K(Ca) channels and identify distinct roles for SK channel activity in regulating calcium- versus sodium-dependent AP firing.
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Affiliation(s)
- David A Jacobson
- Deparment of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232-0615, USA.
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Storer RJ, Immke DC, Goadsby PJ. Large conductance calcium-activated potassium channels (BKCa) modulate trigeminovascular nociceptive transmission. Cephalalgia 2010; 29:1242-58. [PMID: 19911462 DOI: 10.1111/j.1468-2982.2009.01849.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Migraine is a common, disabling, neurological problem whose acute management would benefit from the development of purely neurally acting therapies. The trigeminocervical complex is pivotal in nociceptive signaling in migraine, and is an accepted target for putative antimigraine agents. Whole-cell patch-clamp or extracellular recordings were made of trigeminal neurons identified in rat brainstem slices. Bath application of the large conductance calcium-activated potassium (BKCa) channel opener NS1619 caused a dramatic decrease of cell firing that could be reversed by the co-application of iberiotoxin. NS1619 hyperpolarized the resting membrane potential and reduced the frequency of spontaneous action potentials in these neurons. These data suggest the presence of BKCa channels in the trigeminocervical complex. In vivo in cat L-glutamate-evoked firing was facilitated in nociceptive neurons, also responding to stimulation of the superior sagittal sinus, in the trigeminal nucleus caudalis by the BKCa peptide antagonists, iberiotoxin and slotoxin. Of units tested, 70% responded to microiontophoretic application of the blockers, identifying a subpopulation of trigeminal neurons expressing toxin-sensitive BKCa channels. NS1619 inhibited 74% of cells tested, and this was reversed by slotoxin, suggesting that the action of NS1619 in these cells was mediated through BKCa channels. These data are consistent with the presence of BKCa channels in the trigeminal nucleus caudalis that are potential targets for the development of antimigraine treatments, and may also offer insights into receptor mechanisms involved in sensitization and thus allodynia, in migraine.
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Affiliation(s)
- R J Storer
- Department of Neurology, University of California, San Francisco, California 94143-0114, USA
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King GF, Gentz MC, Escoubas P, Nicholson GM. A rational nomenclature for naming peptide toxins from spiders and other venomous animals. Toxicon 2008; 52:264-76. [DOI: 10.1016/j.toxicon.2008.05.020] [Citation(s) in RCA: 230] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 05/23/2008] [Accepted: 05/23/2008] [Indexed: 11/25/2022]
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Zeng H, Gordon E, Lin Z, Lozinskaya IM, Willette RN, Xu X. 1-[1-Hexyl-6-(methyloxy)-1H-indazol-3-yl]-2-methyl-1-propanone, a Potent and Highly Selective Small Molecule Blocker of the Large-Conductance Voltage-Gated and Calcium-Dependent K+Channel. J Pharmacol Exp Ther 2008; 327:168-77. [DOI: 10.1124/jpet.108.139733] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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Wulff H, Zhorov BS. K+ channel modulators for the treatment of neurological disorders and autoimmune diseases. Chem Rev 2008; 108:1744-73. [PMID: 18476673 PMCID: PMC2714671 DOI: 10.1021/cr078234p] [Citation(s) in RCA: 168] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Heike Wulff
- Department of Pharmacology, University of California, Davis, California 95616, USA.
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Inhibition of martentoxin on neuronal BK channel subtype (alpha+beta4): implications for a novel interaction model. Biophys J 2008; 94:3706-13. [PMID: 18199674 DOI: 10.1529/biophysj.107.122150] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Martentoxin as a 37-residue peptide was capable of blocking large-conductance Ca(2+)-activated K(+) (BK) channels in adrenal medulla chromaffin cells. This study investigated the pharmacological discrimination of martentoxin on BK channel subtypes. The results showed that the iberiotoxin-insensitive neuronal BK channels (alpha+beta4) could be potently blocked by martentoxin (IC(50) = approximately 80 nM). In contrast, the iberiotoxin-sensitive BK channel consisting of only alpha-subunit was less sensitive to martentoxin. Distinctively, martentoxin inhibited neuronal BK channels (alpha+beta4) with a novel interaction mode. Two possible interaction sites of neuronal BK channels (alpha+beta4) might be responsible for the binding with martentoxin: one for trapping and the other located at the pore region for blocking. In addition, the inhibition of martentoxin on neuronal BK channels (alpha+beta4) depended on cytoplasmic Ca(2+) concentration. On the other hand, in vivo experiments from EEG recordings suggested that neuronal BK channels (alpha+beta4) were the primary target of martentoxin. Therefore, this research not only sheds light on a unique ligand for neuronal BK channels (alpha+beta4), but also highlights a novel model approach for the interaction between K(+) channels and specific-ligands.
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Yao J, Li H, Gan GL, Wu Y, Ding JP. Residue Phe266 in S5-S6 loop is not critical for Charybdotoxin binding to Ca2+-activated K+ (mSlo1) channels. Acta Pharmacol Sin 2006; 27:945-9. [PMID: 16787581 DOI: 10.1111/j.1745-7254.2006.00385.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
AIM To gain insight into the interaction between the Charybdotoxin (ChTX) and BK channels. METHODS Site-directed mutagenesis was used to make two mutants: mSlo1-F266L and mSlo1-F266A. The two mutants were then expressed in Xenopus oocytes and their effects were tested on ChTX by electrophysiology experiments. RESULTS We demonstrate an equilibrium dissociation constant Kd=3.1-4.2 nmol/L for both the mutants mSlo1-F266L and mSlo1-F266A similar to that of the wild-type mSlo1 Kd=3.9 nmol/L. CONCLUSION The residue Phe266 does not play a crucial role in binding to ChTX, which is opposed to the result arising from the simulation of peptide-channel interaction.
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Affiliation(s)
- Jing Yao
- Institute of Biochemistry and Biophysics, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
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Ghatta S, Nimmagadda D, Xu X, O'Rourke ST. Large-conductance, calcium-activated potassium channels: structural and functional implications. Pharmacol Ther 2005; 110:103-16. [PMID: 16356551 DOI: 10.1016/j.pharmthera.2005.10.007] [Citation(s) in RCA: 240] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Accepted: 10/13/2005] [Indexed: 12/16/2022]
Abstract
The large-conductance, calcium-activated potassium channels (BK, also termed BK(Ca), Slo, or MaxiK) distributed in both excitable and non-excitable cells are involved in many cellular functions such as action potential repolarization; neuronal excitability; neurotransmitter release; hormone secretion; tuning of cochlear hair cells; innate immunity; and modulation of the tone of vascular, airway, uterine, gastrointestinal, and urinary bladder smooth muscle tissues. Because of their high conductance, activation of BK channels has a strong effect on membrane potential. BK channels differ from all other potassium (K(+)) channels due to their high sensitivity to both intracellular calcium (Ca(2+)) concentrations and voltage. These features make BK channels ideal negative feedback regulators in many cell types by decreasing voltage-dependent Ca(2+) entry through membrane potential hyperpolarization. The current review aims to give a comprehensive understanding of the structure and molecular biology of BK channels and their relevance to various pathophysiological conditions. The review will also focus on the therapeutic potential and pharmacology of the various BK channel activators and blockers.
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Affiliation(s)
- Srinivas Ghatta
- Department of Pharmaceutical Sciences, College of Pharmacy, North Dakota State University, Fargo, 58105, USA.
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36
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Kristensen M, Hansen T, Juel C. Membrane proteins involved in potassium shifts during muscle activity and fatigue. Am J Physiol Regul Integr Comp Physiol 2005; 290:R766-72. [PMID: 16223848 DOI: 10.1152/ajpregu.00534.2004] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Muscle activity is associated with potassium displacements, which may cause fatigue. It was reported previously that the density of the large-conductance Ca2+-dependent K+ (BK(Ca)) channel is higher in the T tubule membrane than in the sarcolemmal membrane and that the opposite is the case for the ATP-sensitive K+ (K(ATP)) channel. In the present experiments, we investigated the subcellular localizations of the strong inward rectifier 2.1 K+ (Kir2.1) channel and the Na+-K+-2Cl- (NKCC)1 cotransporter with Western blot analysis of different muscle fractions. Furthermore, muscle function was studied while trying to manipulate the opening probability or transport capacity of these proteins during electrical stimulation of isolated soleus muscles. All experiments were made with excised muscle from male Wistar rats. Kir2.1 channels were almost undetectable in the sarcolemmal membrane but present in the T tubule membrane, whereas NKCC1 cotransporters were present in the sarcolemmal membrane. For muscles incubated in a buffer containing pinacidil, NS1619, Ba2+, or bumetanide, there was a faster reduction in peak force (P < 0.05). Furthermore, bumetanide incubation reduced the peak force at the onset of electrical stimulation (P < 0.05). Thus the effects on muscle force indicate that these drugs can affect K+-transporting proteins and thereby influence K+ accumulation, especially in the T tubules, suggesting that K(ATP) and BK(Ca) channels are responsible for K+ release and decrease in force during repeated muscle contractions, whereas Kir2.1 and NKCC1 may have a role in K+ reuptake.
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Affiliation(s)
- Michael Kristensen
- Copenhagen Muscle Research Centre, Institute of Molecular Biology and Physiology, August Krogh Bldg., DK-2100 Copenhagen Ø, Denmark
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Tamoxifen alters gating of the BK α subunit and mediates enhanced interactions with the avian β subunit. Biochem Pharmacol 2005; 70:47-58. [DOI: 10.1016/j.bcp.2005.03.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2005] [Revised: 03/25/2005] [Accepted: 03/30/2005] [Indexed: 11/22/2022]
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Yao J, Chen X, Li H, Zhou Y, Yao L, Wu G, Chen X, Zhang N, Zhou Z, Xu T, Wu H, Ding J. BmP09, a “Long Chain” Scorpion Peptide Blocker of BK Channels. J Biol Chem 2005; 280:14819-28. [PMID: 15695820 DOI: 10.1074/jbc.m412735200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A novel "long chain" toxin BmP09 has been purified and characterized from the venom of the Chinese scorpion Buthus martensi Karsch. The toxin BmP09 is composed of 66 amino acid residues, including eight cysteines, with a mass of 7721.0 Da. Compared with the B. martensi Karsch AS-1 as a Na(+) channel blocker (7704.8 Da), the BmP09 has an exclusive difference in sequence by an oxidative modification at the C terminus. The sulfoxide Met-66 at the C terminus brought the peptide a dramatic switch from a Na(+) channel blocker toaK(+) channel blocker. Upon probing the targets of the toxin BmP09 on the isolated mouse adrenal medulla chromaffin cells, where a variety of ion channels coexists, we found that the toxin BmP09 specifically blocked large conductance Ca(2+)- and voltage-dependent K(+) channels (BK) but not Na(+) channels at a range of 100 nm concentration. This was further confirmed by blocking directly the BK channels encoded with mSlo1 alpha-subunits in Xenopus oocytes. The half-maximum concentration EC(50) of BmP09 was 27 nm, and the Hill coefficient was 1.8. In outside-out patches, the 100 nm BmP09 reduced approximately 70% currents of BK channels without affecting the single-channel conductance. In comparison with the "short chain" scorpion peptide toxins such as Charybdotoxin, the toxin BmP09 behaves much better in specificity and reversibility, and thus it will be a more efficient tool for studying BK channels. A three-dimensional simulation between a BmP09 toxin and an mSlo channel shows that the Lys-41 in BmP09 lies at the center of the interface and plugs into the entrance of the channel pore. The stable binding between the toxin BmP09 and the BK channel is favored by aromatic pi -pi interactions around the center.
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Affiliation(s)
- Jing Yao
- Institute of Biochemistry and Biophysics, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
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Valdez-Cruz NA, Dávila S, Licea A, Corona M, Zamudio FZ, García-Valdes J, Boyer L, Possani LD. Biochemical, genetic and physiological characterization of venom components from two species of scorpions: Centruroides exilicauda Wood and Centruroides sculpturatus Ewing. Biochimie 2005; 86:387-96. [PMID: 15358055 DOI: 10.1016/j.biochi.2004.05.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Accepted: 05/14/2004] [Indexed: 11/17/2022]
Abstract
Current literature concerning the taxonomic names of two possibly distinct species of scorpions from the genus Centruroides (sculpturatus and/or exilicauda) is controversial. This communication reports the results of biochemical, genetic and electrophysiological experiments conducted with C. exilicauda Wood of Baja California (Mexico) and C. sculpturatus Ewing of Arizona (USA). The chromatographic profile fractionation of the soluble venom from both species of scorpions is different. The N-terminal amino acid sequence for nine toxins of C. exilicauda was determined and compared with those from C. sculpturatus. Lethality tests conducted in mice support the idea that C. exilicauda venom should be expected to be medically less important than C. sculpturatus. Thirteen genes from the venomous glands of the scorpion C. exilicauda were obtained and compared with previously published sequences from genes of the species C. sculpturatus. Genes coding for cytochrome oxidase I and II of both species were also sequenced. A phylogenetic tree was generated with this information showing important differences between them. Additionally, the results of electrophysiological assays conducted with the venom from both species on the Ca(2+)-dependent K(+)-channels, showed significant differences. These results strongly support the conclusion that C. exilicauda and C. sculpturatus are in fact two distinct species of scorpions.
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Affiliation(s)
- Norma A Valdez-Cruz
- Department of Molecular Medicine and Bioprocesses, Institute of Biotechnology, National Autonomous University of Mexico, Avenida Universidad 2001, Apartado Postal 510-3, Cuernavaca 62210, Mexico
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Abstract
Much of our knowledge on K+-channels was elucidated using specific peptide ligands isolated from a number of venomous organisms. Recently, this field received a strong support and increased interest due to the solution of the three-dimensional structure of a couple of K+-channels. At the same time, several new subfamilies of specific toxins for K+-channels were isolated from scorpion venoms, enhancing the availability and diversity of such useful molecular tools. It opened new lines of research for the better understanding of K+-channel biophysics and pharmacology. In this review, we listed 120 amino acid sequences of peptides isolated from scorpion venoms. They were demonstrated or assumed to be specific for K+-channels. These sequences were aligned and used to generate a rooted phylogenetic tree. The evolutionary tree indicates that several clusters of divergent peptides show preference for specific subtypes of channels. The three-dimensional structures of representative examples of these peptides were drawn and analysed concerning the molecular fitness of their interactions with the channel targets. Four different interacting modes were identified to exist between scorpion toxins and the various subtypes of K+-channels.
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Affiliation(s)
- Ricardo C Rodríguez de la Vega
- Department of Molecular Medicine and Bioprocesses, Institute of Biotechnology, National Autonomous University of Mexico, Avenida Universidad, 2001, Apartado Postal 510-3, Cuernavaca 62210, Mexico
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