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Siatis KE, Giannopoulou E, Manou D, Sarantis P, Karamouzis MV, Raftopoulou S, Fasseas K, Alzahrani FM, Kalofonos HP, Theocharis AD. Resistance to hormone therapy in breast cancer cells promotes autophagy and EGFR signaling pathway. Am J Physiol Cell Physiol 2023; 325:C708-C720. [PMID: 37575061 PMCID: PMC10625825 DOI: 10.1152/ajpcell.00199.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 07/13/2023] [Accepted: 07/26/2023] [Indexed: 08/15/2023]
Abstract
Breast cancer is the leading cause of cancer deaths for women worldwide. Endocrine therapies represent the cornerstone for hormone-dependent breast cancer treatment. However, in many cases, endocrine resistance is induced with poor prognosis for patients. In the current study, we have developed MCF-7 cell lines resistant to fulvestrant (MCF-7Fulv) and tamoxifen (MCF-7Tam) aiming at investigating mechanisms underlying resistance. Both resistant cell lines exerted lower proliferation capacity in two-dimensional (2-D) cultures but retain estrogen receptor α (ERα) expression and proliferate independent of the presence of estrogens. The established cell lines tend to be more aggressive exhibiting advanced capacity to form colonies, increased expression of epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), and heterodimerization of ERBB family receptors and activation of EGFR downstream pathways like MEK/ERK1/2 and PI3K/AKT. Tyrosine kinase inhibitors tested against resistant MCF-7Fulv and MCF-7Tam cells showed moderate efficacy to inhibit cell proliferation, except for lapatinib, which concomitantly inhibits both EGFR and HER2 receptors and strongly reduced cell proliferation. Furthermore, increased autophagy was observed in resistant MCF-7Fulv and MCF-7Tam cells as shown by the presence of autophagosomes and increased Beclin-1 levels. The increased autophagy in resistant cells is not associated with increased apoptosis, suggesting a cytoprotective role for autophagy that may favor cells' survival and aggressiveness. Thus, by exploiting those underlying mechanisms, new targets could be established to overcome endocrine resistance.NEW & NOTEWORTHY The development of resistance to hormone therapy caused by both fulvestrant and tamoxifen promotes autophagy with concomitant apoptosis evasion, rendering cells capable of surviving and growing. The fact that resistance also triggers ERBB family signaling pathways, which are poorly inhibited by tyrosine kinase inhibitors might attribute to cells' aggressiveness. It is obvious that the development of endocrine therapy resistance involves a complex interplay between deregulated ERBB signaling and autophagy that may be considered in clinical practice.
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Affiliation(s)
- Konstantinos E Siatis
- Biochemistry, Biochemical Analysis and Matrix Pathobiology Research Group, Laboratory of Biochemistry, Department of Chemistry, University of Patras, Rio, Greece
- Clinical Oncology Laboratory, Division of Oncology, Department of Medicine, University of Patras, Rio, Greece
| | - Efstathia Giannopoulou
- Clinical Oncology Laboratory, Division of Oncology, Department of Medicine, University of Patras, Rio, Greece
| | - Dimitra Manou
- Biochemistry, Biochemical Analysis and Matrix Pathobiology Research Group, Laboratory of Biochemistry, Department of Chemistry, University of Patras, Rio, Greece
| | - Panagiotis Sarantis
- Molecular Oncology Unit, Department of Biological Chemistry, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Michalis V Karamouzis
- Molecular Oncology Unit, Department of Biological Chemistry, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Sofia Raftopoulou
- Electron Microscopy Laboratory, Faculty of Crop Production, Agricultural University of Athens, Athens, Greece
| | - Konstantinos Fasseas
- Electron Microscopy Laboratory, Faculty of Crop Production, Agricultural University of Athens, Athens, Greece
| | - Fatimah Mohammed Alzahrani
- Department of Chemistry, College of Science, Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia
| | - Haralabos P Kalofonos
- Clinical Oncology Laboratory, Division of Oncology, Department of Medicine, University of Patras, Rio, Greece
| | - Achilleas D Theocharis
- Biochemistry, Biochemical Analysis and Matrix Pathobiology Research Group, Laboratory of Biochemistry, Department of Chemistry, University of Patras, Rio, Greece
- Department of Chemistry, College of Science, Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia
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Mohr CJ, Schroth W, Mürdter TE, Gross D, Maier S, Stegen B, Dragoi A, Steudel FA, Stehling S, Hoppe R, Madden S, Ruth P, Huber SM, Brauch H, Lukowski R. Subunits of BK channels promote breast cancer development and modulate responses to endocrine treatment in preclinical models. Br J Pharmacol 2020; 179:2906-2924. [PMID: 32468618 DOI: 10.1111/bph.15147] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Revised: 03/20/2020] [Accepted: 05/13/2020] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND AND PURPOSE Pore-forming α subunits of the voltage- and Ca2+ -activated K+ channel with large conductance (BKα) promote malignant phenotypes of breast tumour cells. Auxiliary subunits such as the leucine-rich repeat containing 26 (LRRC26) protein, also termed BKγ1, may be required to permit activation of BK currents at a depolarized resting membrane potential that frequently occur in non-excitable tumour cells. EXPERIMENTAL APPROACH Anti-tumour effects of BKα loss were investigated in breast tumour-bearing MMTV-PyMT transgenic BKα knockout (KO) mice, primary MMTV-PyMT cell cultures, and in a syngeneic transplantation model of breast cancer derived from these cells. The therapeutic relevance of BK channels in the context of endocrine treatment was assessed in human breast cancer cell lines expressing either low (MCF-7) or high (MDA-MB-453) levels of BKα and BKγ1, as well as in BKα-negative MDA-MB-157. KEY RESULTS BKα promoted breast cancer onset and overall survival in preclinical models. Conversely, lack of BKα and/or knockdown of BKγ1 attenuated proliferation of murine and human breast cancer cells in vitro. At low concentrations, tamoxifen and its major active metabolites stimulated proliferation of BKα/γ1-positive breast cancer cells, independent of the genomic signalling controlled by the oestrogen receptor. Finally, tamoxifen increased the relative survival time of BKα KO but not of wild-type tumour cell recipient mice. CONCLUSION AND IMPLICATIONS Breast cancer initiation, progression, and tamoxifen sensitivity depend on functional BK channels thereby providing a rationale for the future exploration of the oncogenic actions of BK channels in clinical outcomes with anti-oestrogen therapy.
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Affiliation(s)
- Corinna J Mohr
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany.,Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tuebingen, Germany
| | - Werner Schroth
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tuebingen, Germany
| | - Thomas E Mürdter
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tuebingen, Germany
| | - Dominic Gross
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany
| | - Selina Maier
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany.,Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tuebingen, Germany
| | - Benjamin Stegen
- Department of Radiation Oncology, University of Tuebingen, Tuebingen, Germany
| | - Alice Dragoi
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany
| | - Friederike A Steudel
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany
| | - Severine Stehling
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany
| | - Reiner Hoppe
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tuebingen, Germany
| | - Stephen Madden
- RCSI Division of Population Health Sciences, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Peter Ruth
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany
| | - Stephan M Huber
- Department of Radiation Oncology, University of Tuebingen, Tuebingen, Germany
| | - Hiltrud Brauch
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tuebingen, Germany.,German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany.,iFIT-Cluster of Excellence, University of Tuebingen, Tuebingen, Germany
| | - Robert Lukowski
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany
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Al-Karagholi MAM, Gram C, Nielsen CAW, Ashina M. Targeting BK Ca Channels in Migraine: Rationale and Perspectives. CNS Drugs 2020; 34:325-335. [PMID: 32060729 DOI: 10.1007/s40263-020-00706-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Large (big)-conductance calcium-activated potassium (BKCa) channels are expressed in migraine-related structures such as the cranial arteries, trigeminal ganglion and trigeminal spinal nucleus, and they play a substantial role in vascular tonus and neuronal excitability. Using synthetic BKCa channels openers was associated with headache as a frequent adverse effect in healthy volunteers. Additionally, BKCa channels are downstream molecules in migraine signalling pathways that are activated by several compounds known to provoke migraine, including calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase-activating polypeptide (PACAP) and glyceryl trinitrate (GTN). Also, there is a high affinity and a close coupling between BKCa channels and ATP-sensitive potassium (KATP) channels, the role of which has recently been established in migraine pathophysiology. These observations raise the question as to whether direct BKCa channel activation can provoke migraine in migraine patients, and whether the BKCa channel could be a potential novel anti-migraine target. Hence, randomized and placebo-controlled clinical studies on BKCa channel openers or blockers in migraine patients are needed.
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Affiliation(s)
- Mohammad Al-Mahdi Al-Karagholi
- Danish Headache Center, Department of Neurology, University of Copenhagen, Valdemar Hansen Vej 5, 2600, Glostrup, Denmark
| | - Christian Gram
- Danish Headache Center, Department of Neurology, University of Copenhagen, Valdemar Hansen Vej 5, 2600, Glostrup, Denmark
| | - Cherie Amalie Waldorff Nielsen
- Danish Headache Center, Department of Neurology, University of Copenhagen, Valdemar Hansen Vej 5, 2600, Glostrup, Denmark
| | - Messoud Ashina
- Danish Headache Center, Department of Neurology, University of Copenhagen, Valdemar Hansen Vej 5, 2600, Glostrup, Denmark. .,Glostrup Research Park, Rigshospitalet Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Glostrup, Denmark.
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The molecular nature of the 17β-Estradiol binding site in the voltage- and Ca 2+-activated K + (BK) channel β1 subunit. Sci Rep 2019; 9:9965. [PMID: 31292456 PMCID: PMC6620312 DOI: 10.1038/s41598-019-45942-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 06/17/2019] [Indexed: 01/14/2023] Open
Abstract
The accessory β1 subunit modulates the Ca2+- and voltage-activated K+ (BK) channel gating properties mainly by increasing its apparent Ca2+ sensitivity. β1 plays an important role in the modulation of arterial tone and blood pressure by vascular smooth muscle cells (SMCs). 17β-estradiol (E2) increases the BK channel open probability (Po) in SMCs, through a β1 subunit-dependent modulatory effect. Here, using molecular modeling, bioinformatics, mutagenesis, and electrophysiology, we identify a cluster of hydrophobic residues in the second transmembrane domain of the β1 subunit, including the residues W163 and F166, as the binding site for E2. We further show that the increase in Po induced by E2 is associated with a stabilization of the voltage sensor in its active configuration and an increase in the coupling between the voltage sensor activation and pore opening. Since β1 is a key molecular player in vasoregulation, the findings reported here are of importance in the design of novel drugs able to modulate BK channels.
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Wang F, Chen Q, Huang G, Guo X, Li N, Li Y, Li B. BKCa participates in E2 inducing endometrial adenocarcinoma by activating MEK/ERK pathway. BMC Cancer 2018; 18:1128. [PMID: 30445932 PMCID: PMC6240221 DOI: 10.1186/s12885-018-5027-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 10/31/2018] [Indexed: 11/10/2022] Open
Abstract
Background The large-conductance, voltage-gated, calcium (Ca (2+))-activated potassium channel (BKCa) plays an important role in regulating Ca (2+) signaling and cell physiological function, and is aberrantly expressed in some types of cancers. The present study focuses on identifying the oncogenic potential and clinical significance of BKCa in endometrial adenocarcinoma, as well as exploring the mechanistic relevance by 17β -estradiol (E2) inducing aberrant activation of MEK1/2 and ERK1/2 via BKCa. Methods The expression of BKCa, ERK1/2 and p-ERK1/2 were examined by immunohistochemical staining in 263 cases, including 185 primary types I endometrial cancer tissues, 38 atypical endometrial hyperplasia tissues and 40 normal endometrium tissues. Cell growth, cycle, apoptosis rate, migration and invasion was separately tested in Ishikawa cells using siRNA-BKCa and/or E2 treatment, as well as the expression of these interested proteins by western blot analysis. Results We showed that expression of BKCa is significantly elevated in 185 types I endometrial adenocarcinoma tissues compared to those of the normal endometrium and atypical endometrial hyperplasia tissues. Furthermore, in vitro observations revealed that down-regulation of BKCa expression inhibited cell growth by both enhancing apoptosis and blocking G1/S transition, suppressed cell migration and invasion in Ishakiwa cells, and decreased the expression of p-MEK1/2 and p-ERK1/2. Additionally, RNAi-mediated knockdown of BKCa attenuated the increased cellular growth and invasion, as well as the elevated expression of p-MEK1/2 and p-ERK1/2 proteins, induced by E2 stimulation. More importantly, the aberrant expression of BKCa and p-ERK1/2 were closely related with poor prognostic factors in type I endometrial cancer, and up-regulated expression of p-ERK1/2 was significantly associated with shorter disease-free survival (DFS) and overall survival (OS) and was an independent prognostic factor in type I endometrial cancer patients. Conclusion Our results demonstrated that BKCa and the key downstream effectors p-ERK1/2 could be involved in important signaling pathways in initiation and development of endometrial adenocarcinoma and may provide a new therapeutic approach for women with endometrial cancer. Electronic supplementary material The online version of this article (10.1186/s12885-018-5027-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Fenfen Wang
- Department of Gynecologic Oncology, Women's Hospital, Zhejiang University, School of Medicine, Xueshi Road 1, Hangzhou, Zhejiang, 310006, People's Republic of China
| | - Qin Chen
- Department of Pathology, Women's Hospital, Zhejiang University, School of Medicine, Xueshi Road 1, Hangzhou, Zhejiang, 310006, People's Republic of China
| | - Genping Huang
- Department of Gynecologic Oncology, Women's Hospital, Zhejiang University, School of Medicine, Xueshi Road 1, Hangzhou, Zhejiang, 310006, People's Republic of China
| | - Xuedong Guo
- Department of Gynecologic Oncology, Women's Hospital, Zhejiang University, School of Medicine, Xueshi Road 1, Hangzhou, Zhejiang, 310006, People's Republic of China
| | - Na Li
- Department of Gynecologic Oncology, Women's Hospital, Zhejiang University, School of Medicine, Xueshi Road 1, Hangzhou, Zhejiang, 310006, People's Republic of China
| | - Yang Li
- Department of Gynecologic Oncology, Women's Hospital, Zhejiang University, School of Medicine, Xueshi Road 1, Hangzhou, Zhejiang, 310006, People's Republic of China
| | - Baohua Li
- Department of Gynecologic Oncology, Women's Hospital, Zhejiang University, School of Medicine, Xueshi Road 1, Hangzhou, Zhejiang, 310006, People's Republic of China.
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Goda AA, Siddique AB, Mohyeldin M, Ayoub NM, El Sayed KA. The Maxi-K (BK) Channel Antagonist Penitrem A as a Novel Breast Cancer-Targeted Therapeutic. Mar Drugs 2018; 16:md16050157. [PMID: 29751615 PMCID: PMC5983288 DOI: 10.3390/md16050157] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 05/06/2018] [Accepted: 05/09/2018] [Indexed: 12/24/2022] Open
Abstract
Breast cancer (BC) is a heterogeneous disease with different molecular subtypes. The high conductance calcium-activated potassium channels (BK, Maxi-K channels) play an important role in the survival of some BC phenotypes, via membrane hyperpolarization and regulation of cell cycle. BK channels have been implicated in BC cell proliferation and invasion. Penitrems are indole diterpene alkaloids produced by various terrestrial and marine Penicillium species. Penitrem A (1) is a selective BK channel antagonist with reported antiproliferative and anti-invasive activities against multiple malignancies, including BC. This study reports the high expression of BK channel in different BC subtypes. In silico BK channel binding affinity correlates with the antiproliferative activities of selected penitrem analogs. 1 showed the best binding fitting at multiple BK channel crystal structures, targeting the calcium-sensing aspartic acid moieties at the calcium bowel and calcium binding sites. Further, 1 reduced the levels of BK channel expression and increased expression of TNF-α in different BC cell types. Penitrem A (1) induced G1 cell cycle arrest of BC cells, and induced upregulation of the arrest protein p27. Combination treatment of 1 with targeted anti-HER drugs resulted in synergistic antiproliferative activity, which was associated with reduced EGFR and HER2 receptor activation, as well as reduced active forms of AKT and STAT3. Collectively, the BK channel antagonists represented by penitrem A can be novel sensitizing, chemotherapeutics synergizing, and therapeutic agents for targeted BC therapy.
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Affiliation(s)
- Amira A Goda
- Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, 1800 Bienville Drive, Monroe, LA 71201, USA.
| | - Abu Bakar Siddique
- Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, 1800 Bienville Drive, Monroe, LA 71201, USA.
| | - Mohamed Mohyeldin
- Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, 1800 Bienville Drive, Monroe, LA 71201, USA.
- Department of Pharmacognosy, Faculty of Pharmacy, Alexandria University, Alexandria 21521, Egypt.
| | - Nehad M Ayoub
- Department of Clinical Pharmacy, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid 22110, Jordan.
| | - Khalid A El Sayed
- Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, 1800 Bienville Drive, Monroe, LA 71201, USA.
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Lorca RA, Wakle‐Prabagaran M, Freeman WE, Pillai MK, England SK. The large-conductance voltage- and Ca 2+ -activated K + channel and its γ1-subunit modulate mouse uterine artery function during pregnancy. J Physiol 2018; 596:1019-1033. [PMID: 29319186 PMCID: PMC5851882 DOI: 10.1113/jp274524] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 01/05/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The uterine artery (UA) markedly vasodilates during pregnancy to direct blood flow to the developing fetus. Inadequate UA vasodilatation leads to intrauterine growth restriction and fetal death. The large-conductance voltage- and Ca2+ -activated K+ (BKCa ) channel promotes UA vasodilatation during pregnancy. We report that BKCa channel activation increases the UA diameter at late pregnancy stages in mice. Additionally, a BKCa channel auxiliary subunit, γ1, participates in this process by increasing channel activation and inducing UA vasodilatation at late pregnancy stages. Our results highlight the importance of the BKCa channel and its γ1-subunit for UA functional changes during pregnancy. ABSTRACT Insufficient vasodilatation of the uterine artery (UA) during pregnancy leads to poor utero-placental perfusion, contributing to intrauterine growth restriction and fetal loss. Activity of the large-conductance Ca2+ -activated K+ (BKCa ) channel increases in the UA during pregnancy, and its inhibition reduces uterine blood flow, highlighting a role of this channel in UA adaptation to pregnancy. The auxiliary γ1-subunit increases BKCa activation in vascular smooth muscle, but its role in pregnancy-associated UA remodelling is unknown. We explored whether the BKCa and its γ1-subunit contribute to UA remodelling during pregnancy. Doppler imaging revealed that, compared to UAs from wild-type (WT) mice, UAs from BKCa knockout (BKCa-/- ) mice had lower resistance at pregnancy day 14 (P14) but not at P18. Lumen diameters were twofold larger in pressurized UAs from P18 WT mice than in those from non-pregnant mice, but this difference was not seen in UAs from BKCa-/- mice. UAs from pregnant WT mice constricted 20-50% in response to the BKCa blocker iberiotoxin (IbTX), whereas UAs from non-pregnant WT mice only constricted 15%. Patch-clamp analysis of WT UA smooth muscle cells confirmed that BKCa activity increased over pregnancy, showing three distinct voltage sensitivities. The γ1-subunit transcript increased 7- to 10-fold during pregnancy. Furthermore, γ1-subunit knockdown reduced IbTX sensitivity in UAs from pregnant mice, whereas γ1-subunit overexpression increased IbTX sensitivity in UAs from non-pregnant mice. Finally, at P18, γ1-knockout (γ1-/- ) mice had smaller UA diameters than WT mice, and IbTX-mediated vasoconstriction was prevented in UAs from γ1-/- mice. Our results suggest that the γ1-subunit increases BKCa activation in UAs during pregnancy.
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Affiliation(s)
- Ramón A. Lorca
- Center for Reproductive Health SciencesDepartment of Obstetrics and GynecologyWashington University in St Louis School of MedicineSt LouisMO63110USA
| | - Monali Wakle‐Prabagaran
- Center for Reproductive Health SciencesDepartment of Obstetrics and GynecologyWashington University in St Louis School of MedicineSt LouisMO63110USA
| | - William E. Freeman
- Center for Reproductive Health SciencesDepartment of Obstetrics and GynecologyWashington University in St Louis School of MedicineSt LouisMO63110USA
| | - Meghan K. Pillai
- Center for Reproductive Health SciencesDepartment of Obstetrics and GynecologyWashington University in St Louis School of MedicineSt LouisMO63110USA
| | - Sarah K. England
- Center for Reproductive Health SciencesDepartment of Obstetrics and GynecologyWashington University in St Louis School of MedicineSt LouisMO63110USA
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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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Kow LM, Pfaff DW. Rapid estrogen actions on ion channels: A survey in search for mechanisms. Steroids 2016; 111:46-53. [PMID: 26939826 PMCID: PMC4929851 DOI: 10.1016/j.steroids.2016.02.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 02/22/2016] [Accepted: 02/25/2016] [Indexed: 12/31/2022]
Abstract
A survey of nearly two hundred reports shows that rapid estrogenic actions can be detected across a range of kinds of estrogens, a range of doses, on a wide range of tissue, cell and ion channel types. Striking is the fact that preparations of estrogenic agents that do not permeate the cell membrane almost always mimic the actions of the estrogenic agents that do permeate the membrane. All kinds of estrogens, ranging from natural ones, through receptor modulators, endocrine disruptors, phytoestrogens, agonists, and antagonists to novel G-1 and STX, have been reported to be effective. For actions on specific types of ion channels, the possibility of opposing actions, in different cases, is the rule, not the exception. With this variety there is no single, specific action mechanism for estrogens per se, although in some cases estrogens can act directly or via some signaling pathways to affect ion channels. We infer that estrogens can bind a large number of substrates/receptors at the membrane surface. As against the variety of subsequent routes of action, this initial step of the estrogen's binding action is the key.
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Affiliation(s)
- Lee-Ming Kow
- The Rockefeller University, New York, NY 10065, USA.
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10
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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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11
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Zhang YY, Li G, Che H, Sun HY, Li X, Au WK, Xiao GS, Wang Y, Li GR. Characterization of functional ion channels in human cardiac c-kit+ progenitor cells. Basic Res Cardiol 2014; 109:407. [DOI: 10.1007/s00395-014-0407-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 01/27/2014] [Accepted: 02/25/2014] [Indexed: 12/17/2022]
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12
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Hydrogen sulfide augments the proliferation and survival of human induced pluripotent stem cell–derived mesenchymal stromal cells through inhibition of BKCa. Cytotherapy 2013; 15:1395-405. [DOI: 10.1016/j.jcyt.2013.06.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 05/09/2013] [Accepted: 06/16/2013] [Indexed: 01/01/2023]
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13
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Williams S, Bateman A, O'Kelly I. Altered expression of two-pore domain potassium (K2P) channels in cancer. PLoS One 2013; 8:e74589. [PMID: 24116006 PMCID: PMC3792113 DOI: 10.1371/journal.pone.0074589] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 08/03/2013] [Indexed: 01/31/2023] Open
Abstract
Potassium channels have become a focus in cancer biology as they play roles in cell behaviours associated with cancer progression, including proliferation, migration and apoptosis. Two-pore domain (K2P) potassium channels are background channels which enable the leak of potassium ions from cells. As these channels are open at rest they have a profound effect on cellular membrane potential and subsequently the electrical activity and behaviour of cells in which they are expressed. The K2P family of channels has 15 mammalian members and already 4 members of this family (K2P2.1, K2P3.1, K2P9.1, K2P5.1) have been implicated in cancer. Here we examine the expression of all 15 members of the K2P family of channels in a range of cancer types. This was achieved using the online cancer microarray database, Oncomine (www.oncomine.org). Each gene was examined across 20 cancer types, comparing mRNA expression in cancer to normal tissue. This analysis revealed all but 3 K2P family members (K2P4.1, K2P16.1, K2P18.1) show altered expression in cancer. Overexpression of K2P channels was observed in a range of cancers including breast, leukaemia and lung while more cancers (brain, colorectal, gastrointestinal, kidney, lung, melanoma, oesophageal) showed underexpression of one or more channels. K2P1.1, K2P3.1, K2P12.1, were overexpressed in a range of cancers. While K2P1.1, K2P3.1, K2P5.1, K2P6.1, K2P7.1 and K2P10.1 showed significant underexpression across the cancer types examined. This analysis supports the view that specific K2P channels may play a role in cancer biology. Their altered expression together with their ability to impact the function of other ion channels and their sensitivity to environmental stimuli (pO2, pH, glucose, stretch) makes understanding the role these channels play in cancer of key importance.
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Affiliation(s)
- Sarah Williams
- Human Development and Health, Centre for Human Development, Stem Cells and Regeneration, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Andrew Bateman
- Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Ita O'Kelly
- Human Development and Health, Centre for Human Development, Stem Cells and Regeneration, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
- * E-mail: I.M.O'
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14
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Inhibition of vacuolar H+ ATPase enhances sensitivity to tamoxifen via up-regulation of CHOP in breast cancer cells. Biochem Biophys Res Commun 2013; 437:463-8. [DOI: 10.1016/j.bbrc.2013.06.106] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 06/27/2013] [Indexed: 10/26/2022]
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15
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Gackière F, Warnier M, Katsogiannou M, Derouiche S, Delcourt P, Dewailly E, Slomianny C, Humez S, Prevarskaya N, Roudbaraki M, Mariot P. Functional coupling between large-conductance potassium channels and Cav3.2 voltage-dependent calcium channels participates in prostate cancer cell growth. Biol Open 2013; 2:941-51. [PMID: 24143281 PMCID: PMC3773341 DOI: 10.1242/bio.20135215] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 06/26/2013] [Indexed: 12/11/2022] Open
Abstract
It is strongly suspected that potassium (K+) channels are involved in various aspects of prostate cancer development, such as cell growth. However, the molecular nature of those K+ channels implicated in prostate cancer cell proliferation and the mechanisms through which they control proliferation are still unknown. This study uses pharmacological, biophysical and molecular approaches to show that the main voltage-dependent K+ current in prostate cancer LNCaP cells is carried by large-conductance BK channels. Indeed, most of the voltage-dependent current was inhibited by inhibitors of BK channels (paxillin and iberiotoxin) and by siRNA targeting BK channels. In addition, we reveal that BK channels constitute the main K+ channel family involved in setting the resting membrane potential in LNCaP cells at around −40 mV. This consequently promotes a constitutive calcium entry through T-type Cav3.2 calcium channels. We demonstrate, using single-channel recording, confocal imaging and co-immunoprecipitation approaches, that both channels form macromolecular complexes. Finally, using flow cytometry cell cycle measurements, cell survival assays and Ki67 immunofluorescent staining, we show that both BK and Cav3.2 channels participate in the proliferation of prostate cancer cells.
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Affiliation(s)
- Florian Gackière
- Laboratoire de Physiologie Cellulaire, INSERM U1003, Bâtiment SN3, Université Lille 1 , 59655 Villeneuve d'Ascq Cédex , France
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16
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Weiger TM, Hermann A. Cell proliferation, potassium channels, polyamines and their interactions: a mini review. Amino Acids 2013; 46:681-8. [PMID: 23820618 DOI: 10.1007/s00726-013-1536-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 06/13/2013] [Indexed: 01/18/2023]
Abstract
Polyamines, which are obligatory molecules involved in cell cycling and proliferation, are subject to a change in their free intracellular concentrations during the cell cycle. Potassium (K(+)) channels are also considered, but less well recognized, to be necessary for cell proliferation by either hyperpolarizing or depolarizing cells during the cell cycle. A block of polyamine synthesis as well as block or knockout of K(+) channels can halt cell proliferation. K(+) channels like BK (maxi calcium (Ca(2+))-activated K(+)), Kir (inward rectifier), M-type K(+)-and TASK (two-pore domain K(+)) channels or the delayed rectifier K(+) channels are modulated in their electrical properties by polyamines. Polyamines are most effective in blocking these channels when applied to the intracellular face of these channels except for TASK channels where they act only from the extracellular side. Quinidine, a general K(+) channel blocker, was found to reduce putrescine concentrations, to block the ornithine decarboxylase and halt cell proliferation. From these results, the question arises if there is an interaction between polyamines, K(+) channels and proliferation. It might be speculated that a decrease of intracellular polyamines allows more K(+) channels to be active, thus inducing hyperpolarization, while an increase of the polyamine concentration may block K(+) channel activity leading to depolarization of the membrane potential. On the other hand, a block or a deletion of K(+) channels may cause a decrease of the polyamine concentration in cells. More research is needed to test these hypotheses.
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Affiliation(s)
- Thomas M Weiger
- Division of Cellular and Molecular Neurobiology, Department of Cell Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020, Salzburg, Austria,
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17
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Single Mechanosensitive and Ca2+-Sensitive Channel Currents Recorded from Mouse and Human Embryonic Stem Cells. J Membr Biol 2012. [DOI: 10.1007/s00232-012-9523-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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18
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Abstract
KCNMA1 encodes the α-subunit of the large conductance, voltage and Ca2+-activated (BK) potassium channel and has been reported as a target gene of genomic amplification at 10q22 in prostate cancer. To investigate the prevalence of the amplification in other human cancers, the copy number of KCNMA1 was analyzed by fluorescence-in-situ-hybridization (FISH) in 2,445 tumors across 118 different tumor types. Amplification of KCNMA1 was restricted to a small but distinct fraction of breast, ovarian and endometrial cancer with the highest prevalence in invasive ductal breast cancers and serous carcinoma of ovary and endometrium (3–7%). We performed an extensive analysis on breast cancer tissue microarrays (TMA) of 1,200 tumors linked to prognosis. KCNMA1 amplification was significantly associated with high tumor stage, high grade, high tumor cell proliferation, and poor prognosis. Immunofluorescence revealed moderate or strong KCNMA1 protein expression in 8 out of 9 human breast cancers and in the breast cancer cell line MFM223. KCNMA1-function in breast cancer cell lines was confirmed by whole-cell patch clamp recordings and proliferation assays, using siRNA-knockdown, BK channel activators such as 17ß-estradiol and the BK-channel blocker paxilline. Our findings revealed that enhanced expression of KCNMA1 correlates with and contributes to high proliferation rate and malignancy of breast cancer.
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Ge L, Hoa NT, Cornforth AN, Bota DA, Mai A, Kim DI, Chiou SK, Hickey MJ, Kruse CA, Jadus MR. Glioma big potassium channel expression in human cancers and possible T cell epitopes for their immunotherapy. THE JOURNAL OF IMMUNOLOGY 2012; 189:2625-34. [PMID: 22844111 DOI: 10.4049/jimmunol.1102965] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Big potassium (BK) ion channels have several spliced variants. One spliced variant initially described within human glioma cells is the glioma BK (gBK) channel. This isoform consists of 34 aa inserted into the intracellular region of the basic BK ion channel. PCR primers specific for this inserted region confirmed that human glioma cell lines and freshly resected surgical tissues from glioblastoma multiforme patients strongly expressed gBK mRNA. Normal human brain tissue very weakly expressed this transcript. An Ab specific for this gBK isoform confirmed that human glioma cells displayed this protein in the cell membrane, mitochondria, Golgi, and endoplasmic reticulum. Within the gBK region, two putative epitopes (gBK1 and gBK2) are predicted to bind to the HLA-A*0201 molecule. HLA-A*0201-restricted human CTLs were generated in vitro using gBK peptide-pulsed dendritic cells. Both gBK1 and gBK2 peptide-specific CTLs killed HLA-A2⁺/gBK⁺ gliomas, but they failed to kill non-HLA-A2-expressing but gBK⁺ target cells in cytolytic assays. T2 cells loaded with exogenous gBK peptides, but not with the influenza M1 control peptide, were only killed by their respective CTLs. The gBK-specific CTLs also killed a variety of other HLA-A*0201⁺ cancer cells that possess gBK, as well as HLA-A2⁺ HEK cells transfected with the gBK gene. Of clinical relevance, we found that T cells derived from glioblastoma multiforme patients that were sensitized to the gBK peptide could also kill target cells expressing gBK. This study shows that peptides derived from cancer-associated ion channels maybe useful targets for T cell-mediated immunotherapy.
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Affiliation(s)
- Lisheng Ge
- Diagnostic and Molecular Health Care Group, Long Beach, CA 90822, USA
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20
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Zhang J, Chan YC, Ho JCY, Siu CW, Lian Q, Tse HF. Regulation of cell proliferation of human induced pluripotent stem cell-derived mesenchymal stem cells via ether-à-go-go 1 (hEAG1) potassium channel. Am J Physiol Cell Physiol 2012; 303:C115-25. [DOI: 10.1152/ajpcell.00326.2011] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The successful generation of a high yield of mesenchymal stem cells (MSCs) from human induced pluripotent stem cells (iPSCs) may represent an unlimited cell source with superior therapeutic benefits for tissue regeneration to bone marrow (BM)-derived MSCs. We investigated whether the differential expression of ion channels in iPSC-MSCs was responsible for their higher proliferation capacity than BM-MSCs. The expression of ion channels for K+, Na+, Ca2+, and Cl− was examined by RT-PCR. The electrophysiological properties of iPSC-MSCs and BM-MSCs were then compared by patch-clamp experiments to verify their functional roles. Significant mRNA expression of ion channel genes including KCa1.1, KCa3.1, KCNH1, Kir2.1, SCN9A, CACNA1C, and Clcn3 was observed in both human iPSC-MSCs and BM-MSCs, whereas Kir2.2 and Kir2.3 were only detected in human iPSC-MSCs. Five types of currents [big-conductance Ca2+-activated K+ current (BKCa), delayed rectifier K+ current ( IKDR), inwardly rectifying K+ current ( IKir), Ca2+-activated K+ current ( IKCa), and chloride current ( ICl)] were found in iPSC-MSCs (83%, 47%, 11%, 5%, and 4%, respectively) but only four of them (BKCa, IKDR, IKir, and IKCa) were identified in BM-MSCs (76%, 25%, 22%, and 11%, respectively). Cell proliferation was examined with MTT or bromodeoxyuridine assay, and doubling times were 2.66 and 3.72 days for iPSC-MSCs and BM-MSCs, respectively, showing a 1.4-fold discrepancy. Blockade of IKDR with short hairpin RNA or human ether-à-go-go 1 (hEAG1) channel blockers, 4-AP and astemizole, significantly reduced the rate of proliferation of human iPSC-MSCs. These treatments also decreased the rate of proliferation of human BM-MSCs albeit to a lesser extent. These findings demonstrate that the hEAG1 channel plays a crucial role in controlling the proliferation rate of human iPSC-MSCs and to a lesser extent in BM-MSCs.
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Affiliation(s)
- Jiao Zhang
- Cardiology Division, Department of Medicine, University of Hong Kong, Hong Kong
| | - Yau-Chi Chan
- Cardiology Division, Department of Medicine, University of Hong Kong, Hong Kong
| | - Jenny Chung-Yee Ho
- Cardiology Division, Department of Medicine, University of Hong Kong, Hong Kong
- Research Centre of Heart, Brain, Hormone, and Healthy Aging, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong; and
| | - Chung-Wah Siu
- Cardiology Division, Department of Medicine, University of Hong Kong, Hong Kong
- Research Centre of Heart, Brain, Hormone, and Healthy Aging, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong; and
| | - Qizhou Lian
- Cardiology Division, Department of Medicine, University of Hong Kong, Hong Kong
- Research Centre of Heart, Brain, Hormone, and Healthy Aging, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong; and
- Eye Institute, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Hung-Fat Tse
- Cardiology Division, Department of Medicine, University of Hong Kong, Hong Kong
- Research Centre of Heart, Brain, Hormone, and Healthy Aging, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong; and
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21
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Ma YG, Liu WC, Dong S, Du C, Wang XJ, Li JS, Xie XP, Wu L, Ma DC, Yu ZB, Xie MJ. Activation of BK(Ca) channels in zoledronic acid-induced apoptosis of MDA-MB-231 breast cancer cells. PLoS One 2012; 7:e37451. [PMID: 22655048 PMCID: PMC3360057 DOI: 10.1371/journal.pone.0037451] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 04/20/2012] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Zoledronic acid, one of the most potent nitrogen-containing biphosphonates, has been demonstrated to have direct anti-tumor and anti-metastatic properties in breast cancer in vitro and in vivo. In particular, tumor-cell apoptosis has been recognized to play an important role in the treatment of metastatic breast cancer with zoledronic acid. However, the precise mechanisms remain less clear. In the present study, we investigated the specific role of large conductance Ca(2+)-activated potassium (BK(Ca)) channel in zoledronic acid-induced apoptosis of estrogen receptor (ER)-negative MDA-MB-231 breast cancer cells. METHODOLOGY/PRINCIPAL FINDINGS The action of zoledronic acid on BK(Ca) channel was investigated by whole-cell and cell-attached patch clamp techniques. Cell apoptosis was assessed with immunocytochemistry, analysis of fragmented DNA by agarose gel electrophoresis, and flow cytometry assays. Cell proliferation was investigated by MTT test and immunocytochemistry. In addition, such findings were further confirmed with human embryonic kidney 293 (HEK293) cells which were transfected with functional BK(Ca) α-subunit (hSloα). Our results clearly indicated that zoledronic acid directly increased the activities of BK(Ca) channels, and then activation of BK(Ca) channel by zoledronic acid contributed to induce apoptosis in MDA-MB-231 cells. The possible mechanisms were associated with the elevated level of intracellular Ca(2+) and a concomitant depolarization of mitochondrial membrane potential (Δψm) in MDA-MB-231 cells. CONCLUSIONS Activation of BK(Ca) channel was here shown to be a novel molecular pathway involved in zoledronic acid-induced apoptosis of MDA-MB-231 cells in vitro.
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Affiliation(s)
- Yu-Guang Ma
- Department of Clinical Oncology, Xijing Hospital, Fourth Military Medical University, Xi'an, China
- Department of Breast Disease, First Hospital of Lanzhou University, Lanzhou, China
| | - Wen-Chao Liu
- Department of Clinical Oncology, Xijing Hospital, Fourth Military Medical University, Xi'an, China
- * E-mail: (WCL); (MJX)
| | - Shuo Dong
- Department of Medicine, Baylor College of Medicine, Houston, United States of America
| | - Cheng Du
- Department of Clinical Oncology, Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Xiao-Jun Wang
- Key Laboratory of Aerospace Medicine, Department of Aerospace Physiology, Fourth Military Medical University, Ministry of China, Xi'an, China
| | - Jin-Sheng Li
- Key Laboratory of Aerospace Medicine, Department of Aerospace Physiology, Fourth Military Medical University, Ministry of China, Xi'an, China
| | - Xiao-Ping Xie
- Key Laboratory of Aerospace Medicine, Department of Aerospace Physiology, Fourth Military Medical University, Ministry of China, Xi'an, China
| | - Li Wu
- Department of Breast Disease, First Hospital of Lanzhou University, Lanzhou, China
| | - Da-Chang Ma
- Department of Breast Disease, First Hospital of Lanzhou University, Lanzhou, China
| | - Zhi-Bin Yu
- Key Laboratory of Aerospace Medicine, Department of Aerospace Physiology, Fourth Military Medical University, Ministry of China, Xi'an, China
| | - Man-Jiang Xie
- Key Laboratory of Aerospace Medicine, Department of Aerospace Physiology, Fourth Military Medical University, Ministry of China, Xi'an, China
- * E-mail: (WCL); (MJX)
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22
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Kim Y, Kim WJ, Cha EJ. Quercetin-induced Growth Inhibition in Human Bladder Cancer Cells Is Associated with an Increase in Ca-activated K Channels. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2011; 15:279-83. [PMID: 22128260 DOI: 10.4196/kjpp.2011.15.5.279] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 10/03/2011] [Accepted: 10/09/2011] [Indexed: 12/25/2022]
Abstract
Quercetin (3,3',4',5,7-pentahydroxyflavone) is an attractive therapeutic flavonoid for cancer treatment because of its beneficial properties including apoptotic, antioxidant, and antiproliferative effects on cancer cells. However, the exact mechanism of action of quercetin on ion channel modulation is poorly understood in bladder cancer 253J cells. In this study, we demonstrated that large conductance Ca(2+)-activated K(+) (BK(Ca)) or MaxiK channels were functionally expressed in 253J cells, and quercetin increased BK(Ca) current in a concentration dependent and reversible manner using a whole cell patch configuration. The half maximal activation concentration (IC(50)) of quercetin was 45.5±7.2 µM. The quercetin-evoked BK(Ca) current was inhibited by tetraethylammonium (TEA; 5 mM) a non-specific BK(Ca) blocker and iberiotoxin (IBX; 100 nM) a BK(Ca)-specific blocker. Quercetin-induced membrane hyperpolarization was measured by fluorescence-activated cell sorting (FACS) with voltage sensitive dye, bis (1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC(4)(3); 100 nM). Quercetin-evoked hyperpolarization was prevented by TEA. Quercetin produced an antiproliferative effect (30.3±13.5%) which was recovered to 53.3±10.5% and 72.9±3.7% by TEA and IBX, respectively. Taken together our results indicate that activation of BK(Ca) channels may be considered an important target related to the action of quercetin on human bladder cancer cells.
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Affiliation(s)
- Yangmi Kim
- Department of Physiology, Chungbuk National University, Cheongju 361-763, Korea
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23
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Effects of ion channels on proliferation in cultured human cardiac fibroblasts. J Mol Cell Cardiol 2011; 51:198-206. [DOI: 10.1016/j.yjmcc.2011.05.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 04/24/2011] [Accepted: 05/11/2011] [Indexed: 01/01/2023]
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24
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Wallace JL, Gow IF, Warnock M. The life and death of breast cancer cells: proposing a role for the effects of phytoestrogens on potassium channels. J Membr Biol 2011; 242:53-67. [PMID: 21728044 DOI: 10.1007/s00232-011-9376-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Accepted: 06/20/2011] [Indexed: 10/18/2022]
Abstract
Changes in the regulation of potassium channels are increasingly implicated in the altered activity of breast cancer cells. Increased or reduced expression of a number of K(+) channels have been identified in numerous breast cancer cell lines and cancerous tissue biopsy samples, compared to normal tissue, and are associated with tumor formation and spread, enhanced levels of proliferation, and resistance to apoptotic stimuli. Through knockout or silencing of K(+) channel genes, and use of specific or more broad pharmacologic K(+) channel blockers, the growth of numerous cell lines, including breast cancer cells, has been modified. In this manner it has been proposed that in MCF7 breast cancer cells proliferation appears to be regulated by the activity of a number of K(+) channels, including the Ca(2+) activated K(+) channels, and the voltage-gated K(+) channels hEAG and K(v)1.1. The effect of phytoestrogens on K(+) channels has not been extensively studied but yields some interesting results. In a number of cell lines the phytoestrogen genistein inhibits K(+) current through several channels including K(v)1.3 and hERG. Where it has been used, structurally similar daidzein has little or no effect on K(+) channel activity. Since many K(+) channels have roles in proliferation and apoptosis in breast cancer cells, the impact of K(+) channel regulation by phytoestrogens is of potentially great relevance.
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Affiliation(s)
- Joanne L Wallace
- School of Health Sciences, Queen Margaret University, Musselburgh, Edinburgh, Scotland, UK.
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Kang YJ, Kim IY, Kim EH, Yoon MJ, Kim SU, Kwon TK, Choi KS. Paxilline enhances TRAIL-mediated apoptosis of glioma cells via modulation of c-FLIP, survivin and DR5. Exp Mol Med 2011; 43:24-34. [PMID: 21150246 DOI: 10.3858/emm.2011.43.1.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Tumor necrosis factor-related apoptosis-induced ligand (TRAIL) induces apoptosis selectively in cancer cells while sparing normal cells. However, many cancer cells are resistant to TRAIL-induced cell death. Here, we report that paxilline, an indole alkaloid from Penicillium paxilli, can sensitize various glioma cells to TRAIL-mediated apoptosis. While treatment with TRAIL alone caused partial processing of caspase-3 to its p20 intermediate in TRAIL-resistant glioma cell lines, co-treatment with TRAIL and subtoxic doses of paxilline caused complete processing of caspase-3 into its active subunits. Paxilline treatment markedly upregulated DR5, a receptor of TRAIL, through a CHOP/GADD153-mediated process. In addition, paxilline treatment markedly downregulated the protein levels of the short form of the cellular FLICE-inhibitory protein (c-FLIPs) and the caspase inhibitor, survivin, through proteasome-mediated degradation. Taken together, these results show that paxilline effectively sensitizes glioma cells to TRAIL-mediated apoptosis by modulating multiple components of the death receptor-mediated apoptotic pathway. Interestingly, paxilline/TRAIL co-treatment did not induce apoptosis in normal astrocytes, nor did it affect the protein levels of CHOP, DR5 or survivin in these cells. Thus, combined treatment regimens involving paxilline and TRAIL may offer an attractive strategy for safely treating resistant gliomas.
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Affiliation(s)
- You Jung Kang
- Department of Molecular Science and Technology, Institute for Medical Sciences, Ajou University School of Medicine, Suwon, Korea
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Wagner V, Stadelmeyer E, Riederer M, Regitnig P, Gorischek A, Devaney T, Schmidt K, Tritthart HA, Hirschberg K, Bauernhofer T, Schreibmayer W. Cloning and characterisation of GIRK1 variants resulting from alternative RNA editing of the KCNJ3 gene transcript in a human breast cancer cell line. J Cell Biochem 2010; 110:598-608. [PMID: 20512921 DOI: 10.1002/jcb.22564] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The aim of this study was to investigate the impact of increased mRNA levels encoding GIRK1 in breast tumours on GIRK protein expression. mRNA levels encoding hGIRK1 and hGIRK4 in the MCF7, MCF10A and MDA-MB-453 breast cancer cell lines were assessed and the corresponding proteins detected using Western blots. cDNAs encoding for four hGIRK1 splice variants (hGIRK1a, 1c, 1d and 1e) were cloned from the MCF7 cell line. Subcellular localisation of fluorescence labelled hGIRK1a-e and hGIRK4 and of endogenous GIRK1 and GIRK4 subunits was monitored in the MCF7 cell line. All hGIRK1 splice variants and hGIRK4 were predominantly located within the endoplasmic reticulum. Heterologous expression in Xenopus laevis oocytes and two electrode voltage clamp experiments together with confocal microscopy were performed. Only the hGIRK1a subunit was able to form functional GIRK channels in connection with hGIRK4. The other splice variants are expressed, but exert a dominant negative effect on heterooligomeric channel function. Hence, alternative splicing of the KCNJ3 gene transcript in the MCF7 cell line leads to a family of mRNA's, encoding truncated versions of the hGIRK1 protein. The very high abundance of mRNA's encoding GIRK1 together with the presence of GIRK1 protein suggests a pathophysiological role in breast cancer.
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Affiliation(s)
- Valerie Wagner
- Institute for Biophysics, Center of Physiological Medicine, Medical University of Graz, Graz, Austria
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Calcium-activated potassium channels BK and IK1 are functionally expressed in human gliomas but do not regulate cell proliferation. PLoS One 2010; 5:e12304. [PMID: 20808839 PMCID: PMC2924897 DOI: 10.1371/journal.pone.0012304] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Accepted: 07/25/2010] [Indexed: 01/15/2023] Open
Abstract
Gliomas are morbid brain tumors that are extremely resistant to available chemotherapy and radiology treatments. Some studies have suggested that calcium-activated potassium channels contribute to the high proliferative potential of tumor cells, including gliomas. However, other publications demonstrated no role for these channels or even assigned them antitumorogenic properties. In this work we characterized the expression and functional contribution to proliferation of Ca2+-activated K+ channels in human glioblastoma cells. Quantitative RT-PCR detected transcripts for the big conductance (BK), intermediate conductance (IK1), and small conductance (SK2) K+ channels in two glioblastoma-derived cell lines and a surgical sample of glioblastoma multiforme. Functional expression of BK and IK1 in U251 and U87 glioma cell lines and primary glioma cultures was verified using whole-cell electrophysiological recordings. Inhibitors of BK (paxilline and penitrem A) and IK1 channels (clotrimazole and TRAM-34) reduced U251 and U87 proliferation in an additive fashion, while the selective blocker of SK channels UCL1848 had no effect. However, the antiproliferative properties of BK and IK1 inhibitors were seen at concentrations that were higher than those necessary to inhibit channel activity. To verify specificity of pharmacological agents, we downregulated BK and IK1 channels in U251 cells using gene-specific siRNAs. Although siRNA knockdowns caused strong reductions in the BK and IK1 current densities, neither single nor double gene silencing significantly affected rates of proliferation. Taken together, these results suggest that Ca2+-activated K+ channels do not play a critical role in proliferation of glioma cells and that the effects of pharmacological inhibitors occur through their off-target actions.
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Asano S, Tune JD, Dick GM. Bisphenol A activates Maxi-K (K(Ca)1.1) channels in coronary smooth muscle. Br J Pharmacol 2010; 160:160-70. [PMID: 20331605 DOI: 10.1111/j.1476-5381.2010.00687.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND AND PURPOSE Bisphenol A (BPA) is used to manufacture plastics, including containers for food into which it may leach. High levels of exposure to this oestrogenic endocrine disruptor are associated with diabetes and heart disease. Oestrogen and oestrogen receptor modulators increase the activity of large conductance Ca(2+)/voltage-sensitive K(+) (Maxi-K; K(Ca)1.1) channels, but the effects of BPA on Maxi-K channels are unknown. We tested the hypothesis that BPA activates Maxi-K channels through a mechanism that depends upon the regulatory beta1 subunit. EXPERIMENTAL APPROACH Patch-clamp recordings of Maxi-K channels were made in human and canine coronary smooth muscle cells as well as in AD-293 cells expressing pore-forming alpha or alpha plus beta1 subunits. KEY RESULTS BPA (10 microM) activated an outward current in smooth muscle cells that was inhibited by penitrem A (1 microM), a Maxi-K blocker. BPA increased Maxi-K activity in inside-out patches from coronary smooth muscle, but had no effect on single channel conductance. In AD-293 cells with Maxi-K channels composed of alpha subunits alone, 10 microM BPA did not affect channel activity. When channels in AD-293 cells contained beta1 subunits, 10 microM BPA increased channel activity. Effects of BPA were rapid (<1 min) and reversible. A higher concentration of BPA (100 microM) increased Maxi-K current independent of the beta1 subunit. CONCLUSIONS AND IMPLICATIONS Our data indicate that BPA increased the activity of Maxi-K channels and may represent a basis for some potential toxicological effects.
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Affiliation(s)
- Shinichi Asano
- Division of Exercise Physiology, Center for Cardiovascular & Respiratory Sciences, West Virginia University School of Medicine, Morgantown, WV, USA
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Li GR, Sun HY, Chen JB, Zhou Y, Tse HF, Lau CP. Characterization of multiple ion channels in cultured human cardiac fibroblasts. PLoS One 2009; 4:e7307. [PMID: 19806193 PMCID: PMC2751830 DOI: 10.1371/journal.pone.0007307] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Accepted: 09/14/2009] [Indexed: 01/11/2023] Open
Abstract
Background Although fibroblast-to-myocyte electrical coupling is experimentally suggested, electrophysiology of cardiac fibroblasts is not as well established as contractile cardiac myocytes. The present study was therefore designed to characterize ion channels in cultured human cardiac fibroblasts. Methods and Findings A whole-cell patch voltage clamp technique and RT-PCR were employed to determine ion channels expression and their molecular identities. We found that multiple ion channels were heterogeneously expressed in human cardiac fibroblasts. These include a big conductance Ca2+-activated K+ current (BKCa) in most (88%) human cardiac fibroblasts, a delayed rectifier K+ current (IKDR) and a transient outward K+ current (Ito) in a small population (15 and 14%, respectively) of cells, an inwardly-rectifying K+ current (IKir) in 24% of cells, and a chloride current (ICl) in 7% of cells under isotonic conditions. In addition, two types of voltage-gated Na+ currents (INa) with distinct properties were present in most (61%) human cardiac fibroblasts. One was a slowly inactivated current with a persistent component, sensitive to tetrodotoxin (TTX) inhibition (INa.TTX, IC50 = 7.8 nM), the other was a rapidly inactivated current, relatively resistant to TTX (INa.TTXR, IC50 = 1.8 µM). RT-PCR revealed the molecular identities (mRNAs) of these ion channels in human cardiac fibroblasts, including KCa.1.1 (responsible for BKCa), Kv1.5, Kv1.6 (responsible for IKDR), Kv4.2, Kv4.3 (responsible for Ito), Kir2.1, Kir2.3 (for IKir), Clnc3 (for ICl), NaV1.2, NaV1.3, NaV1.6, NaV1.7 (for INa.TTX), and NaV1.5 (for INa.TTXR). Conclusions These results provide the first information that multiple ion channels are present in cultured human cardiac fibroblasts, and suggest the potential contribution of these ion channels to fibroblast-myocytes electrical coupling.
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Affiliation(s)
- Gui-Rong Li
- Department of Medicine and Research Centre of Heart, Brain, Hormone and Healthy Aging, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China.
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Gomez-Niño A, Obeso A, Baranda JA, Santo-Domingo J, Lopez-Lopez JR, Gonzalez C. MaxiK potassium channels in the function of chemoreceptor cells of the rat carotid body. Am J Physiol Cell Physiol 2009; 297:C715-22. [PMID: 19570892 DOI: 10.1152/ajpcell.00507.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hypoxia activates chemoreceptor cells of the carotid body (CB) promoting an increase in their normoxic release of neurotransmitters. Catecholamine (CA) release rate parallels the intensity of hypoxia. Coupling of hypoxia to CA release requires cell depolarization, produced by inhibition of O(2)-regulated K(+) channels, and Ca(2+) entering the cells via voltage-operated channels. In rat chemoreceptor cells hypoxia inhibits large-conductance, calcium-sensitive K channels (maxiK) and a two-pore domain weakly inward rectifying K(+) channel (TWIK)-like acid-sensitive K(+) channel (TASK)-like channel, but the significance of maxiK is controversial. A proposal envisions maxiK contributing to set the membrane potential (E(m)) and the hypoxic response, but the proposal is denied by authors finding that maxiK inhibition does not depolarize chemoreceptor cells or alters intracellular Ca(2+) concentration or CA release in normoxia or hypoxia. We found that maxiK channel blockers (tetraethylammonium and iberiotoxin) did not modify CA release in rat chemoreceptor cells, in either normoxia or hypoxia, and iberiotoxin did not alter the Ca(2+) transients elicited by hypoxia. On the contrary, both maxiK blockers increased the responses elicited by dinitrophenol, a stimulus we demonstrate does not affect maxiK channels in isolated patches of rat chemoreceptor cells. We conclude that in rat chemoreceptor cells maxiK channels do not contribute to the genesis of the E(m), and that their full inhibition by hypoxia, preclude further inhibition by maxiK channel blockers. We suggest that full inhibition of this channel is required to generate the spiking behavior of the cells in acute hypoxia.
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Affiliation(s)
- Angela Gomez-Niño
- Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid, Superior de Investigaciones Científicas, 47005 Valladolid, Spain
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Tong M, Duncan RK. Tamoxifen inhibits BK channels in chick cochlea without alterations in voltage-dependent activation. Am J Physiol Cell Physiol 2009; 297:C75-85. [PMID: 19439526 DOI: 10.1152/ajpcell.00659.2008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Large-conductance, Ca(2+)-activated, and voltage-gated potassium channels (BK, BK(Ca), or Maxi-K) play an important role in electrical tuning in nonmammalian vertebrate hair cells. Systematic changes in tuning frequency along the tonotopic axis largely result from variations in BK channel kinetics, but the molecular changes underpinning these functional variations remain unknown. Auxiliary beta(1) have been implicated in low-frequency tuning at the cochlear apex because these subunits dramatically slow channel kinetics. Tamoxifen (Tx), a (xeno)estrogen compound known to activate BK channels through the beta-subunit, was used to test for the functional presence of beta(1). The hypotheses were that Tx would activate the majority of BK channels in hair cells from the cochlear apex due to the presence of beta(1) and that the level of activation would exhibit a tonotopic gradient following the expression profile of beta(1). Outside-out patches of BK channels were excised from tall hair cells along the apical half of the chicken basilar papilla. In low-density patches, single-channel conductance was reduced and the averaged open probability was unaffected by Tx. In high-density patches, the amplitude of ensemble-averaged BK current was inhibited, whereas half-activation potential and activation kinetics were unaffected by Tx. In both cases, no tonotopic Tx-dependent activation of channel activity was observed. Therefore, contrary to the hypotheses, electrophysiological assessment suggests that molecular mechanisms other than auxiliary beta-subunits are involved in generating a tonotopic distribution of BK channel kinetics and electric tuning in chick basilar papilla.
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Affiliation(s)
- Mingjie Tong
- Kresge Hearing Research Institute, Univ. of Michigan, 1150 W. Medical Center Drive, Ann Arbor, MI 48109-5616, USA
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32
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Díaz L, Ceja-Ochoa I, Restrepo-Angulo I, Larrea F, Avila-Chávez E, García-Becerra R, Borja-Cacho E, Barrera D, Ahumada E, Gariglio P, Alvarez-Rios E, Ocadiz-Delgado R, Garcia-Villa E, Hernández-Gallegos E, Camacho-Arroyo I, Morales A, Ordaz-Rosado D, García-Latorre E, Escamilla J, Sánchez-Peña LC, Saqui-Salces M, Gamboa-Dominguez A, Vera E, Uribe-Ramírez M, Murbartián J, Ortiz CS, Rivera-Guevara C, De Vizcaya-Ruiz A, Camacho J. Estrogens and human papilloma virus oncogenes regulate human ether-à-go-go-1 potassium channel expression. Cancer Res 2009; 69:3300-7. [PMID: 19351862 DOI: 10.1158/0008-5472.can-08-2036] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Ether-à-go-go-1 (Eag1) potassium channels are potential tools for detection and therapy of numerous cancers. Here, we show human Eag1 (hEag1) regulation by cancer-associated factors. We studied hEag1 gene expression and its regulation by estradiol, antiestrogens, and human papillomavirus (HPV) oncogenes (E6/E7). Primary cultures from normal placentas and cervical cancer tissues; tumor cell lines from cervix, choriocarcinoma, keratinocytes, and lung; and normal cell lines from vascular endothelium, keratinocytes, and lung were used. Reverse transcription-PCR (RT-PCR) experiments and Southern blot analysis showed Eag1 expression in all of the cancer cell types, normal trophoblasts, and vascular endothelium, in contrast to normal keratinocytes and lung cells. Estradiol and antiestrogens regulated Eag1 in a cell type-dependent manner. Real-time RT-PCR experiments in HeLa cells showed that Eag1 estrogenic regulation was strongly associated with the expression of estrogen receptor-alpha. Eag1 protein was detected by monoclonal antibodies in normal placenta and placental blood vessels. Patch-clamp recordings in normal trophoblasts treated with estradiol exhibited potassium currents resembling Eag1 channel activity. Eag1 gene expression in keratinocytes depended either on cellular immortalization or the presence of HPV oncogenes. Eag1 protein was found in keratinocytes transfected with E6/E7 HPV oncogenes. Cell proliferation of E6/E7 keratinocytes was decreased by Eag1 antibodies inhibiting channel activity and by the nonspecific Eag1 inhibitors imipramine and astemizole; the latter also increased apoptosis. Our results propose novel oncogenic mechanisms of estrogen/antiestrogen use and HPV infection. We also suggest Eag1 as an early indicator of cell proliferation leading to malignancies and a therapeutic target at early stages of cellular hyperproliferation.
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Affiliation(s)
- Lorenza Díaz
- Departamento de Biología de la Reproducción, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán
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Hu H, He ML, Tao R, Sun HY, Hu R, Zang WJ, Yuan BX, Lau CP, Tse HF, Li GR. Characterization of ion channels in human preadipocytes. J Cell Physiol 2008; 218:427-35. [PMID: 18942098 DOI: 10.1002/jcp.21617] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Ion channels participate in regulation of cell proliferation. However, though preadipocyte (the progenitor of fat cell) is a type of highly proliferating cells, ion channel expression and their role in proliferation is not understood in human preadipocytes. The present study was designed to characterize ion channels using whole-cell patch clamp technique, RT-PCR, and Western blotting. It was found that a 4-aminopyridine- (4-AP) sensitive transient outward K(+) current (I(to)) was present in a small population of (32.0%) cells, and an outward "noisy" big conductance Ca(2+)-activated K(+) current (I(KCa)) was present in most (92.7%) preadipocytes. The noisy current was inhibited by the big conductance I(KCa) channel blocker paxilline (1 microM), and enhanced by the Ca(2+) ionophore A23187 (5 microM) and the big conductance I(KCa) channel activator NS1619 (10 microM). RT-PCR and Western blot revealed the molecular identities (i.e., KCa1.1 and Kv4.2) of the functional ionic currents I(KCa) and I(to). Blockade of I(KCa) or I(to) with paxilline or 4-AP reduced preadipocyte proliferation, and similar results were obtained with specific siRNAs targeting to KCa1.1 and Kv4.2. Flow cytometric analysis showed ion channel blockade or knockdown of KCa1.1 or Kv4.2 with specific siRNA increased the cell number of G0/G1 phase. The present study demonstrates for the first time that two types of functional ion channel currents, I(to) and big conductance I(KCa), are present in human preadipocytes and that these two types of ion channels participate in regulating proliferation of human preadipocytes.
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Affiliation(s)
- Hao Hu
- Department of Medicine, Research Centre of Heart, Brain, Healthy Aging, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
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CHU SAUTUNG, HUANG CHORNGCHIH, HUANG CHUNJEN, CHENG JINSHIUNG, CHAI KUOLIANG, CHENG HEHSIUNG, FANG YICHIEN, CHI CHAOCHUAN, SU HSINGHAO, CHOU CHIANGTING, JAN CHUNGREN. Tamoxifen-Induced [Ca2+]iRises and Ca2+-Independent Cell Death in Human Oral Cancer Cells. J Recept Signal Transduct Res 2008; 27:353-67. [DOI: 10.1080/10799890701699660] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Soom M, Gessner G, Heuer H, Hoshi T, Heinemann SH. A mutually exclusive alternative exon of slo1 codes for a neuronal BK channel with altered function. Channels (Austin) 2008; 2:278-82. [PMID: 18719396 DOI: 10.4161/chan.2.4.6571] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Large-conductance Ca(2+)- and voltage-activated K(+) (BK) channels are comprised of four pore-forming -subunits (Slo1), whose mRNA is alternatively spliced in a cell-specific manner. Here we report the first case of a correctly spliced mutually exclusive exon in a mammalian (human and mouse) BK channel; an exon coding for the region from S6 to the RCK1 domain is exchanged for an alternative exon of the same length. The slo1 transcript with this novel exon is present in native brain tissues and inclusion of the alternative exon profoundly alters the channel's gating characteristics: faster activation at low Ca(2+) concentrations and greater open probability at resting membrane potential at high Ca(2+) concentrations. The novel gating features conferred by the alternative exon are dominant over those of the commonly described Slo1 variant when coexpressed. The evolutionarily preserved splicing of the Slo1 S6-RCK1 linker segment possess great potential to fine-tune neuronal excitability.
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Affiliation(s)
- Malle Soom
- Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena, Jena, Germany
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36
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Tamoxifen-inducible gene deletion in the cardiac conduction system. J Mol Cell Cardiol 2008; 45:62-9. [DOI: 10.1016/j.yjmcc.2008.04.008] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Revised: 04/18/2008] [Accepted: 04/18/2008] [Indexed: 12/18/2022]
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Foutz RM, Grimm PR, Sansom SC. Insulin increases the activity of mesangial BK channels through MAPK signaling. Am J Physiol Renal Physiol 2008; 294:F1465-72. [PMID: 18367663 DOI: 10.1152/ajprenal.00012.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Glomerular hyperfiltration and mesangial expansion have been described in mouse models of a hyperinsulinemic early stage of type 2 diabetes mellitus (DM). Large-conductance Ca(2+)-activated K(+) channels (BK) have been linked to relaxation of human mesangial cells (MC) and may contribute to MC expansion and hyperfiltration. We hypothesized that high insulin levels increase BK activity in MC by increasing the number and/or open probability (P(o)) of BK in the plasma membrane. With the use of the patch-clamp technique, BK activity was analyzed in cultured MC exposed to normal insulin (1 nM) and high insulin (100 nM) for a 48-h period. The mean P(o) and the percentage of patches (cell attached) with detected BK increased by 100% in the insulin-treated cells. Real-time PCR revealed that insulin increased mRNA of BK-alpha. Western blot revealed an insulin-stimulated increase in BK-alpha from both total cellular and plasma membrane protein fractions. The mitogen-activated protein kinase (MAPK) inhibitors PD-098059 and U-0126 attenuated the insulin-induced increase in BK-alpha expression. PD-098059 inhibited insulin-stimulated phosphorylation of extracellular signal-regulated kinase 1/2 in MC. An insulin-stimulated increase also was found for total cellular BK-beta(1), the accessory subunit of BK in MC. A similar increase in BK-alpha mRNA and protein was evoked by an insulin-like growth factor I analog. Glomeruli, isolated from hyperinsulinemic early stage type 2 DM mice, exhibited increased BK-alpha mRNA by real-time PCR and protein by immunohistochemical staining and Western blot. These results indicate that insulin activates BK in the plasma membrane of MC and stimulates, via MAPK, an increase in cellular and plasma membrane BK-alpha.
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Affiliation(s)
- Ruth M Foutz
- Dept. of Cellular and Integrative Physiology, Univ. of Nebraska Medical Center, 985850 Nebraska Medical Center, Omaha, NE 68198-5850, USA
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Wang J, Xu YQ, Liang YY, Gongora R, Warnock DG, Ma HP. An intermediate-conductance Ca(2+)-activated K (+) channel mediates B lymphoma cell cycle progression induced by serum. Pflugers Arch 2007; 454:945-56. [PMID: 17429684 DOI: 10.1007/s00424-007-0258-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Accepted: 03/18/2007] [Indexed: 01/12/2023]
Abstract
We have previously reported that Kv1.3 channel is expressed in Daudi cells. However, the present study demonstrates that Daudi cell cycle progression is not affected by margatoxin, a Kv1.3 channel blocker, but can be suppressed by tetraethylammonium (TEA) and 1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34), a selective blocker of intermediate-conductance Ca(2+)-activated K(+) (IK) channels. Our patch-clamp data indicate that Daudi cells express an IK channel because it has a unit conductance of about 30 pS, is voltage-independent, and can be activated by submicromolar Ca(2+) and blocked by TRAM-34. Fetal bovine serum (FBS) elevated intracellular Ca(2+) concentration ([Ca(2+)](i)) and activated this IK channel. Conversely, Rituximab, a human-mouse chimeric monoclonal antibody of CD20, significantly decreased [Ca(2+)](i) and inhibited the channel. Furthermore, both FBS-induced IK channel expression and cell cycle progression were attenuated by the treatment with LY-294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor. These data together suggest that a growth factor(s) in FBS triggers cell cycle progression by elevating both IK channel activity via CD20 and IK channel expression on the cell surface via PI3K. Thus, elevated IK channel activity and expression may account, in part, for Daudi cell malignant growth and proliferation.
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Affiliation(s)
- Jing Wang
- Department of Medicine, University of Alabama at Birmingham, 1530 Third Avenue South, Zeigler Research Building 510, Birmingham, AL, 35294-0017, USA
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