1
|
Li R, Tao T, Ren Q, Xie S, Gao X, Wu J, Chen D, Xu C. Key Genes Are Associated with the Prognosis of Glioma, and Melittin Can Regulate the Expression of These Genes in Glioma U87 Cells. BIOMED RESEARCH INTERNATIONAL 2022; 2022:1-18. [DOI: 10.1155/2022/7033478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Glioma is the most common primary tumor of the central nervous system. Currently, there is no effective treatment for glioma. Melittin (MT) is the main component of bee venom, which was found to have therapeutic effects on a variety of tumors. In this study, we explored the relationship between key genes regulated by MT and the prognosis of glioma. In cultured glioma U87 and U251 cells, MT inhibited cell proliferation and induces cell apoptosis in a time- and concentration-dependent manner. RNA-seq revealed that MT upregulated 11 genes and downregulated 37 genes. These genes are mainly enriched in cell membrane signaling pathways, such as surface membrane, membrane-enclosed organelles, integral component of membrane, PPAR signaling pathway, and voltage-gated potassium channel. PPI network analysis and literature analysis of 48 genes were performed, and 8 key genes were identified, and these key genes were closely associated with clinical prognosis. Overexpression of PCDH18, PPL, DEPP1, VASN, KCNE4, MYBPH, and C5AR2 genes or low expression of MARCH4 gene in glioma patients was associated with poor survival. qPCR confirmed that MT can regulate the expression of these genes in glioma U87 cells. This study indicated that MT significantly inhibited the growth and regulated the expression of PCDH18, C5AR2, VASN, DEPP1, MYBPH, KCNE4, PPL, and MARCH4 genes in glioma U87 cells in vitro. These genes are closely related to the prognosis of patients with glioma and can be used as independent prognostic factors in patients with glioma. MT is a potential drug for the treatment of glioma.
Collapse
Affiliation(s)
- Ran Li
- Guangdong Provincial Key Laboratory of Utilization and Conservation of Food and Medicinal Resources in Northern Region, Shaoguan University, 288 Daxue Road, Shaoguan, 512005 Guangdong Province, China
- Medical College of Shaoguan University, 108 XinHua Nan Road, Shaoguan, 512005 Guangdong Province, China
- Hunan Yueyang Maternal & Child Health-Care Hospital, 693 Baling Middle Road, Yueyang, 414000 Hunan Province, China
| | - Ting Tao
- Hunan Yueyang Maternal & Child Health-Care Hospital, 693 Baling Middle Road, Yueyang, 414000 Hunan Province, China
| | - Qiuyun Ren
- Brain Function and Disease Laboratory, Shantou University Medical College, 22 Xinling Road, Shantou, 515041 Guangdong Province, China
| | - Sujun Xie
- Guangzhou University of Chinese Medicine, 12 Jichang Road, Baiyun District, Guangzhou, 510405 Guangdong Province, China
| | - Xiaofen Gao
- Medical College of Shaoguan University, 108 XinHua Nan Road, Shaoguan, 512005 Guangdong Province, China
| | - Jie Wu
- Brain Function and Disease Laboratory, Shantou University Medical College, 22 Xinling Road, Shantou, 515041 Guangdong Province, China
| | - Diling Chen
- Guangzhou Laboratory, 9 XingDao HuanBei Road, Guangzhou International Bio Island, Guangzhou, 510005 Guangdong Province, China
| | - Changqiong Xu
- Medical College of Shaoguan University, 108 XinHua Nan Road, Shaoguan, 512005 Guangdong Province, China
- Hunan Yueyang Maternal & Child Health-Care Hospital, 693 Baling Middle Road, Yueyang, 414000 Hunan Province, China
| |
Collapse
|
2
|
A Possible Explanation for the Low Penetrance of Pathogenic KCNE1 Variants in Long QT Syndrome Type 5. Pharmaceuticals (Basel) 2022; 15:ph15121550. [PMID: 36559002 PMCID: PMC9782992 DOI: 10.3390/ph15121550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 12/07/2022] [Accepted: 12/09/2022] [Indexed: 12/15/2022] Open
Abstract
Long QT syndrome (LQTS) is an inherited cardiac rhythm disorder associated with increased incidence of cardiac arrhythmias and sudden death. LQTS type 5 (LQT5) is caused by dominant mutant variants of KCNE1, a regulatory subunit of the voltage-gated ion channels generating the cardiac potassium current IKs. While mutant LQT5 KCNE1 variants are known to inhibit IKs amplitudes in heterologous expression systems, cardiomyocytes from a transgenic rabbit LQT5 model displayed unchanged IKs amplitudes, pointing towards the critical role of additional factors in the development of the LQT5 phenotype in vivo. In this study, we demonstrate that KCNE3, a candidate regulatory subunit of IKs channels minimizes the inhibitory effects of LQT5 KCNE1 variants on IKs amplitudes, while current deactivation is accelerated. Such changes recapitulate IKs properties observed in LQT5 transgenic rabbits. We show that KCNE3 accomplishes this by displacing the KCNE1 subunit within the IKs ion channel complex, as evidenced by a dedicated biophysical assay. These findings depict KCNE3 as an integral part of the IKs channel complex that regulates IKs function in cardiomyocytes and modifies the development of the LQT5 phenotype.
Collapse
|
3
|
Abbott GW. Kv Channel Ancillary Subunits: Where Do We Go from Here? Physiology (Bethesda) 2022; 37:0. [PMID: 35797055 PMCID: PMC9394777 DOI: 10.1152/physiol.00005.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 04/29/2022] [Accepted: 04/29/2022] [Indexed: 01/10/2023] Open
Abstract
Voltage-gated potassium (Kv) channels each comprise four pore-forming α-subunits that orchestrate essential duties such as voltage sensing and K+ selectivity and conductance. In vivo, however, Kv channels also incorporate regulatory subunits-some Kv channel specific, others more general modifiers of protein folding, trafficking, and function. Understanding all the above is essential for a complete picture of the role of Kv channels in physiology and disease.
Collapse
Affiliation(s)
- Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, California
| |
Collapse
|
4
|
Control of Biophysical and Pharmacological Properties of Potassium Channels by Ancillary Subunits. Handb Exp Pharmacol 2021; 267:445-480. [PMID: 34247280 DOI: 10.1007/164_2021_512] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Potassium channels facilitate and regulate physiological processes as diverse as electrical signaling, ion, solute and hormone secretion, fluid homeostasis, hearing, pain sensation, muscular contraction, and the heartbeat. Potassium channels are each formed by either a tetramer or dimer of pore-forming α subunits that co-assemble to create a multimer with a K+-selective pore that in most cases is capable of functioning as a discrete unit to pass K+ ions across the cell membrane. The reality in vivo, however, is that the potassium channel α subunit multimers co-assemble with ancillary subunits to serve specific physiological functions. The ancillary subunits impart specific physiological properties that are often required for a particular activity in vivo; in addition, ancillary subunit interaction often alters the pharmacology of the resultant complex. In this chapter the modes of action of ancillary subunits on K+ channel physiology and pharmacology are described and categorized into various mechanistic classes.
Collapse
|
5
|
Kuenze G, Vanoye CG, Desai RR, Adusumilli S, Brewer KR, Woods H, McDonald EF, Sanders CR, George AL, Meiler J. Allosteric mechanism for KCNE1 modulation of KCNQ1 potassium channel activation. eLife 2020; 9:57680. [PMID: 33095155 PMCID: PMC7584456 DOI: 10.7554/elife.57680] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 09/28/2020] [Indexed: 01/04/2023] Open
Abstract
The function of the voltage-gated KCNQ1 potassium channel is regulated by co-assembly with KCNE auxiliary subunits. KCNQ1-KCNE1 channels generate the slow delayed rectifier current, IKs, which contributes to the repolarization phase of the cardiac action potential. A three amino acid motif (F57-T58-L59, FTL) in KCNE1 is essential for slow activation of KCNQ1-KCNE1 channels. However, how this motif interacts with KCNQ1 to control its function is unknown. Combining computational modeling with electrophysiological studies, we developed structural models of the KCNQ1-KCNE1 complex that suggest how KCNE1 controls KCNQ1 activation. The FTL motif binds at a cleft between the voltage-sensing and pore domains and appears to affect the channel gate by an allosteric mechanism. Comparison with the KCNQ1-KCNE3 channel structure suggests a common transmembrane-binding mode for different KCNEs and illuminates how specific differences in the interaction of their triplet motifs determine the profound differences in KCNQ1 functional modulation by KCNE1 versus KCNE3.
Collapse
Affiliation(s)
- Georg Kuenze
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Chemistry, Vanderbilt University, Nashville, United States.,Institute for Drug Discovery, Leipzig University, Leipzig, Germany
| | - Carlos G Vanoye
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, United States
| | - Reshma R Desai
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, United States
| | - Sneha Adusumilli
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, United States
| | - Kathryn R Brewer
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Biochemistry, Vanderbilt University, Nashville, United States
| | - Hope Woods
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Chemistry, Vanderbilt University, Nashville, United States
| | - Eli F McDonald
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Chemistry, Vanderbilt University, Nashville, United States
| | - Charles R Sanders
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Biochemistry, Vanderbilt University, Nashville, United States
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, United States
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Chemistry, Vanderbilt University, Nashville, United States.,Institute for Drug Discovery, Leipzig University, Leipzig, Germany.,Department of Pharmacology, Vanderbilt University, Nashville, United States
| |
Collapse
|
6
|
Solé L, Sastre D, Colomer-Molera M, Vallejo-Gracia A, Roig SR, Pérez-Verdaguer M, Lillo P, Tamkun MM, Felipe A. Functional Consequences of the Variable Stoichiometry of the Kv1.3-KCNE4 Complex. Cells 2020; 9:cells9051128. [PMID: 32370164 PMCID: PMC7290415 DOI: 10.3390/cells9051128] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 04/25/2020] [Accepted: 04/30/2020] [Indexed: 12/16/2022] Open
Abstract
The voltage-gated potassium channel Kv1.3 plays a crucial role during the immune response. The channel forms oligomeric complexes by associating with several modulatory subunits. KCNE4, one of the five members of the KCNE family, binds to Kv1.3, altering channel activity and membrane expression. The association of KCNEs with Kv channels is the subject of numerous studies, and the stoichiometry of such associations has led to an ongoing debate. The number of KCNE4 subunits that can interact and modulate Kv1.3 is unknown. KCNE4 transfers important elements to the Kv1.3 channelosome that negatively regulate channel function, thereby fine-tuning leukocyte physiology. The aim of this study was to determine the stoichiometry of the functional Kv1.3-KCNE4 complex. We demonstrate that as many as four KCNE4 subunits can bind to the same Kv1.3 channel, indicating a variable Kv1.3-KCNE4 stoichiometry. While increasing the number of KCNE4 subunits steadily slowed the activation of the channel and decreased the abundance of Kv1.3 at the cell surface, the presence of a single KCNE4 peptide was sufficient for the cooperative enhancement of the inactivating function of the channel. This variable architecture, which depends on KCNE4 availability, differentially affects Kv1.3 function. Therefore, our data indicate that the physiological remodeling of KCNE4 triggers functional consequences for Kv1.3, thus affecting cell physiology.
Collapse
Affiliation(s)
- Laura Solé
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (L.S.); (D.S.); (M.C.-M.); (A.V.-G.); (S.R.R.); (M.P.-V.)
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA;
| | - Daniel Sastre
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (L.S.); (D.S.); (M.C.-M.); (A.V.-G.); (S.R.R.); (M.P.-V.)
| | - Magalí Colomer-Molera
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (L.S.); (D.S.); (M.C.-M.); (A.V.-G.); (S.R.R.); (M.P.-V.)
| | - Albert Vallejo-Gracia
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (L.S.); (D.S.); (M.C.-M.); (A.V.-G.); (S.R.R.); (M.P.-V.)
- Virology and Immunology, Gladstone Institutes, University of California San Francisco, San Francisco, CA 94158, USA
| | - Sara R. Roig
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (L.S.); (D.S.); (M.C.-M.); (A.V.-G.); (S.R.R.); (M.P.-V.)
- Imaging Core Facility, Biozentrum, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland
| | - Mireia Pérez-Verdaguer
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (L.S.); (D.S.); (M.C.-M.); (A.V.-G.); (S.R.R.); (M.P.-V.)
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Pilar Lillo
- Instituto de Química Física Rocasolano, CSIC, 28006 Madrid, Spain;
| | - Michael M. Tamkun
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA;
| | - Antonio Felipe
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (L.S.); (D.S.); (M.C.-M.); (A.V.-G.); (S.R.R.); (M.P.-V.)
- Correspondence: ; Tel.: +34-934034616; Fax: +34-934021559
| |
Collapse
|
7
|
Oliveras A, Serrano-Novillo C, Moreno C, de la Cruz A, Valenzuela C, Soeller C, Comes N, Felipe A. The unconventional biogenesis of Kv7.1-KCNE1 complexes. SCIENCE ADVANCES 2020; 6:eaay4472. [PMID: 32270035 PMCID: PMC7112945 DOI: 10.1126/sciadv.aay4472] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 01/09/2020] [Indexed: 06/11/2023]
Abstract
The potassium channel Kv7.1 associates with the KCNE1 regulatory subunit to trigger cardiac I Ks currents. Although the Kv7.1/KCNE1 complex has received much attention, the subcellular compartment hosting the assembly is the subject of ongoing debate. Evidence suggests that the complex forms either earlier in the endoplasmic reticulum or directly at the plasma membrane. Kv7.1 and KCNE1 mutations, responsible for long QT syndromes, impair association and traffic, thereby altering I Ks currents. We found that Kv7.1 and KCNE1 do not assemble in the first stages of their biogenesis. Data support an unconventional secretory pathway for Kv7.1-KCNE1 that bypasses Golgi. This route targets channels to endoplasmic reticulum-plasma membrane junctions, where Kv7.1-KCNE1 assemble. This mechanism helps to resolve the ongoing controversy about the subcellular compartment hosting the association. Our results also provide new insights into I Ks channel localization at endoplasmic reticulum-plasma membrane junctions, highlighting an alternative anterograde trafficking mechanism for oligomeric ion channels.
Collapse
Affiliation(s)
- Anna Oliveras
- Molecular Physiology Laboratory, Departamento de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
| | - Clara Serrano-Novillo
- Molecular Physiology Laboratory, Departamento de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
| | - Cristina Moreno
- National Institute of Neurological Disorders and Stroke (NIH), Bethesda, MD, USA
| | - Alicia de la Cruz
- Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Carmen Valenzuela
- Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
- Spanish Network for Biomedical Research in Cardiovascular Research (CIBERCV), Instituto de Salud Carlos III, Madrid, Spain
| | - Christian Soeller
- Living Systems Institute and Biomedical Physics, University of Exeter, Exeter, UK
| | - Núria Comes
- Departamento De Biomedicina, Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Barcelona, Spain
| | - Antonio Felipe
- Molecular Physiology Laboratory, Departamento de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
| |
Collapse
|
8
|
Sun J, MacKinnon R. Structural Basis of Human KCNQ1 Modulation and Gating. Cell 2019; 180:340-347.e9. [PMID: 31883792 DOI: 10.1016/j.cell.2019.12.003] [Citation(s) in RCA: 161] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 10/25/2019] [Accepted: 12/04/2019] [Indexed: 01/04/2023]
Abstract
KCNQ1, also known as Kv7.1, is a voltage-dependent K+ channel that regulates gastric acid secretion, salt and glucose homeostasis, and heart rhythm. Its functional properties are regulated in a tissue-specific manner through co-assembly with beta subunits KCNE1-5. In non-excitable cells, KCNQ1 forms a complex with KCNE3, which suppresses channel closure at negative membrane voltages that otherwise would close it. Pore opening is regulated by the signaling lipid PIP2. Using cryoelectron microscopy (cryo-EM), we show that KCNE3 tucks its single-membrane-spanning helix against KCNQ1, at a location that appears to lock the voltage sensor in its depolarized conformation. Without PIP2, the pore remains closed. Upon addition, PIP2 occupies a site on KCNQ1 within the inner membrane leaflet, which triggers a large conformational change that leads to dilation of the pore's gate. It is likely that this mechanism of PIP2 activation is conserved among Kv7 channels.
Collapse
Affiliation(s)
- Ji Sun
- Laboratory of Molecular Neurobiology and Biophysics and Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics and Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
| |
Collapse
|
9
|
Wang Y, Eldstrom J, Fedida D. The I Ks Ion Channel Activator Mefenamic Acid Requires KCNE1 and Modulates Channel Gating in a Subunit-Dependent Manner. Mol Pharmacol 2019; 97:132-144. [PMID: 31722973 DOI: 10.1124/mol.119.117952] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 11/04/2019] [Indexed: 01/05/2023] Open
Abstract
The pairing of KCNQ1 and KCNE1 subunits together mediates the cardiac slow delayed rectifier current (I Ks ), which is partly responsible for cardiomyocyte repolarization and physiologic shortening of the cardiac action potential. Mefenamic acid, a nonsteroidal anti-inflammatory drug, has been identified as an I Ks activator. Here, we provide a biophysical and pharmacological characterization of mefenamic acid's effect on I Ks Using whole-cell patch clamp, we show that mefenamic acid enhances I Ks activity in both a dose- and stoichiometry-dependent fashion by changing the slowly activating and deactivating I Ks current into an almost linear current with instantaneous onset and slowed tail current decay, sensitive to the I Ks blocker (3R,4S)-(+)-N-[3-hydroxy-2,2-dimethyl-6-(4,4,4-trifluorobutoxy) chroman-4-yl]-N-methylmethanesulfonamide (HMR1556). Both single channels, which reveal no change in the maximum conductance, and whole-cell studies, which reveal a dramatically altered conductance-voltage relationship despite increasingly longer interpulse intervals, suggest mefenamic acid decreases the voltage sensitivity of the I Ks channel and shifts channel gating kinetics toward more negative potentials. Modeling studies revealed that changes in voltage sensor activation kinetics are sufficient to reproduce the dose and frequency dependence of mefenamic acid action on I Ks channels. Mutational analysis showed that mefenamic acid's effect on I Ks required residue K41 and potentially other surrounding residues on the extracellular surface of KCNE1, and explains why the KCNQ1 channel alone is insensitive to up to 1 mM mefenamic acid. Given that mefenamic acid can enhance all I Ks channel complexes containing different ratios of KCNQ1 to KCNE1, it may provide a promising therapeutic approach to treating life-threatening cardiac arrhythmia syndromes. SIGNIFICANCE STATEMENT: The channels which generate the cardiac slow delayed rectifier K+ current (I Ks ) are composed of KCNQ1 and KCNE1 subunits. Due to the critical role played by I Ks in heartbeat regulation, enhancing I Ks current has been identified as a promising therapeutic strategy to treat various heart rhythm diseases. Most I Ks activators, unfortunately, only work on KCNQ1 alone and not the physiologically relevant I Ks channel. We have demonstrated that mefenamic acid can enhance I Ks in a dose- and stoichiometry-dependent fashion, regulated by its interactions with KCNE1.
Collapse
Affiliation(s)
- Yundi Wang
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| |
Collapse
|
10
|
Hu Z, Jepps TA, Zhou L, Liu J, Li M, Abbott GW. Kcne4 deletion sex dependently inhibits the RISK pathway response and exacerbates hepatic ischemia-reperfusion injury in mice. Am J Physiol Regul Integr Comp Physiol 2019; 316:R552-R562. [PMID: 30758982 DOI: 10.1152/ajpregu.00251.2018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Activation of antiapoptotic signaling cascades, such as the reperfusion injury salvage kinase (RISK) and survivor activating factor enhancement (SAFE) pathways, is protective in a variety of tissues in the context of ischemia-reperfusion (IR) injury. Hepatic IR injury causes clinically significant hepatocellular damage in surgical procedures, including liver transplantation and hepatic resection, increasing associated morbidity and mortality. We previously found that the cardiovascular-expressed K+ voltage-gated channel ancillary subunit KCNE4 sex specifically influences the cardiac RISK/SAFE pathway response to IR and that Kcne4 deletion testosterone dependently exacerbates cardiac IR injury. Here, we discovered that germline Kcne4 deletion exacerbates hepatic IR injury damage in 13-mo-old male mice, despite a lack of Kcne4 expression in male mouse liver. Examining RISK/SAFE pathway induction, we found that Kcne4 deletion prevents the hepatic ERK1/2 phosphorylation response to IR injury. Conversely, in 13-mo-old female mice, Kcne4 deletion increased both baseline and post-IR GSK-3β inhibitory phosphorylation, and pharmacological GSK-3β inhibition was hepatoprotective. Finally, castration of male mice restored normal hepatic RISK/SAFE pathway responses in Kcne4-/- mice, eliminated Kcne4 deletion-dependent serum alanine aminotransferase elevation, and genotype independently augmented the hepatic post-IR GSK-3β phosphorylation response. These findings support a role for KCNE4 as a systemic modulator of IR injury response and uncover hormonally influenced, sex-specific, KCNE4-dependent and -independent RISK/SAFE pathway induction.
Collapse
Affiliation(s)
- Zhaoyang Hu
- Laboratory of Anesthesiology and Critical Care Medicine, Translational Neuroscience Center, West China Hospital, Sichuan University , Chengdu, Sichuan , China
| | - Thomas A Jepps
- Department of Biomedical Sciences, University of Copenhagen , Copenhagen , Denmark
| | - Leng Zhou
- Department of Anesthesiology, West China Hospital, Sichuan University , Chengdu, Sichuan , China
| | - Jin Liu
- Department of Anesthesiology, West China Hospital, Sichuan University , Chengdu, Sichuan , China
| | - Mufeng Li
- Laboratory of Anesthesiology and Critical Care Medicine, Translational Neuroscience Center, West China Hospital, Sichuan University , Chengdu, Sichuan , China
| | - Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California , Irvine, California
| |
Collapse
|
11
|
Hilton JK, Salehpour T, Sisco NJ, Rath P, Van Horn WD. Phosphoinositide-interacting regulator of TRP (PIRT) has opposing effects on human and mouse TRPM8 ion channels. J Biol Chem 2018; 293:9423-9434. [PMID: 29724821 DOI: 10.1074/jbc.ra118.003563] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 04/25/2018] [Indexed: 12/24/2022] Open
Abstract
Transient receptor potential melastatin 8 (TRPM8) is a cold-sensitive ion channel with diverse physiological roles. TRPM8 activity is modulated by many mechanisms, including an interaction with the small membrane protein phosphoinositide-interacting regulator of TRP (PIRT). Here, using comparative electrophysiology experiments, we identified species-dependent differences between the human and mouse TRPM8-PIRT complexes. We found that human PIRT attenuated human TPRM8 conductance, unlike mouse PIRT, which enhanced mouse TRPM8 conductance. Quantitative Western blot analysis demonstrates that this effect does not arise from decreased trafficking of TRPM8 to the plasma membrane. Chimeric human/mouse TRPM8 channels were generated to probe the molecular basis of the PIRT modulation, and the effect was recapitulated in a pore domain chimera, demonstrating the importance of this region for PIRT-mediated regulation of TRPM8. Moreover, recombinantly expressed and purified human TRPM8 S1-S4 domain (comprising transmembrane helices S1-S4, also known as the sensing domain, ligand-sensing domain, or voltage sensing-like domain) and full-length human PIRT were used to investigate binding between the proteins. NMR experiments, supported by a pulldown assay, indicated that PIRT binds directly and specifically to the TRPM8 S1-S4 domain. Binding became saturated as the S1-S4:PIRT mole ratio approached 1. Our results have uncovered species-specific TRPM8 modulation by PIRT. They provide evidence for a direct interaction between PIRT and the TRPM8 S1-S4 domain with a 1:1 binding stoichiometry, suggesting that a functional tetrameric TRPM8 channel has four PIRT-binding sites.
Collapse
Affiliation(s)
- Jacob K Hilton
- From the School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287.,the Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University, Tempe, Arizona 85281, and.,The Magnetic Resonance Research Center, Arizona State University, Tempe, Arizona 85287
| | - Taraneh Salehpour
- From the School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287.,the Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University, Tempe, Arizona 85281, and.,The Magnetic Resonance Research Center, Arizona State University, Tempe, Arizona 85287
| | - Nicholas J Sisco
- From the School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287.,the Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University, Tempe, Arizona 85281, and.,The Magnetic Resonance Research Center, Arizona State University, Tempe, Arizona 85287
| | - Parthasarathi Rath
- From the School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287.,the Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University, Tempe, Arizona 85281, and.,The Magnetic Resonance Research Center, Arizona State University, Tempe, Arizona 85287
| | - Wade D Van Horn
- From the School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, .,the Virginia G. Piper Center for Personalized Diagnostics, Biodesign Institute, Arizona State University, Tempe, Arizona 85281, and.,The Magnetic Resonance Research Center, Arizona State University, Tempe, Arizona 85287
| |
Collapse
|
12
|
McKinnon D, Rosati B. Transmural gradients in ion channel and auxiliary subunit expression. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 122:165-186. [PMID: 27702655 DOI: 10.1016/j.pbiomolbio.2016.09.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 09/30/2016] [Indexed: 12/11/2022]
Abstract
Evolution has acted to shape the action potential in different regions of the heart in order to produce a maximally stable and efficient pump. This has been achieved by creating regional differences in ion channel expression levels within the heart as well as differences between equivalent cardiac tissues in different species. These region- and species-dependent differences in channel expression are established by regulatory evolution, evolution of the regulatory mechanisms that control channel expression levels. Ion channel auxiliary subunits are obvious targets for regulatory evolution, in order to change channel expression levels and/or modify channel function. This review focuses on the transmural gradients of ion channel expression in the heart and the role that regulation of auxiliary subunit expression plays in generating and shaping these gradients.
Collapse
Affiliation(s)
- David McKinnon
- Department of Veterans Affairs Medical Center, Northport, NY, USA; Institute of Molecular Cardiology, Stony Brook University, Stony Brook, NY, USA; Department of Neurobiology and Behavior, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Barbara Rosati
- Department of Veterans Affairs Medical Center, Northport, NY, USA; Institute of Molecular Cardiology, Stony Brook University, Stony Brook, NY, USA; Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, 11794, USA.
| |
Collapse
|
13
|
Biasiotta A, D'Arcangelo D, Passarelli F, Nicodemi EM, Facchiano A. Ion channels expression and function are strongly modified in solid tumors and vascular malformations. J Transl Med 2016; 14:285. [PMID: 27716384 PMCID: PMC5050926 DOI: 10.1186/s12967-016-1038-y] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 09/21/2016] [Indexed: 12/21/2022] Open
Abstract
Background Several cellular functions relate to ion-channels activity. Physiologically relevant chains of events leading to angiogenesis, cell cycle and different forms of cell death, require transmembrane voltage control. We hypothesized that the unordered angiogenesis occurring in solid cancers and vascular malformations might associate, at least in part, to ion-transport alteration. Methods The expression level of several ion-channels was analyzed in human solid tumor biopsies. Expression of 90 genes coding for ion-channels related proteins was investigated within the Oncomine database, in 25 independent patients-datasets referring to five histologically-different solid tumors (namely, bladder cancer, glioblastoma, melanoma, breast invasive-ductal cancer, lung carcinoma), in a total of 3673 patients (674 control-samples and 2999 cancer-samples). Furthermore, the ion-channel activity was directly assessed by measuring in vivo the electrical sympathetic skin responses (SSR) on the skin of 14 patients affected by the flat port-wine stains vascular malformation, i.e., a non-tumor vascular malformation clinical model. Results Several ion-channels showed significantly increased expression in tumors (p < 0.0005); nine genes (namely, CACNA1D, FXYD3, FXYD5, HTR3A, KCNE3, KCNE4, KCNN4, CLIC1, TRPM3) showed such significant modification in at least half of datasets investigated for each cancer type. Moreover, in vivo analyses in flat port-wine stains patients showed a significantly reduced SSR in the affected skin as compared to the contralateral healthy skin (p < 0.05), in both latency and amplitude measurements. Conclusions All together these data identify ion-channel genes showing significantly modified expression in different tumors and cancer-vessels, and indicate a relevant electrophysiological alteration in human vascular malformations. Such data suggest a possible role and a potential diagnostic application of the ion–electron transport in vascular disorders underlying tumor neo-angiogenesis and vascular malformations.
Collapse
Affiliation(s)
| | - Daniela D'Arcangelo
- Istituto Dermopatico dell'Immacolata, IDI-IRCCS, Fondazione Luigi Maria Monti, via Monti di Creta 104, 00167, Rome, Italy
| | - Francesca Passarelli
- Istituto Dermopatico dell'Immacolata, IDI-IRCCS, Fondazione Luigi Maria Monti, via Monti di Creta 104, 00167, Rome, Italy
| | - Ezio Maria Nicodemi
- Istituto Dermopatico dell'Immacolata, IDI-IRCCS, Fondazione Luigi Maria Monti, via Monti di Creta 104, 00167, Rome, Italy.
| | - Antonio Facchiano
- Istituto Dermopatico dell'Immacolata, IDI-IRCCS, Fondazione Luigi Maria Monti, via Monti di Creta 104, 00167, Rome, Italy.
| |
Collapse
|
14
|
Kroncke BM, Van Horn WD, Smith J, Kang C, Welch RC, Song Y, Nannemann DP, Taylor KC, Sisco NJ, George AL, Meiler J, Vanoye CG, Sanders CR. Structural basis for KCNE3 modulation of potassium recycling in epithelia. SCIENCE ADVANCES 2016; 2:e1501228. [PMID: 27626070 PMCID: PMC5017827 DOI: 10.1126/sciadv.1501228] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 08/10/2016] [Indexed: 05/25/2023]
Abstract
The single-span membrane protein KCNE3 modulates a variety of voltage-gated ion channels in diverse biological contexts. In epithelial cells, KCNE3 regulates the function of the KCNQ1 potassium ion (K(+)) channel to enable K(+) recycling coupled to transepithelial chloride ion (Cl(-)) secretion, a physiologically critical cellular transport process in various organs and whose malfunction causes diseases, such as cystic fibrosis (CF), cholera, and pulmonary edema. Structural, computational, biochemical, and electrophysiological studies lead to an atomically explicit integrative structural model of the KCNE3-KCNQ1 complex that explains how KCNE3 induces the constitutive activation of KCNQ1 channel activity, a crucial component in K(+) recycling. Central to this mechanism are direct interactions of KCNE3 residues at both ends of its transmembrane domain with residues on the intra- and extracellular ends of the KCNQ1 voltage-sensing domain S4 helix. These interactions appear to stabilize the activated "up" state configuration of S4, a prerequisite for full opening of the KCNQ1 channel gate. In addition, the integrative structural model was used to guide electrophysiological studies that illuminate the molecular basis for how estrogen exacerbates CF lung disease in female patients, a phenomenon known as the "CF gender gap."
Collapse
Affiliation(s)
- Brett M. Kroncke
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Wade D. Van Horn
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA
- Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
- Center for Personalized Diagnostics, Arizona State University, Tempe, AZ 85287, USA
| | - Jarrod Smith
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - CongBao Kang
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
- Experimental Therapeutics Centre, Agency for Science Technology and Research, Singapore, Singapore
| | - Richard C. Welch
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| | - Yuanli Song
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - David P. Nannemann
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
- Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
| | - Keenan C. Taylor
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Nicholas J. Sisco
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA
- Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
- Center for Personalized Diagnostics, Arizona State University, Tempe, AZ 85287, USA
| | - Alfred L. George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
- Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
| | - Carlos G. Vanoye
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Charles R. Sanders
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| |
Collapse
|
15
|
Abbott GW. KCNE4 and KCNE5: K(+) channel regulation and cardiac arrhythmogenesis. Gene 2016; 593:249-60. [PMID: 27484720 DOI: 10.1016/j.gene.2016.07.069] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2016] [Revised: 07/23/2016] [Accepted: 07/28/2016] [Indexed: 12/14/2022]
Abstract
KCNE proteins are single transmembrane-segment voltage-gated potassium (Kv) channel ancillary subunits that exhibit a diverse range of physiological functions. Human KCNE gene mutations are associated with various pathophysiological states, most notably cardiac arrhythmias. Of the five isoforms in the human KCNE gene family, KCNE4 and the X-linked KCNE5 are, to date, the least-studied. Recently, however, interest in these neglected genes has been stoked by their putative association with debilitating or lethal cardiac arrhythmias. The sometimes-overlapping functional effects of KCNE4 and KCNE5 vary depending on both their Kv α subunit partner and on other ancillary subunits within the channel complex, but mostly fall into two contrasting categories - either inhibition, or fine-tuning of gating kinetics. This review covers current knowledge regarding the molecular mechanisms of KCNE4 and KCNE5 function, human disease associations, and findings from very recent studies of cardiovascular pathophysiology in Kcne4(-/-) mice.
Collapse
Affiliation(s)
- Geoffrey W Abbott
- Bioelectricity Laboratory, Dept. of Pharmacology and Dept. of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, USA.
| |
Collapse
|
16
|
Murray CI, Westhoff M, Eldstrom J, Thompson E, Emes R, Fedida D. Unnatural amino acid photo-crosslinking of the IKs channel complex demonstrates a KCNE1:KCNQ1 stoichiometry of up to 4:4. eLife 2016; 5. [PMID: 26802629 PMCID: PMC4807126 DOI: 10.7554/elife.11815] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 01/22/2016] [Indexed: 12/20/2022] Open
Abstract
Cardiac repolarization is determined in part by the slow delayed rectifier current (IKs), through the tetrameric voltage-gated ion channel, KCNQ1, and its β-subunit, KCNE1. The stoichiometry between α and β-subunits has been controversial with studies reporting either a strict 2 KCNE1:4 KCNQ1 or a variable ratio up to 4:4. We used IKs fusion proteins linking KCNE1 to one (EQ), two (EQQ) or four (EQQQQ) KCNQ1 subunits, to reproduce compulsory 4:4, 2:4 or 1:4 stoichiometries. Whole cell and single-channel recordings showed EQQ and EQQQQ to have increasingly hyperpolarized activation, reduced conductance, and shorter first latency of opening compared to EQ - all abolished by the addition of KCNE1. As well, using a UV-crosslinking unnatural amino acid in KCNE1, we found EQQQQ and EQQ crosslinking rates to be progressively slowed compared to KCNQ1, which demonstrates that no intrinsic mechanism limits the association of up to four β-subunits within the IKs complex. DOI:http://dx.doi.org/10.7554/eLife.11815.001 The membrane that surrounds heart muscle cells contains specialized channels that can open and close to control the movements of charged ions into and out of the cell. This ion flow generates the electrical signals that stimulate the heart muscle to contract for each heart beat. Different ion channels influence different steps in the initiation and termination of each electrical signal. For example, the IKs ion channel complex helps to return the cell to a resting state so the heart muscle can relax. This allows chambers of the heart to fill with blood before the next beat pumps blood throughout the body. Mutations that affect IKs cause serious heart conditions that affect heart rhythm, such as Long QT Syndrome. The IKs complex consists of channels that are each made of four copies of a protein called KCNQ1, through which potassium ions exit the cell. This channel opens in response to changes in the voltage across the cell membrane (known as the “membrane potential”). A small protein subunit called KCNE1 also makes up part of the complex, but it was not clear how many KCNE1 molecules combine with KCNQ1 to form a working channel complex. Several previous studies have reported two different results: that the KCNQ1 channel complex only exists with two KCNE1 molecules, or that the association is flexible, allowing the complex to contain up to four KCNE1 subunits. Murray et al. have now constructed IKs fusion channels out of different numbers of KCNQ1 and KCNE1 molecules to investigate how different KCNQ1:KCNE1 ratios affect how the channel works. Measuring the responses of these modified channels in mammalian cells revealed that channels with four KCNE1 subunits conducted ions better than channels with one or two KCNE1s. The channels containing fewer KCNE1s also opened at lower membrane potentials and after a shorter delay following a change in the membrane potential. Further experiments also supported the theory that up to four independent KCNE1 subunits may be easily added to the IKs ion channel complex. Murray et al. suggest that by being able to form channel complexes containing different numbers of KCNE1 subunits, cells can more flexibly control the rate at which ions flow out of the heart cells to tune the electrical signals that trigger each heart beat. The next challenges will be to determine the composition of the IKs channel complex in adult heart cells and to investigate how the complex might change with disease. DOI:http://dx.doi.org/10.7554/eLife.11815.002
Collapse
Affiliation(s)
- Christopher I Murray
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Maartje Westhoff
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Emely Thompson
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Robert Emes
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| |
Collapse
|
17
|
Jepps TA, Carr G, Lundegaard PR, Olesen SP, Greenwood IA. Fundamental role for the KCNE4 ancillary subunit in Kv7.4 regulation of arterial tone. J Physiol 2015; 593:5325-40. [PMID: 26503181 DOI: 10.1113/jp271286] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 10/15/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS KCNE4 alters the biophysical properties and cellular localization of voltage-gated potassium channel Kv7.4. KCNE4 is expressed in a variety of arteries and, in mesenteric arteries, co-localizes with Kv7.4, which is important in the control of vascular contractility. Knockdown of KCNE4 leads to reduced Kv7.4 membrane abundance, a depolarized membrane potential and an augmented response to vasoconstrictors. KCNE4 is a key regulator of the function and expression of Kv7.4 in vascular smooth muscle. ABSTRACT The KCNE ancillary subunits (KCNE1-5) significantly alter the expression and function of voltage-gated potassium channels; however, their role in the vasculature has yet to be determined. The present study aimed to investigate the expression and function of the KCNE4 subunit in rat mesenteric arteries and to determine whether it has a functional impact on the regulation of arterial tone by Kv7 channels. In HEK cells expressing Kv7.4, co-expression of KCNE4 increased the membrane expression of Kv7.4 and significantly altered Kv7.4 current properties. Quantitative PCR analysis of different rat arteries found that the KCNE4 isoform predominated and proximity ligation experiments showed that KCNE4 co-localized with Kv7.4 in mesenteric artery myocytes. Morpholino-induced knockdown of KCNE4 depolarized mesenteric artery smooth muscle cells and resulted in their increased sensitivity to methoxamine being attenuated (mean ± SEM EC50 decreased from 5.7 ± 0.63 μm to 1.6 ± 0.23 μm), which coincided with impaired effects of Kv7 modulators. When KCNE4 expression was reduced, less Kv7.4 expression was found in the membrane of the mesenteric artery myocytes. These data show that KCNE4 is consistently expressed in a variety of arteries, and knockdown of the expression product leads to reduced Kv7.4 membrane abundance, a depolarized membrane potential and an augmented response to vasoconstrictors. The present study is the first to demonstrate an integral role of KCNE4 in regulating the function and expression of Kv7.4 in vascular smooth muscle.
Collapse
Affiliation(s)
- Thomas A Jepps
- Ion Channels Group, Department of Biomedical Sciences, University of Copenhagen, Denmark
| | - Georgina Carr
- Vascular Biology Research Centre, Institute for Cardiovascular and Cell Sciences, St George's University of London, London, UK
| | - Pia R Lundegaard
- Ion Channels Group, Department of Biomedical Sciences, University of Copenhagen, Denmark
| | - Søren-Peter Olesen
- Ion Channels Group, Department of Biomedical Sciences, University of Copenhagen, Denmark
| | - Iain A Greenwood
- Ion Channels Group, Department of Biomedical Sciences, University of Copenhagen, Denmark.,Vascular Biology Research Centre, Institute for Cardiovascular and Cell Sciences, St George's University of London, London, UK
| |
Collapse
|
18
|
Auxiliary KCNE subunits modulate both homotetrameric Kv2.1 and heterotetrameric Kv2.1/Kv6.4 channels. Sci Rep 2015; 5:12813. [PMID: 26242757 PMCID: PMC4525287 DOI: 10.1038/srep12813] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 07/08/2015] [Indexed: 01/21/2023] Open
Abstract
The diversity of the voltage-gated K(+) (Kv) channel subfamily Kv2 is increased by interactions with auxiliary β-subunits and by assembly with members of the modulatory so-called silent Kv subfamilies (Kv5-Kv6 and Kv8-Kv9). However, it has not yet been investigated whether these two types of modulating subunits can associate within and modify a single channel complex simultaneously. Here, we demonstrate that the transmembrane β-subunit KCNE5 modifies the Kv2.1/Kv6.4 current extensively, whereas KCNE2 and KCNE4 only exert minor effects. Co-expression of KCNE5 with Kv2.1 and Kv6.4 did not alter the Kv2.1/Kv6.4 current density but modulated the biophysical properties significantly; KCNE5 accelerated the activation, slowed the deactivation and steepened the slope of the voltage-dependence of the Kv2.1/Kv6.4 inactivation by accelerating recovery of the closed-state inactivation. In contrast, KCNE5 reduced the current density ~2-fold without affecting the biophysical properties of Kv2.1 homotetramers. Co-localization of Kv2.1, Kv6.4 and KCNE5 was demonstrated with immunocytochemistry and formation of Kv2.1/Kv6.4/KCNE5 and Kv2.1/KCNE5 complexes was confirmed by Fluorescence Resonance Energy Transfer experiments performed in HEK293 cells. These results suggest that a triple complex consisting of Kv2.1, Kv6.4 and KCNE5 subunits can be formed. In vivo, formation of such tripartite Kv2.1/Kv6.4/KCNE5 channel complexes might contribute to tissue-specific fine-tuning of excitability.
Collapse
|
19
|
Abstract
Ion channels are essential for basic cellular function and for processes including sensory perception and intercellular communication in multicellular organisms. Voltage-gated potassium (Kv) channels facilitate dynamic cellular repolarization during an action potential, opening in response to membrane depolarization to facilitate K+ efflux. In both excitable and nonexcitable cells other, constitutively active, K+ channels provide a relatively constant repolarizing force to control membrane potential, ion homeostasis, and secretory processes. Of the forty known human Kv channel pore-forming α subunits that coassemble in various combinations to form the fundamental tetrameric channel pore and voltage sensor module, KCNQ1 is unique. KCNQ1 stands alone in having the capacity to form either channels that are voltage-dependent and require membrane depolarization for activation, or constitutively active channels. In mammals, KCNQ1 regulates processes including gastric acid secretion, thyroid hormone biosynthesis, salt and glucose homeostasis, and cell volume and in some species is required for rhythmic beating of the heart. In this review, the author discusses the unique functional properties, regulation, cell biology, diverse physiological roles, and involvement in human disease states of this chameleonic K+ channel.
Collapse
|
20
|
Zhang X, Hughes BA. KCNQ and KCNE potassium channel subunit expression in bovine retinal pigment epithelium. Exp Eye Res 2013. [DOI: 10.1016/j.exer.2013.10.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
21
|
Wang Y, Zankov DP, Jiang M, Zhang M, Henderson SC, Tseng GN. [Ca2+]i elevation and oxidative stress induce KCNQ1 protein translocation from the cytosol to the cell surface and increase slow delayed rectifier (IKs) in cardiac myocytes. J Biol Chem 2013; 288:35358-71. [PMID: 24142691 DOI: 10.1074/jbc.m113.504746] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Our goals are to simultaneously determine the three-dimensional distribution patterns of KCNQ1 and KCNE1 in cardiac myocytes and to study the mechanism and functional implications for variations in KCNQ1/KCNE1 colocalization in myocytes. We monitored the distribution patterns of KCNQ1, KCNE1, and markers for subcellular compartments/organelles using immunofluorescence/confocal microscopy and confirmed the findings in ventricular myocytes by directly observing fluorescently tagged KCNQ1-GFP and KCNE1-dsRed expressed in these cells. We also monitored the effects of stress on KCNQ1-GFP and endoplasmic reticulum (ER) remodeling during live cell imaging. The data showed that 1) KCNE1 maintained a stable cell surface localization, whereas KCNQ1 exhibited variations in the cytosolic compartment (striations versus vesicles) and the degree of presence on the cell surface; 2) the degree of cell surface KCNQ1/KCNE1 colocalization was positively correlated with slow delayed rectifier (IKs) current density; 3) KCNQ1 and calnexin (an ER marker) shared a cytosolic compartment; and 4) in response to stress ([Ca(2+)]i elevation, oxidative overload, or AT1R stimulation), KCNQ1 exited the cytosolic compartment and trafficked to the cell periphery in vesicles. This was accompanied by partial ER fragmentation. We conclude that the cellular milieu regulates KCNQ1 distribution in cardiac myocytes and that stressful conditions can increase IKs by inducing KCNQ1 movement to the cell surface. This represents a hitherto unrecognized mechanism by which IKs fulfills its function as a repolarization reserve in ventricular myocytes.
Collapse
Affiliation(s)
- Yuhong Wang
- From the Department of Physiology and Biophysics and
| | | | | | | | | | | |
Collapse
|
22
|
The voltage-gated channel accessory protein KCNE2: multiple ion channel partners, multiple ways to long QT syndrome. Expert Rev Mol Med 2011; 13:e38. [DOI: 10.1017/s1462399411002092] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The single-pass transmembrane protein KCNE2 or MIRP1 was once thought to be the missing accessory protein that combined with hERG to fully recapitulate the cardiac repolarising current IKr. As a result of this role, it was an easy next step to associate mutations in KCNE2 to long QT syndrome, in which there is delayed repolarisation of the heart. Since that time however, KCNE2 has been shown to modify the behaviour of several other channels and currents, and its role in the heart and in the aetiology of long QT syndrome has become less clear. In this article, we review the known interactions of the KCNE2 protein and the resulting functional effects, and the effects of mutations in KCNE2 and their clinical role.
Collapse
|
23
|
Solé L, Felipe A. Does a physiological role for KCNE subunits exist in the immune system? Commun Integr Biol 2011; 3:166-8. [PMID: 20585512 DOI: 10.4161/cib.3.2.10602] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Accepted: 11/10/2009] [Indexed: 11/19/2022] Open
Abstract
The study of channel modulation by regulatory subunits has attracted considerable attention. Evidence indicates a pivotal role for accessory proteins in the channelosome. For instance, these regulatory subunits are necessary to recapitulate in vivo ion currents and to further understand the physiological role of ion channels. KCNEs are a family of regulatory subunits that interact with a wide range of channels. We have described for the first time a molecular interaction between KCNE4 and the voltage-dependent potassium channel K(V)1.3. The association of KCNE4, which alters the biophysical properties, trafficking and membrane localization of K(V)1.3, functions as an endogenous dominantnegative mechanism. Since both proteins are expressed in the immune system, K(V)1.3/KCNE4 channels may contribute to the fine-tuning of the immune response. Therefore, our results point to KCNE4 as a novel target for immunomodulation. KCNE4 is not the only KCNE which is expressed in leukocytes. All KCNEs (KCNE1-5) are present, and some members demonstrate modulation during proliferation and cancer. In summary, regulatory KCNE subunits are expressed in the immune system. In addition, several voltage-dependent K(+) channels, which could interact with KCNEs, are also detected. Therefore, KCNE subunits may play a yet undiscovered role in the physiology of the immune system.
Collapse
Affiliation(s)
- Laura Solé
- Molecular Physiology Laboratory; Departament de Bioquímica i Biologia Molecular; Institut de Biomedicina; Universitat de Barcelona; Barcelona, Spain
| | | |
Collapse
|
24
|
Ciampa EJ, Welch RC, Vanoye CG, George AL. KCNE4 juxtamembrane region is required for interaction with calmodulin and for functional suppression of KCNQ1. J Biol Chem 2010; 286:4141-9. [PMID: 21118809 DOI: 10.1074/jbc.m110.158865] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Voltage-gated potassium (K(V)) channels, such as KCNQ1 (K(V)7.1), are modulated by accessory subunits and regulated by intracellular second messengers. Accessory subunits belonging to the KCNE family exert diverse functional effects on KCNQ1, have been implicated in the pathogenesis of various genetic disorders of heart rhythm, and contribute to transducing intracellular signaling events into changes in K(V) channel activity. We investigated the interactions between calmodulin (CaM), the ubiquitous Ca(2+)-transducing protein that binds and confers Ca(2+) sensitivity to the biophysical properties of KCNQ1, and KCNE4. These studies were motivated by the observed similarities between the suppression of KCNQ1 function by pharmacological disruption of KCNQ1-CaM interactions and the effects of KCNE4 co-expression on the channel. We determined that KCNE4, but not KCNE1, can biochemically interact with CaM and that this interaction is Ca(2+)-dependent and requires a tetraleucine motif in the juxtamembrane region of the KCNE4 C terminus. Furthermore, disruption of the KCNE4-CaM interaction either by mutagenesis of the tetraleucine motif or by acute Ca(2+) chelation impairs the ability of KCNE4 to inhibit KCNQ1. Our findings have potential relevance to KCNQ1 regulation both by KCNE accessory subunits and by an important intracellular signaling molecule.
Collapse
Affiliation(s)
- Erin J Ciampa
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232, USA
| | | | | | | |
Collapse
|
25
|
Abstract
The KCNQ1 voltage-gated potassium channel and its auxiliary subunit KCNE1 play a crucial role in the regulation of the heartbeat. The stoichiometry of KCNQ1 and KCNE1 complex has been debated, with some results suggesting that the four KCNQ1 subunits that form the channel associate with two KCNE1 subunits (a 42 stoichiometry), while others have suggested that the stoichiometry may not be fixed. We applied a single molecule fluorescence bleaching method to count subunits in many individual complexes and found that the stoichiometry of the KCNQ1 - KCNE1 complex is flexible, with up to four KCNE1 subunits associating with the four KCNQ1 subunits of the channel (a 44 stoichiometry). The proportion of the various stoichiometries was found to depend on the relative expression densities of KCNQ1 and KCNE1. Strikingly, both the voltage-dependence and kinetics of gating were found to depend on the relative densities of KCNQ1 and KCNE1, suggesting the heart rhythm may be regulated by the relative expression of the auxiliary subunit and the resulting stoichiometry of the channel complex.
Collapse
|
26
|
Roura-Ferrer M, Solé L, Oliveras A, Dahan R, Bielanska J, Villarroel A, Comes N, Felipe A. Impact of KCNE subunits on KCNQ1 (Kv7.1) channel membrane surface targeting. J Cell Physiol 2010; 225:692-700. [PMID: 20533308 DOI: 10.1002/jcp.22265] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The KCNQ1 (Kv7.1) channel plays an important role in cardiovascular physiology. Cardiomyocytes co-express KCNQ1 with KCNE1-5 proteins. KCNQ1 may co-associate with multiple KCNE regulatory subunits to generate different biophysically and pharmacologically distinct channels. Increasing evidence indicates that the location and targeting of channels are important determinants of their function. In this context, the presence of K(+) channels in sphingolipid-cholesterol-enriched membrane microdomains (lipid rafts) is under investigation. Lipid rafts are important for cardiovascular functioning. We aimed to determine whether KCNE subunits modify the localization and targeting of KCNQ1 channels in lipid rafts microdomains. HEK-293 cells were transiently transfected with KCNQ1 and KCNE1-5, and their traffic and presence in lipid rafts were analyzed. Only KCNQ1 and KCNE3, when expressed alone, co-localized in raft fractions. In addition, while KCNE2 and KCNE5 notably stained the cell surface, KCNQ1 and the rest of the KCNEs showed strong intracellular retention. KCNQ1 targets multiple membrane surface microdomains upon association with KCNE peptides. Thus, while KCNQ1/KCNE1 and KCNQ1/KCNE2 channels target lipid rafts, KCNQ1 associated with KCNE3-5 did not. Channel membrane dynamics, analyzed by fluorescence recovery after photobleaching (FRAP) experiments, further supported these results. In conclusion, the trafficking and targeting pattern of KCNQ1 can be influenced by its association with KCNEs. Since KCNQ1 is crucial for cardiovascular physiology, the temporal and spatial regulations that different KCNE subunits may confer to the channels could have a dramatic impact on membrane electrical activity and putative endocrine regulation.
Collapse
Affiliation(s)
- Meritxell Roura-Ferrer
- Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
| | | | | | | | | | | | | | | |
Collapse
|
27
|
Levy DI, Cepaitis E, Wanderling S, Toth PT, Archer SL, Goldstein SAN. The membrane protein MiRP3 regulates Kv4.2 channels in a KChIP-dependent manner. J Physiol 2010; 588:2657-68. [PMID: 20498229 DOI: 10.1113/jphysiol.2010.191395] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
MiRP3, the single-span membrane protein encoded by KCNE4, is localized by immunofluorescence microscopy to the transverse tubules of murine cardiac myocytes. MiRP3 is found to co-localize with Kv4.2 subunits that contribute to cardiac transient outward potassium currents (I(to)). Whole-cell, voltage-clamp recordings of human MiRP3 and Kv4.2 expressed in a clonal cell line (tsA201) reveal MiRP3 to modulate Kv4.2 current activation, inactivation and recovery from inactivation. MiRP3 shifts the half-maximal voltage for activation (V(1/2)) approximately 20 mV and slows time to peak approximately 100%. In addition, MiRP3 slows inactivation approximately 100%, speeds recovery from inactivation approximately 30%, and enhances restored currents so they 'overshoot' baseline levels. The cytoplasmic accessory subunit KChIP2 also assembles with Kv4.2 in tsA201 cells to increase peak current, shift V(1/2) approximately 5 mV, slow time to peak approximately 10%, slow inactivation approximately 100%, and speed recovery from inactivation approximately 250% without overshoot. Simultaneous expression of all three subunits yields a biophysical profile unlike either accessory subunit alone, abolishes MiRP3-induced overshoot, and allows biochemical isolation of the ternary complex. Thus, regional heterogeneity in cardiac expression of MiRP3, Kv4.2 and KChIP2 in health and disease may establish the local attributes and magnitude of cardiac I(to).
Collapse
Affiliation(s)
- Daniel I Levy
- Department of Medicine, Biological Sciences Division, Pritzker School of Medicine, University of Chicago, Chicago, IL 60637, USA.
| | | | | | | | | | | |
Collapse
|
28
|
Vanoye CG, Welch RC, Tian C, Sanders CR, George AL. KCNQ1/KCNE1 assembly, co-translation not required. Channels (Austin) 2010; 4:108-14. [PMID: 20139709 DOI: 10.4161/chan.4.2.11141] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Voltage-gated potassium channels are often assembled with accessory proteins that increase their functional diversity. KCNE proteins are small accessory proteins that modulate voltage-gated potassium (K(V)) channels. Although the functional effects of various KCNE proteins have been described, many questions remain regarding their assembly with the pore-forming subunits. For example, while previous experiments with some K(V) channels suggest that the association of the pore-subunit with the accessory subunits occurs co-translationally in the endoplasmic reticulum, it is not known whether KCNQ1 assembly with KCNE1 occurs in a similar manner to generate the medically important cardiac slow delayed rectifier current (I(Ks)). In this study we used a novel approach to demonstrate that purified recombinant human KCNE1 protein (prKCNE1) modulates KCNQ1 channels heterologously expressed in Xenopus oocytes resulting in generation of I(Ks). Incubation of KCNQ1-expressing oocytes with cycloheximide did not prevent I(Ks) expression following prKCNE1 injection. By contrast, incubation with brefeldin A prevented KCNQ1 modulation by prKCNE1. Moreover, injection of the trafficking-deficient KCNE1-L51H reduced KCNQ1 currents. Together, these observations indicate that while assembly of KCNE1 with KCNQ1 does not require co-translation, functional KCNQ1-prKCNE1 channels assemble early in the secretory pathway and reach the plasma membrane via vesicular trafficking.
Collapse
Affiliation(s)
- Carlos G Vanoye
- Department of Medicine, Vanderbilt University, Nashville, TN, USA.
| | | | | | | | | |
Collapse
|
29
|
Lundby A, Tseng GN, Schmitt N. Structural basis for K(V)7.1-KCNE(x) interactions in the I(Ks) channel complex. Heart Rhythm 2009; 7:708-13. [PMID: 20206317 DOI: 10.1016/j.hrthm.2009.12.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Accepted: 12/16/2009] [Indexed: 10/20/2022]
Abstract
The cardiac I(Ks) current is involved in action potential repolarization, where its primary function is to limit action potential prolongation during sympathetic stimulation. The I(Ks) channel is mainly composed of K(V)7.1 ion channels associated with KCNE1 auxiliary subunits. The availability of KCNE1 solution structure by nuclear magnetic resonance spectroscopy in conjunction with biochemical assays addressing K(V)7.1-KCNE1 residue interactions has provided new insights into the structural basis for K(V)7.1 modulation by KCNE1. Recent evidence further suggests that KCNE2 may associate with the K(V)7.1-KCNE1 channel complex and modulate its current amplitude. Here we review recent studies in this area and discuss potential roles for multiple KCNE(x) subunits in I(Ks) generation and modulation as well as the clinical relevance of the new information.
Collapse
Affiliation(s)
- Alicia Lundby
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | | | | |
Collapse
|
30
|
Vanoye CG, Welch RC, Daniels MA, Manderfield LJ, Tapper AR, Sanders CR, George AL. Distinct subdomains of the KCNQ1 S6 segment determine channel modulation by different KCNE subunits. ACTA ACUST UNITED AC 2009; 134:207-17. [PMID: 19687231 PMCID: PMC2737226 DOI: 10.1085/jgp.200910234] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Modulation of voltage-gated potassium (KV) channels by the KCNE family of single transmembrane proteins has physiological and pathophysiological importance. All five KCNE proteins (KCNE1–KCNE5) have been demonstrated to modulate heterologously expressed KCNQ1 (KV7.1) with diverse effects, making this channel a valuable experimental platform for elucidating structure–function relationships and mechanistic differences among members of this intriguing group of accessory subunits. Here, we specifically investigated the determinants of KCNQ1 inhibition by KCNE4, the least well-studied KCNE protein. In CHO-K1 cells, KCNQ1, but not KCNQ4, is strongly inhibited by coexpression with KCNE4. By studying KCNQ1-KCNQ4 chimeras, we identified two adjacent residues (K326 and T327) within the extracellular end of the KCNQ1 S6 segment that determine inhibition of KCNQ1 by KCNE4. This dipeptide motif is distinct from neighboring S6 sequences that enable modulation by KCNE1 and KCNE3. Conversely, S6 mutations (S338C and F340C) that alter KCNE1 and KCNE3 effects on KCNQ1 do not abrogate KCNE4 inhibition. Further, KCNQ1-KCNQ4 chimeras that exhibited resistance to the inhibitory effects of KCNE4 still interact biochemically with this protein, implying that accessory subunit binding alone is not sufficient for channel modulation. These observations indicate that the diverse functional effects observed for KCNE proteins depend, in part, on structures intrinsic to the pore-forming subunit, and that distinct S6 subdomains determine KCNQ1 responses to KCNE1, KCNE3, and KCNE4.
Collapse
Affiliation(s)
- Carlos G Vanoye
- Division of Genetic Medicine, Department of Medicine, Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, USA
| | | | | | | | | | | | | |
Collapse
|
31
|
Clancy SM, Chen B, Bertaso F, Mamet J, Jegla T. KCNE1 and KCNE3 beta-subunits regulate membrane surface expression of Kv12.2 K(+) channels in vitro and form a tripartite complex in vivo. PLoS One 2009; 4:e6330. [PMID: 19623261 PMCID: PMC2710002 DOI: 10.1371/journal.pone.0006330] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 06/17/2009] [Indexed: 01/14/2023] Open
Abstract
Voltage-gated potassium channels that activate near the neuronal resting membrane potential are important regulators of excitation in the nervous system, but their functional diversity is still not well understood. For instance, Kv12.2 (ELK2, KCNH3) channels are highly expressed in the cerebral cortex and hippocampus, and although they are most likely to contribute to resting potassium conductance, surprisingly little is known about their function or regulation. Here we demonstrate that the auxiliary MinK (KCNE1) and MiRP2 (KCNE3) proteins are important regulators of Kv12.2 channel function. Reduction of endogenous KCNE1 or KCNE3 expression by siRNA silencing, significantly increased macroscopic Kv12.2 currents in Xenopus oocytes by around 4-fold. Interestingly, an almost 9-fold increase in Kv12.2 currents was observed with the dual injection of KCNE1 and KCNE3 siRNA, suggesting an additive effect. Consistent with these findings, over-expression of KCNE1 and/or KCNE3 suppressed Kv12.2 currents. Membrane surface biotinylation assays showed that surface expression of Kv12.2 was significantly increased by KCNE1 and KCNE3 siRNA, whereas total protein expression of Kv12.2 was not affected. KCNE1 and KCNE3 siRNA shifted the voltages for half-maximal activation to more hyperpolarized voltages, indicating that KCNE1 and KCNE3 may also inhibit activation gating of Kv12.2. Native co-immunoprecipitation assays from mouse brain membranes imply that KCNE1 and KCNE3 interact with Kv12.2 simultaneously in vivo, suggesting the existence of novel KCNE1-KCNE3-Kv12.2 channel tripartite complexes. Together these data indicate that KCNE1 and KCNE3 interact directly with Kv12.2 channels to regulate channel membrane trafficking.
Collapse
Affiliation(s)
- Sinead M. Clancy
- Department of Cell Biology, Institute for Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, California, United States of America
| | - Bihan Chen
- Department of Cell Biology, Institute for Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, California, United States of America
| | - Federica Bertaso
- Department of Cell Biology, Institute for Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, California, United States of America
| | - Julien Mamet
- Department of Cell Biology, Institute for Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, California, United States of America
| | - Timothy Jegla
- Department of Cell Biology, Institute for Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, California, United States of America
- * E-mail:
| |
Collapse
|
32
|
Jiang M, Xu X, Wang Y, Toyoda F, Liu XS, Zhang M, Robinson RB, Tseng GN. Dynamic partnership between KCNQ1 and KCNE1 and influence on cardiac IKs current amplitude by KCNE2. J Biol Chem 2009; 284:16452-16462. [PMID: 19372218 DOI: 10.1074/jbc.m808262200] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cardiac slow delayed rectifier (IKs) channel is composed of KCNQ1 (pore-forming) and KCNE1 (auxiliary) subunits. Although KCNE1 is an obligate IKs component that confers the uniquely slow gating kinetics, KCNE2 is also expressed in human heart. In vitro experiments suggest that KCNE2 can associate with the KCNQ1-KCNE1 complex to suppress the current amplitude without altering the slow gating kinetics. Our goal here is to test the role of KCNE2 in cardiac IKs channel function. Pulse-chase experiments in COS-7 cells show that there is a KCNE1 turnover in the KCNQ1-KCNE1 complex, supporting the possibility that KCNE1 in the IKs channel complex can be substituted by KCNE2 when the latter is available. Biotinylation experiments in COS-7 cells show that although KCNE1 relies on KCNQ1 coassembly for more efficient cell surface expression, KCNE2 can independently traffic to the cell surface, thus becoming available for substituting KCNE1 in the IKs channel complex. Injecting vesicles carrying KCNE1 or KCNE2 into KCNQ1-expressing oocytes leads to KCNQ1 modulation in the same manner as KCNQ1+KCNEx (where x=1 or 2) cRNA coinjection. Thus, free KCNEx peptides delivered to the cell membrane can associate with existing KCNQ1 channels to modulate their function. Finally, adenovirus-mediated KCNE2 expression in adult guinea pig ventricular myocytes exhibited colocalization with native KCNQ1 protein and reduces the native IKs current density. We propose that in cardiac myocytes the IKs current amplitude is under dynamic control by the availability of KCNE2 subunits in the cell membrane.
Collapse
Affiliation(s)
- Min Jiang
- From the Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Xulin Xu
- From the Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Yuhong Wang
- From the Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Futoshi Toyoda
- Department of Physiology, Shiga University of Medical Science, Shiga 520-2192, Japan
| | - Xian-Sheng Liu
- From the Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Mei Zhang
- From the Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298
| | - Richard B Robinson
- Department of Pharmacology and Center for Molecular Therapeutics, Columbia University, New York, New York 10032
| | - Gea-Ny Tseng
- From the Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298.
| |
Collapse
|
33
|
Xu X, Kanda VA, Choi E, Panaghie G, Roepke TK, Gaeta SA, Christini DJ, Lerner DJ, Abbott GW. MinK-dependent internalization of the IKs potassium channel. Cardiovasc Res 2009; 82:430-8. [PMID: 19202166 DOI: 10.1093/cvr/cvp047] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS KCNQ1-MinK potassium channel complexes (4alpha:2beta stoichiometry) generate IKs, the slowly activating human cardiac ventricular repolarization current. The MinK ancillary subunit slows KCNQ1 activation, eliminates its inactivation, and increases its unitary conductance. However, KCNQ1 transcripts outnumber MinK transcripts five to one in human ventricles, suggesting KCNQ1 also forms other heteromeric or even homomeric channels there. Mechanisms governing which channel types prevail have not previously been reported, despite their significance: normal cardiac rhythm requires tight control of IKs density and kinetics, and inherited mutations in KCNQ1 and MinK can cause ventricular fibrillation and sudden death. Here, we describe a novel mechanism for this control. METHODS AND RESULTS Whole-cell patch-clamping, confocal immunofluorescence microscopy, antibody feeding, biotin feeding, fluorescent transferrin feeding, and protein biochemistry techniques were applied to COS-7 cells heterologously expressing KCNQ1 with wild-type or mutant MinK and dynamin 2 and to native IKs channels in guinea-pig myocytes. KCNQ1-MinK complexes, but not homomeric KCNQ1 channels, were found to undergo clathrin- and dynamin 2-dependent internalization (DDI). Three sites on the MinK intracellular C-terminus were, in concert, necessary and sufficient for DDI. Gating kinetics and sensitivity to XE991 indicated that DDI decreased cell-surface KCNQ1-MinK channels relative to homomeric KCNQ1, decreasing whole-cell current but increasing net activation rate; inhibiting DDI did the reverse. CONCLUSION The data redefine MinK as an endocytic chaperone for KCNQ1 and present a dynamic mechanism for controlling net surface Kv channel subunit composition-and thus current density and gating kinetics-that may also apply to other alpha-beta type Kv channel complexes.
Collapse
Affiliation(s)
- Xianghua Xu
- Greenberg Division of Cardiology, Department of Medicine, Weill Medical College of Cornell University, Starr 463, 520 East 70th Street, New York, NY 10065, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Manderfield LJ, Daniels MA, Vanoye CG, George AL. KCNE4 domains required for inhibition of KCNQ1. J Physiol 2008; 587:303-14. [PMID: 19029186 DOI: 10.1113/jphysiol.2008.161281] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Voltage-gated potassium (Kv) channels are modulated in distinct ways by members of the KCNE family of single transmembrane domain accessory subunits. KCNE4 has a dramatic inhibitory effect on KCNQ1 that differs substantially from the activating effects of KCNE1 and KCNE3. The structural features of KCNE4 that enable this behaviour are unknown. We exploited chimeras of KCNE1, KCNE3 and KCNE4 to identify specific domains responsible for the inhibitory effects on heterologously expressed KCNQ1. Previous structure-function analysis of KCNE1 and KCNE3 identified a critical tripeptide motif within the transmembrane domain that accounts for the differences in KCNQ1 modulation evoked by these two KCNE proteins. Swapping the transmembrane tripeptide motif of KCNE4 with the corresponding amino acid sequence of KCNE1 did not influence the behaviour of either protein. Similarly, exchanging the tripeptide regions of KCNE3 and KCNE4 further demonstrated that this transmembrane motif does not explain the activity of KCNE4. Using a more systematic approach, we demonstrated that the KCNE4 C-terminus was critical for KCNQ1 modulation. Replacement of the KCNE1 or KCNE3 C-termini with that of KCNE4 created chimeric proteins that strongly inhibited KCNQ1. Additional evidence supported a cooperative role of the KCNE4 transmembrane domain. Although the C-terminus was necessary for KCNE4 activity, we demonstrated that a surrogate transmembrane domain derived from the cytokine receptor CD8 did not enable inhibition of KCNQ1, indicating that the KCNE4 C-terminus alone was not sufficient for KCNQ1 modulation. We further demonstrated that the KCNE4 C-terminus interacts with KCNQ1. Our data reveal important structure-function relationships for KCNE4 that help advance our understanding of potassium channel modulation by KCNE proteins.
Collapse
Affiliation(s)
- Lauren J Manderfield
- Department of Pharmacology, Department of Medicine, Vanderbilt University, Nashville, TN 37232-0275, USA
| | | | | | | |
Collapse
|
35
|
Structure, function, and modification of the voltage sensor in voltage-gated ion channels. Cell Biochem Biophys 2008; 52:149-74. [PMID: 18989792 DOI: 10.1007/s12013-008-9032-5] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/01/2008] [Indexed: 01/12/2023]
Abstract
Voltage-gated ion channels are crucial for both neuronal and cardiac excitability. Decades of research have begun to unravel the intriguing machinery behind voltage sensitivity. Although the details regarding the arrangement and movement in the voltage-sensor domain are still debated, consensus is slowly emerging. There are three competing conceptual models: the helical-screw, the transporter, and the paddle model. In this review we explore the structure of the activated voltage-sensor domain based on the recent X-ray structure of a chimera between Kv1.2 and Kv2.1. We also present a model for the closed state. From this we conclude that upon depolarization the voltage sensor S4 moves approximately 13 A outwards and rotates approximately 180 degrees, thus consistent with the helical-screw model. S4 also moves relative to S3b which is not consistent with the paddle model. One interesting feature of the voltage sensor is that it partially faces the lipid bilayer and therefore can interact both with the membrane itself and with physiological and pharmacological molecules reaching the channel from the membrane. This type of channel modulation is discussed together with other mechanisms for how voltage-sensitivity is modified. Small effects on voltage-sensitivity can have profound effects on excitability. Therefore, medical drugs designed to alter the voltage dependence offer an interesting way to regulate excitability.
Collapse
|
36
|
Gao Z, Xiong Q, Sun H, Li M. Desensitization of chemical activation by auxiliary subunits: convergence of molecular determinants critical for augmenting KCNQ1 potassium channels. J Biol Chem 2008; 283:22649-58. [PMID: 18490447 DOI: 10.1074/jbc.m802426200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Chemical openers for KCNQ potassium channels are useful probes both for understanding channel gating and for developing therapeutics. The five KCNQ isoforms (KCNQ1 to KCNQ5, or Kv7.1 to Kv7.5) are differentially localized. Therefore, the molecular specificity of chemical openers is an important subject of investigation. Native KCNQ1 normally exists in complex with auxiliary subunits known as KCNE. In cardiac myocytes, the KCNQ1-KCNE1 (IsK or minK) channel is thought to underlie the I(Ks) current, a component critical for membrane repolarization during cardiac action potential. Hence, the molecular and pharmacological differences between KCNQ1 and KCNQ1-KCNE1 channels have been important topics. Zinc pyrithione (ZnPy) is a newly identified KCNQ channel opener, which potently activates KCNQ2, KCNQ4, and KCNQ5. However, the ZnPy effects on cardiac KCNQ1 potassium channels remain largely unknown. Here we show that ZnPy effectively augments the KCNQ1 current, exhibiting an increase in current amplitude, reduction of inactivation, and slowing of both activation and deactivation. Some of these are reminiscent of effects by KCNE1. In addition, neither the heteromultimeric KCNQ1-KCNE1 channels nor native I(Ks) current displayed any sensitivity to ZnPy, indicating that the static occupancy by a KCNE subunit desensitizes the reversible effects by a chemical opener. Site-directed mutagenesis of KCNQ1 reveals that residues critical for the potentiation effects by either ZnPy or KCNE are clustered together in the S6 region overlapping with the critical gating determinants. Thus, the convergence of potentiation effects and molecular determinants critical for both an auxiliary subunit and a chemical opener argue for a mechanistic overlap in causing potentiation.
Collapse
Affiliation(s)
- Zhaobing Gao
- Department of Neuroscience and High Throughput Biology Center, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
| | | | | | | |
Collapse
|
37
|
Levy DI, Wanderling S, Biemesderfer D, Goldstein SAN. MiRP3 acts as an accessory subunit with the BK potassium channel. Am J Physiol Renal Physiol 2008; 295:F380-7. [PMID: 18463315 DOI: 10.1152/ajprenal.00598.2007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
MinK-related peptides (MiRPs) are single-span membrane proteins that assemble with specific voltage-gated K+ (Kv) channel alpha-subunits to establish gating kinetics, unitary conductance, expression level, and pharmacology of the mixed complex. MiRP3 (encoded by the KCNE4 gene) has been shown to alter the behavior of some Kv alpha-subunits in vitro but its natural partners and physiologic functions are unknown. Seeking in vivo partners for MiRP3, immunohistochemistry was used to localize its expression to a unique subcellular site, the apical membrane of renal intercalated cells, where one potassium channel type has been recorded, the calcium- and voltage-gated channel BK. Overlapping staining of these two proteins was found in rabbit intercalated cells, and MiRP3 and BK subunits expressed in tissue culture cells were found to form detergent-stable complexes. Electrophysiologic and biochemical evaluation showed MiRP3 to act on BK to reduce current density in two fashions: shifting the current-voltage relationship to more depolarized voltages in a calcium-dependent fashion ( approximately 10 mV at normal intracellular calcium levels) and accelerating degradation of MiRP3-BK complexes. The findings suggest a role for MiRP3 modulation of BK-dependent urinary potassium excretion.
Collapse
Affiliation(s)
- Daniel I Levy
- Department of Medicine, Biological Sciences Division, University of Chicago, Chicago, Illinois, USA.
| | | | | | | |
Collapse
|