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Delgado-Bermúdez A, Yeste M, Bonet S, Pinart E. Physiological role of potassium channels in mammalian germ cell differentiation, maturation, and capacitation. Andrology 2024. [PMID: 38436215 DOI: 10.1111/andr.13606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 01/16/2024] [Accepted: 01/29/2024] [Indexed: 03/05/2024]
Abstract
BACKGROUND Ion channels are essential for differentiation and maturation of germ cells, and even for fertilization in mammals. Different types of potassium channels have been identified, which are grouped into voltage-gated channels (Kv), ligand-gated channels (Kligand ), inwardly rectifying channels (Kir ), and tandem pore domain channels (K2P ). MATERIAL-METHODS The present review includes recent findings on the role of potassium channels in sperm physiology of mammals. RESULTS-DISCUSSION While most studies conducted thus far have been focused on the physiological role of voltage- (Kv1, Kv3, and Kv7) and calcium-gated channels (SLO1 and SLO3) during sperm capacitation, especially in humans and rodents, little data about the types of potassium channels present in the plasma membrane of differentiating germ cells exist. In spite of this, recent evidence suggests that the content and regulation mechanisms of these channels vary throughout spermatogenesis. Potassium channels are also essential for the regulation of sperm cell volume during epididymal maturation and for preventing premature membrane hyperpolarization. It is important to highlight that the nature, biochemical properties, localization, and regulation mechanisms of potassium channels are species-specific. In effect, while SLO3 is the main potassium channel involved in the K+ current during sperm capacitation in rodents, different potassium channels are implicated in the K+ outflow and, thus, plasma membrane hyperpolarization during sperm capacitation in other mammalian species, such as humans and pigs. CONCLUSIONS Potassium conductance is essential for male fertility, not only during sperm capacitation but throughout the spermiogenesis and epididymal maturation.
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Affiliation(s)
- Ariadna Delgado-Bermúdez
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain
- Department of Biology, Faculty of Sciences, Unit of Cell Biology, University of Girona, Girona, Spain
| | - Marc Yeste
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain
- Department of Biology, Faculty of Sciences, Unit of Cell Biology, University of Girona, Girona, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
| | - Sergi Bonet
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain
- Department of Biology, Faculty of Sciences, Unit of Cell Biology, University of Girona, Girona, Spain
| | - Elisabeth Pinart
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain
- Department of Biology, Faculty of Sciences, Unit of Cell Biology, University of Girona, Girona, Spain
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Ferreira G, Santander A, Cardozo R, Chavarría L, Domínguez L, Mujica N, Benítez M, Sastre S, Sobrevia L, Nicolson GL. Nutrigenomics of inward rectifier potassium channels. Biochim Biophys Acta Mol Basis Dis 2023:166803. [PMID: 37406972 DOI: 10.1016/j.bbadis.2023.166803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 06/27/2023] [Accepted: 06/30/2023] [Indexed: 07/07/2023]
Abstract
Inwardly rectifying potassium (Kir) channels play a key role in maintaining the resting membrane potential and supporting potassium homeostasis. There are many variants of Kir channels, which are usually tetramers in which the main subunit has two trans-membrane helices attached to two N- and C-terminal cytoplasmic tails with a pore-forming loop in between that contains the selectivity filter. These channels have domains that are strongly modulated by molecules present in nutrients found in different diets, such as phosphoinositols, polyamines and Mg2+. These molecules can impact these channels directly or indirectly, either allosterically by modulation of enzymes or via the regulation of channel expression. A particular type of these channels is coupled to cell metabolism and inhibited by ATP (KATP channels, essential for insulin release and for the pathogenesis of metabolic diseases like diabetes mellitus). Genomic changes in Kir channels have a significant impact on metabolism, such as conditioning the nutrients and electrolytes that an individual can take. Thus, the nutrigenomics of ion channels is an important emerging field in which we are attempting to understand how nutrients and diets can affect the activity and expression of ion channels and how genomic changes in such channels may be the basis for pathological conditions that limit nutrition and electrolyte intake. In this contribution we briefly review Kir channels, discuss their nutrigenomics, characterize how different components in the diet affect their function and expression, and suggest how their genomic changes lead to pathological phenotypes that affect diet and electrolyte intake.
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Affiliation(s)
- Gonzalo Ferreira
- Laboratory of Ion Channels, Biological Membranes and Cell Signaling, Dept. of Biophysics, Facultad de Medicina, CP 11800, Universidad de la Republica, Montevideo, Uruguay.
| | - Axel Santander
- Laboratory of Ion Channels, Biological Membranes and Cell Signaling, Dept. of Biophysics, Facultad de Medicina, CP 11800, Universidad de la Republica, Montevideo, Uruguay
| | - Romina Cardozo
- Laboratory of Ion Channels, Biological Membranes and Cell Signaling, Dept. of Biophysics, Facultad de Medicina, CP 11800, Universidad de la Republica, Montevideo, Uruguay
| | - Luisina Chavarría
- Laboratory of Ion Channels, Biological Membranes and Cell Signaling, Dept. of Biophysics, Facultad de Medicina, CP 11800, Universidad de la Republica, Montevideo, Uruguay
| | - Lucía Domínguez
- Laboratory of Ion Channels, Biological Membranes and Cell Signaling, Dept. of Biophysics, Facultad de Medicina, CP 11800, Universidad de la Republica, Montevideo, Uruguay
| | - Nicolás Mujica
- Laboratory of Ion Channels, Biological Membranes and Cell Signaling, Dept. of Biophysics, Facultad de Medicina, CP 11800, Universidad de la Republica, Montevideo, Uruguay
| | - Milagros Benítez
- Laboratory of Ion Channels, Biological Membranes and Cell Signaling, Dept. of Biophysics, Facultad de Medicina, CP 11800, Universidad de la Republica, Montevideo, Uruguay
| | - Santiago Sastre
- Laboratory of Ion Channels, Biological Membranes and Cell Signaling, Dept. of Biophysics, Facultad de Medicina, CP 11800, Universidad de la Republica, Montevideo, Uruguay; Centro de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo CP 11800, Uruguay
| | - Luis Sobrevia
- Cellular and Molecular Physiology Laboratory (CMPL), Department of Obstetrics, Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago 8330024, Chile; Department of Physiology, Faculty of Pharmacy, Universidad de Sevilla, Seville E-41012, Spain; Medical School (Faculty of Medicine), Sao Paulo State University (UNESP), Brazil; University of Queensland, Centre for Clinical Research (UQCCR), Faculty of Medicine and Biomedical Sciences, University of Queensland, Herston, 4029, Queensland, Australia; Tecnologico de Monterrey, Eutra, The Institute for Obesity Research (IOR), School of Medicine and Health Sciences, Monterrey, Nuevo León, Mexico
| | - Garth L Nicolson
- Department of Molecular Pathology, The Institute for Molecular Medicine, Huntington Beach, CA, USA
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Lv J, Xiao X, Bi M, Tang T, Kong D, Diao M, Jiao Q, Chen X, Yan C, Du X, Jiang H. ATP-sensitive potassium channels: A double-edged sword in neurodegenerative diseases. Ageing Res Rev 2022; 80:101676. [PMID: 35724860 DOI: 10.1016/j.arr.2022.101676] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 04/15/2022] [Accepted: 06/14/2022] [Indexed: 11/25/2022]
Abstract
ATP-sensitive potassium channels (KATP channels), a group of vital channels that link the electrical activity of the cell membrane with cell metabolism, were discovered on the ventricular myocytes of guinea pigs by Noma using the patch-clamp technique in 1983. Subsequently, KATP channels have been found to be expressed in pancreatic β cells, cardiomyocytes, skeletal muscle cells, and nerve cells in the substantia nigra (SN), hippocampus, cortex, and basal ganglia. KATP channel openers (KCOs) diazoxide, nicorandil, minoxidil, and the KATP channel inhibitor glibenclamide have been shown to have anti-hypertensive, anti-myocardial ischemia, and insulin-releasing regulatory effects. Increasing evidence has suggested that KATP channels also play roles in Alzheimer's disease (AD), Parkinson's disease (PD), vascular dementia (VD), Huntington's disease (HD) and other neurodegenerative diseases. KCOs and KATP channel inhibitors protect neurons from injury by regulating neuronal excitability and neurotransmitter release, inhibiting abnormal protein aggregation and Ca2+ overload, reducing reactive oxygen species (ROS) production and microglia activation. However, KATP channels have dual effects in some cases. In this review, we focus on the roles of KATP channels and their related openers and inhibitors in neurodegenerative diseases. This will enable us to precisely take advantage of the KATP channels and provide new ideas for the treatment of neurodegenerative diseases.
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Affiliation(s)
- Jirong Lv
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Medical College, Qingdao University, Qingdao, China
| | - Xue Xiao
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Medical College, Qingdao University, Qingdao, China
| | - Mingxia Bi
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Medical College, Qingdao University, Qingdao, China
| | - Tingting Tang
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Medical College, Qingdao University, Qingdao, China
| | - Deao Kong
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Medical College, Qingdao University, Qingdao, China
| | - Meining Diao
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Medical College, Qingdao University, Qingdao, China
| | - Qian Jiao
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Medical College, Qingdao University, Qingdao, China
| | - Xi Chen
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Medical College, Qingdao University, Qingdao, China
| | - Chunling Yan
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Medical College, Qingdao University, Qingdao, China
| | - Xixun Du
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Medical College, Qingdao University, Qingdao, China.
| | - Hong Jiang
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Medical College, Qingdao University, Qingdao, China.
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4
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Bazard P, Pineros J, Frisina RD, Bauer MA, Acosta AA, Paganella LR, Borakiewicz D, Thivierge M, Mannering FL, Zhu X, Ding B. Cochlear Inflammaging in Relation to Ion Channels and Mitochondrial Functions. Cells 2021; 10:2761. [PMID: 34685743 PMCID: PMC8534887 DOI: 10.3390/cells10102761] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 10/06/2021] [Accepted: 10/12/2021] [Indexed: 12/20/2022] Open
Abstract
The slow accumulation of inflammatory biomarker levels in the body-also known as inflammaging-has been linked to a myriad of age-related diseases. Some of these include neurodegenerative conditions such as Parkinson's disease, obesity, type II diabetes, cardiovascular disease, and many others. Though a direct correlation has not been established, research connecting age-related hearing loss (ARHL)-the number one communication disorder and one of the most prevalent neurodegenerative diseases of our aged population-and inflammaging has gained interest. Research, thus far, has found that inflammatory markers, such as IL-6 and white blood cells, are associated with ARHL in humans and animals. Moreover, studies investigating ion channels and mitochondrial involvement have shown promising relationships between their functions and inflammaging in the cochlea. In this review, we summarize key findings in inflammaging within the auditory system, the involvement of ion channels and mitochondrial functions, and lastly discuss potential treatment options focusing on controlling inflammation as we age.
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Affiliation(s)
- Parveen Bazard
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (J.P.); (M.A.B.); (A.A.A.); (L.R.P.); (D.B.); (M.T.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA;
| | - Jennifer Pineros
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (J.P.); (M.A.B.); (A.A.A.); (L.R.P.); (D.B.); (M.T.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA;
| | - Robert D. Frisina
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (J.P.); (M.A.B.); (A.A.A.); (L.R.P.); (D.B.); (M.T.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA;
- Department Communication Sciences and Disorders, College of Behavioral & Communication Sciences, Tampa, FL 33620, USA
- Morsani College of Medicine, University of South Florida, Tampa, FL 33620, USA
| | - Mark A. Bauer
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (J.P.); (M.A.B.); (A.A.A.); (L.R.P.); (D.B.); (M.T.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA;
| | - Alejandro A. Acosta
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (J.P.); (M.A.B.); (A.A.A.); (L.R.P.); (D.B.); (M.T.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA;
| | - Lauren R. Paganella
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (J.P.); (M.A.B.); (A.A.A.); (L.R.P.); (D.B.); (M.T.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA;
| | - Dominika Borakiewicz
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (J.P.); (M.A.B.); (A.A.A.); (L.R.P.); (D.B.); (M.T.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA;
| | - Mark Thivierge
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (J.P.); (M.A.B.); (A.A.A.); (L.R.P.); (D.B.); (M.T.); (X.Z.); (B.D.)
- Morsani College of Medicine, University of South Florida, Tampa, FL 33620, USA
| | - Freyda L. Mannering
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA;
- Morsani College of Medicine, University of South Florida, Tampa, FL 33620, USA
| | - Xiaoxia Zhu
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (J.P.); (M.A.B.); (A.A.A.); (L.R.P.); (D.B.); (M.T.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA;
| | - Bo Ding
- Department of Medical Engineering, College of Engineering, University of South Florida, Tampa, FL 33620, USA; (P.B.); (J.P.); (M.A.B.); (A.A.A.); (L.R.P.); (D.B.); (M.T.); (X.Z.); (B.D.)
- Global Center for Hearing and Speech Research, University of South Florida, Tampa, FL 33612, USA;
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5
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Lei S, Hu B. Ionic and signaling mechanisms involved in neurotensin-mediated excitation of central amygdala neurons. Neuropharmacology 2021; 196:108714. [PMID: 34271017 DOI: 10.1016/j.neuropharm.2021.108714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 07/05/2021] [Accepted: 07/09/2021] [Indexed: 10/20/2022]
Abstract
Neurotensin (NT) serves as a neuromodulator in the brain where it regulates a variety of physiological functions. Whereas the central amygdala (CeA) expresses NT peptide and NTS1 receptors and application of NT has been shown to excite CeA neurons, the underlying cellular and molecular mechanisms have not been determined. We found that activation of NTS1 receptors increased the neuronal excitability of the lateral nucleus (CeL) of CeA. Both phospholipase Cβ (PLCβ) and phosphatidylinositol 4,5-bisphosphate (PIP2) depletion were required, whereas intracellular Ca2+ release and PKC were unnecessary for NT-elicited excitation of CeL neurons. NT increased the input resistance and time constants of CeL neurons, suggesting that NT excites CeL neurons by decreasing a membrane conductance. Depressions of the inwardly rectifying K+ (Kir) channels including both the Kir2 subfamily and the GIRK channels were required for NT-elicited excitation of CeL neurons. Activation of NTS1 receptors in the CeL led to GABAergic inhibition of medial nucleus of CeA neurons, suggesting that NT modulates the network activity in the amygdala. Our results may provide a cellular and molecular mechanism to explain the physiological functions of NT in vivo.
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Affiliation(s)
- Saobo Lei
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND58203, USA.
| | - Binqi Hu
- Department of Biomedical Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND58203, USA
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6
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The intriguing effect of ethanol and nicotine on acetylcholine-sensitive potassium current IKAch: Insight from a quantitative model. PLoS One 2019; 14:e0223448. [PMID: 31600261 PMCID: PMC6786802 DOI: 10.1371/journal.pone.0223448] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 09/20/2019] [Indexed: 02/01/2023] Open
Abstract
Recent experimental work has revealed unusual features of the effect of certain drugs on cardiac inwardly rectifying potassium currents, including the constitutively active and acetylcholine-induced components of acetylcholine-sensitive current (IKAch). These unusual features have included alternating susceptibility of the current components to activation and inhibition induced by ethanol or nicotine applied at various concentrations, and significant correlation between the drug effect and the current magnitude measured under drug-free conditions. To explain these complex drug effects, we have developed a new type of quantitative model to offer a possible interpretation of the effect of ethanol and nicotine on the IKAch channels. The model is based on a description of IKAch as a sum of particular currents related to the populations of channels formed by identical assemblies of different α-subunits. Assuming two different channel populations in agreement with the two reported functional IKAch-channels (GIRK1/4 and GIRK4), the model was able to simulate all the above-mentioned characteristic features of drug-channel interactions and also the dispersion of the current measured in different cells. The formulation of our model equations allows the model to be incorporated easily into the existing integrative models of electrical activity of cardiac cells involving quantitative description of IKAch. We suppose that the model could also help make sense of certain observations related to the channels that do not show inward rectification. This new ionic channel model, based on a concept we call population type, may allow for the interpretation of complex interactions of drugs with ionic channels of various types, which cannot be done using the ionic channel models available so far.
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Bernsteiner H, Zangerl-Plessl EM, Chen X, Stary-Weinzinger A. Conduction through a narrow inward-rectifier K + channel pore. J Gen Physiol 2019; 151:1231-1246. [PMID: 31511304 PMCID: PMC6785732 DOI: 10.1085/jgp.201912359] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2019] [Revised: 07/25/2019] [Accepted: 08/13/2019] [Indexed: 12/17/2022] Open
Abstract
G-protein–gated inwardly rectifying potassium channels are important mediators of inhibitory neurotransmission. Based on microsecond-scale molecular dynamics simulations, Bernsteiner et al. propose novel gating details that may enable K+ flux via a direct knock-on mechanism. Inwardly rectifying potassium (Kir) channels play a key role in controlling membrane potentials in excitable and unexcitable cells, thereby regulating a plethora of physiological processes. G-protein–gated Kir channels control heart rate and neuronal excitability via small hyperpolarizing outward K+ currents near the resting membrane potential. Despite recent breakthroughs in x-ray crystallography and cryo-EM, the gating and conduction mechanisms of these channels are poorly understood. MD simulations have provided unprecedented details concerning the gating and conduction mechanisms of voltage-gated K+ and Na+ channels. Here, we use multi-microsecond–timescale MD simulations based on the crystal structures of GIRK2 (Kir3.2) bound to phosphatidylinositol-4,5-bisphosphate to provide detailed insights into the channel’s gating dynamics, including insights into the behavior of the G-loop gate. The simulations also elucidate the elementary steps that underlie the movement of K+ ions through an inward-rectifier K+ channel under an applied electric field. Our simulations suggest that K+ permeation might occur via direct knock-on, similar to the mechanism recently shown for Kv channels.
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Affiliation(s)
- Harald Bernsteiner
- Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
| | | | - Xingyu Chen
- Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
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8
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Robinson CV, Rohacs T, Hansen SB. Tools for Understanding Nanoscale Lipid Regulation of Ion Channels. Trends Biochem Sci 2019; 44:795-806. [PMID: 31060927 PMCID: PMC6729126 DOI: 10.1016/j.tibs.2019.04.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 03/23/2019] [Accepted: 04/01/2019] [Indexed: 11/17/2022]
Abstract
Anionic phospholipids are minor but prominent components of the plasma membrane that are necessary for ion channel function. Their persistence in bulk membranes, in particular phosphatidylinositol 4,5-bisphosphate (PIP2), initially suggested they act as channel cofactors. However, recent technologies have established an emerging system of nanoscale signaling to ion channels based on lipid compartmentalization (clustering), direct lipid binding, and local lipid dynamics that allow cells to harness lipid heterogeneity to gate ion channels. The new tools to study lipid binding are set to transform our view of the membrane and answer important questions surrounding ion channel-delimited processes such as mechanosensation.
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Affiliation(s)
- Carol V Robinson
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, UK
| | - Tibor Rohacs
- Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Scott B Hansen
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL 33458, USA; Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA.
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9
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Cheng N, Ren S, Yang JF, Liu XM, Li XT. Carvedilol blockage of delayed rectifier Kv2.1 channels and its molecular basis. Eur J Pharmacol 2019; 855:50-55. [PMID: 31063774 DOI: 10.1016/j.ejphar.2019.05.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 04/30/2019] [Accepted: 05/03/2019] [Indexed: 11/19/2022]
Abstract
Previous studies indicated that one of the action targets of carvedilol is the voltage-gated potassium (Kv) channel, which has a fundamental role in the control of electrical properties in excitable cells. It is not clear whether this compound exerts any actions specifically on delayed rectifier Kv2.1 channels. The present study is conducted on Kv2.1 currents heterologously expressed in HEK293 cells to characterize the block by carvedilol in detail, identifying molecular determinants and providing biophysical insights of the block. Macroscopic Kv2.1 currents obtained by whole-cell recording were substantially inhibited after addition of carvedilol with an IC50 value of 5.1 μM. This drug also led to a largely hyperpolarizing shift (30 mV) of the inactivation curve, which may contribute to the blocking action due to more inactivation of Kv2.1 currents occurred in depolarization potentials. Mutations at Y380 (a putative TEA binding site) and K356 (a K+ binding site) in the outer vestibule of Kv2.1 channels significantly eliminated the inhibitory effects of carvedilol and prevented the leftward shift of inactivation. Moreover, mutations at above positions modulated the effects of carvedilol on the deactivation but not activation kinetics of Kv2.1 channels. Collected data indicate that carvedilol can exert a blocking effect on the closed-state of Kv2.1 channels, and specific residues within the S5-P and P-S6 linkers in the outer vestibule may play crucial roles in carvedilol-induced blocking for Kv2.1 channels.
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Affiliation(s)
- Neng Cheng
- College of Life Science, South-Central University for Nationalities, Wuhan, 430074, China
| | - Sheng Ren
- College of Life Science, South-Central University for Nationalities, Wuhan, 430074, China
| | - Jin-Feng Yang
- College of Life Science, South-Central University for Nationalities, Wuhan, 430074, China
| | - Xiang-Ming Liu
- GongQing Institute of Science and Technology, Gongqing City, 332020, China
| | - Xian-Tao Li
- College of Life Science, South-Central University for Nationalities, Wuhan, 430074, China.
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10
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Sarmiento BE, Santos Menezes LF, Schwartz EF. Insulin Release Mechanism Modulated by Toxins Isolated from Animal Venoms: From Basic Research to Drug Development Prospects. Molecules 2019; 24:E1846. [PMID: 31091684 PMCID: PMC6571724 DOI: 10.3390/molecules24101846] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 04/23/2019] [Accepted: 05/09/2019] [Indexed: 12/12/2022] Open
Abstract
Venom from mammals, amphibians, snakes, arachnids, sea anemones and insects provides diverse sources of peptides with different potential medical applications. Several of these peptides have already been converted into drugs and some are still in the clinical phase. Diabetes type 2 is one of the diseases with the highest mortality rate worldwide, requiring specific attention. Diverse drugs are available (e.g., Sulfonylureas) for effective treatment, but with several adverse secondary effects, most of them related to the low specificity of these compounds to the target. In this context, the search for specific and high-affinity compounds for the management of this metabolic disease is growing. Toxins isolated from animal venom have high specificity and affinity for different molecular targets, of which the most important are ion channels. This review will present an overview about the electrical activity of the ion channels present in pancreatic β cells that are involved in the insulin secretion process, in addition to the diversity of peptides that can interact and modulate the electrical activity of pancreatic β cells. The importance of prospecting bioactive peptides for therapeutic use is also reinforced.
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Affiliation(s)
- Beatriz Elena Sarmiento
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
| | - Luis Felipe Santos Menezes
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
| | - Elisabeth F Schwartz
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
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11
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Liu Y, LoCaste CE, Liu W, Poltash ML, Russell DH, Laganowsky A. Selective binding of a toxin and phosphatidylinositides to a mammalian potassium channel. Nat Commun 2019; 10:1352. [PMID: 30902995 PMCID: PMC6430785 DOI: 10.1038/s41467-019-09333-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 03/05/2019] [Indexed: 02/05/2023] Open
Abstract
G-protein-gated inward rectifying potassium channels (GIRKs) require Gβγ subunits and phosphorylated phosphatidylinositides (PIPs) for gating. Although studies have provided insight into these interactions, the mechanism of how these events are modulated by Gβγ and the binding affinity between PIPs and GIRKs remains poorly understood. Here, native ion mobility mass spectrometry is employed to directly monitor small molecule binding events to mouse GIRK2. GIRK2 binds the toxin tertiapin Q and PIPs selectively and with significantly higher affinity than other phospholipids. A mutation in GIRK2 that causes a rotation in the cytoplasmic domain, similarly to Gβγ-binding to the wild-type channel, revealed differences in the selectivity towards PIPs. More specifically, PIP isoforms known to weakly activate GIRKs have decreased binding affinity. Taken together, our results reveal selective small molecule binding and uncover a mechanism by which rotation of the cytoplasmic domain can modulate GIRK•PIP interactions.
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Affiliation(s)
- Yang Liu
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX, 77030, USA
| | - Catherine E LoCaste
- Department of Chemistry, Texas A&M University, College Station, TX, 77842, USA
| | - Wen Liu
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX, 77030, USA
| | - Michael L Poltash
- Department of Chemistry, Texas A&M University, College Station, TX, 77842, USA
| | - David H Russell
- Department of Chemistry, Texas A&M University, College Station, TX, 77842, USA
| | - Arthur Laganowsky
- Department of Chemistry, Texas A&M University, College Station, TX, 77842, USA.
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12
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Meng XY, Kang SG, Zhou R. Molecular mechanism of phosphoinositides' specificity for the inwardly rectifying potassium channel Kir2.2. Chem Sci 2018; 9:8352-8362. [PMID: 30542582 PMCID: PMC6247517 DOI: 10.1039/c8sc01284a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 09/04/2018] [Indexed: 12/04/2022] Open
Abstract
We investigated the binding mechanism of PI(4,5)P2 and variants on the inwardly rectifying potassium channel, Kir2.2. Our results not only demonstrated the molecular origin for their binding specificity, but also revealed the major driving forces.
Phosphoinositides are essential signaling lipids that play a critical role in regulating ion channels, and their dysregulation often results in fatal diseases including cardiac arrhythmia and paralysis. Despite decades of intensive research, the underlying molecular mechanism of lipid agonism and specificity remains largely unknown. Here, we present a systematic study of the binding mechanism and specificity of a native agonist, phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and two of its variants, PI(3,4)P2 and PI(3,4,5)P3, on inwardly rectifying potassium channel Kir2.2, using molecular dynamics simulations and free energy perturbations (FEPs). Our results demonstrate that the major driving force for the PI(4,5)P2 specificity on Kir2.2 comes from the highly organized salt-bridge network formed between the charged inositol head and phosphodiester linker of PI(4,5)P2. The unsaturated arachidonic chain is also shown to contribute to the stable binding through hydrophobic interactions with nearby Kir2.2 hydrophobic residues. Consistent with previous experimental findings, our FEP results confirmed that non-native ligands, PI(3,4)P2 and PI(3,4,5)P3, show significant loss in binding affinity as a result of the substantial shift from the native binding mode and unfavorable local solvation environment. However, surprisingly, the underlying molecular pictures for the unfavorable binding of both ligands are quite distinctive: for PI(3,4)P2, it is due to a direct destabilization in the bound state, whereas for PI(3,4,5)P3, it is due to a relative stabilization in its free state. Our findings not only provide a theoretical basis for the ligand specificity, but also generate new insights into the allosteric modulation of ligand-gated ion channels.
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Affiliation(s)
- Xuan-Yu Meng
- State Key Laboratory of Radiation Medicine and Protection , School for Radiological and Interdisciplinary Sciences (RAD-X) , Collaborative Innovation Centre of Radiation Medicine of Jiangsu Higher Education Institutions , Soochow University , Suzhou 215123 , China
| | - Seung-Gu Kang
- IBM Thomas J. Watson Research Center , Yorktown Heights , NY 10598 , USA .
| | - Ruhong Zhou
- State Key Laboratory of Radiation Medicine and Protection , School for Radiological and Interdisciplinary Sciences (RAD-X) , Collaborative Innovation Centre of Radiation Medicine of Jiangsu Higher Education Institutions , Soochow University , Suzhou 215123 , China.,IBM Thomas J. Watson Research Center , Yorktown Heights , NY 10598 , USA . .,Department of Chemistry , Columbia University , New York , NY 10027 , USA
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13
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Trezza A, Cicaloni V, Porciatti P, Langella A, Fusi F, Saponara S, Spiga O. From in silico to in vitro: a trip to reveal flavonoid binding on the Rattus norvegicus Kir6.1 ATP-sensitive inward rectifier potassium channel. PeerJ 2018; 6:e4680. [PMID: 29736333 PMCID: PMC5936070 DOI: 10.7717/peerj.4680] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 04/09/2018] [Indexed: 12/18/2022] Open
Abstract
Background ATP-sensitive inward rectifier potassium channels (Kir), are a potassium channel family involved in many physiological processes. KATP dysfunctions are observed in several diseases such as hypoglycaemia, hyperinsulinemia, Prinzmetal angina–like symptoms, cardiovascular diseases. Methods A broader view of the KATP mechanism is needed in order to operate on their regulation, and in this work we clarify the structure of the Rattus norvegicus ATP-sensitive inward rectifier potassium channel 8 (Kir6.1), which has been obtained through a homology modelling procedure. Due to the medical use of flavonoids, a considerable increase in studies on their influence on human health has recently been observed, therefore our aim is to study, through computational methods, the three-dimensional (3D) conformation together with mechanism of action of Kir6.1 with three flavonoids. Results Computational analysis by performing molecular dynamics (MD) and docking simulation on rat 3D modelled structure have been completed, in its closed and open conformation state and in complex with Quercetin, 5-Hydroxyflavone and Rutin flavonoids. Our study showed that only Quercetin and 5-Hydroxyflavone were responsible for a significant down-regulation of the Kir6.1 activity, stabilising it in a closed conformation. This hypothesis was supported by in vitro experiments demonstrating that Quercetin and 5-Hydroxyflavone were capable to inhibit KATP currents of rat tail main artery myocytes recorded by the patch-clamp technique. Conclusion Combined methodological approaches, such as molecular modelling, docking and MD simulations of Kir6.1 channel, used to elucidate flavonoids intrinsic mechanism of action, are introduced, revealing a new potential druggable protein site.
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Affiliation(s)
- Alfonso Trezza
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - Vittoria Cicaloni
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy.,Toscana Life Sciences Foundation, Siena, Italy
| | - Piera Porciatti
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - Andrea Langella
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - Fabio Fusi
- Department of Life Sciences, University of Siena, Siena, Italy
| | - Simona Saponara
- Department of Life Sciences, University of Siena, Siena, Italy
| | - Ottavia Spiga
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
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14
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Šimurda J, Šimurdová M, Bébarová M. Inward rectifying potassium currents resolved into components: modeling of complex drug actions. Pflugers Arch 2017; 470:315-325. [DOI: 10.1007/s00424-017-2071-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 09/12/2017] [Accepted: 09/18/2017] [Indexed: 10/18/2022]
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15
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Manicam C, Ginter N, Li H, Xia N, Goloborodko E, Zadeh JK, Musayeva A, Pfeiffer N, Gericke A. Compensatory Vasodilator Mechanisms in the Ophthalmic Artery of Endothelial Nitric Oxide Synthase Gene Knockout Mice. Sci Rep 2017; 7:7111. [PMID: 28769073 PMCID: PMC5541003 DOI: 10.1038/s41598-017-07768-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 06/29/2017] [Indexed: 01/02/2023] Open
Abstract
Nitric oxide (NO) generated by endothelial nitric oxide synthase (eNOS) plays an important role in the maintenance of ocular vascular homeostasis. Therefore, perturbations in vascular NO synthesis have been implicated in the pathogenesis of several ocular diseases. We recently reported that eNOS contributes significantly to vasodilation of the mouse ophthalmic artery. Interestingly, dilatory responses were also retained in eNOS gene-deficient mice (eNOS-/-), indicating inherent endothelial adaptive mechanism(s) that act as back-up systems in chronic absence of eNOS to preserve vasorelaxation. Thus, this study endeavoured to identify the compensatory mechanism(s) in the ophthalmic artery of eNOS-/- mice employing isolated arterial segments and pharmacological inhibitors in vitro. Endothelium removal virtually abolished acetylcholine (ACh)-induced vasodilation, suggesting an obligatory involvement of the endothelium in cholinergic control of vascular tone. However, non-NOS and non-cyclooxygenase components compensate for eNOS deficiency via endothelium-derived hyperpolarizing factors (EDHFs). Notably, arachidonic acid-derived metabolites of the 12-lipoxygenase pathway were key mediators in activating the inwardly rectifying potassium channels to compensate for chronic lack of eNOS. Conclusively, endothelium-dependent cholinergic responses of the ophthalmic artery in the eNOS-/- mice are largely preserved and, this vascular bed has the ability to compensate for the loss of normal vasodilator responses solely via EDHFs.
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Affiliation(s)
- Caroline Manicam
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany.
| | - Natalja Ginter
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Huige Li
- Institute of Pharmacology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Ning Xia
- Institute of Pharmacology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Evgeny Goloborodko
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Jenia Kouchek Zadeh
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Aytan Musayeva
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Norbert Pfeiffer
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Adrian Gericke
- Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, Mainz, Germany
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16
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Wang S, Borschel WF, Heyman S, Hsu P, Nichols CG. Conformational changes at cytoplasmic intersubunit interactions control Kir channel gating. J Biol Chem 2017; 292:10087-10096. [PMID: 28446610 DOI: 10.1074/jbc.m117.785154] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 04/17/2017] [Indexed: 02/02/2023] Open
Abstract
The defining structural feature of inward-rectifier potassium (Kir) channels is the unique Kir cytoplasmic domain. Recently we showed that salt bridges located at the cytoplasmic domain subunit interfaces (CD-Is) of eukaryotic Kir channels control channel gating via stability of a novel inactivated closed state. The cytoplasmic domains of prokaryotic and eukaryotic Kir channels show similar conformational rearrangements to the common gating ligand, phosphatidylinositol bisphosphate (PIP2), although these exhibit opposite coupling to opening and closing transitions. In Kir2.1, mutation of one of these CD-I salt bridge residues (R204A) reduces apparent PIP2 sensitivity of channel activity, and here we show that Ala or Cys substitutions of the functionally equivalent residue (Arg-165) in the prokaryotic Kir channel KirBac1.1 also significantly decrease sensitivity of the channel to PIP2 (by 5-30-fold). To further understand the structural basis of CD-I control of Kir channel gating, we examined the effect of the R165A mutation on PIP2-induced changes in channel function and conformation. Single-channel analyses indicated that the R165A mutation disrupts the characteristic long interburst closed state of reconstituted KirBac1.1 in giant liposomes, resulting in a higher open probability due to more frequent opening bursts. Intramolecular FRET measurements indicate that, relative to wild-type channels, the R165A mutation results in splaying of the cytoplasmic domains away from the central axis and that PIP2 essentially induces opposite motions of the major β-sheet in this channel mutant. We conclude that the removal of stabilizing CD-I salt bridges results in a collapsed state of the Kir domain.
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Affiliation(s)
- Shizhen Wang
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - William F Borschel
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Sarah Heyman
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Phillip Hsu
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Colin G Nichols
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
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17
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Synergistic activation of G protein-gated inwardly rectifying potassium channels by cholesterol and PI(4,5)P 2. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1233-1241. [PMID: 28377218 DOI: 10.1016/j.bbamem.2017.03.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 03/16/2017] [Accepted: 03/31/2017] [Indexed: 11/23/2022]
Abstract
G-protein gated inwardly rectifying potassium (GIRK or Kir3) channels play a major role in the control of the heart rate, and require the membrane phospholipid phosphatidylinositol-bis-phosphate (PI(4,5)P2) for activation. Recently, we have shown that the activity of the heterotetrameric Kir3.1/Kir3.4 channel that underlies atrial KACh currents was enhanced by cholesterol. Similarly, the activities of both the Kir3.4 homomer and its active pore mutant Kir3.4* (Kir3.4_S143T) were also enhanced by cholesterol. Here we employ planar lipid bilayers to investigate the crosstalk between PI(4,5)P2 and cholesterol, and demonstrate that these two lipids act synergistically to activate Kir3.4* currents. Further studies using the Xenopus oocytes heterologous expression system suggest that PI(4,5)P2 and cholesterol act via distinct binding sites. Whereas PI(4,5)P2 binds to the cytosolic domain of the channel, the putative binding region of cholesterol is located at the center of the transmembrane domain overlapping the central glycine hinge region of the channel. Together, our data suggest that changes in the levels of two key membrane lipids - cholesterol and PI(4,5)P2 - could act in concert to provide fine-tuning of Kir3 channel function.
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18
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Structural Basis for Differences in Dynamics Induced by Leu Versus Ile Residues in the CD Loop of Kir Channels. Mol Neurobiol 2016; 53:5948-5961. [PMID: 26520451 PMCID: PMC5085999 DOI: 10.1007/s12035-015-9466-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2015] [Accepted: 09/28/2015] [Indexed: 12/22/2022]
Abstract
The effect of the conserved Leu/Ile site in the CD loop on the gating dynamics of Kir channels and corresponding micro-structural mechanism remains unclear. Molecular dynamics simulations were performed to investigate the structural mechanism of chicken Kir2.2. Compared to WT, the I223L mutant channel bound to PIP2 more strongly, was activated more rapidly, and maintained the activation state more stably after PIP2 dissociation. Cellular electrophysiology assays of mouse Kir2.1 and human Kir2.2 indicated that, consistent with simulations, the Leu residue increased the channel responses to PIP2 through increased binding affinity and faster activation kinetics, and the deactivation kinetics decreased upon PIP2 inhibition. The Ile residue induced the opposite responses. This difference was attributed to the distinct hydrophobic side chain symmetries of Leu and Ile; switching between these residues caused the interaction network to redistribute and offered effective conformation transduction in the Leu systems, which had more rigid and independent subunits.
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19
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Li J, Xiao S, Xie X, Zhou H, Pang C, Li S, Zhang H, Logothetis DE, Zhan Y, An H. Three pairs of weak interactions precisely regulate the G-loop gate of Kir2.1 channel. Proteins 2016; 84:1929-1937. [PMID: 27699887 DOI: 10.1002/prot.25176] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 06/30/2016] [Accepted: 09/19/2016] [Indexed: 11/08/2022]
Abstract
Kir2.1 (also known as IRK1) plays key roles in regulation of resting membrane potential and cell excitability. To achieve its physiological roles, Kir2.1 performs a series of conformational transition, named as gating. However, the structural basis of gating is still obscure. Here, we combined site-directed mutation, two-electrode voltage clamp with molecular dynamics simulations and determined that H221 regulates the gating process of Kir2.1 by involving a weak interaction network. Our data show that the H221R mutant accelerates the rundown kinetics and decelerates the reactivation kinetics of Kir2.1. Compared with the WT channel, the H221R mutation strengthens the interaction between the CD- and G-loops (E303-R221) which stabilizes the close state of the G-loop gate and weakens the interactions between C-linker and CD-loop (R221-R189) and the adjacent G-loops (E303-R312) which destabilizes the open state of G-loop gate. Our data indicate that the three pairs of interactions (E303-H221, H221-R189 and E303-R312) precisely regulate the G-loop gate by controlling the conformation of G-loop. Proteins 2016; 84:1929-1937. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Junwei Li
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, 300401, China.,Department of Electrical Engineering and Computer Science, Hebei University of Technology, Langfang, 065000, China
| | - Shaoying Xiao
- Department of Urban Planning, School of Architecture and Art Design, Hebei University of Technology, Tianjin, 300401, China
| | - Xiaoxiao Xie
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, 300401, China
| | - Hui Zhou
- Department of Mathematics and Physics, North China Electric Power University, Baoding, 071003, China
| | - Chunli Pang
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, 300401, China
| | - Shanshan Li
- Department of Mechatronics Engineering, Hebei University of Technology, Tianjin, 300130, China
| | - Hailin Zhang
- Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of Pharmacology and Toxicology for New Drug, Hebei Province, Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050017, China
| | - Diomedes E Logothetis
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, 23298
| | - Yong Zhan
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, 300401, China
| | - Hailong An
- Key Laboratory of Molecular Biophysics, Hebei Province, Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, 300401, China
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20
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Velasco M, Díaz-García CM, Larqué C, Hiriart M. Modulation of Ionic Channels and Insulin Secretion by Drugs and Hormones in Pancreatic Beta Cells. Mol Pharmacol 2016; 90:341-57. [PMID: 27436126 DOI: 10.1124/mol.116.103861] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 07/18/2016] [Indexed: 12/11/2022] Open
Abstract
Pancreatic beta cells, unique cells that secrete insulin in response to an increase in glucose levels, play a significant role in glucose homeostasis. Glucose-stimulated insulin secretion (GSIS) in pancreatic beta cells has been extensively explored. In this mechanism, glucose enters the cells and subsequently the metabolic cycle. During this process, the ATP/ADP ratio increases, leading to ATP-sensitive potassium (KATP) channel closure, which initiates depolarization that is also dependent on the activity of TRP nonselective ion channels. Depolarization leads to the opening of voltage-gated Na(+) channels (Nav) and subsequently voltage-dependent Ca(2+) channels (Cav). The increase in intracellular Ca(2+) triggers the exocytosis of insulin-containing vesicles. Thus, electrical activity of pancreatic beta cells plays a central role in GSIS. Moreover, many growth factors, incretins, neurotransmitters, and hormones can modulate GSIS, and the channels that participate in GSIS are highly regulated. In this review, we focus on the principal ionic channels (KATP, Nav, and Cav channels) involved in GSIS and how classic and new proteins, hormones, and drugs regulate it. Moreover, we also discuss advances on how metabolic disorders such as metabolic syndrome and diabetes mellitus change channel activity leading to changes in insulin secretion.
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Affiliation(s)
- Myrian Velasco
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Carlos Manlio Díaz-García
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Carlos Larqué
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Marcia Hiriart
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
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21
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Lee CH, Huang PT, Liou HH, Lin MY, Lou KL, Chen CY. Non-basic amino acids in the ROMK1 channels via an appropriate distance modulate PIP2 regulated pHi-gating. Biochem Biophys Res Commun 2016; 473:303-310. [PMID: 27016482 DOI: 10.1016/j.bbrc.2016.03.100] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2016] [Accepted: 03/21/2016] [Indexed: 12/11/2022]
Abstract
The ROMK1 (Kir1.1) channel activity is predominantly regulated by intracellular pH (pHi) and phosphatidylinositol 4,5-bisphosphate (PIP2). Although several residues were reported to be involved in the regulation of pHi associated with PIP2 interaction, the detailed molecular mechanism remains unclear. We perform experiments in ROMK1 pHi-gating with electrophysiology combined with mutational and structural analysis. In the present study, non basic residues of C-terminal region (S219, N215, I192, L216 and L220) in ROMK1 channels have been found to mediate channel-PIP2 interaction and pHi gating. Further, our structural results show these residues with an appropriate distance to interact with membrane PIP2. Meanwhile, a cluster of basic residues (R188, R217 and K218), which was previously discovered regarding the interaction with PIP2, exists in this appropriate distance to discriminate the regulation of channel-PIP2 interaction and pHi-gating. This appropriate distance can be observed with high conservation in the Kir channel family. Our results provide insight that an appropriate distance cooperates with the electrostatics interaction of channel-PIP2 to regulate pHi-gating.
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Affiliation(s)
- Chien-Hsing Lee
- Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, 10051, Taiwan; Department of Nursing, Min-Hwei Junior College of Health Care Management, Tainan, 73658, Taiwan
| | - Po-Tsang Huang
- Institutes of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei, 10051, Taiwan; Graduate Institutes of Oral Biology, Medical College, National Taiwan University, Taipei, 10048, Taiwan
| | - Horng-Huei Liou
- Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, 10051, Taiwan; Divisions of Neurology, National Taiwan University Hospital, Taipei, 10002, Taiwan
| | - Mei-Ying Lin
- Cancer Center, Kaohsiung Medical University Hospital, Kaohsiung, 80708, Taiwan
| | - Kuo-Long Lou
- Institutes of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei, 10051, Taiwan; Graduate Institutes of Oral Biology, Medical College, National Taiwan University, Taipei, 10048, Taiwan; NTU-DRCP Lectures and Core for Membrane Proteins, Center for Biotechnology, National Taiwan University, Taipei, 10672, Taiwan.
| | - Chung-Yi Chen
- School of Medical and Health Sciences, Fooyin University, No.151, Jinxue Rd., Daliao Dist., Kaohsiung City, 83102, Taiwan.
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22
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The ICl,swell inhibitor DCPIB blocks Kir channels that possess weak affinity for PIP2. Pflugers Arch 2016; 468:817-24. [PMID: 26837888 DOI: 10.1007/s00424-016-1794-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 01/17/2016] [Accepted: 01/20/2016] [Indexed: 12/15/2022]
Abstract
Inwardly rectifying K(+) (Kir) channels are important contributors to the resting membrane potential and regulate cellular excitability. The activity of Kir channels depends critically on the phospholipid PIP2. Several modulators of the activity of Kir channels alter the apparent affinity of the channel to PIP2. Channels with high apparent affinity to PIP2 may not respond to a given modulator, but mutations that decrease such affinity can render the channel susceptible to modulation. Here, we identify a known inhibitor of the swelling-activated Cl(-) current, DCPIB, as an effective inhibitor of a number of Kir channels both in native cardiac cells and in heterologous expression systems. We show that the apparent affinity to PIP2 determines whether DCPIB will serve as an efficient blocker of Kir channels. These effects are consistent with a model in which DCPIB competes with PIP2 for a common binding site.
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23
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Ufret-Vincenty CA, Klein RM, Collins MD, Rosasco MG, Martinez GQ, Gordon SE. Mechanism for phosphoinositide selectivity and activation of TRPV1 ion channels. ACTA ACUST UNITED AC 2016; 145:431-42. [PMID: 25918361 PMCID: PMC4411251 DOI: 10.1085/jgp.201511354] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Phosphoinositides bind to a selective site in the proximal C-terminal region to regulate TRPV1. Although PI(4,5)P2 is believed to play an essential role in regulating the activity of numerous ion channels and transporters, the mechanisms by which it does so are unknown. Here, we used the ability of the TRPV1 ion channel to discriminate between PI(4,5)P2 and PI(4)P to localize the region of TRPV1 sequence that interacts directly with the phosphoinositide. We identified a point mutation in the proximal C-terminal region after the TRP box, R721A, that inverted the selectivity of TRPV1. Although the R721A mutation produced only a 30% increase in the EC50 for activation by PI(4,5)P2, it decreased the EC50 for activation by PI(4)P by more than two orders of magnitude. We used chemically induced and voltage-activated phosphatases to determine that PI(4)P continued to support TRPV1 activity even after depletion of PI(4,5)P2 from the plasma membrane. Our data cannot be explained by a purely electrostatic mechanism for interaction between the phosphoinositide and the protein, similar to that of the MARCKS (myristoylated alanine-rich C kinase substrate) effector domain or the EGF receptor. Rather, conversion of a PI(4,5)P2-selective channel to a PI(4)P-selective channel indicates that a structured phosphoinositide-binding site mediates the regulation of TRPV1 activity and that the amino acid at position 721 likely interacts directly with the moiety at the 5′ position of the phosphoinositide.
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Affiliation(s)
| | - Rebecca M Klein
- University of Washington School of Medicine, Seattle, WA 98195
| | | | - Mario G Rosasco
- University of Washington School of Medicine, Seattle, WA 98195
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Wang S, Vafabakhsh R, Borschel WF, Ha T, Nichols CG. Structural dynamics of potassium-channel gating revealed by single-molecule FRET. Nat Struct Mol Biol 2015; 23:31-36. [PMID: 26641713 PMCID: PMC4833211 DOI: 10.1038/nsmb.3138] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 11/06/2015] [Indexed: 01/06/2023]
Abstract
Crystallography has provided invaluable insights to ion channel selectivity and gating, but to advance understanding to a new level, dynamic views of channel structures within membranes are essential. We labeled tetrameric KirBac1.1 potassium channels with single donor and acceptor fluorophores at different sites, and examined structural dynamics within lipid membranes by single molecule FRET. We found that the extracellular region is structurally rigid in both closed and open states, whereas the N-terminal slide helix undergoes marked conformational fluctuations. The cytoplasmic C-terminal domain fluctuates between two major structural states both of which become less dynamic and move away from the pore axis and away from the membrane in closed channels. Our results reveal mobile and rigid conformations of functionally relevant KirBac1.1 channel motifs, implying similar dynamics for similar motifs in eukaryotic Kir channels and for cation channels in general.
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Affiliation(s)
- Shizhen Wang
- Center for Investigation of Membrane Excitability Diseases, Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis MO
| | - Reza Vafabakhsh
- Department of Physics and the Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL
| | - William F Borschel
- Center for Investigation of Membrane Excitability Diseases, Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis MO
| | - Taekjip Ha
- Department of Physics and the Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL.,Howard Hughes Medical Institute, Baltimore, MD.,Department of Biophysics and Biophysical Chemistry, Department of Biophysics, Department of Biomedical Engineering, Baltimore, MD
| | - Colin G Nichols
- Center for Investigation of Membrane Excitability Diseases, Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis MO
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Identification of the Conformational transition pathway in PIP2 Opening Kir Channels. Sci Rep 2015; 5:11289. [PMID: 26063437 PMCID: PMC4462750 DOI: 10.1038/srep11289] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 04/29/2015] [Indexed: 11/08/2022] Open
Abstract
The gating of Kir channels depends critically on phosphatidylinositol 4,5-bisphosphate (PIP2), but the detailed mechanism by which PIP2 regulates Kir channels remains obscure. Here, we performed a series of Targeted molecular dynamics simulations on the full-length Kir2.1 channel and, for the first time, were able to achieve the transition from the closed to the open state. Our data show that with the upward motion of the cytoplasmic domain (CTD) the structure of the C-Linker changes from a loop to a helix. The twisting of the C-linker triggers the rotation of the CTD, which induces a small downward movement of the CTD and an upward motion of the slide helix toward the membrane that pulls the inner helix gate open. At the same time, the rotation of the CTD breaks the interaction between the CD- and G-loops thus releasing the G-loop. The G-loop then bounces away from the CD-loop, which leads to the opening of the G-loop gate and the full opening of the pore. We identified a series of interaction networks, between the N-terminus, CD loop, C linker and G loop one by one, which exquisitely regulates the global conformational changes during the opening of Kir channels by PIP2.
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Hansen SB. Lipid agonism: The PIP2 paradigm of ligand-gated ion channels. BIOCHIMICA ET BIOPHYSICA ACTA 2015; 1851:620-8. [PMID: 25633344 PMCID: PMC4540326 DOI: 10.1016/j.bbalip.2015.01.011] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 01/05/2015] [Accepted: 01/17/2015] [Indexed: 01/08/2023]
Abstract
The past decade, membrane signaling lipids emerged as major regulators of ion channel function. However, the molecular nature of lipid binding to ion channels remained poorly described due to a lack of structural information and assays to quantify and measure lipid binding in a membrane. How does a lipid-ligand bind to a membrane protein in the plasma membrane, and what does it mean for a lipid to activate or regulate an ion channel? How does lipid binding compare to activation by soluble neurotransmitter? And how does the cell control lipid agonism? This review focuses on lipids and their interactions with membrane proteins, in particular, ion channels. I discuss the intersection of membrane lipid biology and ion channel biophysics. A picture emerges of membrane lipids as bona fide agonists of ligand-gated ion channels. These freely diffusing signals reside in the plasma membrane, bind to the transmembrane domain of protein, and cause a conformational change that allosterically gates an ion channel. The system employs a catalog of diverse signaling lipids ultimately controlled by lipid enzymes and raft localization. I draw upon pharmacology, recent protein structure, and electrophysiological data to understand lipid regulation and define inward rectifying potassium channels (Kir) as a new class of PIP2 lipid-gated ion channels.
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Affiliation(s)
- Scott B Hansen
- Department of Molecular Therapeutics, The Scripps Research Institute, Jupiter FL 33458, USA; Department of Neuroscience, The Scripps Research Institute, Jupiter FL 33458, USA.
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Sepúlveda FV, Pablo Cid L, Teulon J, Niemeyer MI. Molecular aspects of structure, gating, and physiology of pH-sensitive background K2P and Kir K+-transport channels. Physiol Rev 2015; 95:179-217. [PMID: 25540142 DOI: 10.1152/physrev.00016.2014] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
K(+) channels fulfill roles spanning from the control of excitability to the regulation of transepithelial transport. Here we review two groups of K(+) channels, pH-regulated K2P channels and the transport group of Kir channels. After considering advances in the molecular aspects of their gating based on structural and functional studies, we examine their participation in certain chosen physiological and pathophysiological scenarios. Crystal structures of K2P and Kir channels reveal rather unique features with important consequences for the gating mechanisms. Important tasks of these channels are discussed in kidney physiology and disease, K(+) homeostasis in the brain by Kir channel-equipped glia, and central functions in the hearing mechanism in the inner ear and in acid secretion by parietal cells in the stomach. K2P channels fulfill a crucial part in central chemoreception probably by virtue of their pH sensitivity and are central to adrenal secretion of aldosterone. Finally, some unorthodox behaviors of the selectivity filters of K2P channels might explain their normal and pathological functions. Although a great deal has been learned about structure, molecular details of gating, and physiological functions of K2P and Kir K(+)-transport channels, this has been only scratching at the surface. More molecular and animal studies are clearly needed to deepen our knowledge.
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Affiliation(s)
- Francisco V Sepúlveda
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - L Pablo Cid
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - Jacques Teulon
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - María Isabel Niemeyer
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
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28
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Bose T, Cieślar-Pobuda A, Wiechec E. Role of ion channels in regulating Ca²⁺ homeostasis during the interplay between immune and cancer cells. Cell Death Dis 2015; 6:e1648. [PMID: 25695601 PMCID: PMC4669790 DOI: 10.1038/cddis.2015.23] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 12/23/2014] [Accepted: 01/06/2015] [Indexed: 01/08/2023]
Abstract
Ion channels are abundantly expressed in both excitable and non-excitable cells, thereby regulating the Ca2+ influx and downstream signaling pathways of physiological processes. The immune system is specialized in the process of cancer cell recognition and elimination, and is regulated by different ion channels. In comparison with the immune cells, ion channels behave differently in cancer cells by making the tumor cells more hyperpolarized and influence cancer cell proliferation and metastasis. Therefore, ion channels comprise an important therapeutic target in anti-cancer treatment. In this review, we discuss the implication of ion channels in regulation of Ca2+ homeostasis during the crosstalk between immune and cancer cell as well as their role in cancer progression.
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Affiliation(s)
- T Bose
- Leibniz-Institute of Neurobiology, Brenneckestrasse 6, D-39 Magdeburg, Germany
| | - A Cieślar-Pobuda
- 1] Department of Clinical and Experimental Medicine, Division of Cell Biology & Integrative Regenerative Medicine Center (IGEN), Linköping University, 581 85 Linköping, Sweden [2] Biosystems Group, Institute of Automatic Control, Silesian University of Technology, Akademicka 16, 44-100 Gliwice, Poland
| | - E Wiechec
- Department of Clinical and Experimental Medicine, Division of Cell Biology & Integrative Regenerative Medicine Center (IGEN), Linköping University, 581 85 Linköping, Sweden
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29
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Logothetis DE, Petrou VI, Zhang M, Mahajan R, Meng XY, Adney SK, Cui M, Baki L. Phosphoinositide control of membrane protein function: a frontier led by studies on ion channels. Annu Rev Physiol 2014; 77:81-104. [PMID: 25293526 DOI: 10.1146/annurev-physiol-021113-170358] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Anionic phospholipids are critical constituents of the inner leaflet of the plasma membrane, ensuring appropriate membrane topology of transmembrane proteins. Additionally, in eukaryotes, the negatively charged phosphoinositides serve as key signals not only through their hydrolysis products but also through direct control of transmembrane protein function. Direct phosphoinositide control of the activity of ion channels and transporters has been the most convincing case of the critical importance of phospholipid-protein interactions in the functional control of membrane proteins. Furthermore, second messengers, such as [Ca(2+)]i, or posttranslational modifications, such as phosphorylation, can directly or allosterically fine-tune phospholipid-protein interactions and modulate activity. Recent advances in structure determination of membrane proteins have allowed investigators to obtain complexes of ion channels with phosphoinositides and to use computational and experimental approaches to probe the dynamic mechanisms by which lipid-protein interactions control active and inactive protein states.
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Affiliation(s)
- Diomedes E Logothetis
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298-0551;
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Abstract
The field of mitochondrial ion channels has recently seen substantial progress, including the molecular identification of some of the channels. An integrative approach using genetics, electrophysiology, pharmacology, and cell biology to clarify the roles of these channels has thus become possible. It is by now clear that many of these channels are important for energy supply by the mitochondria and have a major impact on the fate of the entire cell as well. The purpose of this review is to provide an up-to-date overview of the electrophysiological properties, molecular identity, and pathophysiological functions of the mitochondrial ion channels studied so far and to highlight possible therapeutic perspectives based on current information.
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Mitsuyama H, Yokoshiki H, Irie Y, Watanabe M, Mizukami K, Tsutsui H. Involvement of the phosphatidylinositol kinase pathway in augmentation of ATP-sensitive K+ channel currents by hypo-osmotic stress in rat ventricular myocytes. Can J Physiol Pharmacol 2013; 91:686-92. [DOI: 10.1139/cjpp-2012-0408] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objective of this study was to investigate the mechanisms of increase in the efficacy of ATP-sensitive K+ channel (KATP) openings by hypo-osmotic stress. The whole-cell KATP currents (IK,ATP) stimulated by 100 μmol/L pinacidil, a K+ channel opening drug, were significantly augmented during hypo-osmotic stress (189 mOsmol/L) compared with normal conditions (303 mOsmol/L). The EC50 and Emax value for pinacidil-activated IK,ATP (measured at 0 mV) was 154 μmol/L and 844 pA, respectively, in normal solution and 16.6 μmol/L and 1266 pA, respectively, in hypo-osmotic solution. Augmentation of IK,ATP during hypo-osmotic stress was attenuated by wortmannin (50 μmol/L), an inhibitor of phosphatidylinositol 3- and 4-kinases, but not by (i) phalloidin (30 μmol/L), an actin filament stabilizer, (ii) the absence of Ca2+ from the internal and external solutions, and (iii) the presence of creatine phosphate (3 mmol/L), which affects creatine kinase regulation of the KATP channels. In the single-channel recordings, an inside-out patch was made after approximately 5 min exposure of the myocyte to hypo-osmotic solution. However, the IC50 value for ATP under such conditions was not different from that obtained in normal osmotic solution. In conclusion, hypo-osmotic stress could augment cardiac IK,ATP through intracellular mechanisms involving the phosphatidylinositol kinase pathway.
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Affiliation(s)
- Hirofumi Mitsuyama
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
| | - Hisashi Yokoshiki
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
| | - Yuki Irie
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
| | - Masaya Watanabe
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
| | - Kazuya Mizukami
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
| | - Hiroyuki Tsutsui
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
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Takeda I, Takahashi T, Ueno H, Morino H, Ochi K, Nakamura T, Hosomi N, Kawakami H, Hashimoto K, Matsumoto M. Autosomal recessive Andersen-Tawil syndrome with a novel mutation L94P in Kir2.1. ACTA ACUST UNITED AC 2013. [DOI: 10.1111/ncn3.38] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ikuko Takeda
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Tetsuya Takahashi
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Hiroki Ueno
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Hiroyuki Morino
- Department of Epidemiology; Research Institute for Radiation Biology and Medicine; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Kazuhide Ochi
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Takeshi Nakamura
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Naohisa Hosomi
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Hideshi Kawakami
- Department of Epidemiology; Research Institute for Radiation Biology and Medicine; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Kouichi Hashimoto
- Department of Neurophysiology; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
| | - Masayasu Matsumoto
- Department of Clinical Neuroscience and Therapeutics; Hiroshima University; Graduate School of Biomedical and Health Sciences; Hiroshima; Japan
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Bushman JD, Zhou Q, Shyng SL. A Kir6.2 pore mutation causes inactivation of ATP-sensitive potassium channels by disrupting PIP2-dependent gating. PLoS One 2013; 8:e63733. [PMID: 23700433 PMCID: PMC3659044 DOI: 10.1371/journal.pone.0063733] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 04/05/2013] [Indexed: 11/18/2022] Open
Abstract
In the absence of intracellular nucleotides, ATP-sensitive potassium (KATP) channels exhibit spontaneous activity via a phosphatidylinositol-4,5-bisphosphate (PIP2)-dependent gating process. Previous studies show that stability of this activity requires subunit-subunit interactions in the cytoplasmic domain of Kir6.2; selective mutagenesis and disease mutations at the subunit interface result in time-dependent channel inactivation. Here, we report that mutation of the central glycine in the pore-lining second transmembrane segment (TM2) to proline in Kir6.2 causes KATP channel inactivation. Unlike C-type inactivation, a consequence of selectivity filter closure, in many K(+) channels, the rate of inactivation in G156P channels was insensitive to changes in extracellular ion concentrations or ion species fluxing through the pore. Instead, the rate of G156P inactivation decreased with exogenous application of PIP2 and increased when PIP2-channel interaction was inhibited with neomycin or poly-L-lysine. These findings indicate the G156P mutation reduces the ability of PIP2 to stabilize the open state of KATP channels, similar to mutations in the cytoplasmic domain that produce inactivation. Consistent with this notion, when PIP2-dependent open state stability was substantially increased by addition of a second gain-of-function mutation, G156P inactivation was abolished. Importantly, bath application and removal of Mg(2+)-free ATP or a nonhydrolyzable analog of ATP, which binds to the cytoplasmic domain of Kir6.2 and causes channel closure, recover G156P channel from inactivation, indicating crosstalk between cytoplasmic and transmembrane domains. The G156P mutation provides mechanistic insight into the structural and functional interactions between the pore and cytoplasmic domains of Kir6.2 during gating.
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Affiliation(s)
- Jeremy D. Bushman
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon, United States of America
| | - Qing Zhou
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon, United States of America
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon, United States of America
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Lee SJ, Wang S, Borschel W, Heyman S, Gyore J, Nichols CG. Secondary anionic phospholipid binding site and gating mechanism in Kir2.1 inward rectifier channels. Nat Commun 2013; 4:2786. [PMID: 24270915 PMCID: PMC3868208 DOI: 10.1038/ncomms3786] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 10/16/2013] [Indexed: 12/03/2022] Open
Abstract
Inwardly rectifying potassium (Kir) channels regulate multiple tissues. All Kir channels require interaction of phosphatidyl-4,5-bisphosphate (PIP2) at a crystallographically identified binding site, but an additional nonspecific secondary anionic phospholipid (PL(-)) is required to generate high PIP2 sensitivity of Kir2 channel gating. The PL(-)-binding site and mechanism are yet to be elucidated. Here we report docking simulations that identify a putative PL(-)-binding site, adjacent to the PIP2-binding site, generated by two lysine residues from neighbouring subunits. When either lysine is mutated to cysteine (K64C and K219C), channel activity is significantly decreased in cells and in reconstituted liposomes. Directly tethering K64C to the membrane by modification with decyl-MTS generates high PIP2 sensitivity in liposomes, even in the complete absence of PL(-)s. The results provide a coherent molecular mechanism whereby PL(-) interaction with a discrete binding site results in a conformational change that stabilizes the high-affinity PIP2 activatory site.
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Affiliation(s)
- Sun-Joo Lee
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Shizhen Wang
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - William Borschel
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Sarah Heyman
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Jacob Gyore
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | - Colin G. Nichols
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Amphipathic antenna of an inward rectifier K+ channel responds to changes in the inner membrane leaflet. Proc Natl Acad Sci U S A 2012; 110:749-54. [PMID: 23267068 DOI: 10.1073/pnas.1217323110] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Membrane lipids modulate the function of membrane proteins. In the case of ion channels, they bias the gating equilibrium, although the underlying mechanism has remained elusive. Here we demonstrate that the N-terminal segment (M0) of the KcsA potassium channel mediates the effect of changes in the lipid milieu on channel gating. The M0 segment is a membrane-anchored amphipathic helix, bearing positively charged residues. In asymmetric membranes, the M0 helix senses the presence of negatively charged phospholipids on the inner leaflet. Upon gating, the M0 helix revolves around the axis of the helix on the membrane surface, inducing the positively charged residues to interact with the negative head groups of the lipids so as to stabilize the open conformation (i.e., the "roll-and-stabilize model"). The M0 helix is thus a charge-sensitive "antenna," capturing temporary changes in lipid composition in the fluidic membrane. This unique type of sensory device may be shared by various types of membrane proteins.
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36
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Kukkonen JP. Physiology of the orexinergic/hypocretinergic system: a revisit in 2012. Am J Physiol Cell Physiol 2012; 304:C2-32. [PMID: 23034387 DOI: 10.1152/ajpcell.00227.2012] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The neuropeptides orexins and their G protein-coupled receptors, OX(1) and OX(2), were discovered in 1998, and since then, their role has been investigated in many functions mediated by the central nervous system, including sleep and wakefulness, appetite/metabolism, stress response, reward/addiction, and analgesia. Orexins also have peripheral actions of less clear physiological significance still. Cellular responses to the orexin receptor activity are highly diverse. The receptors couple to at least three families of heterotrimeric G proteins and other proteins that ultimately regulate entities such as phospholipases and kinases, which impact on neuronal excitation, synaptic plasticity, and cell death. This article is a 10-year update of my previous review on the physiology of the orexinergic/hypocretinergic system. I seek to provide a comprehensive update of orexin physiology that spans from the molecular players in orexin receptor signaling to the systemic responses yet emphasizing the cellular physiological aspects of this system.
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Affiliation(s)
- Jyrki P Kukkonen
- Dept. of Veterinary Biosciences, University of Helsinki, Finland.
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37
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Pattnaik BR, Asuma MP, Spott R, Pillers DAM. Genetic defects in the hotspot of inwardly rectifying K(+) (Kir) channels and their metabolic consequences: a review. Mol Genet Metab 2012; 105:64-72. [PMID: 22079268 PMCID: PMC3253982 DOI: 10.1016/j.ymgme.2011.10.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Revised: 10/11/2011] [Accepted: 10/12/2011] [Indexed: 02/07/2023]
Abstract
Inwardly rectifying potassium (Kir) channels are essential for maintaining normal potassium homeostasis and the resting membrane potential. As a consequence, mutations in Kir channels cause debilitating diseases ranging from cardiac failure to renal, ocular, pancreatic, and neurological abnormalities. Structurally, Kir channels consist of two trans-membrane domains, a pore-forming loop that contains the selectivity filter and two cytoplasmic polar tails. Within the cytoplasmic structure, clusters of amino acid sequences form regulatory domains that interact with cellular metabolites to control the opening and closing of the channel. In this review, we present an overview of Kir channel function and recent progress in the characterization of selected Kir channel mutations that lie in and near a C-terminal cytoplasmic 'hotspot' domain. The resultant molecular mechanisms by which the loss or gain of channel function leads to organ failure provide potential opportunities for targeted therapeutic interventions for this important group of channelopathies.
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Affiliation(s)
- Bikash R. Pattnaik
- Department of Pediatrics, University of Wisconsin, Madison
- Department of Ophthalmology & Visual Sciences, University of Wisconsin, Madison
- Department of Eye Research Institute, University of Wisconsin, Madison
| | - Matti P. Asuma
- Department of Pediatrics, University of Wisconsin, Madison
| | - Ryan Spott
- Department of Pediatrics, University of Wisconsin, Madison
| | - De-Ann M. Pillers
- Department of Pediatrics, University of Wisconsin, Madison
- Department of Eye Research Institute, University of Wisconsin, Madison
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Hansen SB, Tao X, MacKinnon R. Structural basis of PIP2 activation of the classical inward rectifier K+ channel Kir2.2. Nature 2011; 477:495-8. [PMID: 21874019 PMCID: PMC3324908 DOI: 10.1038/nature10370] [Citation(s) in RCA: 466] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Accepted: 07/15/2011] [Indexed: 11/10/2022]
Abstract
The regulation of ion channel activity by specific lipid molecules is widely recognized as an integral component of electrical signalling in cells. In particular, phosphatidylinositol 4,5-bisphosphate (PIP(2)), a minor yet dynamic phospholipid component of cell membranes, is known to regulate many different ion channels. PIP(2) is the primary agonist for classical inward rectifier (Kir2) channels, through which this lipid can regulate a cell's resting membrane potential. However, the molecular mechanism by which PIP(2) exerts its action is unknown. Here we present the X-ray crystal structure of a Kir2.2 channel in complex with a short-chain (dioctanoyl) derivative of PIP(2). We found that PIP(2) binds at an interface between the transmembrane domain (TMD) and the cytoplasmic domain (CTD). The PIP(2)-binding site consists of a conserved non-specific phospholipid-binding region in the TMD and a specific phosphatidylinositol-binding region in the CTD. On PIP(2) binding, a flexible expansion linker contracts to a compact helical structure, the CTD translates 6 Å and becomes tethered to the TMD and the inner helix gate begins to open. In contrast, the small anionic lipid dioctanoyl glycerol pyrophosphatidic acid (PPA) also binds to the non-specific TMD region, but not to the specific phosphatidylinositol region, and thus fails to engage the CTD or open the channel. Our results show how PIP(2) can control the resting membrane potential through a specific ion-channel-receptor-ligand interaction that brings about a large conformational change, analogous to neurotransmitter activation of ion channels at synapses.
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Affiliation(s)
- Scott B Hansen
- Laboratory of Molecular Neurobiology & Biophysics, The Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, New York 10065, USA
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Pratt EB, Tewson P, Bruederle CE, Skach WR, Shyng SL. N-terminal transmembrane domain of SUR1 controls gating of Kir6.2 by modulating channel sensitivity to PIP2. ACTA ACUST UNITED AC 2011; 137:299-314. [PMID: 21321069 PMCID: PMC3047609 DOI: 10.1085/jgp.201010557] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Functional integrity of pancreatic adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channels depends on the interactions between the pore-forming potassium channel subunit Kir6.2 and the regulatory subunit sulfonylurea receptor 1 (SUR1). Previous studies have shown that the N-terminal transmembrane domain of SUR1 (TMD0) interacts with Kir6.2 and is sufficient to confer high intrinsic open probability (P(o)) and bursting patterns of activity observed in full-length K(ATP) channels. However, the nature of TMD0-Kir6.2 interactions that underlie gating modulation is not well understood. Using two previously described disease-causing mutations in TMD0 (R74W and E128K), we performed amino acid substitutions to study the structural roles of these residues in K(ATP) channel function in the context of full-length SUR1 as well as TMD0. Our results revealed that although R74W and E128K in full-length SUR1 both decrease surface channel expression and reduce channel sensitivity to ATP inhibition, they arrive there via distinct mechanisms. Mutation of R74 uniformly reduced TMD0 protein levels, suggesting that R74 is necessary for stability of TMD0. In contrast, E128 mutations retained TMD0 protein levels but reduced functional coupling between TMD0 and Kir6.2 in mini-K(ATP) channels formed by TMD0 and Kir6.2. Importantly, E128K full-length channels, despite having a greatly reduced P(o), exhibit little response to phosphatidylinositol 4,5-bisphosphate (PIP(2)) stimulation. This is reminiscent of Kir6.2 channel behavior in the absence of SUR1 and suggests that TMD0 controls Kir6.2 gating by modulating Kir6.2 interactions with PIP(2). Further supporting this notion, the E128W mutation in full-length channels resulted in channel inactivation that was prevented or reversed by exogenous PIP(2). These results identify a critical determinant in TMD0 that controls Kir6.2 gating by controlling channel sensitivity to PIP(2). Moreover, they uncover a novel mechanism of K(ATP) channel inactivation involving aberrant functional coupling between SUR1 and Kir6.2.
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Affiliation(s)
- Emily B Pratt
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, OR 97239, USA
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Ion channels in inflammation. Pflugers Arch 2011; 461:401-21. [PMID: 21279380 DOI: 10.1007/s00424-010-0917-y] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Revised: 12/19/2010] [Accepted: 12/19/2010] [Indexed: 12/12/2022]
Abstract
Most physical illness in vertebrates involves inflammation. Inflammation causes disease by fluid shifts across cell membranes and cell layers, changes in muscle function and generation of pain. These disease processes can be explained by changes in numbers or function of ion channels. Changes in ion channels have been detected in diarrhoeal illnesses, pyelonephritis, allergy, acute lung injury and systemic inflammatory response syndromes involving septic shock. The key role played by changes in ion transport is directly evident in inflammation-induced pain. Expression or function of all major categories of ion channels like sodium, chloride, calcium, potassium, transient receptor potential, purinergic receptor and acid-sensing ion channels can be influenced by cyto- and chemokines, prostaglandins, leukotrienes, histamine, ATP, reactive oxygen species and protons released in inflammation. Key pathways in this interaction are cyclic nucleotide, phosphoinositide and mitogen-activated protein kinase-mediated signalling, direct modification by reactive oxygen species like nitric oxide, ATP or protons and disruption of the cytoskeleton. Therapeutic interventions to modulate the adverse and overlapping effects of the numerous different inflammatory mediators on each ion transport system need to target adversely affected ion transport systems directly and locally.
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Tang QY, Zhang Z, Xia J, Ren D, Logothetis DE. Phosphatidylinositol 4,5-bisphosphate activates Slo3 currents and its hydrolysis underlies the epidermal growth factor-induced current inhibition. J Biol Chem 2010; 285:19259-66. [PMID: 20392696 PMCID: PMC2885204 DOI: 10.1074/jbc.m109.100156] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2010] [Revised: 03/20/2010] [Indexed: 11/06/2022] Open
Abstract
The Slo3 gene encodes a high conductance potassium channel, which is activated by both voltage and intracellular alkalinization. Slo3 is specifically expressed in mammalian sperm cells, where it gives rise to pH-dependent outwardly rectifying K(+) currents. Sperm Slo3 is the main current responsible for the capacitation-induced hyperpolarization, which is required for the ensuing acrosome reaction, an exocytotic process essential for fertilization. Here we show that in intact spermatozoa and in a heterologous expression system, the activation of Slo3 currents is regulated by phosphatidylinositol 4,5-bisphosphate (PIP(2)). Depletion of endogenous PIP(2) in inside-out macropatches from Xenopus oocytes inhibited heterologously expressed Slo3 currents. Whole-cell recordings of sperm Slo3 currents or of Slo3 channels co-expressed in Xenopus oocytes with epidermal growth factor receptor, demonstrated that stimulation by epidermal growth factor (EGF) could inhibit channel activity in a PIP(2)-dependent manner. High concentrations of PIP(2) in the patch pipette not only resulted in a strong increase in sperm Slo3 current density but also prevented the EGF-induced inhibition of this current. Mutation of positively charged residues involved in channel-PIP(2) interactions enhanced the EGF-induced inhibition of Slo3 currents. Overall, our results suggest that PIP(2) is an important regulator for Slo3 activation and that receptor-mediated hydrolysis of PIP(2) leads to inhibition of Slo3 currents both in native and heterologous expression systems.
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Affiliation(s)
- Qiong-Yao Tang
- From the Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298-0551 and
| | - Zhe Zhang
- From the Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298-0551 and
| | - Jingsheng Xia
- the Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Dejian Ren
- the Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Diomedes E. Logothetis
- From the Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298-0551 and
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Li GR, Dong MQ. Pharmacology of Cardiac Potassium Channels. CARDIOVASCULAR PHARMACOLOGY - HEART AND CIRCULATION 2010; 59:93-134. [DOI: 10.1016/s1054-3589(10)59004-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Zhao FL, Herness S. Resynthesis of phosphatidylinositol 4,5-bisphosphate mediates adaptation of the caffeine response in rat taste receptor cells. J Physiol 2008; 587:363-77. [PMID: 19047199 DOI: 10.1113/jphysiol.2008.165167] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Caffeine, a prototypic bitter stimulus, produces several physiological actions on taste receptor cells that include inhibition of KIR and KV potassium currents and elevations of intracellular calcium. These responses display adaptation, i.e. their magnitude diminishes in the sustained presence of the stimulus. Levels of the membrane lipid phosphatidylinositol-4,5-bisphosphate (PIP2) are well known to modulate many potassium channels, activating the channel by stabilizing its open state. Here we investigate a putative relationship of KIR and KV with PIP2 levels hypothesizing that inhibition of these currents by caffeine might be allayed by PIP2 resynthesis. Using standard patch-clamp techniques, recordings of either potassium current from rat posterior taste receptor cells produced essentially parallel results when PIP2 levels were manipulated pharmacologically. Increasing PIP2 levels by blocking phosphoinositide-3 kinase with wortmannin or LY294002, or by blocking phospholipase C with U73122 all significantly increased the incidence of adaptation for both KIR and KV. Conversely, lowering PIP2 synthesis by blocking PI4K or using the PIP2 scavengers polylysine or bovine serum albumin reduced the incidence of adaptation. Adaptation could be modulated by activation of protein kinase C but not calcium calmodulin kinase. Collectively, these data support two highly novel conclusions: potassium currents in taste receptor cells are significantly modulated by PIP2 levels and PIP2 resynthesis may play a central role in the gustatory adaptation process at the primary receptor cell level.
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Affiliation(s)
- Fang-Li Zhao
- College of Dentistry, Ohio State University, Columbus, OH 43210, USA
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Abstract
Arrhythmias arise from a complex interaction between structural changes in the myocardium and changes in cellular electrophysiology. Electrophysiological balance requires precise control of sarcolemmal ion channels and exchangers, many of which are regulated by phospholipid, phosphatidylinositol(4,5)bisphosphate. Phosphatidylinositol(4,5)bisphosphate is the immediate precursor of inositol(1,4,5)trisphosphate, a regulator of intracellular Ca2+ signalling and, therefore, a potential contributor to arrhythmogenesis by altering Ca2+ homeostasis. The aim of the present review is to outline current evidence that this signalling pathway can be a player in the initiation or maintenance of arrhythmias.
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Affiliation(s)
- Elizabeth A Woodcock
- Molecular Cardiology Laboratory, Baker IDI Heart and Diabetes Institute, PO Box 6492, St Kilda Road Central, Melbourne, 8008 Victoria, Australia.
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Wang G, Zeng J, Shen CY, Wang ZQ, Chen SD. Overexpression of Kir2.3 in PC12 cells resists rotenone-induced neurotoxicity associated with PKC signaling pathway. Biochem Biophys Res Commun 2008; 374:204-9. [DOI: 10.1016/j.bbrc.2008.07.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Accepted: 07/01/2008] [Indexed: 12/23/2022]
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DEND mutation in Kir6.2 (KCNJ11) reveals a flexible N-terminal region critical for ATP-sensing of the KATP channel. Biophys J 2008; 95:4689-97. [PMID: 18708460 DOI: 10.1529/biophysj.108.138685] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
ATP-sensitive K(+)-channels link metabolism and excitability in neurons, myocytes, and pancreatic islets. Mutations in the pore-forming subunit (Kir6.2; KCNJ11) cause neonatal diabetes, developmental delay, and epilepsy by decreasing sensitivity to ATP inhibition and suppressing electrical activity. Mutations of residue G53 underlie both mild (G53R,S) and severe (G53D) forms of the disease. All examined substitutions (G53D,R,S,A,C,F) reduced ATP-sensitivity, indicating an intolerance of any amino acid other than glycine. Surprisingly, each mutation reduces ATP affinity, rather than intrinsic gating, although structural modeling places G53 at a significant distance from the ATP-binding pocket. We propose that glycine is required in this location for flexibility of the distal N-terminus, and for an induced fit of ATP at the binding site. Consistent with this hypothesis, glycine substitution of the adjacent residue (Q52G) partially rescues ATP affinity of reconstituted Q52G/G53D channels. The results reveal an important feature of the noncanonical ATP-sensing mechanism of K(ATP) channels.
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Lee CH, Huang PT, Lou KL, Liou HH. Functional and structural characterization of PKA-mediated pHi gating of ROMK1 channels. J Mol Graph Model 2008; 27:332-41. [PMID: 18620882 DOI: 10.1016/j.jmgm.2008.06.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 05/26/2008] [Accepted: 06/02/2008] [Indexed: 11/19/2022]
Abstract
Hyperprostaglandin E syndrome/antenatal Bartter syndrome (HPS/aBS) is a severe salt-losing renal tubular disorder and results from the mutation of renal outer medullary K(+) (ROMK1) channels. The aberrant ROMK1 function induces alterations in intracellular pH (pH(i)) gating under physiological conditions. We investigate the role of protein kinase A (PKA) in the pH(i) gating of ROMK1 channels. Using giant patch clamp with Xenopus oocytes expressing wild-type and mutant ROMK1 channels, PKA-mediated phosphorylation decreased the sensitivity of ROMK1 channels to pH(i). A homology model of ROMK1 reveals that a PKA phosphorylation site (S219) is spatially juxtaposed to the phosphatidylinositol 4,5-bisphosphate (PIP(2)) binding residues (R188, R217, and K218). Molecular dynamics simulations suggest a stable transition state, in which the shortening of distance between S219 and R217 and the movement of K218 towards the membrane after the PKA-phosphorylation can be observed. Such conformational change may bring the PIP(2) binding residues (K218) more accessible to the membrane-bound PIP(2). In addition, PIP(2) dose-dependently reactivates the acidification-induced rundown channels only when ROMK1 channels have been phosphorylated by PKA. This implies a sequence regulatory episode reflecting the role of PIP(2) in the pH(i) gating of ROMK1 channels by PKA-mediated phosphorylation. Our results provide new insights into the molecular mechanisms underlying the ROMK1 channel regulation associated with HPS/aBS.
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Affiliation(s)
- Chien-Hsing Lee
- Department of Pharmacology, College of Medicine, National Taiwan University, Taiwan
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Tucker SJ, Baukrowitz T. How highly charged anionic lipids bind and regulate ion channels. ACTA ACUST UNITED AC 2008; 131:431-8. [PMID: 18411329 PMCID: PMC2346576 DOI: 10.1085/jgp.200709936] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Stephen J Tucker
- Oxford Centre for Gene Function, Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, UK
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Xie LH, John SA, Ribalet B, Weiss JN. Phosphatidylinositol-4,5-bisphosphate (PIP2) regulation of strong inward rectifier Kir2.1 channels: multilevel positive cooperativity. J Physiol 2008; 586:1833-48. [PMID: 18276733 DOI: 10.1113/jphysiol.2007.147868] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Inwardly rectifying potassium (Kir) channels are gated by the interaction of their cytoplasmic regions with membrane-bound phosphatidylinositol-4,5-bisphosphate (PIP(2)). In the present study, we examined how PIP(2) interaction regulates channel availability and channel openings to various subconductance levels (sublevels) as well as the fully open state in the strong inward rectifier Kir2.1 channel. Various Kir2.1 channel constructs were expressed in Xenopus oocytes and single channel or macroscopic currents were recorded from inside-out patches. The wild-type (WT) channel rarely visited the subconductance levels under control conditions. However, upon reducing Kir2.1 channel interaction with PIP(2) by a variety of interventions, including PIP(2) antibodies, screening PIP(2) with neomycin, or mutating PIP(2) binding sites (e.g. K188Q), visitation to the sublevels was markedly increased before channels were converted to an unavailable mode in which they did not open. No channel activity was detected in channels with the double mutation K188A/R189A, a mutant which exhibits extremely weak interaction with PIP(2). By linking subunits together in tandem dimers or tetramers containing mixtures of WT and K188A/R189A subunits, we demonstrate that one functional PIP(2)-interacting WT subunit is sufficient to convert channels from the unavailable to the available mode with a high open probability dominated by the fully open state, with similar kinetics as tetrameric WT channels. Occasional openings to sublevels become progressively less frequent as the number of WT subunits increases. Quantitative analysis reveals that the interaction of PIP(2) with WT subunits exerts strong positive cooperativity in both converting the channels from the unavailable to the available mode, and in promoting the fully open state over sublevels. We conclude that the interaction of PIP(2) with only one Kir2.1 subunit is sufficient for the channel to become available and to open to its full conductance state. Interaction with additional subunits exerts positive cooperativity at multiple levels to further enhance channel availability and promote the fully open state.
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Affiliation(s)
- Lai-Hua Xie
- Cardiovascular Research Laboratory, Rm 3645 MRL Building, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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50
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Gamper N, Shapiro MS. Regulation of ion transport proteins by membrane phosphoinositides. Nat Rev Neurosci 2007; 8:921-34. [DOI: 10.1038/nrn2257] [Citation(s) in RCA: 192] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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