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Liu Q, Sun J, Dong Y, Li P, Wang J, Wang Y, Xu Y, Tian X, Wu B, He P, Yu Q, Lu X, Cao J. Tetramisole is a new I K1 channel agonist and exerts I K1 -dependent cardioprotective effects in rats. Pharmacol Res Perspect 2022; 10:e00992. [PMID: 35880674 PMCID: PMC9316008 DOI: 10.1002/prp2.992] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Revised: 06/22/2022] [Accepted: 07/04/2022] [Indexed: 11/30/2022] Open
Abstract
Cardiac ischemia, hypoxia, arrhythmias, and heart failure share the common electrophysiological changes featured by the elevation of intracellular Ca2+ (Ca2+ overload) and inhibition of the inward rectifier potassium (IK1 ) channel. IK1 channel agonists have been considered a new type of anti-arrhythmia and cardioprotective agents. We predicted using a drug repurposing strategy that tetramisole (Tet), a known anthelminthic agent, was a new IK1 channel agonist. The present study aimed to experimentally identify the above prediction and further demonstrate that Tet has cardioprotective effects. Results of the whole-cell patch clamp technique showed that Tet at 1-100 μmol/L enhanced IK1 current, hyperpolarized resting potential (RP), and shortened action potential duration (APD) in isolated rat cardiomyocytes, while without effects on other ion channels or transporters. In adult Sprague-Dawley (SD) rats in vivo, Tet showed anti-arrhythmia and anticardiac remodeling effects, respectively, in the coronary ligation-induced myocardial infarction model and isoproterenol (Iso, i.p., 3 mg/kg/day, 10 days) infusion-induced cardiac remodeling model. Tet also showed anticardiomyocyte remodeling effect in Iso (1 μmol/L) infused adult rat ventricular myocytes or cultured H9c2 (2-1) cardiomyocytes. Tet at 0.54 mg/kg in vivo or 30 μmol/L in vitro showed promising protections on acute ischemic arrhythmias, myocardial hypertrophy, and fibrosis. Molecular docking was performed and identified the selective binding of Tet with Kir2.1. The cardioprotection of Tet was associated with the facilitation of IK1 channel forward trafficking, deactivation of PKA signaling, and inhibition of intracellular calcium overload. Enhancing IK1 may play dual roles in anti-arrhythmia and antiventricular remodeling mediated by restoration of Ca2+ homeostasis.
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Affiliation(s)
- Qinghua Liu
- Department of PathophysiologyShanxi Medical UniversityTaiyuanChina
| | - Jiaxing Sun
- Department of PathophysiologyShanxi Medical UniversityTaiyuanChina
| | - Yangdou Dong
- Department of PathophysiologyShanxi Medical UniversityTaiyuanChina
| | - Pan Li
- Department of PathophysiologyShanxi Medical UniversityTaiyuanChina
| | - Jin Wang
- Key Laboratory of Cellular Physiology, Ministry of EducationShanxi Medical UniversityTaiyuanChina
- Department of PhysiologyShanxi Medical UniversityTaiyuanChina
| | - Yulan Wang
- Key Laboratory of Cellular Physiology, Ministry of EducationShanxi Medical UniversityTaiyuanChina
- Department of PhysiologyShanxi Medical UniversityTaiyuanChina
| | - Yanwu Xu
- Department of BiochemistryShanghai University of Traditional Chinese MedicineShanghaiChina
| | - Xinrui Tian
- Department of Respiratory and Critical Care MedicineSecond Hospital of Shanxi Medical UniversityTaiyuanChina
| | - Bowei Wu
- Key Laboratory of Cellular Physiology, Ministry of EducationShanxi Medical UniversityTaiyuanChina
- Department of PhysiologyShanxi Medical UniversityTaiyuanChina
| | - Peifeng He
- Shanxi Key Laboratory of Big Data for Clinical Decision Research, School of ManagementShanxi Medical UniversityTaiyuanChina
| | - Qi Yu
- Shanxi Key Laboratory of Big Data for Clinical Decision Research, School of ManagementShanxi Medical UniversityTaiyuanChina
| | - Xuechun Lu
- Department of Hematology, The Second Medical Center, Chinese PLA General HospitalNational clinical research center for geriatric diseaseBeijingChina
| | - Jimin Cao
- Key Laboratory of Cellular Physiology, Ministry of EducationShanxi Medical UniversityTaiyuanChina
- Department of PhysiologyShanxi Medical UniversityTaiyuanChina
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Wang YX, Wu H, Ren Y, Lv S, Ji C, Xiang D, Zhang M, Lu H, Fu W, Liu Q, Yan Z, Ma Q, Miao J, Cai R, Lan X, Wu B, Wang W, Liu Y, Wang DZ, Cao M, He Z, Shi Y, Ping Y, Yao X, Zhang X, Zhang P, Wang JM, Wang Y, Cui Y, Bian XW. Elevated Kir2.1/nuclear N2ICD defines a highly malignant subtype of non-WNT/SHH medulloblastomas. Signal Transduct Target Ther 2022; 7:72. [PMID: 35273141 PMCID: PMC8913686 DOI: 10.1038/s41392-022-00890-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 11/20/2021] [Accepted: 12/13/2021] [Indexed: 11/09/2022] Open
Abstract
Medulloblastoma (MB) is one of the most common childhood malignant brain tumors (WHO grade IV), traditionally divided into WNT, SHH, Group 3, and Group 4 subgroups based on the transcription profiles, somatic DNA alterations, and clinical outcomes. Unlike WNT and SHH subgroup MBs, Group 3 and Group 4 MBs have similar transcriptomes and lack clearly specific drivers and targeted therapeutic options. The recently revised WHO Classification of CNS Tumors has assigned Group 3 and 4 to a provisional non-WNT/SHH entity. In the present study, we demonstrate that Kir2.1, an inwardly-rectifying potassium channel, is highly expressed in non-WNT/SHH MBs, which promotes tumor cell invasion and metastasis by recruiting Adam10 to enhance S2 cleavage of Notch2 thereby activating the Notch2 signaling pathway. Disruption of the Notch2 pathway markedly inhibited the growth and metastasis of Kir2.1-overexpressing MB cell-derived xenograft tumors in mice. Moreover, Kir2.1high/nuclear N2ICDhigh MBs are associated with the significantly shorter lifespan of the patients. Thus, Kir2.1high/nuclear N2ICDhigh can be used as a biomarker to define a novel subtype of non-WNT/SHH MBs. Our findings are important for the modification of treatment regimens and the development of novel-targeted therapies for non-WNT/SHH MBs.
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Affiliation(s)
- Yan-Xia Wang
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Haibo Wu
- Department of Pathology, The First Affiliated Hospital of University of Science and Technology of China, 230036, Hefei, Anhui, China.,Intelligent Pathology Institute, Division of Life Sciences and Medicine, University of Science and Technology of China, 230036, Hefei, Anhui, China
| | - Yong Ren
- Department of Pathology, General Hospital of Central Theater Command of PLA, 627 Wuluo Road, Hongshan District, 430070, Wuhan, Hubei, China
| | - Shengqing Lv
- Xinqiao Hospital, Army Medical University, 400038, Chongqing, China
| | - Chengdong Ji
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Dongfang Xiang
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Mengsi Zhang
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Huimin Lu
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Wenjuan Fu
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Qing Liu
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Zexuan Yan
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Qinghua Ma
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Jingya Miao
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Ruili Cai
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Xi Lan
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Bin Wu
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Wenying Wang
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Yinhua Liu
- Department of Pathology, The First Affiliated Hospital of Wannan Medical College, 241001, Wuhu, Anhui, China
| | - Dai-Zhong Wang
- Department of Pathology, Taihe Hospital, Hubei University of Medicine, 442000, Shiyan, Hubei, China
| | - Mianfu Cao
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Zhicheng He
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Yu Shi
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Yifang Ping
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Xiaohong Yao
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Xia Zhang
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Peng Zhang
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China
| | - Ji Ming Wang
- Laboratory of Cancer and Immunometabolism, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD, 21703, US
| | - Yan Wang
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China.
| | - Youhong Cui
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China.
| | - Xiu-Wu Bian
- Institute of Pathology and Southwest Cancer Center, Southwest Hospital, Army Medical University (former Third Military Medical University), 400038, Chongqing, China.
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Chen L, He Y, Wang X, Ge J, Li H. Ventricular voltage-gated ion channels: Detection, characteristics, mechanisms, and drug safety evaluation. Clin Transl Med 2021; 11:e530. [PMID: 34709746 PMCID: PMC8516344 DOI: 10.1002/ctm2.530] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 07/23/2021] [Accepted: 07/26/2021] [Indexed: 02/06/2023] Open
Abstract
Cardiac voltage-gated ion channels (VGICs) play critical roles in mediating cardiac electrophysiological signals, such as action potentials, to maintain normal heart excitability and contraction. Inherited or acquired alterations in the structure, expression, or function of VGICs, as well as VGIC-related side effects of pharmaceutical drug delivery can result in abnormal cellular electrophysiological processes that induce life-threatening cardiac arrhythmias or even sudden cardiac death. Hence, to reduce possible heart-related risks, VGICs must be acknowledged as important targets in drug discovery and safety studies related to cardiac disease. In this review, we first summarize the development and application of electrophysiological techniques that are employed in cardiac VGIC studies alone or in combination with other techniques such as cryoelectron microscopy, optical imaging and optogenetics. Subsequently, we describe the characteristics, structure, mechanisms, and functions of various well-studied VGICs in ventricular myocytes and analyze their roles in and contributions to both physiological cardiac excitability and inherited cardiac diseases. Finally, we address the implications of the structure and function of ventricular VGICs for drug safety evaluation. In summary, multidisciplinary studies on VGICs help researchers discover potential targets of VGICs and novel VGICs in heart, enrich their knowledge of the properties and functions, determine the operation mechanisms of pathological VGICs, and introduce groundbreaking trends in drug therapy strategies, and drug safety evaluation.
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Affiliation(s)
- Lulan Chen
- Department of Cardiology, Shanghai Institute of Cardiovascular DiseasesShanghai Xuhui District Central Hospital & Zhongshan‐xuhui Hospital, Zhongshan Hospital, Fudan UniversityShanghaiChina
| | - Yue He
- Department of CardiologyShanghai Xuhui District Central Hospital & Zhongshan‐xuhui HospitalShanghaiChina
| | - Xiangdong Wang
- Institute of Clinical Science, Zhongshan HospitalFudan UniversityShanghaiChina
| | - Junbo Ge
- Department of Cardiology, Shanghai Institute of Cardiovascular DiseasesShanghai Xuhui District Central Hospital & Zhongshan‐xuhui Hospital, Zhongshan Hospital, Fudan UniversityShanghaiChina
| | - Hua Li
- Department of Cardiology, Shanghai Institute of Cardiovascular DiseasesShanghai Xuhui District Central Hospital & Zhongshan‐xuhui Hospital, Zhongshan Hospital, Fudan UniversityShanghaiChina
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Manoury B, Idres S, Leblais V, Fischmeister R. Ion channels as effectors of cyclic nucleotide pathways: Functional relevance for arterial tone regulation. Pharmacol Ther 2020; 209:107499. [PMID: 32068004 DOI: 10.1016/j.pharmthera.2020.107499] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Accepted: 02/05/2020] [Indexed: 02/07/2023]
Abstract
Numerous mediators and drugs regulate blood flow or arterial pressure by acting on vascular tone, involving cyclic nucleotide intracellular pathways. These signals lead to regulation of several cellular effectors, including ion channels that tune cell membrane potential, Ca2+ influx and vascular tone. The characterization of these vasocontrictive or vasodilating mechanisms has grown in complexity due to i) the variety of ion channels that are expressed in both vascular endothelial and smooth muscle cells, ii) the heterogeneity of responses among the various vascular beds, and iii) the number of molecular mechanisms involved in cyclic nucleotide signalling in health and disease. This review synthesizes key data from literature that highlight ion channels as physiologically relevant effectors of cyclic nucleotide pathways in the vasculature, including the characterization of the molecular mechanisms involved. In smooth muscle cells, cation influx or chloride efflux through ion channels are associated with vasoconstriction, whereas K+ efflux repolarizes the cell membrane potential and mediates vasodilatation. Both categories of ion currents are under the influence of cAMP and cGMP pathways. Evidence that some ion channels are influenced by CN signalling in endothelial cells will also be presented. Emphasis will also be put on recent data touching a variety of determinants such as phosphodiesterases, EPAC and kinase anchoring, that complicate or even challenge former paradigms.
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Affiliation(s)
- Boris Manoury
- Inserm, Umr-S 1180, Université Paris-Saclay, Châtenay-Malabry, France.
| | - Sarah Idres
- Inserm, Umr-S 1180, Université Paris-Saclay, Châtenay-Malabry, France
| | - Véronique Leblais
- Inserm, Umr-S 1180, Université Paris-Saclay, Châtenay-Malabry, France
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5
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Argyrousi EK, Heckman PRA, Prickaerts J. Role of cyclic nucleotides and their downstream signaling cascades in memory function: Being at the right time at the right spot. Neurosci Biobehav Rev 2020; 113:12-38. [PMID: 32044374 DOI: 10.1016/j.neubiorev.2020.02.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 01/23/2020] [Accepted: 02/03/2020] [Indexed: 01/23/2023]
Abstract
A plethora of studies indicate the important role of cAMP and cGMP cascades in neuronal plasticity and memory function. As a result, altered cyclic nucleotide signaling has been implicated in the pathophysiology of mnemonic dysfunction encountered in several diseases. In the present review we provide a wide overview of studies regarding the involvement of cyclic nucleotides, as well as their upstream and downstream molecules, in physiological and pathological mnemonic processes. Next, we discuss the regulation of the intracellular concentration of cyclic nucleotides via phosphodiesterases, the enzymes that degrade cAMP and/or cGMP, and via A-kinase-anchoring proteins that refine signal compartmentalization of cAMP signaling. We also provide an overview of the available data pointing to the existence of specific time windows in cyclic nucleotide signaling during neuroplasticity and memory formation and the significance to target these specific time phases for improving memory formation. Finally, we highlight the importance of emerging imaging tools like Förster resonance energy transfer imaging and optogenetics in detecting, measuring and manipulating the action of cyclic nucleotide signaling cascades.
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Affiliation(s)
- Elentina K Argyrousi
- Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, 6200 MD, the Netherlands
| | - Pim R A Heckman
- Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, 6200 MD, the Netherlands
| | - Jos Prickaerts
- Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, Maastricht, 6200 MD, the Netherlands.
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6
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Rivera-Pagán AF, Méndez-González MP, Rivera-Aponte DE, Malpica-Nieves CJ, Melnik-Martínez KV, Zayas-Santiago A, Maldonado-Martínez G, Shuba YM, Skatchkov SN, Eaton MJ. A-Kinase-Anchoring Protein (AKAP150) is expressed in Astrocytes and Upregulated in Response to Ischemia. Neuroscience 2018; 384:54-63. [PMID: 29800717 DOI: 10.1016/j.neuroscience.2018.05.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 05/11/2018] [Accepted: 05/14/2018] [Indexed: 10/16/2022]
Abstract
A-kinase-anchoring proteins, AKAPs, are scaffolding proteins that associate with kinases and phosphatases, and direct them to a specific submembrane site to coordinate signaling events. AKAP150, a rodent ortholog of human AKAP79, has been extensively studied in neurons, but very little is known about the localization and function of AKAP150 in astrocytes, the major cell type in brain. Thus, in this study, we assessed the localization of AKAP150 in astrocytes and elucidated its role during physiological and ischemic conditions. Herein, we demonstrate that AKAP150 is localized in astrocytes and is up-regulated during ischemia both in vitro and in vivo. Knock-down of AKAP150 by RNAi depolarizes the astrocytic membrane potential and substantially reduces by 80% the ability of astrocytes to take up extracellular potassium during ischemic conditions. Therefore, upregulation of AKAP150 during ischemia preserves potassium conductance and the associated hyperpolarized membrane potential of astrocytes; properties of astrocytes needed to maintain extracellular brain homeostasis. Taken together, these data suggest that AKAP150 may play a pivotal role in the neuroprotective mechanism of astrocytes during pathological conditions.
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Affiliation(s)
- Aixa F Rivera-Pagán
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States
| | - Miguel P Méndez-González
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States; University of Puerto Rico, Natural Sciences Department, Aguadilla, PR, United States
| | - David E Rivera-Aponte
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States
| | | | | | - Astrid Zayas-Santiago
- Department of Pathology and Laboratory Medicine, Universidad Central del Caribe, Bayamón, PR, United States
| | | | - Yaroslav M Shuba
- Bogomoletz Institute of Physiology and International Center of Molecular Physiology of the National Academy of Sciences of Ukraine, Kiev, Ukraine
| | - Serguei N Skatchkov
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States; Department of Physiology, Universidad Central del Caribe, Bayamón, PR, United States.
| | - Misty J Eaton
- Department of Biochemistry, Universidad Central del Caribe, Bayamón, PR, United States.
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7
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Hager NA, Krasowski CJ, Mackie TD, Kolb AR, Needham PG, Augustine AA, Dempsey A, Szent-Gyorgyi C, Bruchez MP, Bain DJ, Kwiatkowski AV, O'Donnell AF, Brodsky JL. Select α-arrestins control cell-surface abundance of the mammalian Kir2.1 potassium channel in a yeast model. J Biol Chem 2018; 293:11006-11021. [PMID: 29784874 DOI: 10.1074/jbc.ra117.001293] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 05/04/2018] [Indexed: 12/16/2022] Open
Abstract
Protein composition at the plasma membrane is tightly regulated, with rapid protein internalization and selective targeting to the cell surface occurring in response to environmental changes. For example, ion channels are dynamically relocalized to or from the plasma membrane in response to physiological alterations, allowing cells and organisms to maintain osmotic and salt homeostasis. To identify additional factors that regulate the selective trafficking of a specific ion channel, we used a yeast model for a mammalian potassium channel, the K+ inward rectifying channel Kir2.1. Kir2.1 maintains potassium homeostasis in heart muscle cells, and Kir2.1 defects lead to human disease. By examining the ability of Kir2.1 to rescue the growth of yeast cells lacking endogenous potassium channels, we discovered that specific α-arrestins regulate Kir2.1 localization. Specifically, we found that the Ldb19/Art1, Aly1/Art6, and Aly2/Art3 α-arrestin adaptor proteins promote Kir2.1 trafficking to the cell surface, increase Kir2.1 activity at the plasma membrane, and raise intracellular potassium levels. To better quantify the intracellular and cell-surface populations of Kir2.1, we created fluorogen-activating protein fusions and for the first time used this technique to measure the cell-surface residency of a plasma membrane protein in yeast. Our experiments revealed that two α-arrestin effectors also control Kir2.1 localization. In particular, both the Rsp5 ubiquitin ligase and the protein phosphatase calcineurin facilitated the α-arrestin-mediated trafficking of Kir2.1. Together, our findings implicate α-arrestins in regulating an additional class of plasma membrane proteins and establish a new tool for dissecting the trafficking itinerary of any membrane protein in yeast.
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Affiliation(s)
- Natalie A Hager
- From the Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282
| | - Collin J Krasowski
- From the Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282
| | - Timothy D Mackie
- the Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Alexander R Kolb
- the Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Patrick G Needham
- the Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Andrew A Augustine
- the Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Alison Dempsey
- the Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - Christopher Szent-Gyorgyi
- the Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - Marcel P Bruchez
- the Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - Daniel J Bain
- the Department of Geology and Environmental Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, and
| | - Adam V Kwiatkowski
- the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Allyson F O'Donnell
- From the Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282,
| | - Jeffrey L Brodsky
- the Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260,
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Ji CD, Wang YX, Xiang DF, Liu Q, Zhou ZH, Qian F, Yang L, Ren Y, Cui W, Xu SL, Zhao XL, Zhang X, Wang Y, Zhang P, Wang JM, Cui YH, Bian XW. Kir2.1 Interaction with Stk38 Promotes Invasion and Metastasis of Human Gastric Cancer by Enhancing MEKK2-MEK1/2-ERK1/2 Signaling. Cancer Res 2018; 78:3041-3053. [PMID: 29549164 DOI: 10.1158/0008-5472.can-17-3776] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 02/16/2018] [Accepted: 03/12/2018] [Indexed: 12/17/2022]
Abstract
Potassium ion channels are emerging as promalignant factors involved in cancer progression. In this study, we found that invading human gastric cancer cells express high levels of inwardly rectifying potassium channel 2.1 (Kir2.1). Silencing Kir2.1 markedly reduced the invasive and metastatic capabilities as well as the epithelial-mesenchymal transition (EMT) of gastric cancer cells. The promalignant nature of Kir2.1 in gastric cancer cells was independent of potassium permeation but relied on its interaction with serine/threonine-protein kinase 38 (Stk38) to inhibit ubiquitination and degradation of mitogen-activated protein kinase kinase kinase 2 (MEKK2). Degradation of MEKK2 was mediated by small mothers against decapentaplegic-specific E3 ubiquitin protein ligase 1 (Smurf1), which resulted in activation of the MEK1/2-ERK1/2-Snail pathway in gastric cancer cells. In human gastric cancer tissues, expression was high and positively correlated with invasion depth and metastatic status of the tumors as well as poor overall patient survival. Cox regression analysis identified Kir2.1 as an independent prognostic indicator for patients with gastric cancer. Our results suggest that Kir2.1 is an important regulator of gastric cancer malignancy and acts as a novel prognostic marker and a therapeutic target for gastric cancer.Significance: Kir2.1 contributes to invasion and metastasis by a noncanonical ion permeation-independent signaling pathway and may act as a novel prognostic marker and therapeutic target for gastric cancer. Cancer Res; 78(11); 3041-53. ©2018 AACR.
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Affiliation(s)
- Cheng-Dong Ji
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Yan-Xia Wang
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Dong-Fang Xiang
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Qiang Liu
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Zhi-Hua Zhou
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Feng Qian
- Department of General Surgery, Southwest Hospital, Third Military Medical University, Chongqing, China
| | - Lang Yang
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Yong Ren
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Wei Cui
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Sen-Lin Xu
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Xi-Long Zhao
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Xia Zhang
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Yan Wang
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Peng Zhang
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Ji-Ming Wang
- Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, Maryland
| | - You-Hong Cui
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China.
| | - Xiu-Wu Bian
- Institute of Pathology and Southwest Cancer Center and Key Laboratory of Tumor Immunopathology of Ministry of Education of China, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China.
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9
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Jackson WF. Boosting the signal: Endothelial inward rectifier K + channels. Microcirculation 2018; 24. [PMID: 27652592 DOI: 10.1111/micc.12319] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 09/12/2016] [Indexed: 12/19/2022]
Abstract
Endothelial cells express a diverse array of ion channels including members of the strong inward rectifier family composed of KIR 2 subunits. These two-membrane spanning domain channels are modulated by their lipid environment, and exist in macromolecular signaling complexes with receptors, protein kinases and other ion channels. Inward rectifier K+ channel (KIR ) currents display a region of negative slope conductance at membrane potentials positive to the K+ equilibrium potential that allows outward current through the channels to be activated by membrane hyperpolarization, permitting KIR to amplify hyperpolarization induced by other K+ channels and ion transporters. Increases in extracellular K+ concentration activate KIR allowing them to sense extracellular K+ concentration and transduce this change into membrane hyperpolarization. These properties position KIR to participate in the mechanism of action of hyperpolarizing vasodilators and contribute to cell-cell conduction of hyperpolarization along the wall of microvessels. The expression of KIR in capillaries in electrically active tissues may allow KIR to sense extracellular K+ , contributing to functional hyperemia. Understanding the regulation of expression and function of microvascular endothelial KIR will improve our understanding of the control of blood flow in the microcirculation in health and disease and may provide new targets for the development of therapeutics in the future.
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Affiliation(s)
- William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, USA
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10
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Abstract
Although the mechanism of sudden cardiac death (SCD) in heart failure is not completely known, genetic variations are known to play key roles in this process. Increasing numbers of mutations and variants are being discovered through genome-wide association studies. The genetic variations involved in the mechanisms of SCD have aroused widespread concern. Comprehensive understanding of the genetic variations involved in SCD may help prevent it. To this end, we briefly reviewed the genetic variations involved in SCD and their associations and interactions, and observed that cardiac ion channels are the core molecules involved in this process. Genetic variations involved in cardiac structure, cardiogenesis and development, cell division and differentiation, and DNA replication and transcription are all speculated to be loci involved in SCD. Additionally, the systems involved in neurohumoral regulation as well as substance and energy metabolism are also potentially responsible for susceptibility to SCD. They form an elaborate network and mutually interact with each other to govern the fate of SCD-susceptible individuals.
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11
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Role of plasma membrane-associated AKAPs for the regulation of cardiac IK1 current by protein kinase A. Naunyn Schmiedebergs Arch Pharmacol 2017; 390:493-503. [DOI: 10.1007/s00210-017-1344-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 01/12/2017] [Indexed: 12/20/2022]
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12
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Tykocki NR, Boerman EM, Jackson WF. Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles. Compr Physiol 2017; 7:485-581. [PMID: 28333380 DOI: 10.1002/cphy.c160011] [Citation(s) in RCA: 212] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body's tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. © 2017 American Physiological Society. Compr Physiol 7:485-581, 2017.
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Affiliation(s)
- Nathan R Tykocki
- Department of Pharmacology, University of Vermont, Burlington, Vermont, USA
| | - Erika M Boerman
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, USA
| | - William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA
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13
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Bolger GB. The PDE4 cAMP-Specific Phosphodiesterases: Targets for Drugs with Antidepressant and Memory-Enhancing Action. ADVANCES IN NEUROBIOLOGY 2017; 17:63-102. [PMID: 28956330 DOI: 10.1007/978-3-319-58811-7_4] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The PDE4 cyclic nucleotide phosphodiesterases are essential regulators of cAMP abundance in the CNS through their ability to regulate PKA activity, the phosphorylation of CREB, and other important elements of signal transduction. In pre-clinical models and in early-stage clinical trials, PDE4 inhibitors have been shown to have antidepressant and memory-enhancing activity. However, the development of clinically-useful PDE4 inhibitors for CNS disorders has been limited by variable efficacy and significant side effects. Recent structural studies have greatly enhanced our understanding of the molecular configuration of PDE4 enzymes, especially the "long" PDE4 isoforms that are abundant in the CNS. The new structural data provide a rationale for the development of a new generation of PDE4 inhibitors that specifically act on long PDE4 isoforms. These next generation PDE4 inhibitors may also be capable of targeting the interactions of select long forms with their "partner" proteins, such as RACK1, β-arrestin, and DISC1. They would therefore have the ability to affect cAMP levels in specific cellular compartments and target localized cellular functions, such as synaptic plasticity. These new agents might also be able to target PDE4 populations in select regions of the CNS that are implicated in learning and memory, affect, and cognition. Potential therapeutic uses of these agents could include affective disorders, memory enhancement, and neurogenesis.
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Affiliation(s)
- Graeme B Bolger
- Departments of Medicine and Pharmacology, University of Alabama at Birmingham, 1720 2nd Avenue South, NP 2501, Birmingham, AL, 35294-3300, USA.
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14
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Abriel H, Rougier JS, Jalife J. Ion channel macromolecular complexes in cardiomyocytes: roles in sudden cardiac death. Circ Res 2015; 116:1971-88. [PMID: 26044251 DOI: 10.1161/circresaha.116.305017] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The movement of ions across specific channels embedded on the membrane of individual cardiomyocytes is crucial for the generation and propagation of the cardiac electric impulse. Emerging evidence over the past 20 years strongly suggests that the normal electric function of the heart is the result of dynamic interactions of membrane ion channels working in an orchestrated fashion as part of complex molecular networks. Such networks work together with exquisite temporal precision to generate each action potential and contraction. Macromolecular complexes play crucial roles in transcription, translation, oligomerization, trafficking, membrane retention, glycosylation, post-translational modification, turnover, function, and degradation of all cardiac ion channels known to date. In addition, the accurate timing of each cardiac beat and contraction demands, a comparable precision on the assembly and organizations of sodium, calcium, and potassium channel complexes within specific subcellular microdomains, where physical proximity allows for prompt and efficient interaction. This review article, part of the Compendium on Sudden Cardiac Death, discusses the major issues related to the role of ion channel macromolecular assemblies in normal cardiac electric function and the mechanisms of arrhythmias leading to sudden cardiac death. It provides an idea of how these issues are being addressed in the laboratory and in the clinic, which important questions remain unanswered, and what future research will be needed to improve knowledge and advance therapy.
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Affiliation(s)
- Hugues Abriel
- From the Department of Clinical Research, University of Bern, Bern, Switzerland (H.A., J.-S.R.); Center for Arrhythmia Research, Department of Internal Medicine, University of Michigan, Ann Arbor (J.J.); and Area of Myocardial Pathophysiology, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain (J.J.)
| | - Jean-Sébastien Rougier
- From the Department of Clinical Research, University of Bern, Bern, Switzerland (H.A., J.-S.R.); Center for Arrhythmia Research, Department of Internal Medicine, University of Michigan, Ann Arbor (J.J.); and Area of Myocardial Pathophysiology, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain (J.J.)
| | - José Jalife
- From the Department of Clinical Research, University of Bern, Bern, Switzerland (H.A., J.-S.R.); Center for Arrhythmia Research, Department of Internal Medicine, University of Michigan, Ann Arbor (J.J.); and Area of Myocardial Pathophysiology, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain (J.J.).
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15
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Targeting protein-protein interactions within the cyclic AMP signaling system as a therapeutic strategy for cardiovascular disease. Future Med Chem 2013; 5:451-64. [PMID: 23495691 DOI: 10.4155/fmc.12.216] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The cAMP signaling system can trigger precise physiological cellular responses that depend on the fidelity of many protein-protein interactions, which act to bring together signaling intermediates at defined locations within cells. In the heart, cAMP participates in the fine control of excitation-contraction coupling, hence, any disregulation of this signaling cascade can lead to cardiac disease. Due to the ubiquitous nature of the cAMP pathway, general inhibitors of cAMP signaling proteins such as PKA, EPAC and PDEs would act non-specifically and universally, increasing the likelihood of serious 'off target' effects. Recent advances in the discovery of peptides and small molecules that disrupt the protein-protein interactions that underpin cellular targeting of cAMP signaling proteins are described and discussed.
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16
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Zhang L, Liu Q, Liu C, Zhai X, Feng Q, Xu R, Cui X, Zhao Z, Cao J, Wu B. Zacopride selectively activates the Kir2.1 channel via a PKA signaling pathway in rat cardiomyocytes. SCIENCE CHINA-LIFE SCIENCES 2013; 56:788-96. [PMID: 23929001 DOI: 10.1007/s11427-013-4531-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 07/08/2013] [Indexed: 10/26/2022]
Abstract
We recently reported that zacopride is a selective inward rectifier potassium current (I K1) channel agonist, suppressing ventricular arrhythmias without affecting atrial arrhythmias. The present study aimed to investigate the unique pharmacological properties of zacopride. The whole-cell patch-clamp technique was used to study I K1 currents in rat atrial myocytes and Kir2.x currents in human embryonic kidney (HEK)-293 cells transfected with inward rectifier potassium channel (Kir)2.1, Kir2.2, Kir2.3, or mutated Kir2.1 (at phosphorylation site S425L). Western immunoblots were performed to estimate the relative protein expression levels of Kir2.x in rat atria and ventricles. Results showed that zacopride did not affect the IK1 and transmembrane potential of atrial myocytes. In HEK293 cells, zacopride increased Kir2.1 homomeric channels by 40.7%±9.7% at -50 mV, but did not affect Kir2.2 and Kir2.3 homomeric channels, and Kir2.1-Kir2.2, Kir2.1-Kir2.3 and Kir2.2-Kir2.3 heteromeric channels. Western immunoblots showed that similar levels of Kir2.3 protein were expressed in rat atria and ventricles, but atrial Kir2.1 protein level was only 25% of that measured in the ventricle. In addition, 5-hydroxytryptamine (5-HT)3 receptor was undetectable, whereas 5-HT4 receptor was weakly expressed in HEK293 cells. The Kir2.1-activating effect of zacopride in these cells was abolished by inhibition of protein kinase A (PKA), but not PKC or PKG. Furthermore, zacopride did not activate the mutant Kir2.1 channel in HEK293 cells but selectively activated the Kir2.1 homomeric channel via a PKA-dependent pathway, independent to that of the 5-HT receptor.
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Affiliation(s)
- Li Zhang
- Department of Physiology and the Key Laboratory of Cellular Physiology, Ministry of Education, Shanxi Medical University, Taiyuan 030001, China
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17
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The degradation of the inwardly rectifying potassium channel, Kir2.1, depends on the expression level: examination with fluorescent proteins. Brain Res 2013; 1528:8-19. [PMID: 23850646 DOI: 10.1016/j.brainres.2013.07.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2012] [Revised: 07/01/2013] [Accepted: 07/05/2013] [Indexed: 01/24/2023]
Abstract
The expression of ion channels is regulated by their synthesis as well as degradation, and some ion channels are degraded in an expression level-dependent way. Recently, new techniques of fluorescent proteins have been developed and seem to be useful to study protein degradation. To examine the regulation of the degradation of strongly inwardly rectifying potassium channel (Kir2.1) and the usefulness of the fluorescent proteins, we constructed Kir2.1 fusion proteins with SNAP tag and fluorescent timer (FT). The SNAP tag, which covalently binds to a specific membrane-permeable fluorescent dye, enables a pulse-chase experiment with fluorescence. When the SNAP-Kir2.1 proteins were expressed in 293T cells by low and high expression plasmids, the half-life of the fusion protein expressed by a high-expression plasmid was shorter (18.2±1.9 h) than that expressed by a low-expression plasmid (35.1+2.3h). The addition of Ba(2+), a selective blocker of Kir2.1, slowed the degradation, suggesting a current-dependency of degradation. Consistently, patch-clamp recording showed that cultivation in the presence of Ba(2+) increased the whole cell conductance of SNAP-Kir2.1. Since the fluorescence of FT changes gradually changes from green to red, the green/red ratio should allow us to monitor the changes in the degradation rate of FT-Kir2.1. Using this method, we confirmed the slower degradation by Ba(2+). The results suggest a homeostatic regulation of the degradation of Kir2.1 in the 293T cells, and the usefulness of fluorescence-based methods for examining the degradation of ion channels.
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18
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Up-Regulation of the Inwardly Rectifying K+ Channel Kir2.1 (KCNJ2) by Protein Kinase B (PKB/Akt) and PIKfyve. J Membr Biol 2012. [DOI: 10.1007/s00232-012-9520-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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19
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Chu W, Li C, Qu X, Zhao D, Wang X, Yu X, Cai F, Liang H, Zhang Y, Zhao X, Li B, Qiao G, Dong D, Lu Y, Du Z, Yang B. Arsenic-induced interstitial myocardial fibrosis reveals a new insight into drug-induced long QT syndrome. Cardiovasc Res 2012; 96:90-8. [PMID: 22853924 DOI: 10.1093/cvr/cvs230] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
AIMS Arsenic trioxide (ATO), an effective therapeutic agent for acute promyelocytic leukaemia, can cause sudden cardiac death due to long QT syndrome (LQTS). The present study was designed to determine whether ATO could induce cardiac fibrosis and explore whether cardiac fibroblasts (CFs) are involved in the development of LQTS by ATO. METHODS AND RESULTS ATO treatment of guinea pigs caused substantial interstitial myocardial fibrosis and LQTS, which was accompanied by an increase in transforming growth factor β1(TGF-β1) secretion and a decrease in ether-à-go-go-related gene (HERG) and inward rectifying potassium channel (I(K1)) subunit Kir2.1 protein levels. ATO promoted collagen production and TGF-β1 expression and secretion in cultured CFs. Whole-cell patch clamp and western blotting showed that treatment with TGF-β1 markedly reduced HERG and I(K1) current densities and downregulated HERG and Kir2.1 protein expression in HEK293 cells stably transfected with the human recombinant HERG channel and in cardiomyocytes (CMs). These changes were completely reversed by treatment with the protein kinase A (PKA) antagonist, H89. CM and CF co-cultures showed that ATO significantly increased TGF-β1 levels in the culture medium, whereas markedly reduced HERG and Kir2.1 protein levels were observed in CMs compared with ATO-treated CMs not co-cultured with CFs. Finally, in vivo administration of LY364947, a pharmacological antagonist of TGF-β signalling, dramatically prevented interstitial fibrosis and LQTS and abolished aberrant expression of TGF-β1, HERG, and Kir2.1 in ATO-treated guinea pigs. CONCLUSION ATO-induced TGF-β1 secretion from CFs aggravates QT prolongation, suggesting that modulation of TGF-β signalling may provide a novel strategy for the treatment of drug-induced LQTS.
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Affiliation(s)
- Wenfeng Chu
- Department of Pharmacology, Harbin Medical University, Xuefu Road 194, Harbin, Heilongjiang 150081, PR China
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20
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Ting JT, Peça J, Feng G. Functional consequences of mutations in postsynaptic scaffolding proteins and relevance to psychiatric disorders. Annu Rev Neurosci 2012; 35:49-71. [PMID: 22540979 DOI: 10.1146/annurev-neuro-062111-150442] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Functional studies on postsynaptic scaffolding proteins at excitatory synapses have revealed a plethora of important roles for synaptic structure and function. In addition, a convergence of recent in vivo functional evidence together with human genetics data strongly suggest that mutations in a variety of these postsynaptic scaffolding proteins may contribute to the etiology of diverse human psychiatric disorders such as schizophrenia, autism spectrum disorders, and obsessive-compulsive spectrum disorders. Here we review the most recent evidence for several key postsynaptic scaffolding protein families and explore how mouse genetics and human genetics have intersected to advance our knowledge concerning the contributions of these important players to complex brain function and dysfunction.
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Affiliation(s)
- Jonathan T Ting
- McGovern Institute for Brain Research and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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21
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Seebohm G, Strutz-Seebohm N, Ursu ON, Preisig-Müller R, Zuzarte M, Hill EV, Kienitz MC, Bendahhou S, Fauler M, Tapken D, Decher N, Collins A, Jurkat-Rott K, Steinmeyer K, Lehmann-Horn F, Daut J, Tavaré JM, Pott L, Bloch W, Lang F. Altered stress stimulation of inward rectifier potassium channels in Andersen-Tawil syndrome. FASEB J 2011; 26:513-22. [PMID: 22002906 DOI: 10.1096/fj.11-189126] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Inward rectifier potassium channels of the Kir2 subfamily are important determinants of the electrical activity of brain and muscle cells. Genetic mutations in Kir2.1 associate with Andersen-Tawil syndrome (ATS), a familial disorder leading to stress-triggered periodic paralysis and ventricular arrhythmia. To identify the molecular mechanisms of this stress trigger, we analyze Kir channel function and localization electrophysiologically and by time-resolved confocal microscopy. Furthermore, we employ a mathematical model of muscular membrane potential. We identify a novel corticoid signaling pathway that, when activated by glucocorticoids, leads to enrichment of Kir2 channels in the plasma membranes of mammalian cell lines and isolated cardiac and skeletal muscle cells. We further demonstrate that activation of this pathway can either partly restore (40% of cases) or further impair (20% of cases) the function of mutant ATS channels, depending on the particular Kir2.1 mutation. This means that glucocorticoid treatment might either alleviate or deteriorate symptoms of ATS depending on the patient's individual Kir2.1 genotype. Thus, our findings provide a possible explanation for the contradictory effects of glucocorticoid treatment on symptoms in patients with ATS and may open new pathways for the design of personalized medicines in ATS therapy.
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Affiliation(s)
- Guiscard Seebohm
- Department of Biochemistry I-Cation Channel Group, Ruhr University Bochum, Bochum, Germany.
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22
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Abstract
Voltage-gated M-type (KCNQ) K+ channels play critical roles in regulation of neuronal excitability. Previous work showed A-kinase-anchoring protein (AKAP)79/150-mediated protein kinase C (PKC) phosphorylation of M channels to be involved in M current (I(M)) suppression by muscarinic M1, but not bradykinin B2, receptors. In this study, we first explored whether purinergic and angiotensin suppression of I(M) in superior cervical ganglion (SCG) sympathetic neurons involves AKAP79/150. Transfection into rat SCG neurons of ΔA-AKAP79, which lacks the A domain necessary for PKC binding, or the absence of AKAP150 in AKAP150(-/-) mice, did not affect I(M) suppression by purinergic agonist or by bradykinin, but reduced I(M) suppression by muscarinic agonist and angiotensin II. Transfection of AKAP79, but not ΔA-AKAP79 or AKAP15, rescued suppression of I(M) by muscarinic receptors in AKAP150(-/-) neurons. We also tested association of AKAP79 with M(1), B(2), P2Y(6), and AT(1) receptors, and KCNQ2 and KCNQ3 channels, via Förster resonance energy transfer (FRET) on Chinese hamster ovary cells under total internal refection fluorescence microscopy, which revealed substantial FRET between AKAP79 and M1 or AT1 receptors, and with the channels, but only weak FRET with P2Y(6) or B2 receptors. The involvement of AKAP79/150 in G(q/11)-coupled muscarinic regulation of N- and L-type Ca2+) channels and by cAMP/protein kinase A was also studied. We found AKAP79/150 to not play a role in the former, but to be necessary for forskolin-induced upregulation of L-current. Thus, AKAP79/150 action correlates with the PIP(2) (phosphatidylinositol 4,5-bisphosphate)-depletion mode of I(M) suppression, but does not generalize to G(q/11)-mediated inhibition of N- or L-type Ca2+ channels.
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Delint-Ramirez I, Willoughby D, Hammond GRV, Hammond GVR, Ayling LJ, Cooper DMF. Palmitoylation targets AKAP79 protein to lipid rafts and promotes its regulation of calcium-sensitive adenylyl cyclase type 8. J Biol Chem 2011; 286:32962-75. [PMID: 21771783 PMCID: PMC3190942 DOI: 10.1074/jbc.m111.243899] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
PKA anchoring proteins (AKAPs) optimize the efficiency of cAMP signaling by clustering interacting partners. Recently, AKAP79 has been reported to directly bind to adenylyl cyclase type 8 (AC8) and to regulate its responsiveness to store-operated Ca2+ entry (SOCE). Although AKAP79 is well targeted to the plasma membrane via phospholipid associations with three N-terminal polybasic regions, recent studies suggest that AKAP79 also has the potential to be palmitoylated, which may specifically allow it to target the lipid rafts where AC8 resides and is regulated by SOCE. In this study, we have addressed the role of palmitoylation of AKAP79 using a combination of pharmacological, mutagenesis, and cell biological approaches. We reveal that AKAP79 is palmitoylated via two cysteines in its N-terminal region. This palmitoylation plays a key role in targeting the AKAP to lipid rafts in HEK-293 cells. Mutation of the two critical cysteines results in exclusion of AKAP79 from lipid rafts and alterations in its membrane diffusion behavior. This is accompanied by a loss of the ability of AKAP79 to regulate SOCE-dependent AC8 activity in intact cells and decreased PKA-dependent phosphorylation of raft proteins, including AC8. We conclude that palmitoylation plays a key role in the targeting and action of AKAP79. This novel property of AKAP79 adds an unexpected regulatory and targeting option for AKAPs, which may be exploited in the cellular context.
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Affiliation(s)
- Ilse Delint-Ramirez
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
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24
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Welch EJ, Jones BW, Scott JD. Networking with AKAPs: context-dependent regulation of anchored enzymes. Mol Interv 2010; 10:86-97. [PMID: 20368369 DOI: 10.1124/mi.10.2.6] [Citation(s) in RCA: 131] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A-Kinase Anchoring Proteins (AKAPs) orchestrate and synchronize cellular events by tethering the cAMP-dependent protein kinase (PKA) and other signaling enzymes to organelles and membranes. The control of kinases and phosphatases that are held in proximity to activators, effectors, and substrates favors the rapid dissemination of information from one cellular location to the next. This article charts the inception of the PKA-anchoring hypothesis, the characterization of AKAPs and their nomenclature, and the physiological roles of context-specific AKAP signaling complexes.
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Affiliation(s)
- Emily J Welch
- Howard Hughes Medical Institute, Department of Pharmacology, University of Washington School of Medicine, Seattle, WA 98195, USA
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25
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Vaidyanathan R, Taffet SM, Vikstrom KL, Anumonwo JMB. Regulation of cardiac inward rectifier potassium current (I(K1)) by synapse-associated protein-97. J Biol Chem 2010; 285:28000-9. [PMID: 20530486 DOI: 10.1074/jbc.m110.110858] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Synapse-associated protein-97 (SAP97) is a membrane-associated guanylate kinase scaffolding protein expressed in cardiomyocytes. SAP97 has been shown to associate and modulate voltage-gated potassium (Kv) channel function. In contrast to Kv channels, little information is available on interactions involving SAP97 and inward rectifier potassium (Kir2.x) channels that underlie the classical inward rectifier current, I(K1). To investigate the functional effects of silencing SAP97 on I(K1) in adult rat ventricular myocytes, SAP97 was silenced using an adenoviral short hairpin RNA vector. Western blot analysis showed that SAP97 was silenced by approximately 85% on day 3 post-infection. Immunostaining showed that Kir2.1 and Kir2.2 co-localize with SAP97. Co-immunoprecipitation (co-IP) results demonstrated that Kir2.x channels associate with SAP97. Voltage clamp experiments showed that silencing SAP97 reduced I(K1) whole cell density by approximately 55%. I(K1) density at -100 mV was -1.45 +/- 0.15 pA/picofarads (n = 6) in SAP97-silenced cells as compared with -3.03 +/- 0.37 pA/picofarads (n = 5) in control cells. Unitary conductance properties of I(K1) were unaffected by SAP97 silencing. The major mechanism for the reduction of I(K1) density appears to be a decrease in Kir2.x channel abundance. Furthermore, SAP97 silencing impaired I(K1) regulation by beta(1)-adrenergic receptor (beta1-AR) stimulation. In control, isoproterenol reduced I(K1) amplitude by approximately 75%, an effect that was blunted following SAP97 silencing. Our co-IP data show that beta1-AR associates with SAP97 and Kir2.1 and also that Kir2.1 co-IPs with protein kinase A and beta1-AR. SAP97 immunolocalizes with protein kinase A and beta1-AR in the cardiac myocytes. Our results suggest that in cardiac myocytes SAP97 regulates surface expression of channels underlying I(K1), as well as assembles a signaling complex involved in beta1-AR regulation of I(K1).
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Affiliation(s)
- Ravi Vaidyanathan
- Department of Pharmacology, State University of New York Upstate Medical University, Syracuse, New York 13210, USA
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26
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Weisenhaus M, Allen ML, Yang L, Lu Y, Nichols CB, Su T, Hell JW, McKnight GS. Mutations in AKAP5 disrupt dendritic signaling complexes and lead to electrophysiological and behavioral phenotypes in mice. PLoS One 2010; 5:e10325. [PMID: 20428246 PMCID: PMC2859064 DOI: 10.1371/journal.pone.0010325] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Accepted: 03/31/2010] [Indexed: 11/18/2022] Open
Abstract
AKAP5 (also referred to as AKAP150 in rodents and AKAP79 in humans) is a scaffolding protein that is highly expressed in neurons and targets a variety of signaling molecules to dendritic membranes. AKAP5 interacts with PKA holoenzymes containing RIIα or RIIβ as well as calcineurin (PP2B), PKC, calmodulin, adenylyl cyclase type V/VI, L-type calcium channels, and β-adrenergic receptors. AKAP5 has also been shown to interact with members of the MAGUK family of PSD-scaffolding proteins including PSD95 and SAP97 and target signaling molecules to receptors and ion channels in the postsynaptic density (PSD). We created two lines of AKAP5 mutant mice: a knockout of AKAP5 (KO) and a mutant that lacks the PKA binding domain of AKAP5 (D36). We find that PKA is delocalized in both the hippocampus and striatum of KO and D36 mice indicating that other neural AKAPs cannot compensate for the loss of PKA binding to AKAP5. In AKAP5 mutant mice, a significant fraction of PKA becomes localized to dendritic shafts and this correlates with increased binding to microtubule associated protein-2 (MAP2). Electrophysiological and behavioral analysis demonstrated more severe deficits in both synaptic plasticity and operant learning in the D36 mice compared with the complete KO animals. Our results indicate that the targeting of calcineurin or other binding partners of AKAP5 in the absence of the balancing kinase, PKA, leads to a disruption of synaptic plasticity and results in learning and memory defects.
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Affiliation(s)
- Michael Weisenhaus
- Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Margaret L. Allen
- Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Linghai Yang
- Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Yuan Lu
- Department of Pharmacology, University of California Davis, Davis, California, United States of America
| | - C. Blake Nichols
- Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Thomas Su
- Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Johannes W. Hell
- Department of Pharmacology, University of California Davis, Davis, California, United States of America
| | - G. Stanley McKnight
- Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington, United States of America
- * E-mail:
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Hibino H, Inanobe A, Furutani K, Murakami S, Findlay I, Kurachi Y. Inwardly rectifying potassium channels: their structure, function, and physiological roles. Physiol Rev 2010; 90:291-366. [PMID: 20086079 DOI: 10.1152/physrev.00021.2009] [Citation(s) in RCA: 1074] [Impact Index Per Article: 76.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Inwardly rectifying K(+) (Kir) channels allow K(+) to move more easily into rather than out of the cell. They have diverse physiological functions depending on their type and their location. There are seven Kir channel subfamilies that can be classified into four functional groups: classical Kir channels (Kir2.x) are constitutively active, G protein-gated Kir channels (Kir3.x) are regulated by G protein-coupled receptors, ATP-sensitive K(+) channels (Kir6.x) are tightly linked to cellular metabolism, and K(+) transport channels (Kir1.x, Kir4.x, Kir5.x, and Kir7.x). Inward rectification results from pore block by intracellular substances such as Mg(2+) and polyamines. Kir channel activity can be modulated by ions, phospholipids, and binding proteins. The basic building block of a Kir channel is made up of two transmembrane helices with cytoplasmic NH(2) and COOH termini and an extracellular loop which folds back to form the pore-lining ion selectivity filter. In vivo, functional Kir channels are composed of four such subunits which are either homo- or heterotetramers. Gene targeting and genetic analysis have linked Kir channel dysfunction to diverse pathologies. The crystal structure of different Kir channels is opening the way to understanding the structure-function relationships of this simple but diverse ion channel family.
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Affiliation(s)
- Hiroshi Hibino
- Department of Pharmacology, Graduate School of Medicine and The Center for Advanced Medical Engineering and Informatics, Osaka University, Osaka 565-0871, Japan
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28
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Mechanisms of protein kinase A anchoring. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 283:235-330. [PMID: 20801421 DOI: 10.1016/s1937-6448(10)83005-9] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The second messenger cyclic adenosine monophosphate (cAMP), which is produced by adenylyl cyclases following stimulation of G-protein-coupled receptors, exerts its effect mainly through the cAMP-dependent serine/threonine protein kinase A (PKA). Due to the ubiquitous nature of the cAMP/PKA system, PKA signaling pathways underlie strict spatial and temporal control to achieve specificity. A-kinase anchoring proteins (AKAPs) bind to the regulatory subunit dimer of the tetrameric PKA holoenzyme and thereby target PKA to defined cellular compartments in the vicinity of its substrates. AKAPs promote the termination of cAMP signals by recruiting phosphodiesterases and protein phosphatases, and the integration of signaling pathways by binding additional signaling proteins. AKAPs are a heterogeneous family of proteins that only display similarity within their PKA-binding domains, amphipathic helixes docking into a hydrophobic groove formed by the PKA regulatory subunit dimer. This review summarizes the current state of information on compartmentalized cAMP/PKA signaling with a major focus on structural aspects, evolution, diversity, and (patho)physiological functions of AKAPs and intends to outline newly emerging directions of the field, such as the elucidation of AKAP mutations and alterations of AKAP expression in human diseases, and the validation of AKAP-dependent protein-protein interactions as new drug targets. In addition, alternative PKA anchoring mechanisms employed by noncanonical AKAPs and PKA catalytic subunit-interacting proteins are illustrated.
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Chen Q, Weiner RI, Blackman BE. Decreased expression of A-kinase anchoring protein 150 in GT1 neurons decreases neuron excitability and frequency of intrinsic gonadotropin-releasing hormone pulses. Endocrinology 2010; 151:281-90. [PMID: 19887564 PMCID: PMC2803148 DOI: 10.1210/en.2009-0894] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The frequency of intrinsic pulsatile GnRH secretion from endogenous GnRH neurons and GT1 GnRH cell lines is stimulated by increased intracellular cAMP levels. The downstream molecules comprising the cAMP signaling pathway are organized in microdomains by a family of scaffolding proteins, A-kinase anchoring proteins (AKAPs). These molecules tether protein kinase A, cAMP-specific phosphodiesterases, phosphatases to known substrates. In neurons AKAP150 organizes many of the signaling molecules known to regulate the excitability and intrinsic pulsatile activity of GnRH neurons. AKAP150 was expressed in both the GT1-1 and GT1-7 cells. We determined the role of AKAP150 in coordinating GT1-1 cell excitability and intrinsic GnRH pulsatile secretion by lowering AKAP150 levels with a small interfering RNA (siRNA) adenovirus construct to AKAP150 (Ad-AKAP150-siRNA). Infection with Ad-AKAP150-siRNA specifically decreased AKAP150 mRNA levels by 74% and protein levels by 53% relative to uninfected cells or cells infected with a luciferase control adenovirus siRNA vector. In GT1 cells, spontaneous Ca(2+) oscillations, an index of neuron excitability, are stimulated by increased levels of intracellular cAMP and lowered by decreased levels. The frequency of spontaneous Ca(2+) oscillations in Ad-AKAP150-siRNA-treated GT1-1 cells decreased by 47.2% relative to controls. A dramatic decrease in the number of spontaneous GnRH pulses was also observed after infection with Ad-AKAP150-siRNA. The interpulse interval increased to 143 +/- 20.25 min in Ad-AKAP150-siRNA infected cells from 32.2 +/- 7.3 min in luciferase control adenovirus siRNA vector-infected cells. These data demonstrate an important role of AKAP150 in coordinating signaling events regulating the frequency of intrinsic pulsatile GnRH secretion.
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Affiliation(s)
- Qiumei Chen
- Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, California 94143, USA
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30
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Carnegie GK, Means CK, Scott JD. A-kinase anchoring proteins: from protein complexes to physiology and disease. IUBMB Life 2009; 61:394-406. [PMID: 19319965 DOI: 10.1002/iub.168] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Protein scaffold complexes are a key mechanism by which a common signaling pathway can serve many different functions. Sequestering a signaling enzyme to a specific subcellular environment not only ensures that the enzyme is near its relevant targets, but also segregates this activity to prevent indiscriminate phosphorylation of other substrates. One family of diverse, well-studied scaffolding proteins are the A-kinase anchoring proteins (AKAPs). These anchoring proteins form multi-protein complexes that integrate cAMP signaling with other pathways and signaling events. In this review, we focus on recent advances in the elucidation of AKAP function.
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Affiliation(s)
- Graeme K Carnegie
- Department of Pharmacology, Howard Hughes Medical Institute, University of Washington, School of Medicine, Seattle, Washington 98195, USA.
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31
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Scholten A, Aye TT, Heck AJR. A multi-angular mass spectrometric view at cyclic nucleotide dependent protein kinases: in vivo characterization and structure/function relationships. MASS SPECTROMETRY REVIEWS 2008; 27:331-353. [PMID: 18381623 DOI: 10.1002/mas.20166] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Mass spectrometry has evolved in recent years to a well-accepted and increasingly important complementary technique in molecular and structural biology. Here we review the many contributions mass spectrometry based studies have made in recent years in our understanding of the important cyclic nucleotide activated protein kinase A (PKA) and protein kinase G (PKG). We both describe the characterization of kinase isozymes, substrate phosphorylation, binding partners and post-translational modifications by proteomics based methodologies as well as their structural and functional properties as revealed by native mass spectrometry, H/D exchange MS and ion mobility. Combining all these mass spectrometry based data with other biophysical and biochemical data has been of great help to unravel the intricate regulation of kinase function in the cell in all its magnificent complexity.
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Affiliation(s)
- Arjen Scholten
- Biomolecular Mass Spectrometry & Proteomics Group, Utrecht Institute of Pharmaceutical Sciences and Bijvoet Center for Biomolecular Research, Utrecht University, Sorbonnelaan 16, 3584CA, Utrecht, The Netherlands
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32
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Willoughby D, Cooper DMF. Organization and Ca2+Regulation of Adenylyl Cyclases in cAMP Microdomains. Physiol Rev 2007; 87:965-1010. [PMID: 17615394 DOI: 10.1152/physrev.00049.2006] [Citation(s) in RCA: 327] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The adenylyl cyclases are variously regulated by G protein subunits, a number of serine/threonine and tyrosine protein kinases, and Ca2+. In some physiological situations, this regulation can be readily incorporated into a hormonal cascade, controlling processes such as cardiac contractility or neurotransmitter release. However, the significance of some modes of regulation is obscure and is likely only to be apparent in explicit cellular contexts (or stages of the cell cycle). The regulation of many of the ACs by the ubiquitous second messenger Ca2+provides an overarching mechanism for integrating the activities of these two major signaling systems. Elaborate devices have been evolved to ensure that this interaction occurs, to guarantee the fidelity of the interaction, and to insulate the microenvironment in which it occurs. Subcellular targeting, as well as a variety of scaffolding devices, is used to promote interaction of the ACs with specific signaling proteins and regulatory factors to generate privileged domains for cAMP signaling. A direct consequence of this organization is that cAMP will exhibit distinct kinetics in discrete cellular domains. A variety of means are now available to study cAMP in these domains and to dissect their components in real time in live cells. These topics are explored within the present review.
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Affiliation(s)
- Debbie Willoughby
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
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Sandoz G, Thümmler S, Duprat F, Feliciangeli S, Vinh J, Escoubas P, Guy N, Lazdunski M, Lesage F. AKAP150, a switch to convert mechano-, pH- and arachidonic acid-sensitive TREK K(+) channels into open leak channels. EMBO J 2006; 25:5864-72. [PMID: 17110924 PMCID: PMC1698884 DOI: 10.1038/sj.emboj.7601437] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Accepted: 10/16/2006] [Indexed: 11/09/2022] Open
Abstract
TREK channels are unique among two-pore-domain K(+) channels. They are activated by polyunsaturated fatty acids (PUFAs) including arachidonic acid (AA), phospholipids, mechanical stretch and intracellular acidification. They are inhibited by neurotransmitters and hormones. TREK-1 knockout mice have impaired PUFA-mediated neuroprotection to ischemia, reduced sensitivity to volatile anesthetics and altered perception of pain. Here, we show that the A-kinase-anchoring protein AKAP150 is a constituent of native TREK-1 channels. Its binding to a key regulatory domain of TREK-1 transforms low-activity outwardly rectifying currents into robust leak conductances insensitive to AA, stretch and acidification. Inhibition of the TREK-1/AKAP150 complex by Gs-coupled receptors such as serotonin 5HT4sR and noradrenaline beta2AR is as extensive as for TREK-1 alone, but is faster. Inhibition of TREK-1/AKAP150 by Gq-coupled receptors such as serotonin 5HT2bR and glutamate mGluR5 is much reduced when compared to TREK-1 alone. The association of AKAP150 with TREK channels integrates them into a postsynaptic scaffold where both G-protein-coupled membrane receptors (as demonstrated here for beta2AR) and TREK-1 dock simultaneously.
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MESH Headings
- Adaptor Proteins, Signal Transducing/analysis
- Adaptor Proteins, Signal Transducing/metabolism
- Amino Acid Sequence
- Animals
- Arachidonic Acid/metabolism
- COS Cells
- Chlorocebus aethiops
- Dogs
- GTP-Binding Protein alpha Subunits, Gq-G11/metabolism
- Hydrogen-Ion Concentration
- Mice
- Mice, Inbred C57BL
- Molecular Sequence Data
- Oocytes
- Potassium Channels, Tandem Pore Domain/chemistry
- Potassium Channels, Tandem Pore Domain/metabolism
- Protein Binding
- Protein Structure, Tertiary
- Proteomics
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, Cell Surface/metabolism
- Up-Regulation/genetics
- Xenopus
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Affiliation(s)
- Guillaume Sandoz
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097, Institut Paul Hamel, Valbonne, France
| | - Susanne Thümmler
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097, Institut Paul Hamel, Valbonne, France
| | - Fabrice Duprat
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097, Institut Paul Hamel, Valbonne, France
| | - Sylvain Feliciangeli
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097, Institut Paul Hamel, Valbonne, France
| | | | - Pierre Escoubas
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097, Institut Paul Hamel, Valbonne, France
| | - Nicolas Guy
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097, Institut Paul Hamel, Valbonne, France
| | - Michel Lazdunski
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097, Institut Paul Hamel, Valbonne, France
| | - Florian Lesage
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097, Institut Paul Hamel, Valbonne, France
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS UMR6097, Institut Paul Hamel, 660, route des lucioles, 06560 Valbonne, France. Tel.: +33 4 93 95 77 32; Fax: +33 4 93 95 77 32; E-mail:
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Abstract
Voltage-gated potassium channels regulate cell membrane potential and excitability in neurons and other cell types. A precise control of neuronal action potential patterns underlies the basic functioning of the central and peripheral nervous system. This control relies on the adaptability of potassium channel activities. The functional diversity of potassium currents, however, far exceeds the considerable molecular diversity of this class of genes. Potassium current diversity contributes to the specificity of neuronal firing patterns and may be achieved by regulated transcription, RNA splicing, and posttranslational modifications. Another mechanism for regulation of potassium channel activity is through association with interacting proteins and accessory subunits. Here the authors highlight recent work that addresses this growing area of exploration and discuss areas of future investigation.
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Affiliation(s)
- Yan Li
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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35
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Pearman C, Kent W, Bracken N, Hussain M. H-89 inhibits transient outward and inward rectifier potassium currents in isolated rat ventricular myocytes. Br J Pharmacol 2006; 148:1091-8. [PMID: 16799649 PMCID: PMC1752020 DOI: 10.1038/sj.bjp.0706810] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
1. Voltage clamp was used to investigate the effects of N-[2-p-bromo-cinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89), a potent inhibitor of PKA, on transient outward K(+) current (I(to)) and inward rectifying K(+) current (I(K1)) in rat cardiac muscle. 2. Initial experiments, performed using descending voltage ramps, showed that H-89 inhibited both the outward and inward ramp currents in a concentration-dependent manner at concentrations between 5 and 60 micromol l(-1). A similar degree of inhibition was observed when I(to) and I(K1) were recorded using square wave depolarising and hyperpolarising voltage steps, respectively. 3. The IC(50) was 35.8 micromol l(-1) for I(to) and 27.8 micromol l(-1) for I(K1) compared to 5.4 micromol l(-1) for L-type Ca(2+) current (I(Ca)). The Hill coefficients for I(to), I(K1) and I(Ca) were -1.97, -1.60 and -1.21, respectively. In addition to inhibiting I(to) amplitude, H-89 also accelerated the time to peak and the rate of voltage-dependent inactivation so that the time course of I(to) was abbreviated. 4. Paired-pulse protocols were performed to study the effects of H-89 on steady-state activation and inactivation as well as recovery from voltage-dependent inactivation. H-89 produced a concentration-dependent rightward shift in voltage-dependent activation but had no significant effect on steady-state inactivation. Recovery from voltage-dependent inactivation was delayed, although this was only visible at the highest concentration (60 micromol l(-1)) used. In experiments investigating the effects of elevated cyclic AMP, the beta-adrenergic agonist isoprenaline and the phosphatase inhibitor calyculin A had no major effects on I(to) or I(K1). 6. Data suggest that the effects of H-89 on K(+) currents are more complex than simple inhibition of PKA-mediated phosphorylation.
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Affiliation(s)
- Charles Pearman
- School of Clinical Sciences, University of Liverpool, Daulby Street, Liverpool L69 3GA
| | - William Kent
- School of Clinical Sciences, University of Liverpool, Daulby Street, Liverpool L69 3GA
| | - Nicolas Bracken
- School of Clinical Sciences, University of Liverpool, Daulby Street, Liverpool L69 3GA
| | - Munir Hussain
- School of Clinical Sciences, University of Liverpool, Daulby Street, Liverpool L69 3GA
- Author for correspondence:
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Willoughby D, Wong W, Schaack J, Scott JD, Cooper DMF. An anchored PKA and PDE4 complex regulates subplasmalemmal cAMP dynamics. EMBO J 2006; 25:2051-61. [PMID: 16642035 PMCID: PMC1462982 DOI: 10.1038/sj.emboj.7601113] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2005] [Accepted: 04/03/2006] [Indexed: 01/28/2023] Open
Abstract
The spatiotemporal regulation of cAMP can generate microdomains just beneath the plasma membrane where cAMP increases are larger and more dynamic than those seen globally. Real-time measurements of cAMP using mutant cyclic nucleotide-gated ion channel biosensors, pharmacological tools and RNA interference (RNAi) were employed to demonstrate a subplasmalemmal cAMP signaling module in living cells. Transient cAMP increases were observed upon stimulation of HEK293 cells with prostaglandin E1. However, pretreatment with selective inhibitors of type 4 phosphodiesterases (PDE4), protein kinase A (PKA) or PKA/A-kinase anchoring protein (AKAP) interaction blocked an immediate return of subplasmalemmal cAMP to basal levels. Knockdown of specific membrane-associated AKAPs using RNAi identified gravin (AKAP250) as the central organizer of the PDE4 complex. Co-immunoprecipitation confirmed that gravin maintains a signaling complex that includes PKA and PDE4D. We propose that gravin-associated PDE4D isoforms provide a means to rapidly terminate subplasmalemmal cAMP signals with concomitant effects on localized ion channels or enzyme activities.
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Affiliation(s)
| | - Wei Wong
- Howard Hughes Medical Institute/Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Jerome Schaack
- Department of Microbiology, Program in Molecular Biology, and University of Colorado Cancer Center, University of Colorado Health Sciences Center, Denver, CO, USA
| | - John D Scott
- Howard Hughes Medical Institute/Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Dermot M F Cooper
- Department of Pharmacology, University of Cambridge, Cambridge, UK
- Department of Pharmacology, Tennis Court Road, University of Cambridge, Cambridge CB2 1QJ, UK. Tel.: +44 1223 334063; Fax: +44 1223 334040; E-mail:
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37
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Mignen O, Thompson JL, Shuttleworth TJ. Arachidonate-regulated Ca2+-selective (ARC) channel activity is modulated by phosphorylation and involves an A-kinase anchoring protein. J Physiol 2005; 567:787-98. [PMID: 15994185 PMCID: PMC1474237 DOI: 10.1113/jphysiol.2005.090209] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In many non-excitable cells, the predominant mode of agonist-activated Ca(2+) entry switches from the arachidonic acid-regulated Ca(2+) (ARC) channels at low agonist concentrations, to store-operated channels at high concentrations. Underlying this process is the inhibition of the ARC channels by a calcineurin-mediated dephosphorylation, which inhibits the ability of arachidonic acid to activate the channels. Following such a dephosphorylation, we found that restoration of the sensitivity of the ARC channels to arachidonic acid, as well as to low concentrations of carbachol, was specifically dependent on protein kinase A (PKA) activity. Inhibition of protein kinase C, protein kinase G or calmodulin-activated kinase had no effect. This action of PKA was unaffected by prolonged intracellular dialysis, whilst disruption of the binding of PKA to A-kinase anchoring proteins (AKAPs) inhibited currents through ARC channels, and blocked the PKA-dependent effects. AKAP79, a protein which scaffolds both PKA and calcineurin, was shown to be present in the cells. These data illustrate the significance of PKA-dependent phosphorylation and calcineurin-dependent dephosphorylation in the overall regulation of ARC channel activity, and indicate the key role of an AKAP, possibly AKAP79, in the spatial organization these processes.
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Affiliation(s)
- Olivier Mignen
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA
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38
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Romanenko VG, Fang Y, Byfield F, Travis AJ, Vandenberg CA, Rothblat GH, Levitan I. Cholesterol sensitivity and lipid raft targeting of Kir2.1 channels. Biophys J 2004; 87:3850-61. [PMID: 15465867 PMCID: PMC1304896 DOI: 10.1529/biophysj.104.043273] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
This study investigates how changes in the level of cellular cholesterol affect inwardly rectifying K+ channels belonging to a family of strong rectifiers (Kir2). In an earlier study we showed that an increase in cellular cholesterol suppresses endogenous K+ current in vascular endothelial cells, presumably due to effects on underlying Kir2.1 channels. Here we show that, indeed, cholesterol increase strongly suppressed whole-cell Kir2.1 current when the channels were expressed in a null cell line. However, cholesterol level had no effect on the unitary conductance and only little effect on the open probability of the channels. Moreover, no cholesterol effect was observed either on the total level of Kir2.1 protein or on its surface expression. We suggest, therefore, that cholesterol modulates not the total number of Kir2.1 channels in the plasma membrane but rather the transition of the channels between active and silent states. Comparing the effects of cholesterol on members of the Kir2.x family shows that Kir2.1 and Kir2.2 have similar high sensitivity to cholesterol, Kir2.3 is much less sensitive, and Kir2.4 has an intermediate sensitivity. Finally, we show that Kir2.x channels partition virtually exclusively into Triton-insoluble membrane fractions indicating that the channels are targeted into cholesterol-rich lipid rafts.
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Affiliation(s)
- Victor G Romanenko
- Institute for Medicine and Engineering, Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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39
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Correia MJ, Wood TG, Prusak D, Weng T, Rennie KJ, Wang HQ. Molecular characterization of an inward rectifier channel (IKir) found in avian vestibular hair cells: cloning and expression of pKir2.1. Physiol Genomics 2004; 19:155-69. [PMID: 15316115 DOI: 10.1152/physiolgenomics.00096.2004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A fast inwardly rectifying current has been observed in some of the sensory cells (hair cells) of the inner ear of several species. While the current was presumed to be an IKir current, contradictory evidence existed as to whether the cloned channel actually belonged to the Kir2.0 subfamily of potassium inward rectifiers. In this paper, we report for the first time converging evidence from electrophysiological, biochemical, immunohistochemical, and genetic studies that show that the Kir2.1 channel carries the fast inwardly rectifying currents found in pigeon vestibular hair cells. Following cytoplasm extraction from single type II and multiple pigeon vestibular hair cells, mRNA was reverse transcribed, amplified, and sequenced. The open reading frame (ORF), consisting of a 1,284-bp nucleotide sequence, showed 94, 85, and 83% identity with Kir2.1 subunit sequences from chick lens, Kir2 sequences from human heart, and a mouse macrophage cell line, respectively. Phylogenetic analyses revealed that pKir2.1 formed an immediate node with hKir2.1 but not with hKir2.2-2.4. Hair cells (type I and type II) and supporting cells in the sensory epithelium reacted positively with a Kir2.1 antibody. The whole cell current recorded in oocytes and CHO cells, transfected with pigeon hair cell Kir2.1 (pKir2.1), demonstrated blockage by Ba2+ and sensitivity to changing K+ concentration. The mean single-channel linear slope conductance in transfected CHO cells was 29 pS. The open dwell time was long (approximately 300 ms at -100 mV), and the closed dwell time was short (approximately 34 ms at -100 mV). Multistates ranging from 3-6 were noted in some single-channel responses. All of the above features have been described for other Kir2.1 channels. Current clamp studies of native pigeon vestibular hair cells illustrated possible physiological roles of the channel and showed that blockage of the channel by Ba2+ depolarized the resting membrane potential by approximately 30 mV. Negative currents hyperpolarized the membrane approximately 20 mV before block but approximately 60 mV following block. RT-PCR studies revealed that the pKir2.1 channels found in pigeon vestibular hair cells were also present in pigeon vestibular nerve, vestibular ganglion, lens, neck muscle, brain (brain stem, cerebellum and optic tectum), liver, and heart.
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Affiliation(s)
- Manning J Correia
- Department of Otolaryngology, University of Texas Medical Branch, Galveston, Texas 77555-1063, USA.
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40
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Leyland ML, Dart C. An alternatively spliced isoform of PSD-93/chapsyn 110 binds to the inwardly rectifying potassium channel, Kir2.1. J Biol Chem 2004; 279:43427-36. [PMID: 15304517 DOI: 10.1074/jbc.m407575200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Inwardly rectifying potassium (Kir) channels are prime determinants of resting membrane potential in neurons. Their subcellular distribution and surface density thus help shape neuronal excitability, yet mechanisms governing the membrane targeting and localization of Kir channels are poorly understood. Here we report a direct interaction between the strong inward rectifier, Kir2.1, and a recently identified splice variant of postsynaptic density-93 (PSD-93), a protein involved the subcellular targeting of ion channels and glutamate receptors at excitatory synapses. Yeast two-hybrid screening of a human brain cDNA library using the carboxyl terminus of Kir2.1 as bait yielded cDNA encoding the first two PDZ domains of PSD-93, but with an extended N-terminal region that diverged from other PSD-93 isoforms. This clone represented the human homologue of the mouse PSD-93 splice variant, PSD-93delta. Reverse transcription-polymerase chain reaction analysis showed diffuse low level PSD-93delta expression throughout the brain, with significantly higher levels in spinal cord. In vitro binding studies revealed that a type I PDZ recognition motif at the extreme C terminus of the Kir2.1 mediates interaction with all three PDZ domains of PSD-93delta, and association between Kir2 channels and PSD-93delta was confirmed further by the ability of anti-Kir2.1 antibodies to coimmunoprecipitate PSD-93delta from rat spinal cord lysates. Functionally, coexpression of Kir2.1 and PSD-93delta had no discernible effect upon channel kinetics but resulted in cell surface Kir2.1 clustering and suppression of channel internalization. We conclude that PSD-93delta is potentially an important regulator of the spatial and temporal distribution of Kir2 channels within neuronal membranes of the central nervous system.
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Affiliation(s)
- Mark L Leyland
- Department of Biochemistry, University of Leicester, PO Box 138, LE1 9HN, UK.
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41
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Malbon CC, Tao J, Wang HY. AKAPs (A-kinase anchoring proteins) and molecules that compose their G-protein-coupled receptor signalling complexes. Biochem J 2004; 379:1-9. [PMID: 14715081 PMCID: PMC1224059 DOI: 10.1042/bj20031648] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2003] [Revised: 12/08/2003] [Accepted: 01/09/2004] [Indexed: 11/17/2022]
Abstract
Cell signalling mediated via GPCRs (G-protein-coupled receptors) is a major paradigm in biology, involving the assembly of receptors, G-proteins, effectors and downstream elements into complexes that approach in design 'solid-state' signalling devices. Scaffold molecules, such as the AKAPs (A-kinase anchoring proteins), were discovered more than a decade ago and represent dynamic platforms, enabling multivalent signalling. AKAP79 and AKAP250 were the first to be shown to bind to membrane-embedded GPCRs, orchestrating the interactions of various protein kinases (including tyrosine kinases), protein phosphatases (e.g. calcineurin) and cytoskeletal elements with at least one member of the superfamily of GPCRs, the prototypical beta2-adrenergic receptor. In this review, the multivalent interactions of AKAP250 with the cell membrane, receptor, cytoskeleton and constituent components are detailed, providing a working model for AKAP-based GPCR signalling complexes. Dynamic regulation of the AKAP-receptor complex is mediated by ordered protein phosphorylation.
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Affiliation(s)
- Craig C Malbon
- Department of Molecular Pharmacology, University Medical Center, Stony Brook University, Stony Brook, NY 11794-8651, USA.
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42
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Bauman AL, Goehring AS, Scott JD. Orchestration of synaptic plasticity through AKAP signaling complexes. Neuropharmacology 2004; 46:299-310. [PMID: 14975685 DOI: 10.1016/j.neuropharm.2003.09.016] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2003] [Accepted: 09/16/2003] [Indexed: 11/20/2022]
Abstract
Significant progress has been made toward understanding the mechanisms by which organisms learn from experiences and how those experiences are translated into memories. Advances in molecular, electrophysiological and genetic technologies have permitted great strides in identifying biochemical and structural changes that occur at synapses during processes that are thought to underlie learning and memory. Cellular events that generate the second messenger cyclic AMP (cAMP) and activate protein kinase A (PKA) have been linked to synaptic plasticity and long-term memory. In this review we will focus on the role of PKA in synaptic plasticity and discuss how the compartmentalization of PKA through its association with A-Kinase Anchoring Proteins (AKAPs) affect PKA function in this process.
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Affiliation(s)
- Andrea L Bauman
- Howard Hughes Medical Institute, Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
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43
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Abstract
Background and Purpose—
It is not known whether cerebral vasoprotective mechanisms in females include increased function of arterial K
+
channels. We hypothesized that vasodilator responses mediated by activation of inwardly rectifying K
+
(K
IR
) channels are greater in cerebral arteries of female versus male rats and that this is due to the effects of estrogen.
Methods—
Changes in basilar artery diameter were measured with a cranial window preparation in anesthetized Sprague-Dawley rats.
Results—
K
+
(5 and 10 mmol/L) caused greater vasodilatation in females (percent maximum, 21±3% and 58±7%, respectively) versus males (11±1% and 37±4%, respectively;
P
<0.05). In contrast, vasodilator responses to aprikalim (1 and 3 μmol/L) or acetylcholine (ACh, 1 and 10 μmol/L) did not differ between the genders. The selective K
IR
channel inhibitor barium ion (30 μmol/L) decreased basilar artery diameter in males but not females (−7±1% versus −2±1%,
P
<0.05) and selectively inhibited K
+
-induced vasodilatation by ≈50% in both groups. Ovariectomy of female rats resulted in smaller vasodilator effects of K
+
, and chronic treatment of these rats with 17β-estradiol (0.01 mg/kg per day for 7 days) normalized K+-induced vasodilatation. Furthermore, the selective M2 muscarinic ACh receptor antagonist methoctramine (1 μmol/L) increased responses to K
+
in males to levels equivalent to responses in females but had no effect on responses to K
+
in females.
Conclusions—
K
+
is a more powerful vasodilator in the female versus male cerebral circulation. This difference is estrogen dependent and could be due to a lack of M2 muscarinic ACh receptor–induced inhibition of K
IR
channel activation by K
+
in female cerebral arteries.
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44
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Donaldson MR, Yoon G, Fu YH, Ptacek LJ. Andersen-Tawil syndrome: a model of clinical variability, pleiotropy, and genetic heterogeneity. Ann Med 2004; 36 Suppl 1:92-7. [PMID: 15176430 DOI: 10.1080/17431380410032490] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Due to its varied and variable phenotypes, Andersen-Tawil syndrome (ATS) holds a unique place in the field of channelopathies. Patients with ATS typically present with the triad of periodic paralysis, cardiac arrhythmias, and developmental dysmorphisms. Although penetrance of ATS is high, disease expression and severity are remarkably variable. Mutations in KCNJ2 are the primary cause of ATS with 21 mutations discovered in 30 families. These mutations affect channel function through heterogeneous mechanisms, including reduced PIP2-related channel activation and altered pore function. Aside from KCNJ2-based ATS, the genetic basis of this disease in nearly 40% of cases is unknown. Other ATS genes likely share a common pathway or function with Kir2.1 or facilitate the activity of this ion channel. In this review, we explore hypotheses explaining the pathogenesis, expression, and variability of ATS.
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Affiliation(s)
- Matthew R Donaldson
- Department of Human Molecular Biology and Genetics, University of Utah, Salt Lake City, USA
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45
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Sampson LJ, Leyland ML, Dart C. Direct interaction between the actin-binding protein filamin-A and the inwardly rectifying potassium channel, Kir2.1. J Biol Chem 2003; 278:41988-97. [PMID: 12923176 DOI: 10.1074/jbc.m307479200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The role of filamins in actin cross-linking and membrane stabilization is well established, but recently their ability to interact with a variety of transmembrane receptors and signaling proteins has led to speculation of additional roles in scaffolding and signal transduction. Here we report a direct interaction between filamin-A and Kir2.1, an isoform of inwardly rectifying potassium channel expressed in vascular smooth muscle and an important regulator of vascular tone. Yeast two-hybrid screening of a porcine coronary artery cDNA library using the carboxyl terminus of Kir2.1 as bait yielded cDNA encoding a fragment of filamin-A (residues 2481-2647). Interaction between filamin-A and Kir2.1 was confirmed by in vitro overlay assay of membrane-bound Kir2.1 with glutathione S-transferase fusion protein of the isolated filamin clone. Additionally, antibodies directed against Kir2.1 coimmunoprecipitated filamin-A from arterial smooth muscle cell lysates, and immunocytochemical analysis of individual arterial smooth muscle cells showed that Kir2.1 and filamin co-localize in "hotspots" at the cell membrane. Interaction with filamin-A was found to have no effect on Kir2.1 channel behavior but, rather, increased the number of functional channels resident within the membrane. We conclude that filamin-A is potentially an important regulator of Kir2.1 surface expression and location within vascular smooth muscle.
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Affiliation(s)
- Laura J Sampson
- Department of Cell Physiology and Pharmacology, University of Leicester, P. O. Box 138, Leicester LE1 9HN, United Kingdom.
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46
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Bacallao RL, Yu W, Dunn KW, Phillips CL. Novel light microscopy imaging techniques in nephrology. Curr Opin Nephrol Hypertens 2003; 12:455-61. [PMID: 12815343 DOI: 10.1097/00041552-200307000-00015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW As more genomes are sequenced, the difficult task of characterizing the gene products of these genomes becomes the compelling mission of biological sciences. The melding of whole organ physiology with transgenic animal models, gene transfer methods and RNA silencing promises to form the next wave of scientific inquiry. A host of new microscopy imaging technologies enables researchers to directly visualize gene products, probe alterations in cell function in transgenic animals and map tissue organization. This review will describe these microscopy imaging techniques, their advantages, imaging properties and limitations. RECENT FINDINGS New optical methods such as two-photon confocal microscopy, fluorescence resonance energy transfer, and total internal fluorescence reflectance microscopy are increasingly being applied to extend our understanding of whole organ and renal epithelial function. Two-photon confocal microscopy has been used to image directly into the kidney of living animals. Fluorescence resonance energy transfer has been used to directly visualize transcription factor complexes within the nucleus while total internal fluorescence reflectance microscopy has permitted direct observation of protein delivery to the plasma membrane. SUMMARY The application of these optical techniques along with the ability to label virtually any protein with a fluorescent tag will enable researchers to study cellular processes and whole organ function in vivo. Light microscopy methods will allow an advance from semi-quantitative to quantitative approaches to problems of relevance to physiologists studying issues related to renal function.
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Affiliation(s)
- Robert L Bacallao
- Division of Nephrology, Richard Roudebush VAMC and Indiana University School of Medicine, Indianapolis, Indiana, USA
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47
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Affiliation(s)
- Graeme K Carnegie
- Howard Hughes Medical Institute, Vollum Institute, Oregon Health and Sciences University, Portland, Oregon 97201, USA
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48
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Stanfield PR, Nakajima S, Nakajima Y. Constitutively active and G-protein coupled inward rectifier K+ channels: Kir2.0 and Kir3.0. Rev Physiol Biochem Pharmacol 2002; 145:47-179. [PMID: 12224528 DOI: 10.1007/bfb0116431] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Peter R Stanfield
- Molecular Physiology Group, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK
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49
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Lopes CMB, Zhang H, Rohacs T, Jin T, Yang J, Logothetis DE. Alterations in conserved Kir channel-PIP2 interactions underlie channelopathies. Neuron 2002; 34:933-44. [PMID: 12086641 DOI: 10.1016/s0896-6273(02)00725-0] [Citation(s) in RCA: 315] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Inwardly rectifying K(+) (Kir) channels are important regulators of resting membrane potential and cell excitability. The activity of Kir channels is critically dependent on the integrity of channel interactions with phosphatidylinositol 4,5-bisphosphate (PIP(2)). Here we identify and characterize channel-PIP(2) interactions that are conserved among Kir family members. We find basic residues that interact with PIP(2), two of which have been associated with Andersen's and Bartter's syndromes. We show that several naturally occurring mutants decrease channel-PIP(2) interactions, leading to disease.
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Affiliation(s)
- Coeli M B Lopes
- Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York University, New York, NY 10029, USA
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50
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Hoger JH, Ilyin VI, Forsyth S, Hoger A. Shear stress regulates the endothelial Kir2.1 ion channel. Proc Natl Acad Sci U S A 2002; 99:7780-5. [PMID: 12032360 PMCID: PMC124350 DOI: 10.1073/pnas.102184999] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2001] [Accepted: 03/29/2002] [Indexed: 11/18/2022] Open
Abstract
Endothelial cells (ECs) line the mammalian vascular system and respond to the hemodynamic stimulus of fluid shear stress, the frictional force produced by blood flow. When ECs are exposed to shear stress, one of the fastest responses is an increase of K(+) conductance, which suggests that ion channels are involved in the early shear stress response. Here we show that an applied shear stress induces a K(+) ion current in cells expressing the endothelial Kir2.1 channel. This ion current shares the properties of the shear-induced current found in ECs. In addition, the shear current induction can be specifically prevented by tyrosine kinase inhibition. Our findings identify the Kir2.1 channel as an early component of the endothelial shear response mechanism.
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Affiliation(s)
- Jeff H Hoger
- Hitachi Chemical Research Center, Irvine, CA 92612, USA.
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