1
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Souri F, Badavi M, Dianat M, Mard A, Sarkaki A, Razliqi RN. The protective effects of gallic acid and SGK1 inhibitor on cardiac damage and genes involved in Ca2+ homeostasis in an isolated heart model of ischemia/reperfusion injury in rat. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2024; 397:5207-5217. [PMID: 38252301 DOI: 10.1007/s00210-024-02949-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 01/10/2024] [Indexed: 01/23/2024]
Abstract
Serum and glucocorticoid-induced kinase 1 (SGK1) is an enzyme that may play a vital role in myocardial ischemia/reperfusion (I/R) injury. This enzyme may affect sarcoplasmic reticulum Ca2+ ATPase (SERCA2), ryanodine receptor (RyR2) and sodium/calcium exchanger (NCX1) during myocardial ischemia/reperfusion injury. The objective of this investigation was to analyze the effects of the combination of GSK650394 (SGK1 inhibitor) and gallic acid on the calcium ions regulation, inflammation, and cardiac dysfunction resulting from ischemia/reperfusion (I/R) injury in the heart. Sixty male Wistar rats were randomly divided into six groups, pretreated with gallic acid or vehicle for 10 days. Then the heart was isolated and exposed to I/R. In the SGK1 inhibitor groups, GSK650394 was infused 5 min before ischemia induction. After that, Ca2+ homeostasis, inflammatory factors, cardiac function, antioxidant activity, and myocardial damage were evaluated. The findings suggested that the use of two drugs in combination therapy produced more significant improvements in left ventricular end diastolic pressure, left ventricular systolic pressure, RR-interval, ST-elevation, inflammation factors, and antioxidant enzymes activity as compared to the use of each drug. Despite this, there was a significant decrease observed in heart marker enzymes (including lactate dehydrogenase (LDH), troponin-I (cTn-I), creatine kinase-MB (CK-MB) and creatine phosphokinase (CPK) when compared to the ischemic group. Additionally, the expression of RyR2, NCX1, and SERCA2 genes showed a noteworthy increase as compared to the ischemic group. The findings of this study propose that using both of these agents on myocardial I/R injury could have superior advantages compared to using only one of them.
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Affiliation(s)
- Faramarz Souri
- Student Research Committee, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Mohammad Badavi
- The Persian Gulf Physiology Research Center, Medical Basic Sciences Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
| | - Mahin Dianat
- The Persian Gulf Physiology Research Center, Medical Basic Sciences Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Ali Mard
- The Persian Gulf Physiology Research Center, Medical Basic Sciences Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Alireza Sarkaki
- The Persian Gulf Physiology Research Center, Medical Basic Sciences Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Reza Noei Razliqi
- Student Research Committee, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
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2
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Structure-Based Function and Regulation of NCX Variants: Updates and Challenges. Int J Mol Sci 2022; 24:ijms24010061. [PMID: 36613523 PMCID: PMC9820601 DOI: 10.3390/ijms24010061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Revised: 12/14/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022] Open
Abstract
The plasma-membrane homeostasis Na+/Ca2+ exchangers (NCXs) mediate Ca2+ extrusion/entry to dynamically shape Ca2+ signaling/in biological systems ranging from bacteria to humans. The NCX gene orthologs, isoforms, and their splice variants are expressed in a tissue-specific manner and exhibit nearly 104-fold differences in the transport rates and regulatory specificities to match the cell-specific requirements. Selective pharmacological targeting of NCX variants could benefit many clinical applications, although this intervention remains challenging, mainly because a full-size structure of eukaryotic NCX is unavailable. The crystal structure of the archaeal NCX_Mj, in conjunction with biophysical, computational, and functional analyses, provided a breakthrough in resolving the ion transport mechanisms. However, NCX_Mj (whose size is nearly three times smaller than that of mammalian NCXs) cannot serve as a structure-dynamic model for imitating high transport rates and regulatory modules possessed by eukaryotic NCXs. The crystal structures of isolated regulatory domains (obtained from eukaryotic NCXs) and their biophysical analyses by SAXS, NMR, FRET, and HDX-MS approaches revealed structure-based variances of regulatory modules. Despite these achievements, it remains unclear how multi-domain interactions can decode and integrate diverse allosteric signals, thereby yielding distinct regulatory outcomes in a given ortholog/isoform/splice variant. This article summarizes the relevant issues from the perspective of future developments.
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3
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The Contribution of Lipotoxicity to Diabetic Kidney Disease. Cells 2022; 11:cells11203236. [PMID: 36291104 PMCID: PMC9601125 DOI: 10.3390/cells11203236] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/02/2022] [Accepted: 10/12/2022] [Indexed: 11/17/2022] Open
Abstract
Lipotoxicity is a fundamental pathophysiologic mechanism in diabetes and non-alcoholic fatty liver disease and is now increasingly recognized in diabetic kidney disease (DKD) pathogenesis. This review highlights lipotoxicity pathways in the podocyte and proximal tubule cell, which are arguably the two most critical sites in the nephron for DKD. The discussion focuses on membrane transporters and lipid droplets, which represent potential therapeutic targets, as well as current and developing pharmacologic approaches to reduce renal lipotoxicity.
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4
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Gök C, Robertson AD, Fuller W. Insulin-induced palmitoylation regulates the Cardiac Na+/Ca2+ exchanger NCX1. Cell Calcium 2022; 104:102567. [DOI: 10.1016/j.ceca.2022.102567] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 02/20/2022] [Accepted: 02/22/2022] [Indexed: 11/02/2022]
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5
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Ottolia M, John S, Hazan A, Goldhaber JI. The Cardiac Na + -Ca 2+ Exchanger: From Structure to Function. Compr Physiol 2021; 12:2681-2717. [PMID: 34964124 DOI: 10.1002/cphy.c200031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Ca2+ homeostasis is essential for cell function and survival. As such, the cytosolic Ca2+ concentration is tightly controlled by a wide number of specialized Ca2+ handling proteins. One among them is the Na+ -Ca2+ exchanger (NCX), a ubiquitous plasma membrane transporter that exploits the electrochemical gradient of Na+ to drive Ca2+ out of the cell, against its concentration gradient. In this critical role, this secondary transporter guides vital physiological processes such as Ca2+ homeostasis, muscle contraction, bone formation, and memory to name a few. Herein, we review the progress made in recent years about the structure of the mammalian NCX and how it relates to function. Particular emphasis will be given to the mammalian cardiac isoform, NCX1.1, due to the extensive studies conducted on this protein. Given the degree of conservation among the eukaryotic exchangers, the information highlighted herein will provide a foundation for our understanding of this transporter family. We will discuss gene structure, alternative splicing, topology, regulatory mechanisms, and NCX's functional role on cardiac physiology. Throughout this article, we will attempt to highlight important milestones in the field and controversial topics where future studies are required. © 2021 American Physiological Society. Compr Physiol 12:1-37, 2021.
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Affiliation(s)
- Michela Ottolia
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Scott John
- Department of Medicine (Cardiology), UCLA, Los Angeles, California, USA
| | - Adina Hazan
- Smidt Heart Institute, Cedars Sinai Medical Center, Los Angeles, California, USA
| | - Joshua I Goldhaber
- Smidt Heart Institute, Cedars Sinai Medical Center, Los Angeles, California, USA
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6
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Durak A, Akkus E, Canpolat AG, Tuncay E, Corapcioglu D, Turan B. Glucagon-like peptide-1 receptor agonist treatment of high carbohydrate intake-induced metabolic syndrome provides pleiotropic effects on cardiac dysfunction through alleviations in electrical and intracellular Ca 2+ abnormalities and mitochondrial dysfunction. Clin Exp Pharmacol Physiol 2021; 49:46-59. [PMID: 34519087 DOI: 10.1111/1440-1681.13590] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 09/07/2021] [Accepted: 09/10/2021] [Indexed: 02/06/2023]
Abstract
The pleiotropic effects of glucagon-like peptide-1 receptor (GLP-1R) agonists on the heart have been recognised in obese or diabetic patients. However, little is known regarding the molecular mechanisms of these agonists in cardioprotective actions under metabolic disturbances. We evaluated the effects of GLP-1R agonist liraglutide treatment on left ventricular cardiomyocytes from high-carbohydrate induced metabolic syndrome rats (MetS rats), characterised with insulin resistance and cardiac dysfunction with a long-QT. Liraglutide (0.3 mg/kg for 4 weeks) treatment of MetS rats significantly reversed long-QT, through a shortening the prolonged action potential duration and recovering inhibited K+ -currents. We also determined a significant recovery in the leaky sarcoplasmic reticulum (SR) and high cytosolic Ca2+ -level, which are confirmed with a full recovery in activated Na+ /Ca2+ -exchanger currents (INCX ). Moreover, the liraglutide treatment significantly reversed the depolarised mitochondrial membrane potential (MMP), increased production of oxidant markers, and cellular acidification together with the depressed ATP production. Our light microscopy analysis of isolated cardiomyocytes showed marked recoveries in the liraglutide-treated MetS group such as marked reverses in highly dilated T-tubules and SR-mitochondria junctions. Moreover, we determined a significant increase in depressed GLUT4 protein level in liraglutide-treated MetS group, possibly associated with recovery in casein kinase 2α. Overall, the study demonstrated a molecular mechanism of liraglutide-induced cardioprotection in MetS rats, at most, via its pleiotropic effects, such as alleviation in the electrical abnormalities, Ca2+ -homeostasis, and mitochondrial dysfunction in ventricular cardiomyocytes.
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Affiliation(s)
- Aysegul Durak
- Faculty of Medicine, Department of Biophysics, Ankara University, Ankara, Turkey
| | - Erman Akkus
- Faculty of Medicine, Department of Internal Medicine, Ankara University, Ankara, Turkey
| | - Asena Gokcay Canpolat
- Faculty of Medicine, Department of Endocrinology and Metabolism, Ankara University, Ankara, Turkey
| | - Erkan Tuncay
- Faculty of Medicine, Department of Biophysics, Ankara University, Ankara, Turkey
| | - Demet Corapcioglu
- Faculty of Medicine, Department of Endocrinology and Metabolism, Ankara University, Ankara, Turkey
| | - Belma Turan
- Faculty of Medicine, Department of Biophysics, Ankara University, Ankara, Turkey.,Faculty of Medicine, Department of Biophysics, Lokman Hekim University, Ankara, Turkey
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7
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Wang W, Wei Q, Zhang J, Zhang M, Wang C, Qu R, Wang Y, Yang G, Wang J. A Ratiometric Fluorescent Biosensor Reveals Dynamic Regulation of Long‐Chain Fatty Acyl‐CoA Esters Metabolism. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202101731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Weibo Wang
- State Key Laboratory of Natural and Biomimetic Drugs Department of Chemical Biology School of Pharmaceutical Sciences Peking University Beijing 100191 China
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education International Joint Research Center for Intelligent Biosensor Technology and Health College of Chemistry Central China Normal University Wuhan 430079 China
| | - Qingpeng Wei
- State Key Laboratory of Natural and Biomimetic Drugs Department of Chemical Biology School of Pharmaceutical Sciences Peking University Beijing 100191 China
| | - Jiayuan Zhang
- Wellcome Centre for Human Genetics University of Oxford Roosevelt Dr, Headington Oxford OX3 7BN UK
| | - Meiqi Zhang
- State Key Laboratory of Natural and Biomimetic Drugs Department of Chemical Biology School of Pharmaceutical Sciences Peking University Beijing 100191 China
| | - Chuchen Wang
- State Key Laboratory of Natural and Biomimetic Drugs Department of Chemical Biology School of Pharmaceutical Sciences Peking University Beijing 100191 China
| | - Renyu Qu
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education International Joint Research Center for Intelligent Biosensor Technology and Health College of Chemistry Central China Normal University Wuhan 430079 China
| | - Yuan Wang
- State Key Laboratory of Natural and Biomimetic Drugs Department of Chemical Biology School of Pharmaceutical Sciences Peking University Beijing 100191 China
| | - Guangfu Yang
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education International Joint Research Center for Intelligent Biosensor Technology and Health College of Chemistry Central China Normal University Wuhan 430079 China
| | - Jing Wang
- State Key Laboratory of Natural and Biomimetic Drugs Department of Chemical Biology School of Pharmaceutical Sciences Peking University Beijing 100191 China
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8
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Wang W, Wei Q, Zhang J, Zhang M, Wang C, Qu R, Wang Y, Yang G, Wang J. A Ratiometric Fluorescent Biosensor Reveals Dynamic Regulation of Long-Chain Fatty Acyl-CoA Esters Metabolism. Angew Chem Int Ed Engl 2021; 60:13996-14004. [PMID: 33837610 DOI: 10.1002/anie.202101731] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 03/14/2021] [Indexed: 01/28/2023]
Abstract
Despite increasing awareness of the biological impacts of long-chain fatty acyl-CoA esters (LCACoAs), our knowledge about the subcellular distribution and regulatory functions of these acyl-CoA molecules is limited by a lack of methods for detecting LCACoAs in living cells. Here, we report development of a genetically encoded fluorescent sensor that enables ratiometric quantification of LCACoAs in living cells and subcellular compartments. We demonstrate how this FadR-cpYFP fusion "LACSer sensor" undergoes LCACoA-induced conformational changes reflected in easily detectable fluorescence responses, and show proof-of-concept for real-time monitoring of LCACoAs in human cells. Subsequently, we applied LACSer in scientific studies investigating how disruption of ACSL enzymes differentially reduces cytosolic and mitochondrial LCACoA levels, and show how genetic disruption of an acyl-CoA binding protein (ACBP) alters mitochondrial accumulation of LCACoAs.
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Affiliation(s)
- Weibo Wang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China.,Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, International Joint Research Center for Intelligent Biosensor Technology and Health, College of Chemistry, Central China Normal University, Wuhan, 430079, China
| | - Qingpeng Wei
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
| | - Jiayuan Zhang
- Wellcome Centre for Human Genetics, University of Oxford, Roosevelt Dr, Headington, Oxford, OX3 7BN, UK
| | - Meiqi Zhang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
| | - Chuchen Wang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
| | - Renyu Qu
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, International Joint Research Center for Intelligent Biosensor Technology and Health, College of Chemistry, Central China Normal University, Wuhan, 430079, China
| | - Yuan Wang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
| | - Guangfu Yang
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, International Joint Research Center for Intelligent Biosensor Technology and Health, College of Chemistry, Central China Normal University, Wuhan, 430079, China
| | - Jing Wang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
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9
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Varró A, Tomek J, Nagy N, Virág L, Passini E, Rodriguez B, Baczkó I. Cardiac transmembrane ion channels and action potentials: cellular physiology and arrhythmogenic behavior. Physiol Rev 2020; 101:1083-1176. [PMID: 33118864 DOI: 10.1152/physrev.00024.2019] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Cardiac arrhythmias are among the leading causes of mortality. They often arise from alterations in the electrophysiological properties of cardiac cells and their underlying ionic mechanisms. It is therefore critical to further unravel the pathophysiology of the ionic basis of human cardiac electrophysiology in health and disease. In the first part of this review, current knowledge on the differences in ion channel expression and properties of the ionic processes that determine the morphology and properties of cardiac action potentials and calcium dynamics from cardiomyocytes in different regions of the heart are described. Then the cellular mechanisms promoting arrhythmias in congenital or acquired conditions of ion channel function (electrical remodeling) are discussed. The focus is on human-relevant findings obtained with clinical, experimental, and computational studies, given that interspecies differences make the extrapolation from animal experiments to human clinical settings difficult. Deepening the understanding of the diverse pathophysiology of human cellular electrophysiology will help in developing novel and effective antiarrhythmic strategies for specific subpopulations and disease conditions.
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Affiliation(s)
- András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - Jakub Tomek
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Elisa Passini
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Blanca Rodriguez
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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10
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FATP2-targeted therapies - A role beyond fatty liver disease. Pharmacol Res 2020; 161:105228. [PMID: 33027714 DOI: 10.1016/j.phrs.2020.105228] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 09/26/2020] [Accepted: 09/27/2020] [Indexed: 12/31/2022]
Abstract
Fatty acid transport protein 2 (FATP2) is a multifunctional protein whose specific function is determined by the type of located cell, its intracellular location, or organelle-specific interactions. In the different diseases setting, a newfound appreciation for the biological function of FATP2 has come into view. Two main functions of FATP2 are to activate long-chain fatty acids (LCFAs) as a very long-chain acyl-coenzyme A (CoA) synthetase (ACSVL) and to transport LCFAs as a fatty acid transporter. FATP2 is not only involved in the occurrence of nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM), but also plays an important role in lithogenic diet-induced cholelithiasis, the formation of cancer tumor immunity, the progression of chronic kidney disease (CKD), and the regulation of zoledronate-induced nephrotoxicity. Herein, we review the updated information on the role of FATP2 in related diseases. In particular, we discuss the new functions of FATP2 and propose that FATP2 is a potential clinical biomarker and therapeutic target. In conclusion, regulatory strategies for FATP2 may bring new treatment options for cancer and lipid metabolism-related disorders.
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11
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Cracking the code of sodium/calcium exchanger (NCX) gating: Old and new complexities surfacing from the deep web of secondary regulations. Cell Calcium 2020; 87:102169. [PMID: 32070925 DOI: 10.1016/j.ceca.2020.102169] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 01/29/2020] [Accepted: 01/29/2020] [Indexed: 12/14/2022]
Abstract
Cell membranes spatially define gradients that drive the complexity of biological signals. To guarantee movements and exchanges of solutes between compartments, membrane transporters negotiate the passages of ions and other important molecules through lipid bilayers. The Na+/Ca2+ exchangers (NCXs) in particular play central roles in balancing Na+ and Ca2+ fluxes across diverse proteolipid borders in all eukaryotic cells, influencing cellular functions and fate by multiple means. To prevent progression from balance to disease, redundant regulatory mechanisms cooperate at multiple levels (transcriptional, translational, and post-translational) and guarantee that the activities of NCXs are finely-tuned to cell homeostatic requirements. When this regulatory network is disturbed by pathological forces, cells may approach the end of life. In this review, we will discuss the main findings, controversies and open questions about regulatory mechanisms that control NCX functions in health and disease.
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12
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Gök C, Fuller W. Regulation of NCX1 by palmitoylation. Cell Calcium 2020; 86:102158. [PMID: 31935590 DOI: 10.1016/j.ceca.2019.102158] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 12/28/2019] [Accepted: 12/29/2019] [Indexed: 11/17/2022]
Abstract
Palmitoylation (S-acylation) is the reversible conjugation of a fatty acid (usually C16 palmitate) to intracellular cysteine residues of proteins via a thioester linkage. Palmitoylation anchors intracellular regions of proteins to membranes because the palmitoylated cysteine is recruited to the lipid bilayer. NCX1 is palmitoylated at a single cysteine in its large regulatory intracellular loop. The presence of an amphipathic α-helix immediately adjacent to the NCX1 palmitoylation site is required for NCX1 palmitoylation. The NCX1 palmitoylation site is conserved through most metazoan phlya. Although palmitoylation does not regulate the normal forward or reverse ion transport modes of NCX1, NCX1 palmitoylation is required for its inactivation: sodium-dependent inactivation and inactivation by PIP2 depletion are significantly impaired for unpalmitoylatable NCX1. Here we review the role of palmitoylation in regulating NCX1 activity, and highlight future questions that must be addressed to fully understand the importance of this regulatory mechanism for sodium and calcium transport in cardiac muscle.
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Affiliation(s)
- Caglar Gök
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, UK
| | - William Fuller
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, UK. https://twitter.com@FullerLabGlas
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13
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Al Kury LT. Calcium Homeostasis in Ventricular Myocytes of Diabetic Cardiomyopathy. J Diabetes Res 2020; 2020:1942086. [PMID: 33274235 PMCID: PMC7683117 DOI: 10.1155/2020/1942086] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 10/24/2020] [Accepted: 10/29/2020] [Indexed: 12/12/2022] Open
Abstract
Diabetes mellitus (DM) is a chronic metabolic disorder commonly characterized by high blood glucose levels, resulting from defects in insulin production or insulin resistance, or both. DM is a leading cause of mortality and morbidity worldwide, with diabetic cardiomyopathy as one of its main complications. It is well established that cardiovascular complications are common in both types of diabetes. Electrical and mechanical problems, resulting in cardiac contractile dysfunction, are considered as the major complications present in diabetic hearts. Inevitably, disturbances in the mechanism(s) of Ca2+ signaling in diabetes have implications for cardiac myocyte contraction. Over the last decade, significant progress has been made in outlining the mechanisms responsible for the diminished cardiac contractile function in diabetes using different animal models of type I diabetes mellitus (TIDM) and type II diabetes mellitus (TIIDM). The aim of this review is to evaluate our current understanding of the disturbances of Ca2+ transport and the role of main cardiac proteins involved in Ca2+ homeostasis in the diabetic rat ventricular cardiomyocytes. Exploring the molecular mechanism(s) of altered Ca2+ signaling in diabetes will provide an insight for the identification of novel therapeutic approaches to improve the heart function in diabetic patients.
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Affiliation(s)
- Lina T. Al Kury
- Department of Health Sciences, College of Natural and Health Sciences, Zayed University, Abu Dhabi 144534, UAE
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14
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Scranton K, John S, Escobar A, Goldhaber JI, Ottolia M. Modulation of the cardiac Na +-Ca 2+ exchanger by cytoplasmic protons: Molecular mechanisms and physiological implications. Cell Calcium 2019; 87:102140. [PMID: 32070924 DOI: 10.1016/j.ceca.2019.102140] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 12/06/2019] [Accepted: 12/07/2019] [Indexed: 01/31/2023]
Abstract
A precise temporal and spatial control of intracellular Ca2+ concentration is essential for a coordinated contraction of the heart. Following contraction, cardiac cells need to rapidly remove intracellular Ca2+ to allow for relaxation. This task is performed by two transporters: the plasma membrane Na+-Ca2+ exchanger (NCX) and the sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA). NCX extrudes Ca2+ from the cell, balancing the Ca2+entering the cytoplasm during systole through L-type Ca2+ channels. In parallel, following SR Ca2+ release, SERCA activity replenishes the SR, reuptaking Ca2+ from the cytoplasm. The activity of the mammalian exchanger is fine-tuned by numerous ionic allosteric regulatory mechanisms. Micromolar concentrations of cytoplasmic Ca2+ potentiate NCX activity, while an increase in intracellular Na+ levels inhibits NCX via a mechanism known as Na+-dependent inactivation. Protons are also powerful inhibitors of NCX activity. By regulating NCX activity, Ca2+, Na+ and H+ couple cell metabolism to Ca2+ homeostasis and therefore cardiac contractility. This review summarizes the recent progress towards the understanding of the molecular mechanisms underlying the ionic regulation of the cardiac NCX with special emphasis on pH modulation and its physiological impact on the heart.
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Affiliation(s)
- Kyle Scranton
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, UCLA, Los Angeles, CA 90095, USA
| | - Scott John
- Department of Medicine (Cardiology), UCLA, Los Angeles, CA 90095, USA; Cardiovascular Research Laboratory, UCLA, Los Angeles, CA 90095, USA
| | - Ariel Escobar
- Department of Bioengineering, School of Engineering, UC Merced, Merced, CA 95343, USA
| | - Joshua I Goldhaber
- Smidt Heart Institute, Cedars Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Michela Ottolia
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, UCLA, Los Angeles, CA 90095, USA; Cardiovascular Research Laboratory, UCLA, Los Angeles, CA 90095, USA.
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15
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Sakharkar MK, Kashmir Singh SK, Rajamanickam K, Mohamed Essa M, Yang J, Chidambaram SB. A systems biology approach towards the identification of candidate therapeutic genes and potential biomarkers for Parkinson's disease. PLoS One 2019; 14:e0220995. [PMID: 31487305 PMCID: PMC6728017 DOI: 10.1371/journal.pone.0220995] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 07/26/2019] [Indexed: 12/13/2022] Open
Abstract
Parkinson's disease (PD) is an irreversible and incurable multigenic neurodegenerative disorder. It involves progressive loss of mid brain dopaminergic neurons in the substantia nigra pars compacta (SN). We compared brain gene expression profiles with those from the peripheral blood cells of a separate sample of PD patients to identify disease-associated genes. Here, we demonstrate the use of gene expression profiling of brain and blood for detecting valid targets and identifying early PD biomarkers. Implementing this systematic approach, we discovered putative PD risk genes in brain, delineated biological processes and molecular functions that may be particularly disrupted in PD and also identified several putative PD biomarkers in blood. 20 of the differentially expressed genes in SN were also found to be differentially expressed in the blood. Further application of this methodology to other brain regions and neurological disorders should facilitate the discovery of highly reliable and reproducible candidate risk genes and biomarkers for PD. The identification of valid peripheral biomarkers for PD may ultimately facilitate early identification, intervention, and prevention efforts as well.
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Affiliation(s)
- Meena Kishore Sakharkar
- Drug Discovery and Development Research Group, College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Canada
- * E-mail: (MKS); (SBC)
| | | | - Karthic Rajamanickam
- Drug Discovery and Development Research Group, College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Canada
| | | | - Jian Yang
- Drug Discovery and Development Research Group, College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Canada
| | - Saravana Babu Chidambaram
- Department of Pharmacology, JSS College of Pharmacy, JSSAHER, Karnataka, India
- * E-mail: (MKS); (SBC)
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16
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Khan S, Cabral PD, Schilling WP, Schmidt ZW, Uddin AN, Gingras A, Madhavan SM, Garvin JL, Schelling JR. Kidney Proximal Tubule Lipoapoptosis Is Regulated by Fatty Acid Transporter-2 (FATP2). J Am Soc Nephrol 2017; 29:81-91. [PMID: 28993506 DOI: 10.1681/asn.2017030314] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 08/08/2017] [Indexed: 11/03/2022] Open
Abstract
Albuminuria and tubular atrophy are among the highest risks for CKD progression to ESRD. A parsimonious mechanism involves leakage of albumin-bound nonesterified fatty acids (NEFAs) across the damaged glomerular filtration barrier and subsequent reabsorption by the downstream proximal tubule, causing lipoapoptosis. We sought to identify the apical proximal tubule transporter that mediates NEFA uptake and cytotoxicity. We observed transporter-mediated uptake of fluorescently labeled NEFA in cultured proximal tubule cells and microperfused rat proximal tubules, with greater uptake from the apical surface than from the basolateral surface. Protein and mRNA expression analyses revealed that kidney proximal tubules express transmembrane fatty acid transporter-2 (FATP2), encoded by Slc27a2, but not the other candidate transporters CD36 and free fatty acid receptor 1. Kidney FATP2 localized exclusively to proximal tubule epithelial cells along the apical but not the basolateral membrane. Treatment of mice with lipidated albumin to induce proteinuria caused a decrease in the proportion of tubular epithelial cells and an increase in the proportion of interstitial space in kidneys from wild-type but not Slc27a2-/- mice. Ex vivo microperfusion and in vitro experiments with NEFA-bound albumin at concentrations that mimic apical proximal tubule exposure during glomerular injury revealed significantly reduced NEFA uptake and palmitate-induced apoptosis in microperfused Slc27a2-/- proximal tubules and Slc27a2-/- or FATP2 shRNA-treated proximal tubule cell lines compared with wild-type or scrambled oligonucleotide-treated cells, respectively. We conclude that FATP2 is a major apical proximal tubule NEFA transporter that regulates lipoapoptosis and may be an amenable target for the prevention of CKD progression.
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Affiliation(s)
- Shenaz Khan
- Department of Medicine, The MetroHealth System and
| | - Pablo D Cabral
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio
| | - William P Schilling
- Department of Medicine, The MetroHealth System and.,Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio
| | | | - Asif N Uddin
- Department of Medicine, The MetroHealth System and
| | | | | | - Jeffrey L Garvin
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio
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17
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Abstract
The longstanding focus in chronic kidney disease (CKD) research has been on the glomerulus, which is sensible because this is where glomerular filtration occurs, and a large proportion of progressive CKD is associated with significant glomerular pathology. However, it has been known for decades that tubular atrophy is also a hallmark of CKD and that it is superior to glomerular pathology as a predictor of glomerular filtration rate decline in CKD. Nevertheless, there are vastly fewer studies that investigate the causes of tubular atrophy, and fewer still that identify potential therapeutic targets. The purpose of this review is to discuss plausible mechanisms of tubular atrophy, including tubular epithelial cell apoptosis, cell senescence, peritubular capillary rarefaction and downstream tubule ischemia, oxidative stress, atubular glomeruli, epithelial-to-mesenchymal transition, interstitial inflammation, lipotoxicity and Na(+)/H(+) exchanger-1 inactivation. Once a a better understanding of tubular atrophy (and interstitial fibrosis) pathophysiology has been obtained, it might then be possible to consider tandem glomerular and tubular therapeutic strategies, in a manner similar to cancer chemotherapy regimens, which employ multiple drugs to simultaneously target different mechanistic pathways.
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18
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Neess D, Bek S, Engelsby H, Gallego SF, Færgeman NJ. Long-chain acyl-CoA esters in metabolism and signaling: Role of acyl-CoA binding proteins. Prog Lipid Res 2015; 59:1-25. [PMID: 25898985 DOI: 10.1016/j.plipres.2015.04.001] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 03/11/2015] [Accepted: 04/09/2015] [Indexed: 02/03/2023]
Abstract
Long-chain fatty acyl-CoA esters are key intermediates in numerous lipid metabolic pathways, and recognized as important cellular signaling molecules. The intracellular flux and regulatory properties of acyl-CoA esters have been proposed to be coordinated by acyl-CoA-binding domain containing proteins (ACBDs). The ACBDs, which comprise a highly conserved multigene family of intracellular lipid-binding proteins, are found in all eukaryotes and ubiquitously expressed in all metazoan tissues, with distinct expression patterns for individual ACBDs. The ACBDs are involved in numerous intracellular processes including fatty acid-, glycerolipid- and glycerophospholipid biosynthesis, β-oxidation, cellular differentiation and proliferation as well as in the regulation of numerous enzyme activities. Little is known about the specific roles of the ACBDs in the regulation of these processes, however, recent studies have gained further insights into their in vivo functions and provided further evidence for ACBD-specific functions in cellular signaling and lipid metabolic pathways. This review summarizes the structural and functional properties of the various ACBDs, with special emphasis on the function of ACBD1, commonly known as ACBP.
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Affiliation(s)
- Ditte Neess
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Signe Bek
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Hanne Engelsby
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Sandra F Gallego
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Nils J Færgeman
- Villum Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
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19
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Gray KL, Petersen KS, Clifton PM, Keogh JB. Attitudes and beliefs of health risks associated with sodium intake in diabetes. Appetite 2014; 83:97-103. [PMID: 25128832 DOI: 10.1016/j.appet.2014.08.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Revised: 07/31/2014] [Accepted: 08/04/2014] [Indexed: 11/30/2022]
Abstract
BACKGROUND Despite good evidence that reducing sodium intake can reduce blood pressure (BP), salt intake in people with type 1 diabetes (T1DM) or type 2 diabetes (T2DM) remains high. The purpose of this study was to describe the knowledge and beliefs of health risks associated with a high salt diet in adults with diabetes. METHODS Men and women with T1DM (n = 27; age 38 ± 16 years) or T2DM (n = 124; age 60 ± 11 years) were recruited. RESULTS Nine (6.0%) respondents knew the correct maximum daily recommended upper limit for salt intake. Thirty-six (23.9%) participants were not concerned with the amount of salt in their diet. Most participants knew that a diet high in salt was related to high BP (88.1%) and stroke (78.1%) and that foods such as pizza (80.8%) and bacon (84.8%) were high in salt. Fewer than 30% of people knew that foods such as white bread, cheese and breakfast cereals are high in salt (white bread 28.5%, cheese 29.1%, breakfast cereals 19.9%) and 51.0% correctly ranked three different nutrition information panels based on the sodium content. Label reading and purchase of low salt products was used by 60-80% of the group. Estimated average 24 hour urinary sodium excretion was 169 ± 32 mmol/24 h in men and 115 ± 27 mmol/24 h in women. CONCLUSION Label reading and purchase of low salt products was used by the majority of the group but their salt excretion was still high. Men who used label reading had a lower salt intake. Other strategies to promote a lower sodium intake such as reducing sodium in staple foods such as bread need investigation.
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Affiliation(s)
- Kristy L Gray
- School of Pharmacy and Medical Sciences, University of South Australia, Australia
| | - Kristina S Petersen
- School of Pharmacy and Medical Sciences, University of South Australia, Australia
| | - Peter M Clifton
- School of Pharmacy and Medical Sciences, University of South Australia, Australia
| | - Jennifer B Keogh
- School of Pharmacy and Medical Sciences, University of South Australia, Australia.
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20
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Yu Y, Carter CRJ, Youssef N, Dyck JRB, Light PE. Intracellular long-chain acyl CoAs activate TRPV1 channels. PLoS One 2014; 9:e96597. [PMID: 24798548 PMCID: PMC4010479 DOI: 10.1371/journal.pone.0096597] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 04/10/2014] [Indexed: 01/03/2023] Open
Abstract
TRPV1 channels are an important class of membrane proteins that play an integral role in the regulation of intracellular cations such as calcium in many different tissue types. The anionic phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2) is a known positive modulator of TRPV1 channels and the negatively charged phosphate groups interact with several basic amino acid residues in the proximal C-terminal TRP domain of the TRPV1 channel. We and other groups have shown that physiological sub-micromolar levels of long-chain acyl CoAs (LC-CoAs), another ubiquitous anionic lipid, can also act as positive modulators of ion channels and exchangers. Therefore, we investigated whether TRPV1 channel activity is similarly regulated by LC-CoAs. Our results show that LC-CoAs are potent activators of the TRPV1 channel and interact with the same PIP2-binding residues in TRPV1. In contrast to PIP2, LC-CoA modulation of TRPV1 is independent of Ca2+i, acting in an acyl side-chain saturation and chain-length dependent manner. Elevation of LC-CoAs in intact Jurkat T-cells leads to significant increases in agonist-induced Ca2+i levels. Our novel findings indicate that LC-CoAs represent a new fundamental mechanism for regulation of TRPV1 channel activity that may play a role in diverse cell types under physiological and pathophysiological conditions that alter fatty acid transport and metabolism such as obesity and diabetes.
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Affiliation(s)
- Yi Yu
- Department of Pharmacology, Alberta Diabetes Institute, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Chris R. J. Carter
- Department of Pharmacology, Alberta Diabetes Institute, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Nermeen Youssef
- Department of Pharmacology, Alberta Diabetes Institute, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Jason R. B. Dyck
- Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Peter E. Light
- Department of Pharmacology, Alberta Diabetes Institute, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- * E-mail:
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21
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Lipid metabolites and their differential pro-arrhythmic profiles: of importance in the development of a new anti-arrhythmic pharmacology. Mol Cell Biochem 2014; 393:191-7. [DOI: 10.1007/s11010-014-2060-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Accepted: 04/11/2014] [Indexed: 01/12/2023]
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22
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Khan S, Abu Jawdeh BG, Goel M, Schilling WP, Parker MD, Puchowicz MA, Yadav SP, Harris RC, El-Meanawy A, Hoshi M, Shinlapawittayatorn K, Deschênes I, Ficker E, Schelling JR. Lipotoxic disruption of NHE1 interaction with PI(4,5)P2 expedites proximal tubule apoptosis. J Clin Invest 2014; 124:1057-68. [PMID: 24531551 DOI: 10.1172/jci71863] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 12/11/2013] [Indexed: 12/12/2022] Open
Abstract
Chronic kidney disease progression can be predicted based on the degree of tubular atrophy, which is the result of proximal tubule apoptosis. The Na+/H+ exchanger NHE1 regulates proximal tubule cell survival through interaction with phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], but pathophysiologic triggers for NHE1 inactivation are unknown. Because glomerular injury permits proximal tubule luminal exposure and reabsorption of fatty acid/albumin complexes, we hypothesized that accumulation of amphipathic, long-chain acyl-CoA (LC-CoA) metabolites stimulates lipoapoptosis by competing with the structurally similar PI(4,5)P2 for NHE1 binding. Kidneys from mouse models of progressive, albuminuric kidney disease exhibited increased fatty acids, LC-CoAs, and caspase-2-dependent proximal tubule lipoapoptosis. LC-CoAs and the cytosolic domain of NHE1 directly interacted, with an affinity comparable to that of the PI(4,5)P2-NHE1 interaction, and competing LC-CoAs disrupted binding of the NHE1 cytosolic tail to PI(4,5)P2. Inhibition of LC-CoA catabolism reduced NHE1 activity and enhanced apoptosis, whereas inhibition of proximal tubule LC-CoA generation preserved NHE1 activity and protected against apoptosis. Our data indicate that albuminuria/lipiduria enhances lipotoxin delivery to the proximal tubule and accumulation of LC-CoAs contributes to tubular atrophy by severing the NHE1-PI(4,5)P2 interaction, thereby lowering the apoptotic threshold. Furthermore, these data suggest that NHE1 functions as a metabolic sensor for lipotoxicity.
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23
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Liu T, O'Rourke B. Regulation of the Na+/Ca2+ exchanger by pyridine nucleotide redox potential in ventricular myocytes. J Biol Chem 2013; 288:31984-92. [PMID: 24045952 DOI: 10.1074/jbc.m113.496588] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The cardiac Na(+)/Ca(2+) exchanger (NCX) is the major Ca(2+) efflux pathway on the sarcolemma, counterbalancing Ca(2+) influx via L-type Ca(2+) current during excitation-contraction coupling. Altered NCX activity modulates the sarcoplastic reticulum Ca(2+) load and can contribute to abnormal Ca(2+) handling and arrhythmias. NADH/NAD(+) is the main redox couple controlling mitochondrial energy production, glycolysis, and other redox reactions. Here, we tested whether cytosolic NADH/NAD(+) redox potential regulates NCX activity in adult cardiomyocytes. NCX current (INCX), measured with whole cell patch clamp, was inhibited in response to cytosolic NADH loaded directly via pipette or increased by extracellular lactate perfusion, whereas an increase of mitochondrial NADH had no effect. Reactive oxygen species (ROS) accumulation was enhanced by increasing cytosolic NADH, and NADH-induced INCX inhibition was abolished by the H2O2 scavenger catalase. NADH-induced ROS accumulation was independent of mitochondrial respiration (rotenone-insensitive) but was inhibited by the flavoenzyme blocker diphenylene iodonium. NADPH oxidase was ruled out as the effector because INCX was insensitive to cytosolic NADPH, and NADH-induced ROS and INCX inhibition were not abrogated by the specific NADPH oxidase inhibitor gp91ds-tat. This study reveals a novel mechanism of NCX regulation by cytosolic NADH/NAD(+) redox potential through a ROS-generating NADH-driven flavoprotein oxidase. The mechanism is likely to play a key role in Ca(2+) homeostasis and the response to alterations in the cytosolic pyridine nucleotide redox state during ischemia-reperfusion or other cardiovascular diseases.
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Affiliation(s)
- Ting Liu
- From the Division of Cardiology, Department of Medicine, The Johns Hopkins University, Baltimore, Maryland 21205
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24
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Acyl coenzyme A thioesterase 7 regulates neuronal fatty acid metabolism to prevent neurotoxicity. Mol Cell Biol 2013; 33:1869-82. [PMID: 23459938 DOI: 10.1128/mcb.01548-12] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Numerous neurological diseases are associated with dysregulated lipid metabolism; however, the basic metabolic control of fatty acid metabolism in neurons remains enigmatic. Here we have shown that neurons have abundant expression and activity of the long-chain cytoplasmic acyl coenzyme A (acyl-CoA) thioesterase 7 (ACOT7) to regulate lipid retention and metabolism. Unbiased and targeted metabolomic analysis of fasted mice with a conditional knockout of ACOT7 in the nervous system, Acot7(N-/-), revealed increased fatty acid flux into multiple long-chain acyl-CoA-dependent pathways. The alterations in brain fatty acid metabolism were concomitant with a loss of lean mass, hypermetabolism, hepatic steatosis, dyslipidemia, and behavioral hyperexcitability in Acot7(N-/-) mice. These failures in adaptive energy metabolism are common in neurodegenerative diseases. In agreement, Acot7(N-/-) mice exhibit neurological dysfunction and neurodegeneration. These data show that ACOT7 counterregulates fatty acid metabolism in neurons and protects against neurotoxicity.
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25
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Keung W, Ussher JR, Jaswal JS, Raubenheimer M, Lam VH, Wagg CS, Lopaschuk GD. Inhibition of carnitine palmitoyltransferase-1 activity alleviates insulin resistance in diet-induced obese mice. Diabetes 2013; 62:711-20. [PMID: 23139350 PMCID: PMC3581198 DOI: 10.2337/db12-0259] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Impaired skeletal muscle fatty acid oxidation has been suggested to contribute to insulin resistance and glucose intolerance. However, increasing muscle fatty acid oxidation may cause a reciprocal decrease in glucose oxidation, which might impair insulin sensitivity and glucose tolerance. We therefore investigated what effect inhibition of mitochondrial fatty acid uptake has on whole-body glucose tolerance and insulin sensitivity in obese insulin-resistant mice. C57BL/6 mice were fed a high-fat diet (60% calories from fat) for 12 weeks to develop insulin resistance. Subsequent treatment of mice for 4 weeks with the carnitine palmitoyltransferase-1 inhibitor, oxfenicine (150 mg/kg i.p. daily), resulted in improved whole-body glucose tolerance and insulin sensitivity. Exercise capacity was increased in oxfenicine-treated mice, which was accompanied by an increased respiratory exchange ratio. In the gastrocnemius muscle, oxfenicine increased pyruvate dehydrogenase activity, membrane GLUT4 content, and insulin-stimulated Akt phosphorylation. Intramyocellular levels of lipid intermediates, including ceramide, long-chain acyl CoA, and diacylglycerol, were also decreased. Our results demonstrate that inhibition of mitochondrial fatty acid uptake improves insulin sensitivity in diet-induced obese mice. This is associated with increased carbohydrate utilization and improved insulin signaling in the skeletal muscle, suggestive of an operating Randle Cycle in muscle.
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26
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Fantinelli JC, González Arbeláez LF, Pérez Núñez IA, Mosca SM. Protective effects of N-(2-mercaptopropionyl)-glycine against ischemia-reperfusion injury in hypertrophied hearts. Exp Mol Pathol 2012; 94:277-84. [PMID: 22850634 DOI: 10.1016/j.yexmp.2012.07.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 07/20/2012] [Indexed: 01/03/2023]
Abstract
The beneficial effects of N-(2-mercaptopropionyl)-glycine (MPG) against ischemia-reperfusion injury in normotensive animals have been previously studied. Our objective was to test the action of MPG during ischemia and reperfusion in hearts from spontaneously hypertensive rats (SHR). Isolated hearts from SHR and age-matched normotensive rats Wistar Kyoto (WKY) were subjected to 50-min global ischemia (GI) and 2-hour reperfusion (R). In other hearts MPG 2mM was administered during 10 min before GI and the first 10 min of R. Infarct size (IS) was assessed by TTC staining technique and expressed as percentage of risk area. Postischemic recovery of myocardial function was assessed. Reduced glutathione (GSH), thiobarbituric acid reactive substances (TBARS) and SOD cytosolic activity - as estimators of oxidative stress and MnSOD cytosolic activity - as an index of (mPTP) opening were determined. In isolated mitochondria H(2)O(2)-induced mPTP opening was also measured. The treatment with MPG decreased infarct size, preserved GSH levels and decreased SOD and MnSOD cytosolic activities, TBARS concentration, and H(2)O(2) induced-mPTP opening in both rat strains. Our results show that in both hypertrophied and normal hearts an attenuation of mPTP opening via reduction of oxidative stress appears to be the predominant mechanism involved in the cardioprotection against reperfusion injury MPG-mediated.
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Affiliation(s)
- Juliana C Fantinelli
- Established Investigator of CONICET, Centro de Investigaciones Cardiovasculares, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina
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27
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Berberián G, Podjarny A, DiPolo R, Beaugé L. Metabolic regulation of the squid nerve Na⁺/Ca²⁺ exchanger: recent kinetic, biochemical and structural developments. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 108:47-63. [PMID: 21964458 DOI: 10.1016/j.pbiomolbio.2011.09.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 08/30/2011] [Accepted: 09/13/2011] [Indexed: 11/25/2022]
Abstract
The Na⁺/Ca²⁺ exchangers are structural membrane proteins, essential for the extrusion of Ca²⁺ from most animal cells. Apart from the transport sites, they have several interacting ionic and metabolic sites located at the intracellular loop of the exchanger protein. One of these, the intracellular Ca²⁺ regulatory sites, are essential and must be occupied by Ca²⁺ to allow any type of ion (Na⁺ or Ca²⁺) translocation. Intracellular protons and Na⁺ are inhibitory by reducing the affinity of the regulatory sites for Ca²⁺; MgATP stimulates by antagonizing H⁺ and Na⁺. We have proposed a kinetic scheme to explain all ionic and metabolic regulation of the squid nerve Na⁺/Ca²⁺ exchanger. This model uniquely accounts for most of the new kinetic data provided here; however, none of the existing models can explain the trans effects of the Ca(i)²⁺-regulatory sites on external cation transport sites; i.e. all models are incomplete. MgATP up-regulation of the squid Na⁺/Ca²⁺ exchanger requires a cytosolic protein, which has been recently identified as a member of the lipocalin super family of Lipid Binding Proteins (LBP or FABP) of 132 amino acids (ReP1-NCXSQ, access to GenBank EU981897). This protein was cloned, expressed and purified. To be active, ReP1-NCXSQ must be phosphorylated from MgATP by a kinase present in the plasma membrane. Phosphorylated ReP1-NCXSQ can stimulate the exchanger in the absence of ATP. Experiments with proteoliposomes proved that this up-regulation can take place just with the lipid membrane and the exchanger protein. The structure of ReP1-NCXSQ predicted from the amino acid sequence has been confirmed by X-ray crystal analysis; it has a "barrel" formed by ten beta sheets and two alpha helices, with a lipid coordinated by hydrogen bonds with Arg 126 and Tyr 128.
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Affiliation(s)
- Graciela Berberián
- Laboratorio de Biofísica, Instituto de Investigación Médica "Mercedes y Martín Ferreyra" (INIMEC-CONICET), Casilla de Correo 389, 5000 Córdoba, Argentina
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Intracerebroventricular leptin administration differentially alters cardiac energy metabolism in mice fed a low-fat and high-fat diet. J Cardiovasc Pharmacol 2011; 57:103-13. [PMID: 20980918 DOI: 10.1097/fjc.0b013e31820014f9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Leptin directly acts on peripheral tissues and alters energy metabolism in obese mice. It also has acute beneficial effects on these tissues via its hypothalamic action. However, it is not clear what effect chronic intracerebroventrical (ICV) leptin administration has on cardiac energy metabolism. We examined the effects of chronic ICV leptin on glucose and fatty acid metabolism in isolated working hearts from high-fat-fed and low-fat-fed mice. Mice were fed a high-fat (60% calories from fat) or low-fat (10% calories from fat) diet for 8 weeks before ICV leptin (5 [mu]g/d) for 7 days. In low-fat-fed mice, leptin increased glucose oxidation rates in isolated working hearts when compared with control [203 +/- 21 vs. 793 +/- 93 nmol[middle dot](g dry weight)-1[middle dot]min-1]. In high-fat-fed mice leptin inhibited fatty acid oxidation [476 +/- 73 vs. 251 +/- 38 nmol[middle dot](g[middle dot]dry[middle dot]wt)-1[middle dot]min-1]. The increase in glucose oxidation in low-fat-fed mice was accompanied by increased pyruvate dehydrogenase activity. In high-fat-fed mice, leptin increased cardiac malonyl coenzyme A levels, secondary to a decrease in malonyl coenzyme A decarboxylase expression. These results suggest that ICV leptin alters cardiac energy metabolism opposite to its peripheral effects and that these effects differ depending on energy substrate supply to the mice.
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29
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Increased CD36 expression in middle-aged mice contributes to obesity-related cardiac hypertrophy in the absence of cardiac dysfunction. J Mol Med (Berl) 2011; 89:459-69. [DOI: 10.1007/s00109-010-0720-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Revised: 11/20/2010] [Accepted: 12/14/2010] [Indexed: 01/18/2023]
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Hamming KS, Soliman D, Webster NJ, Searle GJ, Matemisz LC, Liknes DA, Dai XQ, Pulinilkunnil T, Riedel MJ, Dyck JR, MacDonald PE, Light PE. Inhibition of beta-cell sodium-calcium exchange enhances glucose-dependent elevations in cytoplasmic calcium and insulin secretion. Diabetes 2010; 59:1686-93. [PMID: 20413506 PMCID: PMC2889768 DOI: 10.2337/db09-0630] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
OBJECTIVE The sodium-calcium exchanger isoform 1 (NCX1) regulates cytoplasmic calcium (Ca(2+)(c)) required for insulin secretion in beta-cells. NCX1 is alternatively spliced, resulting in the expression of splice variants in different tissues such as NCX1.3 and -1.7 in beta-cells. As pharmacological inhibitors of NCX1 splice variants are in development, the pharmacological profile of beta-cell NCX1.3 and -1.7 and the cellular effects of NCX1 inhibition were investigated. RESEARCH DESIGN AND METHODS The patch-clamp technique was used to examine the pharmacological profile of the NCX1 inhibitor KB-R7943 on recombinant NCX1.3 and -1.7 activity. Ca(2+) imaging and membrane capacitance were used to assess the effects of KB-R7943 on Ca(2+)(c) and insulin secretion in mouse and human beta-cells and islets. RESULTS NCX1.3 and -1.7 calcium extrusion (forward-mode) activity was approximately 16-fold more sensitive to KB-R7943 inhibition compared with cardiac NCX1.1 (IC(50s) = 2.9 and 2.4 vs. 43.0 micromol/l, respectively). In single mouse/human beta-cells, 1 micromol/l KB-R7943 increased insulin granule exocytosis but was without effect on alpha-cell glucagon granule exocytosis. KB-R7943 also augmented sulfonylurea and glucose-stimulated Ca(2+)(c) levels and insulin secretion in mouse and human islets, although KB-R7943 was without effect under nonstimulated conditions. CONCLUSIONS Islet NCX1 splice variants display a markedly greater sensitivity to pharmacological inhibition than the cardiac NCX1.1 splice variant. NCX1 inhibition resulted in glucose-dependent increases in Ca(2+)(c) and insulin secretion in mouse and human islets. Thus, we identify beta-cell NCX1 splice variants as targets for the development of novel glucose-sensitive insulinotropic drugs for type 2 diabetes.
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Affiliation(s)
- Kevin S.C. Hamming
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Daniel Soliman
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Nicola J. Webster
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Gavin J. Searle
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Laura C. Matemisz
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - David A. Liknes
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Xiao-Qing Dai
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Thomas Pulinilkunnil
- Department of Pediatrics, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Michael J. Riedel
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Jason R.B. Dyck
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- Department of Pediatrics, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Patrick E. MacDonald
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Peter E. Light
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- Corresponding author: Peter E. Light,
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31
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Koonen DP, Sung MM, Kao CK, Dolinsky VW, Koves TR, Ilkayeva O, Jacobs RL, Vance DE, Light PE, Muoio DM, Febbraio M, Dyck JR. Alterations in skeletal muscle fatty acid handling predisposes middle-aged mice to diet-induced insulin resistance. Diabetes 2010; 59:1366-75. [PMID: 20299464 PMCID: PMC2874697 DOI: 10.2337/db09-1142] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
OBJECTIVE Although advanced age is a risk factor for type 2 diabetes, a clear understanding of the changes that occur during middle age that contribute to the development of skeletal muscle insulin resistance is currently lacking. Therefore, we sought to investigate how middle age impacts skeletal muscle fatty acid handling and to determine how this contributes to the development of diet-induced insulin resistance. RESEARCH DESIGN AND METHODS Whole-body and skeletal muscle insulin resistance were studied in young and middle-aged wild-type and CD36 knockout (KO) mice fed either a standard or a high-fat diet for 12 weeks. Molecular signaling pathways, intramuscular triglycerides accumulation, and targeted metabolomics of in vivo mitochondrial substrate flux were also analyzed in the skeletal muscle of mice of all ages. RESULTS Middle-aged mice fed a standard diet demonstrated an increase in intramuscular triglycerides without a concomitant increase in insulin resistance. However, middle-aged mice fed a high-fat diet were more susceptible to the development of insulin resistance-a condition that could be prevented by limiting skeletal muscle fatty acid transport and excessive lipid accumulation in middle-aged CD36 KO mice. CONCLUSION Our data provide insight into the mechanisms by which aging becomes a risk factor for the development of insulin resistance. Our data also demonstrate that limiting skeletal muscle fatty acid transport is an effective approach for delaying the development of age-associated insulin resistance and metabolic disease during exposure to a high-fat diet.
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Affiliation(s)
- Debby P.Y. Koonen
- Department of Pediatrics, Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada
- Department of Pathology and Medical Biology, Medical Biology Section, Division Molecular Genetics, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Miranda M.Y. Sung
- Department of Pediatrics, Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada
| | - Cindy K.C. Kao
- Department of Pediatrics, Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada
| | - Vernon W. Dolinsky
- Department of Pediatrics, Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada
| | - Timothy R. Koves
- Sarah W. Stedman Nutrition and Metabolism Center, Departments of Medicine, Pharmacology, and Cancer Biology, Duke University, Durham, North Carolina
| | - Olga Ilkayeva
- Sarah W. Stedman Nutrition and Metabolism Center, Departments of Medicine, Pharmacology, and Cancer Biology, Duke University, Durham, North Carolina
| | - René L. Jacobs
- Group on the Molecular and Cell Biology of Lipids, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Dennis E. Vance
- Group on the Molecular and Cell Biology of Lipids, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Peter E. Light
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Deborah M. Muoio
- Sarah W. Stedman Nutrition and Metabolism Center, Departments of Medicine, Pharmacology, and Cancer Biology, Duke University, Durham, North Carolina
| | - Maria Febbraio
- Department of Cell Biology, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio; and
| | - Jason R.B. Dyck
- Department of Pediatrics, Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta, Canada
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
- Corresponding author: Jason R.B. Dyck,
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32
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Condrescu M, Reeves JP. Inhibition of sodium–calcium exchange by KB-R7943: Dodecylamine and sphingosine in transfected Chinese hamster ovary cells. Cell Calcium 2010; 47:404-11. [DOI: 10.1016/j.ceca.2010.02.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Revised: 02/05/2010] [Accepted: 02/08/2010] [Indexed: 12/13/2022]
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Soliman D, Hamming KS, Matemisz LC, Light PE. Reactive oxygen species directly modify sodium–calcium exchanger activity in a splice variant-dependent manner. J Mol Cell Cardiol 2009; 47:595-602. [DOI: 10.1016/j.yjmcc.2009.05.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2009] [Revised: 05/15/2009] [Accepted: 05/16/2009] [Indexed: 11/15/2022]
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34
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Raimunda D, Bollo M, Beaugé L, Berberián G. Squid nerve Na+/Ca2+ exchanger expressed in Saccharomyces cerevisiae: Up-regulation by a phosphorylated cytosolic protein (ReP1–NCXSQ) is identical to that of native exchanger in situ. Cell Calcium 2009; 45:499-508. [DOI: 10.1016/j.ceca.2009.03.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 03/12/2009] [Accepted: 03/17/2009] [Indexed: 01/11/2023]
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35
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Abstract
Arrhythmias arise from a complex interaction between structural changes in the myocardium and changes in cellular electrophysiology. Electrophysiological balance requires precise control of sarcolemmal ion channels and exchangers, many of which are regulated by phospholipid, phosphatidylinositol(4,5)bisphosphate. Phosphatidylinositol(4,5)bisphosphate is the immediate precursor of inositol(1,4,5)trisphosphate, a regulator of intracellular Ca2+ signalling and, therefore, a potential contributor to arrhythmogenesis by altering Ca2+ homeostasis. The aim of the present review is to outline current evidence that this signalling pathway can be a player in the initiation or maintenance of arrhythmias.
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Affiliation(s)
- Elizabeth A Woodcock
- Molecular Cardiology Laboratory, Baker IDI Heart and Diabetes Institute, PO Box 6492, St Kilda Road Central, Melbourne, 8008 Victoria, Australia.
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36
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Hamming KSC, Riedel MJ, Soliman D, Matemisz LC, Webster NJ, Searle GJ, MacDonald PE, Light PE. Splice variant-dependent regulation of beta-cell sodium-calcium exchange by acyl-coenzyme As. Mol Endocrinol 2008; 22:2293-306. [PMID: 18635667 DOI: 10.1210/me.2008-0053] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The sodium-calcium exchanger isoform 1 (NCX1) is intimately involved in the regulation of calcium (Ca(2+)) homeostasis in many tissues including excitation-secretion coupling in pancreatic beta-cells. Our group has previously found that intracellular long-chain acyl-coenzyme As (acyl CoAs) are potent regulators of the cardiac NCX1.1 splice variant. Despite this, little is known about the biophysical properties of beta-cell NCX1 splice variants and the effects of intracellular modulators on their important physiological function in health and disease. Here, we show that the forward-mode activity of beta-cell NCX1 splice variants is differentially modulated by acyl-CoAs and is dependent both upon the intrinsic biophysical properties of the particular NCX1 splice variant as well as the side chain length and degree of saturation of the acyl-CoA moiety. Notably, saturated long-chain acyl-CoAs increased both peak and total NCX1 activity, whereas polyunsaturated long-chain acyl-CoAs did not show this effect. Furthermore, we have identified the exon within the alternative splicing region that bestows sensitivity to acyl-CoAs. We conclude that the physiologically relevant forward-mode activity of NCX1 splice variants expressed in the pancreatic beta-cell are sensitive to acyl-CoAs of different saturation and alterations in intracellular acyl-CoA levels may ultimately lead to defects in Ca(2+)-mediated exocytosis and insulin secretion.
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Affiliation(s)
- Kevin S C Hamming
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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37
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Webster NJ, Searle GJ, Lam PPL, Huang YC, Riedel MJ, Harb G, Gaisano HY, Holt A, Light PE. Elevation in intracellular long-chain acyl-coenzyme A esters lead to reduced beta-cell excitability via activation of adenosine 5'-triphosphate-sensitive potassium channels. Endocrinology 2008; 149:3679-87. [PMID: 18372336 DOI: 10.1210/en.2007-1138] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Closure of pancreatic beta-cell ATP-sensitive potassium (K(ATP)) channels links glucose metabolism to electrical activity and insulin secretion. It is now known that saturated, but not polyunsaturated, long-chain acyl-coenyzme A esters (acyl-CoAs) can potently activate K(ATP) channels when superfused directly across excised membrane patches, suggesting a plausible mechanism to account for reduced beta-cell excitability and insulin secretion observed in obesity and type 2 diabetes. However, reduced beta-cell excitability due to elevation of endogenous saturated acyl-CoAs has not been confirmed in intact pancreatic beta-cells. To test this notion directly, endogenous acyl-CoA levels were elevated within primary mouse beta-cells using virally delivered overexpression of long-chain acyl-CoA synthetase-1 (AdACSL-1), and the effects on beta-cell K(ATP) channel activity and cell excitability was assessed using the perforated whole-cell and cell-attached patch-clamp technique. Data indicated a significant increase in K(ATP) channel activity in AdACSL-1-infected beta-cells cultured in medium supplemented with palmitate/oleate but not with the polyunsaturated fat linoleate. No changes in the ATP/ADP ratio were observed in any of the groups. Furthermore, AdACSL-1-infected beta-cells (with palmitate/oleate) showed a significant decrease in electrical responsiveness to glucose and tolbutamide and a hyperpolarized resting membrane potential at 5 mm glucose. These results suggest a direct link between intracellular fatty ester accumulation and K(ATP) channel activation, which may contribute to beta-cell dysfunction in type 2 diabetes.
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Affiliation(s)
- Nicola J Webster
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
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Tucker SJ, Baukrowitz T. How highly charged anionic lipids bind and regulate ion channels. ACTA ACUST UNITED AC 2008; 131:431-8. [PMID: 18411329 PMCID: PMC2346576 DOI: 10.1085/jgp.200709936] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Stephen J Tucker
- Oxford Centre for Gene Function, Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, UK
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Koonen DPY, Febbraio M, Bonnet S, Nagendran J, Young ME, Michelakis ED, Dyck JRB. CD36 expression contributes to age-induced cardiomyopathy in mice. Circulation 2007; 116:2139-47. [PMID: 17967771 DOI: 10.1161/circulationaha.107.712901] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BACKGROUND Cardiac remodeling and impaired cardiac performance in the elderly significantly increase the risk of developing heart disease. Although vascular abnormalities associated with aging contribute to the age-related decline in cardiac function, myocardium-specific events may also be involved. METHODS AND RESULTS We show that intramyocardial lipid accumulation, as well as a reduction in both fatty acid and glucose oxidation and a subsequent deterioration in cardiac ATP supply, also occurs in aged mice. Consistent with an energetically compromised heart, hearts from aged mice display depressed myocardial performance and cardiac hypertrophy. Associated with this is a dramatic increase in the fatty acid transport protein CD36 in aged hearts compared with young hearts, which suggests that CD36 is a mediator of these multiple metabolic, functional, and structural alterations in the aged heart. In accordance with this, hearts from aged CD36-deficient mice have lower levels of intramyocardial lipids, demonstrate improved mitochondria-derived ATP production, have significantly enhanced function compared with aged wild-type mice, and have a blunted hypertrophic response. CONCLUSIONS These findings provide evidence that CD36 mediates an age-induced cardiomyopathy in mice and suggest that inhibition of CD36 may be an approach for the treatment of the detrimental age-related effects on cardiac performance.
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Affiliation(s)
- Debby P Y Koonen
- Cardiovascular Research Group, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2S2
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40
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Abstract
Mammalian Na+/Ca2+ exchangers are members of three branches of a much larger family of transport proteins [the CaCA (Ca2+/cation antiporter) superfamily] whose main role is to provide control of Ca2+ flux across the plasma membranes or intracellular compartments. Since cytosolic levels of Ca2+ are much lower than those found extracellularly or in sequestered stores, the major function of Na+/Ca2+ exchangers is to extrude Ca2+ from the cytoplasm. The exchangers are, however, fully reversible and thus, under special conditions of subcellular localization and compartmentalized ion gradients, Na+/Ca2+ exchangers may allow Ca2+ entry and may play more specialized roles in Ca2+ movement between compartments. The NCX (Na+/Ca2+ exchanger) [SLC (solute carrier) 8] branch of Na+/Ca2+ exchangers comprises three members: NCX1 has been most extensively studied, and is broadly expressed with particular abundance in heart, brain and kidney, NCX2 is expressed in brain, and NCX3 is expressed in brain and skeletal muscle. The NCX proteins subserve a variety of roles, depending upon the site of expression. These include cardiac excitation-contraction coupling, neuronal signalling and Ca2+ reabsorption in the kidney. The NCKX (Na2+/Ca2+-K+ exchanger) (SLC24) branch of Na+/Ca2+ exchangers transport K+ and Ca2+ in exchange for Na+, and comprises five members: NCKX1 is expressed in retinal rod photoreceptors, NCKX2 is expressed in cone photoreceptors and in neurons throughout the brain, NCKX3 and NCKX4 are abundant in brain, but have a broader tissue distribution, and NCKX5 is expressed in skin, retinal epithelium and brain. The NCKX proteins probably play a particularly prominent role in regulating Ca2+ flux in environments which experience wide and frequent fluctuations in Na+ concentration. Until recently, the range of functions that NCKX proteins play was generally underappreciated. This situation is now changing rapidly as evidence emerges for roles including photoreceptor adaptation, synaptic plasticity and skin pigmentation. The CCX (Ca2+/cation exchanger) branch has only one mammalian member, NCKX6 or NCLX (Na+/Ca2+-Li+ exchanger), whose physiological function remains unclear, despite a broad pattern of expression.
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Affiliation(s)
- Jonathan Lytton
- Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute of Alberta, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
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41
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Iwata Y, Katanosaka Y, Hisamitsu T, Wakabayashi S. Enhanced Na+/H+ exchange activity contributes to the pathogenesis of muscular dystrophy via involvement of P2 receptors. THE AMERICAN JOURNAL OF PATHOLOGY 2007; 171:1576-87. [PMID: 17823278 PMCID: PMC2043518 DOI: 10.2353/ajpath.2007.070452] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A subset of muscular dystrophy is caused by genetic defects in dystrophin-associated glycoprotein complex. Using two animal models (BIO14.6 hamsters and mdx mice), we found that Na(+)/H(+) exchanger (NHE) inhibitors prevented muscle degeneration. NHE activity was constitutively enhanced in BIO myotubes, as evidenced by the elevated intracellular pH and enhanced (22)Na(+) influx, with activation of putative upstream kinases ERK42/44. NHE inhibitor significantly reduced the increases in baseline intracellular Ca(2+) as well as Na(+) concentration and stretch-induced damage, suggesting that Na(+)(i)-dependent Ca(2+)overload via the Na(+)/Ca(2+) exchanger may cause muscle damage. Furthermore, ATP was found to be released continuously from BIO myotubes in a manner further stimulated by stretching and that the P2 receptor antagonists reduce the enhanced NHE activity and dystrophic muscle damage. These observations suggest that autocrine ATP release may be primarily involved in genesis of abnormal ionic homeostasis in dystrophic muscles and that Na(+)-dependent ion exchangers play a critical pathological role in muscular dystrophy.
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Affiliation(s)
- Yuko Iwata
- Department of Molecular Physiology, National Cardiovascular Center Research Institute, Suita, Osaka, Japan.
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42
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Yaradanakul A, Feng S, Shen C, Lariccia V, Lin MJ, Yang J, Dong P, Yin HL, Albanesi JP, Hilgemann DW. Dual control of cardiac Na+ Ca2+ exchange by PIP(2): electrophysiological analysis of direct and indirect mechanisms. J Physiol 2007; 582:991-1010. [PMID: 17540705 PMCID: PMC2075271 DOI: 10.1113/jphysiol.2007.132712] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Cardiac Na(+)-Ca(2+) exchange (NCX1) inactivates in excised membrane patches when cytoplasmic Ca(2+) is removed or cytoplasmic Na(+) is increased. Exogenous phosphatidylinositol-4,5-bis-phosphate (PIP(2)) can ablate both inactivation mechanisms, while it has no effect on inward exchange current in the absence of cytoplasmic Na(+). To probe PIP(2) effects in intact cells, we manipulated PIP(2) metabolism by several means. First, we used cell lines with M1 (muscarinic) receptors that couple to phospholipase C's (PLCs). As expected, outward NCX1 current (i.e. Ca(2+) influx) can be strongly inhibited when M1 agonists induce PIP(2) depletion. However, inward currents (i.e. Ca(2+) extrusion) without cytoplasmic Na(+) can be increased markedly in parallel with an increase of cell capacitance (i.e. membrane area). Similar effects are incurred by cytoplasmic perfusion of GTPgammaS or the actin cytoskeleton disruptor latrunculin, even in the presence of non-hydrolysable ATP (AMP-PNP). Thus, G-protein signalling may increase NCX1 currents by destabilizing membrane cytoskeleton-PIP(2) interactions. Second, to increase PIP(2) we directly perfused PIP(2) into cells. Outward NCX1 currents increase as expected. But over minutes currents decline substantially, and cell capacitance usually decreases in parallel. Third, using BHK cells with stable NCX1 expression, we increased PIP(2) by transient expression of a phosphatidylinositol-4-phosphate-5-kinase (hPIP5KIbeta) and a PI4-kinase (PI4KIIalpha). NCX1 current densities were decreased by > 80 and 40%, respectively. Fourth, we generated transgenic mice with 10-fold cardiac-specific overexpression of PI4KIIalpha. This wortmannin-insensitive PI4KIIalpha was chosen because basal cardiac phosphoinositides are nearly insensitive to wortmannin, and surface membrane PI4-kinase activity, defined functionally in excised patches, is not blocked by wortmannin. Both phosphatidylinositol-4-phosphate (PIP) and PIP(2) were increased significantly, while NCX1 current densities were decreased by 78% with no loss of NCX1 expression. Most mice developed cardiac hypertrophy, and immunohistochemical analysis suggests that NCX1 is redistributed away from the outer sarcolemma. Cholera toxin uptake was increased 3-fold, suggesting that clathrin-independent endocytosis is enhanced. We conclude that direct effects of PIP(2) to activate NCX1 can be strongly modulated by opposing mechanisms in intact cells that probably involve membrane cytoskeleton remodelling and membrane trafficking.
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Affiliation(s)
- Alp Yaradanakul
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9040, USA
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43
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Hilgemann DW. On the physiological roles of PIP(2) at cardiac Na+ Ca2+ exchangers and K(ATP) channels: a long journey from membrane biophysics into cell biology. J Physiol 2007; 582:903-9. [PMID: 17463041 PMCID: PMC2075268 DOI: 10.1113/jphysiol.2007.132746] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Over the last 10 years we have tried to understand the roles of PIP(2) in regulating cardiac Na(+)-Ca(2+) exchangers and K(ATP) K(+) channels, both of which are directly activated by PIP(2). Up to now, the idea that hormones might physiologically regulate these mechanisms by causing changes of PIP(2) concentrations in the cardiac sarcolemma, either locally or globally, is not well supported. In intact myocardium, but not excised patches, phosphatidylinositol 4-phosphate 5-kinase (PIP5K) activity appears to be Ca(2+) activated and dependent on cardiac activity. Potentially therefore the primary second messenger of the heart, cytoplasmic Ca(2+), may regulate PIP(2) and therewith numerous cardiac membrane processes. In general, however, PIP(2) may simply serve to strongly activate various cardiac channels and transporters when they are inserted in the sarcolemma, while a lack of PIP(2) on internal membranes maintains transporters and channels inactive during trafficking and processing. As in most, if not all, strong regulatory systems of cells, the activating effects of PIP(2) can apparently be countered by strong inactivation mechanisms. In this context, our recent work suggests that internalization of cardiac Na(+)-Ca(2+) exchangers is promoted by increased PIP(2) synthesis, especially in combination with other cell signals. Assuming that multiple adapter-PIP(2) interactions are necessary to initiate the budding of individual membrane vesicles, the dependence of endocytosis on PIP(2) in the surface membrane can potentially be a very steep function. Thus, a better understanding of the regulation of cardiac lipid kinases may be key to understanding when and how cardiac ion transporters and channels are internalized.
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Affiliation(s)
- Donald W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9040, USA.
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