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Claeyssen C, Bulangalire N, Bastide B, Agbulut O, Cieniewski-Bernard C. Desmin and its molecular chaperone, the αB-crystallin: How post-translational modifications modulate their functions in heart and skeletal muscles? Biochimie 2024; 216:137-159. [PMID: 37827485 DOI: 10.1016/j.biochi.2023.10.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 08/04/2023] [Accepted: 10/02/2023] [Indexed: 10/14/2023]
Abstract
Maintenance of the highly organized striated muscle tissue requires a cell-wide dynamic network through protein-protein interactions providing an effective mechanochemical integrator of morphology and function. Through a continuous and complex trans-cytoplasmic network, desmin intermediate filaments ensure this essential role in heart and in skeletal muscle. Besides their role in the maintenance of cell shape and architecture (permitting contractile activity efficiency and conferring resistance towards mechanical stress), desmin intermediate filaments are also key actors of cell and tissue homeostasis. Desmin participates to several cellular processes such as differentiation, apoptosis, intracellular signalisation, mechanotransduction, vesicle trafficking, organelle biogenesis and/or positioning, calcium homeostasis, protein homeostasis, cell adhesion, metabolism and gene expression. Desmin intermediate filaments assembly requires αB-crystallin, a small heat shock protein. Over its chaperone activity, αB-crystallin is involved in several cellular functions such as cell integrity, cytoskeleton stabilization, apoptosis, autophagy, differentiation, mitochondria function or aggresome formation. Importantly, both proteins are known to be strongly associated to the aetiology of several cardiac and skeletal muscles pathologies related to desmin filaments disorganization and a strong disturbance of desmin interactome. Note that these key proteins of cytoskeleton architecture are extensively modified by post-translational modifications that could affect their functional properties. Therefore, we reviewed in the herein paper the impact of post-translational modifications on the modulation of cellular functions of desmin and its molecular chaperone, the αB-crystallin.
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Affiliation(s)
- Charlotte Claeyssen
- University of Lille, University of Artois, University of Littoral Côte d'Opale, ULR 7369 - URePSSS - Unité de Recherche Pluridisciplinaire Sport Santé Société, F-59000 Lille, France
| | - Nathan Bulangalire
- University of Lille, University of Artois, University of Littoral Côte d'Opale, ULR 7369 - URePSSS - Unité de Recherche Pluridisciplinaire Sport Santé Société, F-59000 Lille, France; Université de Lille, CHU Lille, F-59000 Lille, France
| | - Bruno Bastide
- University of Lille, University of Artois, University of Littoral Côte d'Opale, ULR 7369 - URePSSS - Unité de Recherche Pluridisciplinaire Sport Santé Société, F-59000 Lille, France
| | - Onnik Agbulut
- Sorbonne Université, Institut de Biologie Paris-Seine (IBPS), CNRS UMR 8256, Inserm ERL U1164, Biological Adaptation and Ageing, 75005, Paris, France
| | - Caroline Cieniewski-Bernard
- University of Lille, University of Artois, University of Littoral Côte d'Opale, ULR 7369 - URePSSS - Unité de Recherche Pluridisciplinaire Sport Santé Société, F-59000 Lille, France.
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Jung E, Capel R, Jiang C, Venturi E, Neagu G, Pearcey S, Zhou Y, Zhang Y, Lei M. Cardiac deficiency of P21-activated kinase 1 promotes atrial arrhythmogenesis in mice following adrenergic challenge. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220168. [PMID: 37122217 PMCID: PMC10150202 DOI: 10.1098/rstb.2022.0168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 11/24/2022] [Indexed: 05/02/2023] Open
Abstract
P21-activated kinase 1 (Pak1) signalling plays a vital and overall protective role in the heart. However, the phenotypes of Pak1 deficiency in the cardiac atria have not been well explored. In this study, Pak1 cardiac-conditional knock-out (cKO) mice were studied under baseline and adrenergic challenge conditions. Pak1 cKO mice show atrial arrhythmias including atrial fibrillation (AF) in vivo, detected during anaesthetized electrocardiography without evidence of interstitial fibrosis upon Masson's trichrome staining. Optical mapping of left atrial preparations from Pak1 cKO mice revealed a higher incidence of Ca2+ and action potential alternans under isoprenaline challenge and differences in baseline action potential and calcium transient characteristics. Type-2 ryanodine receptor (RyR2) channels from Pak1 cKO hearts had a higher open probability than those from wild-type. Reverse transcription-quantitative polymerase chain reaction and Western blotting indicated that pCamkIIδ and RyR2 are highly phosphorylated at baseline in the atria of Pak1 cKO mice, while the expression of Slc8a2 and Slc8a3 as a Na+-Ca2+ exchanger, controlling the influx of Ca2+ from outside of the cell and efflux of Na+ from the cytoplasm, are augmented. Chromatin immunoprecipitation study showed that pCreb1 interacts with Slc8a2 and Slc8a3. Our study thus demonstrates that deficiency of Pak1 promotes atrial arrhythmogenesis under adrenergic stress, probably through post-translational and transcriptional modifications of key molecules that are critical to Ca2+ homeostasis. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Eunjeong Jung
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Rebecca Capel
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Congshan Jiang
- National Regional Children's Medical Center (Northwest); Key Laboratory of Precision Medicine to Pediatric Diseases of Shaanxi Province; Xi'an Key Laboratory of Children's Health and Diseases, Shaanxi Institute for Pediatric Diseases; Xi'an Children's Hospital, Affiliated Children's Hospital of Xi'an Jiaotong University. No. 69, Xijuyuan Lane, Xi'an 710003, People's Republic of China
| | - Elisa Venturi
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Georgiana Neagu
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Sarah Pearcey
- Paediatric Intensive Care, Addenbrooke's Hospital, Cambridge CB2 1QY, UK
| | - Yafei Zhou
- National Regional Children's Medical Center (Northwest); Key Laboratory of Precision Medicine to Pediatric Diseases of Shaanxi Province; Xi'an Key Laboratory of Children's Health and Diseases, Shaanxi Institute for Pediatric Diseases; Xi'an Children's Hospital, Affiliated Children's Hospital of Xi'an Jiaotong University. No. 69, Xijuyuan Lane, Xi'an 710003, People's Republic of China
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, 646000, People's Republic of China
| | - Yanmin Zhang
- National Regional Children's Medical Center (Northwest); Key Laboratory of Precision Medicine to Pediatric Diseases of Shaanxi Province; Xi'an Key Laboratory of Children's Health and Diseases, Shaanxi Institute for Pediatric Diseases; Xi'an Children's Hospital, Affiliated Children's Hospital of Xi'an Jiaotong University. No. 69, Xijuyuan Lane, Xi'an 710003, People's Republic of China
- Institute of Cardiovascular Sciences, Faculty of Medicine and Human Science, University of Manchester, Manchester, M13, 9GB UK
| | - Ming Lei
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
- Key Laboratory of Medical Electrophysiology of the Ministry of Education, Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, 646000, People's Republic of China
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3
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Liu H, Liu K, Dong Z. The Role of p21-Activated Kinases in Cancer and Beyond: Where Are We Heading? Front Cell Dev Biol 2021; 9:641381. [PMID: 33796531 PMCID: PMC8007885 DOI: 10.3389/fcell.2021.641381] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 02/03/2021] [Indexed: 12/12/2022] Open
Abstract
The p21-activated kinases (PAKs), downstream effectors of Ras-related Rho GTPase Cdc42 and Rac, are serine/threonine kinases. Biologically, PAKs participate in various cellular processes, including growth, apoptosis, mitosis, immune response, motility, inflammation, and gene expression, making PAKs the nexus of several pathogenic and oncogenic signaling pathways. PAKs were proved to play critical roles in human diseases, including cancer, infectious diseases, neurological disorders, diabetes, pancreatic acinar diseases, and cardiac disorders. In this review, we systematically discuss the structure, function, alteration, and molecular mechanisms of PAKs that are involved in the pathogenic and oncogenic effects, as well as PAK inhibitors, which may be developed and deployed in cancer therapy, anti-viral infection, and other diseases. Furthermore, we highlight the critical questions of PAKs in future research, which provide an opportunity to offer input and guidance on new directions for PAKs in pathogenic, oncogenic, and drug discovery research.
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Affiliation(s)
- Hui Liu
- Department of Pathophysiology, School of Basic Medical Sciences, The Academy of Medical Science, College of Medical, Zhengzhou University, Zhengzhou, China
| | - Kangdong Liu
- Department of Pathophysiology, School of Basic Medical Sciences, The Academy of Medical Science, College of Medical, Zhengzhou University, Zhengzhou, China.,China-US (Henan) Hormel Cancer Institute, Zhengzhou, China
| | - Zigang Dong
- Department of Pathophysiology, School of Basic Medical Sciences, The Academy of Medical Science, College of Medical, Zhengzhou University, Zhengzhou, China.,China-US (Henan) Hormel Cancer Institute, Zhengzhou, China
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4
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Biesiadecki BJ, Westfall MV. Troponin I modulation of cardiac performance: Plasticity in the survival switch. Arch Biochem Biophys 2019; 664:9-14. [PMID: 30684464 DOI: 10.1016/j.abb.2019.01.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 12/11/2018] [Accepted: 01/22/2019] [Indexed: 01/21/2023]
Abstract
Signaling complexes targeting the myofilament are essential in modulating cardiac performance. A central target of this signaling is cardiac troponin I (cTnI) phosphorylation. This review focuses on cTnI phosphorylation as a model for myofilament signaling, discussing key gaps and future directions towards understanding complex myofilament modulation of cardiac performance. Human heart cTnI is phosphorylated at 14 sites, giving rise to a complex modulatory network of varied functional responses. For example, while classical Ser23/24 phosphorylation mediates accelerated relaxation, protein kinase C phosphorylation of cTnI serves as a brake on contractile function. Additionally, the functional response of cTnI multi-site phosphorylation cannot necessarily be predicted from the response of individual sites alone. These complexities underscore the need for systematically evaluating single and multi-site phosphorylation on myofilament cellular and in vivo contractile function. Ultimately, a complete understanding of these multi-site responses requires work to establish site occupancy and dominance, kinase/phosphatase signaling balance, and the function of adaptive secondary phosphorylation. As cTnI phosphorylation is essential for modulating cardiac performance, future insight into the complex role of cTnI phosphorylation is important to establish sarcomere signaling in the healthy heart as well as identification of novel myofilament targets in the treatment of disease.
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Affiliation(s)
- Brandon J Biesiadecki
- Department of Physiology and Cell Biology, The Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, 43210, USA.
| | - Margaret V Westfall
- Department of Cardiac Surgery, University of Michigan, Ann Arbor, MI, 48109, USA.
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5
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Yang Y, Rong X, Lv X, Jiang W, Yang Y, Lai D, Xu S, Fu G. Inhibition of mevalonate pathway prevents ischemia-induced cardiac dysfunction in rats via RhoA-independent signaling pathway. Cardiovasc Ther 2018; 35. [PMID: 28665545 DOI: 10.1111/1755-5922.12285] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 05/31/2017] [Accepted: 06/27/2017] [Indexed: 11/27/2022] Open
Abstract
AIM We previously demonstrated that anoxia-mediated Ca2+ handling dysfunction could be ameliorated through inhibition of mevalonate pathway via RhoA- and Ras-related mechanisms in H9c2 cells. In this study, we further explored whether inhibition of mevalonate pathway is associated with cardiac remodeling and dysfunction in ischemic cardiomyopathy, and discussed the possible role of Ras, Rac and RhoA in cardiac dysfunction. METHODS We investigated the role of mevalonate pathway in cardiac remodeling and cardiomyocyte Ca2+ handling proteins expression in a rat model of cardiac dysfunction due to myocardial infarction (MI). After MI, adult male Sprague-Dawley rats were treated with drugs that antagonize key components in mevalonate pathway, including 3-hydroxy-3-methylglutaryl-CoA reductase, farnesyl pyrophosphate synthase, and Rho-kinase for 10 weeks. The protein expression of ryanodine receptor 2 (RyR2), sarcoplasmic reticulum Ca2+ ATPase (SERCA) 2a, phospholamban (PLB), phospho-PLB at serine-16 (PSer16-PLB), FKBP12.6, and RhoA as well as RyR2 and FKBP12.6 mRNA levels was evaluated. RESULTS Rosuvastatin and alendronate treatment prevented myocardial remodeling, improved cardiac function and reduced infarct size. Furthermore, rosuvastatin and alendronate promoted an increase in the protein expression of SERCA2a and PSer16-PLB/PLB ratio as well as partially restored the RyR2 and FKBP12.6 gene and protein expression. Fasudil failed to exert these beneficial effects. CONCLUSIONS These findings indicate that mevalonate pathway inhibition by rosuvastatin and alendronate prevents cardiac remodeling and dysfunction possibly through RhoA-independent mechanisms.
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Affiliation(s)
- Ying Yang
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Xiqing Rong
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Xue Lv
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Wenbing Jiang
- Department of Cardiology, Wenzhou People's Hospital, Wenzhou, China
| | - Yuan Yang
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Dongwu Lai
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Shiming Xu
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China.,Institute of Translational Medicine, College of Medicine, Zhejiang University, Hangzhou, China
| | - Guosheng Fu
- Department of Cardiology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China
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Wang Y, Wang S, Lei M, Boyett M, Tsui H, Liu W, Wang X. The p21-activated kinase 1 (Pak1) signalling pathway in cardiac disease: from mechanistic study to therapeutic exploration. Br J Pharmacol 2017; 175:1362-1374. [PMID: 28574147 DOI: 10.1111/bph.13872] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 05/12/2017] [Accepted: 05/17/2017] [Indexed: 01/01/2023] Open
Abstract
p21-activated kinase 1 (Pak1) is a member of the highly conserved family of serine/threonine protein kinases regulated by Ras-related small G-proteins, Cdc42/Rac1. It has been previously demonstrated to be involved in cardiac protection. Based on recent studies, this review provides an overview of the role of Pak1 in cardiac diseases including disrupted Ca2+ homoeostasis-related cardiac arrhythmias, adrenergic stress- and pressure overload-induced hypertrophy, and ischaemia/reperfusion injury. These findings demonstrate the important role of Pak1 mediated through the phosphorylation and transcriptional modification of hypertrophy and/or arrhythmia-related genes. This review also discusses the anti-arrhythmic and anti-hypertrophic, protective function of Pak1 and the beneficial effects of fingolimod (an FDA-approved sphingolipid drug), a Pak1 activator, and its ability to prevent arrhythmias and cardiac hypertrophy. These findings also highlight the therapeutic potential of Pak1 signalling in the treatment and prevention of cardiac diseases. LINKED ARTICLES This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.
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Affiliation(s)
- Yanwen Wang
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Shunyao Wang
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Ming Lei
- Department of Pharmacology, The University of Oxford, Oxford, UK
| | - Mark Boyett
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Hoyee Tsui
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Wei Liu
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
| | - Xin Wang
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
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7
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Abstract
Cardiac arrhythmias can follow disruption of the normal cellular electrophysiological processes underlying excitable activity and their tissue propagation as coherent wavefronts from the primary sinoatrial node pacemaker, through the atria, conducting structures and ventricular myocardium. These physiological events are driven by interacting, voltage-dependent, processes of activation, inactivation, and recovery in the ion channels present in cardiomyocyte membranes. Generation and conduction of these events are further modulated by intracellular Ca2+ homeostasis, and metabolic and structural change. This review describes experimental studies on murine models for known clinical arrhythmic conditions in which these mechanisms were modified by genetic, physiological, or pharmacological manipulation. These exemplars yielded molecular, physiological, and structural phenotypes often directly translatable to their corresponding clinical conditions, which could be investigated at the molecular, cellular, tissue, organ, and whole animal levels. Arrhythmogenesis could be explored during normal pacing activity, regular stimulation, following imposed extra-stimuli, or during progressively incremented steady pacing frequencies. Arrhythmic substrate was identified with temporal and spatial functional heterogeneities predisposing to reentrant excitation phenomena. These could arise from abnormalities in cardiac pacing function, tissue electrical connectivity, and cellular excitation and recovery. Triggering events during or following recovery from action potential excitation could thereby lead to sustained arrhythmia. These surface membrane processes were modified by alterations in cellular Ca2+ homeostasis and energetics, as well as cellular and tissue structural change. Study of murine systems thus offers major insights into both our understanding of normal cardiac activity and its propagation, and their relationship to mechanisms generating clinical arrhythmias.
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Affiliation(s)
- Christopher L-H Huang
- Physiological Laboratory and the Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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8
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Salhi HE, Hassel NC, Siddiqui JK, Brundage EA, Ziolo MT, Janssen PML, Davis JP, Biesiadecki BJ. Myofilament Calcium Sensitivity: Mechanistic Insight into TnI Ser-23/24 and Ser-150 Phosphorylation Integration. Front Physiol 2016; 7:567. [PMID: 28018230 PMCID: PMC5156683 DOI: 10.3389/fphys.2016.00567] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 11/08/2016] [Indexed: 11/14/2022] Open
Abstract
Troponin I (TnI) is a major regulator of cardiac muscle contraction and relaxation. During physiological and pathological stress, TnI is differentially phosphorylated at multiple residues through different signaling pathways to match cardiac function to demand. The combination of these TnI phosphorylations can exhibit an expected or unexpected functional integration, whereby the function of two phosphorylations are different than that predicted from the combined function of each individual phosphorylation alone. We have shown that TnI Ser-23/24 and Ser-150 phosphorylation exhibit functional integration and are simultaneously increased in response to cardiac stress. In the current study, we investigated the functional integration of TnI Ser-23/24 and Ser-150 to alter cardiac contraction. We hypothesized that Ser-23/24 and Ser-150 phosphorylation each utilize distinct molecular mechanisms to alter the TnI binding affinity within the thin filament. Mathematical modeling predicts that Ser-23/24 and Ser-150 phosphorylation affect different TnI affinities within the thin filament to distinctly alter the Ca2+-binding properties of troponin. Protein binding experiments validate this assertion by demonstrating pseudo-phosphorylated Ser-150 decreases the affinity of isolated TnI for actin, whereas Ser-23/24 pseudo-phosphorylation is not different from unphosphorylated. Thus, our data supports that TnI Ser-23/24 affects TnI-TnC binding, while Ser-150 phosphorylation alters TnI-actin binding. By measuring force development in troponin-exchanged skinned myocytes, we demonstrate that the Ca2+ sensitivity of force is directly related to the amount of phosphate present on TnI. Furthermore, we demonstrate that Ser-150 pseudo-phosphorylation blunts Ser-23/24-mediated decreased Ca2+-sensitive force development whether on the same or different TnI molecule. Therefore, TnI phosphorylations can integrate across troponins along the myofilament. These data demonstrate that TnI Ser-23/24 and Ser-150 phosphorylation regulates muscle contraction in part by modulating different TnI interactions in the thin filament and it is the combination of these differential mechanisms that provides understanding of their functional integration.
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Affiliation(s)
| | | | | | | | | | | | | | - Brandon J. Biesiadecki
- Department of Physiology and Cell Biology and Davis Heart and Lung Research Institute, Ohio State UniversityColumbus, OH, USA
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9
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Egom EEA, Bae JS, Capel R, Richards M, Ke Y, Pharithi RB, Maher V, Kruzliak P, Lei M. Effect of sphingosine-1-phosphate on L-type calcium current and Ca2+ transient in rat ventricular myocytes. Mol Cell Biochem 2016; 419:83-92. [DOI: 10.1007/s11010-016-2752-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 06/21/2016] [Indexed: 01/05/2023]
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10
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Wang Y, Tsui H, Bolton EL, Wang X, Huang CLH, Solaro RJ, Ke Y, Lei M. Novel insights into mechanisms for Pak1-mediated regulation of cardiac Ca(2+) homeostasis. Front Physiol 2015; 6:76. [PMID: 25852566 PMCID: PMC4362298 DOI: 10.3389/fphys.2015.00076] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 02/25/2015] [Indexed: 11/13/2022] Open
Abstract
A series of recent studies report novel roles for Pak1, a key member of the highly conserved family of serine-threonine protein kinases regulated by Ras-related small G-proteins, Cdc42/Rac1, in cardiac physiology and cardioprotection. Previous studies had identified Pak1 in the regulation of hypertrophic remodeling that could potentially lead to heart failure. This article provides a review of more recent findings on the roles of Pak1 in cardiac Ca(2+) homeostasis. These findings identified crucial roles for Pak1 in cardiomyocyte Ca(2+) handling and demonstrated that it functions through unique mechanisms involving regulation of the post-transcriptional activity of key Ca(2+)-handling proteins, including the expression of Ca(2+)-ATPase SERCA2a, along with the speculative possibility of an involvement in the maintenance of transverse (T)-tubular structure. They highlight important regulatory functions of Pak1 in Ca(2+) homeostasis in cardiac cells, and identify novel potential therapeutic strategies directed at manipulation of Pak1 signaling for the management of cardiac disease, particularly heart failure.
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Affiliation(s)
- Yanwen Wang
- Department of Pharmacology, University of Oxford Oxford, UK
| | - Hoyee Tsui
- Faculty of Life Science, University of Manchester Manchester, UK
| | - Emma L Bolton
- Department of Pharmacology, University of Oxford Oxford, UK
| | - Xin Wang
- Faculty of Life Science, University of Manchester Manchester, UK
| | | | - R John Solaro
- Department of Physiology and Biophysics, University of Illinois Chicago, IL, USA
| | - Yunbo Ke
- Department of Physiology and Biophysics, University of Illinois Chicago, IL, USA
| | - Ming Lei
- Department of Pharmacology, University of Oxford Oxford, UK
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11
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Ke Y, Wang X, Jin XY, Solaro RJ, Lei M. PAK1 is a novel cardiac protective signaling molecule. Front Med 2014; 8:399-403. [PMID: 25416031 DOI: 10.1007/s11684-014-0380-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Accepted: 10/15/2014] [Indexed: 12/19/2022]
Abstract
We review here the novel cardiac protective effects of the multifunctional enzyme, p21-activated kinase 1 (PAK1), a member of a serine/threonine protein kinase family. Despite the large body of evidence from studies in noncardiac tissue indicating that PAK1 activity is key in the regulation of a number of cellular functions, the role of PAK1 in the heart has only been revealed over the past few years. In this review, we assemble an overview of the recent findings on PAK1 signaling in the heart, particularly its cardiac protective effects. We present a model for PAK1 signaling that provides a mechanism for specifically affecting cardiac cellular processes in which regulation of protein phosphorylation states by protein phosphatase 2A (PP2A) predominates.We discuss the anti-adrenergic and antihypertrophic cardiac protective effects of PAK1, as well as its role in maintaining ventricular Ca(2+) homeostasis and electrophysiological stability under physiological, β-adrenergic and hypertrophic stress conditions.
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Affiliation(s)
- Yunbo Ke
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, 60612, USA
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12
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Abstract
Our work and others’ over the past few years have led to the identification of new roles of PAK1 in cardiac physiology, such as the regulation of cardiac ion channel and actomyosin function. More recent studies have revealed that PAK1-deficient mice were vulnerable to cardiac hypertrophy and readily progress to failure under sustained pressure overload and susceptible to ischemia/reperfusion injury. Our further study indicated that the PAK1 activator FTY720 was able to prevent this pressure overload-induced hypertrophy in wild-type mice without compromising their cardiac functions. A cardiac protective effect against ischemia/reperfusion injury by FTY720 was also observed in both rat and mouse models by us and others. Thus, these studies suggest that PAK1 is more important in the heart than previously thought, in particular a therapeutic potential of PAK1 activators. In the future, in-depth investigations are required to further substantiate our hypotheses on mechanisms for PAK1 function in the heart and to explore a therapeutic potential of FTY720 and other PAK1 activators in heart disease conditions.
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Affiliation(s)
- Yunbo Ke
- Department of Physiology and Biophysics and Center for Cardiovascular Research; University of Illinois at Chicago; Chicago, IL USA
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13
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Dostal DE, Feng H, Nizamutdinov D, Golden HB, Afroze SH, Dostal JD, Jacob JC, Foster DM, Tong C, Glaser S, Gerilechaogetu F. Mechanosensing and Regulation of Cardiac Function. ACTA ACUST UNITED AC 2014; 5:314. [PMID: 25485172 PMCID: PMC4255974 DOI: 10.4172/2155-9880.1000314] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The role of mechanical force as an important regulator of structure and function of mammalian cells, tissues, and organs has recently been recognized. However, mechanical overload is a pathogenesis or comorbidity existing in a variety of heart diseases, such as hypertension, aortic regurgitation and myocardial infarction. Physical stimuli sensed by cells are transmitted through intracellular signal transduction pathways resulting in altered physiological responses or pathological conditions. Emerging evidence from experimental studies indicate that β1-integrin and the angiotensin II type I (AT1) receptor play critical roles as mechanosensors in the regulation of heart contraction, growth and leading to heart failure. Integrin link the extracellular matrix and the intracellular cytoskeleton to initiate the mechanical signalling, whereas, the AT1 receptor could be activated by mechanical stress through an angiotensin-II-independent mechanism. Recent studies show that both Integrin and AT1 receptor and their downstream signalling factors including MAPKs, AKT, FAK, ILK and GTPase regulate heart function in cardiac myocytes. In this review we describe the role of mechanical sensors residing within the plasma membrane, mechanical sensor induced downstream signalling factors and its potential roles in cardiac contraction and growth.
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Affiliation(s)
- David E Dostal
- Central Texas Veterans Health Care System, Temple, Texas, USA ; Division of Molecular Cardiology, Cardiovascular Research Institute, Texas A&M University Health Science Centre, College of Medicine, Temple, Texas, USA
| | - Hao Feng
- Division of Molecular Cardiology, Cardiovascular Research Institute, Texas A&M University Health Science Centre, College of Medicine, Temple, Texas, USA
| | - Damir Nizamutdinov
- Division of Molecular Cardiology, Cardiovascular Research Institute, Texas A&M University Health Science Centre, College of Medicine, Temple, Texas, USA
| | - Honey B Golden
- Division of Molecular Cardiology, Cardiovascular Research Institute, Texas A&M University Health Science Centre, College of Medicine, Temple, Texas, USA
| | - Syeda H Afroze
- Scott & White Healthcare - Digestive Disease Research Centre, Temple, Texas, USA
| | - Joseph D Dostal
- Division of Molecular Cardiology, Cardiovascular Research Institute, Texas A&M University Health Science Centre, College of Medicine, Temple, Texas, USA
| | - John C Jacob
- Division of Molecular Cardiology, Cardiovascular Research Institute, Texas A&M University Health Science Centre, College of Medicine, Temple, Texas, USA
| | - Donald M Foster
- Central Texas Veterans Health Care System, Temple, Texas, USA
| | - Carl Tong
- Systems Biology and Translational Medicine, the Texas A&M University Health Science Centre, College of Medicine, Temple, Texas, USA
| | - Shannon Glaser
- Central Texas Veterans Health Care System, Temple, Texas, USA ; Scott & White Healthcare - Digestive Disease Research Centre, Temple, Texas, USA
| | - Fnu Gerilechaogetu
- Division of Molecular Cardiology, Cardiovascular Research Institute, Texas A&M University Health Science Centre, College of Medicine, Temple, Texas, USA
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14
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Loirand G, Sauzeau V, Pacaud P. Small G Proteins in the Cardiovascular System: Physiological and Pathological Aspects. Physiol Rev 2013; 93:1659-720. [DOI: 10.1152/physrev.00021.2012] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Small G proteins exist in eukaryotes from yeast to human and constitute the Ras superfamily comprising more than 100 members. This superfamily is structurally classified into five families: the Ras, Rho, Rab, Arf, and Ran families that control a wide variety of cell and biological functions through highly coordinated regulation processes. Increasing evidence has accumulated to identify small G proteins and their regulators as key players of the cardiovascular physiology that control a large panel of cardiac (heart rhythm, contraction, hypertrophy) and vascular functions (angiogenesis, vascular permeability, vasoconstriction). Indeed, basal Ras protein activity is required for homeostatic functions in physiological conditions, but sustained overactivation of Ras proteins or spatiotemporal dysregulation of Ras signaling pathways has pathological consequences in the cardiovascular system. The primary object of this review is to provide a comprehensive overview of the current progress in our understanding of the role of small G proteins and their regulators in cardiovascular physiology and pathologies.
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Affiliation(s)
- Gervaise Loirand
- INSERM, UMR S1087; University of Nantes; and CHU Nantes, l'Institut du Thorax, Nantes, France
| | - Vincent Sauzeau
- INSERM, UMR S1087; University of Nantes; and CHU Nantes, l'Institut du Thorax, Nantes, France
| | - Pierre Pacaud
- INSERM, UMR S1087; University of Nantes; and CHU Nantes, l'Institut du Thorax, Nantes, France
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15
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Kirk JA, Zhang P, Murphy AM, Van Eyk JE. Troponin I alterations detected by multiple-reaction monitoring: how might this impact the study of heart failure? Expert Rev Proteomics 2013; 10:5-8. [PMID: 23414352 DOI: 10.1586/epr.12.77] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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16
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DeSantiago J, Bare DJ, Ke Y, Sheehan KA, Solaro RJ, Banach K. Functional integrity of the T-tubular system in cardiomyocytes depends on p21-activated kinase 1. J Mol Cell Cardiol 2013; 60:121-8. [PMID: 23612118 PMCID: PMC3679655 DOI: 10.1016/j.yjmcc.2013.04.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 03/06/2013] [Accepted: 04/12/2013] [Indexed: 12/30/2022]
Abstract
p21-activated kinase (Pak1), a serine-threonine protein kinase, regulates cytoskeletal dynamics and cell motility. Recent experiments further demonstrate that loss of Pak1 results in exaggerated hypertrophic growth in response to pathophysiological stimuli. Calcium (Ca) signaling plays an important role in the regulation of transcription factors involved in hypertrophic remodeling. Here we aimed to determine the role of Pak1 in cardiac excitation-contraction coupling (ECC). Ca transients were recorded in isolated, ventricular myocytes (VMs) from WT and Pak1(-/-) mice. Pak1(-/-) Ca transients had a decreased amplitude, prolonged rise time and delayed recovery time. Di-8-ANNEPS staining revealed a decreased T-tubular density in Pak1(-/-) VMs that coincided with decreased cell capacitance and increased dis-synchrony of Ca induced Ca release (CICR) at individual release units. These changes were not observed in atrial myocytes of Pak1(-/-) mice where the T-tubular system is only sparsely developed. Experiments in cultured rabbit VMs supported a role of Pak1 in the maintenance of the T-tubular structure. T-tubular density in rabbit VMs significantly decreased within 24h of culture. This was accompanied by a decrease of the Ca transient amplitude and a prolongation of its rise time. However, overexpression of constitutively active Pak1 in VMs attenuated the structural remodeling as well as changes in ECC. The results provide significant support for a prominent role of Pak1 activity not only in the functional regulation of ECC but for the structural maintenance of the T-tubular system whose remodeling is an integral feature of hypertrophic remodeling.
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Affiliation(s)
- Jaime DeSantiago
- Center for Cardiovascular Research, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
- Dept. of Medicine, Section of Cardiology, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
| | - Dan J Bare
- Center for Cardiovascular Research, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
- Dept. of Medicine, Section of Cardiology, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
| | - Yunbo Ke
- Center for Cardiovascular Research, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
- Dept. of Physiology and Biophysics, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
| | - Katherine A. Sheehan
- Center for Cardiovascular Research, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
- Dept. of Physiology and Biophysics, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
| | - R. John Solaro
- Center for Cardiovascular Research, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
- Dept. of Physiology and Biophysics, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
| | - Kathrin Banach
- Center for Cardiovascular Research, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
- Dept. of Medicine, Section of Cardiology, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA
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17
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Walker LA, Fullerton DA, Buttrick PM. Contractile protein phosphorylation predicts human heart disease phenotypes. Am J Physiol Heart Circ Physiol 2013; 304:H1644-50. [PMID: 23564307 DOI: 10.1152/ajpheart.00957.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Human heart failure has been associated with a low level of thin-filament protein phosphorylation and an increase in calcium sensitivity of contraction relative to both "control" human heart tissue and tissue from small animal models. However, diverse strategies of human tissue procurement and the reliance on tissue obtained from subjects with end-stage heart failure suggest this may be an incomplete characterization. Therefore, we evaluated cardiac left ventricular (LV) biopsy samples from patients with aortic stenosis undergoing valve replacement who presented either with LV hypertrophy and preserved systolic function (Hyp) or with LV dilation and reduced ejection fraction (Dil). In Hyp, total troponin I (TnI) phosphorylation was markedly increased and myosin light chain 2 (MLC2) phosphorylation was unchanged relative to a control group of patients with normal LV function. Conversely, in Dil, total TnI phosphorylation was significantly reduced compared with control subjects and MLC2 phosphorylation was increased. Site-specific analysis of TnI phosphorylation revealed phenotype-specific differences such that Hyp samples demonstrated significant increases in phosphorylation at serine 22/23 and Dil samples had significant decreases at serine 43. The ratio of phosphorylation at the two sites was biased toward serine 22/23 in Hyp and toward serine 43/45 in Dil. Western blot analysis showed that protein phosphatase-1 was reduced in Hyp and protein phosphatase-2 was reduced in Dil. These data suggest that posttranslational modifications of sarcomeric proteins, both singly and in combination, are stage specific. Defining these changes in progressive heart disease may provide important diagnostic and treatment information.
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Affiliation(s)
- Lori A Walker
- Division of Cardiology, Department of Medicine, University of Colorado Denver, Aurora, CO 80045, USA.
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18
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Abstract
We focus here on the modulation of thin filament activity by cardiac troponin I phosphorylation as an integral and adaptive mechanism in cardiac homeostasis and as a mechanism vulnerable to maladaptive response to stress. We discuss a current concept of cardiac troponin I function in the A-band region of the sarcomere and potential signaling to cardiac troponin I in a network involving the ends of the thin filaments at the Z-disk and the M-band regions. The cardiac sarcomere represents a remarkable set of interacting proteins that functions not only as a molecular machine generating the heartbeat but also as a hub of signaling. We review how phosphorylation signaling to cardiac troponin I is integrated, with parallel signals controlling excitation-contraction coupling, hypertrophy, and metabolism.
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Affiliation(s)
- R John Solaro
- Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, College of Medicine, Chicago, IL 60612, USA.
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19
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Wang H, Wang L, Song L, Zhang YW, Ye J, Xu RX, Shi N, Meng XM. TNNI3K is a novel mediator of myofilament function and phosphorylates cardiac troponin I. Braz J Med Biol Res 2013; 46:128-37. [PMID: 23369981 PMCID: PMC3854359 DOI: 10.1590/1414-431x20122515] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 10/22/2012] [Indexed: 11/21/2022] Open
Abstract
The phosphorylation of cardiac troponin I (cTnI) plays an important role in the contractile dysfunction associated with heart failure. Human cardiac troponin I-interacting kinase (TNNI3K) is a novel cardiac-specific functional kinase that can bind to cTnI in a yeast two-hybrid screen. The purpose of this study was to investigate whether TNNI3K can phosphorylate cTnI at specific sites and to examine whether the phosphorylation of cTnI caused by TNNI3K can regulate cardiac myofilament contractile function. Co-immunoprecipitation was performed to confirm that TNNI3K could interact with cTnI. Kinase assays further indicated that TNNI3K did not phosphorylate cTnI at Ser23/24 and Ser44, but directly phosphorylated Ser43 and Thr143 in vitro. The results obtained for adult rat cardiomyocytes also indicated that enhanced phosphorylation of cTnI at Ser43 and Thr143 correlated with rTNNI3K (rat TNNI3K) overexpression, and phosphorylation was reduced when rTNNI3K was knocked down. To determine the contractile function modulated by TNNI3K-mediated phosphorylation of cTnI, cardiomyocyte contraction was studied in adult rat ventricular myocytes. The contraction of cardiomyocytes increased with rTNNI3K overexpression and decreased with rTNNI3K knockdown. We conclude that TNNI3K may be a novel mediator of cTnI phosphorylation and contribute to the regulation of cardiac myofilament contraction function.
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Affiliation(s)
- Hui Wang
- Chinese Academy of Medical Sciences and Peking Union Medical College, Core Laboratory, Fu Wai Hospital and Cardiovascular Institute, Beijing, China
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20
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Staser K, Shew MA, Michels EG, Mwanthi MM, Yang FC, Clapp DW, Park SJ. A Pak1-PP2A-ERM signaling axis mediates F-actin rearrangement and degranulation in mast cells. Exp Hematol 2012; 41:56-66.e2. [PMID: 23063725 DOI: 10.1016/j.exphem.2012.10.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 10/01/2012] [Accepted: 10/06/2012] [Indexed: 01/12/2023]
Abstract
Mast cells coordinate allergy and allergic asthma and are crucial cellular targets in therapeutic approaches to inflammatory disease. Allergens cross-link immunoglobulin E bound at high-affinity receptors on the mast cell's surface, causing release of preformed cytoplasmic granules containing inflammatory molecules, including histamine, a principal effector of fatal septic shock. Both p21 activated kinase 1 (Pak1) and protein phosphatase 2A (PP2A) modulate mast cell degranulation, but the molecular mechanisms underpinning these observations and their potential interactions in common or disparate pathways are unknown. In this study, we use genetic and other approaches to show that Pak1's kinase-dependent interaction with PP2A potentiates PP2A's subunit assembly and activation. PP2A then dephosphorylates threonine 567 of Ezrin/Radixin/Moesin (ERM) molecules that have been shown to couple F-actin to the plasma membrane in other cell systems. In our study, the activity of this Pak1-PP2A-ERM axis correlates with impaired systemic histamine release in Pak1(-/-) mice and defective F-actin rearrangement and impaired degranulation in Ezrin disrupted (Mx1Cre(+)Ezrin(flox/flox)) primary mast cells. This heretofore unknown mechanism of mast cell degranulation provides novel therapeutic targets in allergy and asthma and may inform studies of kinase regulation of cytoskeletal dynamics in other cell lineages.
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Affiliation(s)
- Karl Staser
- Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
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21
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A novel player in cellular hypertrophy: Giβγ/PI3K-dependent activation of the RacGEF TIAM-1 is required for α₁-adrenoceptor induced hypertrophy in neonatal rat cardiomyocytes. J Mol Cell Cardiol 2012; 53:165-75. [PMID: 22564263 DOI: 10.1016/j.yjmcc.2012.04.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Revised: 04/25/2012] [Accepted: 04/26/2012] [Indexed: 01/08/2023]
Abstract
Activation of α(1)-adrenoceptors (α(1)-AR) by high catecholamine levels, e.g. in heart failure, is thought to be a driving force of cardiac hypertrophy. In this context several downstream mediators and cascades have been identified to potentially play a role in cardiomyocyte hypertrophy. One of these proteins is the monomeric G protein Rac1. However, until now it is unclear how this essential G protein is activated by α(1)-AR agonists and what are the downstream targets inducing cellular growth. By using protein-based as well as pharmacological inhibitors and the shRNA technique, we demonstrate that in neonatal rat cardiomyocytes (NRCM) Rac1 is activated via a cascade involving the α(1A)-AR subtype, G(i)βγ, the phosphoinositide-3'-kinase and the guanine nucleotide exchange factor Tiam1. We further demonstrate that this signaling induces an increase in protein synthesis, cell size and atrial natriuretic peptide expression. We identified the p21-activated kinase 2 (PAK2) as a downstream effector of Rac1 and were able to link this cascade to the activation of the pro-hypertrophic kinases ERK1/2 and p90RSK. Our data thus reveal a prominent role of the α(1A)-AR/G(i)βγ/Tiam1-mediated activation of Rac1 and its effector PAK2 in the induction of hypertrophy in NRCM.
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22
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Zhang T, Lu X, Arnold P, Liu Y, Baliga R, Huang H, Bauer JA, Liu Y, Feng Q. Mitogen-activated protein kinase phosphatase-1 inhibits myocardial TNF-α expression and improves cardiac function during endotoxemia. Cardiovasc Res 2011; 93:471-9. [PMID: 22198506 DOI: 10.1093/cvr/cvr346] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS Myocardial tumour necrosis factor-α (TNF-α) expression induces cardiac dysfunction in endotoxemia. The aim of this study was to investigate the role of mitogen-activated protein kinase phosphatase-1 (MKP1) pathway in myocardial TNF-α expression and cardiac function during endotoxemia. METHODS AND RESULTS Lipopolysaccharide (LPS) increased MKP1 expression in the myocardium in vivo and in cultured neonatal cardiomyocytes in vitro. LPS-induced extracellular signal-regulated kinase (ERK) 1/2 and p38 phosphorylation in the myocardium was prolonged in MKP1(-/-) mice. Myocardial TNF-α mRNA and protein levels were enhanced in MKP1(-/-) compared with wild-type (WT) mice in endotoxemia, leading to a further decrease in cardiac function. To study if Rac1/p21-activated kinase 1 (PAK1) signalling regulates MKP1 expression, cardiomyocytes were treated with LPS. Inhibition of Rac1 and PAK1 by a dominant negative Rac1 adenovirus (Ad-Rac1N17) and PAK1 siRNA, respectively, blocked LPS-induced MKP1 expression in cardiomyocytes. PAK1 siRNA also decreased p38 and c-Jun N-terminal kinase (JNK) activation, and TNF-α expression induced by LPS. Furthermore, deficiency in either Rac1 or JNK1 decreased myocardial MKP1 expression in endotoxemic mice. CONCLUSION LPS activates the Rac1/PAK1 pathway, which increases myocardial MKP1 expression via JNK1. MKP1 attenuates ERK1/2 and p38 activation, inhibits myocardial TNF-α expression, and improves cardiac function in endotoxemia. Thus, MKP1 represents an important negative feedback mechanism limiting pro-inflammatory response in the heart during sepsis.
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Affiliation(s)
- Ting Zhang
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada N6A 5C1
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23
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Cheng G, Kasiganesan H, Baicu CF, Wallenborn JG, Kuppuswamy D, Cooper G. Cytoskeletal role in protection of the failing heart by β-adrenergic blockade. Am J Physiol Heart Circ Physiol 2011; 302:H675-87. [PMID: 22081703 DOI: 10.1152/ajpheart.00867.2011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Formation of a dense microtubule network that impedes cardiac contraction and intracellular transport occurs in severe pressure overload hypertrophy. This process is highly dynamic, since microtubule depolymerization causes striking improvement in contractile function. A molecular etiology for this cytoskeletal alteration has been defined in terms of type 1 and type 2A phosphatase-dependent site-specific dephosphorylation of the predominant myocardial microtubule-associated protein (MAP)4, which then decorates and stabilizes microtubules. This persistent phosphatase activation is dependent upon ongoing upstream activity of p21-activated kinase-1, or Pak1. Because cardiac β-adrenergic activity is markedly and continuously increased in decompensated hypertrophy, and because β-adrenergic activation of cardiac Pak1 and phosphatases has been demonstrated, we asked here whether the highly maladaptive cardiac microtubule phenotype seen in pathological hypertrophy is based on β-adrenergic overdrive and thus could be reversed by β-adrenergic blockade. The data in this study, which were designed to answer this question, show that such is the case; that is, β(1)- (but not β(2)-) adrenergic input activates this pathway, which consists of Pak1 activation, increased phosphatase activity, MAP4 dephosphorylation, and thus the stabilization of a dense microtubule network. These data were gathered in a feline model of severe right ventricular (RV) pressure overload hypertrophy in response to tight pulmonary artery banding (PAB) in which a stable, twofold increase in RV mass is reached by 2 wk after pressure overloading. After 2 wk of hypertrophy induction, these PAB cats during the following 2 wk either had no further treatment or had β-adrenergic blockade. The pathological microtubule phenotype and the severe RV cellular contractile dysfunction otherwise seen in this model of RV hypertrophy (PAB No Treatment) was reversed in the treated (PAB β-Blockade) cats. Thus these data provide both a specific etiology and a specific remedy for the abnormal microtubule network found in some forms of pathological cardiac hypertrophy.
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Affiliation(s)
- Guangmao Cheng
- Gazes Cardiac Research Institute, PO Box 250773, Medical Univ. of South Carolina, 114 Doughty St., Charleston, SC 29403, USA
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24
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Monasky MM, Taglieri DM, Patel BG, Chernoff J, Wolska BM, Ke Y, Solaro RJ. p21-activated kinase improves cardiac contractility during ischemia-reperfusion concomitant with changes in troponin-T and myosin light chain 2 phosphorylation. Am J Physiol Heart Circ Physiol 2011; 302:H224-30. [PMID: 22037191 DOI: 10.1152/ajpheart.00612.2011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
p21-activated kinase 1 (Pak1) is a serine/threonine kinase that activates protein phosphatase 2a, resulting in the dephosphorylation of cardiac proteins and increased myofilament Ca(2+) sensitivity. Emerging evidence indirectly indicates a role for Pak1 in ischemia-reperfusion (I/R), but direct evidence is lacking. We hypothesize that activation of the Pak1 signaling pathway is a cardioprotective mechanism that prevents or reverses the detrimental effects of ischemic injury by inducing posttranslational modifications in myofilament proteins that ultimately improve cardiac contractility following ischemic insult. In the present study, we subjected ex vivo hearts from wild-type (WT) and Pak1-knockout (KO) mice to 20 min of global cardiac ischemia followed by 30 min of reperfusion. In the absence of Pak1, there was an exacerbation of the increased end-diastolic pressure and reduced left ventricular developed pressure occurring after I/R injury. ProQ analysis revealed an increase in troponin-T phosphorylation at baseline in Pak1-KO hearts compared with WT. Significantly decreased myosin light chain 2 (MLC2) phosphorylation in Pak1-KO hearts compared with WT after I/R injury was confirmed by Western immunoblotting. These data indicate that Pak1-KO hearts have reduced recovery of myocardial performance after global I/R injury concomitant with changes in troponin-T and MLC2 phosphorylation. Finally, a protein-protein association between Pak1 and MLC2, and Pak1 and troponin-T, was determined by coimmunoprecipitation. Thus, results of our study provide a basis for targeting a novel pathway, including Pak1, in the therapies for patients with ischemic events.
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Affiliation(s)
- Michelle M Monasky
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, 60612-7342, USA
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25
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Taglieri DM, Monasky MM, Knezevic I, Sheehan KA, Lei M, Wang X, Chernoff J, Wolska BM, Ke Y, Solaro RJ. Ablation of p21-activated kinase-1 in mice promotes isoproterenol-induced cardiac hypertrophy in association with activation of Erk1/2 and inhibition of protein phosphatase 2A. J Mol Cell Cardiol 2011; 51:988-96. [PMID: 21971074 DOI: 10.1016/j.yjmcc.2011.09.016] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 09/09/2011] [Accepted: 09/11/2011] [Indexed: 12/16/2022]
Abstract
Earlier investigations in our lab indicated an anti-adrenergic effect induced by activation of p21-activated kinase (Pak-1) and protein phosphatase 2A (PP2A). Our objective was to test the hypothesis that Pak-1/PP2A is a signaling cascade controlling stress-induced cardiac growth. We determined the effects of ablation of the Pak-1 gene on the response of the myocardium to chronic stress of isoproterenol (ISO) administration. Wild-type (WT) and Pak-1-knockout (Pak-1-KO) mice were randomized into six groups to receive either ISO, saline (CTRL), or ISO and FR180204, a selective inhibitor of Erk1/2. Echocardiography revealed that hearts of the Pak-1-KO/ISO group had increased LV fractional shortening, reduced LV chamber volume in diastole and systole, increased cardiac hypertrophy, and enhanced transmitral early filling deceleration time, compared to all other groups. The changes were associated with an increase in relative Erk1/2 activation in Pak-1-KO/ISO mice versus all other groups. ISO-induced cardiac hypertrophy and Erk1/2 activation in Pak-1-KO/ISO were attenuated when the selective Erk1/2 inhibitor FR180204 was administered. Immunoprecipitation showed an association between Pak-1, PP2A, and Erk1/2. Cardiac myocytes infected with an adenoviral vector expressing constitutively active Pak-1 showed a repression of Erk1/2 activation. p38 MAPK phosphorylation was decreased in Pak-1-KO/ISO and Pak-1-KO/CTRL mice compared to WT. Levels of phosphorylated PP2A were increased in ISO-treated Pak-1-KO mice, indicating reduced phosphatase activity. Maximum Ca(2+)-activated tension in detergent-extracted bundles of papillary fibers from ISO-treated Pak-1-KO mice was higher than in all other groups. Analysis of cTnI phosphorylation indicated that compared to WT, ISO-induced phosphorylation of cTnI was blunted in Pak-1-KO mice. Active Pak-1 is a natural inhibitor of Erk1/2 and a novel anti-hypertrophic signaling molecule upstream of PP2A.
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Affiliation(s)
- Domenico M Taglieri
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, 835 S. Wolcott Ave, M/C 901, Chicago, IL 60612-7342, USA.
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26
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Ai X, Jiang A, Ke Y, Solaro RJ, Pogwizd SM. Enhanced activation of p21-activated kinase 1 in heart failure contributes to dephosphorylation of connexin 43. Cardiovasc Res 2011; 92:106-14. [PMID: 21727092 DOI: 10.1093/cvr/cvr163] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS We previously showed decreased cellular coupling and dephosphorylation of the gap junctional protein connexin 43 (Cx43) in left ventricular (LV) myocytes from an arrhythmogenic rabbit model of non-ischaemic heart failure (HF) that was associated with a 2.5-fold increase in the amount of protein phosphatase type 2A (PP2A) co-localized with Cx43. Here, we further explore the molecular mechanisms of enhanced dephosphorylation of Cx43 in HF. p21-activated kinase 1 (PAK1) is a serine-threonine protein kinase that has been shown to activate PP2A. METHODS AND RESULTS We found that total PAK1 and activated PAK1 (PAK1-P(Thr423)) were both increased in HF rabbit LV (vs. controls). PAK1 co-immunoprecipitated (co-IP'd) with Cx43 protein and, with HF, co-IP'd PAK1 and PAK1-P(Thr423) were increased. With failing human LV, PAK1 total protein and PAK1-P(Thr423) were also increased globally and locally (co-IP'd with Cx43). To further explore the role of PAK1 in modulating Cx43 dephosphorylation and intercellular coupling, we overexpressed active PAK1 in isolated LV myocytes from control rabbits and in HEK293 cells with genetically modified overexpression of Cx43 (HEK293-Cx43). PAK1 overexpression in both rabbit myocytes and HEK293-Cx43 cells significantly increased PP2A activity (globally and at the level of Cx43), increased dephosphorylated Cx43, and markedly reduced intercellular dye coupling. These effects were attenuated with PP2A inhibition using okadaic acid (10 nM). CONCLUSIONS PAK1 and PP2A are integral components of a macromolecular complex with cardiac Cx43, and increased activation of associated PAK1 can contribute to enhanced Cx43 dephosphorylation and impaired intercellular coupling that may underlie slow conduction in HF.
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Affiliation(s)
- Xun Ai
- Department of Medicine, University of Alabama at Birmingham, 1670, University Blvd, Birmingham, AL, USA
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27
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Solaro RJ, Sheehan KA, Lei M, Ke Y. The curious role of sarcomeric proteins in control of diverse processes in cardiac myocytes. ACTA ACUST UNITED AC 2011; 136:13-9. [PMID: 20584888 PMCID: PMC2894547 DOI: 10.1085/jgp.201010462] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- R John Solaro
- Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago College of Medicine, Chicago, IL 60611, USA.
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28
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Cheng G, Takahashi M, Shunmugavel A, Wallenborn JG, DePaoli-Roach AA, Gergs U, Neumann J, Kuppuswamy D, Menick DR, Cooper G. Basis for MAP4 dephosphorylation-related microtubule network densification in pressure overload cardiac hypertrophy. J Biol Chem 2010; 285:38125-40. [PMID: 20889984 DOI: 10.1074/jbc.m110.148650] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Increased activity of Ser/Thr protein phosphatases types 1 (PP1) and 2A (PP2A) during maladaptive cardiac hypertrophy contributes to cardiac dysfunction and eventual failure, partly through effects on calcium metabolism. A second maladaptive feature of pressure overload cardiac hypertrophy that instead leads to heart failure by interfering with cardiac contraction and intracellular transport is a dense microtubule network stabilized by decoration with microtubule-associated protein 4 (MAP4). In an earlier study we showed that the major determinant of MAP4-microtubule affinity, and thus microtubule network density and stability, is site-specific MAP4 dephosphorylation at Ser-924 and to a lesser extent at Ser-1056; this was found to be prominent in hypertrophied myocardium. Therefore, in seeking the etiology of this MAP4 dephosphorylation, we looked here at PP2A and PP1, as well as the upstream p21-activated kinase 1, in maladaptive pressure overload cardiac hypertrophy. The activity of each was increased persistently during maladaptive hypertrophy, and overexpression of PP2A or PP1 in normal hearts reproduced both the microtubule network phenotype and the dephosphorylation of MAP4 Ser-924 and Ser-1056 seen in hypertrophy. Given the major microtubule-based abnormalities of contractile and transport function in maladaptive hypertrophy, these findings constitute a second important mechanism for phosphatase-dependent pathology in the hypertrophied and failing heart.
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Affiliation(s)
- Guangmao Cheng
- Gazes Cardiac Research Institute, Cardiology Division, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29403, USA
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Ouyang Y, Mamidi R, Jayasundar JJ, Chandra M, Dong WJ. Structural and kinetic effects of PAK3 phosphorylation mimic of cTnI(S151E) on the cTnC-cTnI interaction in the cardiac thin filament. J Mol Biol 2010; 400:1036-45. [PMID: 20540949 DOI: 10.1016/j.jmb.2010.06.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 05/29/2010] [Accepted: 06/03/2010] [Indexed: 12/01/2022]
Abstract
Residue Ser151 of cardiac troponin I (cTnI) is known to be phosphorylated by p21-activated kinase 3 (PAK3). It has been found that PAK3-mediated phosphorylation of cTnI induces an increase in the sensitivity of myofilament to Ca(2+), but the detailed mechanism is unknown. We investigated how the structural and kinetic effects mediated by pseudo-phosphorylation of cTnI (S151E) modulates Ca(2+)-induced activation of cardiac thin filaments. Using steady-state, time-resolved Förster resonance energy transfer (FRET) and stopped-flow kinetic measurements, we monitored Ca(2+)-induced changes in cTnI-cTnC interactions. Measurements were done using reconstituted thin filaments, which contained the pseudo-phosphorylated cTnI(S151E). We hypothesized that the thin filament regulation is modulated by altered cTnC-cTnI interactions due to charge modification caused by the phosphorylation of Ser151 in cTnI. Our results showed that the pseudo-phosphorylation of cTnI (S151E) sensitizes structural changes to Ca(2+) by shortening the intersite distances between cTnC and cTnI. Furthermore, kinetic rates of Ca(2+) dissociation-induced structural change in the regulatory region of cTnI were reduced significantly by cTnI (S151E). The aforementioned effects of pseudo-phosphorylation of cTnI were similar to those of strong crossbridges on structural changes in cTnI. Our results provide novel information on how cardiac thin filament regulation is modulated by PAK3 phosphorylation of cTnI.
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Affiliation(s)
- Yexin Ouyang
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA
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30
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Ke Y, Sheehan KA, Egom EEA, Lei M, Solaro RJ. Novel bradykinin signaling in adult rat cardiac myocytes through activation of p21-activated kinase. Am J Physiol Heart Circ Physiol 2010; 298:H1283-9. [PMID: 20154261 PMCID: PMC2853422 DOI: 10.1152/ajpheart.01070.2009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Although bradykinin (BK) is known to exert effects on the myocardium, its intracellular signaling pathways remain poorly understood. Experiments in other cell types indicated that p21-activated kinase-1 (Pak1), a Ser/Thr kinase downstream of small monomeric G proteins, is activated by BK. We previously reported that the expression of active Pak1 in adult cardiac myocytes induced activation of protein phosphatase 2A and dephosphorylation of myofilament proteins (Ke et al. Circ Res 94: 194–200, 2004). In experiments reported here, we tested the hypothesis that BK signals altered protein phosphorylation in adult rat cardiac myocytes through the activation and translocation of Pak1. Treatment of myocytes with BK resulted in the activation of Pak1 as demonstrated by increased autophosphorylation at Thr423 and a diminished striated localization, which is present in the basal state. BK induced dephosphorylation of both cardiac troponin I and phospholamban. Treatment of isolated myocytes with BK also blunted the effect of isoproterenol to enhance peak Ca2+ and relaxation of Ca2+ transients. Protein phosphatase 2A was demonstrated to associate with both Pak 1 and phospholamban. Our studies indicate a novel signaling mechanism for BK in adult rat cardiac myocytes and support our hypothesis that Pak 1 is a significant regulator of phosphatase activity in the heart.
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Affiliation(s)
- Yunbo Ke
- Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, USA
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31
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Silberman GA, Fan THM, Liu H, Jiao Z, Xiao HD, Lovelock JD, Boulden BM, Widder J, Fredd S, Bernstein KE, Wolska BM, Dikalov S, Harrison DG, Dudley SC. Uncoupled cardiac nitric oxide synthase mediates diastolic dysfunction. Circulation 2010; 121:519-28. [PMID: 20083682 PMCID: PMC2819317 DOI: 10.1161/circulationaha.109.883777] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
BACKGROUND Heart failure with preserved ejection fraction is 1 consequence of hypertension and is caused by impaired cardiac diastolic relaxation. Nitric oxide (NO) is a known modulator of cardiac relaxation. Hypertension can lead to a reduction in vascular NO, in part because NO synthase (NOS) becomes uncoupled when oxidative depletion of its cofactor tetrahydrobiopterin (BH(4)) occurs. Similar events may occur in the heart that lead to uncoupled NOS and diastolic dysfunction. METHODS AND RESULTS In a hypertensive mouse model, diastolic dysfunction was accompanied by cardiac oxidation, a reduction in cardiac BH(4), and uncoupled NOS. Compared with sham-operated animals, male mice with unilateral nephrectomy, with subcutaneous implantation of a controlled-release deoxycorticosterone acetate pellet, and given 1% saline to drink were mildly hypertensive and had diastolic dysfunction in the absence of systolic dysfunction or cardiac hypertrophy. The hypertensive mouse hearts showed increased oxidized biopterins, NOS-dependent superoxide production, reduced NO production, and dephosphorylated phospholamban. Feeding hypertensive mice BH(4) (5 mg/d), but not treating with hydralazine or tetrahydroneopterin, improved cardiac BH(4) stores, phosphorylated phospholamban levels, and diastolic dysfunction. Isolated cardiomyocyte experiments revealed impaired relaxation that was normalized with short-term BH(4) treatment. Targeted cardiac overexpression of angiotensin-converting enzyme also resulted in cardiac oxidation, NOS uncoupling, and diastolic dysfunction in the absence of hypertension. CONCLUSIONS Cardiac oxidation, independently of vascular changes, can lead to uncoupled cardiac NOS and diastolic dysfunction. BH(4) may represent a possible treatment for diastolic dysfunction.
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Affiliation(s)
- Gad A. Silberman
- Department of Medicine (Division of Cardiology), Emory University School of Medicine, Atlanta, GA
| | - Tai-Hwang M. Fan
- Department of Medicine (Division of Cardiology), Emory University School of Medicine, Atlanta, GA
- Atlanta VA Medical Center, Atlanta, GA
| | - Hong Liu
- Department of Medicine (Division of Cardiology), Emory University School of Medicine, Atlanta, GA
- Section of Cardiology, University of Illinois at Chicago, Chicago, IL and the Jesse Brown VA Medical Center, Chicago IL
| | - Zhe Jiao
- Department of Medicine (Division of Cardiology), Emory University School of Medicine, Atlanta, GA
- Section of Cardiology, University of Illinois at Chicago, Chicago, IL and the Jesse Brown VA Medical Center, Chicago IL
| | - Hong D. Xiao
- Department of Pathology, Massachusetts General Hospital, Boston, MA
| | - Joshua D. Lovelock
- Section of Cardiology, University of Illinois at Chicago, Chicago, IL and the Jesse Brown VA Medical Center, Chicago IL
| | - Beth M. Boulden
- Department of Medicine (Division of Cardiology), Emory University School of Medicine, Atlanta, GA
| | - Julian Widder
- Department of Medicine (Division of Cardiology), Emory University School of Medicine, Atlanta, GA
| | - Scott Fredd
- Department of Medicine (Division of Cardiology), Emory University School of Medicine, Atlanta, GA
| | | | - Beata M. Wolska
- Section of Cardiology, University of Illinois at Chicago, Chicago, IL and the Jesse Brown VA Medical Center, Chicago IL
| | - Sergey Dikalov
- Department of Medicine (Division of Cardiology), Emory University School of Medicine, Atlanta, GA
| | - David G. Harrison
- Department of Medicine (Division of Cardiology), Emory University School of Medicine, Atlanta, GA
- Atlanta VA Medical Center, Atlanta, GA
| | - Samuel C. Dudley
- Department of Medicine (Division of Cardiology), Emory University School of Medicine, Atlanta, GA
- Atlanta VA Medical Center, Atlanta, GA
- Section of Cardiology, University of Illinois at Chicago, Chicago, IL and the Jesse Brown VA Medical Center, Chicago IL
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33
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Ke Y, Lei M, Solaro RJ. Regulation of cardiac excitation and contraction by p21 activated kinase-1. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2009; 98:238-50. [PMID: 19351515 DOI: 10.1016/j.pbiomolbio.2009.01.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cardiac excitation and contraction are regulated by a variety of signaling molecules. Central to the regulatory scheme are protein kinases and phosphatases that carry out reversible phosphorylation of different effectors. The process of beta-adrenergic stimulation mediated by cAMP dependent protein kinase (PKA) forms a well-known pathway considered as the most significant control mechanism in excitation and contraction as well as many other regulatory mechanisms in cardiac function. However, although dephosphorylation pathways are critical to these regulatory processes, signaling to phosphatases is relatively poorly understood. Emerging evidence indicates that regulation of phosphatases, which dampen the effect of beta-adrenergic stimulation, is also important. We review here functional studies of p21 activated kinase-1 (Pak1) and its potential role as an upstream signal for protein phosphatase PP2A in the heart. Pak1 is a serine/threonine protein kinase directly activated by the small GTPases Cdc42 and Rac1. Pak1 is highly expressed in different regions of the heart and modulates the activities of ion channels, sarcomeric proteins, and other phosphoproteins through up-regulation of PP2A activity. Coordination of Pak1 and PP2A activities is not only potentially involved in regulation of normal cardiac function, but is likely to be important in patho-physiological conditions.
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Affiliation(s)
- Yunbo Ke
- The Department of Physiology and Biophysics and Center for Cardiovascular Research, University of Illinois at Chicago, College of Medicine, Room 202, COMRB, 835 South Wolcott Avenue, Chicago, IL 60612, USA
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