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Jones TLM, Woulfe KC. Considering impact of age and sex on cardiac cytoskeletal components. Am J Physiol Heart Circ Physiol 2024; 326:H470-H478. [PMID: 38133622 PMCID: PMC11219061 DOI: 10.1152/ajpheart.00619.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 12/08/2023] [Accepted: 12/21/2023] [Indexed: 12/23/2023]
Abstract
The cardiac cytoskeletal components are integral to cardiomyocyte function and are responsible for contraction, sustaining cell structure, and providing scaffolding to direct signaling. Cytoskeletal components have been implicated in cardiac pathology; however, less attention has been paid to age-related modifications of cardiac cytoskeletal components and how these contribute to dysfunction with increased age. Moreover, significant sex differences in cardiac aging have been identified, but we still lack a complete understanding to the mechanisms behind these differences. This review summarizes what is known about how key cardiomyocyte cytoskeletal components are modified because of age, as well as reported sex-specific differences. Thorough consideration of both age and sex as integral players in cytoskeletal function may reveal potential avenues for more personalized therapeutics.
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Affiliation(s)
- Timothy L M Jones
- Division of Cardiology, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States
| | - Kathleen C Woulfe
- Division of Cardiology, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States
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2
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Simulation Study of Radio Frequency Safety and the Optimal Size of a Single-Channel Surface Radio Frequency Coil for Mice at 9.4 T Magnetic Resonance Imaging. SENSORS 2022; 22:s22114274. [PMID: 35684895 PMCID: PMC9185248 DOI: 10.3390/s22114274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 05/22/2022] [Accepted: 06/01/2022] [Indexed: 12/04/2022]
Abstract
The optimized size of a single-channel surface radio frequency (RF) coil for mouse body images in a 9.4 T magnetic resonance imaging (MRI) system was determined via electromagnetic-field analysis of the signal depth according to the size of a single-channel coil. The single-channel surface RF coils used in electromagnetic field simulations were configured to operate in transmission/reception mode at a frequency of 9.4 T–400 MHz. Computational analysis using the finite-difference time-domain method was used to assess the single-channel surface RF coil by comparing single-channel surface RF coils of varying sizes in terms of |B1|-, |B1+|-, |B1−|- and |E|-field distribution. RF safety for the prevention of burn injuries to small animals was assessed using an analysis of the specific absorption rate. A single-channel surface RF coil with a 20 mm diameter provided optimal B1-field distribution and RF safety, thus confirming that single-channel surface RF coils with ≥25 mm diameter could not provide typical B1-field distribution. A single-channel surface RF coil with a 20 mm diameter for mouse body imaging at 9.4 T MRI was recommended to preserve the characteristics of single-channel surface RF coils, and ensured that RF signals were applied correctly to the target point within RF safety guidelines.
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3
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Gömöri K, Herwig M, Budde H, Hassoun R, Mostafi N, Zhazykbayeva S, Sieme M, Modi S, Szabados T, Pipis J, Farkas-Morvay N, Leprán I, Ágoston G, Baczkó I, Kovács Á, Mügge A, Ferdinandy P, Görbe A, Bencsik P, Hamdani N. Ca2+/calmodulin-dependent protein kinase II and protein kinase G oxidation contributes to impaired sarcomeric proteins in hypertrophy model. ESC Heart Fail 2022; 9:2585-2600. [PMID: 35584900 PMCID: PMC9288768 DOI: 10.1002/ehf2.13973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 04/20/2022] [Accepted: 05/04/2022] [Indexed: 11/24/2022] Open
Abstract
Aims Volume overload (VO) induced hypertrophy is one of the hallmarks to the development of heart diseases. Understanding the compensatory mechanisms involved in this process might help preventing the disease progression. Methods and results Therefore, the present study used 2 months old Wistar rats, which underwent an aortocaval fistula to develop VO‐induced hypertrophy. The animals were subdivided into four different groups, two sham operated animals served as age‐matched controls and two groups with aortocaval fistula. Echocardiography was performed prior termination after 4‐ and 8‐month. Functional and molecular changes of several sarcomeric proteins and their signalling pathways involved in the regulation and modulation of cardiomyocyte function were investigated. Results The model was characterized with preserved ejection fraction in all groups and with elevated heart/body weight ratio, left/right ventricular and atrial weight at 4‐ and 8‐month, which indicates VO‐induced hypertrophy. In addition, 8‐months groups showed increased left ventricular internal diameter during diastole, RV internal diameter, stroke volume and velocity‐time index compared with their age‐matched controls. These changes were accompanied by increased Ca2+ sensitivity and titin‐based cardiomyocyte stiffness in 8‐month VO rats compared with other groups. The altered cardiomyocyte mechanics was associated with phosphorylation deficit of sarcomeric proteins cardiac troponin I, myosin binding protein C and titin, also accompanied with impaired signalling pathways involved in phosphorylation of these sarcomeric proteins in 8‐month VO rats compared with age‐matched control group. Impaired protein phosphorylation status and dysregulated signalling pathways were associated with significant alterations in the oxidative status of both kinases CaMKII and PKG explaining by this the elevated Ca2+ sensitivity and titin‐based cardiomyocyte stiffness and perhaps the development of hypertrophy. Conclusions Our findings showed VO‐induced cardiomyocyte dysfunction via deranged phosphorylation of myofilament proteins and signalling pathways due to increased oxidative state of CaMKII and PKG and this might contribute to the development of hypertrophy.
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Affiliation(s)
- Kamilla Gömöri
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary.,Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany.,Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Melissa Herwig
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany.,Department of Cardiology, St. Josef-Hospital, Ruhr University Bochum, Bochum, Germany
| | - Heidi Budde
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany.,Department of Cardiology, St. Josef-Hospital, Ruhr University Bochum, Bochum, Germany
| | - Roua Hassoun
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany.,Department of Cardiology, St. Josef-Hospital, Ruhr University Bochum, Bochum, Germany
| | - Nusratul Mostafi
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany.,Department of Cardiology, St. Josef-Hospital, Ruhr University Bochum, Bochum, Germany
| | - Saltanat Zhazykbayeva
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany.,Department of Cardiology, St. Josef-Hospital, Ruhr University Bochum, Bochum, Germany
| | - Marcel Sieme
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany.,Department of Cardiology, St. Josef-Hospital, Ruhr University Bochum, Bochum, Germany
| | - Suvasini Modi
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany.,Department of Cardiology, St. Josef-Hospital, Ruhr University Bochum, Bochum, Germany
| | - Tamara Szabados
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary.,Pharmahungary Group, Szeged, Hungary
| | - Judit Pipis
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary.,Pharmahungary Group, Szeged, Hungary
| | | | - István Leprán
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Gergely Ágoston
- Institute of Family Medicine, University of Szeged, Szeged, Hungary
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Árpád Kovács
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany.,Department of Cardiology, St. Josef-Hospital, Ruhr University Bochum, Bochum, Germany
| | - Andreas Mügge
- Department of Cardiology, St. Josef-Hospital, Ruhr University Bochum, Bochum, Germany
| | - Péter Ferdinandy
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary.,Pharmahungary Group, Szeged, Hungary
| | - Anikó Görbe
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary.,Pharmahungary Group, Szeged, Hungary
| | - Péter Bencsik
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary.,Pharmahungary Group, Szeged, Hungary
| | - Nazha Hamdani
- Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany.,Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary.,Department of Cardiology, St. Josef-Hospital, Ruhr University Bochum, Bochum, Germany.,HCEMM-Cardiovascular Research Group, Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
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4
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Qvit N, Lin AJ, Elezaby A, Ostberg NP, Campos JC, Ferreira JCB, Mochly-Rosen D. A Selective Inhibitor of Cardiac Troponin I Phosphorylation by Delta Protein Kinase C (δPKC) as a Treatment for Ischemia-Reperfusion Injury. Pharmaceuticals (Basel) 2022; 15:271. [PMID: 35337069 PMCID: PMC8950820 DOI: 10.3390/ph15030271] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/15/2022] [Accepted: 02/17/2022] [Indexed: 01/27/2023] Open
Abstract
Myocardial infarction is the leading cause of cardiovascular mortality, with myocardial injury occurring during ischemia and subsequent reperfusion (IR). We previously showed that the inhibition of protein kinase C delta (δPKC) with a pan-inhibitor (δV1-1) mitigates myocardial injury and improves mitochondrial function in animal models of IR, and in humans with acute myocardial infarction, when treated at the time of opening of the occluded blood vessel, at reperfusion. Cardiac troponin I (cTnI), a key sarcomeric protein in cardiomyocyte contraction, is phosphorylated by δPKC during reperfusion. Here, we describe a rationally-designed, selective, high-affinity, eight amino acid peptide that inhibits cTnI's interaction with, and phosphorylation by, δPKC (ψTnI), and prevents tissue injury in a Langendorff model of myocardial infarction, ex vivo. Unexpectedly, we also found that this treatment attenuates IR-induced mitochondrial dysfunction. These data suggest that δPKC phosphorylation of cTnI is critical in IR injury, and that a cTnI/δPKC interaction inhibitor should be considered as a therapeutic target to reduce cardiac injury after myocardial infarction.
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Affiliation(s)
- Nir Qvit
- Center for Clinical Sciences Research, Department of Chemical & Systems Biology, Stanford University School of Medicine, 269 Campus Dr. Room 3145, Stanford, CA 94305, USA; (N.Q.); (A.J.L.); (A.E.); (N.P.O.); (J.C.B.F.)
- The Azrieli Faculty of Medicine in the Galilee, Bar-Ilan University, Safed 1311502, Israel
| | - Amanda J. Lin
- Center for Clinical Sciences Research, Department of Chemical & Systems Biology, Stanford University School of Medicine, 269 Campus Dr. Room 3145, Stanford, CA 94305, USA; (N.Q.); (A.J.L.); (A.E.); (N.P.O.); (J.C.B.F.)
| | - Aly Elezaby
- Center for Clinical Sciences Research, Department of Chemical & Systems Biology, Stanford University School of Medicine, 269 Campus Dr. Room 3145, Stanford, CA 94305, USA; (N.Q.); (A.J.L.); (A.E.); (N.P.O.); (J.C.B.F.)
| | - Nicolai P. Ostberg
- Center for Clinical Sciences Research, Department of Chemical & Systems Biology, Stanford University School of Medicine, 269 Campus Dr. Room 3145, Stanford, CA 94305, USA; (N.Q.); (A.J.L.); (A.E.); (N.P.O.); (J.C.B.F.)
| | - Juliane C. Campos
- Department of Anatomy, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-000, Brazil;
| | - Julio C. B. Ferreira
- Center for Clinical Sciences Research, Department of Chemical & Systems Biology, Stanford University School of Medicine, 269 Campus Dr. Room 3145, Stanford, CA 94305, USA; (N.Q.); (A.J.L.); (A.E.); (N.P.O.); (J.C.B.F.)
- Department of Anatomy, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-000, Brazil;
| | - Daria Mochly-Rosen
- Center for Clinical Sciences Research, Department of Chemical & Systems Biology, Stanford University School of Medicine, 269 Campus Dr. Room 3145, Stanford, CA 94305, USA; (N.Q.); (A.J.L.); (A.E.); (N.P.O.); (J.C.B.F.)
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5
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Li X, Zheng S, Tan W, Chen H, Li X, Wu J, Luo T, Ren X, Pyle WG, Wang L, Backx PH, Huang R, Yang FH. Slit2 Protects Hearts Against Ischemia-Reperfusion Injury by Inhibiting Inflammatory Responses and Maintaining Myofilament Contractile Properties. Front Physiol 2020; 11:228. [PMID: 32292352 PMCID: PMC7135862 DOI: 10.3389/fphys.2020.00228] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 02/27/2020] [Indexed: 12/12/2022] Open
Abstract
Background The secreted glycoprotein Slit2, previously known as an axon guidance cue, has recently been found to protect tissues in pathological conditions; however, it is unknown whether Slit2 functions in cardiac ischemia-reperfusion (IR) injury. Methods Langendorff-perfused isolated hearts from Slit2-overexpressing (Slit2-Tg) mice and C57BL/6J mice (background strain) were subjected to 20 min of global ischemia followed by 40 min of reperfusion. We compared Slit2-Tg with C57BL/6J mice in terms of left ventricular function and infarct size of post-IR hearts along with tissue histological and biochemical assessments (mRNA and protein expression, phosphorylation status, and myofilament contractile properties). Results Slit2 played cardioprotective roles in maintaining contractile function and reducing infarct size in post-IR hearts. IR increased the expression of the Slit2 receptor Robo4 and the membrane receptor Slamf7, but these increases were suppressed by Slit2 overexpression post IR. This suppression was associated with inhibition of the nuclear translocation of NFκB p65 and reductions in IL-1β and IL-18 release into perfusates. Furthermore, Slit2 overexpression attenuated the increases in myofilament-associated PKCs and phosphorylation of cTnI at Ser43 in the post-IR myocardium. The myofilament calcium sensitivity and actomyosin MgATPase activity were preserved in the post-IR Slit2 myocardium. Conclusion Our work demonstrates that Slit2 inhibits inflammatory responses and maintains myofilament contractile properties, thus contributing, at least in part, to the prevention of structural and functional damage during IR.
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Affiliation(s)
- Xiang Li
- Guangdong Province Key Laboratory of Laboratory Animals, Cardiovascular Model Research Center, Guangdong Laboratory Animals Monitoring Institute, Guangzhou, China
| | - Shuang Zheng
- Guangdong Province Key Laboratory of Laboratory Animals, Cardiovascular Model Research Center, Guangdong Laboratory Animals Monitoring Institute, Guangzhou, China.,School of Basic Medicine, Vascular Biology Institute, Guangdong Pharmaceutical University, Guanghzou, China
| | - Weijiang Tan
- Guangdong Province Key Laboratory of Laboratory Animals, Cardiovascular Model Research Center, Guangdong Laboratory Animals Monitoring Institute, Guangzhou, China
| | - Hongqi Chen
- Guangdong Province Key Laboratory of Laboratory Animals, Cardiovascular Model Research Center, Guangdong Laboratory Animals Monitoring Institute, Guangzhou, China
| | - Xiaohui Li
- Department of Cardiovascular Surgery, The First Affiliated Hospital, Jinan University, Guangzhou, China
| | - Jian Wu
- Shanghai Institute of Cardiovascular Diseases, Zhongshan Hospital and Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Ting Luo
- Guangdong Province Key Laboratory of Laboratory Animals, Cardiovascular Model Research Center, Guangdong Laboratory Animals Monitoring Institute, Guangzhou, China
| | - Xuecong Ren
- Guangdong Province Key Laboratory of Laboratory Animals, Cardiovascular Model Research Center, Guangdong Laboratory Animals Monitoring Institute, Guangzhou, China
| | - W Glen Pyle
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Lijing Wang
- School of Basic Medicine, Vascular Biology Institute, Guangdong Pharmaceutical University, Guanghzou, China
| | - Peter H Backx
- Department of Biology, York University, Toronto, ON, Canada.,Division of Cardiology and the Peter Munk Cardiac Centre, University Health Network, Toronto, ON, Canada
| | - Ren Huang
- Guangdong Province Key Laboratory of Laboratory Animals, Cardiovascular Model Research Center, Guangdong Laboratory Animals Monitoring Institute, Guangzhou, China
| | - Feng Hua Yang
- Guangdong Province Key Laboratory of Laboratory Animals, Cardiovascular Model Research Center, Guangdong Laboratory Animals Monitoring Institute, Guangzhou, China.,Department of Cardiovascular Surgery, The First Affiliated Hospital, Jinan University, Guangzhou, China
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6
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Scruggs SB, Wang D, Ping P. PRKCE gene encoding protein kinase C-epsilon-Dual roles at sarcomeres and mitochondria in cardiomyocytes. Gene 2016; 590:90-6. [PMID: 27312950 DOI: 10.1016/j.gene.2016.06.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 05/23/2016] [Accepted: 06/05/2016] [Indexed: 12/26/2022]
Abstract
Protein kinase C-epsilon (PKCε) is an isoform of a large PKC family of enzymes that has a variety of functions in different cell types. Here we discuss two major roles of PKCε in cardiac muscle cells; specifically, its role in regulating cardiac muscle contraction via targeting the sarcomeric proteins, as well as modulating cardiac cell energy production and metabolism by targeting cardiac mitochondria. The importance of PKCε action is described within the context of intracellular localization, as substrate selectivity and specificity is achieved through spatiotemporal targeting of PKCε. Accordingly, the role of PKCε in regulating myocardial function in physiological and pathological states has been documented in both cardioprotection and cardiac hypertrophy.
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Affiliation(s)
- Sarah B Scruggs
- Departments of Physiology, Medicine (Cardiology) and Bioinformatics, NIH BD2K Center of Excellence for Biomedical Computing, University of California Los Angeles, Los Angeles, CA 90095, USA.
| | - Ding Wang
- Departments of Physiology, Medicine (Cardiology) and Bioinformatics, NIH BD2K Center of Excellence for Biomedical Computing, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Peipei Ping
- Departments of Physiology, Medicine (Cardiology) and Bioinformatics, NIH BD2K Center of Excellence for Biomedical Computing, University of California Los Angeles, Los Angeles, CA 90095, USA.
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7
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Khodabukus A, Baehr LM, Bodine SC, Baar K. Role of contraction duration in inducing fast-to-slow contractile and metabolic protein and functional changes in engineered muscle. J Cell Physiol 2015; 230:2489-97. [PMID: 25857846 DOI: 10.1002/jcp.24985] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 03/04/2015] [Indexed: 12/26/2022]
Abstract
The role of factors such as frequency, contraction duration and active time in the adaptation to chronic low-frequency electrical stimulation (CLFS) is widely disputed. In this study we explore the ability of contraction duration (0.6, 6, 60, and 600 sec) to induce a fast-to-slow shift in engineered muscle while using a stimulation frequency of 10 Hz and keeping active time constant at 60%. We found that all contraction durations induced similar slowing of time-to-peak tension. Despite similar increases in total myosin heavy (MHC) levels with stimulation, increasing contraction duration resulted in progressive decreases in total fast myosin. With contraction durations of 60 and 600 sec, MHC IIx levels decreased and MHC IIa levels increased. All contraction durations resulted in fast-to-slow shifts in TnT and TnC but increased both fast and slow TnI levels. Half-relaxation slowed to a greater extent with contraction durations of 60 and 600 sec despite similar changes in the calcium sequestering proteins calsequestrin and parvalbumin and the calcium uptake protein SERCA. All CLFS groups resulted in greater fatigue resistance than control. Similar increases in GLUT4, mitochondrial enzymes (SDH and ATPsynthase), the fatty acid transporter CPT-1, and the metabolic regulators PGC-1α and MEF2 were found with all contraction durations. However, the mitochondrial enzymes cytochrome C and citrate synthase were increased to greater levels with contraction durations of 60 and 600 sec. These results demonstrate that contraction duration plays a pivotal role in dictating the level of CLFS-induced contractile and metabolic adaptations in tissue-engineered skeletal muscle.
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Affiliation(s)
- Alastair Khodabukus
- Division of Neurobiology, Physiology and Behavior, University of California Davis, Davis, California
| | - Leslie M Baehr
- Division of Neurobiology, Physiology and Behavior, University of California Davis, Davis, California
| | - Sue C Bodine
- Division of Neurobiology, Physiology and Behavior, University of California Davis, Davis, California
| | - Keith Baar
- Division of Neurobiology, Physiology and Behavior, University of California Davis, Davis, California
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8
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Tarigopula M, Davis RT, Mungai PT, Ryba DM, Wieczorek DF, Cowan CL, Violin JD, Wolska BM, Solaro RJ. Cardiac myosin light chain phosphorylation and inotropic effects of a biased ligand, TRV120023, in a dilated cardiomyopathy model. Cardiovasc Res 2015; 107:226-34. [PMID: 26045475 DOI: 10.1093/cvr/cvv162] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 05/17/2015] [Indexed: 01/06/2023] Open
Abstract
AIMS Therapeutic approaches to treat familial dilated cardiomyopathy (DCM), which is characterized by depressed sarcomeric tension and susceptibility to Ca(2+)-related arrhythmias, have been generally unsuccessful. Our objective in the present work was to determine the effect of the angiotensin II type 1 receptor (AT1R) biased ligand, TRV120023, on contractility of hearts of a transgenic mouse model of familial DCM with mutation in tropomyosin at position 54 (TG-E54K). Our rationale is based on previous studies, which have supported the hypothesis that biased G-protein-coupled receptor ligands, signalling via β-arrestin, increase cardiac contractility with no effect on Ca(2+) transients. Our previous work demonstrated that the biased ligand TRV120023 is able to block angiotensin-induced hypertrophy, while promoting an increase in sarcomere Ca(2+) response. METHODS AND RESULTS We tested the hypothesis that the depression in cardiac function associated with DCM can be offset by infusion of the AT1R biased ligand, TRV120023. We intravenously infused saline, TRV120023, or the unbiased ligand, losartan, for 15 min in TG-E54K and non-transgenic mice to obtain left ventricular pressure-volume relations. Hearts were analysed for sarcomeric protein phosphorylation. Results showed that the AT1R biased ligand increases cardiac performance in TG-E54K mice in association with increased myosin light chain-2 phosphorylation. CONCLUSION Treatment of mice with an AT1R biased ligand, acting via β-arrestin signalling, is able to induce an increase in cardiac contractility associated with an increase in ventricular myosin light chain-2 phosphorylation. AT1R biased ligands may prove to be a novel inotropic approach in familial DCM.
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Affiliation(s)
- Madhusudhan Tarigopula
- Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois, 835 S. Wolcott Avenue, Chicago, IL 60612-7342, USA
| | - Robert T Davis
- Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois, 835 S. Wolcott Avenue, Chicago, IL 60612-7342, USA
| | - Paul T Mungai
- Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois, 835 S. Wolcott Avenue, Chicago, IL 60612-7342, USA
| | - David M Ryba
- Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois, 835 S. Wolcott Avenue, Chicago, IL 60612-7342, USA
| | - David F Wieczorek
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati Medical Center, Cincinnati, OH, USA
| | | | | | - Beata M Wolska
- Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois, 835 S. Wolcott Avenue, Chicago, IL 60612-7342, USA Department of Medicine, Division of Cardiology, University of Illinois, Chicago, IL, USA
| | - R John Solaro
- Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois, 835 S. Wolcott Avenue, Chicago, IL 60612-7342, USA
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9
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Bondarenko VE. A compartmentalized mathematical model of the β1-adrenergic signaling system in mouse ventricular myocytes. PLoS One 2014; 9:e89113. [PMID: 24586529 PMCID: PMC3931689 DOI: 10.1371/journal.pone.0089113] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Accepted: 01/14/2014] [Indexed: 01/08/2023] Open
Abstract
The β1-adrenergic signaling system plays an important role in the functioning of cardiac cells. Experimental data shows that the activation of this system produces inotropy, lusitropy, and chronotropy in the heart, such as increased magnitude and relaxation rates of [Ca2+]i transients and contraction force, and increased heart rhythm. However, excessive stimulation of β1-adrenergic receptors leads to heart dysfunction and heart failure. In this paper, a comprehensive, experimentally based mathematical model of the β1-adrenergic signaling system for mouse ventricular myocytes is developed, which includes major subcellular functional compartments (caveolae, extracaveolae, and cytosol). The model describes biochemical reactions that occur during stimulation of β1-adrenoceptors, changes in ionic currents, and modifications of Ca2+ handling system. Simulations describe the dynamics of major signaling molecules, such as cyclic AMP and protein kinase A, in different subcellular compartments; the effects of inhibition of phosphodiesterases on cAMP production; kinetics and magnitudes of phosphorylation of ion channels, transporters, and Ca2+ handling proteins; modifications of action potential shape and duration; magnitudes and relaxation rates of [Ca2+]i transients; changes in intracellular and transmembrane Ca2+ fluxes; and [Na+]i fluxes and dynamics. The model elucidates complex interactions of ionic currents upon activation of β1-adrenoceptors at different stimulation frequencies, which ultimately lead to a relatively modest increase in action potential duration and significant increase in [Ca2+]i transients. In particular, the model includes two subpopulations of the L-type Ca2+ channels, in caveolae and extracaveolae compartments, and their effects on the action potential and [Ca2+]i transients are investigated. The presented model can be used by researchers for the interpretation of experimental data and for the developments of mathematical models for other species or for pathological conditions.
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Affiliation(s)
- Vladimir E. Bondarenko
- Department of Mathematics and Statistics and Neuroscience Institute, Georgia State University, Atlanta, Georgia, United States of America
- * E-mail:
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10
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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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11
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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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12
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Gaikis L, Stewart D, Johnson R, Pyle WG. Identifying a role of the actin capping protein CapZ in β-adrenergic receptor signalling. Acta Physiol (Oxf) 2013; 207:173-82. [PMID: 22882973 DOI: 10.1111/j.1748-1716.2012.02470.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 12/08/2011] [Accepted: 06/25/2012] [Indexed: 11/30/2022]
Abstract
AIM β-Adrenergic receptor activation increases myocardial contractility, in part through protein kinase A (PKA)-dependent modification of cardiac myofilaments. PKA regulation of cardiac myofilaments is contingent influenced by protein kinase C (PKC) phosphorylation of troponin I (TnI). Reductions in the cardiac Z-disc protein CapZ attenuate PKC regulation of myofilament activation. We hypothesized that CapZ-deficient transgenic mouse hearts respond poorly to β-adrenergic receptor activation, as a result of impaired PKC activation. METHODS Wild-type and CapZ-deficient transgenic mice were treated with the β-adrenergic receptor agonist isoproterenol (ISO) and whole heart function assessed by echocardiography. Cardiac myofilaments were isolated post-ISO treatment and subjected to an actomyosin MgATPase assay and protein phosphorylation gels. RESULTS CapZ-deficient transgenic mouse hearts exhibited increased contractility and myofilament calcium sensitivity at baseline, as compared to wild-type mice. In wild-type mice, ISO increased myocardial contractility and decreased myofilament calcium sensitivity, along with an increase in TnI phosphorylation. CapZ-deficient transgenic mice responded to ISO treatment, and myocardial functional differences between transgenic and wild-type mice were abolished. ISO-dependent changes in myofilament activation in transgenic mice were similar to those observed in wild-type. TnI phosphorylation was similarly increased in wild-type and transgenic mice following ISO treatment, while CapZ-deficient transgenic mouse myofilaments also exhibited increased myosin-binding protein C phosphorylation. Differences in myofilament protein phosphorylation patterns suggest the intracellular mechanisms utilized by β-adrenergic receptor activation are different than that seen in wild-type hearts. CONCLUSIONS These data further support the concept that the cardiac Z-disc protein is a regulator of myofilament function and intracellular signalling transduction.
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Affiliation(s)
- L. Gaikis
- Cardiovascular Research Group; Department of Biomedical Sciences; Ontario Veterinary College; University of Guelph; Guelph; ON; Canada
| | - D. Stewart
- Cardiovascular Research Group; Department of Biomedical Sciences; Ontario Veterinary College; University of Guelph; Guelph; ON; Canada
| | - R. Johnson
- Cardiovascular Research Group; Department of Biomedical Sciences; Ontario Veterinary College; University of Guelph; Guelph; ON; Canada
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13
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Dong X, Sumandea CA, Chen YC, Garcia-Cazarin ML, Zhang J, Balke CW, Sumandea MP, Ge Y. Augmented phosphorylation of cardiac troponin I in hypertensive heart failure. J Biol Chem 2011; 287:848-57. [PMID: 22052912 DOI: 10.1074/jbc.m111.293258] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
An altered cardiac myofilament response to activating Ca(2+) is a hallmark of human heart failure. Phosphorylation of cardiac troponin I (cTnI) is critical in modulating contractility and Ca(2+) sensitivity of cardiac muscle. cTnI can be phosphorylated by protein kinase A (PKA) at Ser(22/23) and protein kinase C (PKC) at Ser(22/23), Ser(42/44), and Thr(143). Whereas the functional significance of Ser(22/23) phosphorylation is well understood, the role of other cTnI phosphorylation sites in the regulation of cardiac contractility remains a topic of intense debate, in part, due to the lack of evidence of in vivo phosphorylation. In this study, we utilized top-down high resolution mass spectrometry (MS) combined with immunoaffinity chromatography to determine quantitatively the cTnI phosphorylation changes in spontaneously hypertensive rat (SHR) model of hypertensive heart disease and failure. Our data indicate that cTnI is hyperphosphorylated in the failing SHR myocardium compared with age-matched normotensive Wistar-Kyoto rats. The top-down electron capture dissociation MS unambiguously localized augmented phosphorylation sites to Ser(22/23) and Ser(42/44) in SHR. Enhanced Ser(22/23) phosphorylation was verified by immunoblotting with phospho-specific antibodies. Immunoblot analysis also revealed up-regulation of PKC-α and -δ, decreased PKCε, but no changes in PKA or PKC-β levels in the SHR myocardium. This provides direct evidence of in vivo phosphorylation of cTnI-Ser(42/44) (PKC-specific) sites in an animal model of hypertensive heart failure, supporting the hypothesis that PKC phosphorylation of cTnI may be maladaptive and potentially associated with cardiac dysfunction.
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Affiliation(s)
- Xintong Dong
- Human Proteomics Program, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706, USA
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14
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Belin RJ, Sumandea MP, Sievert GA, Harvey LA, Geenen DL, Solaro RJ, de Tombe PP. Interventricular differences in myofilament function in experimental congestive heart failure. Pflugers Arch 2011; 462:795-809. [PMID: 21927813 DOI: 10.1007/s00424-011-1024-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 08/23/2011] [Accepted: 08/29/2011] [Indexed: 10/17/2022]
Abstract
This study was conducted to identify molecular mechanisms which explain interventricular differences in myofilament function in experimental congestive heart failure (CHF). CHF was induced in rats by chronic aortic banding or myocardial infarction for 32-36 weeks. Right and left ventricular (RV, LV) myocytes were mechanically isolated, triton-skinned, and attached to a force transducer and motor arm. Myofilament force-[Ca(2+)] relations assessed maximal Ca(2+)-saturated force (F (max)) and the [Ca(2+)] at 50% of F (max) (EC(50)). Myofilament protein phosphorylation was determined via ProQ diamond phospho-staining. Protein kinase C (PKC)-α expression/activation and site-specific phosphorylation of cardiac troponin I (cTnI) and cardiac troponin T (cTnT) were measured via immunoblotting. Relative to controls, failing RV myocytes displayed a ~45% decrease in F (max) with no change in EC(50), whereas failing LV myocytes displayed a ~45% decrease in F (max) and ~50% increase in EC(50). Failing LV myofilaments were less Ca(2+)-sensitive (37% increase in EC(50)) than failing RV myofilaments. Expression and activation of PKC-α was increased twofold in failing RV myocardium and relative to the RV, PKC-α was twofold higher in the failing LV, while PKC-β expression was unchanged by CHF. PKC-α-dependent phosphorylation and PP1-mediated dephosphorylation of failing RV myofilaments increased EC(50) and increased F (max), respectively. Phosphorylation of cTnI and cTnT was greater in failing LV myofilaments than in failing RV myofilaments. RV myofilament function is depressed in experimental CHF in association with increased PKC-α signaling and myofilament protein phosphorylation. Furthermore, myofilament dysfunction is greater in the LV compared to the RV due in part to increased PKC-α activation and phosphorylation of cTnI and cTnT.
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Affiliation(s)
- Rashad J Belin
- Department of Physiology & Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, IL, USA
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15
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Ambardekar AV, Walker JS, Walker LA, Cleveland JC, Lowes BD, Buttrick PM. Incomplete recovery of myocyte contractile function despite improvement of myocardial architecture with left ventricular assist device support. Circ Heart Fail 2011; 4:425-32. [PMID: 21540356 DOI: 10.1161/circheartfailure.111.961326] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Unloading a failing heart with a left ventricular assist device (LVAD) can improve ejection fraction (EF) and LV size; however, recovery with LVAD explantation is rare. We hypothesized that evaluation of myocyte contractility and biochemistry at the sarcomere level before and after LVAD may explain organ-level changes. METHODS AND RESULTS Paired LV tissue samples were frozen from 8 patients with nonischemic cardiomyopathy at LVAD implantation (before LVAD) and before cardiac transplantation (after LVAD). These were compared with 8 nonfailing hearts. Isolated skinned myocytes were purified and attached to a force transducer, and dimensions, maximum calcium-saturated force, calcium sensitivity, and myofilament cooperativity were assessed. Relative isoform abundance and phosphorylation levels of sarcomeric contractile proteins were measured. With LVAD support, the unloaded EF improved (10.0±1.0% to 25.6±11.0%, P=0.007), LV size decreased (LV internal dimension at end diastole, 7.6±1.2 to 4.9±1.4 cm; P<0.001), and myocyte dimensions decreased (cross-sectional area, 1247±346 to 638±254 μm(2); P=0.001). Maximum calcium-saturated force improved after LVAD (3.6±0.9 to 7.3±1.8 mN/mm(2), P<0.001) implantation but was still lower than in nonfailing hearts (7.3±1.8 versus 17.6±1.8 mN/mm(2), P<0.001). An increase in troponin I (TnI) phosphorylation after LVAD implantation was noted, but protein kinase C phosphorylation of TnI decreased. Biochemical changes of other sarcomeric proteins were not observed after LVAD. CONCLUSIONS There is significant improvement in LV and myocyte size with LVAD, but there is only partial recovery of EF and myocyte contractility. LVAD support was associated only with biochemical changes in TnI, suggesting that alternate mechanisms might contribute to contractile changes after LVAD and that additional interventions may be needed to alter biochemical remodeling of the sarcomere to further enhance myofilament and organ-level recovery.
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Affiliation(s)
- Amrut V Ambardekar
- Division of Cardiology, University of Colorado Denver, Aurora, CO 80045, USA.
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16
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Ramirez-Correa GA, Cortassa S, Stanley B, Gao WD, Murphy AM. Calcium sensitivity, force frequency relationship and cardiac troponin I: critical role of PKA and PKC phosphorylation sites. J Mol Cell Cardiol 2010; 48:943-53. [PMID: 20083117 PMCID: PMC2854165 DOI: 10.1016/j.yjmcc.2010.01.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Revised: 01/06/2010] [Accepted: 01/07/2010] [Indexed: 11/18/2022]
Abstract
Transgenic models with pseudo phosphorylation mutants of troponin I, PKA sites at Ser 22 and 23 (cTnIDD(22,23) mice) or PKC sites at Ser 42 and 44 (cTnIAD(22,23)DD(42,44)) displayed differential force-frequency relationships and afterload relaxation delay in vivo. We hypothesized that cTnI PKA and PKC phosphomimics impact cardiac muscle rate-related developed twitch force and relaxation kinetics in opposite directions. cTnIDD(22,23) transgenic mice produce a force frequency relationship (FFR) equivalent to control NTG albeit at lower peak [Ca(2+)](i), while cTnIAD(22,23)DD(42,44) TG mice had a flat FFR with normal peak systolic [Ca(2+)](i), thus suggestive of diminished responsiveness to [Ca(2+)](i) at higher frequencies. Force-[Ca(2+)](i) hysteresis analysis revealed that cTnIDD(22,23) mice have a combined enhanced myofilament calcium peak response with an enhanced slope of force development and decline per unit of [Ca(2+)](i), whereas cTnIAD(22,23)DD(42,44) transgenic mice showed the opposite. The computational ECME model predicts that the TG lines may be distinct from each other due to different rate constants for association/dissociation of Ca(2+) at the regulatory site of cTnC. Our data indicate that cTnI phosphorylation at PKA sites plays a critical role in the FFR by increasing relative myofilament responsiveness, and results in a distinctive transition between activation and relaxation, as displayed by force-[Ca(2+)](i) hysteresis loops. These findings may have important implications for understanding the specific contribution of cTnI to beta-adrenergic inotropy and lusitropy and to adverse contractile effects of PKC activation, which is relevant during heart failure development.
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Affiliation(s)
- Genaro A. Ramirez-Correa
- Department of Pediatrics/Division of Cardiology, Johns Hopkins University School of Medicine. Baltimore, MD
| | - Sonia Cortassa
- Department of Medicine/Division of Cardiology, Johns Hopkins University School of Medicine. Baltimore, MD
| | - Brian Stanley
- Department of Medicine/Division of Cardiology, Johns Hopkins University School of Medicine. Baltimore, MD
| | - Wei Dong Gao
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine. Baltimore, MD
| | - Anne M. Murphy
- Department of Pediatrics/Division of Cardiology, Johns Hopkins University School of Medicine. Baltimore, MD
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17
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Why does troponin I have so many phosphorylation sites? Fact and fancy. J Mol Cell Cardiol 2010; 48:810-6. [PMID: 20188739 DOI: 10.1016/j.yjmcc.2010.02.014] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 02/18/2010] [Accepted: 02/18/2010] [Indexed: 11/23/2022]
Abstract
We discuss a current controversy regarding the relative role of phosphorylation sites on cardiac troponin I (cTnI) (Fig. 1) in physiological and patho-physiological cardiac function. Studies with mouse models and in vitro studies indicate that multi-site phosphorylations are involved in both control of maximum tension and sarcomeric responsiveness to Ca(2+). Thus one hypothesis is that cardiac function reflects a balance of cTnI phosphorylations and a tilt in this balance may be maladaptive in acquired and genetic disorders of the heart. Studies on human heart samples taken mainly at end-stage heart failure, and in depth proteomic analysis of human and rat heart samples demonstrate that Ser23/Ser24 are the major and perhaps the only sites likely to be relevant to control cardiac function. Thus functional significance of Ser23/Ser24 phosphorylation is taken as fact, whereas the function of some other sites is treated as fancy. Maybe the extremes will meet: in any case we both agree that further work needs to be carried out with relatively large mammals and with determination of the time course of changes in phosphorylation to identify transient modifications that may be relevant at a beat-to-beat basis. Moreover, we agree that the changes and effects of cTnI phosphorylation need to be fully integrated into the effects of other phosphorylations in the cardiac myocyte.
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18
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Kirk JA, MacGowan GA, Evans C, Smith SH, Warren CM, Mamidi R, Chandra M, Stewart AFR, Solaro RJ, Shroff SG. Left ventricular and myocardial function in mice expressing constitutively pseudophosphorylated cardiac troponin I. Circ Res 2009; 105:1232-9. [PMID: 19850940 DOI: 10.1161/circresaha.109.205427] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Protein kinase (PK)C-induced phosphorylation of cardiac troponin (cTn)I has been shown to regulate cardiac contraction. OBJECTIVE Characterize functional effects of increased PKC-induced cTnI phosphorylation and identify underlying mechanisms using a transgenic mouse model (cTnI(PKC-P)) expressing mutant cTnI (S43E, S45E, T144E). METHODS AND RESULTS Two-dimensional gel analysis showed 7.2+/-0.5% replacement of endogenous cTnI with the mutant form. Experiments included: mechanical measurements (perfused isolated hearts, isolated papillary muscles, and skinned fiber preparations), biochemical and molecular biological measurements, and a mathematical model-based analysis for integrative interpretation. Compared to wild-type mice, cTnI(PKC-P) mice exhibited negative inotropy in isolated hearts (14% decrease in peak developed pressure), papillary muscles (53% decrease in maximum developed force), and skinned fibers (14% decrease in maximally activated force, F(max)). Additionally, cTnI(PKC-P) mice exhibited slowed relaxation in both isolated hearts and intact papillary muscles. The cTnI(PKC-P) mice showed no differences in calcium sensitivity, cooperativity, steady-state force-MgATPase relationship, calcium transient (amplitude and relaxation), or baseline phosphorylation of other myofilamental proteins. The model-based analysis revealed that experimental observations in cTnI(PKC-P) mice could be reproduced by 2 simultaneous perturbations: a decrease in the rate of cross-bridge formation and an increase in calcium-independent persistence of the myofilament active state. CONCLUSIONS A modest increase in PKC-induced cTnI phosphorylation ( approximately 7%) can significantly alter cardiac muscle contraction: negative inotropy via decreased cross-bridge formation and negative lusitropy via persistence of myofilament active state. Based on our data and data from the literature we speculate that effects of PKC-mediated cTnI phosphorylation are site-specific (S43/S45 versus T144).
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Affiliation(s)
- Jonathan A Kirk
- Cardiovascular Systems Laboratory, Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15219, USA
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19
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Walker LA, Walker JS, Ambler SK, Buttrick PM. Stage-specific changes in myofilament protein phosphorylation following myocardial infarction in mice. J Mol Cell Cardiol 2009; 48:1180-6. [PMID: 19799909 DOI: 10.1016/j.yjmcc.2009.09.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Accepted: 09/18/2009] [Indexed: 11/18/2022]
Abstract
The response of cardiac muscle to an insult such as myocardial infarction includes changes in the expression of numerous signaling proteins and modulation of gene expression, as well as post-translational modifications of existing proteins. Most studies to date have defined these in end-stage cardiac muscle thus obviating consideration of the temporal progression that causes the heart to transition from a compensated to a decompensated phenotype. To explore these transitions, we examined contractile protein biochemistry in a mouse MI model at two early time points: 2 days and 2 weeks post-infarct and at two later time points: 2 and 4 months post-infarct. Phosphorylation of myofilament proteins was analyzed using phosphospecific staining of polyacrylamide gels, and whenever possible, phosphospecific antibodies. Phosphorylation of myosin binding protein c, the myosin regulatory light chain and troponin I were all decreased relative to sham operated animals at both early time points. However, by 2 months, total phosphorylation of all the major myofilament proteins normalized and at both 2 and 4 months, there was a significant increase in troponin I phosphorylation. One-dimensional IEF of troponin I coupled with phospho-specific antibody analysis demonstrated a redistribution of phosphorylation sites with a significant initial decline at the putative PKA sites, Serine 22,23, and a subsequent increase at the putative PKC site, serine 43,45. These data suggest that temporal changes in myofilament protein phosphorylation contribute both to the initial compensatory hyperdynamic response to myocardial infarction and subsequently to the gradual progression to myocardial failure.
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Affiliation(s)
- Lori A Walker
- University of Colorado Health Sciences Center, Department of Medicine/Cardiology, Aurora, CO 80045, USA.
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20
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Adenosine triggers the nuclear translocation of protein kinase C epsilon in H9c2 cardiomyoblasts with the loss of phosphorylation at Ser729. J Cell Biochem 2009; 106:633-42. [DOI: 10.1002/jcb.22043] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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21
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Solaro RJ. Multiplex kinase signaling modifies cardiac function at the level of sarcomeric proteins. J Biol Chem 2008; 283:26829-33. [PMID: 18567577 DOI: 10.1074/jbc.r800037200] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- R John Solaro
- Department of Physiology and Biophysics and the Center for Cardiovascular Research, University of Illinois, Chicago, Illinois 60612, USA.
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22
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Lai ZF, Chen YZ, Feng LP, Meng XM, Ding JF, Wang LY, Ye J, Li P, Cheng XS, Kitamoto Y, Monzen K, Komuro I, Sakaguchi N, Kim-Mitsuyama S. Overexpression of TNNI3K, a cardiac-specific MAP kinase, promotes P19CL6-derived cardiac myogenesis and prevents myocardial infarction-induced injury. Am J Physiol Heart Circ Physiol 2008; 295:H708-16. [PMID: 18552163 DOI: 10.1152/ajpheart.00252.2008] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
TNNI3K is a new cardiac-specific MAP kinase whose gene is localized to 1p31.1 and that belongs to a tyrosine kinase-like branch in the kinase tree of the human genome. In the present study we investigated the role of TNNI3K in the cardiac myogenesis process and in the repair of ischemic injury. Pluripotent P19CL6 cells with or without transfection by pcDNA6-TNNI3K plasmid were used to induce differentiation into beating cardiomyocytes. TNNI3K promoted the differentiation process, judging from the increasing beating mass and increased number of alpha-actinin-positive cells. TNNI3K improved cardiac function by enhancing beating frequency and increasing the contractile force and epinephrine response of spontaneous action potentials without an increase of the single-cell size. TNNI3K suppressed phosphorylation of cardiac troponin I, annexin-V(+) cells, Bax protein, and p38/JNK-mediated apoptosis. Intramyocardial administration of TNNI3K-overexpressing P19CL6 cells in mice with myocardial infarction improved cardiac performance and attenuated ventricular remodeling compared with injection of wild-type P19CL6 cells. In conclusion, our study clearly indicates that TNNI3K promotes cardiomyogenesis, enhances cardiac performance, and protects the myocardium from ischemic injury by suppressing p38/JNK-mediated apoptosis. Therefore, modulation of TNNI3K activity would be a useful therapeutic approach for ischemic cardiac disease.
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Affiliation(s)
- Zhong-Fang Lai
- Dept. of Pharmacology and Molecular Therapeutics, Graduate School of Medical Sciences, Kumamoto Univ., Kumamoto 860-8556, Japan.
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23
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Kobayashi T, Jin L, de Tombe PP. Cardiac thin filament regulation. Pflugers Arch 2008; 457:37-46. [PMID: 18421471 DOI: 10.1007/s00424-008-0511-8] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2008] [Revised: 03/19/2008] [Accepted: 03/25/2008] [Indexed: 12/17/2022]
Abstract
Myocardial contraction is initiated upon the release of calcium into the cytosol from the sarcoplasmic reticulum following membrane depolarization. The fundamental physiological role of the heart is to pump an amount blood that is determined by the prevailing requirements of the body. The physiological control systems employed to accomplish this task include regulation of heart rate, the amount of calcium release, and the response of the cardiac myofilaments to activator calcium ions. Thin filament activation and relaxation dynamics has emerged as a pivotal regulatory system tuning myofilament function to the beat-to-beat regulation of cardiac output. Maladaptation of thin filament dynamics, in addition to dysfunctional calcium cycling, is now recognized as an important cellular mechanism causing reduced cardiac pump function in a variety of cardiac diseases. Here, we review current knowledge regarding protein-protein interactions involved in the dynamics of thin filament activation and relaxation and the regulation of these processes by protein kinase-mediated phosphorylation.
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Affiliation(s)
- Tomoyoshi Kobayashi
- Department of Physiology & Biophysics, University of Illinois at Chicago, Chicago, IL 60612, USA
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24
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Affiliation(s)
- Allen M. Samarel
- From the Cardiovascular Institute, Loyola University Chicago, Stritch School of Medicine, Maywood, Ill
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25
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Solaro RJ, Rosevear P, Kobayashi T. The unique functions of cardiac troponin I in the control of cardiac muscle contraction and relaxation. Biochem Biophys Res Commun 2007; 369:82-7. [PMID: 18162178 DOI: 10.1016/j.bbrc.2007.12.114] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Accepted: 12/11/2007] [Indexed: 01/02/2023]
Abstract
We review development of evidence and current perceptions of the multiple and significant functions of cardiac troponin I in regulation and modulation of cardiac function. Our emphasis is on the unique structure function relations of the cardiac isoform of troponin I, especially regions containing sites of phosphorylation. The data indicate that modifications of specific regions cardiac troponin I by phosphorylations either promote or reduce cardiac contractility. Thus, a homeostatic balance in these phosphorylations is an important aspect of control of cardiac function. A new concept is the idea that the homeostatic mechanisms may involve modifications of intra-molecular interactions in cardiac troponin I.
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Affiliation(s)
- R John Solaro
- Department of Physiology and Biophysics (M/C901) and Center for Cardiovascular Research, 835 South Wolcott Avenue, University of Illinois at Chicago, College of Medicine, Chicago, IL 60612, USA
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26
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Howarth JW, Meller J, Solaro RJ, Trewhella J, Rosevear PR. Phosphorylation-dependent conformational transition of the cardiac specific N-extension of troponin I in cardiac troponin. J Mol Biol 2007; 373:706-22. [PMID: 17854829 DOI: 10.1016/j.jmb.2007.08.035] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Revised: 08/08/2007] [Accepted: 08/14/2007] [Indexed: 10/22/2022]
Abstract
We present here the solution structure for the bisphosphorylated form of the cardiac N-extension of troponin I (cTnI(1-32)), a region for which there are no previous high-resolution data. Using this structure, the X-ray crystal structure of the cardiac troponin core, and uniform density models of the troponin components derived from neutron contrast variation data, we built atomic models for troponin that show the conformational transition in cardiac troponin induced by bisphosphorylation. In the absence of phosphorylation, our NMR data and sequence analyses indicate a less structured cardiac N-extension with a propensity for a helical region surrounding the phosphorylation motif, followed by a helical C-terminal region (residues 25-30). In this conformation, TnI(1-32) interacts with the N-lobe of cardiac troponin C (cTnC) and thus is positioned to modulate myofilament Ca2+-sensitivity. Bisphosphorylation at Ser23/24 extends the C-terminal helix (residues 21-30) which results in weakening interactions with the N-lobe of cTnC and a re-positioning of the acidic amino terminus of cTnI(1-32) for favorable interactions with basic regions, likely the inhibitory region of cTnI. An extended poly(L-proline)II helix between residues 11 and 19 serves as the rigid linker that aids in re-positioning the amino terminus of cTnI(1-32) upon bisphosphorylation at Ser23/24. We propose that it is these electrostatic interactions between the acidic amino terminus of cTnI(1-32) and the basic inhibitory region of troponin I that induces a bending of cTnI at the end that interacts with cTnC. This model provides a molecular mechanism for the observed changes in cross-bridge kinetics upon TnI phosphorylation.
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Affiliation(s)
- Jack W Howarth
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, Ohio, 45267, USA
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Belin RJ, Sumandea MP, Allen EJ, Schoenfelt K, Wang H, Solaro RJ, de Tombe PP. Augmented Protein Kinase C-α–Induced Myofilament Protein Phosphorylation Contributes to Myofilament Dysfunction in Experimental Congestive Heart Failure. Circ Res 2007; 101:195-204. [PMID: 17556659 DOI: 10.1161/circresaha.107.148288] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
It is becoming clear that upregulated protein kinase C (PKC) signaling plays a role in reduced ventricular myofilament contractility observed in congestive heart failure. However, data are scant regarding which PKC isozymes are involved. There is evidence that PKC-alpha may be of particular importance. Here, we examined PKC-alpha quantity, activity, and signaling to myofilaments in chronically remodeled myocytes obtained from rats in either early heart failure or end-stage congestive heart failure. Immunoblotting revealed that PKC-alpha expression and activation was unaltered in early heart failure but increased in end-stage congestive heart failure. Left ventricular myocytes were isolated by mechanical homogenization, Triton-skinned, and attached to micropipettes that projected from a force transducer and motor. Myofilament function was characterized by an active force-[Ca(2+)] relation to obtain Ca(2+)-saturated maximal force (F(max)) and myofilament Ca(2+) sensitivity (indexed by EC(50)) before and after incubation with PKC-alpha, protein phosphatase type 1 (PP1), or PP2a. PKC-alpha treatment induced a 30% decline in F(max) and 55% increase in the EC(50) in control cells but had no impact on myofilament function in failing cells. PP1-mediated dephosphorylation increased F(max) (15%) and decreased EC(50) ( approximately 20%) in failing myofilaments but had no effect in control cells. PP2a-dependent dephosphorylation had no effect on myofilament function in either group. Lastly, PP1 dephosphorylation restored myofilament function in control cells hyperphosphorylated with PKC-alpha. Collectively, our results suggest that in end-stage congestive heart failure, the myofilament proteins exist in a hyperphosphorylated state attributable, in part, to increased activity and signaling of PKC-alpha.
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Affiliation(s)
- Rashad J Belin
- Department of Physiology and Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, IL 60612, USA
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El-Armouche A, Singh J, Naito H, Wittköpper K, Didié M, Laatsch A, Zimmermann WH, Eschenhagen T. Adenovirus-delivered short hairpin RNA targeting PKCalpha improves contractile function in reconstituted heart tissue. J Mol Cell Cardiol 2007; 43:371-6. [PMID: 17628588 DOI: 10.1016/j.yjmcc.2007.05.021] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Revised: 04/23/2007] [Accepted: 05/29/2007] [Indexed: 12/13/2022]
Abstract
PKCalpha has been shown to be a negative regulator of contractility and PKCalpha gene deletion in mice protected against heart failure. Small interfering (si)RNAs mediate gene silencing by RNA interference (RNAi) and may be used to knockdown PKCalpha in cardiomyocytes. However, transfection efficiencies of (si)RNAs by lipofection tend to be low in primary cells. To address this limitation, we developed an adenoviral vector (AV) driving short hairpin (sh)RNAs against PKCalpha (Ad-shPKCalpha) and evaluated its potential to silence PKCalpha in neonatal rat cardiac myocytes and in engineered heart tissues (EHTs), which resemble functional myocardium in vitro. A nonsense encoding AV (Ad-shNS) served as control. Quantitative PCR and Western blotting showed 90% lower PKCalpha-mRNA and 50% lower PKCalpha protein in Ad-shPKCalpha-infected cells. EHTs were infected with Ad-shPKCalpha on day 11 and subjected to isometric force measurements in organ baths 4 days later. Mean twitch tension was >50% higher in Ad-shPKCalpha compared to Ad-shNS-infected EHTs, under basal and Ca(2+)- or isoprenaline-stimulated conditions. Twitch tension negatively correlated with PKCalpha mRNA levels. In summary, AV-delivered shRNA mediated highly efficient PKCalpha knockdown in cardiac myocytes and improved contractility in EHTs. The data support a role of PKCalpha as a negative regulator of myocardial contractility and demonstrate that EHTs in conjunction with AV-delivered shRNA are a useful model for target validation.
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Affiliation(s)
- Ali El-Armouche
- Institute of Experimental and Clinical Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, D-20246, Germany.
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Xiao L, Zhao Q, Du Y, Yuan C, Solaro RJ, Buttrick PM. PKCepsilon increases phosphorylation of the cardiac myosin binding protein C at serine 302 both in vitro and in vivo. Biochemistry 2007; 46:7054-61. [PMID: 17503784 PMCID: PMC3969456 DOI: 10.1021/bi700467k] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cardiac myosin binding protein C (cMyBPC) phosphorylation is essential for normal cardiac function. Although PKC was reported to phosphorylate cMyBPC in vitro, the relevant PKC isoforms and functions of PKC-mediated cMyBPC phosphorylation are unknown. We recently reported that a transgenic mouse model with cardiac-specific overexpression of PKCepsilon (PKCepsilon TG) displayed enhanced sarcomeric protein phosphorylation and dilated cardiomyopathy. In the present study, we have investigated cMyBPC phosphorylation in PKCepsilon TG mice. Western blotting and two-dimensional gel electrophoresis demonstrated a significant increase in cMyBPC serine (Ser) phosphorylation in 12-month-old TG mice compared to wild type (WT). In vitro PKCepsilon treatment of myofibrils increased the level of cMyBPC Ser phosphorylation in WT mice to that in TG mice, whereas treatment of TG myofibrils with PKCepsilon showed only a minimal increase in cMyBPC Ser phosphorylation. Three peptide motifs of cMyBPC were identified as the potential PKCepsilon consensus sites including a 100% matched motif at Ser302 and two nearly matched motifs at Ser811 and Ser1203. We treated synthetic peptides corresponding to the sequences of these three motifs with PKCepsilon and determined phosphorylation by mass spectrometry and ELISA assay. PKCepsilon induced phosphorylation at the Ser302 site but not at the Ser811 or Ser1203 sites. A S302A point mutation in the Ser302 peptide abolished the PKCepsilon-dependent phosphorylation. Taken together, our data show that the Ser302 on mouse cMyBPC is a likely PKCepsilon phosphorylation site both in vivo and in vitro and may contribute to the dilated cardiomyopathy associated with increased PKCepsilon activity.
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Affiliation(s)
| | | | | | | | | | - Peter M. Buttrick
- Address correspondence to this author at the Division of Cardiology, University of Colorado Health Sciences Center, 4200 East Ninth, Ave., B130, Denver, CO 80262. Tel: (303) 315-5394. Fax: (303) 315-5082.
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Fan X, Markiewicz EJ, Zamora M, Karczmar GS, Roman BB. Comparison and evaluation of mouse cardiac MRI acquired with open birdcage, single loop surface and volume birdcage coils. Phys Med Biol 2006; 51:N451-9. [PMID: 17148815 DOI: 10.1088/0031-9155/51/24/n01] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Although the quality and speed of MR images have vastly improved with the development of novel RF coil technologies, the engineering expertise required to implement them is often not available in many animal in vivo MR laboratories. We present here an open birdcage coil design which is easily constructed with basic RF coil expertise and produces high quality images. The quality and advantages of mouse cardiac MR images acquired with open birdcage coils were evaluated and compared to images acquired with a bent single loop surface, and standard birdcage coils acquired at 4.7 Tesla. Two low pass open birdcage coils, two single loop surface coils, and a low pass volume birdcage coil were constructed and their B(1) distributions were evaluated and compared. The calculated average signal-to-noise ratio for the left ventricular wall was 10, 23 and 32 for the volume birdcage coil, single loop surface coil and open birdcage coil, respectively. The results demonstrate that the open birdcage coil provides greater sensitivity than the volume coil and a higher signal/contrast-to-noise ratio and B(1) homogeneity than the single loop surface coil. The open birdcage coil offers easy access and better quality mouse cardiac imaging than both the single loop surface coil and volume birdcage coil and does not require extensive RF engineering expertise to construct.
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Affiliation(s)
- Xiaobing Fan
- Department of Radiology, University of Chicago, Chicago, IL 60637, USA
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He H, Wang W, Zhang H, Ma L, Wu H, Wang P, Gao J. Fosinopril and Carvedilol Reverse Hypertrophy and Change the Levels of Protein Kinase Cɛ and Components of its Signaling Complex. Cardiovasc Drugs Ther 2006; 20:259-71. [PMID: 17039281 DOI: 10.1007/s10557-006-0079-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To demonstrate the alterations of Protein Kinase C epsilon (PKC epsilon) and components of its signaling complexes after treatment with fosinopril and carvedilol and analyze potential molecular mechanisms of the two drugs for cardiac hypertrophy and heart failure. METHODS Pressure-overload cardiac hypertrophy (POH) was developed in 8-week-old male Sprague Dawley rats by abdominal aortic banding. The rats were divided into three groups at the age of 20 weeks: POH without failure group, reversed POH with drugs group, and POH with failure group on high diet. Western Blot analysis, co-immunoprecipitation and proteomic analysis were performed in ventricular tissues of rat hearts. RESULTS Increased PKC epsilon was found during POH. PKC epsilon decreased during transition from POH to heart failure (HF). However, increased PKC epsilon inclined to recover to normal levels after treatment with both drugs. There were differential proteins in PKC epsilon complexes during the different stages of POH. The two significant PKC epsilon-binding proteins, MAD1 and Lyn A, were only present in PKC epsilon complex during reversing POH with drugs. CONCLUSION Chronic administration of carvedilol and fosinopril could reverse the development of POH and delay the appearance of HF, partly by regulating PKC epsilon level and its signaling complex. MAD1 and Lyn A may be important proteins participating in the reversing process.
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Affiliation(s)
- Hua He
- Department of Internal Medicine, Cardiovascular Institute and Fuwai Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, No167 BeiLishi Road, Xicheng District, Beijing, 100037, People's Republic of China
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Jeong D, Cha H, Kim E, Kang M, Yang DK, Kim JM, Yoon PO, Oh JG, Bernecker OY, Sakata S, Le TT, Cui L, Lee YH, Kim DH, Woo SH, Liao R, Hajjar RJ, Park WJ. PICOT inhibits cardiac hypertrophy and enhances ventricular function and cardiomyocyte contractility. Circ Res 2006; 99:307-14. [PMID: 16809552 DOI: 10.1161/01.res.0000234780.06115.2c] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Multiple signaling pathways involving protein kinase C (PKC) have been implicated in the development of cardiac hypertrophy. We observed that a putative PKC inhibitor, PICOT (PKC-Interacting Cousin Of Thioredoxin) was upregulated in response to hypertrophic stimuli both in vitro and in vivo. This suggested that PICOT may act as an endogenous negative feedback regulator of cardiac hypertrophy through its ability to inhibit PKC activity, which is elevated during cardiac hypertrophy. Adenovirus-mediated gene transfer of PICOT completely blocked the hypertrophic response of neonatal rat cardiomyocytes to enthothelin-1 and phenylephrine, as demonstrated by cell size, sarcomere rearrangement, atrial natriuretic factor expression, and rates of protein synthesis. Transgenic mice with cardiac-specific overexpression of PICOT showed that PICOT is a potent inhibitor of cardiac hypertrophy induced by pressure overload. In addition, PICOT overexpression dramatically increased the ventricular function and cardiomyocyte contractility as measured by ejection fraction and end-systolic pressure of transgenic hearts and peak shortening of isolated cardiomyocytes, respectively. Intracellular Ca(2+) handing analysis revealed that increases in myofilament Ca(2+) responsiveness, together with increased rate of sarcoplasmic reticulum Ca(2+) reuptake, are associated with the enhanced contractility in PICOT-overexpressing cardiomyocytes. The inhibition of cardiac remodeling by of PICOT with a concomitant increase in ventricular function and cardiomyocyte contractility suggests that PICOT may provide an efficient modality for treatment of cardiac hypertrophy and heart failure.
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Affiliation(s)
- Dongtak Jeong
- Department of Life Science, Global Research Laboratory on Cardiovascular Gene Therapy, Gwangju Institute of Science and Technology, Korea
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Murphy AM. Heart failure, myocardial stunning, and troponin: a key regulator of the cardiac myofilament. ACTA ACUST UNITED AC 2006; 12:32-8; quiz 39-40. [PMID: 16470090 DOI: 10.1111/j.1527-5299.2006.04320.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This review discusses post-translational modifications of myofilament regulatory proteins, particularly troponin, associated with heart failure and myocardial stunning--two common disease processes. Altered phosphorylation, partial proteolysis and, possibly, oxidative damage to myofilament proteins may result in abnormalities in both systolic and diastolic function. At a molecular level, these changes may lead to abnormalities in crossbridge cycling and tension development and result in inefficiencies in utilization of energy. Understanding these alterations may lead to new targeted therapies.
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Affiliation(s)
- Anne M Murphy
- Cardiology Division, Department of Pediatrics, Johns Hopkins University School of Medicine, Ross Building 1144, 720 Rutland Avenue, Baltimore, MD 21205, USA.
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Abstract
Although well known as the location of the mechanism by which the cardiac sarcomere is activated by Ca2+ to generate force and shortening, the thin filament is now also recognized as a vital component determining the dynamics of contraction and relaxation. Molecular signaling in the thin filament involves steric, allosteric, and cooperative mechanisms that are modified by protein phosphorylation, sarcomere length and load, the chemical environment, and isoform composition. Approaches employing transgenesis and mutagenesis now permit investigation of these processes at the level of the systems biology of the heart. These studies reveal that the thin filaments are not merely slaves to the levels of Ca2+ determined by membrane channels, transporters and exchangers, but are actively involved in beat to beat control of cardiac function by neural and hormonal factors and by the Frank-Starling mechanism.
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Affiliation(s)
- Tomoyoshi Kobayashi
- Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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MacGowan GA, Rager J, Shroff SG, Mathier MA. In vivo alpha-adrenergic responses and troponin I phosphorylation: anesthesia interactions. J Appl Physiol (1985) 2004; 98:1163-70. [PMID: 15579573 DOI: 10.1152/japplphysiol.00959.2004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mechanisms by which alpha-adrenergic stimulation of the heart in vivo can cause contractile dysfunction are not well understood. We hypothesized that alpha-adrenergic-mediated contractile dysfunction is mediated through protein kinase C phosphorylation of troponin I, which in in vitro experiments has been shown to reduce actomyosin Mg-ATPase activity. We studied pressure-volume loops in transgenic mice expressing mutant troponin I lacking protein kinase C phosphorylation sites and hypothesized altered responses to phenylephrine. As anesthesia agents can produce markedly different effects on contractility, we studied two agents: avertin and alpha-chloralose-urethane. With alpha-chloralose-urethane, at baseline, there were no contractile abnormalities in the troponin I mutants. Phenylephrine produced a 50% reduction in end-systolic elastance in wild-type controls, although a 9% increase in troponin I mutants (P <0.05). Avertin was associated with reduced contractility compared with alpha-chloralose-urethane. Avertin anesthesia, at baseline, produced a reduction in end-systolic elastance by 31% in the troponin I mutants compared with wild-type (P <0.05), and this resulted in further marked systolic and diastolic dysfunction with phenylephrine in the troponin I mutants. Dobutamine produced no significant difference in the contractile phenotype of the transgenic mice with either anesthetic regimen. In conclusion, these data (alpha-chloralose-urethane) demonstrate that alpha-adrenergic-mediated force reduction is mediated through troponin I protein kinase C phosphorylation. beta-Adrenergic responses are not mediated through this pathway. Altering the myofilament force-calcium relationship may result in in vivo increased sensitivity to negative inotropy. Thus choice of a negative inotropic anesthetic agent (avertin) with phenylephrine can lead to profound contractile dysfunction.
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Affiliation(s)
- Guy A MacGowan
- Freeman Hospital, Dept of Cardiology, Newcastle upon Tyne NE7 7DN, UK.
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