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Yampolskaya DS, Kopylova GV, Shchepkin DV, Nabiev SR, Nikitina LV, Walklate J, Ziganshin RH, Bershitsky SY, Geeves MA, Matyushenko AM, Levitsky DI. Pseudo-phosphorylation of essential light chains affects the functioning of skeletal muscle myosin. Biophys Chem 2023; 292:106936. [PMID: 36436358 DOI: 10.1016/j.bpc.2022.106936] [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: 08/19/2022] [Revised: 11/10/2022] [Accepted: 11/18/2022] [Indexed: 11/21/2022]
Abstract
The work aimed to investigate how the phosphorylation of the myosin essential light chain of fast skeletal myosin (LC1) affects the functional properties of the myosin molecule. Using mass-spectrometry, we revealed phosphorylated peptides of LC1 in myosin from different fast skeletal muscles. Mutations S193D and T65D that mimic natural phosphorylation of LC1 were produced, and their effects on functional properties of the entire myosin molecule and isolated myosin head (S1) were studied. We have shown that T65D mutation drastically decreased the sliding velocity of thin filaments in an in vitro motility assay and strongly increased the duration of actin-myosin interaction in optical trap experiments. These effects of T65D mutation in LC1 observed only with the whole myosin but not with S1 were prevented by double T65D/S193D mutation. The T65D and T65D/S193D mutations increased actin-activated ATPase activity of S1 and decreased ADP affinity for the actin-S1 complex. The results indicate that pseudo-phosphorylation of LC1 differently affects the properties of the whole myosin molecule and its isolated head. Also, the results show that phosphorylation of LC1 of skeletal myosin could be one more mechanism of regulation of actin-myosin interaction that needs further investigation.
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Affiliation(s)
- Daria S Yampolskaya
- Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninsky prosp. 33, Moscow 119071, Russia
| | - Galina V Kopylova
- Institute of Immunology and Physiology of the Russian Academy of Sciences, Yekaterinburg 620049, Russia
| | - Daniil V Shchepkin
- Institute of Immunology and Physiology of the Russian Academy of Sciences, Yekaterinburg 620049, Russia
| | - Salavat R Nabiev
- Institute of Immunology and Physiology of the Russian Academy of Sciences, Yekaterinburg 620049, Russia
| | - Larisa V Nikitina
- Institute of Immunology and Physiology of the Russian Academy of Sciences, Yekaterinburg 620049, Russia
| | - Jonathan Walklate
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom
| | - Rustam H Ziganshin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, Moscow 117997, Russia
| | - Sergey Y Bershitsky
- Institute of Immunology and Physiology of the Russian Academy of Sciences, Yekaterinburg 620049, Russia
| | - Michael A Geeves
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom
| | - Alexander M Matyushenko
- Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninsky prosp. 33, Moscow 119071, Russia
| | - Dmitrii I Levitsky
- Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninsky prosp. 33, Moscow 119071, Russia.
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2
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NIMA-related kinase 9 regulates the phosphorylation of the essential myosin light chain in the heart. Nat Commun 2022; 13:6209. [PMID: 36266340 PMCID: PMC9585074 DOI: 10.1038/s41467-022-33658-2] [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: 04/06/2019] [Accepted: 09/28/2022] [Indexed: 12/24/2022] Open
Abstract
To adapt to changing hemodynamic demands, regulatory mechanisms modulate actin-myosin-kinetics by calcium-dependent and -independent mechanisms. We investigate the posttranslational modification of human essential myosin light chain (ELC) and identify NIMA-related kinase 9 (NEK9) to interact with ELC. NEK9 is highly expressed in the heart and the interaction with ELC is calcium-dependent. Silencing of NEK9 results in blunting of calcium-dependent ELC-phosphorylation. CRISPR/Cas9-mediated disruption of NEK9 leads to cardiomyopathy in zebrafish. Binding to ELC is mediated via the protein kinase domain of NEK9. A causal relationship between NEK9 activity and ELC-phosphorylation is demonstrated by genetic sensitizing in-vivo. Finally, we observe significantly upregulated ELC-phosphorylation in dilated cardiomyopathy patients and provide a unique map of human ELC-phosphorylation-sites. In summary, NEK9-mediated ELC-phosphorylation is a calcium-dependent regulatory system mediating cardiac contraction and inotropy.
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Haynes P, Nava KE, Lawson BA, Chung CS, Mitov MI, Campbell SG, Stromberg AJ, Sadayappan S, Bonnell MR, Hoopes CW, Campbell KS. Transmural heterogeneity of cellular level power output is reduced in human heart failure. J Mol Cell Cardiol 2014; 72:1-8. [PMID: 24560668 DOI: 10.1016/j.yjmcc.2014.02.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 01/22/2014] [Accepted: 02/11/2014] [Indexed: 01/04/2023]
Abstract
Heart failure is associated with pump dysfunction and remodeling but it is not yet known if the condition affects different transmural regions of the heart in the same way. We tested the hypotheses that the left ventricles of non-failing human hearts exhibit transmural heterogeneity of cellular level contractile properties, and that heart failure produces transmural region-specific changes in contractile function. Permeabilized samples were prepared from the sub-epicardial, mid-myocardial, and sub-endocardial regions of the left ventricular free wall of non-failing (n=6) and failing (n=10) human hearts. Power, an in vitro index of systolic function, was higher in non-failing mid-myocardial samples (0.59±0.06μWmg(-1)) than in samples from the sub-epicardium (p=0.021) and the sub-endocardium (p=0.015). Non-failing mid-myocardial samples also produced more isometric force (14.3±1.33kNm(-2)) than samples from the sub-epicardium (p=0.008) and the sub-endocardium (p=0.026). Heart failure reduced power (p=0.009) and force (p=0.042) but affected the mid-myocardium more than the other transmural regions. Fibrosis increased with heart failure (p=0.021) and mid-myocardial tissue from failing hearts contained more collagen than matched sub-epicardial (p<0.001) and sub-endocardial (p=0.043) samples. Power output was correlated with the relative content of actin and troponin I, and was also statistically linked to the relative content and phosphorylation of desmin and myosin light chain-1. Non-failing human hearts exhibit transmural heterogeneity of contractile properties. In failing organs, region-specific fibrosis produces the greatest contractile deficits in the mid-myocardium. Targeting fibrosis and sarcomeric proteins in the mid-myocardium may be particularly effective therapies for heart failure.
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Affiliation(s)
- Premi Haynes
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Kristofer E Nava
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Benjamin A Lawson
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Charles S Chung
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Mihail I Mitov
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | - Stuart G Campbell
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
| | | | - Sakthivel Sadayappan
- Department of Cell and Molecular Physiology, Stritch School of Medicine, Loyola University, Chicago, USA
| | - Mark R Bonnell
- Division of Cardiothoracic Surgery, University of Kentucky, Lexington, KY, USA
| | - Charles W Hoopes
- Division of Cardiothoracic Surgery, University of Kentucky, Lexington, KY, USA
| | - Kenneth S Campbell
- Department of Physiology, University of Kentucky, Lexington, KY, USA; Center for Muscle Biology, University of Kentucky, Lexington, KY, USA.
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4
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Sawicki G. Intracellular regulation of matrix metalloproteinase-2 activity: new strategies in treatment and protection of heart subjected to oxidative stress. SCIENTIFICA 2013; 2013:130451. [PMID: 24455428 PMCID: PMC3886579 DOI: 10.1155/2013/130451] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2013] [Accepted: 12/03/2013] [Indexed: 05/15/2023]
Abstract
Much is known regarding cardiac energy metabolism in ischemia/reperfusion (I/R) injury. Under aerobic conditions, the heart prefers to metabolize fatty acids, which contribute to 60-80% of the required ATP. During ischemia, anaerobic glycolysis increases and becomes an important source of ATP for preservation of ion gradients. With reperfusion, fatty acid oxidation quickly recovers and again predominates as the major source of mitochondrial oxidative metabolism. Although a number of molecular mechanisms have been implicated in the development of I/R injury, their relative contributions remain to be determined. One such mechanism involves the proteolytic degradation of contractile proteins, such as troponin I (TnI), myosin heavy chain, titin, and the myosin light chains (MLC1 and MLC2) by matrix metalloproteinase-2 (MMP-2). However, very little is known about intracellular regulation of MMP-2 activity under physiological and pathological conditions. Greater understanding of the mechanisms that govern MMP-2 activity may lead to the development of new therapeutic strategies aimed at preservation of the contractile function of the heart subjected to myocardial infarction (MI) or I/R. This review discusses the intracellular mechanisms controlling MMP-2 activity and highlights a new intracellular therapeutic direction for the prevention and treatment of heart injury.
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Affiliation(s)
- Grzegorz Sawicki
- Department of Pharmacology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK, Canada S7N 5E5
- Department of Clinical Chemistry, Medical University of Wroclaw, Wrovasc Integrated Cardiovascular Centre, 50-556 Wroclaw, Poland
- *Grzegorz Sawicki:
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Meder B, Laufer C, Hassel D, Just S, Marquart S, Vogel B, Hess A, Fishman MC, Katus HA, Rottbauer W. A single serine in the carboxyl terminus of cardiac essential myosin light chain-1 controls cardiomyocyte contractility in vivo. Circ Res 2009; 104:650-9. [PMID: 19168438 DOI: 10.1161/circresaha.108.186676] [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
Although it is well known that mutations in the cardiac essential myosin light chain-1 (cmlc-1) gene can cause hypertrophic cardiomyopathy, the precise in vivo structural and functional roles of cMLC-1 in the heart are only poorly understood. We have isolated the zebrafish mutant lazy susan (laz), which displays severely reduced contractility of both heart chambers. By positional cloning, we identified a nonsense mutation within the zebrafish cmlc-1 gene to be responsible for the laz phenotype, leading to expression of a carboxyl-terminally truncated cMLC-1. Whereas complete loss of cMLC-1 leads to cardiac acontractility attributable to impaired cardiac sarcomerogenesis, expression of a carboxyl-terminally truncated cMLC-1 in laz mutant hearts is sufficient for normal cardiac sarcomerogenesis but severely impairs cardiac contractility in a cell-autonomous fashion. Whereas overexpression of wild-type cMLC-1 restores contractility of laz mutant cardiomyocytes, overexpression of phosphorylation site serine 195-deficient cMLC-1 (cMLC-1(S195A)) does not reconstitute cardiac contractility in laz mutant cardiomyocytes. By contrast, introduction of a phosphomimetic amino acid on position 195 (cMLC-1(S195D)) rescues cardiomyocyte contractility, demonstrating for the first time an essential role of the carboxyl terminus and especially of serine 195 of cMLC-1 in the regulation of cardiac contractility.
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Affiliation(s)
- Benjamin Meder
- Department of Medicine III, University of Heidelberg, Heidelberg, Germany
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Dou Y, Arlock P, Arner A. Blebbistatin specifically inhibits actin-myosin interaction in mouse cardiac muscle. Am J Physiol Cell Physiol 2007; 293:C1148-53. [PMID: 17615158 DOI: 10.1152/ajpcell.00551.2006] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Blebbistatin is a powerful inhibitor of actin-myosin interaction in isolated contractile proteins. To examine whether blebbistatin acts in a similar manner in the organized contractile system of striated muscle, the effects of blebbistatin on contraction of cardiac tissue from mouse were studied. The contraction of paced intact papillary muscle preparations and shortening of isolated cardiomyocytes were inhibited by blebbistatin with inhibitory constants in the micromolar range (1.3-2.8 muM). The inhibition constants are similar to those previously reported for isolated cardiac myosin subfragments showing that blebbistatin action is similar in filamentous myosin of the cardiac contractile apparatus and isolated proteins. The inhibition was not associated with alterations in action potential duration or decreased influx through L-type Ca(2+) channels. Experiments on permeabilized cardiac muscle preparations showed that the inhibition was not due to alterations in Ca(2+) sensitivity of the contractile filaments. The maximal shortening velocity was not affected by 1 muM blebbistatin. In conclusion, we show that blebbistatin is an inhibitor of the actin-myosin interaction in the organized contractile system of cardiac muscle and that its action is not due to effects on the Ca(2+) influx and activation systems.
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Affiliation(s)
- Ying Dou
- Dept. of Physiology and Pharmacology, Karolinska Institutet, SE 171 77 Stockholm, Sweden
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Verduyn SC, Zaremba R, van der Velden J, Stienen GJM. Effects of contractile protein phosphorylation on force development in permeabilized rat cardiac myocytes. Basic Res Cardiol 2007; 102:476-87. [PMID: 17546528 PMCID: PMC2780643 DOI: 10.1007/s00395-007-0663-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Revised: 04/30/2007] [Accepted: 04/30/2007] [Indexed: 11/24/2022]
Abstract
The phosphorylation status of myofibrillar proteins influences the Ca2+ responsiveness of the myofilaments,but the contribution of and the interaction between the individual components is poorly characterized. Therefore, in Langendorff perfused rat hearts (n=30), the phosphorylation levels of cardiac myosin binding protein-C (cMyBP-C), troponin I and T (cTnI, cTnT) and myosin light chain 1 and 2 (MLC-1, MLC-2) were determined by 1- and 2-dimensional gel electrophoresis. Isometric force development, its Ca2+-sensitivity, the rate of tension redevelopment (ktr) and passive force (Fpas) were studied at optimal sarcomere length (2.2 μm) in mechanically isolated,permeabilized cardiomyocytes at 15 °C. Protein phosphorylation was varied by: 1) blocking spontaneous cardiac activity by lidocaine (0.35 mM; Quiescence); 2) electrical stimulation of the hearts at 5 Hz (Contraction) and 3. treatment of contracting hearts with Isoprenaline (1 μM). MLC-2 phosphorylation was increased in the Contraction group almost 2-fold, relative to the Quiescence group, whereas cMyBP-C and cTnI phosphorylation remained the same. Isoprenaline resulted in 3.7-fold increases in both cMyBP-C and cTnI phosphorylation, but did not result in a further increase in MLC-2 phosphorylation.No significant differences were found in maximum force and ktr between groups, both before and after protein kinase A (PKA) treatment. Ca2+-sensitivity in the Contraction and Isoprenaline groups was significantly reduced in comparison to the Quiescence group. These differences were largely abolished by PKA and Fpas was reduced. These results highlight the impact of PKA-dependent phosphorylation on Ca2+-sensitivity and provide evidence for an interaction between the effects of TnI and MLC-2 phosphorylation.
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Affiliation(s)
- S. C. Verduyn
- Laboratory for Physiology, Faculty of Medicine, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center (VUMC), Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - R. Zaremba
- Laboratory for Physiology, Faculty of Medicine, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center (VUMC), Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - J. van der Velden
- Laboratory for Physiology, Faculty of Medicine, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center (VUMC), Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - G. J. M. Stienen
- Laboratory for Physiology, Faculty of Medicine, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center (VUMC), Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
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8
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Hernandez OM, Jones M, Guzman G, Szczesna-Cordary D. Myosin essential light chain in health and disease. Am J Physiol Heart Circ Physiol 2006; 292:H1643-54. [PMID: 17142342 DOI: 10.1152/ajpheart.00931.2006] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The essential light chain of myosin (ELC) is known to be important for structural stability of the alpha-helical lever arm domain of the myosin head, but its function in striated muscle contraction is poorly understood. Two ELC isoforms are expressed in fast skeletal muscle, a long isoform and its NH(2)-terminal approximately 40 amino acid shorter counterpart, whereas only the long ELC is observed in the heart. Biochemical and structural studies revealed that the NH(2)-terminus of the long ELC can make direct contacts with actin, but the effects of the ELC on the affinity of myosin for actin, ATPase, force, and the kinetics of force generating myosin cross-bridges are inconclusive. Myosin containing the long ELC has been shown to have slower cross-bridge kinetics than myosin with the short isoform. A difference was also reported among myosins with long isoforms. Increased shortening velocity was observed in atrial compared with ventricular muscle fibers. The common findings suggest that ELC provides the fine tuning of the myosin motor function, which is regulated in an isoform and tissue-dependent manner. The functional importance of the ELC is further implicated by the discovery of ELC mutations associated with Familial Hypertrophic Cardiomyopathy. The pathological phenotypes vary in severity, but more notably, almost all ELC mutations result in sudden cardiac death at a young age. This review summarizes the functional roles of striated muscle ELC in normal healthy muscle and in disease. Transgenic animal models and phenotypic characterization of ELC-mediated remodeling of the heart are also discussed.
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Affiliation(s)
- Olga M Hernandez
- Department of Molecular and Cellular Pharmacology, University of Miami, Leonard M. Miller School of Medicine, Miami Florida 33136, USA
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9
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Zobel C, Zavidou-Saroti P, Bölck B, Brixius K, Reuter H, Frank K, Diedrichs H, Müller-Ehmsen J, Bloch W, Schwinger RHG. Altered tension cost in (TG(mREN-2)27) rats overexpressing the mouse renin gene. Eur J Appl Physiol 2006; 99:121-32. [PMID: 17063360 DOI: 10.1007/s00421-006-0323-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2006] [Indexed: 10/24/2022]
Abstract
The present study aimed to characterize cardiac hypertrophy induced by activation of the renin-angiotensin system in terms of functional alterations on the level of the contractile proteins, employing transgenic rats harboring the mouse renin gene (TGR(mREN2)27). Ca2+-dependent tension and myosin ATPase activity were measured in skinned fiber preparations obtained from TGR(mREN2)27 and from age-matched Sprague-Dawley rats (SPDR). Western blots for troponin I (TnI) and troponin T (TnT) were performed and the phosphorylation status of TnI were evaluated in myocardial preparations. TnT and myosin heavy chain (MHC) isoforms were analyzed by RT-PCR. The pCa/tension relationship was shifted to the right in TGR(mREN2)27 compared to SPDR as indicated by increased Ca2+-concentrations required for half maximal activation of tension (SPDR 5.80, 95% confidence limits 5.77-5.82 vs. TGR(mREN2)27 5.69, 95% confidence limits 5.67-5.72, pCa units), while maximal developed tension was unaltered. Even more pronounced was the shift in the relationship between pCa and myosin-ATPase (SPDR 6.01, 95% confidence limits 5.99-6.03 vs. TGR(mREN2)27 5.77, 95% confidence limits 5.73-5.79, pCa units). The maximal myosin-ATPase activity was reduced in TGR(mREN2)27 compared to SPDR, respectively (211.0 +/- 28.77 micromol ADP/s vs. 271.6 +/- 43.66 micromol ADP/s, P < 0.05). Tension cost (ATPase activity/tension) was significantly reduced in TGR(mREN2)27. The beta-MHC expression was significantly increased in TGR(mREN2)27. There was no isoform shift for TnT (protein and mRNA), as well as TnI, and no alteration of the phosphorylation of TnI in TGR(mREN2)27 compared to SPRD. The present study demonstrates that cardiac hypertrophy, induced by an activation of the renin-angiotensin system, leads to adapting alterations on the level of the contractile filaments, which reduce tension cost.
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Affiliation(s)
- Carsten Zobel
- Laboratory of Muscle Research and Molecular Cardiology, Department of Internal Medicine III, University of Cologne, Joseph-Stelzmann-Str. 9, 50924, Cologne, Germany.
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Antoons G, Mubagwa K, Nevelsteen I, Sipido KR. Mechanisms underlying the frequency dependence of contraction and [Ca(2+)](i) transients in mouse ventricular myocytes. J Physiol 2002; 543:889-98. [PMID: 12231646 PMCID: PMC2290543 DOI: 10.1113/jphysiol.2002.025619] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In most mammalian species force of contraction of cardiac muscle increases with increasing rate of stimulation, i.e. a positive force-frequency relationship. In single mouse ventricular cells, both positive and negative relationships have been described and little is known about the underlying mechanisms. We studied enzymatically isolated single ventricular mouse myocytes, at 30 degrees C. During field stimulation, amplitude of unloaded cell shortening increased with increasing frequency of stimulation (0.04 +/- 0.01 Delta L/L(0) at 1 Hz to 0.07 +/- 0.01 Delta L/L(0) at 4 Hz, n = 12, P < 0.05). During whole cell voltage clamp with 50 microM [K5-fluo-3](pip), both peak and baseline [Ca(2+)](i) increased at higher stimulation frequencies, but the net Delta[Ca(2+)](i) increased only modestly from 1.59 +/- 0.08 Delta F/F(0) at 1 Hz, to 1.71 +/- 0.11 Delta F/F(0) at 4 Hz (n = 17, P < 0.05). When a 1 s pause was interposed during stimulation at 2 and 4 Hz, [Ca(2+)](i) transients were significantly larger (at 4 Hz, peak F/F(0) increased by 78 +/- 2 %, n = 5). SR Ca(2+) content assessed during caffeine application, significantly increased from 91 +/- 24 micromol l(-1) at 1 Hz to 173 +/- 20 micromol l(-1) at 4 Hz (n = 5, P < 0.05). Peak I(Ca,L) decreased at higher frequencies (by 28 +/- 6 % at 2 Hz, and 45 +/- 8 % at 4 Hz), due to slow recovery from inactivation. This loss of I(Ca,L) resulted in reduced fractional release. Thus, in mouse ventricular myocytes the [Ca(2+)](i)-frequency response depends on a balance between the increase in SR content and the loss of trigger I(Ca,L). Small changes in this balance may contribute to variability in frequency-dependent behaviour. In addition, there may be a regulation of the contractile response downstream of [Ca(2+)](i).
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Affiliation(s)
- Gudrun Antoons
- Laboratory of Experimental Cardiology, University of Leuven, Belgium
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11
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Arrell DK, Neverova I, Fraser H, Marbán E, Van Eyk JE. Proteomic analysis of pharmacologically preconditioned cardiomyocytes reveals novel phosphorylation of myosin light chain 1. Circ Res 2001; 89:480-7. [PMID: 11557734 DOI: 10.1161/hh1801.097240] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Proteomic analysis of rabbit ventricular myocytes revealed a novel posttranslational modification to myosin light chain 1 (MLC1), consisting of phosphorylation at two sites. Subproteomic extraction to isolate myofilament-enriched fractions enabled determination of the extent of phosphorylation, which increased from 25.7+/-1.6% to 34.0+/-2.7% (mean+/-SE, n=4; P<0.05) after adenosine treatment at levels sufficient to pharmacologically precondition the myocytes (100 micromol/L). Mass spectrometry of MLC1 tryptic digests identified two peptide fragments modified by phosphorylation. These two phosphopeptides were characterized by peptide mass fingerprinting to determine the phosphorylation sites within rabbit ventricular MLC1, which correspond to Thr69 and Ser200 of rat MLC1, and to Thr64 and Ser194 or 195 of human MLC1. This proteomic analysis of preconditioned myocardium has revealed a previously unsuspected in vivo posttranslational modification to MLC1.
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Affiliation(s)
- D K Arrell
- Department of Physiology, Queen's University, Kingston, Ontario, Canada
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12
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van der Velden J, Moorman AF, Stienen GJ. Age-dependent changes in myosin composition correlate with enhanced economy of contraction in guinea-pig hearts. J Physiol 1998; 507 ( Pt 2):497-510. [PMID: 9518708 PMCID: PMC2230794 DOI: 10.1111/j.1469-7793.1998.497bt.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
1. The composition of myosin heavy chains (MHCs) was investigated in young (1- to 8-week-old) and mature (9- to 26-week-old) guinea-pigs using two monoclonal antibodies directed specifically against alpha-MHC and beta-MHC. In addition, maximum force and the rate of ATP consumption during isometric contraction were measured in chemically skinned trabeculae taken from the same hearts. 2. An age-dependent shift in the MHC composition was found. The alpha-MHC fraction decreased from 0.17 +/- 0.02 (mean +/- S.E.M.; n = 24) in young to 0.04 +/- 0.01 (n = 43) in mature hearts. This shift was correlated with a decrease in tension cost (i.e. ATP consumption per second per trabecula volume/force per cross-sectional area) from 4.1 +/- 0.2 mmol kN-1 m-1 s-1 (n = 23) in young to 2.5 +/- 0.1 mmol kN-1 m-1 s-1 (n = 57) in mature hearts. 3. From the results it follows that the slow beta-MHC isoform, which predominates in hearts of mature guinea-pigs, is about 5 times more economical than the fast alpha-MHC isoform. Calcium sensitivity of force and ATP consumption decreased with age, but stabilized within a few weeks after birth. The pronounced dependence of cardiac energetics on MHC composition should be taken into account in long-term studies of cardiac overload.
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Affiliation(s)
- J van der Velden
- Laboratory for Physiology, Institute for Cardiovascular Research, Free University, Amsterdam, The Netherlands.
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13
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Schaub MC, Hefti MA, Zuellig RA, Morano I. Modulation of contractility in human cardiac hypertrophy by myosin essential light chain isoforms. Cardiovasc Res 1998; 37:381-404. [PMID: 9614495 DOI: 10.1016/s0008-6363(97)00258-7] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Cardiac hypertrophy is an adaptive response that normalizes wall stress and compensates for increased workload. It is accompanied by distinct qualitative and quantitative changes in the expression of protein isoforms concerning contractility, intracellular Ca(2+)-homeostasis and metabolism. Changes in the myosin subunit isoform expression improves contractility by an increase in force generation at a given Ca(2+)-concentration (increased Ca(2+)-sensitivity) and by improving the economy of the chemo-mechanical transduction process per amount of utilised ATP (increased duty ratio). In the human atrium this is achieved by partial replacement of the endogenous fast myosin by the ventricular slow-type heavy and light chains. In the hypertrophic human ventricle the slow-type beta-myosin heavy chains remain unchanged, but the ectopic expression of the atrial myosin essential light chain (ALC1) partially replaces the endogenous ventricular isoform (VLC1). The ventricular contractile apparatus with myosin containing ALC1 is characterised by faster cross-bridge kinetics, a higher Ca(2+)-sensitivity of force generation and an increased duty ratio. The mechanism for cross-bridge modulation relies on the extended Ala-Pro-rich N-terminus of the essential light chains of which the first eleven residues interact with the C-terminus of actin. A change in charge in this region between ALC1 and VLC1 explains their functional difference. The intracellular Ca(2+)-handling may be impaired in heart failure, resulting in either higher or lower cytosolic Ca(2+)-levels. Thus the state of the cardiomyocyte determines whether this hypertrophic adaptation remains beneficial or becomes detrimental during failure. Also discussed are the effects on contractility of long-term changes in isoform expression of other sarcomeric proteins. Positive and negative modulation of contractility by short-term phosphorylation reactions at multiple sites in the myosin regulatory light chain, troponin-I, troponin-T, alpha-tropomyosin and myosin binding protein-C are considered in detail.
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Affiliation(s)
- M C Schaub
- Institute of Pharmacology, University of Zurich, Switzerland.
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Clement O, Puceat M, Walsh MP, Vassort G. Protein kinase C enhances myosin light-chain kinase effects on force development and ATPase activity in rat single skinned cardiac cells. Biochem J 1992; 285 ( Pt 1):311-7. [PMID: 1386218 PMCID: PMC1132782 DOI: 10.1042/bj2850311] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Many neurohormones alter the force of cardiac contraction by variations in the intracellular Ca2+ concentration. alpha 1-Adrenergic and muscarinic stimulations, rather, modify the sensitivity of contractile proteins to Ca(2+)-calmodulin-myosin light-chain kinase (MLCK) complex induces a large increase in Ca2+ sensitivity (0.14 pCa unit) of these easily accessible myofilaments. This increase is further enhanced by up to 0.19 pCa unit when protein kinase C (PKC) is added together with MLCK. Similarly, the Ca2+ ATPase activity of skinned cells in suspension is increased in the presence of MLCK and further in the presence of both kinases. 32P-labelling and SDS/PAGE show that these changes are associated with light-chain 2 (LC2) phosphorylation together with phosphorylation of troponin I and troponin T when PKC is added. Although to a smaller extent than in smooth muscle, phosphorylation of cardiac myosin LC2 may be involved in the modulation of heart contractility.
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Affiliation(s)
- O Clement
- Unité de Recherches de Physiologie Cellulaire Cardiaque, INSERM U-241, Université Paris-Sud, Orsay, France
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15
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Boels PJ, Pfitzer G. Relaxant effect of phalloidin on Triton-skinned microvascular and other smooth muscle preparations. J Muscle Res Cell Motil 1992; 13:71-80. [PMID: 1313442 DOI: 10.1007/bf01738430] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Guinea pig mesenteric microarteries (diameter 60-100 microns), the main branch of the mesenteric artery and taenia coli were skinned with 1% Triton X-100 for 4 h at 4 degrees C. Microarteries, mounted for circumferential force measurement, developed maximal active force in response to elevation of the free Ca2+ (pCa = 4.52, in EGTA buffer) in the presence of ATP (7.5 mM) and calmodulin (0.1-0.3 microM). In these preparations, addition of phalloidin (1-100 microM) slowly (greater than 1 h) relaxed submaximal contractions (pCa greater than 4.52) in a dose-dependent manner. Relaxation was irreversible as, after phalloidin wash-out, subsequent active force to pCa = 4.52 was also reduced. By contrast, phalloidin preincubation and wash-out under relaxed conditions (pCa greater than 8) only reduced subsequent force to pCa = 4.52 on prolonged stimulation. The extent of phalloidin-induced relaxation was not dependent on free Ca2+ between pCa 6.40 and 4.52. Phalloidin-induced relaxation did not occur during rigor contractions (i.e. absence of ATP and Ca2+). These mechanical effects of phalloidin were accompanied by a decreased leak of actin out of the skinned preparations and by the prevention of guanidine extraction of actin from these preparations. Phalloidin did not inhibit the myosin light chain kinase or phosphatase activity isolated from these preparations. In addition, the relaxant effects were also noted in taenia coli and the main branch of the mesenteric artery but not in skinned porcine ventricular heart muscle. These experiments suggest the possible participation of actin filament dynamics on the maintenance of active force in Triton-skinned smooth muscle.
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MESH Headings
- Animals
- Colon/drug effects
- Colon/enzymology
- Colon/physiology
- Dose-Response Relationship, Drug
- Electrophoresis, Polyacrylamide Gel
- Guinea Pigs
- Mesenteric Arteries/drug effects
- Mesenteric Arteries/enzymology
- Mesenteric Arteries/physiology
- Microcirculation/physiology
- Muscle Relaxation/drug effects
- Muscle, Smooth/drug effects
- Muscle, Smooth/enzymology
- Muscle, Smooth/physiology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/enzymology
- Muscle, Smooth, Vascular/physiology
- Myosin-Light-Chain Kinase/metabolism
- Octoxynol
- Phalloidine/pharmacology
- Phosphoric Monoester Hydrolases/metabolism
- Polyethylene Glycols
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Affiliation(s)
- P J Boels
- II. Physiologisches Institut, Universität Heidelberg, Germany
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