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Nayak A, Wang T, Franz P, Steffen W, Chizhov I, Tsiavaliaris G, Amrute-Nayak M. Single-molecule analysis reveals that regulatory light chains fine-tune skeletal myosin II function. J Biol Chem 2020; 295:7046-7059. [PMID: 32273340 DOI: 10.1074/jbc.ra120.012774] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 04/07/2020] [Indexed: 11/06/2022] Open
Abstract
Myosin II is the main force-generating motor during muscle contraction. Myosin II exists as different isoforms that are involved in diverse physiological functions. One outstanding question is whether the myosin heavy chain (MHC) isoforms alone account for these distinct physiological properties. Unique sets of essential and regulatory light chains (RLCs) are known to assemble with specific MHCs, raising the intriguing possibility that light chains contribute to specialized myosin functions. Here, we asked whether different RLCs contribute to this functional diversification. To this end, we generated chimeric motors by reconstituting the MHC fast isoform (MyHC-IId) and slow isoform (MHC-I) with different light-chain variants. As a result of the RLC swapping, actin filament sliding velocity increased by ∼10-fold for the slow myosin and decreased by >3-fold for the fast myosin. Results from ensemble molecule solution kinetics and single-molecule optical trapping measurements provided in-depth insights into altered chemo-mechanical properties of the myosin motors that affect the sliding speed. Notably, we found that the mechanical output of both slow and fast myosins is sensitive to the RLC isoform. We therefore propose that RLCs are crucial for fine-tuning the myosin function.
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Affiliation(s)
- Arnab Nayak
- Institute of Molecular and Cell Physiology, Hannover Medical School, 30625 Hannover, Germany
| | - Tianbang Wang
- Institute of Molecular and Cell Physiology, Hannover Medical School, 30625 Hannover, Germany
| | - Peter Franz
- Institute of Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany
| | - Walter Steffen
- Institute of Molecular and Cell Physiology, Hannover Medical School, 30625 Hannover, Germany
| | - Igor Chizhov
- Institute of Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany
| | - Georgios Tsiavaliaris
- Institute of Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany
| | - Mamta Amrute-Nayak
- Institute of Molecular and Cell Physiology, Hannover Medical School, 30625 Hannover, Germany
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Toepfer CN, Garfinkel AC, Venturini G, Wakimoto H, Repetti G, Alamo L, Sharma A, Agarwal R, Ewoldt JF, Cloonan P, Letendre J, Lun M, Olivotto I, Colan S, Ashley E, Jacoby D, Michels M, Redwood CS, Watkins HC, Day SM, Staples JF, Padrón R, Chopra A, Ho CY, Chen CS, Pereira AC, Seidman JG, Seidman CE. Myosin Sequestration Regulates Sarcomere Function, Cardiomyocyte Energetics, and Metabolism, Informing the Pathogenesis of Hypertrophic Cardiomyopathy. Circulation 2020; 141:828-842. [PMID: 31983222 PMCID: PMC7077965 DOI: 10.1161/circulationaha.119.042339] [Citation(s) in RCA: 165] [Impact Index Per Article: 41.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 12/20/2019] [Indexed: 12/15/2022]
Abstract
BACKGROUND Hypertrophic cardiomyopathy (HCM) is caused by pathogenic variants in sarcomere protein genes that evoke hypercontractility, poor relaxation, and increased energy consumption by the heart and increased patient risks for arrhythmias and heart failure. Recent studies show that pathogenic missense variants in myosin, the molecular motor of the sarcomere, are clustered in residues that participate in dynamic conformational states of sarcomere proteins. We hypothesized that these conformations are essential to adapt contractile output for energy conservation and that pathophysiology of HCM results from destabilization of these conformations. METHODS We assayed myosin ATP binding to define the proportion of myosins in the super relaxed state (SRX) conformation or the disordered relaxed state (DRX) conformation in healthy rodent and human hearts, at baseline and in response to reduced hemodynamic demands of hibernation or pathogenic HCM variants. To determine the relationships between myosin conformations, sarcomere function, and cell biology, we assessed contractility, relaxation, and cardiomyocyte morphology and metabolism, with and without an allosteric modulator of myosin ATPase activity. We then tested whether the positions of myosin variants of unknown clinical significance that were identified in patients with HCM, predicted functional consequences and associations with heart failure and arrhythmias. RESULTS Myosins undergo physiological shifts between the SRX conformation that maximizes energy conservation and the DRX conformation that enables cross-bridge formation with greater ATP consumption. Systemic hemodynamic requirements, pharmacological modulators of myosin, and pathogenic myosin missense mutations influenced the proportions of these conformations. Hibernation increased the proportion of myosins in the SRX conformation, whereas pathogenic variants destabilized these and increased the proportion of myosins in the DRX conformation, which enhanced cardiomyocyte contractility, but impaired relaxation and evoked hypertrophic remodeling with increased energetic stress. Using structural locations to stratify variants of unknown clinical significance, we showed that the variants that destabilized myosin conformations were associated with higher rates of heart failure and arrhythmias in patients with HCM. CONCLUSIONS Myosin conformations establish work-energy equipoise that is essential for life-long cellular homeostasis and heart function. Destabilization of myosin energy-conserving states promotes contractile abnormalities, morphological and metabolic remodeling, and adverse clinical outcomes in patients with HCM. Therapeutic restabilization corrects cellular contractile and metabolic phenotypes and may limit these adverse clinical outcomes in patients with HCM.
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Affiliation(s)
- Christopher N. Toepfer
- Department of Genetics, Harvard Medical School, Boston, MA (C.N.T., A.C.G., G.V., H.W., G.R., A.S., R.A., A.C.P., J.G.S., C.E.S.)
- Cardiovascular Medicine, Radcliffe Department of Medicine (C.N.T., C.S.R., H.C.W.), University of Oxford, UK
- Wellcome Centre for Human Genetics (C.N.T., H.C.W.), University of Oxford, UK
| | - Amanda C. Garfinkel
- Department of Genetics, Harvard Medical School, Boston, MA (C.N.T., A.C.G., G.V., H.W., G.R., A.S., R.A., A.C.P., J.G.S., C.E.S.)
| | - Gabriela Venturini
- Department of Genetics, Harvard Medical School, Boston, MA (C.N.T., A.C.G., G.V., H.W., G.R., A.S., R.A., A.C.P., J.G.S., C.E.S.)
- Laboratory of Genetics and Molecular Cardiology, Heart Institute (InCor)-University of São Paulo Medical School, Brazil (G.V., A.C.P.)
| | - Hiroko Wakimoto
- Department of Genetics, Harvard Medical School, Boston, MA (C.N.T., A.C.G., G.V., H.W., G.R., A.S., R.A., A.C.P., J.G.S., C.E.S.)
| | - Giuliana Repetti
- Department of Genetics, Harvard Medical School, Boston, MA (C.N.T., A.C.G., G.V., H.W., G.R., A.S., R.A., A.C.P., J.G.S., C.E.S.)
| | - Lorenzo Alamo
- Centro de Biología Estructural, Instituto Venezolano de Investigaciones Cientifìcas (IVIC), Caracas (L.A., R.P.)
| | - Arun Sharma
- Department of Genetics, Harvard Medical School, Boston, MA (C.N.T., A.C.G., G.V., H.W., G.R., A.S., R.A., A.C.P., J.G.S., C.E.S.)
| | - Radhika Agarwal
- Department of Genetics, Harvard Medical School, Boston, MA (C.N.T., A.C.G., G.V., H.W., G.R., A.S., R.A., A.C.P., J.G.S., C.E.S.)
| | - Jourdan F. Ewoldt
- Department of Biomedical Engineering, Boston University, MA (J.F.E., P.C., J.L., A.C., C.S.C.)
| | - Paige Cloonan
- Department of Biomedical Engineering, Boston University, MA (J.F.E., P.C., J.L., A.C., C.S.C.)
| | - Justin Letendre
- Department of Biomedical Engineering, Boston University, MA (J.F.E., P.C., J.L., A.C., C.S.C.)
| | - Mingyue Lun
- Department of Medicine, Division of Genetics (M.L.), Brigham and Women’s Hospital, Boston, MA
| | - Iacopo Olivotto
- Cardiomyopathy Unit and Genetic Unit, Careggi University Hospital, Florence, Italy (I.O.)
| | - Steve Colan
- Department of Cardiology, Boston Children’s Hospital, MA (S.C.)
| | - Euan Ashley
- Center for Inherited Cardiovascular Disease, Stanford University, CA (E.A.)
| | - Daniel Jacoby
- Department of Internal Medicine, Section of Cardiovascular Diseases, Yale School of Medicine, New Haven, CT (D.J.)
| | - Michelle Michels
- Department of Cardiology, Thorax Center, Erasmus MC, Rotterdam, The Netherlands (M.M.)
| | - Charles S. Redwood
- Cardiovascular Medicine, Radcliffe Department of Medicine (C.N.T., C.S.R., H.C.W.), University of Oxford, UK
| | - Hugh C. Watkins
- Cardiovascular Medicine, Radcliffe Department of Medicine (C.N.T., C.S.R., H.C.W.), University of Oxford, UK
- Wellcome Centre for Human Genetics (C.N.T., H.C.W.), University of Oxford, UK
| | - Sharlene M. Day
- Department of Internal Medicine, University of Michigan, Ann Arbor (S.M.D.)
| | - James F. Staples
- Department of Biology, University of Western Ontario, London, Canada (J.F.S.)
| | - Raúl Padrón
- Centro de Biología Estructural, Instituto Venezolano de Investigaciones Cientifìcas (IVIC), Caracas (L.A., R.P.)
- Division of Cell Biology and Imaging, Department of Radiology, University of Massachusetts Medical School, Worcester (R.P.)
| | - Anant Chopra
- Department of Biomedical Engineering, Boston University, MA (J.F.E., P.C., J.L., A.C., C.S.C.)
| | - Carolyn Y. Ho
- Cardiovascular Division (C.Y.H., C.E.S.), Brigham and Women’s Hospital, Boston, MA
| | - Christopher S. Chen
- Department of Biomedical Engineering, Boston University, MA (J.F.E., P.C., J.L., A.C., C.S.C.)
| | - Alexandre C. Pereira
- Department of Genetics, Harvard Medical School, Boston, MA (C.N.T., A.C.G., G.V., H.W., G.R., A.S., R.A., A.C.P., J.G.S., C.E.S.)
- Laboratory of Genetics and Molecular Cardiology, Heart Institute (InCor)-University of São Paulo Medical School, Brazil (G.V., A.C.P.)
| | - Jonathan G. Seidman
- Department of Genetics, Harvard Medical School, Boston, MA (C.N.T., A.C.G., G.V., H.W., G.R., A.S., R.A., A.C.P., J.G.S., C.E.S.)
| | - Christine E. Seidman
- Department of Genetics, Harvard Medical School, Boston, MA (C.N.T., A.C.G., G.V., H.W., G.R., A.S., R.A., A.C.P., J.G.S., C.E.S.)
- Cardiovascular Division (C.Y.H., C.E.S.), Brigham and Women’s Hospital, Boston, MA
- Howard Hughes Medical Institute, Chevy Chase, MD (C.E.S.)
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X Cai L, Tanada Y, D Bello G, C Fleming J, F Alkassis F, Ladd T, Golde T, Koh J, Chen S, Kasahara H. Cardiac MLC2 kinase is localized to the Z-disc and interacts with α-actinin2. Sci Rep 2019; 9:12580. [PMID: 31467300 PMCID: PMC6715661 DOI: 10.1038/s41598-019-48884-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 08/13/2019] [Indexed: 02/07/2023] Open
Abstract
Cardiac contractility is enhanced by phosphorylation of myosin light chain 2 (MLC2) by cardiac-specific MLC kinase (cMLCK), located at the neck region of myosin heavy chain. In normal mouse and human hearts, the level of phosphorylation is maintained relatively constant, at around 30-40% of total MLC2, likely by well-balanced phosphorylation and phosphatase-dependent dephosphorylation. Overexpression of cMLCK promotes sarcomere organization, while the loss of cMLCK leads to cardiac atrophy in vitro and in vivo. In this study, we showed that cMLCK is predominantly expressed at the Z-disc with additional diffuse cytosolic expression in normal adult mouse and human hearts. cMLCK interacts with the Z-disc protein, α-actinin2, with a high-affinity kinetic value of 13.4 ± 0.1 nM through the N-terminus region of cMLCK unique to cardiac-isoform. cMLCK mutant deficient for interacting with α-actinin2 did not promote sarcomeric organization and reduced cardiomyocyte cell size. In contrast, a cMLCK kinase-deficient mutant showed effects similar to wild-type cMLCK on sarcomeric organization and cardiomyocyte cell size. Our results suggest that cMLCK plays a role in sarcomere organization, likely distinct from its role in phosphorylating MLC2, both of which will contribute to the enhancement of cardiac contractility.
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Affiliation(s)
- Lawrence X Cai
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - Yohei Tanada
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - Gregory D Bello
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - James C Fleming
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - Fariz F Alkassis
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - Thomas Ladd
- Department of Neuroscience, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - Todd Golde
- Department of Neuroscience, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - Jin Koh
- Proteomics and Mass Spectrometry, Interdisciplinary Center for Biotechnology Research (ICBR), University of Florida, Gainesville, FL, 32610, USA
| | - Sixue Chen
- Proteomics and Mass Spectrometry, Interdisciplinary Center for Biotechnology Research (ICBR), University of Florida, Gainesville, FL, 32610, USA.,Department of Biology, Genetics Institute, Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL, 32610, USA
| | - Hideko Kasahara
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, 32610, USA.
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4
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Chang AN, Kamm KE, Stull JT. Role of myosin light chain phosphatase in cardiac physiology and pathophysiology. J Mol Cell Cardiol 2016; 101:35-43. [PMID: 27742556 DOI: 10.1016/j.yjmcc.2016.10.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 10/07/2016] [Accepted: 10/10/2016] [Indexed: 11/18/2022]
Abstract
Maintenance of contractile performance of the heart is achieved in part by the constitutive 40% phosphorylation of myosin regulatory light chain (RLC) in sarcomeres. The importance of this extent of RLC phosphorylation for optimal cardiac performance becomes apparent when various mouse models and resultant phenotypes are compared. The absence or attenuation of RLC phosphorylation results in poor performance leading to heart failure, whereas increased RLC phosphorylation is associated with cardiac protection from stresses. Although information is limited, RLC phosphorylation appears compromised in human heart failure which is consistent with data from mouse studies. The extent of cardiac RLC phosphorylation is determined by the balanced activities of cardiac myosin light chain kinases and phosphatases, the regulatory mechanisms of which are now emerging. This review thusly focuses on kinases that may participate in phosphorylating RLC to make the substrate for cardiac myosin light chain phosphatases, in addition to providing perspectives on the family of myosin light chain phosphatases and involved signaling mechanisms. Because biochemical and physiological information about cardiac myosin light chain phosphatase is sparse, such studies represent an emerging area of investigation in health and disease.
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Affiliation(s)
- Audrey N Chang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Kristine E Kamm
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - James T Stull
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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5
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Toepfer CN, West TG, Ferenczi MA. Revisiting Frank-Starling: regulatory light chain phosphorylation alters the rate of force redevelopment (ktr ) in a length-dependent fashion. J Physiol 2016; 594:5237-54. [PMID: 27291932 PMCID: PMC5023691 DOI: 10.1113/jp272441] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 06/01/2016] [Indexed: 11/24/2022] Open
Abstract
Key points Regulatory light chain (RLC) phosphorylation has been shown to alter the ability of muscle to produce force and power during shortening and to alter the rate of force redevelopment (ktr) at submaximal [Ca2+]. Increasing RLC phosphorylation ∼50% from the in vivo level in maximally [Ca2+]‐activated cardiac trabecula accelerates ktr. Decreasing RLC phosphorylation to ∼70% of the in vivo control level slows ktr and reduces force generation. ktr is dependent on sarcomere length in the physiological range 1.85–1.94 μm and RLC phosphorylation modulates this response. We demonstrate that Frank–Starling is evident at maximal [Ca2+] activation and therefore does not necessarily require length‐dependent change in [Ca2+]‐sensitivity of thin filament activation. The stretch response is modulated by changes in RLC phosphorylation, pinpointing RLC phosphorylation as a modulator of the Frank–Starling law in the heart. These data provide an explanation for slowed systolic function in the intact heart in response to RLC phosphorylation reduction.
Abstract Force and power in cardiac muscle have a known dependence on phosphorylation of the myosin‐associated regulatory light chain (RLC). We explore the effect of RLC phosphorylation on the ability of cardiac preparations to redevelop force (ktr) in maximally activating [Ca2+]. Activation was achieved by rapidly increasing the temperature (temperature‐jump of 0.5–20ºC) of permeabilized trabeculae over a physiological range of sarcomere lengths (1.85–1.94 μm). The trabeculae were subjected to shortening ramps over a range of velocities and the extent of RLC phosphorylation was varied. The latter was achieved using an RLC‐exchange technique, which avoids changes in the phosphorylation level of other proteins. The results show that increasing RLC phosphorylation by 50% accelerates ktr by ∼50%, irrespective of the sarcomere length, whereas decreasing phosphorylation by 30% slows ktr by ∼50%, relative to the ktr obtained for in vivo phosphorylation. Clearly, phosphorylation affects the magnitude of ktr following step shortening or ramp shortening. Using a two‐state model, we explore the effect of RLC phosphorylation on the kinetics of force development, which proposes that phosphorylation affects the kinetics of both attachment and detachment of cross‐bridges. In summary, RLC phosphorylation affects the rate and extent of force redevelopment. These findings were obtained in maximally activated muscle at saturating [Ca2+] and are not explained by changes in the Ca2+‐sensitivity of acto‐myosin interactions. The length‐dependence of the rate of force redevelopment, together with the modulation by the state of RLC phosphorylation, suggests that these effects play a role in the Frank–Starling law of the heart. Regulatory light chain (RLC) phosphorylation has been shown to alter the ability of muscle to produce force and power during shortening and to alter the rate of force redevelopment (ktr) at submaximal [Ca2+]. Increasing RLC phosphorylation ∼50% from the in vivo level in maximally [Ca2+]‐activated cardiac trabecula accelerates ktr. Decreasing RLC phosphorylation to ∼70% of the in vivo control level slows ktr and reduces force generation. ktr is dependent on sarcomere length in the physiological range 1.85–1.94 μm and RLC phosphorylation modulates this response. We demonstrate that Frank–Starling is evident at maximal [Ca2+] activation and therefore does not necessarily require length‐dependent change in [Ca2+]‐sensitivity of thin filament activation. The stretch response is modulated by changes in RLC phosphorylation, pinpointing RLC phosphorylation as a modulator of the Frank–Starling law in the heart. These data provide an explanation for slowed systolic function in the intact heart in response to RLC phosphorylation reduction.
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Affiliation(s)
- Christopher N Toepfer
- Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London, UK. .,Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, MD, USA.
| | - Timothy G West
- Structure & Motion Laboratory, Royal Veterinary College London, North Mymms, UK
| | - Michael A Ferenczi
- Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London, UK.,Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
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6
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Milani-Nejad N, Chung JH, Canan BD, Davis JP, Fedorov VV, Higgins RSD, Kilic A, Mohler PJ, Janssen PML. Insights into length-dependent regulation of cardiac cross-bridge cycling kinetics in human myocardium. Arch Biochem Biophys 2016; 601:48-55. [PMID: 26854725 PMCID: PMC4899103 DOI: 10.1016/j.abb.2016.02.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 01/29/2016] [Accepted: 02/02/2016] [Indexed: 11/16/2022]
Abstract
Cross-bridge cycling kinetics play an essential role in the heart's ability to contract and relax. The rate of tension redevelopment (ktr) slows down as a muscle length is increased in intact human myocardium. We set out to determine the effect of rapid length step changes and protein kinase A (PKA) and protein kinase C-βII (PKC-βII) inhibitors on the ktr in ultra-thin non-failing and failing human right ventricular trabeculae. After stabilizing the muscle either at L90 (90% of optimal length) or at Lopt (optimal length), we rapidly changed the length to either Lopt or L90 and measured ktr. We report that length-dependent changes in ktr occur very rapidly (in the order of seconds or faster) in both non-failing and failing muscles and that the length at which a muscle had been stabilized prior to the length change does not significantly affect ktr. In addition, at L90 and at Lopt, PKA and PKC-βII inhibitors did not significantly change ktr. Our results reveal that length-dependent regulation of cross-bridge cycling kinetics predominantly occurs rapidly and involves the intrinsic properties of the myofilament rather than post-translational modifications that are known to occur in the cardiac muscle as a result of a change in muscle/sarcomere length.
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Affiliation(s)
- Nima Milani-Nejad
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA; Medical Scientist Training Program and Biomedical Sciences Graduate Program, The Ohio State University Wexner Medical Center, USA
| | - Jae-Hoon Chung
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA; Medical Scientist Training Program and Biomedical Sciences Graduate Program, The Ohio State University Wexner Medical Center, USA
| | - Benjamin D Canan
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA
| | - Jonathan P Davis
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA
| | - Vadim V Fedorov
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA
| | - Robert S D Higgins
- Department of Surgery, Division of Cardiac Surgery, The Ohio State University Wexner Medical Center, USA
| | - Ahmet Kilic
- Department of Surgery, Division of Cardiac Surgery, The Ohio State University Wexner Medical Center, USA
| | - Peter J Mohler
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA; Department of Internal Medicine, The Ohio State University Wexner Medical Center, USA
| | - Paul M L Janssen
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, USA; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, USA; Department of Internal Medicine, The Ohio State University Wexner Medical Center, USA.
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7
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Cardiac myosin light chain is phosphorylated by Ca2+/calmodulin-dependent and -independent kinase activities. Proc Natl Acad Sci U S A 2016; 113:E3824-33. [PMID: 27325775 DOI: 10.1073/pnas.1600633113] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The well-known, muscle-specific smooth muscle myosin light chain kinase (MLCK) (smMLCK) and skeletal muscle MLCK (skMLCK) are dedicated protein kinases regulated by an autoregulatory segment C terminus of the catalytic core that blocks myosin regulatory light chain (RLC) binding and phosphorylation in the absence of Ca(2+)/calmodulin (CaM). Although it is known that a more recently discovered cardiac MLCK (cMLCK) is necessary for normal RLC phosphorylation in vivo and physiological cardiac performance, information on cMLCK biochemical properties are limited. We find that a fourth uncharacterized MLCK, MLCK4, is also expressed in cardiac muscle with high catalytic domain sequence similarity with other MLCKs but lacking an autoinhibitory segment. Its crystal structure shows the catalytic domain in its active conformation with a short C-terminal "pseudoregulatory helix" that cannot inhibit catalysis as a result of missing linker regions. MLCK4 has only Ca(2+)/CaM-independent activity with comparable Vmax and Km values for different RLCs. In contrast, the Vmax value of cMLCK is orders of magnitude lower than those of the other three MLCK family members, whereas its Km (RLC and ATP) and KCaM values are similar. In contrast to smMLCK and skMLCK, which lack activity in the absence of Ca(2+)/CaM, cMLCK has constitutive activity that is stimulated by Ca(2+)/CaM. Potential contributions of autoregulatory segment to cMLCK activity were analyzed with chimeras of skMLCK and cMLCK. The constitutive, low activity of cMLCK appears to be intrinsic to its catalytic core structure rather than an autoinhibitory segment. Thus, RLC phosphorylation in cardiac muscle may be regulated by two different protein kinases with distinct biochemical regulatory properties.
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8
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Yu H, Chakravorty S, Song W, Ferenczi MA. Phosphorylation of the regulatory light chain of myosin in striated muscle: methodological perspectives. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2016; 45:779-805. [PMID: 27084718 PMCID: PMC5101276 DOI: 10.1007/s00249-016-1128-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 03/10/2016] [Accepted: 03/23/2016] [Indexed: 12/18/2022]
Abstract
Phosphorylation of the regulatory light chain (RLC) of myosin modulates cellular functions such as muscle contraction, mitosis, and cytokinesis. Phosphorylation defects are implicated in a number of diseases. Here we focus on striated muscle where changes in RLC phosphorylation relate to diseases such as hypertrophic cardiomyopathy and muscular dystrophy, or age-related changes. RLC phosphorylation in smooth muscle and non-muscle cells are covered briefly where relevant. There is much scientific interest in controlling the phosphorylation levels of RLC in vivo and in vitro in order to understand its physiological function in striated muscles. A summary of available and emerging in vivo and in vitro methods is presented. The physiological role of RLC phosphorylation and novel pathways are discussed to highlight the differences between muscle types and to gain insights into disease processes.
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Affiliation(s)
- Haiyang Yu
- Lee Kong Chian School of Medicine, Nanyang Technological University, Experimental Medicine Building, Level 3, 59 Nanyang Drive, Singapore, 636921, Singapore
| | - Samya Chakravorty
- Lee Kong Chian School of Medicine, Nanyang Technological University, Experimental Medicine Building, Level 3, 59 Nanyang Drive, Singapore, 636921, Singapore
| | - Weihua Song
- Lee Kong Chian School of Medicine, Nanyang Technological University, Experimental Medicine Building, Level 3, 59 Nanyang Drive, Singapore, 636921, Singapore
| | - Michael A Ferenczi
- Lee Kong Chian School of Medicine, Nanyang Technological University, Experimental Medicine Building, Level 3, 59 Nanyang Drive, Singapore, 636921, Singapore.
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Karabina A, Kazmierczak K, Szczesna-Cordary D, Moore JR. Myosin regulatory light chain phosphorylation enhances cardiac β-myosin in vitro motility under load. Arch Biochem Biophys 2015; 580:14-21. [PMID: 26116789 PMCID: PMC4790447 DOI: 10.1016/j.abb.2015.06.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 05/27/2015] [Accepted: 06/21/2015] [Indexed: 12/15/2022]
Abstract
Familial hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy and myofibrillar disarray, and often results in sudden cardiac death. Two HCM mutations, N47K and R58Q, are located in the myosin regulatory light chain (RLC). The RLC mechanically stabilizes the myosin lever arm, which is crucial to myosin's ability to transmit contractile force. The N47K and R58Q mutations have previously been shown to reduce actin filament velocity under load, stemming from a more compliant lever arm (Greenberg, 2010). In contrast, RLC phosphorylation was shown to impart stiffness to the myosin lever arm (Greenberg, 2009). We hypothesized that phosphorylation of the mutant HCM-RLC may mitigate distinct mutation-induced structural and functional abnormalities. In vitro motility assays were utilized to investigate the effects of RLC phosphorylation on the HCM-RLC mutant phenotype in the presence of an α-actinin frictional load. Porcine cardiac β-myosin was depleted of its native RLC and reconstituted with mutant or wild-type human RLC in phosphorylated or non-phosphorylated form. Consistent with previous findings, in the presence of load, myosin bearing the HCM mutations reduced actin sliding velocity compared to WT resulting in 31-41% reductions in force production. Myosin containing phosphorylated RLC (WT or mutant) increased sliding velocity and also restored mutant myosin force production to near WT unphosphorylated values. These results point to RLC phosphorylation as a general mechanism to increase force production of the individual myosin motor and as a potential target to ameliorate the HCM-induced phenotype at the molecular level.
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Affiliation(s)
- Anastasia Karabina
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA, USA
| | - Katarzyna Kazmierczak
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Danuta Szczesna-Cordary
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Jeffrey R Moore
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA, USA.
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10
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Functions of myosin light chain-2 (MYL2) in cardiac muscle and disease. Gene 2015; 569:14-20. [PMID: 26074085 DOI: 10.1016/j.gene.2015.06.027] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Revised: 05/08/2015] [Accepted: 06/09/2015] [Indexed: 12/19/2022]
Abstract
Myosin light chain-2 (MYL2, also called MLC-2) is an ~19kDa sarcomeric protein that belongs to the EF-hand calcium binding protein superfamily and exists as three major isoforms encoded by three distinct genes in mammalian striated muscle. Each of the three different MLC-2 genes (MLC-2f; fast twitch skeletal isoform, MLC-2v; cardiac ventricular and slow twitch skeletal isoform, MLC-2a; cardiac atrial isoform) has a distinct developmental expression pattern in mammals. Genetic loss-of-function studies in mice demonstrated an essential role for cardiac isoforms of MLC-2, MLC-2v and MLC-2a, in cardiac contractile function during early embryogenesis. In the adult heart, MLC-2v function is regulated by phosphorylation, which displays a specific 1`expression pattern (high in epicardium and low in endocardium) across the heart. These data along with new data from computational models, genetic mouse models, and human studies have revealed a direct role for MLC-2v phosphorylation in cross-bridge cycling kinetics, calcium-dependent cardiac muscle contraction, cardiac torsion, cardiac function and various cardiac diseases. This review focuses on the regulatory functions of MLC-2 in the embryonic and adult heart, with an emphasis on phosphorylation-driven actions of MLC-2v in adult cardiac muscle, which provide new insights into mechanisms regulating myosin cycling kinetics and human cardiac diseases.
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11
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Muthu P, Liang J, Schmidt W, Moore JR, Szczesna-Cordary D. In vitro rescue study of a malignant familial hypertrophic cardiomyopathy phenotype by pseudo-phosphorylation of myosin regulatory light chain. Arch Biochem Biophys 2014; 552-553:29-39. [PMID: 24374283 PMCID: PMC4043912 DOI: 10.1016/j.abb.2013.12.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 12/02/2013] [Accepted: 12/16/2013] [Indexed: 11/18/2022]
Abstract
Pseudo-phosphorylation of cardiac myosin regulatory light chain (RLC) has never been examined as a rescue method to alleviate a cardiomyopathy phenotype brought about by a disease causing mutation in the myosin RLC. This study focuses on the aspartic acid to valine substitution (D166V) in the myosin RLC shown to be associated with a malignant phenotype of familial hypertrophic cardiomyopathy (FHC). The mutation has also been demonstrated to cause severe functional abnormalities in transgenic mice expressing D166V in the heart. To explore this novel rescue strategy, pseudo-phosphorylation of D166V was used to determine whether the D166V-induced detrimental phenotype could be brought back to the level of wild-type (WT) RLC. The S15D substitution at the phosphorylation site of RLC was inserted into the recombinant WT and D166V mutant to mimic constitutively phosphorylated RLC proteins. Non-phosphorylatable (S15A) constructs were used as controls. A multi-faceted approach was taken to determine the effect of pseudo-phosphorylation on the ability of myosin to generate force and motion. Using mutant reconstituted porcine cardiac muscle preparations, we showed an S15D-induced rescue of both the enzymatic and binding properties of D166V-myosin to actin. A significant increase in force production capacity was noted in the in vitro motility assays for S15D-D166V vs. D166V reconstituted myosin. A similar pseudo-phosphorylation induced effect was observed on the D166V-elicited abnormal Ca(2+) sensitivity of force in porcine papillary muscle strips reconstituted with phosphomimic recombinant RLCs. Results from this study demonstrate a novel in vitro rescue strategy that could be utilized in vivo to ameliorate a malignant cardiomyopathic phenotype. We show for the first time that pseudo-RLC phosphorylation can reverse the majority of the mutation-induced phenotypes highlighting the importance of RLC phosphorylation in combating cardiac disease.
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Affiliation(s)
- Priya Muthu
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Jingsheng Liang
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - William Schmidt
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118, USA
| | - Jeffrey R Moore
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118, USA
| | - Danuta Szczesna-Cordary
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
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12
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Sheikh F, Lyon RC, Chen J. Getting the skinny on thick filament regulation in cardiac muscle biology and disease. Trends Cardiovasc Med 2014; 24:133-41. [PMID: 23968570 PMCID: PMC3877703 DOI: 10.1016/j.tcm.2013.07.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 07/03/2013] [Accepted: 07/05/2013] [Indexed: 12/21/2022]
Abstract
Thin (actin) filament accessory proteins are thought to be the regulatory force for muscle contraction in cardiac muscle; however, compelling new evidence suggests that thick (myosin) filament regulatory proteins are emerging as having independent and important roles in regulating cardiac muscle contraction. Key to these new findings is a growing body of evidence that point to an influential and, more recently, direct role for ventricular myosin light chain-2 (MLC2v) phosphorylation in regulating cardiac muscle contraction, function, and disease. This includes the discovery and characterization of a cardiac-specific myosin light chain kinase capable of phosphorylating MLC2v as well as a myosin phosphatase that dephosphorylates MLC2v in the heart, which provides added mechanistic insights on MLC2v regulation within cardiac muscle. Here, we review evidence for an emerging and critical role for MLC2v phosphorylation in regulating cardiac myosin cycling kinetics, function, and disease, based on recent studies performed in genetic mouse models and humans. We further provide new perspectives on future avenues for targeting these pathways as therapies in alleviating cardiac disease.
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Affiliation(s)
- Farah Sheikh
- Department of Medicine (Cardiology Division), University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
| | - Robert C Lyon
- Department of Medicine (Cardiology Division), University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Ju Chen
- Department of Medicine (Cardiology Division), University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
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13
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Toepfer C, Caorsi V, Kampourakis T, Sikkel MB, West TG, Leung MC, Al-Saud SA, MacLeod KT, Lyon AR, Marston SB, Sellers JR, Ferenczi MA. Myosin regulatory light chain (RLC) phosphorylation change as a modulator of cardiac muscle contraction in disease. J Biol Chem 2013; 288:13446-54. [PMID: 23530050 PMCID: PMC3650382 DOI: 10.1074/jbc.m113.455444] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Revised: 03/21/2013] [Indexed: 01/26/2023] Open
Abstract
Understanding how cardiac myosin regulatory light chain (RLC) phosphorylation alters cardiac muscle mechanics is important because it is often altered in cardiac disease. The effect this protein phosphorylation has on muscle mechanics during a physiological range of shortening velocities, during which the heart generates power and performs work, has not been addressed. We have expressed and phosphorylated recombinant Rattus norvegicus left ventricular RLC. In vitro we have phosphorylated these recombinant species with cardiac myosin light chain kinase and zipper-interacting protein kinase. We compare rat permeabilized cardiac trabeculae, which have undergone exchange with differently phosphorylated RLC species. We were able to enrich trabecular RLC phosphorylation by 40% compared with controls and, in a separate series, lower RLC phosphorylation to 60% of control values. Compared with the trabeculae with a low level of RLC phosphorylation, RLC phosphorylation enrichment increased isometric force by more than 3-fold and peak power output by more than 7-fold and approximately doubled both maximum shortening speed and the shortening velocity that generated peak power. We augmented these measurements by observing increased RLC phosphorylation of human and rat HF samples from endocardial left ventricular homogenate. These results demonstrate the importance of increased RLC phosphorylation in the up-regulation of myocardial performance and suggest that reduced RLC phosphorylation is a key aspect of impaired contractile function in the diseased myocardium.
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Affiliation(s)
- Christopher Toepfer
- From the Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London SW7 2AZ, United Kingdom
- the Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, and
| | - Valentina Caorsi
- From the Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London SW7 2AZ, United Kingdom
| | - Thomas Kampourakis
- the Randall Division of Cell and Molecular Biophysics, Guy's Campus, King's College London, London SE1 1UL, United Kingdom
| | - Markus B. Sikkel
- the National Heart and Lung Institute, 4th Floor, Imperial Center for Translational and Experimental Medicine, Hammersmith Campus, Du Cane Road, London W12 0NN, United Kingdom
| | - Timothy G. West
- the Structure and Motion Laboratory, Royal Veterinary College London, North Mymms AL9 7TA, United Kingdom
| | - Man-Ching Leung
- the National Heart and Lung Institute, 4th Floor, Imperial Center for Translational and Experimental Medicine, Hammersmith Campus, Du Cane Road, London W12 0NN, United Kingdom
| | - Sara A. Al-Saud
- From the Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London SW7 2AZ, United Kingdom
| | - Kenneth T. MacLeod
- the National Heart and Lung Institute, 4th Floor, Imperial Center for Translational and Experimental Medicine, Hammersmith Campus, Du Cane Road, London W12 0NN, United Kingdom
| | - Alexander R. Lyon
- the National Heart and Lung Institute, 4th Floor, Imperial Center for Translational and Experimental Medicine, Hammersmith Campus, Du Cane Road, London W12 0NN, United Kingdom
- the Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London SW3 6MP, United Kingdom
| | - Steven B. Marston
- the National Heart and Lung Institute, 4th Floor, Imperial Center for Translational and Experimental Medicine, Hammersmith Campus, Du Cane Road, London W12 0NN, United Kingdom
| | - James R. Sellers
- the Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, and
| | - Michael A. Ferenczi
- From the Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London SW7 2AZ, United Kingdom
- the Lee Kong Chian School of Medicine, Nanyang Technological University, 637553 Singapore
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14
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Walker LA, Fullerton DA, Buttrick PM. Contractile protein phosphorylation predicts human heart disease phenotypes. Am J Physiol Heart Circ Physiol 2013; 304:H1644-50. [PMID: 23564307 DOI: 10.1152/ajpheart.00957.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Human heart failure has been associated with a low level of thin-filament protein phosphorylation and an increase in calcium sensitivity of contraction relative to both "control" human heart tissue and tissue from small animal models. However, diverse strategies of human tissue procurement and the reliance on tissue obtained from subjects with end-stage heart failure suggest this may be an incomplete characterization. Therefore, we evaluated cardiac left ventricular (LV) biopsy samples from patients with aortic stenosis undergoing valve replacement who presented either with LV hypertrophy and preserved systolic function (Hyp) or with LV dilation and reduced ejection fraction (Dil). In Hyp, total troponin I (TnI) phosphorylation was markedly increased and myosin light chain 2 (MLC2) phosphorylation was unchanged relative to a control group of patients with normal LV function. Conversely, in Dil, total TnI phosphorylation was significantly reduced compared with control subjects and MLC2 phosphorylation was increased. Site-specific analysis of TnI phosphorylation revealed phenotype-specific differences such that Hyp samples demonstrated significant increases in phosphorylation at serine 22/23 and Dil samples had significant decreases at serine 43. The ratio of phosphorylation at the two sites was biased toward serine 22/23 in Hyp and toward serine 43/45 in Dil. Western blot analysis showed that protein phosphatase-1 was reduced in Hyp and protein phosphatase-2 was reduced in Dil. These data suggest that posttranslational modifications of sarcomeric proteins, both singly and in combination, are stage specific. Defining these changes in progressive heart disease may provide important diagnostic and treatment information.
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Affiliation(s)
- Lori A Walker
- Division of Cardiology, Department of Medicine, University of Colorado Denver, Aurora, CO 80045, USA.
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15
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Sheikh F, Ouyang K, Campbell SG, Lyon RC, Chuang J, Fitzsimons D, Tangney J, Hidalgo CG, Chung CS, Cheng H, Dalton ND, Gu Y, Kasahara H, Ghassemian M, Omens JH, Peterson KL, Granzier HL, Moss RL, McCulloch AD, Chen J. Mouse and computational models link Mlc2v dephosphorylation to altered myosin kinetics in early cardiac disease. J Clin Invest 2012; 122:1209-21. [PMID: 22426213 DOI: 10.1172/jci61134] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 01/18/2012] [Indexed: 11/17/2022] Open
Abstract
Actin-myosin interactions provide the driving force underlying each heartbeat. The current view is that actin-bound regulatory proteins play a dominant role in the activation of calcium-dependent cardiac muscle contraction. In contrast, the relevance and nature of regulation by myosin regulatory proteins (for example, myosin light chain-2 [MLC2]) in cardiac muscle remain poorly understood. By integrating gene-targeted mouse and computational models, we have identified an indispensable role for ventricular Mlc2 (Mlc2v) phosphorylation in regulating cardiac muscle contraction. Cardiac myosin cycling kinetics, which directly control actin-myosin interactions, were directly affected, but surprisingly, Mlc2v phosphorylation also fed back to cooperatively influence calcium-dependent activation of the thin filament. Loss of these mechanisms produced early defects in the rate of cardiac muscle twitch relaxation and ventricular torsion. Strikingly, these defects preceded the left ventricular dysfunction of heart disease and failure in a mouse model with nonphosphorylatable Mlc2v. Thus, there is a direct and early role for Mlc2 phosphorylation in regulating actin-myosin interactions in striated muscle contraction, and dephosphorylation of Mlc2 or loss of these mechanisms can play a critical role in heart failure.
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Affiliation(s)
- Farah Sheikh
- Department of Medicine, UCSD, La Jolla, California 92093-0613C, USA.
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16
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Walker LA, Walker JS, Glazier A, Brown DR, Stenmark KR, Buttrick PM. Biochemical and myofilament responses of the right ventricle to severe pulmonary hypertension. Am J Physiol Heart Circ Physiol 2011; 301:H832-40. [PMID: 21622821 DOI: 10.1152/ajpheart.00249.2011] [Citation(s) in RCA: 21] [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
Right ventricular (RV) failure is one of the strongest predictors of mortality both in the presence of left ventricular decompensation and in the context of pulmonary vascular disease. Despite this, there is a limited understanding of the biochemical and mechanical characteristics of the pressure-overloaded RV at the level of the cardiac myocyte. To better understand this, we studied ventricular muscle obtained from neonatal calves that were subjected to hypobaric atmospheric conditions, which result in profound pulmonary hypertension. We found that RV pressure overload resulted in significant changes in the phosphorylation of key contractile proteins. Total phosphorylation of troponin I was decreased with pressure overload, predominantly reflecting changes at the putative PKA site at Ser(22/23). Similarly, both troponin T and myosin light chain 2 showed a significant decline in phosphorylation. Desmin was unchanged, and myosin-binding protein C (MyBP-C) phosphorylation was apparently increased. However, the apparent increase in MyBP-C phosphorylation was not due to phosphorylation but rather to an increase in MyBP-C total protein. Importantly, these findings were seen in all regions of the RV and were paralleled by reduced Ca(2+) sensitivity with preserved maximal Ca(2+) saturated developed force normalized to cross-sectional area in isolated skinned right ventricular myocyte fragments. No changes in total force or cooperativity were seen. Taken together, these results suggest that RV failure is mechanistically unique from left ventricular failure.
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Affiliation(s)
- Lori A Walker
- Department of Medicine, University of Colorado-Denver, Aurora, Colorado 80045, USA.
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17
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Neonatal asphyxia induces the nitration of cardiac myosin light chain 2 that is associated with cardiac systolic dysfunction. Shock 2011; 34:592-600. [PMID: 20386496 DOI: 10.1097/shk.0b013e3181e14f1d] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Hypoxia followed by reoxygenation (H-R) observed during perinatal asphyxia is a serious complication with high mortality and morbidity rates that may cause adverse cardiovascular effects in neonates. Our aim was to determine if oxidative stress related to H-R induces peroxynitrite-dependent modifications of the cardiac contractile protein, myosin regulatory light chain 2 (MLC2), and whether this is associated with development of cardiac systolic dysfunction. Twelve newborn piglets were acutely instrumented for hemodynamic monitoring and randomized to a control group ventilated with only atmospheric air or to the H-R study group exposed to alveolar normocapnic hypoxia followed by reoxygenation. Afterward, animals were euthanized, and the hearts were harvested for biochemical analyses. Systolic function as well as cardiac MLC2 levels decreased in H-R animals, whereas nitrates and nitrotyrosine levels increased. Negative correlations between nitrates, nitrotyrosine, and MLC2 levels were observed. Moreover, H-R induced nitration of two tyrosine residues within the MLC2 protein. Similarly, in vitro exposure of MLC2 to peroxynitrite resulted in the nitration of tyrosine, which increased the susceptibility of MLC2 to subsequent degradation by matrix metalloproteinase 2. Substitution of this tyrosine with phenylalanine prevented the matrix metalloproteinase 2-dependent degradation of MLC2. In addition, a large decrease in MLC2 phosphorylation caused by H-R was observed. Oxidative stress related to asphyxia induces nitration of cardiac MLC2 protein and thus increases its degradation. This and a large decrease in MLC2 phosphorylation contribute to the development of systolic dysfunction. Inhibition of MLC2 nitration and/or direct inhibition of its degradation by MMP-2 could be potential therapeutic targets aiming at reduction of myocardial damage during resuscitation of asphyxiated newborns.
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18
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Scruggs SB, Reisdorph R, Armstrong ML, Warren CM, Reisdorph N, Solaro RJ, Buttrick PM. A novel, in-solution separation of endogenous cardiac sarcomeric proteins and identification of distinct charged variants of regulatory light chain. Mol Cell Proteomics 2010; 9:1804-18. [PMID: 20445002 DOI: 10.1074/mcp.m110.000075] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The molecular conformation of the cardiac myosin motor is modulated by intermolecular interactions among the heavy chain, the light chains, myosin binding protein-C, and titin and is governed by post-translational modifications (PTMs). In-gel digestion followed by LC/MS/MS has classically been applied to identify cardiac sarcomeric PTMs; however, this approach is limited by protein size, pI, and difficulties in peptide extraction. We report a solution-based work flow for global separation of endogenous cardiac sarcomeric proteins with a focus on the regulatory light chain (RLC) in which specific sites of phosphorylation have been unclear. Subcellular fractionation followed by OFFGEL electrophoresis resulted in isolation of endogenous charge variants of sarcomeric proteins, including regulatory and essential light chains, myosin heavy chain, and myosin-binding protein-C of the thick filament. Further purification of RLC using reverse-phase HPLC separation and UV detection enriched for RLC PTMs at the intact protein level and provided a stoichiometric and quantitative assessment of endogenous RLC charge variants. Digestion and subsequent LC/MS/MS unequivocally identified that the endogenous charge variants of cardiac RLC focused in unique OFFGEL electrophoresis fractions were unphosphorylated (78.8%), singly phosphorylated (18.1%), and doubly phosphorylated (3.1%) RLC. The novel aspects of this study are that 1) milligram amounts of endogenous cardiac sarcomeric subproteome were focused with resolution comparable with two-dimensional electrophoresis, 2) separation and quantification of post-translationally modified variants were achieved at the intact protein level, 3) separation of intact high molecular weight thick filament proteins was achieved in solution, and 4) endogenous charge variants of RLC were separated; a novel doubly phosphorylated form was identified in mouse, and singly phosphorylated, singly deamidated, and deamidated/phosphorylated forms were identified and quantified in human non-failing and failing heart samples, thus demonstrating the clinical utility of the method.
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Affiliation(s)
- Sarah B Scruggs
- Department of Physiology and Biophysics, University of Illinois, Chicago, Illinois 60612, 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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de Waard MC, van der Velden J, Boontje NM, Dekkers DHW, van Haperen R, Kuster DWD, Lamers JMJ, de Crom R, Duncker DJ. Detrimental effect of combined exercise training and eNOS overexpression on cardiac function after myocardial infarction. Am J Physiol Heart Circ Physiol 2009; 296:H1513-23. [PMID: 19286956 DOI: 10.1152/ajpheart.00485.2008] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
It has been reported that exercise after myocardial infarction (MI) attenuates left ventricular (LV) pump dysfunction by normalization of myofilament function. This benefit could be due to an exercise-induced upregulation of endothelial nitric oxide synthase (eNOS) expression and activity. Consequently, we first tested the hypothesis that the effects of exercise after MI can be mimicked by elevated eNOS expression using transgenic mice with overexpression of human eNOS (eNOSTg). Both exercise and eNOSTg attenuated LV remodeling and dysfunction after MI in mice and improved cardiomyocyte maximal force development (F(max)). However, only exercise training restored myofilament Ca(2+)-sensitivity and sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA)2a protein levels and improved the first derivative of LV pressure at 30 mmHg. Conversely, only eNOSTg improved survival. In view of these partly complementary actions, we subsequently tested the hypothesis that combining exercise and eNOSTg would provide additional protection against LV remodeling and dysfunction after MI. Unexpectedly, the combination of exercise and eNOSTg abolished the beneficial effects on LV remodeling and dysfunction of either treatment alone. The latter was likely due to perturbations in Ca(2+) homeostasis, as myofilament F(max) actually increased despite marked reductions in the phosphorylation status of several myofilament proteins, whereas the exercise-induced increases in SERCA2a protein levels were lost in eNOSTg mice. Antioxidant treatment with N-acetylcysteine or supplementation of tetrahydrobiopterin and l-arginine prevented these detrimental effects on LV function while partly restoring the phosphorylation status of myofilament proteins and further enhancing myofilament F(max). In conclusion, the combination of exercise and elevated eNOS expression abolished the cardioprotective effects of either treatment alone after MI, which appeared to be, at least in part, the result of increased oxidative stress secondary to eNOS "uncoupling."
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Affiliation(s)
- Monique C de Waard
- Div. of Experimental Cardiology, Dept. of Cardiology, Thoraxcenter, Erasmus Univ. Medical Center, PO Box 2040, Rotterdam 3000 CA, The Netherlands
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21
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Chu L, Norota I, Endoh M. Differential inhibition by the Rho kinase inhibitor Y-27632 of the increases in contractility and Ca2+ transients induced by endothelin-1 in rabbit ventricular myocytes. Naunyn Schmiedebergs Arch Pharmacol 2005; 371:185-94. [PMID: 15900512 DOI: 10.1007/s00210-005-1032-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2004] [Accepted: 01/28/2005] [Indexed: 01/08/2023]
Abstract
The role of Rho kinase activation in the regulation of cardiac contractility and Ca(2+) signaling remains unclear, whereas its role in smooth muscle regulation has been well documented. To study the potential role of Rho kinase in the regulation of cardiac contractility and Ca(2+) transients induced by endothelin-1 (ET-1) and isoproterenol, we used the Rho kinase inhibitor Y-27632 in rabbit ventricular myocardium and myocytes loaded with indo-1/AM. Y-27632 (3-30 microM) inhibited significantly the baseline contractility and Ca(2+) transients. Furthermore, Y-27632 suppressed the increase in contractility and Ca(2+) transients induced by ET-1 in a concentration-dependent manner, when it was used in a concentration at which it did not affect the effects of isoproterenol via beta-adrenoceptors. In the presence of Y-27632, ET-1 increased cell shortening in the absence of an increase in Ca(2+) transients. This is an indication that the increase in myofilament Ca(2+) sensitivity induced by ET-1 is less susceptible to the inhibitory action of Y-27632. These findings imply that the Rho kinase activation may partially contribute to the ET-1-induced regulation of contractility, primarily due to an ET-1-induced increase in Ca(2+) transients in rabbit ventricular myocardium.
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Affiliation(s)
- Li Chu
- Department of Cardiovascular Pharmacology, Yamagata University School of Medicine, Yamagata 990-9585, Japan
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Olsson MC, Patel JR, Fitzsimons DP, Walker JW, Moss RL. Basal myosin light chain phosphorylation is a determinant of Ca2+ sensitivity of force and activation dependence of the kinetics of myocardial force development. Am J Physiol Heart Circ Physiol 2004; 287:H2712-8. [PMID: 15331360 DOI: 10.1152/ajpheart.01067.2003] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is generally recognized that ventricular myosin regulatory light chains (RLC) are approximately 40% phosphorylated under basal conditions, and there is little change in RLC phosphorylation with agonist stimulation of myocardium or altered stimulation frequency. To establish the functional consequences of basal RLC phosphorylation in the heart, we measured mechanical properties of rat skinned trabeculae in which approximately 7% or approximately 58% of total RLC was phosphorylated. The protocol for achieving approximately 7% phosphorylation of RLC involved isolating trabeculae in the presence of 2,3-butanedione monoxime (BDM) to dephosphorylate RLC from its baseline level. Subsequent phosphorylation to approximately 58% of total was achieved by incubating BDM-treated trabeculae in solution containing smooth muscle myosin light chain kinase, calmodulin, and Ca2+ (i.e., MLCK treatment). After MLCK treatment, Ca2+ sensitivity of force increased by 0.06 pCa units and maximum force increased by 5%. The rate constant of force development (ktr) increased as a function of Ca2+ concentration in the range between pCa 5.8 and pCa 4.5. When expressed versus pCa, the activation dependence of ktr appeared to be unaffected by MLCK treatment; however, when activation was expressed in terms of isometric force-generating capability (as a fraction of maximum), MLCK treatment slowed ktr at submaximal activations. These results suggest that basal phosphorylation of RLC plays a role in setting the kinetics of force development and Ca2+ sensitivity of force in cardiac muscle. Our results also argue that changes in RLC phosphorylation in the range examined here influence actin-myosin interaction kinetics differently in heart muscle than was previously reported for skeletal muscle.
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Affiliation(s)
- M Charlotte Olsson
- Dept. of Physiology, Univ. of Wisconsin Medical School, 1300 University Ave., Madison, WI 53706, USA
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Roopnarine O. Mechanical defects of muscle fibers with myosin light chain mutants that cause cardiomyopathy. Biophys J 2003; 84:2440-9. [PMID: 12668451 PMCID: PMC1302809 DOI: 10.1016/s0006-3495(03)75048-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Familial hypertrophic cardiomyopathy is a disease caused by single mutations in several sarcomeric proteins, including the human myosin ventricular regulatory light chain (vRLC). The effects of four of these mutations (A13T, F18L, E22K, and P95A) in vRLC on force generation were determined as a function of Ca(2+) concentration. The endogenous RLC was removed from skinned rabbit psoas muscle fibers, and replaced with either rat wildtype vRLC or recombinant rat vRLC (G13T, F18L, E22K, and P95A). Compared to fibers with wildtype rat vRLC, the E22K mutant increased Ca sensitivity of force generation, whereas the G13T and F18L mutants decreased the Ca sensitivity, and the P95A mutant had no significant effect. None of the RLC mutants affected the maximal tension (observed at saturating Ca(2+) concentrations), except for F18L, which decreased the maximal tension to 69 +/- 10% of the wildtype value. Of the mutant RLCs, only F18L decreased the cooperativity of activation of force generation. These results suggest that the primary cause of familial hypertrophic cardiomyopathy, in some cases, is perturbation in the Ca sensitivity of force generation, in which Ca-sensitizing or Ca-desensitizing effects can lead to similar disease phenotypes.
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Affiliation(s)
- Osha Roopnarine
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA.
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Nguyen TT, Hayes E, Mulieri LA, Leavitt BJ, ter Keurs HE, Alpert NR, Warshaw DM. Maximal actomyosin ATPase activity and in vitro myosin motility are unaltered in human mitral regurgitation heart failure. Circ Res 1996; 79:222-6. [PMID: 8755998 DOI: 10.1161/01.res.79.2.222] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Myofibrillar but not actomyosin ATPase is depressed in failing myocardium from patients with dilated cardiomyopathy. Since there is a similar depression of myofibrillar ATPase in mitral regurgitation myocardium, we investigated whether or not the hydrolytic and mechanical performances of myosin are altered by comparing the maximal actomyosin ATPase activity and the in vitro myosin motility of myocardial myosin from patients with mitral regurgitation heart failure with that of patients with normal ventricular function. The results show that there is no significant difference (P > .05) between nonfailing and failing values for either the maximal actomyosin ATPase activity (0.3 s-1.head-1) or the myosin motility (1 micron/s). These observations suggest that changes, other than in the myosin heavy chain, contribute to the altered myocardial performance in mitral regurgitation myocardium.
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Affiliation(s)
- T T Nguyen
- Department of Medicine and Medical Physiology, University of Calgary, Canada
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