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Stanczyk PJ, Seidel M, White J, Viero C, George CH, Zissimopoulos S, Lai FA. Association of cardiac myosin-binding protein-C with the ryanodine receptor channel - putative retrograde regulation? J Cell Sci 2018; 131:jcs.210443. [PMID: 29930088 PMCID: PMC6104826 DOI: 10.1242/jcs.210443] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 05/31/2018] [Indexed: 11/20/2022] Open
Abstract
The cardiac muscle ryanodine receptor-Ca2+ release channel (RyR2) constitutes the sarcoplasmic reticulum (SR) Ca2+ efflux mechanism that initiates myocyte contraction, while cardiac myosin-binding protein-C (cMyBP-C; also known as MYBPC3) mediates regulation of acto-myosin cross-bridge cycling. In this paper, we provide the first evidence for the presence of direct interaction between these two proteins, forming a RyR2-cMyBP-C complex. The C-terminus of cMyBP-C binds with the RyR2 N-terminus in mammalian cells and the interaction is not mediated by a fibronectin-like domain. Notably, we detected complex formation between both recombinant cMyBP-C and RyR2, as well as between the native proteins in cardiac tissue. Cellular Ca2+ dynamics in HEK293 cells is altered upon co-expression of cMyBP-C and RyR2, with lowered frequency of RyR2-mediated spontaneous Ca2+ oscillations, suggesting that cMyBP-C exerts a potential inhibitory effect on RyR2-dependent Ca2+ release. Discovery of a functional RyR2 association with cMyBP-C provides direct evidence for a putative mechanistic link between cytosolic soluble cMyBP-C and SR-mediated Ca2+ release, via RyR2. Importantly, this interaction may have clinical relevance to the observed cMyBP-C and RyR2 dysfunction in cardiac pathologies, such as hypertrophic cardiomyopathy.
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Affiliation(s)
- Paulina J Stanczyk
- Sir Geraint Evans Wales Heart Research Institute, Department of Cardiology, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.,School of Biosciences, Sir Martin Evans Building, College of Biomedical and Life Sciences, Cardiff University, Cardiff CF10 3AX, UK
| | - Monika Seidel
- Sir Geraint Evans Wales Heart Research Institute, Department of Cardiology, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.,Swansea University Medical School, Institute of Life Science, Swansea SA2 8PP, UK
| | - Judith White
- Sir Geraint Evans Wales Heart Research Institute, Department of Cardiology, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.,School of Biosciences, Sir Martin Evans Building, College of Biomedical and Life Sciences, Cardiff University, Cardiff CF10 3AX, UK
| | - Cedric Viero
- Sir Geraint Evans Wales Heart Research Institute, Department of Cardiology, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.,Institute of Pharmacology and Toxicology, Medical School, Saarland University, Homburg/Saar, Germany
| | - Christopher H George
- Sir Geraint Evans Wales Heart Research Institute, Department of Cardiology, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.,Swansea University Medical School, Institute of Life Science, Swansea SA2 8PP, UK
| | - Spyros Zissimopoulos
- Sir Geraint Evans Wales Heart Research Institute, Department of Cardiology, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK .,Swansea University Medical School, Institute of Life Science, Swansea SA2 8PP, UK
| | - F Anthony Lai
- Sir Geraint Evans Wales Heart Research Institute, Department of Cardiology, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK .,School of Biosciences, Sir Martin Evans Building, College of Biomedical and Life Sciences, Cardiff University, Cardiff CF10 3AX, UK.,College of Medicine, Member of QU Health, Qatar University, P.O. Box 2013, Doha, Qatar
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Cardiac myosin binding protein C regulates postnatal myocyte cytokinesis. Proc Natl Acad Sci U S A 2015; 112:9046-51. [PMID: 26153423 DOI: 10.1073/pnas.1511004112] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Homozygous cardiac myosin binding protein C-deficient (Mybpc(t/t)) mice develop dramatic cardiac dilation shortly after birth; heart size increases almost twofold. We have investigated the mechanism of cardiac enlargement in these hearts. Throughout embryogenesis myocytes undergo cell division while maintaining the capacity to pump blood by rapidly disassembling and reforming myofibrillar components of the sarcomere throughout cell cycle progression. Shortly after birth, myocyte cell division ceases. Cardiac MYBPC is a thick filament protein that regulates sarcomere organization and rigidity. We demonstrate that many Mybpc(t/t) myocytes undergo an additional round of cell division within 10 d postbirth compared with their wild-type counterparts, leading to increased numbers of mononuclear myocytes. Short-hairpin RNA knockdown of Mybpc3 mRNA in wild-type mice similarly extended the postnatal window of myocyte proliferation. However, adult Mybpc(t/t) myocytes are unable to fully regenerate the myocardium after injury. MYBPC has unexpected inhibitory functions during postnatal myocyte cytokinesis and cell cycle progression. We suggest that human patients with homozygous MYBPC3-null mutations develop dilated cardiomyopathy, coupled with myocyte hyperplasia (increased cell number), as observed in Mybpc(t/t) mice. Human patients, with heterozygous truncating MYBPC3 mutations, like mice with similar mutations, have hypertrophic cardiomyopathy. However, the mechanism leading to hypertrophic cardiomyopathy in heterozygous MYBPC3(+/-) individuals is myocyte hypertrophy (increased cell size), whereas the mechanism leading to cardiac dilation in homozygous Mybpc3(-/-) mice is primarily myocyte hyperplasia.
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Kapplinger JD, Landstrom AP, Bos JM, Salisbury BA, Callis TE, Ackerman MJ. Distinguishing hypertrophic cardiomyopathy-associated mutations from background genetic noise. J Cardiovasc Transl Res 2014; 7:347-61. [PMID: 24510615 DOI: 10.1007/s12265-014-9542-z] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 01/13/2014] [Indexed: 01/24/2023]
Abstract
Despite the significant progress that has been made in identifying disease-associated mutations, the utility of the hypertrophic cardiomyopathy (HCM) genetic test is limited by a lack of understanding of the background genetic variation inherent to these sarcomeric genes in seemingly healthy subjects. This study represents the first comprehensive analysis of genetic variation in 427 ostensibly healthy individuals for the HCM genetic test using the "gold standard" Sanger sequencing method validating the background rate identified in the publically available exomes. While mutations are clearly overrepresented in disease, a background rate as high as ∼5 % among healthy individuals prevents diagnostic certainty. To this end, we have identified a number of estimated predictive value-based associations including gene-specific, topology, and conservation methods generating an algorithm aiding in the probabilistic interpretation of an HCM genetic test.
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Affiliation(s)
- Jamie D Kapplinger
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA
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Decker RS, Nakamura S, Decker ML, Sausamuta M, Sinno S, Harris K, Klocke FJ, Kulikovskaya I, Winegrad S. The dynamic role of cardiac myosin binding protein-C during ischemia. J Mol Cell Cardiol 2012; 52:1145-54. [PMID: 22281395 DOI: 10.1016/j.yjmcc.2012.01.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 01/05/2012] [Accepted: 01/06/2012] [Indexed: 12/16/2022]
Abstract
Cardiac myosin binding protein C (cMyBP-C) is a myofibrillar protein important for normal myocardial contractility and stability. In mutated form it can cause cardiomyopathy and heart failure. cMyBP-C appears to have separate regions for different functions. Three phosphorylation sites near the N terminus modulate contractility by their effect on both the kinetics of contraction and the binding site of the N-terminus. The C terminal region binds to myosin rods and stabilizes thick filament structure. The aim of the study reported here was to test whether cMyBPC is important in producing the structural and functional changes that result from ischemia/reperfusion. In this study the sequential changes in cMyBP-C, contractility, and thick filament structure following dephosphorylation of cMyBP-C associated with ischemia and reperfusion have been studied in biopsied specimens from chronically instrumented dogs. One and two dimensional electrophoresis, electron microscopy and immunocytochemistry with multiple antibodies generated against different domains in cMyBP-C have been used to follow structural changes in cMyBP-C. Ischemia produced dephosphorylation of cMyBP-C. Subsequent reperfusion released the dephosphorylated cMyBP-C from myofibrils and activated proteolysis of the cytoplasmic cMyBP-C. This in turn leads to increased vulnerability of cMyBP-C to proteolysis and increased degradation of thick filaments. The state of cMyBP-C appears to be closely related to phosphorylation and dephosphorylation of serine 282. In the absence of the stabilizing action of cMyBP-C either as a consequence of genetic mutation or dephosphorylation, premature degradation of thick filaments occurs and is accompanied by persistent contractile dysfunction.
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Affiliation(s)
- Robert S Decker
- Feinberg Cardiovascular Research Institute, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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Bardswell SC, Cuello F, Rowland AJ, Sadayappan S, Robbins J, Gautel M, Walker JW, Kentish JC, Avkiran M. Distinct sarcomeric substrates are responsible for protein kinase D-mediated regulation of cardiac myofilament Ca2+ sensitivity and cross-bridge cycling. J Biol Chem 2010; 285:5674-82. [PMID: 20018870 PMCID: PMC2820795 DOI: 10.1074/jbc.m109.066456] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 12/16/2009] [Indexed: 01/02/2023] Open
Abstract
Protein kinase D (PKD), a serine/threonine kinase with emerging cardiovascular functions, phosphorylates cardiac troponin I (cTnI) at Ser(22)/Ser(23), reduces myofilament Ca(2+) sensitivity, and accelerates cross-bridge cycle kinetics. Whether PKD regulates cardiac myofilament function entirely through cTnI phosphorylation at Ser(22)/Ser(23) remains to be established. To determine the role of cTnI phosphorylation at Ser(22)/Ser(23) in PKD-mediated regulation of cardiac myofilament function, we used transgenic mice that express cTnI in which Ser(22)/Ser(23) are substituted by nonphosphorylatable Ala (cTnI-Ala(2)). In skinned myocardium from wild-type (WT) mice, PKD increased cTnI phosphorylation at Ser(22)/Ser(23) and decreased the Ca(2+) sensitivity of force. In contrast, PKD had no effect on the Ca(2+) sensitivity of force in myocardium from cTnI-Ala(2) mice, in which Ser(22)/Ser(23) were unavailable for phosphorylation. Surprisingly, PKD accelerated cross-bridge cycle kinetics similarly in myocardium from WT and cTnI-Ala(2) mice. Because cardiac myosin-binding protein C (cMyBP-C) phosphorylation underlies cAMP-dependent protein kinase (PKA)-mediated acceleration of cross-bridge cycle kinetics, we explored whether PKD phosphorylates cMyBP-C at its PKA sites, using recombinant C1C2 fragments with or without site-specific Ser/Ala substitutions. Kinase assays confirmed that PKA phosphorylates Ser(273), Ser(282), and Ser(302), and revealed that PKD phosphorylates only Ser(302). Furthermore, PKD phosphorylated Ser(302) selectively and to a similar extent in native cMyBP-C of skinned myocardium from WT and cTnI-Ala(2) mice, and this phosphorylation occurred throughout the C-zones of sarcomeric A-bands. In conclusion, PKD reduces myofilament Ca(2+) sensitivity through cTnI phosphorylation at Ser(22)/Ser(23) but accelerates cross-bridge cycle kinetics by a distinct mechanism. PKD phosphorylates cMyBP-C at Ser(302), which may mediate the latter effect.
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Affiliation(s)
- Sonya C. Bardswell
- From the Cardiovascular Division, King's College London, London SE1 7EH, United Kingdom
| | - Friederike Cuello
- From the Cardiovascular Division, King's College London, London SE1 7EH, United Kingdom
| | - Alexandra J. Rowland
- From the Cardiovascular Division, King's College London, London SE1 7EH, United Kingdom
| | - Sakthivel Sadayappan
- the Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, and
| | - Jeffrey Robbins
- the Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, and
| | - Mathias Gautel
- From the Cardiovascular Division, King's College London, London SE1 7EH, United Kingdom
| | - Jeffery W. Walker
- the Molecular Cardiovascular Research Program, University of Arizona, Tuscon, Arizona 85724
| | - Jonathan C. Kentish
- From the Cardiovascular Division, King's College London, London SE1 7EH, United Kingdom
| | - Metin Avkiran
- From the Cardiovascular Division, King's College London, London SE1 7EH, United Kingdom
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Decker RS, Rines AK, Nakamura S, Naik TJ, Wassertsrom JA, Ardehali H. Phosphorylation of contractile proteins in response to alpha- and beta-adrenergic stimulation in neonatal cardiomyocytes. Transl Res 2010; 155:27-34. [PMID: 20004359 PMCID: PMC3307141 DOI: 10.1016/j.trsl.2009.09.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Revised: 09/17/2009] [Accepted: 09/19/2009] [Indexed: 10/20/2022]
Abstract
alpha- and beta-Adrenergic receptor agonists induce an inotropic response in the adult heart by promoting the phosphorylation of several regulatory proteins, including myosin-binding protein C (MyBP-C), cardiac troponin I (cTnI), and phospholamban (PLB). However, the adrenergic-induced phosphorylation of these proteins has not been characterized in the developing heart. Accordingly, we evaluated MyBP-C, cTnI, and PLB phosphorylation in cultured neonatal rat cardiomyocytes (NRCMs) after alpha- and beta-receptor activation with phenylephrine and isoproterenol. alpha-Receptor stimulation increased, whereas beta-receptor activation reduced MyBP-C phosphorylation. Isoelectric-focusing experiments indicated that the amount of monophosphorylated MyBP-C was sensitive to alpha-adrenergic activation, but diphosphorylated and triphosphorylated MyBP-C levels were largely unaffected. The phosphorylation of cTnI and PLB was consistent with the mechanism observed in adult hearts: alpha- and beta-Receptor stimulation phosphorylated both proteins. For cTnI, the greatest difference associated with beta-receptor activation was observed in the diphosphorylated state, whereas alpha-receptor activation was associated with a marked increase in the tetraphosphorylated protein and absence of the unphosphorylated state. Despite these apparent changes in cTnI and PLB phosphorylation, beta-receptor activation failed to alter calcium transients in NRCMs. Collectively, these findings suggest that, unlike cTnI and PLB, MyBP-C and inotropy are not coupled to beta-adrenergic stimulation in NRCMs. Therefore, cTnI and PLB probably play a more central role in modulating contractile function in NRCMs in response to catecholamines than does MyBP-C, and MyBP-C may have a structural role in stabilizing thick filament assembly rather than influencing cross-bridge formation in developing hearts.
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Affiliation(s)
- Robert S Decker
- Feinberg Cardiovascular Research Institute, Northwestern University Medical Center, Chicago, Ill 60611, USA
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Cohen S, Brault JJ, Gygi SP, Glass DJ, Valenzuela DM, Gartner C, Latres E, Goldberg AL. During muscle atrophy, thick, but not thin, filament components are degraded by MuRF1-dependent ubiquitylation. ACTA ACUST UNITED AC 2009; 185:1083-95. [PMID: 19506036 PMCID: PMC2711608 DOI: 10.1083/jcb.200901052] [Citation(s) in RCA: 450] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Loss of myofibrillar proteins is a hallmark of atrophying muscle. Expression of muscle RING-finger 1 (MuRF1), a ubiquitin ligase, is markedly induced during atrophy, and MuRF1 deletion attenuates muscle wasting. We generated mice expressing a Ring-deletion mutant MuRF1, which binds but cannot ubiquitylate substrates. Mass spectrometry of the bound proteins in denervated muscle identified many myofibrillar components. Upon denervation or fasting, atrophying muscles show a loss of myosin-binding protein C (MyBP-C) and myosin light chains 1 and 2 (MyLC1 and MyLC2) from the myofibril, before any measurable decrease in myosin heavy chain (MyHC). Their selective loss requires MuRF1. MyHC is protected from ubiquitylation in myofibrils by associated proteins, but eventually undergoes MuRF1-dependent degradation. In contrast, MuRF1 ubiquitylates MyBP-C, MyLC1, and MyLC2, even in myofibrils. Because these proteins stabilize the thick filament, their selective ubiquitylation may facilitate thick filament disassembly. However, the thin filament components decreased by a mechanism not requiring MuRF1.
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Affiliation(s)
- Shenhav Cohen
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
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Nyland LR, Palmer BM, Chen Z, Maughan DW, Seidman CE, Seidman J, Kreplak L, Vigoreaux JO. Cardiac myosin binding protein-C is essential for thick-filament stability and flexural rigidity. Biophys J 2009; 96:3273-80. [PMID: 19383471 PMCID: PMC2718271 DOI: 10.1016/j.bpj.2008.12.3946] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Revised: 12/19/2008] [Accepted: 12/23/2008] [Indexed: 01/13/2023] Open
Abstract
Using atomic force microscopy, we examined the contribution of cardiac myosin binding protein-C (cMyBP-C) to thick-filament length and flexural rigidity. Native thick filaments were isolated from the hearts of transgenic mice bearing a truncation mutation of cMyBP-C (t/t) that results in no detectable cMyBP-C and from age-matched wild-type controls (+/+). Atomic force microscopy images of these filaments were evaluated with an automated analysis algorithm that identified filament position and shape. The t/t thick-filament length (1.48 +/- 0.02 microm) was significantly (P < 0.01) shorter than +/+ (1.56 +/- 0.02 microm). This 5%-shorter thick-filament length in the t/t was reflected in 4% significantly shorter sarcomere lengths of relaxed isolated cardiomyocytes of the t/t (1.97 +/- 0.01 microm) compared to +/+ (2.05 +/- 0.01 microm). To determine if cMyBP-C contributes to the mechanical properties of thick filaments, we used statistical polymer chain mechanics to calculate a per-filament-specific persistence length, an index of flexural rigidity directly proportional to Young's modulus. Thick-filament-specific persistence length in the t/t (373 +/- 62 microm) was significantly lower than in +/+ (639 +/- 101 microm). Accordingly, Young's modulus of t/t thick filaments was approximately 60% of +/+. These results provide what we consider a new understanding for the critical role of cMyBP-C in defining normal cardiac output by sustaining force and muscle stiffness.
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Affiliation(s)
- Lori R. Nyland
- Department of Biology, University of Vermont, Burlington, Vermont 05405
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont 05405
| | - Bradley M. Palmer
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont 05405
| | - Zengyi Chen
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont 05405
| | - David W. Maughan
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont 05405
| | - Christine E. Seidman
- Department of Genetics, Howard Hughes Medical Institute and Harvard Medical School, Boston, Massachusetts 02115
| | - J.G. Seidman
- Department of Genetics, Howard Hughes Medical Institute and Harvard Medical School, Boston, Massachusetts 02115
| | - Laurent Kreplak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Jim O. Vigoreaux
- Department of Biology, University of Vermont, Burlington, Vermont 05405
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont 05405
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van Dijk SJ, Dooijes D, dos Remedios C, Michels M, Lamers JMJ, Winegrad S, Schlossarek S, Carrier L, ten Cate FJ, Stienen GJM, van der Velden J. Cardiac myosin-binding protein C mutations and hypertrophic cardiomyopathy: haploinsufficiency, deranged phosphorylation, and cardiomyocyte dysfunction. Circulation 2009; 119:1473-83. [PMID: 19273718 DOI: 10.1161/circulationaha.108.838672] [Citation(s) in RCA: 241] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Mutations in the MYBPC3 gene, encoding cardiac myosin-binding protein C (cMyBP-C), are a frequent cause of familial hypertrophic cardiomyopathy. In the present study, we investigated whether protein composition and function of the sarcomere are altered in a homogeneous familial hypertrophic cardiomyopathy patient group with frameshift mutations in MYBPC3 (MYBPC3(mut)). METHODS AND RESULTS Comparisons were made between cardiac samples from MYBPC3 mutant carriers (c.2373dupG, n=7; c.2864_2865delCT, n=4) and nonfailing donors (n=13). Western blots with the use of antibodies directed against cMyBP-C did not reveal truncated cMyBP-C in MYBPC3(mut). Protein expression of cMyBP-C was significantly reduced in MYBPC3(mut) by 33+/-5%. Cardiac MyBP-C phosphorylation in MYBPC3(mut) samples was similar to the values in donor samples, whereas the phosphorylation status of cardiac troponin I was reduced by 84+/-5%, indicating divergent phosphorylation of the 2 main contractile target proteins of the beta-adrenergic pathway. Force measurements in mechanically isolated Triton-permeabilized cardiomyocytes demonstrated a decrease in maximal force per cross-sectional area of the myocytes in MYBPC3(mut) (20.2+/-2.7 kN/m(2)) compared with donor (34.5+/-1.1 kN/m(2)). Moreover, Ca(2+) sensitivity was higher in MYBPC3(mut) (pCa(50)=5.62+/-0.04) than in donor (pCa(50)=5.54+/-0.02), consistent with reduced cardiac troponin I phosphorylation. Treatment with exogenous protein kinase A, to mimic beta-adrenergic stimulation, did not correct reduced maximal force but abolished the initial difference in Ca(2+) sensitivity between MYBPC3(mut) (pCa(50)=5.46+/-0.03) and donor (pCa(50)=5.48+/-0.02). CONCLUSIONS Frameshift MYBPC3 mutations cause haploinsufficiency, deranged phosphorylation of contractile proteins, and reduced maximal force-generating capacity of cardiomyocytes. The enhanced Ca(2+) sensitivity in MYBPC3(mut) is due to hypophosphorylation of troponin I secondary to mutation-induced dysfunction.
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Affiliation(s)
- Sabine J van Dijk
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
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