Cardiac myosin binding protein C regulates postnatal myocyte cytokinesis

Homozygous cardiac myosin binding protein C-deficient (Mybpct/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 Mybpct/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 Mybpct/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 Mybpct/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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HSC70 is a chaperone for wild-type and mutant cardiac myosin binding protein C

JCI Insight ◽

10.1172/jci.insight.99319 ◽

2018 ◽

Vol 3 (11) ◽

Cited By ~ 10

Author(s):

Amelia A. Glazier ◽

Neha Hafeez ◽

Dattatreya Mellacheruvu ◽

Venkatesha Basrur ◽

Alexey I. Nesvizhskii ◽

...

Keyword(s):

Protein C ◽

Binding Protein ◽

Cardiac Myosin ◽

Wild Type ◽

Myosin Binding Protein ◽

Myosin Binding Protein C ◽

Myosin Binding

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Phosphomimetic cardiac myosin-binding protein C partially rescues a cardiomyopathy phenotype in murine engineered heart tissue

Scientific Reports ◽

10.1038/s41598-019-54665-2 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 5

Author(s):

Alexander Dutsch ◽

Paul J. M. Wijnker ◽

Saskia Schlossarek ◽

Felix W. Friedrich ◽

Elisabeth Krämer ◽

...

Keyword(s):

Gene Transfer ◽

Protein C ◽

Binding Protein ◽

Heart Tissue ◽

Cardiac Myosin ◽

Wild Type ◽

Myosin Binding Protein ◽

Myosin Binding Protein C ◽

Myosin Binding

AbstractPhosphorylation of cardiac myosin-binding protein C (cMyBP-C), encoded by MYBPC3, increases the availability of myosin heads for interaction with actin thus enhancing contraction. cMyBP-C phosphorylation level is lower in septal myectomies of patients with hypertrophic cardiomyopathy (HCM) than in non-failing hearts. Here we compared the effect of phosphomimetic (D282) and wild-type (S282) cMyBP-C gene transfer on the HCM phenotype of engineered heart tissues (EHTs) generated from a mouse model carrying a Mybpc3 mutation (KI). KI EHTs showed lower levels of mutant Mybpc3 mRNA and protein, and altered gene expression compared with wild-type (WT) EHTs. Furthermore, KI EHTs exhibited faster spontaneous contractions and higher maximal force and sensitivity to external [Ca2+] under pacing. Adeno-associated virus-mediated gene transfer of D282 and S282 similarly restored Mybpc3 mRNA and protein levels and suppressed mutant Mybpc3 transcripts. Moreover, both exogenous cMyBP-C proteins were properly incorporated in the sarcomere. KI EHTs hypercontractility was similarly prevented by both treatments, but S282 had a stronger effect than D282 to normalize the force-Ca2+-relationship and the expression of dysregulated genes. These findings in an in vitro model indicate that S282 is a better choice than D282 to restore the HCM EHT phenotype. To which extent the results apply to human HCM remains to be seen.

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Impaired contractile function due to decreased cardiac myosin binding protein C content in the sarcomere

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00929.2012 ◽

2013 ◽

Vol 305 (1) ◽

pp. H52-H65 ◽

Cited By ~ 29

Author(s):

Y. Cheng ◽

X. Wan ◽

T. A. McElfresh ◽

X. Chen ◽

K. S. Gresham ◽

...

Keyword(s):

Cardiac Function ◽

Protein C ◽

Binding Protein ◽

Left Ventricular ◽

Cardiac Myosin ◽

Wild Type ◽

Cross Bridge ◽

Myosin Binding Protein ◽

Myosin Binding Protein C ◽

Myosin Binding

Mutations in cardiac myosin binding protein C (MyBP-C) are a common cause of familial hypertrophic cardiomyopathy (FHC). The majority of MyBP-C mutations are expected to reduce MyBP-C expression; however, the consequences of MyBP-C deficiency on the regulation of myofilament function, Ca2+ homeostasis, and in vivo cardiac function are unknown. To elucidate the effects of decreased MyBP-C expression on cardiac function, we employed MyBP-C heterozygous null (MyBP-C+/−) mice presenting decreases in MyBP-C expression (32%) similar to those of FHC patients carrying MyBP-C mutations. The levels of MyBP-C phosphorylation were reduced 53% in MyBP-C+/− hearts compared with wild-type hearts. Skinned myocardium isolated from MyBP-C+/− hearts displayed decreased cross-bridge stiffness at half-maximal Ca2+ activations, increased steady-state force generation, and accelerated rates of cross-bridge recruitment at low Ca2+ activations (<15% and <25% of maximum, respectively). Protein kinase A treatment abolished basal differences in rates of cross-bridge recruitment between MyBP-C+/− and wild-type myocardium. Intact ventricular myocytes from MyBP-C+/− hearts displayed abnormal sarcomere shortening but unchanged Ca2+ transient kinetics. Despite a lack of left ventricular hypertrophy, MyBP-C+/− hearts exhibited elevated end-diastolic pressure and decreased peak rate of LV pressure rise, which was normalized following dobutamine infusion. Furthermore, electrocardiogram recordings in conscious MyBP-C+/− mice revealed prolonged QRS and QT intervals, which are known risk factors for cardiac arrhythmia. Collectively, our data show that reduced MyBP-C expression and phosphorylation in the sarcomere result in myofilament dysfunction, contributing to contractile dysfunction that precedes compensatory adaptations in Ca2+ handling, and chamber remodeling. Perturbations in mechanical and electrical activity in MyBP-C+/− mice could increase their susceptibility to cardiac dysfunction and arrhythmia.

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Abstract 021: Extended Proliferation Capacity of Cardiomyocytes is Insufficient to Complete Cardiac Regeneration in Mice with a Mutation of Cardiac Myosin Binding Protein C

Circulation Research ◽

10.1161/res.113.suppl_1.a021 ◽

2013 ◽

Vol 113 (suppl_1) ◽

Author(s):

Gregory M Fomovsky ◽

Joseph B Gannon ◽

Kimberly K Schaefer ◽

Jianming Jiang ◽

Hiroko Wakimoto ◽

...

Keyword(s):

Cell Cycle ◽

Protein C ◽

Binding Protein ◽

Cardiac Regeneration ◽

Brdu Incorporation ◽

Cardiac Myosin ◽

Proliferation Capacity ◽

Myosin Binding Protein ◽

Myosin Binding Protein C ◽

Myosin Binding

Introduction: Adult mammalian cardiac regeneration rate is inadequate to compensate for the loss of myocardium following injury. One-day old (P1) mice fully regenerate myocardium after ventricular apex resection by division of cardiomyocytes (CMs). This regeneration ability is lost by P7. While CMs of a P1 mouse are mostly mononuclear, CMs withdraw from cell cycle and become mostly binuclear in the first post-natal week. CMs in mice with a mutation of a sarcomeric cardiac myosin-binding protein C (MyBP-C t/t ) have an extended proliferating capacity. In MyBP-C t/t mice, there are more CMs per ventricle and a significant number of CMs remain mononuclear compared to WT. Hypothesis: The loss of regeneration potential during the first post-natal week in WT mice is a result of rigid sarcomeric structure of maturing CMs, and a mutation of sarcomeric MyBP-C would extend the regenerative capacity of CMs beyond P1. Methods: We performed apical resections on P10 MyBP-C t/t and WT mice with sham-operated controls (n=61 of 118 survived surgery). For the resection surgery, neonates were anesthetized on ice, causing transient sedation, apnea and asystole. We assessed cardiac regeneration over two weeks by measuring cell cycle activity: Ki67 and pH3 expressions, and BrdU incorporation. Results: All cell cycle activity markers in MyBP-C t/t CMs were significantly higher than in WT. At 7 days-post resection (dpr) the number of BrdU-positive CM nuclei per 40X field was (mean±SD): 1.8±1.2 in MyBP-C t/t resections (n=4), 0.7±0.3 in MyBP-C t/t shams (n=5), 0.3±0.3 in WT resections (n=3), and 0.2±0.2 in WT shams (n=3). However, an increase in cell cycle activity in MyBP-C t/t resected hearts was not significant compared to MyBP-C t/t sham controls. Interestingly, using VonKossa silver staining, we observed pronounced dystrophic calcifications due to CM necrosis in MyBP-C t/t resected hearts only. The calcifications filled the resected area and were positive for cardiac troponin and proliferation markers as early as 3dpr, suggesting that proliferating CMs underwent necrosis and aborted regeneration. Conclusion: An extended proliferation capacity of MyBP-C t/t CMs beyond the first post-natal week is insufficient for complete cardiac regeneration following apical resection.

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Biological variation of cardiac myosin-binding protein C in healthy individuals

Clinical Chemistry and Laboratory Medicine (CCLM) ◽

10.1515/cclm-2021-0306 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Bashir Alaour ◽

Torbjørn Omland ◽

Janniche Torsvik ◽

Thomas E. Kaier ◽

Marit S. Sylte ◽

...

Keyword(s):

Risk Stratification ◽

Protein C ◽

Myocardial Injury ◽

Binding Protein ◽

Biological Variation ◽

Cardiac Myosin ◽

Analytical Quality ◽

Myosin Binding Protein ◽

Myosin Binding Protein C ◽

Myosin Binding

Abstract Objectives Cardiac myosin-binding protein C (cMyC) is a novel biomarker of myocardial injury, with a promising role in the triage and risk stratification of patients presenting with acute cardiac disease. In this study, we assess the weekly biological variation of cMyC, to examine its potential in monitoring chronic myocardial injury, and to suggest analytical quality specification for routine use of the test in clinical practice. Methods Thirty healthy volunteers were included. Non-fasting samples were obtained once a week for ten consecutive weeks. Samples were tested in duplicate on the Erenna® platform by EMD Millipore Corporation. Outlying measurements and subjects were identified and excluded systematically, and homogeneity of analytical and within-subject variances was achieved before calculating the biological variability (CVI and CVG), reference change values (RCV) and index of individuality (II). Results Mean age was 38 (range, 21–64) years, and 16 participants were women (53%). The biological variation, RCV and II with 95% confidence interval (CI) were: CVA (%) 19.5 (17.8–21.6), CVI (%) 17.8 (14.8–21.0), CVG (%) 66.9 (50.4–109.9), RCV (%) 106.7 (96.6–120.1)/−51.6 (−54.6 to −49.1) and II 0.42 (0.29–0.56). There was a trend for women to have lower CVG. The calculated RCVs were comparable between genders. Conclusions cMyC exhibits acceptable RCV and low II suggesting that it could be suitable for disease monitoring, risk stratification and prognostication if measured serially. Analytical quality specifications based on biological variation are similar to those for cardiac troponin and should be achievable at clinically relevant concentrations.

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Cardiac myosin‐binding protein C as a candidate biomarker in heart failure: rational but not revolutionary

European Journal of Heart Failure ◽

10.1002/ejhf.2126 ◽

2021 ◽

Author(s):

A. Mark Richards

Keyword(s):

Heart Failure ◽

Protein C ◽

Binding Protein ◽

Cardiac Myosin ◽

Myosin Binding Protein ◽

Myosin Binding Protein C ◽

Myosin Binding

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Cardiac Myosin-Binding Protein C Modulates the Tuning of the Molecular Motor in the Heart

Biophysical Journal ◽

10.1529/biophysj.107.127787 ◽

2008 ◽

Vol 95 (2) ◽

pp. 720-728 ◽

Cited By ~ 21

Author(s):

Yves Lecarpentier ◽

Nicolas Vignier ◽

Patricia Oliviero ◽

Aziz Guellich ◽

Lucie Carrier ◽

...

Keyword(s):

Protein C ◽

Molecular Motor ◽

Binding Protein ◽

Cardiac Myosin ◽

Myosin Binding Protein ◽

Myosin Binding Protein C ◽

Myosin Binding

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Phosphorylation of cardiac myosin binding protein C releases myosin heads from the surface of cardiac thick filaments

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1614020114 ◽

2017 ◽

Vol 114 (8) ◽

pp. E1355-E1364 ◽

Cited By ~ 35

Author(s):

Robert W. Kensler ◽

Roger Craig ◽

Richard L. Moss

Keyword(s):

Protein C ◽

Structural Changes ◽

Binding Protein ◽

Cardiac Contraction ◽

Cardiac Myosin ◽

Cross Bridge ◽

Myosin Binding Protein ◽

Myosin Binding Protein C ◽

Thick Filaments ◽

Myosin Binding

Cardiac myosin binding protein C (cMyBP-C) has a key regulatory role in cardiac contraction, but the mechanism by which changes in phosphorylation of cMyBP-C accelerate cross-bridge kinetics remains unknown. In this study, we isolated thick filaments from the hearts of mice in which the three serine residues (Ser273, Ser282, and Ser302) that are phosphorylated by protein kinase A in the m-domain of cMyBP-C were replaced by either alanine or aspartic acid, mimicking the fully nonphosphorylated and the fully phosphorylated state of cMyBP-C, respectively. We found that thick filaments from the cMyBP-C phospho-deficient hearts had highly ordered cross-bridge arrays, whereas the filaments from the cMyBP-C phospho-mimetic hearts showed a strong tendency toward disorder. Our results support the hypothesis that dephosphorylation of cMyBP-C promotes or stabilizes the relaxed/superrelaxed quasi-helical ordering of the myosin heads on the filament surface, whereas phosphorylation weakens this stabilization and binding of the heads to the backbone. Such structural changes would modulate the probability of myosin binding to actin and could help explain the acceleration of cross-bridge interactions with actin when cMyBP-C is phosphorylated because of, for example, activation of β1-adrenergic receptors in myocardium.

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