scholarly journals Sarcomeric protein modification during adrenergic stress enhances cross-bridge kinetics and cardiac output

2017 ◽  
Vol 122 (3) ◽  
pp. 520-530 ◽  
Author(s):  
Kenneth S. Gresham ◽  
Ranganath Mamidi ◽  
Jiayang Li ◽  
Hyerin Kwak ◽  
Julian E. Stelzer
Keyword(s):  
Cardiac Output ◽  
Posttranslational Modifications ◽  
Troponin I ◽  
Ventricular Contractility ◽  
Protein Modifications ◽  
Sarcomeric Protein ◽  
Cross Bridge ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Pressure Development

Molecular adaptations to chronic neurohormonal stress, including sarcomeric protein cleavage and phosphorylation, provide a mechanism to increase ventricular contractility and enhance cardiac output, yet the link between sarcomeric protein modifications and changes in myocardial function remains unclear. To examine the effects of neurohormonal stress on posttranslational modifications of sarcomeric proteins, mice were administered combined α- and β-adrenergic receptor agonists (isoproterenol and phenylephrine, IPE) for 14 days using implantable osmotic pumps. In addition to significant cardiac hypertrophy and increased maximal ventricular pressure, IPE treatment accelerated pressure development and relaxation (74% increase in dP/d tmax and 14% decrease in τ), resulting in a 52% increase in cardiac output compared with saline (SAL)-treated mice. Accelerated pressure development was maintained when accounting for changes in heart rate and preload, suggesting that myocardial adaptations contribute to enhanced ventricular contractility. Ventricular myocardium isolated from IPE-treated mice displayed a significant reduction in troponin I (TnI) and myosin-binding protein C (MyBP-C) expression and a concomitant increase in the phosphorylation levels of the remaining TnI and MyBP-C protein compared with myocardium isolated from saline-treated control mice. Skinned myocardium isolated from IPE-treated mice displayed a significant acceleration in the rate of cross-bridge (XB) detachment (46% increase) and an enhanced magnitude of XB recruitment (43% increase) at submaximal Ca2+ activation compared with SAL-treated mice but unaltered myofilament Ca2+ sensitivity of force generation. These findings demonstrate that sarcomeric protein modifications during neurohormonal stress are molecular adaptations that enhance in vivo ventricular contractility through accelerated XB kinetics to increase cardiac output. NEW & NOTEWORTHY Posttranslational modifications to sarcomeric regulatory proteins provide a mechanism to modulate cardiac function in response to stress. In this study, we demonstrate that neurohormonal stress produces modifications to myosin-binding protein C and troponin I, including a reduction in protein expression within the sarcomere and increased phosphorylation of the remaining protein, which serve to enhance cross-bridge kinetics and increase cardiac output. These findings highlight the importance of sarcomeric regulatory protein modifications in modulating ventricular function during cardiac stress.

scholarly journals The Interplay between S-glutathionylation and Phosphorylation of Cardiac Troponin I and Myosin Binding Protein C in End-Stage Human Failing Hearts

Antioxidants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1134
Author(s):  
Heidi Budde ◽  
Roua Hassoun ◽  
Melina Tangos ◽  
Saltanat Zhazykbayeva ◽  
Melissa Herwig ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Protein C ◽  
Troponin I ◽  
Reduced Glutathione ◽  
Binding Protein ◽  
Enzyme Treatment ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Myosin Binding ◽  
End Stage

Oxidative stress is defined as an imbalance between the antioxidant defense system and the production of reactive oxygen species (ROS). At low levels, ROS are involved in the regulation of redox signaling for cell protection. However, upon chronical increase in oxidative stress, cell damage occurs, due to protein, DNA and lipid oxidation. Here, we investigated the oxidative modifications of myofilament proteins, and their role in modulating cardiomyocyte function in end-stage human failing hearts. We found altered maximum Ca2+-activated tension and Ca2+ sensitivity of force production of skinned single cardiomyocytes in end-stage human failing hearts compared to non-failing hearts, which was corrected upon treatment with reduced glutathione enzyme. This was accompanied by the increased oxidation of troponin I and myosin binding protein C, and decreased levels of protein kinases A (PKA)- and C (PKC)-mediated phosphorylation of both proteins. The Ca2+ sensitivity and maximal tension correlated strongly with the myofilament oxidation levels, hypo-phosphorylation, and oxidative stress parameters that were measured in all the samples. Furthermore, we detected elevated titin-based myocardial stiffness in HF myocytes, which was reversed by PKA and reduced glutathione enzyme treatment. Finally, many oxidative stress and inflammation parameters were significantly elevated in failing hearts compared to non-failing hearts, and corrected upon treatment with the anti-oxidant GSH enzyme. Here, we provide evidence that the altered mechanical properties of failing human cardiomyocytes are partially due to phosphorylation, S-glutathionylation, and the interplay between the two post-translational modifications, which contribute to the development of heart failure.

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

2017 ◽  
Vol 114 (8) ◽  
pp. E1355-E1364 ◽  
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.

Abstract P338: Myopeptide Improves Contractile Mechanics In A Mouse Model Of Heart Failure Expressing Phosphoablated Cardiac Myosin Binding Protein-C

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Rohit Singh ◽  
Sakthivel Sadayappan
Keyword(s):  
Heart Failure ◽  
Mouse Model ◽  
Protein C ◽  
Cardiac Myosin ◽  
Bridge Formation ◽  
Cross Bridge ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Myosin Binding ◽  
Cross Bridges

Rationale: Normal heart function depends on cardiac myosin binding protein-C (cMyBP-C) phosphorylation. Its decrease is associated with heart failure (HF) by inhibiting actomyosin interactions. In absence of cMyBP-C phosphorylation, the protein is bound to myosin S2, but released when phosphorylated, allowing myosin to form cross-bridges with actin. Challenging cMyBP-C/myosin S2 interaction by myopeptide (the first 126 amino acids of myosin S2) could promote actomyosin interaction in vitro , but its ability to improve contractility in HF remains untested. Objective: To test contractile function in skinned papillary fibers of a cMyBP-C dephosphorylated mouse model using myopeptide. Methods and Results: To mimic constitutive phosphoablation, a knock-in mouse model was established to express cMyBP-C in which serines 273, 282 and 302 were mutated to alanine (cMyBP-C AAA ). Western blotting revealed 50% and 100% of cMyBP-C AAA in het and homo mouse hearts, respectively. Echocardiography showed a decreased percentage of ejection fraction (28%, p<0.01) and fractional shortening (30%, p< 0.05) in both het and homo cMyBP-C AAA mice at 3 months of age, compared to knock-in negative controls. These mice also developed diastolic dysfunction with elevated ratio of E/A and E/e’ waves. Next, pCa-force measurements using skinned papillary fibers determined that maximal force (F max ) and rate of cross-bridge formation ( k tr ) were decreased in the cMyBP-C AAA groups, compared to the control. However, administration of dose-dependent myopeptide increased F max and k tr in wild-type and cMyBP-C AAA permeabilized skinned papillary fibers without affecting myofilament Ca 2+ sensitivity. Conclusions: Myopeptide can increase contractile force and rate of cross-bridge formation by releasing cMyBP-C/myosin S2 and promoting actomyosin formation of cross-bridges, thus validating its therapeutic potential.

scholarly journals Protein kinase A–induced myofilament desensitization to Ca2+ as a result of phosphorylation of cardiac myosin–binding protein C

2010 ◽  
Vol 136 (6) ◽  
pp. 615-627 ◽  
Author(s):  
Peter P. Chen ◽  
Jitandrakumar R. Patel ◽  
Inna N. Rybakova ◽  
Jeffery W. Walker ◽  
Richard L. Moss
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Protein C ◽  
Binding Protein ◽  
Cardiac Myosin ◽  
Cross Bridge ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Myosin Binding ◽  
Kinase A

In skinned myocardium, cyclic AMP–dependent protein kinase A (PKA)-catalyzed phosphorylation of cardiac myosin–binding protein C (cMyBP-C) and cardiac troponin I (cTnI) is associated with a reduction in the Ca2+ responsiveness of myofilaments and an acceleration in the kinetics of cross-bridge cycling, although the respective contribution of these two proteins remains controversial. To further examine the relative roles that cTnI and cMyBP-C phosphorylation play in altering myocardial function, we determined the Ca2+ sensitivity of force (pCa50) and the activation dependence of the rate of force redevelopment (ktr) in control and PKA-treated mouse myocardium (isolated in the presence of 2,3-butanedione monoxime) expressing: (a) phosphorylatable cTnI and cMyBP-C (wild type [WT]), (b) phosphorylatable cTnI on a cMyBP-C–null background (cMyBP-C−/−), (c) nonphosphorylatable cTnI with serines23/24/43/45 and threonine144 mutated to alanines (cTnIAla5), and (d) nonphosphorylatable cTnI on a cMyBP-C–null background (cTnIAla5/cMyBP-C−/−). Here, PKA treatment decreased pCa50 in WT, cTnIAla5, and cMyBP-C−/− myocardium by 0.13, 0.08, and 0.09 pCa units, respectively, but had no effect in cTnIAla5/cMyBP-C−/− myocardium. In WT and cTnIAla5 myocardium, PKA treatment also increased ktr at submaximal levels of activation; however, PKA treatment did not have an effect on ktr in cMyBP-C−/− or cTnIAla5/cMyBP-C−/− myocardium. In addition, reconstitution of cTnIAla5/cMyBP-C−/− myocardium with recombinant cMyBP-C restored the effects of PKA treatment on pCa50 and ktr reported in cTnIAla5 myocardium. Collectively, these results indicate that the attenuation in myofilament force response to PKA occurs as a result of both cTnI and cMyBP-C phosphorylation, and that the reduction in pCa50 mediated by cMyBP-C phosphorylation most likely arises from an accelerated cross-bridge cycling kinetics partly as a result of an increased rate constant of cross-bridge detachment.

scholarly journals Roles of phosphorylation of myosin binding protein-C and troponin I in mouse cardiac muscle twitch dynamics

2004 ◽  
Vol 558 (3) ◽  
pp. 927-941 ◽  
Author(s):  
Carl W. Tong ◽  
Robert D. Gaffin ◽  
David C. Zawieja ◽  
Mariappan Muthuchamy
Keyword(s):  
Cardiac Muscle ◽  
Protein C ◽  
Troponin I ◽  
Binding Protein ◽  
Muscle Twitch ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Myosin Binding

scholarly journals Cardiac Myosin-binding Protein C and Troponin-I Phosphorylation Independently Modulate Myofilament Length-dependent Activation

2015 ◽  
Vol 290 (49) ◽  
pp. 29241-29249 ◽  
Author(s):  
Mohit Kumar ◽  
Suresh Govindan ◽  
Mengjie Zhang ◽  
Ramzi J. Khairallah ◽  
Jody L. Martin ◽  
...  
Keyword(s):  
Protein C ◽  
Troponin I ◽  
Binding Protein ◽  
Cardiac Myosin ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Myosin Binding ◽  
Length Dependent Activation

Abstract 231: Cardiac Myosin Binding Protein C Couples Cross-Bridge Cycling to Calcium Transients to Provide Normal Cardiac Function

2012 ◽  
Vol 111 (suppl_1) ◽  
Author(s):  
Yang Liu ◽  
Mahamed Abdalla ◽  
Himakarnika Alluri ◽  
Daniel Jupiter ◽  
Shannon Glaser ◽  
...  
Keyword(s):  
Body Weight ◽  
Cardiac Function ◽  
Protein C ◽  
Calcium Transients ◽  
Cardiac Myosin ◽  
Cross Bridge ◽  
Myosin Binding Protein ◽  
Myosin Binding Protein C ◽  
Myosin Binding ◽  
Normal Cardiac Function

A 40-year old American has a 20% chance of developing heart failure (HF) in his/her lifetime. Although cross-bridge cycling forms the basis for contraction and relaxation of the heart, mechanisms that modulate cross-bridge cycling are not completely understood, nor are the alterations in these processes in HF. Cardiac myosin binding protein-C (MyBPC3) is a component of heart muscle that is believed to regulate cross-bridge cycling kinetics. We hypothesize that MyBPC3 tunes cross-bridge cycling to the [Ca2+]i transient to produce normal cardiac function, which we tested using our MyBPC3 knockout (KO) mouse. Echocardiography showed that MyBPC3(KO) hearts exhibited abbreviated aortic ejection durations (AED) and AED/(period between heart beats) ratio compared to WT. MyBPC3(KO) hearts also had smaller velocity-time integrals which indicate smaller stroke volumes as a result of abbreviated ejection. Brain natriuretic peptide expression level, heart weight/body weight, and lung weight/body weight were all increased in MyBPC3(KO) mice, consistent with HF. MyBPC3(KO) mice also exhibit increased 1-year mortality. We used simultaneous twitch force and intracellular calcium [Ca2+]i measurements on intact papillary muscles to evaluate the consequences of losing cross-bridge cycling regulation on force response to changing [Ca2+]i transients. MyBPC3 (KO) myocardium exhibited abbreviated contractions despite slower calcium transients and an inability to accelerate relaxation with respect to peak contraction. Therefore, loss of MyBPC3-mediated coupling of cross-bridge cycling to the [Ca2+]i transient was associated with contractile dysfunction and HF.

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