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Musgrave JH, Han JC, Ward ML, Taberner AJ, Loiselle DS, Tran K. Uncovering cross-bridge properties that underlie the cardiac active complex modulus using model linearisation techniques. Math Biosci 2022; 353:108922. [DOI: 10.1016/j.mbs.2022.108922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 09/12/2022] [Accepted: 10/12/2022] [Indexed: 11/05/2022]
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Trujillo AS, Hsu KH, Puthawala J, Viswanathan MC, Loya A, Irving TC, Cammarato A, Swank DM, Bernstein SI. Myosin dilated cardiomyopathy mutation S532P disrupts actomyosin interactions, leading to altered muscle kinetics, reduced locomotion, and cardiac dilation in Drosophila. Mol Biol Cell 2021; 32:1690-1706. [PMID: 34081531 PMCID: PMC8684735 DOI: 10.1091/mbc.e21-02-0088] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Dilated cardiomyopathy (DCM), a life-threatening disease characterized by pathological heart enlargement, can be caused by myosin mutations that reduce contractile function. To better define the mechanistic basis of this disease, we employed the powerful genetic and integrative approaches available in Drosophila melanogaster. To this end, we generated and analyzed the first fly model of human myosin-induced DCM. The model reproduces the S532P human β-cardiac myosin heavy chain DCM mutation, which is located within an actin-binding region of the motor domain. In concordance with the mutation's location at the actomyosin interface, steady-state ATPase and muscle mechanics experiments revealed that the S532P mutation reduces the rates of actin-dependent ATPase activity and actin binding and increases the rate of actin detachment. The depressed function of this myosin form reduces the number of cross-bridges during active wing beating, the power output of indirect flight muscles, and flight ability. Further, S532P mutant hearts exhibit cardiac dilation that is mutant gene dose-dependent. Our study shows that Drosophila can faithfully model various aspects of human DCM phenotypes and suggests that impaired actomyosin interactions in S532P myosin induce contractile deficits that trigger the disease.
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Affiliation(s)
- Adriana S Trujillo
- Department of Biology, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182
| | - Karen H Hsu
- Department of Biology, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182
| | - Joy Puthawala
- Department of Biological Sciences and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180
| | - Meera C Viswanathan
- Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Amy Loya
- Department of Biological Sciences and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180
| | - Thomas C Irving
- Center for Synchrotron Radiation Research and Instrumentation and Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616
| | - Anthony Cammarato
- Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Douglas M Swank
- Department of Biological Sciences and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180
| | - Sanford I Bernstein
- Department of Biology, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182
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Pewowaruk RJ, Philip JL, Tewari SG, Chen CS, Nyaeme MS, Wang Z, Tabima DM, Baker AJ, Beard DA, Chesler NC. Multiscale Computational Analysis of Right Ventricular Mechanoenergetics. J Biomech Eng 2019; 140:2679646. [PMID: 30003251 DOI: 10.1115/1.4040044] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Indexed: 11/08/2022]
Abstract
Right ventricular (RV) failure, which occurs in the setting of pressure overload, is characterized by abnormalities in mechanical and energetic function. The effects of these cell- and tissue-level changes on organ-level RV function are unknown. The primary aim of this study was to investigate the effects of myofiber mechanics and mitochondrial energetics on organ-level RV function in the context of pressure overload using a multiscale model of the cardiovascular system. The model integrates the mitochondria-generated metabolite concentrations that drive intracellular actin-myosin cross-bridging and extracellular myocardial tissue mechanics in a biventricular heart model coupled with simple lumped parameter circulations. Three types of pressure overload were simulated and compared to experimental results. The computational model was able to capture a wide range of cardiovascular physiology and pathophysiology from mild RV dysfunction to RV failure. Our results confirm that, in response to pressure overload alone, the RV is able to maintain cardiac output (CO) and predict that alterations in either RV active myofiber mechanics or RV metabolite concentrations are necessary to decrease CO.
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Affiliation(s)
- Ryan J Pewowaruk
- Mem. ASME Biomedical Engineering, University of Wisconsin-Madison, 2145 Engineering Centers Building, 1550 Engineering Drive, Madison, WI 53706 e-mail:
| | - Jennifer L Philip
- Surgery, University of Wisconsin-Madison, , 1550 Engineering Drive, Madison, WI 53706 e-mail:
| | - Shivendra G Tewari
- Molecular & Integrative Physiology, University of Michigan-Ann Arbor, , North Campus Research Center, Ann Arbor, MI 48109-5622 e-mail:
| | - Claire S Chen
- Mechanical Engineering, University of Wisconsin-Madison, , 1550 Engineering Drive, Madison, WI 53706 e-mail:
| | - Mark S Nyaeme
- Biomedical Engineering, University of Wisconsin-Madison, , 1550 Engineering Drive, Madison, WI 53706 e-mail:
| | - Zhijie Wang
- Mechanical Engineering, Colorado State University, , Fort Collins, CO 80521 e-mail:
| | - Diana M Tabima
- Biomedical Engineering, University of Wisconsin-Madison, , 1550 Engineering Drive, Madison, WI 53706 e-mail:
| | - Anthony J Baker
- Medicine, University of California-San Francisco, , San Francisco, CA 94121; VA Medical Center, 4150 Clement St., San Francisco, CA 94121 e-mail:
| | - Daniel A Beard
- Molecular & Integrative Physiology, University of Michigan-Ann Arbor, , North Campus Research Center, Ann Arbor, MI 48109-5622 e-mail:
| | - Naomi C Chesler
- Fellow ASME Biomedical Engineering, University of Wisconsin-Madison Medicine, , 1550 Engineering Drive, Madison, WI 53706 e-mail:
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Kieu TT, Awinda PO, Tanner BCW. Omecamtiv Mecarbil Slows Myosin Kinetics in Skinned Rat Myocardium at Physiological Temperature. Biophys J 2019; 116:2149-2160. [PMID: 31103235 DOI: 10.1016/j.bpj.2019.04.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 04/10/2019] [Accepted: 04/15/2019] [Indexed: 12/15/2022] Open
Abstract
Heart failure is a life-threatening condition that occurs when the heart muscle becomes weakened and cannot adequately circulate blood and nutrients around the body. Omecamtiv mecarbil (OM) is a compound that has been developed to treat systolic heart failure via targeting the cardiac myosin heavy chain to increase myocardial contractility. Biophysical and biochemical studies have found that OM increases calcium (Ca2+) sensitivity of contraction by prolonging the myosin working stroke and increasing the actin-myosin cross-bridge duty ratio. Most in vitro studies probing the effects of OM on cross-bridge kinetics and muscle force production have been conducted at subphysiological temperature, even though temperature plays a critical role in enzyme activity and cross-bridge function. Herein, we used skinned, ventricular papillary muscle strips from rats to investigate the effects of [OM] on Ca2+-activated force production, cross-bridge kinetics, and myocardial viscoelasticity at physiological temperature (37°C). We find that OM only increases myocardial contractility at submaximal Ca2+ activation levels and not maximal Ca2+ activation levels. As [OM] increased, the kinetic rate constants for cross-bridge recruitment and detachment slowed for both submaximal and maximal Ca2+-activated conditions. These findings support a mechanism by which OM increases cardiac contractility at physiological temperature via increasing cross-bridge contributions to thin-filament activation as cross-bridge kinetics slow and the duration of cross-bridge attachment increases. Thus, force only increases at submaximal Ca2+ activation due to cooperative recruitment of neighboring cross-bridges, because thin-filament activation is not already saturated. In contrast, OM does not increase myocardial force production for maximal Ca2+-activated conditions at physiological temperature because cooperative activation of thin filaments may already be saturated.
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Affiliation(s)
- Thinh T Kieu
- Department of Integrative Physiology and Neuroscience
| | | | - Bertrand C W Tanner
- Department of Integrative Physiology and Neuroscience; Washington Center for Muscle Biology, Washington State University, Pullman, Washington.
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Breithaupt JJ, Pulcastro HC, Awinda PO, DeWitt DC, Tanner BCW. Regulatory light chain phosphorylation augments length-dependent contraction in PTU-treated rats. J Gen Physiol 2018; 151:66-76. [PMID: 30523115 PMCID: PMC6314387 DOI: 10.1085/jgp.201812158] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 11/07/2018] [Indexed: 12/13/2022] Open
Abstract
Contraction of cardiac muscle is regulated by sarcomere length and proteins that comprise the sarcomeric filaments. Breithaupt et al. find that phosphorylation of myosin regulatory light chain augments length-dependent activation of contraction when β-cardiac myosin heavy chain predominates. Force production by actin–myosin cross-bridges in cardiac muscle is regulated by thin-filament proteins and sarcomere length (SL) throughout the heartbeat. Prior work has shown that myosin regulatory light chain (RLC), which binds to the neck of myosin heavy chain, increases cardiac contractility when phosphorylated. We recently showed that cross-bridge kinetics slow with increasing SLs, and that RLC phosphorylation amplifies this effect, using skinned rat myocardial strips predominantly composed of the faster α-cardiac myosin heavy chain isoform. In the present study, to assess how RLC phosphorylation influences length-dependent myosin function as myosin motor speed varies, we used a propylthiouracil (PTU) diet to induce >95% expression of the slower β-myosin heavy chain isoform in rat cardiac ventricles. We measured the effect of RLC phosphorylation on Ca2+-activated isometric contraction and myosin cross-bridge kinetics (via stochastic length perturbation analysis) in skinned rat papillary muscle strips at 1.9- and 2.2-µm SL. Maximum tension and Ca2+ sensitivity increased with SL, and RLC phosphorylation augmented this response at 2.2-µm SL. Subtle increases in viscoelastic myocardial stiffness occurred with RLC phosphorylation at 2.2-µm SL, but not at 1.9-µm SL, thereby suggesting that RLC phosphorylation increases β-myosin heavy chain binding or stiffness at longer SLs. The cross-bridge detachment rate slowed as SL increased, providing a potential mechanism for prolonged cross-bridge attachment to augment length-dependent activation of contraction at longer SLs. Length-dependent slowing of β-myosin heavy chain detachment rate was not affected by RLC phosphorylation. Together with our previous studies, these data suggest that both α- and β-myosin heavy chain isoforms show a length-dependent activation response and prolonged myosin attachment as SL increases in rat myocardial strips, and that RLC phosphorylation augments length-dependent activation at longer SLs. In comparing cardiac isoforms, however, we found that β-myosin heavy chain consistently showed greater length-dependent sensitivity than α-myosin heavy chain. Our work suggests that RLC phosphorylation is a vital contributor to the regulation of myocardial contractility in both cardiac myosin heavy chain isoforms.
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Affiliation(s)
- Jason J Breithaupt
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
| | - Hannah C Pulcastro
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
| | - Peter O Awinda
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
| | - David C DeWitt
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
| | - Bertrand C W Tanner
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA
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Tewari SG, Bugenhagen SM, Palmer BM, Beard DA. Dynamics of cross-bridge cycling, ATP hydrolysis, force generation, and deformation in cardiac muscle. J Mol Cell Cardiol 2016; 96:11-25. [PMID: 25681584 PMCID: PMC4532654 DOI: 10.1016/j.yjmcc.2015.02.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 01/29/2015] [Accepted: 02/04/2015] [Indexed: 11/27/2022]
Abstract
Despite extensive study over the past six decades the coupling of chemical reaction and mechanical processes in muscle dynamics is not well understood. We lack a theoretical description of how chemical processes (metabolite binding, ATP hydrolysis) influence and are influenced by mechanical processes (deformation and force generation). To address this need, a mathematical model of the muscle cross-bridge (XB) cycle based on Huxley's sliding filament theory is developed that explicitly accounts for the chemical transformation events and the influence of strain on state transitions. The model is identified based on elastic and viscous moduli data from mouse and rat myocardial strips over a range of perturbation frequencies, and MgATP and inorganic phosphate (Pi) concentrations. Simulations of the identified model reproduce the observed effects of MgATP and MgADP on the rate of force development. Furthermore, simulations reveal that the rate of force re-development measured in slack-restretch experiments is not directly proportional to the rate of XB cycling. For these experiments, the model predicts that the observed increase in the rate of force generation with increased Pi concentration is due to inhibition of cycle turnover by Pi. Finally, the model captures the observed phenomena of force yielding suggesting that it is a result of rapid detachment of stretched attached myosin heads.
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Affiliation(s)
- Shivendra G Tewari
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Scott M Bugenhagen
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Bradley M Palmer
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA
| | - Daniel A Beard
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA.
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Land S, Niederer SA, Aronsen JM, Espe EKS, Zhang L, Louch WE, Sjaastad I, Sejersted OM, Smith NP. An analysis of deformation-dependent electromechanical coupling in the mouse heart. J Physiol 2012; 590:4553-69. [PMID: 22615436 PMCID: PMC3477757 DOI: 10.1113/jphysiol.2012.231928] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 05/17/2012] [Indexed: 01/20/2023] Open
Abstract
To investigate the effects of the coupling between excitation and contraction on whole-organ function, we have developed a novel biophysically based multiscale electromechanical model of the murine heart. Through comparison with a comprehensive in vivo experimental data set, we show good agreement with pressure and volume measurements at both physiological temperatures and physiological pacing frequencies. This whole-organ model was used to investigate the effects of material and haemodynamic properties introduced at the tissue level, as well as emergent function of our novel cell contraction model. Through a comprehensive sensitivity analysis at both the cellular and whole organ level, we demonstrate the sensitivity of the model's results to its parameters and the constraining effect of experimental data. These results demonstrate the fundamental importance of length- and velocity-dependent feedback to the cellular scale for whole-organ function, and we show that a strong velocity dependence of tension is essential for explaining the differences between measured single cell tension and whole-organ pressure transients.
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Affiliation(s)
- Sander Land
- Department of Computer Science, University of Oxford, Oxford, UK
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Toth MJ, Miller MS, VanBuren P, Bedrin NG, LeWinter MM, Ades PA, Palmer BM. Resistance training alters skeletal muscle structure and function in human heart failure: effects at the tissue, cellular and molecular levels. J Physiol 2011; 590:1243-59. [PMID: 22199163 DOI: 10.1113/jphysiol.2011.219659] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Reduced skeletal muscle function in heart failure (HF) patients may be partially explained by altered myofilament protein content and function. Resistance training increases muscle function, although whether these improvements are achieved by correction of myofilament deficits is not known. To address this question, we examined 10 HF patients and 14 controls prior to and following an 18 week high-intensity resistance training programme. Evaluations of whole muscle size and strength, single muscle fibre size, ultrastructure and tension and myosin-actin cross-bridge mechanics and kinetics were performed. Training improved whole muscle isometric torque in both groups, although there were no alterations in whole muscle size or single fibre cross-sectional area or isometric tension.Unexpectedly, training reduced the myofibril fractional area of muscle fibres in both groups. This structural change manifested functionally as a reduction in the number of strongly bound myosin-actin cross-bridges during Ca²⁺ activation. When post-training single fibre tension data were corrected for the loss of myofibril fractional area, we observed an increase in tension with resistance training. Additionally, training corrected alterations in cross-bridge kinetics (e.g. myosin attachment time) in HF patients back to levels observed in untrained controls. Collectively, our results indicate that improvements in myofilament function in sedentary elderly with and without HF may contribute to increased whole muscle function with resistance training. More broadly, these data highlight novel cellular and molecular adaptations in muscle structure and function that contribute to the resistance-trained phenotype.
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Affiliation(s)
- Michael J Toth
- Health Science Research Facility 126B, 149 Beaumont Ave, University of Vermont, Burlington, VT 05405, USA.
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Distribution of myosin attachment times predicted from viscoelastic mechanics of striated muscle. J Biomed Biotechnol 2011; 2011:592343. [PMID: 22190855 PMCID: PMC3228685 DOI: 10.1155/2011/592343] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Accepted: 08/22/2011] [Indexed: 11/17/2022] Open
Abstract
We demonstrate that viscoelastic mechanics of striated muscle, measured as elastic and viscous moduli, emerge directly from the myosin crossbridge attachment time, tatt, also called time-on. The distribution of tatt was modeled using a gamma distribution with shape parameter, p, and scale parameter, β. At 5 mM MgATP, β was similar between mouse α-MyHC (16.0 ± 3.7 ms) and β-MyHC (17.9 ± 2.0 ms), and p was higher (P < 0.05) for β-MyHC (5.6 ± 0.4 no units) compared to α-MyHC (3.2 ± 0.9). At 1 mM MgATP, p approached a value of 10 in both isoforms, but β rose only in the β-MyHC (34.8 ± 5.8 ms). The estimated mean tatt (i.e., pβ product) was longer in the β-MyHC compared to α-MyHC, and became prolonged in both isoforms as MgATP was reduced as expected. The application of our viscoelastic model to these isoforms and varying MgATP conditions suggest that tatt is better modeled as a gamma distribution due to its representing multiple temporal events occurring within tatt compared to a single exponential distribution which assumes only one temporal event within tatt.
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Tanner BCW, Wang Y, Maughan DW, Palmer BM. Measuring myosin cross-bridge attachment time in activated muscle fibers using stochastic vs. sinusoidal length perturbation analysis. J Appl Physiol (1985) 2011; 110:1101-8. [PMID: 21233339 PMCID: PMC3075125 DOI: 10.1152/japplphysiol.00800.2010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 01/11/2011] [Indexed: 11/22/2022] Open
Abstract
The average time myosin cross bridges remain bound to actin (t(on)) can be measured by sinusoidal length perturbations (sinusoidal analysis) of striated muscle fibers using recently developed analytic methods. This approach allows measurements of t(on) in preparations possessing a physiologically relevant myofilament lattice. In this study, we developed an approach to measure t(on) in 5-10% of the time required for sinusoidal analysis by using stochastic length perturbations (white noise analysis). To compare these methods, we measured the influence of MgATP concentration ([MgATP]) on t(on) in demembranated myocardial strips from mice, sampling muscle behavior from 0.125 to 200 Hz with a 20-s burst of white noise vs. a 300-s series of sinusoids. Both methods detected a similar >300% increase in t(on) as [MgATP] decreased from 5 to 0.25 mM, differing by only 3-14% at any [MgATP]. Additional experiments with Drosophila indirect flight muscle fibers demonstrated that faster cross-bridge cycling kinetics permit further reducing of the perturbation time required to measure t(on). This reduced sampling time allowed strain-dependent measurements of t(on) in flight muscle fibers by combining 10-s bursts of white noise during periods of linear shortening and lengthening. Analyses revealed longer t(on) values during shortening and shorter t(on) values during lengthening. This asymmetry may provide a mechanism that contributes to oscillatory energy transfer between the flight muscles and thoracic cuticle to power flight. This study demonstrates that white noise analysis can detect underlying molecular processes associated with dynamic muscle contraction comparable to sinusoidal analysis, but in a fraction of the time.
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Affiliation(s)
- Bertrand C W Tanner
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont, USA.
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