Lys184 deletion in troponin I impairs relaxation kinetics and induces hypercontractility in murine cardiac myofibrils

Iorga, Bogdan; Blaudeck, Natascha; Solzin, Johannes; Neulen, Axel; Stehle, Ina; Dávila, Alfredo Jesús López; Pfitzer, Gabriele; Stehle, Robert

doi:10.1093/cvr/cvm113

Cited by 25 publications

(38 citation statements)

References 31 publications

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“…Altered myofibril function in cardiomyopathies Myofibril force kinetics have been shown to be altered by cardiomyopathy-related mutations or post-translational modifications of cTnI [65,80,107] and by mutations of myosin heavy chain [11]. In addition, passive mechanical properties of myofibrils are altered by titin-dependent mechanisms in dilated and ischemic cardiomyopathy [99,108].…”

Section: Troponin Regulatory Kineticsmentioning

confidence: 99%

“…Because the cardiac myofibril model is particularly useful for studying sarcomere relaxation kinetics and titindependent diastolic properties of cardiac muscle, it has great potential for the elucidation of the pathophysiological mechanisms of diastolic dysfunction at sarcomere level [65,80,107]. Diastolic dysfunction can lead to diastolic heart failure and is a highly prevalent feature in hypertrophic cardiomyopathy, diabetes and the ageing heart.…”

Section: Troponin Regulatory Kineticsmentioning

confidence: 99%

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Insights into the kinetics of Ca2+-regulated contraction and relaxation from myofibril studies

Stehle

Solzin

Iorga

et al. 2009

Pflugers Arch - Eur J Physiol

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Muscle contraction results from force-generating interactions between myosin cross-bridges on the thick filament and actin on the thin filament. The force-generating interactions are regulated by Ca(2+) via specialised proteins of the thin filament. It is controversial how the contractile and regulatory systems dynamically interact to determine the time course of muscle contraction and relaxation. Whereas kinetics of Ca(2+)-induced thin-filament regulation is often investigated with isolated proteins, force kinetics is usually studied in muscle fibres. The gap between studies on isolated proteins and structured fibres is now bridged by recent techniques that analyse the chemical and mechanical kinetics of small components of a muscle fibre, subcellular myofibrils isolated from skeletal and cardiac muscle. Formed of serially arranged repeating units called sarcomeres, myofibrils have a complete fully structured ensemble of contractile and Ca(2+) regulatory proteins. The small diameter of myofibrils (few micrometres) facilitates analysis of the kinetics of sarcomere contraction and relaxation induced by rapid changes of [ATP] or [Ca(2+)]. Among the processes studied on myofibrils are: (1) the Ca(2+)-regulated switch on/off of the troponin complex, (2) the chemical steps in the cross-bridge adenosine triphosphatase cycle, (3) the mechanics of force generation and (4) the length dynamics of individual sarcomeres. These studies give new insights into the kinetics of thin-filament regulation and of cross-bridge turnover, how cross-bridges transform chemical energy into mechanical work, and suggest that the cross-bridge ensembles of each half-sarcomere cooperate with each other across the half-sarcomere borders. Additionally, we now have a better understanding of muscle relaxation and its impairment in certain muscle diseases.

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Section: Troponin Regulatory Kineticsmentioning

confidence: 99%

Section: Troponin Regulatory Kineticsmentioning

confidence: 99%

Insights into the kinetics of Ca2+-regulated contraction and relaxation from myofibril studies

Stehle

Solzin

Iorga

et al. 2009

Pflugers Arch - Eur J Physiol

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“…Both the passive tension of titin and the active tension of cross-bridges can elevate sarcomere tension during relaxation and thus impair ventricular filling. Incomplete inactivation, either due to an incomplete reduction in [Ca 2+ ] to fully relaxing concentrations or due to an incomplete switching off of the regulatory troponin-tropomyosin system, causes residual active tension and slows relaxation (Iorga et al, 2008;Kruger et al, 2005;Stehle et al, 2009). Here, we use the N2B-knockout mice as a genetic model of diastolic dysfunction to investigate whether increased titin-based stiffness also slows down cardiac myofibrillar relaxation.…”

Section: Introductionmentioning

confidence: 99%

Deletion of the titin N2B region accelerates myofibrillar force development but does not alter relaxation kinetics

Elhamine

Radkë

Pfitzer

et al. 2014

Journal of Cell Science

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Cardiac titin is the main determinant of sarcomere stiffness during diastolic relaxation. To explore whether titin stiffness affects the kinetics of cardiac myofibrillar contraction and relaxation, we used subcellular myofibrils from the left ventricles of homozygous and heterozygous N2B-knockout mice which express truncated cardiac titins lacking the unique elastic N2B region. Compared with myofibrils from wild-type mice, myofibrils from knockout and heterozygous mice exhibit increased passive myofibrillar stiffness. To determine the kinetics of Ca 2+ -induced force development (rate constant k ACT ), myofibrils from knockout, heterozygous and wildtype mice were stretched to the same sarcomere length (2.3 mm) and rapidly activated with Ca 2+. Additionally, mechanically induced force-redevelopment kinetics (rate constant k TR ) were determined by slackening and re-stretching myofibrils during Ca 2+ -mediated activation. Myofibrils from knockout mice exhibited significantly higher k ACT , k TR and maximum Ca 2+ -activated tension than myofibrils from wild-type mice. By contrast, the kinetic parameters of biphasic force relaxation induced by rapidly reducing [Ca 2+ ] were not significantly different among the three genotypes. These results indicate that increased titin stiffness promotes myocardial contraction by accelerating the formation of force-generating crossbridges without decelerating relaxation.

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“…It is widely accepted that HCM myofilament mutations and strong cross-bridges modulate the Ca 2ϩ affinity and the rate of Ca 2ϩ dissociation from cTnC (18 -21). It is expected that these factors will influence cardiac muscle relaxation by prolonging the Ca 2ϩ and force transients (5,(22)(23)(24)(25)(26)(27), which can be correlated with the diastolic dysfunction seen in patients and animal models of hypertrophy.…”

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confidence: 99%

Strong Cross-bridges Potentiate the Ca2+ Affinity Changes Produced by Hypertrophic Cardiomyopathy Cardiac Troponin C Mutants in Myofilaments

Pinto

Reynaldo

Parvatiyar

et al. 2011

Journal of Biological Chemistry

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This spectroscopic study examined the steady-state and kinetic parameters governing the cross-bridge effect on the increased Ca 2؉ affinity of hypertrophic cardiomyopathy-cardiac troponin C (HCM-cTnC) mutants. Previously, we found that incorporation of the A8V and D145E HCM-cTnC mutants, but not E134D into thin filaments (TFs), increased the apparent Ca 2؉ affinity relative to TFs containing the WT protein. Here, we show that the addition of myosin subfragment 1 (S1) to TFs reconstituted with these mutants in the absence of MgATP 2؊ , the condition conducive to rigor cross-bridge formation, further increased the apparent Ca 2؉ affinity. Stopped-flow fluorescence techniques were used to determine the kinetics of Ca 2؉ dissociation (k off ) from the cTnC mutants in the presence of TFs and S1. At a high level of complexity (i.e. TF ؉ S1), an increase in the Ca 2؉ affinity and decrease in k off was achieved for the A8V and D145E mutants when compared with WT. Therefore, it appears that the cTnC Ca 2؉ off-rate is most likely to be affected rather than the Ca 2؉ on rate. At all levels of TF complexity, the results obtained with the E134D mutant reproduced those seen with the WT protein. We conclude that strong cross-bridges potentiate the Ca 2؉ -sensitizing effect of HCM-cTnC mutants on the myofilament. Finally, the slower k off from the A8V and D145E mutants can be directly correlated with the diastolic dysfunction seen in these patients.

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Lys184 deletion in troponin I impairs relaxation kinetics and induces hypercontractility in murine cardiac myofibrils

Cited by 25 publications

References 31 publications

Insights into the kinetics of Ca2+-regulated contraction and relaxation from myofibril studies

Insights into the kinetics of Ca2+-regulated contraction and relaxation from myofibril studies

Deletion of the titin N2B region accelerates myofibrillar force development but does not alter relaxation kinetics

Strong Cross-bridges Potentiate the Ca2+ Affinity Changes Produced by Hypertrophic Cardiomyopathy Cardiac Troponin C Mutants in Myofilaments

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