Cardiac myosin binding protein-C Ser 302 phosphorylation regulates cardiac β-adrenergic reserve

Doh

et al. 2018

JAHA

Self Cite

BackgroundRecent studies suggest that mavacamten (Myk461), a small myosin‐binding molecule, decreases hypercontractility in myocardium expressing hypertrophic cardiomyopathy‐causing missense mutations in myosin heavy chain. However, the predominant feature of most mutations in cardiac myosin binding protein‐C (cMyBPC) that cause hypertrophic cardiomyopathy is reduced total cMyBPC expression, and the impact of Myk461 on cMyBPC‐deficient myocardium is currently unknown.Methods and ResultsWe measured the impact of Myk461 on steady‐state and dynamic cross‐bridge (XB) behavior in detergent‐skinned mouse wild‐type myocardium and myocardium lacking cMyBPC (knockout (KO)). KO myocardium exhibited hypercontractile XB behavior as indicated by significant accelerations in rates of XB detachment (krel) and recruitment (kdf) at submaximal Ca2+ activations. Incubation of KO and wild‐type myocardium with Myk461 resulted in a dose‐dependent force depression, and this impact was more pronounced at low Ca2+ activations. Interestingly, Myk461‐induced force depressions were less pronounced in KO myocardium, especially at low Ca2+ activations, which may be because of increased acto‐myosin XB formation and potential disruption of super‐relaxed XBs in KO myocardium. Additionally, Myk461 slowed krel in KO myocardium but not in wild‐type myocardium, indicating increased XB “on” time. Furthermore, the greater degree of Myk461‐induced slowing in kdf and reduction in XB recruitment magnitude in KO myocardium normalized the XB behavior back to wild‐type levels.ConclusionsThis is the first study to demonstrate that Myk461‐induced force depressions are modulated by cMyBPC expression levels in the sarcomere, and emphasizes that clinical use of Myk461 may need to be optimized based on the molecular trigger that underlies the hypertrophic cardiomyopathy phenotype.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Impact of the Myosin Modulator Mavacamten on Force Generation and Cross‐Bridge Behavior in a Murine Model of Hypercontractility

Doh

et al. 2018

JAHA

Self Cite

“…18 The composition of various Ca 2+ solutions 21 used for experiments was calculated using a computer program 22 and using established stability constants 23 . OM (Selleckchem, Houston, TX, USA) and was initially dissolved in DMSO 11 and diluted in a relaxing solution to achieve final concentrations of 0.5μM or 1μM OM.…”

Section: Methodsmentioning

confidence: 99%

Dose-Dependent Effects of the Myosin Activator Omecamtiv Mecarbil on Cross-Bridge Behavior and Force Generation in Failing Human Myocardium

Gresham

et al. 2017

Circ: Heart Failure

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Background Omecamtiv mecarbil (OM) enhances systolic function in vivo by directly binding the myosin cross-bridges (XBs) in the sarcomere. However, the mechanistic details governing OM-induced modulation of XB behavior in failing human myocardium are unclear. Methods and results The effects of OM on steady-state and dynamic XB behavior were measured in chemically-skinned myocardial preparations isolated from human donor and heart failure (HF) left ventricle. HF myocardium exhibited impaired contractile function as evidenced by reduced maximal force, magnitude of XB recruitment (Pdf), and a slowed rate of XB detachment (krel) at submaximal Ca2+-activations. Ca2+-sensitivity of force generation (pCa50) was higher in HF myocardium when compared to donor myocardium, both prior to and following OM incubations. OM incubation (0.5μM and 1.0μM) enhanced force generation at sub-maximal Ca2+-activations in a dose-dependent manner. Notably, OM-induced a slowing in krel with 1.0μM OM but not with 0.5μM OM in HF myocardium. Additionally, OM exerted other differential effects on XB behavior in HF myocardium as evidenced by a greater enhancement in Pdf and slowing in the time-course of cooperative XB recruitment (Trec), which collectively prolonged achievement of peak force development (Tpk), compared to donor myocardium. Conclusions Our findings demonstrate that OM augments force generation but also prolongs the time course of XB transitions to force-bearing states in remodeled HF myocardium which may extend the systolic ejection time (SET) in vivo. Optimal OM dosing is critical for eliciting enhanced systolic function without excessive prolongation of SET which may compromise diastolic filling.

Lost in translation: Interpreting cardiac muscle mechanics data in clinical practice

Archives of Biochemistry and Biophysics

Doh

et al. 2019

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Current inotropic therapies improve systolic function in heart failure patients but they also elicit undesirable side effects such as arrhythmias and increased intracellular Ca 2+ transients. In order to maintain myocyte Ca 2+ homeostasis, the increased cytosolic Ca 2+ needs to be actively transported back to sarcoplasmic reticulum leading to depleted ATP reserves. Thus, an emerging approach is to design sarcomere-based treatments to correct impaired contractility via a direct and allosteric modulation of myosin's intrinsic force-generating behavior -a concept that potentially avoids the "off-target" effects. To achieve this goal, various biophysical approaches are utilized to investigate the mechanistic impact of sarcomeric modulators but information derived from diverse approaches is not fully integrated into therapeutic applications. This is in part due to the lack of information that provides a coherent connecting link between biophysical data to in vivo function. Hence, our ability to clearly discern the drug-mediated impact on whole-heart function is diminished. Reducing this translational barrier can significantly accelerate clinical progress related to sarcomere-based therapies by optimizing drug-dosing and treatment duration protocols based on information obtained from biophysical studies. Therefore, we attempt to link biophysical mechanical measurements obtained in isolated cardiac muscle and in vivo contractile function.