Myosin binding protein C phosphorylation in normal, hypertrophic and failing human heart muscle

Jacques, Adam; Copeland, O'Neal; Messer, Andrew E.; Gallon, Clare E.; King, Katie; McKenna, William J.; Tsang, Victor; Marston, Steven B.

doi:10.1016/j.yjmcc.2008.05.020

Cited by 98 publications

(87 citation statements)

References 32 publications

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“…Here we show that Myk461 has salutary effects in reducing hypercontractility in myocardium lacking cMyBPC by decreasing the magnitude of force generation and the tension cost of force generation, which at the whole organ level would be expected to reduce systolic pressure generation, improve contractile efficiency, and reduce myocardial oxygen demands. Thus, development of Myk461‐based therapies may have utility in treating HCM patients expressing cMyBPC mutations, which are known to reduce the total amount of cMyBPC7 and induce severe cardiac dysfunction and death, especially at a young age 59, 60, 61. Our results define the mechanistic impact of Myk461 in hypercontractile myocardium lacking cMyBPC, and importantly, demonstrate that in KO myocardium Myk461‐induced force reductions were less pronounced than in WT myocardium.…”

Section: Discussionmentioning

confidence: 60%

“…Previous findings show that Myk461 inhibits myosin ATPase activity, decreases force generation, and prevents adverse cardiac remodeling in hypercontractile mouse hearts expressing HCM‐causing MHC missense mutations 21. It has been shown that myocardial samples isolated from HCM patients expressing cMyBPC mutations often display reduced total cMyBPC expression7, 25 and accelerated XB kinetics27; therefore, we sought to investigate the effects of Myk461 on the contractile function of myocardium lacking cMyBPC. In this context, recent data show that Myk461 stabilizes an autoinhibited state of 2‐headed myosin structure48 and also strengthens a folded‐back sequestered super‐relaxed state of myosin heads onto the thick filament backbone49—an effect that contributes to Myk461‐induced force depression by stabilizing the “ off ” state of myosin heads and preventing acto‐myosin formation.…”

Section: Discussionmentioning

confidence: 99%

“…At the whole heart level, HCM is characterized by hypercontractility, as indicated by an increased left ventricular ejection fraction3 and power output,4 and also diastolic dysfunction 5, 6. At the myofilament level, HCM‐related hypercontractility is often linked to enhanced sensitivity of the contractile apparatus to Ca 2+ ,7, 8 and accelerated rates of cross‐bridge (XB) cycling 9…”

Section: Introductionmentioning

confidence: 99%

“…This is mainly because missense mutations in β‐MHC that cause HCM result in incorporation of mutant proteins into the sarcomere, whereas the majority of mutations in cMyBPC that cause HCM often result in the production of truncated cMyBPC peptides, which are not incorporated into the sarcomere as they are likely removed by cellular quality control mechanisms such as non‐sense‐mediated mRNA decay or ubiquitin‐proteasome systems 24. The net result is decreased incorporation of full‐length cMyBPC into the sarcomere leading to haploinsufficiency 7, 8, 25, 26. Functionally, decreased incorporation of cMyBPC in human HCM samples expressing cMyBPC truncation mutations led to accelerated XB kinetics at submaximal Ca 2+ activations, in part, contributing to cardiac hypercontractility and hypertrophy 27.…”

Section: Introductionmentioning

confidence: 99%

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

Mamidi

Doh

et al. 2018

JAHA

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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.

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Section: Discussionmentioning

confidence: 60%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

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

Mamidi

Doh

et al. 2018

JAHA

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“…1A) (9, 10). β-Adrenergic-stimulated phosphorylation of these serines is believed to enhance cardiac contractility (11,12), and a high level of phosphorylation appears to be critical to normal cardiac function, whereas dephosphorylation has been associated with heart failure (13)(14)(15). Although the mechanistic role of cMyBP-C phosphorylation in vivo remains unclear, it is known to reduce the extensibility of the M-domain (10,16), diminish the binding of cMyBP-C to actin (17,18) and to myosin S2 (19), and to tune cMyBP-C's ability to modulate actomyosin activity in vitro (20)(21)(22)(23)(24).…”

mentioning

confidence: 99%

Phosphorylation and calcium antagonistically tune myosin-binding protein C’s structure and function

Previs

Mun

Michalek

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

106

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During each heartbeat, cardiac contractility results from calcium-activated sliding of actin thin filaments toward the centers of myosin thick filaments to shorten cellular length. Cardiac myosin-binding protein C (cMyBP-C) is a component of the thick filament that appears to tune these mechanochemical interactions by its N-terminal domains transiently interacting with actin and/or the myosin S2 domain, sensitizing thin filaments to calcium and governing maximal sliding velocity. Both functional mechanisms are potentially further tunable by phosphorylation of an intrinsically disordered, extensible region of cMyBP-C’s N terminus, the M-domain. Using atomic force spectroscopy, electron microscopy, and mutant protein expression, we demonstrate that phosphorylation reduced the M-domain’s extensibility and shifted the conformation of the N-terminal domain from an extended structure to a compact configuration. In combination with motility assay data, these structural effects of M-domain phosphorylation suggest a mechanism for diminishing the functional potency of individual cMyBP-C molecules. Interestingly, we found that calcium levels necessary to maximally activate the thin filament mitigated the structural effects of phosphorylation by increasing M-domain extensibility and shifting the phosphorylated N-terminal fragments back to the extended state, as if unphosphorylated. Functionally, the addition of calcium to the motility assays ablated the impact of phosphorylation on maximal sliding velocities, fully restoring cMyBP-C’s inhibitory capacity. We conclude that M-domain phosphorylation may have its greatest effect on tuning cMyBP-C’s calcium-sensitization of thin filaments at the low calcium levels between contractions. Importantly, calcium levels at the peak of contraction would allow cMyBP-C to remain a potent contractile modulator, regardless of cMyBP-C’s phosphorylation state.

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The use of phosphate‐affinity SDS‐PAGE to measure the cardiac troponin I phosphorylation site distribution in human heart muscle

Messer

Gallon

McKenna

et al. 2009

Proteomics Clinical Apps

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We have used phosphate affinity SDS-PAGE to separate the phosphorylated species of cardiac troponin I (cTnI). To test the method we phosphorylated pure cTnI with protein kinase A catalytic subunit and observed up to six bands corresponding to 0, 1P, 2P, 3P, 4P and 5P phospho-species. We examined the phospho-species of cTnI in human heart myofibrillar extracts by phosphate affinity SDS-PAGE and Western blotting with a non-specific troponin I (TnI) antibody. In donor heart samples the bis-phosphorylated species of cTnI predominated and no more highly phosphorylated species were not detectable (0P was 10.3±1.9%, 1P, 17.5±3.5%, 2P, 72.2±4.7%, 11 samples). Total phosphorylation was 1.62±0.06 molsPi/mol TnI. In myofibrils from end-stage failing hearts, the unphosphorylated cTnI species predominated (0P was 78.5±1.8%, 1P, 17.5±1.9%, 2P, 4.0±0.7%, total phosphorylation 0.26±0.02 molsPi/mol TnI, five samples). Muscle from patients with hypertrophic obstructive cardiomyopathy was also largely unphosphorylated (0P was 76.6±3.1%, 1P, 17.5±2.7%, 2P, 5.9±0.8%, total phosphorylation 0.29±0.04 molsPi/mol TnI, 19 samples). Using a range of phospho-specific antibodies we demonstrated that 3/4 of the bis-phosphorylated band of donor heart cTnI is phosphorylated at Ser22 and Ser23 in approximately equal amounts and that phosphorylation of Ser43 and Thr142 was not detected.

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Myosin binding protein C phosphorylation in normal, hypertrophic and failing human heart muscle

Cited by 98 publications

References 32 publications

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

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

Phosphorylation and calcium antagonistically tune myosin-binding protein C’s structure and function

The use of phosphate‐affinity SDS‐PAGE to measure the cardiac troponin I phosphorylation site distribution in human heart muscle

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