Molecular Mechanics of Cardiac Myosin-Binding Protein C in Native Thick Filaments

Previs, Michael J.; Previs, Samantha Beck; Gulick, James; Robbins, Jeffrey; Warshaw, David M.

doi:10.1126/science.1223602

Cited by 175 publications

(270 citation statements)

References 33 publications

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“…In addition to the thin filament activating effects of cMyBP-C at low Ca 2+ , cMyBP-C also governs contractility, as evidenced by enhanced unloaded cardiac muscle shortening velocities in cMyBP-C null mice (43). The inhibition of velocity in the presence of cMyBP-C occurs through cMyBP-C's N terminus, as observed previously by ourselves and others (16,19,20,50) and confirmed here (Fig. 6).…”

Section: Discussionsupporting

confidence: 71%

“…The cMyBP-C domains primarily involved in binding actin appear to be the C1 and M-domains (9,15,16,20), although there is evidence that C0 may be important (10,14). Previous modeling suggested that the C0 and C1 domains could clash with Tm in its blocked position (25,27,28), whereas experiments in which expressed N-terminal fragments were added to skinned cardiac myocytes implicated the ProAla-rich domain between C0 and C1 in modulating Ca 2+ activation of crossbridge cycling (46).…”

Section: Discussionmentioning

confidence: 99%

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Myosin-binding protein C displaces tropomyosin to activate cardiac thin filaments and governs their speed by an independent mechanism

Mun

Previs

et al. 2014

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

138

207

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Significance Myosin-binding protein C (MyBP-C) is a component of myosin filaments, one of the two sets of contractile elements whose relative sliding is the basis of muscle contraction. In the heart, MyBP-C modulates contractility in response to cardiac stimulation; mutations in MyBP-C lead to cardiac disease. The mechanism by which MyBP-C modulates cardiac contraction is not understood. Using electron microscopy and a light microscopic assay for filament sliding, we demonstrate that MyBP-C binds to the other set of filaments, containing actin and the regulatory component, tropomyosin. In so doing, it displaces tropomyosin from its inhibitory position to activate actin filament interaction with myosin, promoting filament sliding. These findings provide insights into the molecular basis of heart function.

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Section: Discussionsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 99%

Myosin-binding protein C displaces tropomyosin to activate cardiac thin filaments and governs their speed by an independent mechanism

Mun

Previs

et al. 2014

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

138

207

View full text Add to dashboard Cite

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“…1B). Using this assay, we showed that the sliding velocity of bare F-actin filaments was slowed within the C-zone of thick filaments and that the degree of slowing was reduced by phosphorylation of the four serines within the M-domain (21). Next, we examined the motion of native thin filaments containing the calcium-regulatory troponin-tropomyosin complex over native thick filaments.…”

Section: Significancementioning

confidence: 99%

“…filaments (21,23). The actin filaments used in this assay are short 250-nm shards, which allow independent probing of thick filament areas with and without cMyBP-C (the C-and D-zones, respectively) (Fig.…”

Section: Significancementioning

confidence: 99%

“…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%

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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 mechanics of the heart: zooming in on hypertrophic cardiomyopathy and cMyBP‐C

Suay-Corredera

Alegre-Cebollada

2022

FEBS Letters

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Hypertrophic cardiomyopathy (HCM), a disease characterized by cardiac muscle hypertrophy and hypercontractility, is the most frequently inherited disorder of the heart. HCM is mainly caused by variants in genes encoding proteins of the sarcomere, the basic contractile unit of cardiomyocytes. The most frequently mutated among them is MYBPC3, which encodes cardiac myosin-binding protein C (cMyBP-C), a key regulator of sarcomere contraction. In this review, we summarize clinical and genetic aspects of HCM and provide updated information on the function of the healthy and HCM sarcomere, as well as on emerging therapeutic options targeting sarcomere mechanical activity. Building on what is known about cMyBP-C activity, we examine different pathogenicity drivers by which MYBPC3 variants can cause disease, focussing on protein haploinsufficiency as a common pathomechanism also in nontruncating variants. Finally, we discuss recent evidence correlating altered cMyBP-C mechanical properties with HCM development.

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Molecular Mechanics of Cardiac Myosin-Binding Protein C in Native Thick Filaments

Cited by 175 publications

References 33 publications

Myosin-binding protein C displaces tropomyosin to activate cardiac thin filaments and governs their speed by an independent mechanism

Myosin-binding protein C displaces tropomyosin to activate cardiac thin filaments and governs their speed by an independent mechanism

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

The mechanics of the heart: zooming in on hypertrophic cardiomyopathy and cMyBP‐C

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