Hypertrophic cardiomyopathy mutations in the pliant and light chain-binding regions of the lever arm of human β-cardiac myosin have divergent effects on myosin function

Morck, Makenna M.; Bhowmik, Debanjan; Pathak, Divya; Dawood, Aminah; Spudich, James A.; Ruppel, Kathleen M.

doi:10.7554/elife.76805

Cited by 18 publications

(18 citation statements)

References 59 publications

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“…First, based on the position of Y115H, a reduction in step-size is an unexpected change. Previously, different mechanisms have been proposed to explain step-size changes observed for other mutations based on their location: uncoupling of the biochemical and mechanical activities of myosin (P710R 51 and R712L 49 in the converter), destabilization of the lever arm (L781P 37 ), and altered lever arm priming in the pre-powerstroke state (R671C 54 in the transducer). Judging from the location of Y115H in the motor head, it seems unlikely that this mutation affects lever arm coupling or compliance.…”

Section: Discussionmentioning

confidence: 99%

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Hypertrophic cardiomyopathy mutations Y115H and E497D disrupt the folded-back state of human beta-cardiac myosin allosterically

Nandwani,

Bhowmik,

Childers

et al. 2024

Preprint

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At the molecular level, clinical hypercontractility associated with many hypertrophic cardiomyopathy (HCM)-causing mutations in beta-cardiac myosin appears to be driven by their disruptive effect on the energy-conserving, folded-back, super relaxed (SRX) OFF-state of myosin. A pathological increase in force production results from release of heads from this OFF-state, which results in an increase in the number of heads free to interact with actin and produce force. Pathogenic mutations in myosin can conceivably disrupt the OFF-state by (1) directly affecting the intramolecular interfaces stabilizing the folded-back state, or (2) allosterically destabilizing the folded-back state via disruption of diverse conformational states of the myosin motor along its chemomechanical cycle. However, very little is understood about the mutations that fall in the latter group. Here, using recombinant human beta-cardiac myosin, we analysed the biomechanical properties of two such HCM-causing mutations, Y115H (in the transducer) and E497D (in the relay helix), neither of which falls in the regions that interact to stabilize the myosin folded-back state. We find these mutations have diverse effects on the contractility parameters of myosin, yet the primary hypercontractile change in both cases is the destabilization of the OFF-state of myosin and increased availability of active myosin heads for actin-binding. Experimental data and molecular dynamics simulations indicate that these mutations likely destabilize the pre-powerstroke state of myosin, the conformation the motor adopts in the inactive folded-back state. We propose that destabilization of the folded-back state of myosin, directly and/or allosterically, is the molecular basis of hypercontractility in HCM in a far greater number of pathogenic mutations than currently thought.

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Section: Discussionmentioning

confidence: 99%

“…Steady-state actin-activated ATP turnover rates were measured using a plate based NADH-coupled assay as previously described 37,74 . G-actin was prepared 75 from acetone powder from bovine cardiac LV tissue and polymerized to F-actin by dialyzing 5x into assay buffer containing 10 mM imidazole, pH 7.5, 5 mM KCl, 4 mM MgCl 2 and 1 mM DTT.…”

Section: Methodsmentioning

confidence: 99%

Hypertrophic cardiomyopathy mutations Y115H and E497D disrupt the folded-back state of human beta-cardiac myosin allosterically

Nandwani,

Bhowmik,

Childers

et al. 2024

Preprint

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“…In contrast, HCM mutations are thought to increase intrinsic motor properties and/or destabilize the autoinhibited state leading to increased force and power (23, 52, 53). Interestingly, exceptions are being identified, unraveling the idea that changes in one property of myosin equate to the resulting changes in ensemble force seen in the disease phenotype (10, 19, 20). The E525K DCM mutant is an example of an intriguing exception to this theory showing a DCM mutant can stabilize the autoinhibited state while also increasing intrinsic motor properties along with ensemble force and power of active heads.…”

Section: Discussionmentioning

confidence: 99%

“…For example, the leading hypothesis suggests that beta-cardiac myosin mutations that are “ gain of function ” are associated with HCM whereas “ loss of function ” are associated with DCM (18). However, exceptions have been identified, leaving room for debate within the field (10, 19, 20).…”

Section: Introductionmentioning

confidence: 99%

Dilated cardiomyopathy mutation in beta-cardiac myosin enhances actin activation of the power stroke and phosphate release

Bodt,

Ge,

et al. 2023

Preprint

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Inherited mutations in human beta-cardiac myosin (M2β) can lead to severe forms of heart failure. The E525K mutation in M2β is associated with dilated cardiomyopathy (DCM) and was found to stabilize the interacting heads motif (IHM) and autoinhibited super-relaxed (SRX) state in dimeric heavy meromyosin. However, in monomeric M2β subfragment 1 (S1) we found that E525K enhances (3-fold) the maximum steady-state actin-activated ATPase activity (kcat) and decreases (6-fold) the actin concentration at which ATPase is one-half maximal (KATPase). We also found a 3 to 4-fold increase in the actin-activated power stroke and phosphate release rate constants at 30 μM actin, which overall enhanced the duty ratio 3-fold. Loaded motility assays revealed that the enhanced intrinsic motor activity translates to increased ensemble force in M2β S1. Glutamate 525, located near the actin binding region in the so-called activation loop, is highly conserved and predicted to form a salt-bridge with another conserved residue (lysine 484) in the relay helix. Enhanced sampling molecular dynamics simulations predict that the charge reversal mutation disrupts the E525-K484 salt-bridge, inducing conformations with a more flexible relay helix and a wide phosphate release tunnel. Our results highlight a highly conserved allosteric pathway associated with actin activation of the power stroke and phosphate release and suggest an important feature of the autoinhibited IHM is to prevent this region of myosin from interacting with actin. The ability of the E525K mutation to stabilize the IHM likely overrides the enhanced intrinsic motor properties, which may be key to triggering DCM pathogenesis.Significance StatementHeart disease can be caused by inherited mutations in beta-cardiac myosin, the molecular motor that powers systolic contraction in the ventricles of the heart. However, it remains unclear how these mutations lead to contractile dysfunction and pathogenic remodeling of the heart. We investigated a unique dilated cardiomyopathy mutation (E525K) that dramatically stabilizes the autoinhibited state while enhancing intrinsic motor function. Thus, we examined how this mutation impacts transient kinetic steps of the ATPase cycle, motile properties, and structural changes associated with the power stroke and phosphate release. Our results provide a kinetic and structural basis for how beta-cardiac myosin mutations may disrupt molecular-level contractile function in complex ways, which may inform the development of targeted therapeutics.

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“…Structural information is also needed to design new modulators capable of enriching a personalized medicine approach. Indeed, hundreds of point-mutations are responsible for inherited cardiomyopathies and these mutations have diverse effects on β-cardiac myosin function and/or regulation 28,29,30,31 . Some mutations may impede the action of modulators, either by (i) reducing their affinity or (ii) blocking their allosteric effect.…”

Section: Figure 1 -Effect Of Omecamtiv Mecarbil (Om) and Mavacamten (...mentioning

confidence: 99%

Omecamtiv mecarbil and Mavacamten target the same myosin pocket despite antagonistic effects in heart contraction

Auguin,

Robert-Paganin,

Réty

et al. 2023

Preprint

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SummaryInherited cardiomyopathies are amongst the most common cardiac diseases worldwide, leading in the late-stage to heart failure and death. The most promising treatments against these diseases are small-molecules directly modulating the force produced by β-cardiac myosin, the molecular motor driving heart contraction. Two of these molecules that produce antagonistic effects on cardiac contractility have completed clinical phase 3 trials: the activatorOmecamtiv mecarbiland the inhibitorMavacamten. In this work, we reveal by X-ray crystallography that both drugs target the same pocket and stabilize a pre-stroke structural state, with only few local differences. All atoms molecular dynamics simulations reveal how these molecules can have antagonistic impact on the allostery of the motor by comparing β-cardiac myosin in the apo form or bound toOmecamtiv mecarbilorMavacamten. Altogether, our results provide the framework for rational drug development for the purpose of personalized medicine.

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Hypertrophic cardiomyopathy mutations in the pliant and light chain-binding regions of the lever arm of human β-cardiac myosin have divergent effects on myosin function

Cited by 18 publications

References 59 publications

Hypertrophic cardiomyopathy mutations Y115H and E497D disrupt the folded-back state of human beta-cardiac myosin allosterically

Hypertrophic cardiomyopathy mutations Y115H and E497D disrupt the folded-back state of human beta-cardiac myosin allosterically

Dilated cardiomyopathy mutation in beta-cardiac myosin enhances actin activation of the power stroke and phosphate release

Omecamtiv mecarbil and Mavacamten target the same myosin pocket despite antagonistic effects in heart contraction

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