Molecular mechanism regulating myosin and cardiac functions by ELC

Lossie, Janine; Köhncke, Clemens; Mahmoodzadeh, Shokoufeh; Walter, Steffen; Canepari, Monica; Maffei, Manuela; Taube, Martin; Larchevêque, Oriane; Baumert, Philipp; Haase, Hannelore; Bottinelli, Roberto; Regitz‐Zagrosek, Vera; Morano, Ingo

doi:10.1016/j.bbrc.2014.05.142

Cited by 20 publications

(15 citation statements)

References 35 publications

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“…Similar results were obtained using the assay for adult zebrafish skeletal myosin step-size and step-frequency [11]. We proposed that the major 5 nm step is the default step identical to the dominant step in skeletal myosin [18], that the 8 nm step is somewhat less likely and different from the 5 nm step by involving an extra interaction with actin via the unique N-terminus extension of ELC [4, 19–21], and that the minor 3 nm step is the unlikely conversion of the 5 nm step to the full cELC bound 8 nm step. The 3 nm step is isolated in time from the 5 nm step by slow ADP dissociation hence we sometimes observe it as a separate step [22].…”

Section: Methodssupporting

confidence: 61%

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Auxotonic to isometric contraction transitioning in a beating heart causes myosin step-size to down shift

et al. 2017

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Myosin motors in cardiac ventriculum convert ATP free energy to the work of moving blood volume under pressure. The actin bound motor cyclically rotates its lever-arm/light-chain complex linking motor generated torque to the myosin filament backbone and translating actin against resisting force. Previous research showed that the unloaded in vitro motor is described with high precision by single molecule mechanical characteristics including unitary step-sizes of approximately 3, 5, and 8 nm and their relative step-frequencies of approximately 13, 50, and 37%. The 3 and 8 nm unitary step-sizes are dependent on myosin essential light chain (ELC) N-terminus actin binding. Step-size and step-frequency quantitation specifies in vitro motor function including duty-ratio, power, and strain sensitivity metrics. In vivo, motors integrated into the muscle sarcomere form the more complex and hierarchically functioning muscle machine. The goal of the research reported here is to measure single myosin step-size and step-frequency in vivo to assess how tissue integration impacts motor function.A photoactivatable GFP tags the ventriculum myosin lever-arm/light-chain complex in the beating heart of a live zebrafish embryo. Detected single GFP emission reports time-resolved myosin lever-arm orientation interpreted as step-size and step-frequency providing single myosin mechanical characteristics over the active cycle. Following step-frequency of cardiac ventriculum myosin transitioning from low to high force in relaxed to auxotonic to isometric contraction phases indicates that the imposition of resisting force during contraction causes the motor to down-shift to the 3 nm step-size accounting for >80% of all the steps in the near-isometric phase. At peak force, the ATP initiated actomyosin dissociation is the predominant strain inhibited transition in the native myosin contraction cycle. The proposed model for motor down-shifting and strain sensing involves ELC N-terminus actin binding.Overall, the approach is a unique bottom-up single molecule mechanical characterization of a hierarchically functional native muscle myosin.

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Section: Methodssupporting

confidence: 61%

“…RLC stabilizes the lever-arm [2] and disease implicated RLC mutants lower velocity, force, and strain sensitivity suggesting they alter lever-arm processing of stress [3]. The ELC N-terminus binds actin to modulate myosin functionality [4] and step-size in cardiac muscle [5]. …”

Section: Introductionmentioning

confidence: 99%

Auxotonic to isometric contraction transitioning in a beating heart causes myosin step-size to down shift

et al. 2017

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“…We proposed the model in Fig 3 where the major 5 nm step is the default step identical to the unitary step in sHMM. The 8 nm step is different from the 5 nm step by involving an extra interaction with actin via the unique N-terminus of the cardiac ELC (cELC) (Lossie et al 2014; Miller et al 2005; Miyanishi et al 2002; Muthu et al 2011; Petzhold et al 2014; Schaub et al 1998; Timson 2003). The minor 3 nm step is the unlikely conversion of the 5 nm step to the full cELC bound 8 nm step.…”

Section: Natural Myosin Activationmentioning

confidence: 99%

In vitro and in vivo single myosin step-sizes in striated muscle

Burghardt

Sun

Wang

et al. 2015

J Muscle Res Cell Motil

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Myosin in muscle transduces ATP free energy into the mechanical work of moving actin. It has a motor domain transducer containing ATP and actin binding sites, and, mechanical elements coupling motor impulse to the myosin filament backbone providing transduction/mechanical-coupling. The mechanical coupler is a lever-arm stabilized by bound essential and regulatory light chains. The lever-arm rotates cyclically to impel bound filamentous actin. Linear actin displacement due to lever-arm rotation is the myosin step-size. A high-throughput quantum dot labeled actin in vitro motility assay (Qdot assay) measures motor step-size in the context of an ensemble of actomyosin interactions. The ensemble context imposes a constant velocity constraint for myosins interacting with one actin filament. In a cardiac myosin producing multiple step-sizes, a “second characterization” is step-frequency that adjusts longer step-size to lower frequency maintaining a linear actin velocity identical to that from a shorter step-size and higher frequency actomyosin cycle. The step-frequency characteristic involves and integrates myosin enzyme kinetics, mechanical strain, and other ensemble affected characteristics. The high-throughput Qdot assay suits a new paradigm calling for wide surveillance of the vast number of disease or aging relevant myosin isoforms that contrasts with the alternative model calling for exhaustive research on a tiny subset myosin forms. The zebrafish embryo assay (Z assay) performs single myosin step-size and step-frequency assaying in vivo combining single myosin mechanical and whole muscle physiological characterizations in one model organism. The Qdot and Z assays cover “bottom-up” and “top-down” assaying of myosin characteristics.

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“…The ELC N-terminus is the single QFD that presents in both ventriculum and atrium centric inheritable diseases and is the largest contributor to probability in both α- and βmys. ELC is intimately involved in myosin strain-dependent mechanics 38 , its binding to the IQ domain (qe) stabilizes the lever arm 40 , and it is critical for the native folding of the myosin heavy chain after translation 41 . The lever arm (la) converts torque generated in the motor domain of myosin into linear displacement of actin.…”

Section: Resultsmentioning

confidence: 99%

Demographic Model for Inheritable Cardiac Disease

Burghardt

2019

Preprint

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19The cardiac muscle proteins, generating and regulating energy transduction during a heartbeat, 20 assemble in the sarcomere into a cyclical machine repetitively translating actin relative to myosin 21 filaments. Myosin is the motor transducing ATP free energy into actin movement against 22 resisting force. Cardiac myosin binding protein C (mybpc3) regulates shortening velocity 23 probably by transient N-terminus binding to actin while its C-terminus strongly binds the myosin 24 filament. Inheritable heart disease associated mutants frequently modify these proteins involving 25 them in disease mechanisms. Nonsynonymous single nucleotide polymorphisms (SNPs) cause 26 single residue substitutions with independent characteristics (sequence location, residue 27 substitution, human demographic, and allele frequency) hypothesized to decide dependent 28 phenotype and pathogenicity characteristics in a feed-forward Neural network model. Trial 29 models train and validate on a dynamic worldwide SNP database for cardiac muscle proteins 30 then predict phenotype and pathogenicity for any single residue substitution in myosin, mybpc3, 31 or actin. A separate Bayesian model formulates conditional probabilities for phenotype or 32 pathogenicity given independent SNP characteristics. Neural/Bayes forecasting tests SNP 33 pathogenicity vs (in)dependent SNP characteristics to assess individualized disease risk and in 34 particular to elucidate gender and human subpopulation bias in disease. Evident subpopulation 35 bias in myosin SNP pathogenicities imply myosin normally engages other sarcomere proteins 36 functionally. Consistent with this observation, mybpc3 forms a third actomyosin interaction 37competing with myosin essential light chain N-terminus suggesting a novel strain-dependent 38 mechanism adapting myosin force-velocity to load dynamics. The working models, and the 39 integral myosin/mybpc3 motor concept, portends the wider considerations involved in 40 understanding heart disease as a systemic maladaptation. 41 3 KEYWORDS 42 cardiac ventricular myosin, cardiac atrial myosin, cardiac myosin binding protein C, cardiac 43 actin, inheritable heart disease mechanism, machine learning, autonomous motor; hypertrophic 44 cardiomyopathy; dilated cardiomyopathy; restrictive cardiomyopathy; gender based risk 45 assessment 46 47 The cardiac muscle proteins generate and regulate energy transduction during a heartbeat. They 48 assemble into a cyclical machine in the sarcomere that repetitively translates actin relative to 49 myosin filaments. Myosin is the 50 motor transducing ATP free energy 51 to the work of moving actin against 52 resisting force. Cardiac myosin 53 binding protein C (mybpc3) 54 regulates shortening velocity 55 probably by binding transiently to 56 actin while stably bound to the 57 myosin filament.58Myosin (Fig 1) has a 140 59 kDa N-terminal globular head 60 called subfragment 1 (S1) and an 61 extended α-helical tail domain 62 (LMM+S2). Tail domains form 63 dimers that self-assemble into 64 myosin thick f...

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Molecular mechanism regulating myosin and cardiac functions by ELC

Cited by 20 publications

References 35 publications

Auxotonic to isometric contraction transitioning in a beating heart causes myosin step-size to down shift

Auxotonic to isometric contraction transitioning in a beating heart causes myosin step-size to down shift

In vitro and in vivo single myosin step-sizes in striated muscle

Demographic Model for Inheritable Cardiac Disease

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