Myosin Regulatory Light Chain (RLC) Phosphorylation Change as a Modulator of Cardiac Muscle Contraction in Disease

Toepfer, Christopher N.; Caorsi, Valentina; Kampourakis, Thomas; Sikkel, Markus B.; West, Timothy G.; Leung, Man Ching; Al-Saud, Sara Abou; MacLeod, Kenneth T.; Lyon, Alexander R.; Marston, Steven B.; Sellers, James R.; Ferenczi, Michael A.

doi:10.1074/jbc.m113.455444

Cited by 67 publications

(96 citation statements)

References 53 publications

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“…Given that the entire load velocity relationship is shifted to greater values, it is not surprising that power output of the individual myosin motor was increased upon phosphorylation. Studies utilizing porcine cardiac fibers showed that increased RLC phosphorylation levels lead to an increase in force and power output during fiber shortening at physiologically relevant loads [45]. A phosphorylation induced increase in the maximum power of isolated myosin shown in this work is likely a contributing factor to this phenomenon.…”

Section: Discussionmentioning

confidence: 71%

“…In cardiac muscle fibers, isometric force production increased with increasing levels of RLC phosphorylation during fiber shortening [45]. Interplay between cardiac myosin light chain kinase (MLCK) and a myosin phosphatase holoenzyme in human ventricular tissue is thought to maintain the level of RLC phosphorylation at about ~40% [5,25,30].…”

Section: Introductionmentioning

confidence: 99%

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Myosin regulatory light chain phosphorylation enhances cardiac β-myosin in vitro motility under load

Karabina

Kazmierczak

Szczesna‐Cordary

et al. 2015

Archives of Biochemistry and Biophysics

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Familial hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy and myofibrillar disarray, and often results in sudden cardiac death. Two HCM mutations, N47K and R58Q, are located in the myosin regulatory light chain (RLC). The RLC mechanically stabilizes the myosin lever arm, which is crucial to myosin’s ability to transmit contractile force. The N47K and R58Q mutations have previously been shown to reduce actin filament velocity under load, stemming from a more compliant lever arm (Greenberg, 2010). In contrast, RLC phosphorylation was shown to impart stiffness to the myosin lever arm (Greenberg, 2009). We hypothesized that phosphorylation of the mutant HCM-RLC may mitigate distinct mutation-induced structural and functional abnormalities. In vitro motility assays were utilized to investigate the effects of RLC phosphorylation on the HCM-RLC mutant phenotype in the presence of an α-actinin frictional load. Porcine cardiac β-myosin was depleted of its native RLC and reconstituted with mutant or wild-type human RLC in phosphorylated or non-phosphorylated form. Consistent with previous findings, in the presence of load, myosin bearing the HCM mutations reduced actin sliding velocity compared to WT resulting in 31–41% reductions in force production. Myosin containing phosphorylated RLC (WT or mutant) increased sliding velocity and also restored mutant myosin force production to near WT unphosphorylated values. These results point to RLC phosphorylation as a general mechanism to increase force production of the individual myosin motor and as a potential target to ameliorate the HCM-induced phenotype at the molecular level.

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Section: Discussionmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Myosin regulatory light chain phosphorylation enhances cardiac β-myosin in vitro motility under load

Karabina

Kazmierczak

Szczesna‐Cordary

et al. 2015

Archives of Biochemistry and Biophysics

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“…[37]. In cardiac muscle, RLC phosphorylation is associated with increased myocardial performance and enhances myosin motility under loaded conditions in vitro [38, 39]. Electron microscopic studies show that the motor domains of unphosphorylated skeletal and cardiac muscle myosin-2 filaments are held in close apposition to the filament backbone with a high degree of order.…”

Section: Regulation By Phosphorylationmentioning

confidence: 99%

Various Themes of Myosin Regulation

Heissler

Sellers

2016

Journal of Molecular Biology

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118

127

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Members of the myosin superfamily are actin-based molecular motors that are indispensable for cellular homeostasis. The vast functional and structural diversity of myosins accounts for the variety and complexity of the underlying allosteric regulatory mechanisms that determine the activation or inhibition of myosin motor activity and enable precise timing and spatial aspects of myosin function at the cellular level. This review focuses on the molecular basis of posttranslational regulation of eukaryotic myosins from different classes across species by allosteric intrinsic and extrinsic effectors. First, we highlight the impact of heavy and light chain phosphorylation. Second, we outline intramolecular regulatory mechanisms such as autoinhibition and subsequent activation. Third, we discuss diverse extramolecular allosteric mechanisms ranging from actin-linked regulatory mechanisms to myosin:cargo interactions. At last, we briefly outline the allosteric regulation of myosins with synthetic compounds.

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“…Higher RLC phosphorylation levels correlate with higher isometric force and power output in permeabilized rat cardiac trabeculae and with heart failure in human tissue (Toepfer et al 2013) implying it is a compensation mechanism for power shortage in failing heart.…”

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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Myosin Regulatory Light Chain (RLC) Phosphorylation Change as a Modulator of Cardiac Muscle Contraction in Disease

Cited by 67 publications

References 53 publications

Myosin regulatory light chain phosphorylation enhances cardiac β-myosin in vitro motility under load

Myosin regulatory light chain phosphorylation enhances cardiac β-myosin in vitro motility under load

Various Themes of Myosin Regulation

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

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