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Journal of Muscle Research and Cell... Sep 2023The structure of the thin, actin-containing filament of muscle is both highly conserved across a broad range of muscle types and is now well understood. The structure of... (Review)
Review
The structure of the thin, actin-containing filament of muscle is both highly conserved across a broad range of muscle types and is now well understood. The structure of the thick, myosin-containing filaments of striated muscle are quite variable and remained comparatively unknown until recently, particularly in the arrangement of the myosin tails. John Squire played a major role not only in our understanding of thin filament structure and function but also in the structure of the thick filaments. Long before much was known about the structure and composition of muscle thick filaments, he proposed a general model for how myosin filaments were constructed. His role in our current understanding the structure of striated muscle thick filaments and the extent through which his predictions have held true is the topic of this review.
Topics: Myosins; Sarcomeres; Muscle, Skeletal; Actin Cytoskeleton
PubMed: 37099254
DOI: 10.1007/s10974-023-09646-4 -
Journal of Biochemistry Apr 2021Myosin within the nucleus has often been overlooked due to their importance in cytoplasmic processes and a lack of investigation. However, more recently, it has been... (Review)
Review
Myosin within the nucleus has often been overlooked due to their importance in cytoplasmic processes and a lack of investigation. However, more recently, it has been shown that their nuclear roles are just as fundamental to cell function and survival with roles in transcription, DNA damage and viral replication. Myosins can act as molecular transporters and anchors that rely on their actin binding and ATPase capabilities. Their roles within the DNA damage response can varies from a transcriptional response, moving chromatin and stabilizing chromosome contacts. This review aims to highlight their key roles in the DNA damage response and how they impact nuclear organization and transcription.
Topics: Actins; Adenosine Triphosphatases; Animals; Cell Nucleus; Cytoplasm; DNA Damage; Humans; Myosins; Protein Binding; Transcription, Genetic
PubMed: 33035317
DOI: 10.1093/jb/mvaa113 -
Methods in Molecular Biology (Clifton,... 2024Fast transient kinetics using stopped-flow fluorimetry is now a powerful method for defining the ATPase cycle of myosin and its subfragments and has found wide use in...
Fast transient kinetics using stopped-flow fluorimetry is now a powerful method for defining the ATPase cycle of myosin and its subfragments and has found wide use in defining the difference between myosin isoforms, myosins carrying disease linked mutations, and the effect of small molecules on the ATPase cycle. Here the protocols for completing the classical assays of myosin and actin.myosin using the stopped-flow are described. The assays include ATP and ADP binding to myosin and actin.myosin, displacement of ADP from myosin and actin.myosin, and the cleavage of ATP to ADP and phosphate on myosin. Single and multiple turnover assays are also described.
Topics: Actins; Myosins; Adenosine Triphosphatases; Physics; Kinetics; Adenosine Triphosphate; Adenosine Diphosphate
PubMed: 38038850
DOI: 10.1007/978-1-0716-3527-8_11 -
Current Cardiology Reports Jun 2021Pharmacological treatment options for hypertrophic cardiomyopathy (HCM) are currently limited and comprise non-disease specific therapies such as β-blockers,... (Review)
Review
PURPOSE OF REVIEW
Pharmacological treatment options for hypertrophic cardiomyopathy (HCM) are currently limited and comprise non-disease specific therapies such as β-blockers, non-dihydropyridine calcium channel blockers, and disopyramide. These agents that offer a variable degree of symptomatic relief, often suboptimal, are often limited by side-effects and fail to address the key molecular abnormalities of the disease.
RECENT FINDINGS
Mavacamten is a novel, first-in-class, allosteric inhibitor of cardiac myosin ATPase, which reduces actin-myosin cross-bridge formation, thereby reducing myocardial contractility and improving myocardial energetic consumption in experimental HCM models. Following a successful Phase 2 study, the recently published phase III, placebo-controlled, randomized EXPLORER-HCM trial demonstrated the efficacy and safety of mavacamten in reducing left ventricular outflow tract obstruction and ameliorating exercise capacity, New York Heart Association functional class and health status in patients with obstructive HCM. Mavacamten represents the first agent specifically developed for HCM successfully tested in a Phase III trial, to be registered soon for clinical use, representing a radical change of paradigm in the pharmacological treatment of HCM.
Topics: Benzylamines; Cardiac Myosins; Cardiomyopathy, Hypertrophic; Clinical Trials, Phase III as Topic; Humans; Randomized Controlled Trials as Topic; Uracil
PubMed: 34081217
DOI: 10.1007/s11886-021-01508-0 -
Comprehensive Physiology Dec 2016The striated muscle sarcomere is a highly organized and complex enzymatic and structural organelle. Evolutionary pressures have played a vital role in determining the... (Review)
Review
The striated muscle sarcomere is a highly organized and complex enzymatic and structural organelle. Evolutionary pressures have played a vital role in determining the structure-function relationship of each protein within the sarcomere. A key part of this multimeric assembly is the light chain-binding domain (LCBD) of the myosin II motor molecule. This elongated "beam" functions as a biological lever, amplifying small interdomain movements within the myosin head into piconewton forces and nanometer displacements against the thin filament during the cross-bridge cycle. The LCBD contains two subunits known as the essential and regulatory myosin light chains (ELC and RLC, respectively). Isoformic differences in these respective species provide molecular diversity and, in addition, sites for phosphorylation of serine residues, a highly conserved feature of striated muscle systems. Work on permeabilized skeletal fibers and thick filament systems shows that the skeletal myosin light chain kinase catalyzed phosphorylation of the RLC alters the "interacting head motif" of myosin motor heads on the thick filament surface, with myriad consequences for muscle biology. At rest, structure-function changes may upregulate actomyosin ATPase activity of phosphorylated cross-bridges. During activation, these same changes may increase the Ca2+ sensitivity of force development to enhance force, work, and power output, outcomes known as "potentiation." Thus, although other mechanisms may contribute, RLC phosphorylation may represent a form of thick filament activation that provides a "molecular memory" of contraction. The clinical significance of these RLC phosphorylation mediated alterations to contractile performance of various striated muscle systems are just beginning to be understood. © 2017 American Physiological Society. Compr Physiol 7:171-212, 2017.
Topics: Animals; Humans; Muscle Contraction; Muscle, Skeletal; Myosins; Phosphorylation
PubMed: 28135003
DOI: 10.1002/cphy.c150044 -
Molecular & Cellular Proteomics : MCP Oct 2022Myosin and myosin-binding protein C are exquisitely organized into giant filamentous macromolecular complexes within cardiac muscle sarcomeres, yet these proteins must...
Myosin and myosin-binding protein C are exquisitely organized into giant filamentous macromolecular complexes within cardiac muscle sarcomeres, yet these proteins must be continually replaced to maintain contractile fidelity. The overall hypothesis that myosin filament structure is dynamic and allows for the stochastic replacement of individual components was tested in vivo, using a combination of mass spectrometry- and fluorescence-based proteomic techniques. Adult mice were fed a diet that marked all newly synthesized proteins with a stable isotope-labeled amino acid. The abundance of unlabeled and labeled proteins was quantified by high-resolution mass spectrometry over an 8-week period. The rates of change in the abundance of these proteins were well described by analytical models in which protein synthesis defined stoichiometry and protein degradation was governed by the stochastic selection of individual molecules. To test whether the whole myosin filaments or the individual components were selected for replacement, cardiac muscle was chemically skinned to remove the cellular membrane and myosin filaments were solubilized with ionic solutions. The composition of the filamentous and soluble fractions was quantified by mass spectrometry, and filament depolymerization was visualized by real-time fluorescence microscopy. Myosin molecules were preferentially extracted from ends of the filaments in the presence of the ionic solutions, and there was only a slight bias in the abundance of unlabeled molecules toward the innermost region on the myosin filaments. These data demonstrate for the first time that the newly synthesized myosin and myosin-binding protein C molecules are randomly mixed into preexisting thick filaments in vivo and the rate of mixing may not be equivalent along the length of the thick filament. These data collectively support a new model of cardiac myosin filament structure, with the filaments being dynamic macromolecular assemblies that allow for replacement of their components, rather than rigid bodies.
Topics: Mice; Animals; Cardiac Myosins; Proteomics; Myosins; Macromolecular Substances; Amino Acids
PubMed: 35921914
DOI: 10.1016/j.mcpro.2022.100274 -
The Journal of Clinical Investigation Mar 2022Myosin modulators are a novel class of pharmaceutical agents that are being developed to treat patients with a range of cardiomyopathies. The therapeutic goal of these... (Review)
Review
Myosin modulators are a novel class of pharmaceutical agents that are being developed to treat patients with a range of cardiomyopathies. The therapeutic goal of these drugs is to target cardiac myosins directly to modulate contractility and cardiac power output to alleviate symptoms that lead to heart failure and arrhythmias, without altering calcium signaling. In this Review, we discuss two classes of drugs that have been developed to either activate (omecamtiv mecarbil) or inhibit (mavacamten) cardiac contractility by binding to β-cardiac myosin (MYH7). We discuss progress in understanding the mechanisms by which the drugs alter myosin mechanochemistry, and we provide an appraisal of the results from clinical trials of these drugs, with consideration for the importance of disease heterogeneity and genetic etiology for predicting treatment benefit.
Topics: Cardiac Myosins; Cardiomyopathies; Heart Failure; Humans; Myocardial Contraction; Myosins; Urea
PubMed: 35229734
DOI: 10.1172/JCI148557 -
Advances in Experimental Medicine and... 2020High-speed atomic force microscopy (HS-AFM) is a unique tool that enables imaging of protein molecules during their functional activity at sub-100 ms temporal and... (Review)
Review
High-speed atomic force microscopy (HS-AFM) is a unique tool that enables imaging of protein molecules during their functional activity at sub-100 ms temporal and submolecular spatial resolution. HS-AFM is suited for the study of highly dynamic proteins, including myosin motors. HS-AFM images of myosin V walking on actin filaments provide irrefutable evidence for the swinging lever arm motion propelling the molecule forward. Moreover, molecular behaviors that have not been noticed before are also displayed on the AFM movies. This chapter describes the principle, underlying techniques and performance of HS-AFM, filmed images of myosin V, and mechanistic insights into myosin motility provided from the filmed images.
Topics: Microscopy, Atomic Force; Movement; Myosins
PubMed: 32451858
DOI: 10.1007/978-3-030-38062-5_7 -
Nature Communications Feb 2022The contractile properties of adult myofibers are shaped by their Myosin heavy chain isoform content. Here, we identify by snATAC-seq a 42 kb super-enhancer at the...
The contractile properties of adult myofibers are shaped by their Myosin heavy chain isoform content. Here, we identify by snATAC-seq a 42 kb super-enhancer at the locus regrouping the fast Myosin genes. By 4C-seq we show that active fast Myosin promoters interact with this super-enhancer by DNA looping, leading to the activation of a single promoter per nucleus. A rainbow mouse transgenic model of the locus including the super-enhancer recapitulates the endogenous spatio-temporal expression of adult fast Myosin genes. In situ deletion of the super-enhancer by CRISPR/Cas9 editing demonstrates its major role in the control of associated fast Myosin genes, and deletion of two fast Myosin genes at the locus reveals an active competition of the promoters for the shared super-enhancer. Last, by disrupting the organization of fast Myosin, we uncover positional heterogeneity within limb skeletal muscles that may underlie selective muscle susceptibility to damage in certain myopathies.
Topics: Animals; Mice; Mice, Transgenic; Muscle Fibers, Skeletal; Muscle, Skeletal; Myosin Heavy Chains; Myosins; Phenotype
PubMed: 35210422
DOI: 10.1038/s41467-022-28666-1 -
Histology and Histopathology Jun 2022The contractile and metabolic properties of skeletal muscles depend on the composition of muscle fibers. There are two major fiber types: type 1 and type 2. Type 2... (Review)
Review
The contractile and metabolic properties of skeletal muscles depend on the composition of muscle fibers. There are two major fiber types: type 1 and type 2. Type 2 fibers are further subdivided into type 2A, 2X, and 2B fibers. Muscle fiber type composition is an important property that affects sports performance and metabolic ability in humans, and meat quality in domestic animals. In this review, we summarize the history of muscle fiber type classification based on various staining methods for skeletal muscle sections. The history illustrates the development of an experimental method to detect myosin heavy chain (MyHC) proteins, which are the most common marker molecules for muscle fiber type. Metabolic enzymes, such as nicotinamide adenine dinucleotide-tetrazolium reductase and succinate dehydrogenase are also described for histochemical staining combined with myosin ATPase staining. We found an improvement in the quality of antibodies used for immunostaining of MyHC, from polyclonal antibodies to monoclonal antibodies (mAbs) and then to mAbs produced by synthetic peptides as antigens. We believe that the information presented herein will assist researchers in selecting optimal staining methods, dependent on the experimental conditions and purposes.
Topics: Animals; Antibodies, Monoclonal; Immunohistochemistry; Muscle Fibers, Skeletal; Muscle, Skeletal; Myosin Heavy Chains; Myosins; Staining and Labeling
PubMed: 35043970
DOI: 10.14670/HH-18-422