Myosin and adenosinetriphosphatase

Recent Advances in Molecular and Cellular Functions of S100A10

S100A10 (p11, annexin II light chain, calpactin light chain) is a multifunctional protein with a wide range of physiological activity. S100A10 is unique among the S100 family members of proteins since it does not bind to Ca2+, despite its sequence and structural similarity. This review focuses on studies highlighting the structure, regulation, and binding partners of S100A10. The binding partners of S100A10 were collated and summarized.

Widely cited publications of Michael Bárány in 1964 and 1967 as tipping points in understanding myosin molecular motors

In 1964 Michael Bárány and colleagues published a paper ((M. Bárány, E. Gaetjens, K. Bárány, Karp E. Arch Biochem Biophys 106(1964)280-93. http://10.1016/0003-9861(64)90,189-4)) that has been one of the most cited papers in Archives of Biochemistry and Biophysics. This was followed in 1967 by another most cited paper (M. Bárány. J Gen Physiol 50(1967)197-218. https://doi.org/10.1085/jgp.50.6.197). I have commemorated these achievements as tipping points in the understanding of myosin motors in muscle function. Tipping points are generally defined as a temporal point in which a series of progressive advances (in this case the understanding of the relations between myosin ATP hydrolysis and muscle function) inspire more expansive, wide-ranging, significant changes. I first concisely summarize the background against which the papers came to publication as well as the unimaginable personal challenges faced by Michael and Kate Bárány. A final section summarizes the impact of these publications as key steps in the progression of contemporary understanding of diverse control of myosin ATPase activity with focus on the thick filaments in cardiac homeostasis, disorders, and as targets for therapeutic applications in translational investigations.

Genome-Wide Identification, Characterization and Expression Profiling of myosin Family Genes in Sebastes schlegelii

Myosins are important eukaryotic motor proteins that bind actin and utilize the energy of ATP hydrolysis to perform a broad range of functions such as muscle contraction, cell migration, cytokinesis, and intracellular trafficking. However, the characterization and function of myosin is poorly studied in teleost fish. In this study, we identified 60 myosin family genes in a marine teleost, black rockfish (Sebastes schlegelii), and further characterized their expression patterns. myosin showed divergent expression patterns in adult tissues, indicating they are involved in different types and compositions of muscle fibers. Among 12 subfamilies, S. schlegelii myo2 subfamily was significantly expanded, which was driven by tandem duplication events. The up-regulation of five representative genes of myo2 in the skeletal muscle during fast-growth stages of juvenile and adult S. schlegelii revealed their active role in skeletal muscle fiber synthesis. Moreover, the expression regulation of myosin during the process of myoblast differentiation in vitro suggested that they contribute to skeletal muscle growth by involvement of both myoblast proliferation and differentiation. Taken together, our work characterized myosin genes systemically and demonstrated their diverse functions in a marine teleost species. This lays foundation for the further studies of muscle growth regulation and molecular mechanisms of indeterminate skeletal muscle growth of large teleost fishes.

Genome-wide identification and characterization of myosin genes in the silkworm, Bombyx mori

Myosins are a large family of actin filament-based motor proteins with a broad range of functions such as intracellular membrane trafficking, endocytosis, exocytosis, organellar transport, growth cone motility, cytokinesis, and cell locomotion. They are found in many organisms from fungi to humans. The myosin gene family in Bombyx mori is poorly studied, even though the molecular functions of these genes in vertebrates and insects, such as Drosophila, are well known. We identified 16 myosin genes from B. mori and identified the myosin genes in 12 vertebrates, eight insects, three nematodes, and seven protozoa. The number of myosin genes in vertebrates is double the number in invertebrates. The number of myosin isoforms in classes I and II is larger in vertebrates compared to invertebrates. B. mori myosin genes can be classified into 11 classes. Compared to B. mori, some myosin classes are not present in other insects. Classes I, II, XVIII, and XXI appear to be important for insect survival because they are conserved among nine insects. The relatively large sizes of B. mori myosin genes are due to their longer introns. Reverse transcription PCR (RT-PCR) and quantitative real-time PCR (qRT-PCR) analysis demonstrated that many B. mori myosin genes have tissue-specific expression and exhibit temporal-specific activity during metamorphosis. These data provide insights into evolutionary and functional aspects of B. mori myosin genes that could be useful for the study of homologous myosins in other Lepidoptera species.

The Concentration of Adenosinetriphosphate (ATP) Citrate and Calcium in Blood During Insulin Shock Therapy

Concentration changes of blood constituents other than glucose occurring during hypoglycaemia, and particularly during insulin shock therapy, have been studied by several authors (e.g., Harris, Blalock and Horwitz, 1938; Katzenelbogen et al., 1939) though not always with concordant results. One of the most constant features of insulin hypoglycaemia is a decrease in the level of inorganic phosphate during the phase of blood-sugar fall and a gradual return to normal after the blood-sugar curve has reached its lowest value. This fact which was described soon after the discovery of insulin (see Cori (1931) for a review of the older literature) is generally attributed to the increased phosphate esterification consequent upon the enhancement of glucose utilisation and is in harmony with the current concept that the function of insulin is primarily that of a promotor of glucose phosphorylation.

Thin Filament Structure and the Steric Blocking Model

By interacting with the troponin-tropomyosin complex on myofibrillar thin filaments, Ca2+ and myosin govern the regulatory switching processes influencing contractile activity of mammalian cardiac and skeletal muscles. A possible explanation of the roles played by Ca2+ and myosin emerged in the early 1970s when a compelling "steric model" began to gain traction as a likely mechanism accounting for muscle regulation. In its most simple form, the model holds that, under the control of Ca2+ binding to troponin and myosin binding to actin, tropomyosin strands running along thin filaments either block myosin-binding sites on actin when muscles are relaxed or move away from them when muscles are activated. Evidence for the steric model was initially based on interpretation of subtle changes observed in X-ray fiber diffraction patterns of intact skeletal muscle preparations. Over the past 25 years, electron microscopy coupled with three-dimensional reconstruction directly resolved thin filament organization under many experimental conditions and at increasingly higher resolution. At low-Ca2+, tropomyosin was shown to occupy a "blocked-state" position on the filament, and switched-on in a two-step process, involving first a movement of tropomyosin away from the majority of the myosin-binding site as Ca2+ binds to troponin and then a further movement to fully expose the site when small numbers of myosin heads bind to actin. In this contribution, basic information on Ca2+-regulation of muscle contraction is provided. A description is then given relating the voyage of discovery taken to arrive at the present understanding of the steric regulatory model.

Historical perspective on heart function: the Frank-Starling Law

More than a century of research on the Frank-Starling Law has significantly advanced our knowledge about the working heart. The Frank-Starling Law mandates that the heart is able to match cardiac ejection to the dynamic changes occurring in ventricular filling and thereby regulates ventricular contraction and ejection. Significant efforts have been attempted to identify a common fundamental basis for the Frank-Starling heart and, although a unifying idea has still to come forth, there is mounting evidence of a direct relationship between length changes in individual constituents (cardiomyocytes) and their sensitivity to Ca²⁺ ions. As the Frank-Starling Law is a vital event for the healthy heart, it is of utmost importance to understand its mechanical basis in order to optimize and organize therapeutic strategies to rescue the failing human heart. The present review is a historic perspective on cardiac muscle function. We "revive" a century of scientific research on the heart's fundamental protein constituents (contractile proteins), to their assemblies in the muscle (the sarcomeres), culminating in a thorough overview of the several synergistically events that compose the Frank-Starling mechanism. It is the authors' personal beliefs that much can be gained by understanding the Frank-Starling relationship at the cellular and whole organ level, so that we can finally, in this century, tackle the pathophysiologic mechanisms underlying heart failure.

Studies on the mechanism of action of ionizing radiations; inhibition of enzymes by X-rays

Dilute solutions of sulfhydryl enzymes (phosphoglyceraldehyde dehydrogenase, adenosinetriphosphatase, succinoxidase) showed reduced activity on irradiation by small amounts of x-rays. When the inhibition was partial the enzyme was reactivated on addition of glutathione. When the inhibition was more complete, reactivation was only partial. These observations are interpreted as being due to oxidation of the —SH groups of the protein by the products of water irradiation, the radicals OH and O₂H, and H₂O₂ and atomic oxygen. The irreversible inhibition which occurs when the dose of x-rays is increased is attributed to protein denaturation. Inhibition of the non-sulfhydryl enzymes trypsin, catalase, and ribonuclease, which required larger amounts of x-rays, is attributed to protein denaturation. These experiments are further evidence that inhibition of enzymes by ionizing radiations is due to the indirect action of the products of irradiated water rather than to direct ionization of the enzyme through collision with the ionizing radiation.

Studies on the mechanism of action of ionizing radiations; inhibition of sulfhydryl enzymes by alpha, beta, and gamma rays

The activity of crystalline phosphoglyceraldehyde dehydrogenase and urease was decreased when dilute solutions of these sulfhydryl enzymes were irradiated with small doses of alpha rays from Po, beta rays from Si⁸⁹, and gamma rays from Ra. Partial reactivation of the enzyme by addition of glutathione was obtained after inhibition with alpha rays. Evidence that these inhibitions are due to oxidation of the —SH groups of the enzymes was given by the irradiation of the mercury-mercaptide urease with gamma rays. This irradiated complex was completely reactivated by glutathione as was the non-irradiated enzyme. The ionic efficiency of all these ionizing radiations on inhibition of phosphoglyceraldehyde dehydrogenase was similar (ionic yield around 1). The sulfhydryl groups of crystalline phosphoglyceraldehyde dehydrogenase were titrated by enzyme activity measurements and by ferricyanide oxidation.

Unconventional myosins in muscle

Myosins, actin-based molecular motors originally isolated from muscle tissues, are ubiquitously expressed in all eukaryotic cells. They are involved in a panoply of cellular functions, including cell migration, intracellular trafficking, adhesion, and cytokinesis. Several unconventional myosins belonging to classes I, V, VI, VII, IX, and XVIII have been detected in myogenic cells and/or adult muscle where they seem to play important roles in muscle functioning and/or differentiation. For example, a point mutation within the myosin VI gene leads to a cardiac dysfunction, and myosin XVIIIB (expressed predominantly in striated muscle) may be involved in muscle gene transcription. This review summarizes data addressing the functioning of these unconventional myosins in muscle and/or myogenic cells.

Calcium signaling phenomena in heart diseases: a perspective

Ca(2+) is a major intracellular messenger and nature has evolved multiple mechanisms to regulate free intracellular (Ca(2+))(i) level in situ. The Ca(2+) signal inducing contraction in cardiac muscle originates from two sources. Ca(2+) enters the cell through voltage dependent Ca(2+) channels. This Ca(2+) binds to and activates Ca(2+) release channels (ryanodine receptors) of the sarcoplasmic reticulum (SR) through a Ca(2+) induced Ca(2+) release (CICR) process. Entry of Ca(2+) with each contraction requires an equal amount of Ca(2+) extrusion within a single heartbeat to maintain Ca(2+) homeostasis and to ensure relaxation. Cardiac Ca(2+) extrusion mechanisms are mainly contributed by Na(+)/Ca(2+) exchanger and ATP dependent Ca(2+) pump (Ca(2+)-ATPase). These transport systems are important determinants of (Ca(2+))(i) level and cardiac contractility. Altered intracellular Ca(2+) handling importantly contributes to impaired contractility in heart failure. Chronic hyperactivity of the beta-adrenergic signaling pathway results in PKA-hyperphosphorylation of the cardiac RyR/intracellular Ca(2+) release channels. Numerous signaling molecules have been implicated in the development of hypertrophy and failure, including the beta-adrenergic receptor, protein kinase C, Gq, and the down stream effectors such as mitogen activated protein kinases pathways, and the Ca(2+) regulated phosphatase calcineurin. A number of signaling pathways have now been identified that may be key regulators of changes in myocardial structure and function in response to mutations in structural components of the cardiomyocytes. Myocardial structure and signal transduction are now merging into a common field of research that will lead to a more complete understanding of the molecular mechanisms that underlie heart diseases. Recent progress in molecular cardiology makes it possible to envision a new therapeutic approach to heart failure (HF), targeting key molecules involved in intracellular Ca(2+) handling such as RyR, SERCA2a, and PLN. Controlling these molecular functions by different agents have been found to be beneficial in some experimental conditions.

Studies on the rigor resulting from the thawing of frozen frog sartorius muscle

1. The rigor which takes place when completely frozen frog sartorius muscle is thawed ("thaw rigor"), is accompanied by a decrease in length of 70 per cent and a loss in weight of 35 per cent, whether the muscle is frozen in the resting or the exhausted condition, or during isometric tetanus. Muscle tetanized to maximal shortening shows a loss in weight of 25 per cent on thawing. 2. A load of 8 gm. is sufficient to prevent the decrease in length on thawing, but after its removal the muscle will shorten almost to the normal extent. 3. Inhibitors such as azide, cyanide, 2:4 dinitrophenol, p-chloromercuribenzoate, Cu, and hydrogen peroxide, when used for periods not exceeding 1 hour, have little effect on the shortening; although in some cases these poisons render the muscle inexcitable. 4. Muscles poisoned with iodoacetic acid and stimulated to exhaustion, or maintained at fixed length in nitrogen, show little or no shortening on thawing. ATP can produce shortening in the muscles in which it has been prevented. 5. The phenomenon is considered to be due to an in situ synaeresis of the actomyosin of the myofibrils. As a result of the disorganisation of the muscle protoplasm produced by the freezing and subsequent thawing, the ATP, which must be bound or localized in the resting muscle, can act on the myofibril in a similar manner to its in vitro effect on the actomyosin thread.