Shenkman B S
State Scientific Center of the Russian Federation - Institute of Biomedical Problems, Russian Academy of Sciences, Khoroshevskoe shosse, 76A, Moscow, 123007, Russia.
Acta Naturae. 2016 Oct-Dec;8(4):47-59.
Skeletal muscle consists of different fiber types arranged in a mosaic pattern. These fiber types are characterized by specific functional properties. Slow-type fibers demonstrate a high level of fatigue resistance and prolonged contraction duration, but decreased maximum contraction force and velocity. Fast-type fibers demonstrate high contraction force and velocity, but profound fatigability. During the last decades, it has been discovered that all these properties are determined by the predominance of slow or fast myosin-heavy-chain (MyHC) isoforms. It was observed that gravitational unloading during space missions and simulated microgravity in ground-based experiments leads to the transformation of some slow-twitch muscle fibers into fast-twitch ones due to changes in the patterns of MyHC gene expression in the postural . The present review covers the facts and mechanistic speculations regarding myosin phenotype remodeling under conditions of gravitational unloading. The review considers the neuronal mechanisms of muscle fiber control and molecular mechanisms of regulation of myosin gene expression, such as inhibition of the calcineurin/NFATc1 signaling pathway, epigenomic changes, and the behavior of specific microRNAs. In the final portion of the review, we discuss the adaptive role of myosin phenotype transformations.
骨骼肌由以镶嵌模式排列的不同纤维类型组成。这些纤维类型具有特定的功能特性。慢肌纤维表现出高水平的抗疲劳能力和延长的收缩持续时间，但最大收缩力和速度降低。快肌纤维表现出高收缩力和速度，但极易疲劳。在过去几十年中，人们发现所有这些特性都由慢或快肌球蛋白重链（MyHC）同工型的优势决定。据观察，太空任务期间的重力卸载以及地面实验中的模拟微重力会导致一些慢肌纤维由于姿势肌中MyHC基因表达模式的变化而转变为快肌纤维。本综述涵盖了关于重力卸载条件下肌球蛋白表型重塑的事实和机制推测。该综述考虑了肌纤维控制的神经元机制以及肌球蛋白基因表达的调控分子机制，如钙调神经磷酸酶/NFATc1信号通路的抑制、表观基因组变化和特定微小RNA的行为。在综述的最后部分，我们讨论了肌球蛋白表型转变的适应性作用。
