Российский физиологический журнал им \xa0И \xa0М \xa0Сеченова | 2021
Как мышечная активность контролирует экспрессию медленного миозина
Abstract
One of the main gravitationally determined functions of the locomotor system is maintaining a vertical pose. These functions, according to the school of Professor I.B. Kozlovskoy are provided by the tonic muscular system. Under the term tonic system I. B. Kozlovskaya understood all structures and regulatory mechanisms capable of maintaining basal mechanical tension (tone) for a long time. In mammals, she attributed slow fibers as fibers with a predominant expression of the slow isoform of myosin heavy chains type I (β) - MyHC I (β) and all the neural mechanisms controlling them to the tonic system. It is clear that the muscle s ability to maintain tonic tension for a long time depends on the intensity of slow myosin expression. Therefore, it would not be a great exaggeration if we call the slow myosin gene myh7 the true muscle tone gene. In recent years, it has generally become clear how, against the background of prolonged increased muscle contractile activity, an increase in the expression of the slow isoform of myosin heavy chains, MyHC I (β), and a decrease in the expression of its fast isoforms are triggered. Much less is known about the mechanisms of the decrease in the expression of MyHC I (β) caused by a decrease in muscle contractile activity. This phenomenon was observed after exposure to real weightlessness, after bedrest, “dry” immersion, and also when using the standard model of rodent hindlimb suspension. Numerous studies of the plasticity of the myosin phenotype, as a rule, are focused on the search for mechanisms that link changes in the expression of myosin genes with the pattern of the contractile activity of muscle fibers. The data discussed in the review indicate that constant expression of slow myosin is controlled by tonic activity and, in turn, is a necessary condition for maintaining such activity. When this activity is significantly reduced or stopped, also stop the metabolic and mechanical stimuli that trigger the signaling pathways activating expression of the myh7 gene. It is this phenomenon that was the subject of discussion in this work.