Predominant synthesis of giant myofibrillar proteins in striated muscles of the long-tailed ground squirrel Urocitellus undulatus during interbout arousal

Svetlana Popova,Nadezda Zakharova,Nikolay Salmov,Yulia Gritsyna,Gulnara Mikhailova,Liya Bobyleva,Ivan Vikhlyantsev,Yana Yutskevich,Anna Ulanova,Oleg Morenkov,Vadim Rogachevsky,Alexander Bobylev

doi:10.1038/s41598-020-72127-y

Abstract

Molecular mechanisms underlying muscle-mass retention during hibernation have been extensively discussed in recent years. This work tested the assumption that protein synthesis hyperactivation during interbout arousal of the long-tailed ground squirrel Urocitellus undulatus should be accompanied by increased calpain-1 activity in striated muscles. Calpain-1 is known to be autolysed and activated in parallel. Western blotting detected increased amounts of autolysed calpain-1 fragments in the heart (1.54-fold, p < 0.05) and m. longissimus dorsi (1.8-fold, p < 0.01) of ground squirrels during interbout arousal. The total protein synthesis rate determined by SUnSET declined 3.67-fold in the heart (p < 0.01) and 2.96-fold in m. longissimus dorsi (p < 0.01) during interbout arousal. The synthesis rates of calpain-1 substrates nebulin and titin in muscles did not differ during interbout arousal from those in active summer animals. A recovery of the volume of m. longissimus dorsi muscle fibres, a trend towards a heart-muscle mass increase and a restoration of the normal titin content (reduced in the muscles during hibernation) were observed. The results indicate that hyperactivation of calpain-1 in striated muscles of long-tailed ground squirrels during interbout arousal is accompanied by predominant synthesis of giant sarcomeric cytoskeleton proteins. These changes may contribute to muscle mass retention during hibernation.

Highlights

Molecular mechanisms underlying muscle-mass retention during hibernation have been extensively discussed in recent years
This research is the first to report on seasonal changes in the total content of calpain-1 and calpastatin in striated muscles of the long-tailed ground squirrel Urocitellus undulatus
This article is the first to communicate an increased autolysis of calpain-1 in striated muscles of a hibernating animal during interbout arousal (Fig. 2). These data are indicative of a hyperactivation of calpain-1 in the heart and m. longissimus dorsi of the long-tailed ground squirrel during this period

Summary

Introduction

Molecular mechanisms underlying muscle-mass retention during hibernation have been extensively discussed in recent years. This work tested the assumption that protein synthesis hyperactivation during interbout arousal of the long-tailed ground squirrel Urocitellus undulatus should be accompanied by increased calpain-1 activity in striated muscles. The results indicate that hyperactivation of calpain-1 in striated muscles of long-tailed ground squirrels during interbout arousal is accompanied by predominant synthesis of giant sarcomeric cytoskeleton proteins. These changes may contribute to muscle mass retention during hibernation. Longissimus dorsi during hibernation[12] For this reason, research into this muscle of the long-tailed ground squirrel may contribute to a better understanding of the molecular mechanisms of muscle-system adaptation in hibernators. In the golden hamster (Mesocricetus auratus)[24] and golden-mantled ground squirrel (Callospermophilus lateralis), the diaphragm and heart are observed to be hypertrophied during h ibernation[25,26,27]

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