Muscle Fibre Stress in Response to Exercise

Abstract

Heat-shock or stress proteins (HSPs) are considered to play an essential role in protecting cells from stress and preparing them to survive new environmental challenges. This study investigates the induction kinetics of synthesis and accumulation of 70-kDa stress proteins in the soleus and extensor digitorum longus (EDL) muscles of the rat following exercise, as well as the isoform transitions that take place during the post-exercise period. Relative synthesis rates (referred to constitutively expressed stress protein HSP73) of the 70-kDa heat-shock proteins were greatly enhanced after a single bout of exercise in both muscles. They peaked early in the post-exercise period and returned to resting levels after approximately 5-6 h. The levels of the inducible stress protein HSP72 in the EDL rose only transiently following exercise, while its accumulation in the soleus was more continuous and stable. The amount of HSP73 increased only transiently in both muscle types after exercise. The constitutive expression of the stress protein HSP72 in the soleus muscle was much higher than in the EDL and other tissues, while that of HSP73 was relatively constant among tissues. Rat skeletal muscle HSP72 and HSP73 were made up of at least three isoforms of the same molecular mass and very close isoelectric points, although only one radiolabelled isoform was detected. The relative proportion of the most abundant isoforms of HSP72, isoforms 1 and 2, as well as their ratio (isoform 2hoform l), increased during the post-exercise period. Since isoform 2 of HSP72 partially disappeared after incubating soleus muscle extracts of exercised rats with alkaline phosphatase, these data indicate that phosphorylation of HSP72 is an early event in the stress response of skeletal muscle to exercise stress.Keywords: heat-shock protein ; exercise ; skeletal muscle ; protein phosphorylation.Cells from all organisms studied thus far experience a stress response when subjected to high temperatures or other environmental challenges. This response is characterized by the induction of the synthesis of a group of proteins known as heat-shock or stress proteins (for a review see [ l , 21). In mammalian cells, the most highly induced proteins of the cellular stress response are the components of the protein family of 70 kDa, a group of closely related proteins that includes HSP72, HSP73, GRP78 and GRP75. All of them share the common property of binding ATP but have a different subcellular distribution within the cell [3, 41. HSP72 and HSP73 have been located within the cytoplasm and nucleus ; HSP73 is constitutively expressed while HSP72 is usually synthesized in response to stress. GRP78 is located in the lumen of the endoplasmic reticulum where it is expressed constitutively at a basal level and is induced by various factors that stress this cellular compartment. GRP78 binds Correspondence to R. Manso, Departamento de Biologia Molecular, Centro de Biologia Molecular 'Severo Ochoa' , Universidad Aut6noma de Madrid, Canto Blanco, E-28049 Madrid, SpainAbbr...

Regulation of survival gene hsp70

“…ATPase activity results in the transient autophosphorylation of Hsp70 protein (McCarty and Walker 1991; Wu et al 2004). Enhanced Hsp70 protein expression has been observed with concomitant elevation in its phosphorylated state early after exercise in skeletal (Hernando and Manso 1997) and cardiac muscles (Melling et al 2009). Hsp70 protein can be phosphorylated in vitro by cAMP-dependent protein kinase (PKA), inhibiting its ability to enhance calcineurin activity (Lakshmikuttyamma et al 2004).…”

Influences of temperature, oxidative stress, and phosphorylation on binding of heat shock proteins in skeletal muscle fibers

“…oxidation; stress response; skinned fiber; chaperones HEAT SHOCK PROTEINS (HSPs) are highly conserved and ubiquitously expressed proteins that act as protein chaperones and in stress situations bind and interact with various proteins to help preserve or restore their function (23,32). A great deal of work in skeletal muscle has focused on the increase in HSP protein and/or mRNA expression levels occurring in hours to days after various stressful stimuli, such as eccentric exercise (11,17,26,27,39), oxidative stress (50), heat (4,35), and glycogen depletion (12). The present study focuses instead on the acute responses of HSPs to stresses, examining the effects of heat, contraction, and oxidative stress on the distribution and binding of three important HSPs present in rat skeletal muscle fibers, namely ␣B-crystallin, HSP25 (also known as HSP27), and HSP72 (also known as HSP70).…”

Inhibitory Effect of a Combination of Thermotherapy with Exercise Therapy on Progression of Muscle Atrophy

“…The induction of HSP expression by exercise and other physical stresses in experiments 11,12) has also been reported. In these experiments, rats ran on a treadmill once a day at a speed of 27-30 m/min for 60-90 minutes, a relatively high exercise intensity over a relatively long time.…”