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RESEARCH PRODUCT

Exercise-Induced Activation and Translocation of αB-Crystallin in Skeletal Muscle Depends upon Fiber Type and Oxidative Stress

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Alpha B-crystallin (CRYAB) is a member of the small heat shock proteins implicated in various biological functions, particularly in skeletal muscle tissue [1], where it results to be modulated following exercise-induced reactive oxygen species (ROS) [2]. In this work we aimed to analyse the CRYAB response to acute exercise with respect muscle fiber composition and to identify the underlying molecular mechanism by the utilization of the C2C12 “in vitro” cellular model. Our results highlighted as acute exercise determines a specific increase of phospho-CRYAB both in the red, but not white, gastrocnemius (GS), with an higher amount of oxidative and oxidative-glycolytic fibers, and in soleus (SOL), mainly composed of fibers Ia and IIa/x. Confocal microscopy analysis showed a localization of pCRYAB only at cytoskeletal level of these fibers. Moreover, pCRYAB activazion was correlated with increased level of 4-hydroxynonenal (HNE) with absence of apoptotic activation, suggesting a putative role of mild oxidative stress in pCRYAB protective response [3, 4]. H 2 O 2- treatment of C2C12 myotubes, whose MHC composition resembles the Ia-IIa/x fibers, confirmed that the ROS-dependent pCRYAB activation was paralleled by the upregulation of ROCK1 and ROCK2, two serine/threonine kinases known to mediate the cytoskeletal stability. We hypothesize that the activation of CRYAB and the subsequent stabilization of the cytoskeleton might represent a specific adaptive response of skeletal muscle oxidative fibers to exercise. References [1] Mercatelli N, et al. Free Radic Biol Med. 2010 Vol. 49(3):374-82. [2] Dimauro I, et al. Free Radic Biol Med. 2016 Vol. 98:46-55. [3] Dimauro I, et al. Free Radic Biol Med. 2012 Vol. 53(11):2017-27. [4] Fittipaldi S, et al. Free Radic Biol Med. 2014 Vol. 48(1):52-70