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J Appl Physiol (1985). 2019 Mar 28. doi: 10.1152/japplphysiol.01038.2018. [Epub ahead of print]

Phosphorylation of αB-crystallin and its cytoskeleton association differs in skeletal myofiber types depending on resistance exercise intensity and volume.

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Molecular and Cellular Sport Medicine, German Sport University Cologne, Germany.
Sport Science, University of Hildesheim, Germany.
Sports Medicine and Sports Nutrition, Ruhr University of Bochum, Germany.
Department of Molecular and Cellular Sport Medicine, German Sport University Cologne, Germany.
Department of Exercise Science, University of Hildesheim, Germany.


αB-crystallin (CRYAB) is an important actor in the immediate cell stabilizing response following mechanical stress in skeletal muscle. Yet, only little is known regarding myofiber type-specific stress-responses of CRYAB. We investigated whether the phosphorylation of CRYAB at serine 59 (pCRYABSer59) and its cytoskeleton association is influenced by varying load-intensity and -volume in a fiber type-specific manner. Male subjects were assigned to one, five and ten sets of different acute resistance exercise protocols: hypertrophy (HYP); maximum strength (MAX); strength endurance (SE); low intensity (LI) and 3 sets of maximum eccentric resistance exercise (ECC). Skeletal muscle biopsies were taken at baseline and 30 min after exercise. Western blot revealed an increase in pCRYABSer59 only following five and ten sets in groups HYP, MAX, SE, LI and following 3 sets in ECC-group. In type I fibers, immunohistochemistry determined increased pCRYABSer59 in all groups. In type II fibers, pCRYABSer59 only increased in MAX- and ECC-group, with the increase in type II fibers exceeding that of type I fibers in ECC. Association of CRYAB and pCRYABSer59 to the cytoskeleton reflected the fiber type-specific phosphorylation pattern. Phosphorylation of CRYAB and its association to the cytoskeleton in type I and II myofibers is highly specific in terms of loading intensity and volume. Most likely, this is based on specific recruitment-patterns of the different myofiber entities due to the different resistance exercise loadings. We conclude that pCRYABSer59 indicates contraction-induced mechanical stress exposure of single myofibers in consequence of resistance exercise.


fiber types; resistance exercise; skeletal muscle; small heat shock proteins; αB-crystallin

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