Abstract
HSPB5 or alpha B-crystallin (CRYAB), originally identified as lens protein, is one of the most widespread and represented of the human small heat shock proteins (sHSPs). It is greatly expressed in tissue with high rates of oxidative metabolism, such as skeletal and cardiac muscles, where HSPB5 dysfunction is associated with a plethora of human diseases. Since HSPB5 has a major role in protecting muscle tissues from the alterations of protein stability (i.e., microfilaments, microtubules, and intermediate filament components), it is not surprising that this sHSP is specifically modulated by exercise. Considering the robust content and the protective function of HSPB5 in striated muscle tissues, as well as its specific response to muscle contraction, it is then realistic to predict a specific role for exercise-induced modulation of HSPB5 in the prevention of muscle diseases caused by protein misfolding. After offering an overview of the current knowledge on HSPB5 structure and function in muscle, this review aims to introduce the reader to the capacity that different exercise modalities have to induce and/or activate HSPB5 to levels sufficient to confer protection, with the potential to prevent or delay skeletal and cardiac muscle disorders.
Highlights
Organisms, to reduce their susceptibility to various stress conditions such as environmental, metabolic, or pathophysiological stress, have developed adaptive protective mechanisms to maintain or re-establish cellular homeostasis [1]
It cannot be excluded that the contraction-induced benefits result from an additive effect of multiple pathways induced by physical exercise, the experimental data collected so far suggest that the modulation of HSPB5 exerted by non-damaging concentric or eccentric muscle contractions may contribute to the protection against skeletal and cardiac muscle weakness by preserving myofibrillar structure and function as well as protecting against oxidative stress insults [175]
In addition to its chaperon activity in preventing protein aggregation, it is clear that in both skeletal and cardiac tissues, HSPB5 prevents cell death induced by oxidative stress and other cytotoxic stimuli, counteracts the disruption of cytoskeletal assembly, and inhibits inflammation
Summary
To reduce their susceptibility to various stress conditions such as environmental, metabolic, or pathophysiological stress, have developed adaptive protective mechanisms to maintain or re-establish cellular homeostasis [1]. HSPs display different functions depending on tissue specific localization, intra-or extracellular distribution, developmental expression, and level of induction and interaction with the target protein Based on their approximate molecular mass, and as suggested by Kampinga and colleagues (2008) in their new guidelines for the nomenclature of human HSP families, there have been identified five major and broadly conserved families, namely HSPH (Hsp110s), HSPC (Hsp90s), HSPA (Hsp70s), HSPD (Hsp60s), DNAJ (Hsp40s), and small heat shock proteins (sHSPs) [3]. Information on the human HSPB structure and function has mainly been based on cell free in vitro data and on cell biological data with the stress-inducible human HSPB1 and HSPB5 or HSP members from other organisms These data show that HSPB members can act to block the aggregation of un- or misfolded proteins, and that they can protect cytoskeletal integrity or assist in cytoskeletal recovery upon stress, both functions potentially contributing to the increased survival of cells when exposed to stress conditions that hamper protein homeostasis and/or disrupt the cytoskeleton [12]. We report what is known to date about the modulation of HSPB5 following physical activity/exercise and how this response may have the potential to prevent or delay skeletal and cardiac muscle disorders caused by protein misfolding
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