Changes in skeletal muscle heat shock proteins: pathological significance

In response to stress, cells rapidly produce a series of new proteins known as heat shock proteins (HSP). HSPs are considered to be molecular chaperones which play a universal role in maintaining cellular homeostasis. It is known that different HSPs are expressed in skeletal muscle, namely, small HSPs (including ubiquitin, alpha B- crystallin, HSP20 and HSP 27), HSP70, HSP60 and HSP90. Skeletal muscle is a complex and heterogeneous system in that its contractile proteins are made of different isoforms to form various muscle fibre types, and each type of muscle fibre has its own histochemical and functional characteristics. It seems that the induction of HSPs differs with muscle fibre type suggesting HSP expression is muscle fibre type specific. HSPs have been shown to respond in muscle diseases and following exercise. However, the molecular mechanisms of HSP induction, regulation and its role in maintaining the muscle function, are not completely understood. Relatively few studies of HSP have been conducted in human skeletal muscles. This review discusses the significance of changes of HSPs in skeletal muscle in both physiological and pathological conditions.