Heat shock proteins (HSPs) are a group of highly conserved stress response proteins which primarily function as molecular chaperones, and are involved in a variety of biological processes including thermotolerance, inhibition of apoptosis, regulation of cell development and cell differentiation, as well as signal transduction.
HSP27, also known as HSP beta-1 (HSPB1), is a chaperone of the sHSP (small heat shock protein) group. It appears in many cell types, especially all types of muscle cells. It is overexpressed during different stages of cell differentiation and development. HSP27 is involved in the apoptotic signalling pathway and inhibits the activation of procaspase-9. Furthermore, HSP27 also exerts functions in protecting actin filaments from fragmentation and the activation of the proteasome. HSP27 could be a potential diagnostic marker. High levels of HSP27 were also found in sera of breast cancer patients. Phosphorylated HSP27 increases human prostate cancer cell invasion, enhances cell proliferation, and suppresses Fas-induced apoptosis.