Heat shock protein 27 is one of the small HSPs that are constitutively expressed at different levels in various cell types and tissues. HSP27 is a constitutively expressed cytoplasmic protein that co-localizes to the nucleus upon stress induced by insult. Heat, cytokines and hormones are among the factors that stimulate the synthesis of HSP27. In vitro, HSP27 becomes highly phosphorylated following exposure to stress. HSP27 is phosphorylated at Ser15, Ser78, and Ser82 by MAPKAPK-2 as a result of the activation of the p38 MAP kinase pathway. The discovery that HSP27 is regulated by hormones such as estrogen has led to studies establishing a relationship between HSP27 and breast cancer.
