The heat-shock response: regulation and function of heat-shock proteins and molecular chaperones.

Exposure of cells to stresses such as heat shock, oxidant injury and heavy metals causes an imbalance in protein metabolism which challenges the cell to respond rapidly, yet precisely, to minimize the deleterious effects of environmental and physiological stress. The heat-shock response, through the activation of HSFs, results in the elevated expression of heat-shock genes and the concomitant synthesis of HSPs and molecular chaperones. Molecular chaperones function in a variety of protein biosynthetic events and protect proteins from the deleterious effects of acute or chronic stress by stabilizing and refolding protein-folding intermediates or facilitating protein degradation. The accumulation of misfolded proteins has also become a central issue to diseases of protein folding, including sickle cell haemoglobin, cystic fibrosis and prion diseases, in addition to complex multifactorial diseases such as bacterial and viral infections, myocardial ischaemia, neurodegenerative diseases and cancer.