1962-2007: a cell stress odyssey.

The induction of a cellular stress response was first observed in 1962 in a set of serendipitous experiments in Drosophila melanogasterlarvae, which led to the discovery of a family of intracellular polypeptides known as heat shock proteins (HSPs). These highly conserved proteins are present in both prokaryotic and eukaryotic species, suggesting that they play important roles in fundamental cellular processes. Moreover, these proteins are induced in response to a range of stimuli, implicating HSPs as important modifying factors in an organism's response to a variety of physiological conditions. HSPs were initially regarded as intracellular molecules mediating cytoprotective, regulatory and chaperoning functions. However, the past two decades have seen an explosion of information related to the cell stress response, with a primary focus on molecular chaperones, which are a class of multifunctional intracellular proteins that assist in folding and assembly of other proteins. Stress proteins have also been identified on cell surfaces and in extracellular fluids, and are now viewed as potential immunomodulators, pro-inflammatory signalling molecules, and anti-inflammatory proteins in disease states. This chapter serves as an overview of the rapidly expanding world of cell stress proteins and aims to provide the reader with a foundation for more detailed presentations in subsequent sections of this book.