Many heritable and acquired human diseases result from production of misfolded proteins due to mutations or extreme stress conditions, which disrupt numerous cellular metabolic processes and culminate in cell death. As a defense strategy, cells respond to these stresses by rapidly synthesizing heat shock or stress proteins (hsps), which repair or degrade damaged proteins. The inducible hsp7O subfamily, which contains two phylogenetically conserved members (hsp7O.1 and hsp7O.3) in mice, is unique in its function. These proteins act as molecular chaperones and prevent aggregation of misfolded proteins; they also assist in the refolding, transport, and assembly of proteins in the cytoplasm, mitochondria and endoplasmic reticulum. There is widespread clinical interest in hsp7O chaperone function in a number of human pathologies including cancer, neurodegenerative conditions, aging, and cardiovascular diseases. However, efforts to understand the functional roles of stress-inducible hsp7Os in vivo have been hampered by a lack of experimental models. To this effect, we have generated mice deficient in hsp7O by replacing the entire coding region of the hsp7O.1 or hsp70.3 gene with an in frame b-galactosidase gene sequence. These mutant mice offer an unique opportunity to study in an animal model the regulation of inducible hsp70, and allow for studies of it's function in clinically significant states such as cancer, ischemia, hyperthermia, inflammation, vascular hypertrophy, and oxidative stress.
The specific aims of this proposal are: (1) To study transcriptional regulation of the hsp7O.1 or hsp70.3 genes during development and in adult tissues under normal and environmental stress conditions. (2) To analyze the function of the hsp70. 1 or hsp70.3 genes in maintenance of tolerance in vivo to thermal stress and to define their contribution to inflammation, protection from ischemia, and tumor cell survival. (3) To examine whether the function of inducible hsp70 in acquired thermotolerance and protection from stress situations such as radiation and ischemia, during development and in adult is indispensable and cannot be compensated by other related members of the hsp family. Here studies are proposed on mutant mice completely devoid of inducible hsp70 expression (deficient in both hsp70. 1 and hsp7o.3 genes). The proposed studies will help us achieve a better understanding of the fundamental cellular processes in which hsp70 molecular chaperones engage to respond to environmental stresses, as well as to determine their role in clinically relevant pathologies in humans.
