Stress-Induced Expression of HSP70 in Mammalian Tissues. The goals of this proposal are to determine the mechanism(s) supporting the induction of the 70 kilodalton Heat Shock Protein (HSP70) in mammalian tissues and the function of these proteins in physiologic stress responses. These goals are derived from the original observations that: 1) Heat stress induces the selective expression of HSP70 in brain areas coordinating neuroendocrine stress responses; 2) Heat stress induces HSP70 expression in adrenal cortex but not adrenal medulla; 2) Restraint stress, in the absence of heat, also induces HSP70 expression in adrenal cortex as well as in vascular tissue. Based on these observations, it is hypothesized that HSP70 can be induced in mammalian tissues by hormones and/or neurotransmitters subsequent to activation of the hypothalamic-pituitary- adrenal (HPA) axis and the sympathetic nervous system where it functions to facilitate the biochemical and molecular actions of these stress response systems. This hypothesis will be tested by the following specific aims: SA1) Determine the cellular and molecular basis for the selective induction of HSP70 expression in the adrenal by comparing the activation of heat shock transcriptional factors between the cortex and medulla; SA2) Determine the signal transduction pathways that mediate restraint-induced HSP70 expression in the adrenal cortex by determining ability of theophylline and cAMP analogs to mimic the effects of restraint; SA3) Determine the function of HSP70 in adrenal cortical cells of restraint-stressed rats by blocking HSP70 expression with antisense oligonucleotides then assessing the effects of this blockade on steroid hormone synthesis; and SA4) Identify the receptor populations and molecular mechanisms supporting HSP70 induction in the aorta by determining the effects of several adrenergic receptor ligands on restraint-induced expression. Our current knowledge of HSP function is derived largely from studies in cultured cells. Few investigations have utilized in vivo stress models to address HSP function in mammalian systems where their induction may have unique effects on physiologic processes. Using a combination of heat stress and restraint stress this application seeks to determine the relationship between this highly conserved cellular stress response and mammalian stress response systems. Already, results from this line of investigation have identified HSP70 as an important player in the classic HPA response to stress while restraint-induced expression in the aorta suggests HSP70 also plays a salient role in cardiovascular stress. Investigations into HSP70 expression in mammalian tissues provides a novel approach to understanding the cellular and molecular mechanisms underlying physiologic stress responses.
