The 70-kDa heat shock cognate protein (Hsc73) gene is enhanced by ovarian hormones in the ventromedial hypothalamus

Estrogen (E) and progesterone (P) orchestrate many cellular responses invol ved in female reproductive physiology, including reproductive behaviors. E- and P-binding neurons important for lordosis behavior have been located wi thin the ventromedial hypothalamus (VMH), and several hormone-responsive ge nes have been observed there as well. In attempts to identify additional E- and P-responsive genes in the VMH that may contribute to sexual behaviors, we used the differential display mRNA screening technique. One of the gene s identified encodes the 73-kDa heat shock cognate protein (Hsc73), Quantit ative in situ hybridization analysis of brains from naturally cycling femal e rats revealed a significant increase in Hsc73 mRNA in the VMH and arcuate nucleus of animals during proestrus compared with those at diestrus-1. To confirm that these increases were steroid hormone dependent, we compared ve hicle-treated ovariectomized females with ovariectomized females treated,vi th estradiol benzoate and P. Northern analysis and in situ hybridizations s howed that the Hsc73 gene is enhanced by E and P in the pituitary and subre gions of the VMH. Incidentally, by examining the primary amino acid sequenc e of rat, human, and chicken progesterone receptors, we noticed that putati ve Hsc73 binding sites are conserved across species with similar sites exis ting in the androgen and glucocorticoid receptors. Together these findings suggest a possible mechanism through which E could influence the activities of progesterone, androgen, and glucocorticoid receptors, by enhancing the expression of Hsc73 in cells where these proteins colocalize.