The role of heat shock protein 70 in vitamin D receptor function

We previously demonstrated that the 1 alpha ,25-dihydroxyvitamin D-3 receptor (VDR) interests with the constitutive heat shock protein, hsc70 in vitro and with DnaK (Biochem. Biophys. Res. Commun. 260, 446-152, 1999). The biological significance of VDR-heat shock protein interactions! however, is unknown. To examine the role of such interactions in eukaryotic cells, we heterologously expressed VDR and RXR alpha together with a vitamin D-responsive reporter system in Saccharomyces cerevisiae and examined the consequences of heat shock protein 70 gene (SSA) deletion in these cells. We show that heaerologously expressed VDR associates with the yeast cytosolic hsp79 protein, Ssa1p. Deletion of the SSA2, SSA3, and SSA4 genes and reduction of Ssa1p activity, reduces the intracellular concentrations of the VDR and its heterodimeric partner, RSR alpha and reduces the activity of a vitamin D-dependent gene. Hsp70-like chaperone proteins play a role in controlling concentrations of the VDR within the cell. (C) 2001 Academic Press.