Evaluation of a novel photoactive and biotinylated dehydroepiandrosterone analog

To characterize the cell surface receptor for dehydroepiandrosterone (DHEA), we synthesized a DHEA analog containing biotin and benzophenone groups (DHEA–BP–Bt). DHEA–BP–Bt was equipotent with DHEA in competing with [3H]DHEA for binding to solubilized plasma membranes of bovine aortic endothelial cells (BAEC). Additionally, DHEA–BP–Bt pre-conjugated to avidin and immobilized on agarose, also inhibited plasma membrane binding of [3H]DHEA. Furthermore, DHEA–BP–Bt activated endothelial nitric oxide synthase, similar to DHEA. Confocal micrographs showed that, upon photoirradiation, DHEA–BP–Bt bound to sites on the cell surface of BAEC in a DHEA inhibitable manner. Finally, DHEA–BP–Bt bound specifically to proteins of approximately 55 kDa and 80 kDa, either when live cells were UV irradiated with the analog and plasma membrane proteins separated by SDS-PAGE or in a ligand blot analysis. These data confirm the successful synthesis of a photoactive, biotinylated DHEA analog which is capable of cross-linking to and identifying plasma membrane DHEA binding sites and which will allow us to further purify this receptor.