University Honors

It is taught in textbooks that steroid hormones are lipid based molecules that passivelydiffuse through the cell membrane into the cell. However, recent studies have shown that thefruit fly Drosophila melanogaster has a membrane transporter for ecdysone, a steroid hormonein insects, called Ecdysone Importer (EcI). This implies that other steroid hormones, includingmammalian steroid hormones, might also require transportation across the cell membranes,challenging our current understanding of this pathway. EcI is a member of a highly conservedsuperfamily of genes called Organic Anion Transporting Polypeptides (OATPs), which are alsoconserved in mammals. In these experiments, we investigated the potential role of OATPs thatare highly expressed in HEK293T cells in cortisol cellular import. We tested for the transport ofcortisol into cells by measuring cortisol-induced GR activation through a luciferase assay. UsingqPCR, we analyzed the differences in expression levels of glucocorticoid-inducible genes in wildtype HEK293T cells, OATP-overexpressing HEK293T cells, and double-knockout HEK293Tcells where the two most highly expressed OATP genes are knocked out. Lastly, we utilizedA549 lung cancer cells whose proliferation is known to be inhibited by glucocorticoids to furtheranalyze the role OATPs play in glucocorticoids cellular import. In wildtype A549 cells andOATP-overexpressing A549 cells, growth was monitored with the addition of different doses ofeither a methanol control, cortisol, or dexamethasone. This research will help to elucidate themechanisms behind steroid hormone transport, opening up pathways to be used in more preciseand effective medicine and research.