SUN-027 Androgen Induces Its Own Receptor Expression in Human Granulosa Cells

Abstract

Androgens are very important in the regulation of normal ovarian function, as well as pathologies such as ovarian insufficiency and polycystic ovary syndrome. Androgen receptors are present in all major cell types of the ovarian follicle, and are most abundant in granulosa cells where they enhance proliferation during the follicular phase of the reproductive cycle. However, the molecular pathways mediating androgen actions in the ovary are not clearly delineated. We previously found that in human prostate cancer cells, androgen receptor (AR) is highly active in the extra-nuclear compartment, where it stimulates kinase signaling and enhances growth factor-induced cell proliferation. Further, these novel extra-nuclear actions of AR require paxillin, a cytoplasmic adapter protein that is implicated in cell growth, cytoskeletal remodeling and kinase signaling in many tissues. Here, we investigated the role of paxillin in androgen-regulated processes in human granulosa cells using the KGN cell line. We show that 25 nM dihydrotestosterone (DHT) treatment greatly induces the protein expression of AR, while its mRNA is unaffected. This induction is apparent as early as one hour after DHT treatment and the AR protein further accumulates with continued exposure. Importantly, near-depletion of paxillin with siRNA significantly blunted this induction, as well as basal AR protein expression. Our results indicate that androgens are capable of generating a positive feedback loop in granulosa cells at the level of their receptor, potentially greatly amplifying their actions. This occurs independently of AR gene transcription and requires paxillin, adding to the growing body of evidence that paxillin mediates extra-nuclear steroid signaling in various endocrine tissues. Our ongoing studies are aimed at identifying the mechanism of AR protein accumulation by DHT and clarifying paxillin involvement in this and other processes in the ovary.