THU573 Paxillin Regulates Androgen Receptor In Granulosa Cells

Abstract

Abstract Disclosure: A. Weidner: None. A. Roy: None. K. Vann: None. O. Astapova: None. Paxillin is a ubiquitously-expressed adaptor protein that is integral in focal adhesions and plays an active role in the regulation of cell motility and apoptosis. Recently, paxillin was shown to mediate pro-tumorigenic androgen signaling in prostate cancer cells, where it is necessary for rapid cytoplasmic kinase signaling triggered by activation of membrane-bound androgen receptor. We sought to investigate the relationship between paxillin and androgen receptor (AR) in granulosa cells, where androgen actions, apoptosis and focal adhesions are of known importance, but the role of paxillin is understudied. When paxillin expression was silenced using siRNA in human granulosa-derived KGN cells, AR protein expression was significantly reduced, while its RNA expression was unaffected. Similarly, in granulosa cell-specific paxillin knockout mice, AR protein expression in granulosa cells was reduced. Further, we found that AR and paxillin co-localize in focal adhesions in mouse primary granulosa cells and in KGN cells, and their interaction requires the activity of focal adhesion kinase. Disruption of focal adhesion with a focal adhesion kinase inhibitor also leads to reduced AR protein levels. To further explore the mechanisms by which paxillin regulates AR expression, we created paxillin-null KGN cell lines using CRISPR-Cas9 gene editing. While paxillin loss resulted in reduced AR protein expression early (days) in the gene-editing process, this effect disappeared after weeks of clonal expansion from selected single cells. Expanded paxillin-null KGN clones showed normal AR protein expression, but increased AR mRNA expression, suggesting an adaptive increase in AR gene transcription to compensate for reduced AR protein levels in cells that survived paxillin deletion. Studies of AR protein degradation using cycloheximide to block protein synthesis showed that the half-life of AR was reduced from 6.7 to 4.5 hours (approximately 33%) by paxillin deletion, indicating accelerated AR protein degradation in cells lacking paxillin. Based on our results, we hypothesize that paxillin brings AR into focal adhesions in granulosa cells, thereby sequestering it from proteasomal degradation in the cytoplasm. Thus, paxillin may be a novel target in the management of androgen-related disorders in women, such as polycystic ovary syndrome. Presentation Date: Thursday, June 15, 2023