PTOV1 is an oncogenic protein, initially identified in prostate cancer, that promotes proliferation, cell motility, and invasiveness. However, the mechanism of PTOV1 regulation is poorly understood. To understand these mechanisms, we identify 14-3-3 as a PTOV1 interactor and show that high levels of 14-3-3 expression, like PTOV1, correlate with prostate cancer progression. Further, we found that SGK2-mediated phosphorylation of PTOV1 is required for 14-3-3 binding. This phosphorylation occurs in a cell cycle-dependent manner and peaks in the G1 phase. Disruption of the PTOV1-14-3-3 interaction results in an accumulation of PTOV1 in the nucleus and a proteasome-dependent reduction in PTOV1 protein levels. To understand the effect of 14-3-3 on PTOV1 stability, we found that loss of 14-3-3 binding leads to an increase in PTOV1 binding to the E3 ubiquitin ligase HUWE1, which promotes proteasomal degradation of PTOV1. Conversely, our data suggest that 14-3-3 stabilizes PTOV1 protein by sequestering PTOV1 in the cytosol and inhibiting its interaction with HUWE1. Finally, our data suggest that stabilization of the 14-3-3-bound form of PTOV1 promotes PTOV1-mediated expression of cJun. Together, these data provide a first mechanism to understand the regulation of PTOV1 stability, localization, and function within the cell.

Citation Format: Katie L. Pennington, James Woods, Colin Muir, Colten M. McEwan, Pramoda S. Aththota Gamage, Riley J. Eastmond, Crissy M. Egbert, Tyler Heaton, Stephen R. Piccolo, Joshua L. Andersen. SGK2, 14-3-3, and HUWE1 coordinately regulate the localization and stability of PTOV1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2295.