SGK2, 14-3-3, and HUWE1 Cooperate to Control the Localization, Stability, and Function of the Oncoprotein PTOV1

Abstract

PTOV1 is an oncogenic protein, initially identified in prostate cancer, that promotes proliferation, cell motility, and invasiveness. However, the mechanisms that regulate PTOV1 remain unclear. Here, 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. We discover an SGK2-mediated phosphorylation of PTOV1 at S36, which is required for 14-3-3 binding. 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. We find 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, which drives cell-cycle progression in cancer. Together, these data provide a mechanism to understand the regulation of the oncoprotein PTOV1. Implications: These findings identify a potentially targetable mechanism that regulates the oncoprotein PTOV1.

The Integration of Proteome-Wide PTM Data with Protein Structural and Sequence Features Identifies Phosphorylations that Mediate 14-3-3 Interactions

“…In our previous work, we identified several 14-3-3 client proteins whose docking site phosphorylations were difficult to identify, 26 , 43 , 71 which motivated the development of this tool. One of these 14-3-3 client proteins is the non-receptor tyrosine kinase TNK1, which we ultimately found to interact with 14-3-3 through a phosphorylation at S502 within the unusual docking sequence of ISRpSLES.…”

“…Many textbook mechanisms of molecular biology have been discovered from the perspective of understanding how 14-3-3 docks to and controls client protein activity. These mechanisms include the control of cell cycle progression via 14-3-3-mediated regulation of the CDK1-regulating phosphatase CDC25, 4 , 24 , 25 the control of cell death by 14-3-3 binding to the BH3-only protein BAD, 8 , 9 the control of transcription factor access to DNA, 26 – 29 and the regulation of various metabolic enzymes, kinases, and structural proteins. (reviewed in 14 ) 14-3-3s exert their effect by docking to one or two phosphorylated Serines or Threonines on the client protein.…”

Serine 13 of the human cytomegalovirus viral cyclin-dependent kinase UL97 is required for regulatory protein 14-3-3 binding and UL97 stability

“…The lack of an N-terminal extension in gammaherpesvirus v-CDKs implies that they may not bind 14-3-3 proteins, and indeed our preliminary efforts to isolate complexes between 14-3-3 proteins and BGLF4, the EBV v-CDK, have failed. 14-3-3 proteins regulate protein stability in multiple ways, including blocking proteolysis by sterically preventing client polyubiquitination ( 28 ), relocalizing clients away from degradation machinery ( 54 ), or can even act as chaperones to help proteins achieve or maintain more stable structures ( 55 ). How the 14-3-3 proteins stabilize UL97 remains to be explored.…”

ColocZStats: A Z-Stack Signal Colocalization Extension Tool for 3D Slicer

“…The specific approach of setting thresholds for calculating PCC is similar to that of the ‘Colocalization Analyzer’ in the Huygens Essential software (Scientific Volume Imaging B.V.., 2024a). The Huygens Essential software (Scientific Volume Imaging B.V.., 2024b) is a widely acknowledged desktop software for the visualization and analysis of microscopic images (Pennington et al, 2022; Davis et al, 2023; Volk et al, 2022). The distinction between the two is that, in ColocZStats, not only the value of the lower threshold but also that of the upper threshold can be specified for each channel.…”