Regulation of Angiopoietin-1-induced in-vitro angiogenesis by PDRG1 (P53 and DNA damage regulated 1)

The Angiopoietin-1 (Ang-1)/Tie-2 signaling axis is critical for embryonic vascular development and maintaining quiescent vasculature in adults. We recently demonstrated that Ang-1 exposure for 24 h significantly downregulates miR-1233-3p expression in endothelial cells (ECs) and that PDRG1 (P53 and DNA Damage Regulated 1) is a direct target of miR-1233-3p. However, the role of PDRG1 in Ang-1-mediated angiogenesis and the mechanisms by which PDRG1 regulates EC function remain unclear. In this study, we reveal that PDRG1 significantly enhances key angiogenic processes, including EC survival, migration, proliferation, and capillary-like tube formation, while also inhibiting Caspase-3 activity. Immunoprecipitation and mass spectrometry analyses identified multiple PDRG1-interacting proteins, including TSC2, a regulator of the mammalian target of rapamycin (mTOR) pathway. Notably, this interaction occurs not only in ECs but also in other cell types. Overexpression of PDRG1 was found to activate mTOR complex 1 (mTORC1), as evidenced by increased phosphorylation of downstream targets P70S6K and 4E-BP1. Conversely, inhibiting mTORC1 activity suppressed PDRG1-mediated effects on mTORC1 activation, EC migration, capillary-like tube formation, and proliferation. Based on these findings and our previous observation that the Ang-1/Tie-2 axis regulates miR-1233-3p expression, we propose a model in which Ang-1/Tie-2 signaling promotes angiogenesis by downregulating miR-1233-3p. This downregulation leads to increased PDRG1 expression and enhanced interaction with TSC2, ultimately alleviating the inhibitory effects of the TSC1-TSC2 complex on mTORC1 activity.