Protein tyrosine phosphatase-PEST (PTP-PEST) mediates hypoxia-induced endothelial autophagy and angiogenesis through AMPK activation

Global and endothelial loss of PTP-PEST is associated with impaired cardiovascular development and embryonic lethality. Although hypoxia is implicated in vascular morphogenesis and remodelling, its effect on PTP-PEST remains unexplored. Here we report that hypoxia (1% oxygen)increases protein levels and catalytic activity of PTP-PEST in primary endothelial cells. Immunoprecipitation followed by mass spectrometry (LC/MS/MS) revealed that AMP-activated protein kinase alpha subunits (AMPK α and α) interact with PTP-PEST under normoxia but not in hypoxia. Co-immunoprecipitation experiments confirmed this observation and determined that AMPK α subunits interact with the catalytic domain of PTP-PEST. Knock-down of PTP-PEST abrogated hypoxia mediated tyrosine dephosphorylation and activation of AMPK (Thr phosphorylation). Absence of PTP-PEST also blocked hypoxia-induced autophagy (measured as LC3 degradation and puncta formation) which was rescued by AMPK activator, metformin (500µM). Since endothelial autophagy is a pre-requisite for angiogenesis, knock-down of PTP-PEST also attenuated endothelial cell migration and capillary tube formation with autophagy inducer rapamycin (200nM) rescuing these effects. In conclusion, this work identifies for the first time PTP-PEST as a regulator of hypoxia-induced AMPK activation and endothelial autophagy to promote angiogenesis.