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

Abstract

26Global and endothelial loss of PTP-PEST is associated with impaired cardiovascular 27 development and embryonic lethality. Although hypoxia is implicated in vascular 28 morphogenesis and remodelling, its effect on PTP-PEST remains unexplored. Here we 29 report that hypoxia (1% oxygen)increases protein levels and catalytic activity of PTP-30 PEST in primary endothelial cells. Immunoprecipitation followed by mass spectrometry 31 (LC/MS/MS) revealed that AMP-activated protein kinase alpha subunits (AMPK α 1 and 32 α 2 ) interact with PTP-PEST under normoxia but not in hypoxia. experiments confirmed this observation and determined that AMPK α subunits interact 34 with the catalytic domain of PTP-PEST. Knock-down of PTP-PEST abrogated hypoxia 35 mediated tyrosine dephosphorylation and activation of AMPK (Thr 172 phosphorylation). 36Absence of PTP-PEST also blocked hypoxia-induced autophagy (measured as LC3 37 degradation and puncta formation) which was rescued by AMPK activator, metformin 38 (500µM). Since endothelial autophagy is a pre-requisite for angiogenesis, knock-down 39 of PTP-PEST also attenuated endothelial cell migration and capillary tube formation 40 with autophagy inducer rapamycin (200nM) rescuing these effects. In conclusion, this 41 work identifies for the first time PTP-PEST as a regulator of hypoxia-induced AMPK 42 activation and endothelial autophagy to promote angiogenesis.43 44 45 46 47 48 Physiological hypoxia is a potent agonist for embryonic development and post-natal 49 angiogenesis. Oxygen concentrations ranging from 1% to 5% are observed in the 50 uterine environment between embryonic days 3.5 to 14.5 (E3.5-E14.5) to facilitate 51 development of placenta. Similarly, in response to hypoxia (<2% oxygen), endocardial 52 and vascular endothelial cells mediate formation of foetal heart and vasculature 53 respectively in mice between embryonic days E7.5 to E15 [1;2]. Post-natal 54 angiogenesis as seen in female reproductive tract during menstrual cycle in humans, as 55 well as formation of collateral circulation to over-come coronary artery blocks also 56 depend on hypoxia-induced endothelial signalling. Other than the known classical 57 mediators of angiogenesis, multiple studies in rodents have reported increased activity 58 of cytosolic protein tyrosine phosphatases (PTPs) at the sites of post-natal 59 angiogenesis, including ischemic myocardium and skeletal muscles [3;4]. An increase 60 in the cytosolic PTP activity during hypoxia is also seen in the cerebral cortex of new 61 born piglets [5]. Paradoxically, others have shown that non-selective PTP inhibitor, 62 sodium orthovanadate, enhances VEGFR2 signalling and capillary morphogenesis 63 [3;6]. Although these studies allude to the involvement of different PTPs in hypoxia-64 induced angiogenic signalling, barring the involvement of few, for instance VE-PTP (a 65 receptor PTP), the identity of hypoxia responsive cytosolic angiogenic PTPs remains 66 largely unknown. 67 68 Human genome encodes 38 classical PTPs which are specific for tyr...

RETRACTED: mtROS-mediated Akt/AMPK/mTOR pathway was involved in Copper-induced autophagy and it attenuates Copper-induced apoptosis in RAW264.7 mouse monocytes

“…The PI3K/Akt signal transduction pathway controls mTOR activity [ 25 ]. Moreover, the activation of AMPK is recently suggested to result in autophagy by negatively modulating mTOR [ 26 ]. Besides, AMPK can directly phosphorylate ULK1 to induce autophagy [ 26 ].…”

“…Moreover, the activation of AMPK is recently suggested to result in autophagy by negatively modulating mTOR [ 26 ]. Besides, AMPK can directly phosphorylate ULK1 to induce autophagy [ 26 ]. These results demonstrate that CuSO 4 induces autophagy through Akt/AMPK/mTOR/ULK1 signaling.…”

Three Distinct Transcriptional Profiles of Monocytes Associate with Disease Activity in SSc Patients

“…Both Group B and C upregulated genes associated with vasculature development and blood vessel morphogenesis, such as VEGFA and HBEGF (58), but Group C additional genes associated with angiogenesis (i.e. CXCR4 (59) and PTPN12 (60)). Further, Group C also expressed upregulated genes associated with TGFB and BMP signaling, including TGFB1 , SMAD3 , SKIL and PPARD .…”