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Gene expression profile in HUVECs before and after Angiopoietin stimulation

ABSTRACT: Angiopoietin-Tie2 sytem has been inplicated in both vascular quiescence and angiogenesis. It is unclear how these two opposing signals are regulated from the same receptor-mediated intracellular signal transduction. We have noticed that Tie2 localization upon Angiopoietin stimulation depends upon the presence or absence of cell-cell contacts. Therefore, to identify the downstream signaling of Tie2 upon Angiopoietin stimulation, we performed DNA microarray analyais using RNAs obtained from confluent human umbirical vein endothelial cells (HUVECs) or sparse HUVECs stimulated with after Angiopoietin-1. There is striking difference on gene expression profile between confluent and sparse HUVECs. Keywords: endothelial cell, angiopoietin

ORGANISM(S): Homo sapiens

PROVIDER: GSE9677 | GEO | 2008/04/01

SECONDARY ACCESSION(S): PRJNA103567

REPOSITORIES: GEO

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Project description:Vascular endothelial protein tyrosine phosphatase (VE-PTP, PTPRB) is a receptor type phosphatase that is crucial for the regulation of endothelial junctions and blood vessel development. VE-PTP regulates vascular integrity by dephosphorylating substrates which are key players in endothelial junction stability, such as the angiopoietin receptor TIE2, the endothelial adherens junction protein VE-cadherin and the vascular endothelial growth factor receptor VEGFR2. Here, we have systematically searched for novel substrates of VE-PTP in endothelial cells by utilizing two approaches. First, we studied changes in the endothelial phosphoproteome upon exposing cells to a highly VE-PTP-specific phosphatase inhibitor followed by affinity isolation and mass-spectrometric analysis of phosphorylated proteins by phosphotyrosine-specific antibodies. Second, we used a substrate trapping mutant of VE-PTP to pull down phosphorylated substrates in combination with SILAC-based quantitative mass spectrometry measurements. We identified a set of substrate candidates of VE-PTP, of which a remarkably large fraction is related to cell junctions (48/165; 29.1%). Several of those were found in both screens and displayed very high connectivity in predicted functional interaction networks. The receptor protein tyrosine kinase EPHB4 was the most prominently phosphorylated protein upon VE-PTP inhibition among those VE-PTP targets that were identified by both proteomic approaches. Further analysis revealed that EPHB4 forms a ternary complex with VE-PTP and TIE2 in endothelial cells. VE-PTP controls the phosphorylation of each of these two tyrosine kinase receptors. Despite of their simultaneous presence in a ternary complex, stimulating each of the receptors with their own specific ligand did not cross-activate the respective partner receptor. Our systematic approach has led to the identification of novel substrates of VE-PTP, of which many are relevant for the control of cellular junctions further promoting the importance of VE-PTP as a key player of junctional signalling.

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Gene expression profile in HUVECs before and after Angiopoietin stimulation

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