Dataset Information

Vascular endothelial protein tyrosine phosphatase: Identification of novel cell junction-related substrates and a ternary receptor complex with EPHB4 and TIE2

ABSTRACT: 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.

INSTRUMENT(S): LTQ Orbitrap Velos

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Endothelial Cell

SUBMITTER: Hannes Drexler

LAB HEAD: Hannes C. A. Drexler

PROVIDER: PXD011940 | Pride | 2019-08-20

REPOSITORIES: Pride

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Publications

Vascular Endothelial Receptor Tyrosine Phosphatase: Identification of Novel Substrates Related to Junctions and a Ternary Complex with EPHB4 and TIE2.

Drexler Hannes C A HCA Vockel Matthias M Polaschegg Christian C Frye Maike M Peters Kevin K Vestweber Dietmar D

Molecular & cellular proteomics : MCP 20190819 10

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. We and others have shown recently that VE-PTP regulates vascular integrity by dephosphorylating substrates that 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 VEGF ...[more]

PMID: 31427368

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Project description:Rationale: The mechanistic foundation of vascular maturation is still largely unknown. Several human pathologies are characterized by deregulated angiogenesis and unstable blood vessels. Solid tumours, for instance, get their nourishment from newly formed structurally abnormal vessels which present wide and irregular inter-endothelial junctions. Expression and clustering of the main endothelial-specific adherens junction protein, vascular endothelial (VE)-cadherin (VEC), upregulate genes with key roles in endothelial differentiation and stability. Objective: We aim at understanding the molecular mechanisms through which VEC triggers the expression of a set of genes involved in endothelial differentiation and vascular stabilization. Methods and Results: We compared a VEC-null cell line with the same line reconstituted with VEC wild type cDNA. VEC expression and clustering upregulated endothelial-specific genes with key roles in vascular stabilization including claudin-5, Vascular Endothelial-Protein Tyrosine Phosphatase (VE-PTP) and von Willebrand factor (vWf). Mechanistically VEC exerts this effect by inhibiting Polycomb protein activity on the specific gene promoters. This is achieved by preventing nuclear translocation of FoxO1 and β-catenin, which contribute to Polycomb repressive complex-2 (PRC2) binding to promoter regions of claudin-5, VE-PTP and vWf. VE-cadherin/β-catenin complex also sequesters a core subunit of PRC2 (Ezh2) at the cell membrane, preventing its nuclear translocation. Inhibition of Ezh2/VE-cadherin association increases Ezh2 recruitment to claudin-5, VE-PTP and vWf promoters, causing gene downregulation. RNAseq comparison of VEC-null and VEC-positive cells suggested a more general role of VE-cadherin in activating endothelial genes and triggering a vascular stability-related gene expression program. In pathological angiogenesis of human ovarian carcinomas, reduced VEC expression paralleled decreased levels of Claudin-5 and VE-PTP. Conclusions: These data extend the knowledge of Polycomb-mediated regulation of gene expression to endothelial cell differentiation and vessel maturation. The identified mechanism opens novel therapeutic opportunities to modulate endothelial gene expression and induce vascular normalization through pharmacological inhibition of the Polycomb-mediated repression system. Keywords: Polycomb, endothelial cells, VE-cadherin, vessel maturation, vascular biology, vascular permeability, cell signalling, epigenetics, gene regulation. Downloaded from http://circres.ahajour Conclusions: These data extend the knowledge of Polycomb-mediated regulation of gene expression to endothelial cell differentiation and vessel maturation. The identified mechanism opens novel therapeutic opportunities to modulate endothelial gene expression and induce vascular normalization through pharmacological inhibition of the Polycomb-mediated repression system

Dataset Information

Vascular endothelial protein tyrosine phosphatase: Identification of novel cell junction-related substrates and a ternary receptor complex with EPHB4 and TIE2

Publications

Vascular Endothelial Receptor Tyrosine Phosphatase: Identification of Novel Substrates Related to Junctions and a Ternary Complex with EPHB4 and TIE2.

Similar Datasets

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