Thesis presented November 29, 2023

Abstract:
Endothelial plasticity involves tyrosine phosphorylation of the cadherin–catenin complex including VE-cadherin. To provide a systematic broad-based view of this mechanisms , in the present study, we report the comprehensive transcriptome profiling of Lung ECs from carrying the single point mutation Y685F VE-cadherin and unveil cellular dynamics and molecular features associated with cell-cell adhesion and angiogenesis. We identified a total of 884 differential expressed genes (DEGs) regulated by VE-cadherin knock-in on the basis of transcriptomic RNA sequencing (RNA-Seq). Gene ontology analysis revealed that upregulated DEGs were mainly enriched in cell-cell adhesion and angiogenesis which were found to be the most deregulated functions of lung EC culture. Among the top 30 DEGs, genes encoding for transmembrane receptors were up-regulated, whereas genes encoding for protein phosphatase or enzymes involved in anions transport, and lipid metabolism were downregulated. Among receptors, Sphingosine-1-phosphate-receptor 1 (S1pr1) was the highest mean expression among the samples. Analysis of gene interaction networks identified that S1pr1 strongly linked with Cdh5, Kdr and genes related to cell-cell adhesion and angiogenesis. Mechanistically, immunoprecipitation assay showed a significant decrease in the ratio mutant VE-cadherin/ beta-catenin which was correlated with an increase in the nuclear ratio beta-catenin/Histone H3. Using Chromatin immunoprecipitation assay (CHIPS), we found that the transcriptional activity of S1pr1 promoter was increased by the direct binding of the lung transcriptional regulator FOXF1. Of importance, VE-cadherin mutant was phosphorylated on Y731 and located the membrane which showed less vascular remodeling with less fibrosis in lungs from mutated mice . Hence, our findings provide new insights in the role of a single tyrosine of VE-cadherin which would participate in an endothelial-specific transcription program important for tumor vessels and therapeutic targets. Moreover, we studied the VE-cadherin modification by a tumor microenvironment using 2D and 3D in vitro models of triple negative breast cancer cells co-cultured with endothelial cells. This a step foward developing tools for drug efficiency testing .Finally, VE-cadherin could be used as a potenital biomarker in clinical studies such as SARS-CoV-2 infection.

Keywords:
phosphorylation, tyrosine kinase, gene expression, Endothelial cell functions, VE-cadherin

On-line thesis. ​