Journal of Proteomics & Bioinformatics
Open Access

Abstract

Differential Quantitative Proteomics of Human Microvascular Endothelial Cells 1 by iTRAQ Reveals Palladin to be a New Biomarker During TGF-?1 Induced Endothelial Mesenchymal Transition

Marta Stasiak, Katarzyna Gawryś, Marcin Popielarski, Radosław Bednarek, Maciej Studzian, Ewa Sitkiewicz, Janusz Szemraj and Maria Swiatkowska

The study uses global quantitative proteomics to investigate the molecular mechanisms behind the induction of endothelial-mesenchymal transition (EndMT) by transforming growth factor–β (TGF-β). Orbitrap Velos mass spectrometers and iTRAQ – a labeling-based analysis were used to perform a global and quantitative comparison of two proteomes of Human Microvascular Endothelial Cells-1 (HMEC-1) treated or not treated by TGF-β1. iTRAQ analysis identified 43 differentially-expressed proteins in the early stages of EndMT induced by TGF-β1. From 5522 identified proteins, 26 were downregulated and 17 were upregulated, including proteins such as palladin, POTE I, torsin A and nucleoporin (NDC1). Further analysis of palladin revealed its increased mRNA and protein expression in response to TGF-β and Snail transcription factor. Our findings demonstrate that the newly- identified proteins may be involved in early stages of biological processes leading to EndMT.

Biological Significance: Endothelial to mesenchymal transition is a possible source of myofibroblasts, which play a crucial role in the pathogenesis of fibrosis. EndMT participate in tissue fibrotic processes in various organs. TGF-β family growth factors are involved in the initiation of EndMT. The intracellular cascades activated by TGF-β that result in the remarkable phenotypic change of endothelial cells to mesenchymal cells have not been entirely elucidated. The downstream signaling pathway initiated by TGF-β resulted in a strong upregulation of the Snail1 transcriptional repressor. Our proteomics data demonstrated that TGF-β -induced EndMT leads to alterations in protein profiles, more specifically, the upregulation of palladin. This upregulation is mediated by Snail transcription factor and GSK-3 β signaling kinase. Our results also suggest that palladin could be considered a new biomarker in the early stages of cellular transdifferentiation, eventually leading to endothelial-mesenchymal transition.