TGF-β-induced mesenchymal transition of MS-1 endothelial cells requires Smad-dependent cooperative activation of Rho signals and MRTF-A

Abstract

Endothelial-mesenchymal transition (EndMT) plays important roles in various physiological and pathological processes. While signals mediated by transforming growth factor (TGF)-β have been implicated in EndMT, the molecular mechanisms underlying it remain to be fully elucidated. Here, we examined the effects of TGF-β signals on the EndMT of mouse pancreatic microvascular endothelial cells (MS-1). By addition of TGF-β2, MS-1 cells underwent mesenchymal transition characterized by re-organization of actin stress fibre and increased expression of various mesenchymal markers such as α-smooth muscle actin (α-SMA) through activation of Rho signals. Whereas activation of Rho signals via TGF-β-induced non-Smad signals has been implicated in epithelial-mesenchymal transition (EMT), we found that Arhgef5, a guanine nucleotide exchange factor, is induced by Smad signals and contributes to the TGF-β2-induced α-SMA expression in MS-1 cells. We also found that TGF-β2 induces the expression of myocardin-related transcription factor-A (MRTF-A) in a Smad-dependent fashion and its nuclear accumulation in MS-1 cells and that MRTF-A is required and sufficient for TGF-β2-induced α-SMA expression. These results indicate that activation of Smad signals by TGF-β2 have dual effects on the activation of Rho signals and MRTF-A leading to the mesenchymal transition of MS-1 endothelial cells.

TGF-β-induced differentiation into myofibroblasts involves specific regulation of two MKL1 isoforms

“…4C). As reported by others (Mihira et al, 2012;Minami et al, 2012;Sandbo et al, 2011), we also observed an increase in total MKL1 levels compared to control cells (Fig. 4D).…”

“…Current models suggest a complex interplay between TGF-b/Smad3 and the Rho-actin-MKL1 signaling pathways during myofibroblast differentiation (Charbonney et al, 2011;Masszi et al, 2010;Small, 2012). Several studies have shown that TGF-b upregulates total MKL1 expression and triggers the nuclear accumulation of MKL1, but not MKL2, in different precursor cells (Gupta et al, 2013;Mihira et al, 2012;Minami et al, 2012;Morita et al, 2007;Sandbo et al, 2011). However, TGF-b-mediated MKL1 translocation occurs in a delayed fashion compared to direct stimulation of the Rho-actin-MKL1 pathway.…”

Microvascular Endothelial Cells Poised to Take Center Stage in Experimental Renal Fibrosis

“…12 Interestingly, endothelin-1/endothelin receptor type A-mediated glomerular endothelial cell dysfunction is required for podocyte depletion and progression of glomerulosclerosis in several podocyte injury models. 13 Endothelial fenestrations and surface layer are characteristic hallmarks of differentiated capillary endothelial cells. A reduced number of glomerular endothelial fenestrations in patients with type 1 and type 2 diabetes has been documented.…”

Endothelial-mesenchymal transition in normal human esophageal endothelial cells cocultured with esophageal adenocarcinoma cells: role of IL-1β and TGF-β2

“…Many studies have pointed to the important role of TGF-␤ receptor signaling and downstream targets, such as RhoA, Smad, and Snail transcriptional repressor in EndoMT (11,18). Additionally, interleukin-1␤ (IL-1␤) has been found to also initiate the transition of endothelial cells to mesenchymal cells in corneal endothelial cells (14).…”