Activation of Src Mediates PDGF-Induced Smad1 Phosphorylation and Contributes to the Progression of Glomerulosclerosis in Glomerulonephritis

Akira Mima,Toru Kita,Kojiro Nagai,Atsushi Fukatsu,Toshio Doi,Takeshi Matsubara,Hidenori Arai,Hideharu Abe,Tatsuya Tominaga,Kazuo Torikoshi,Noriyuki Iehara,Makoto Araki

doi:10.1371/journal.pone.0017929

Akira Mima, Toru Kita + Show 10 more

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https://doi.org/10.1371/journal.pone.0017929

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Journal: PLoS ONE	Publication Date: Mar 22, 2011
Citations: 53	License type: CC BY 4.0

Affiliation: Kyoto University, Tokushima University

Abstract

Platelet-derived growth factor (PDGF) plays critical roles in mesangial cell (MC) proliferation in mesangial proliferative glomerulonephritis. We showed previously that Smad1 contributes to PDGF-dependent proliferation of MCs, but the mechanism by which Smad1 is activated by PDGF is not precisely known. Here we examined the role of c-Src tyrosine kinase in the proliferative change of MCs. Experimental mesangial proliferative glomerulonephritis (Thy1 GN) was induced by a single intravenous injection of anti-rat Thy-1.1 monoclonal antibody. In Thy1 GN, MC proliferation and type IV collagen (Col4) expression peaked on day 6. Immunohistochemical staining for the expression of phospho-Src (pSrc), phospho-Smad1 (pSmad1), Col4, and smooth muscle α-actin (SMA) revealed that the activation of c-Src and Smad1 signals in glomeruli peaked on day 6, consistent with the peak of mesangial proliferation. When treated with PP2, a Src inhibitor, both mesangial proliferation and sclerosis were significantly reduced. PP2 administration also significantly reduced pSmad1, Col4, and SMA expression. PDGF induced Col4 synthesis in association with increased expression of pSrc and pSmad1 in cultured MCs. In addition, PP2 reduced Col4 synthesis along with decreased pSrc and pSmad1 protein expression in vitro. Moreover, the addition of siRNA against c-Src significantly reduced the phosphorylation of Smad1 and the overproduction of Col4. These results provide new evidence that the activation of Src/Smad1 signaling pathway plays a key role in the development of glomerulosclerosis in experimental glomerulonephritis.

Highlights

Glomerulonephritis is usually progressive and remains an important cause of end stage renal disease
Effect of PP2 on Platelet-derived growth factor (PDGF)-mediated signaling in mesangial cell (MC) Because PDGF is well known to play a key role in the development of glomerulosclerosis, we investigated whether PDGF can activate c-Src/Smad1 signal transduction and increase the synthesis of Col4
Glomerulosclerosis followed by mesangial proliferative glomerulonephritis is characterized by mesangial matrix expansion and phenotypic change of MCs [3]

Summary

Introduction

Glomerulonephritis is usually progressive and remains an important cause of end stage renal disease. Accumulation of the extracellular matrix (ECM) is a critical process in progressive glomerular injuries [1,2]. Type IV collagen (Col4) is one of the most important components of the expanded ECM [3]. Smooth muscle a actin (SMA) is a known common molecular marker of phenotypic changes of mesangial cells (MCs) in many glomerular diseases. We previously reported that Smad participates in the development of glomerulosclerosis in experimental glomerulonephritis [4]. We reported that Smad transcriptionally regulates the expression of Col and SMA [5,6]. The mechanisms by which Smad is activated in glomerulonephritis have not been fully elucidated

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