scholarly journals Connective tissue growth factor (CTGF) promotes activated mesangial cell survival via up-regulation of mitogen-activated protein kinase phosphatase-1 (MKP-1)

2007 ◽  
Vol 406 (1) ◽  
pp. 131-138 ◽  
Author(s):  
Nadia Wahab ◽  
Dimity Cox ◽  
Abigail Witherden ◽  
Roger M. Mason
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Protein Kinase ◽  
Connective Tissue ◽  
P38 Mapk ◽  
Mesangial Cell ◽  
Mesangial Cells ◽  
Tissue Growth ◽  
Mitogen Activated Protein Kinase ◽  
Mitogen Activated Protein

Activated mesangial cells are thought to play a pivotal role in the development of kidney fibrosis under chronic pathological conditions, including DN (diabetic nephropathy). Their prolonged survival may enhance the development of the disease since they express increased amounts of growth factors and extracellular matrix proteins. CTGF (connective tissue growth factor) is one of the growth factors produced by activated mesangial cells and is reported to play a key role in the pathogenesis of DN. Previous studies have shown that addition of exogenous CTGF to HMCs (human mesangial cells) rapidly activates ERK1/2 (extracellular-signal-regulated kinase 1/2) MAPK (mitogen-activated protein kinase) and JNK (c-Jun N-terminal kinase) MAPK, but not the p38 MAPK, despite the activation of the upstream kinases, MKK3/6 (MAPK kinase 3/6). The aim of the present study was to investigate whether the lack of phosphorylated p38 MAPK by CTGF has an anti-apoptotic effect on activated HMCs. We show that in HMC CTGF induces the rapid transcriptional activation and synthesis of MKP-1 (MAPK phosphatase-1), a dual specificity phosphatase that dephosphorylates p38 MAPK. This in turn prevents the anti-apoptotic protein, Bcl-2, from being phosphorylated and losing its function, leading to the survival of the cells. Knockout of MKP-1 protein in mesangial cells treated with CTGF, using siRNA (small interfering RNA) or antisense oligonucleotides, allows p38 MAPK activation and induces mesangial cell death.

scholarly journals CCN2 (Connective Tissue Growth Factor) Promotes Fibroblast Adhesion to Fibronectin

2004 ◽  
Vol 15 (12) ◽  
pp. 5635-5646 ◽  
Author(s):  
Yunliang Chen ◽  
David J. Abraham ◽  
Xu Shi-wen ◽  
Jeremy D. Pearson ◽  
Carol M. Black ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Growth Factor ◽  
Protein Kinase ◽  
Connective Tissue ◽  
Connective Tissue Growth Factor ◽  
Tissue Growth ◽  
Mitogen Activated Protein Kinase ◽  
Mitogen Activated Protein ◽  
Fibroblast Adhesion

In vivo, CCN2 (connective tissue growth factor) promotes angiogenesis, osteogenesis, tissue repair, and fibrosis, through largely unknown mechanisms. In vitro, CCN2 promotes cell adhesion in a variety of systems via integrins and heparin sulfate proteoglycans (HSPGs). However, the physiological relevance of CCN2-mediated cell adhesion is unknown. Here, we find that HSPGs and the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase cascade are required for adult human dermal fibroblasts to adhere to CCN2. Endogenous CCN2 directly binds fibronectin and the fibronectin receptors integrins α4 β1 and α5 and syndecan 4. Using Ccn2-/- mouse embryonic fibroblasts, we show that loss of endogenous CCN2 results in impaired spreading on fibronectin, delayed α-smooth muscle actin stress fiber formation, and reduced ERK and focal adhesion kinase phosphorylation. These results suggest that a physiological role of CCN2 is to potentiate the ability of fibroblasts to spread on fibronectin, which may be important in modulating fibroblast adhesion to the provisional matrix during tissue development and wound healing. These results are consistent with the notion that a principal function of CCN2 is to modulate receptor/ligand interactions in vivo.

scholarly journals Phosphorylation of Fibroblast Growth Factor (FGF) Receptor 1 at Ser777 by p38 Mitogen-Activated Protein Kinase Regulates Translocation of Exogenous FGF1 to the Cytosol and Nucleus

2008 ◽  
Vol 28 (12) ◽  
pp. 4129-4141 ◽  
Author(s):  
Vigdis Sørensen ◽  
Yan Zhen ◽  
Malgorzata Zakrzewska ◽  
Ellen Margrethe Haugsten ◽  
Sébastien Wälchli ◽  
...  
Keyword(s):  
Growth Factor ◽  
Protein Kinase ◽  
Fibroblast Growth Factor ◽  
P38 Mapk ◽  
Activity Level ◽  
Mitogen Activated Protein Kinase ◽  
Target Cells ◽  
Fibroblast Growth ◽  
Mitogen Activated Protein ◽  
P38α Mapk

ABSTRACT Exogenous fibroblast growth factor 1 (FGF1) signals through activation of transmembrane FGF receptors (FGFRs) but may also regulate cellular processes after translocation to the cytosol and nucleus of target cells. Translocation of FGF1 occurs across the limiting membrane of intracellular vesicles and is a regulated process that depends on the C-terminal tail of the FGFR. Here, we report that translocation of FGF1 requires activity of the α isoform of p38 mitogen-activated protein kinase (MAPK). FGF1 translocation was inhibited after chemical inhibition of p38 MAPK or after small interfering RNA knockdown of p38α. Translocation was increased after stimulation of p38 MAPK with anisomycin, mannitol, or H2O2. The activity level of p38 MAPK was not found to affect endocytosis or intracellular sorting of FGF1/FGFR1. Instead, we found that p38 MAPK regulates FGF1 translocation by phosphorylation of FGFR1 at Ser777. The FGFR1 mutation S777A abolished FGF1 translocation, while phospho-mimetic mutations of Ser777 to Asp or Glu allowed translocation to take place and bypassed the requirement for active p38 MAPK. Ser777 in FGFR1 was directly phosphorylated by p38α in a cell-free system. These data demonstrate a crucial role for p38α MAPK in the regulated translocation of exogenous FGF1 into the cytosol/nucleus, and they reveal a specific role for p38α MAPK-mediated serine phosphorylation of FGFR1.

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