Hepatocyte growth Factor/Scatter factor (HGF/SF) is a regulator of fibronectin splicing in MDCK cells: comparison between the effects of HGF/SF and TGF-beta1 on fibronectin splicing at the EDA region.
EDA-containing fibronectin (EDA + FN) is selectively produced under several physiological and pathological conditions requiring tissue remodeling, where cells actively proliferate and migrate. Only a few growth factors, such as transforming growth factor (TGF)-beta1, have been reported to regulate FN splicing at the EDA region. In the present study, we showed for the first time that hepatocyte growth factor/scatter factor (HGF/SF), which is mainly produced by mesenchymal cells and functions as a motogenic and mitogenic factor for epithelial cells, modulates FN splicing at the EDA region in MDCK epithelial cells. HGF/SF treatment increased the ratio of EDA + FN mRNA to mRNA of FN that lacks EDA (EDA - FN) (EDA+/EDA- ratio) more than TGF-beta1 treatment did: at a range from 0.02 to 20 ng/ml, HGF/SF increased the ratio in a dose-dependent manner by up to 2. 1-fold compared with nontreated control, while TGF-beta1 stimulated the EDA+/EDA- ratio by 1.5-fold at the optimum dose of 10 ng/ml. However, TGF-beta1 increased total FN mRNA levels by 3-fold at 10 ng/ml, but HGF/SF did not. We previously demonstrated that fibroblasts cultured at low cell density expressed more EDA + FN than those at high cell density. The same effect of cell density was also observed in MDCK cells. Furthermore, at low cell density, HGF/SF stimulated EDA inclusion into FN mRNA more effectively than did TGF-beta1, whereas at high cell density, TGF-beta1 was more potent than HGF/SF. Simultaneous treatment of cells with HGF/SF and TGF-beta1 synergistically stimulated EDA inclusion into FN mRNA. This stimulation of EDA inclusion into FN mRNA by HGF/SF led to increased EDA + FN protein production and secretion by cells, which was demonstrated by immunoblotting. Thus, our studies have shown that HGF/SF is an enhancer of EDA inclusion into FN mRNA as is TGF-beta1. However, these two factors were different in their effects at low and high cell densities and also in their effects on total FN mRNA levels.
Inoue
T
T
Second Department of Pathology, Miyazaki Medical College, 5200 Kihara, Miyazaki, Kiyotake, 889-1692, Japan.
Nabeshima
K
K
Shimao
Y
Y
Koono
M
M
D000818:Animals; D002452:Cell Count; D002460:Cell Line; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D053331:Ectodysplasins; D005353:Fibronectins / Q000378:metabolism*; D017228:Hepatocyte Growth Factor / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
C506018:EDA protein, human; D053331:Ectodysplasins; D005353:Fibronectins; D008565:Membrane Proteins; D016212:Transforming Growth Factor beta; D017228:Hepatocyte Growth Factor