Separate roles for H‐Ras and Rac in signaling by transforming growth factor (TGF)‐β: H‐Ras is essential for activation of MAP kinase, partially required for …

H Yamamoto, N Atsuchi, H Tanaka… - European journal of …, 1999 - Wiley Online Library
H Yamamoto, N Atsuchi, H Tanaka, W Ogawa, M Abe, A Takeshita, H Ueno
European journal of biochemistry, 1999Wiley Online Library
The signaling components located downstream of the transforming growth factor (TGF)‐β
receptor are poorly understood. We constructed adenoviral vectors expressing a dominant‐
negative form of either H‐Ras (AdCARasY57) or Rac (AdCARacN17), and used them to
examine the roles of H‐Ras and Rac in TGF‐β signaling using arterial endothelial cells in
primary culture, and several established cells including a mink lung epithelial cell line
(Mv1Lu). The rapid activation of p42/44 MAP kinase (MAPK) by TGF‐β1 was eliminated …
The signaling components located downstream of the transforming growth factor (TGF)‐β receptor are poorly understood. We constructed adenoviral vectors expressing a dominant‐negative form of either H‐Ras (AdCARasY57) or Rac (AdCARacN17), and used them to examine the roles of H‐Ras and Rac in TGF‐β signaling using arterial endothelial cells in primary culture, and several established cells including a mink lung epithelial cell line (Mv1Lu). The rapid activation of p42/44 MAP kinase (MAPK) by TGF‐β1 was eliminated completely, and transcriptional activation by TGF‐β1 of the plasminogen activator inhibitor‐1 gene was reduced by 50% in both endothelial cells and Mv1Lu when they were infected with AdCARasY57. However, the antiproliferative effect of TGF‐β, as assessed by the induction of the mRNA for Cdk4/6‐specific inhibitor p15INK4B and by DNA synthesis, was not affected in AdCARasY57‐infected cells. A MAPK kinase (MEK)1/2 inhibitor, U0126 also abolished MAPK activation and partially inhibited transcriptional activation by TGF‐β, suggesting that MAPK may be partially involved in this pathway. MAPK activation, transcriptional activation and growth suppression by TGF‐β were all unaffected in cells infected with AdCARacN17, although the DNA synthesis elicited by serum mitogens was suppressed completely in the infected cells. Our data indicate that H‐Ras is essential for mitogen‐activated protein kinase activation, partly required for transcriptional activation by TGF‐β, but not critically involved in the signaling that exerts the antiproliferative effect of TGF‐β. The results also suggest that Rac may not serve as an essential molecule in signaling by TGF‐β in the cells tested.
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