Martínez-Salgado Carlos, Fuentes-Calvo Isabel, García-Cenador Begoña, Santos Eugenio, López-Novoa José M
Unidad de Investigación, Hospital Universitario de Salamanca, Salamanca, Spain.
Exp Cell Res. 2006 Jul 1;312(11):2093-106. doi: 10.1016/j.yexcr.2006.03.008. Epub 2006 Apr 19.
Transforming growth factor beta1 (TGF-beta1) has a relevant role in the origin and maintenance of glomerulosclerosis and tubule-interstitial fibrosis. TGF-beta and Ras signaling pathways are closely related: TGF-beta1 overcomes Ras mitogenic effects and Ras counteracts TGF-beta signaling. Tubule-interstitial fibrosis is associated to increases in Ras, Erk, and Akt activation in a renal fibrosis model. We study the role of N- and H-Ras isoforms, and the involvement of the Ras effectors Erk and Akt, in TGF-beta1-mediated extracellular matrix (ECM) synthesis and proliferation, using embrionary fibroblasts from double knockout (KO) mice for H- and N-Ras (H-ras(-/-)/N-ras(-/-)) isoforms and from heterozygote mice (H-ras(+/-)/N-ras(+/-)). ECM synthesis is increased in basal conditions in H-ras(-/-)/N-ras(-/-) fibroblasts, this increase being higher after stimulation with TGF-beta1. TGF-beta1-induced fibroblast proliferation is smaller in H-ras(-/-)/N-ras(-/-) than in H-ras(+/-)/N-ras(+/-) fibroblasts. Erk activation is decreased in H-ras(-/-)/N-ras(-/-) fibroblasts; inhibition of Erk activation reduces fibroblast proliferation. Akt activation is higher in double KO fibroblasts than in heterozygotes; inhibition of Akt activation also inhibits ECM synthesis. We suggest that H- and N-Ras isoforms downregulate ECM synthesis, and mediate proliferation, in part through MEK/Erk activation. PI3K-Akt pathway activation may be involved in the increase in ECM synthesis observed in the absence of H- and N-Ras.
转化生长因子β1（TGF-β1）在肾小球硬化和肾小管间质纤维化的发生及维持过程中发挥着重要作用。TGF-β信号通路与Ras信号通路密切相关：TGF-β1可克服Ras的促有丝分裂作用，而Ras则可对抗TGF-β信号。在肾纤维化模型中，肾小管间质纤维化与Ras、细胞外信号调节激酶（Erk）和蛋白激酶B（Akt）激活的增加有关。我们利用H-Ras和N-Ras双敲除（KO）小鼠（H-ras(-/-)/N-ras(-/-)）及杂合子小鼠（H-ras(+/-)/N-ras(+/-)）的胚胎成纤维细胞，研究了N-Ras和H-Ras亚型的作用以及Ras效应器Erk和Akt在TGF-β1介导的细胞外基质（ECM）合成和增殖中的作用。在基础条件下，H-ras(-/-)/N-ras(-/-)成纤维细胞中的ECM合成增加，在用TGF-β1刺激后这种增加更为明显。与H-ras(+/-)/N-ras(+/-)成纤维细胞相比，TGF-β1诱导的H-ras(-/-)/N-ras(-/-)成纤维细胞增殖较小。H-ras(-/-)/N-ras(-/-)成纤维细胞中的Erk激活降低；抑制Erk激活可减少成纤维细胞增殖。双敲除成纤维细胞中的Akt激活高于杂合子；抑制Akt激活也可抑制ECM合成。我们认为，H-Ras和N-Ras亚型可下调ECM合成，并部分通过丝裂原活化蛋白激酶/细胞外信号调节激酶（MEK/Erk）激活介导细胞增殖。磷脂酰肌醇-3激酶/蛋白激酶B（PI3K-Akt）信号通路的激活可能与在缺乏H-Ras和N-Ras时观察到的ECM合成增加有关。
