Involvement of H- and N-Ras isoforms in transforming growth factor-beta1-induced proliferation and in collagen and fibronectin synthesis.
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.
Martínez-Salgado
Carlos
C
Unidad de Investigación, Hospital Universitario de Salamanca, Salamanca, Spain. carloms@usal.es
Fuentes-Calvo
Isabel
I
García-Cenador
Begoña
B
Santos
Eugenio
E
López-Novoa
José M
JM
D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis* / Q000187:drug effects; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis; D005347:Fibroblasts / Q000187:drug effects; D005353:Fibronectins / Q000096:biosynthesis* / Q000187:drug effects; D011905:Genes, ras / Q000502:physiology*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006579:Heterozygote; D051379:Mice; D018345:Mice, Knockout; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology; D051058:Oncogene Protein v-akt / Q000502:physiology; D020033:Protein Isoforms / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1; D018631:ras Proteins / Q000378:metabolism
D016326:Extracellular Matrix Proteins; D005353:Fibronectins; D020033:Protein Isoforms; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D006160:Guanosine Triphosphate; D003094:Collagen; D051058:Oncogene Protein v-akt; D048052:Mitogen-Activated Protein Kinase 3; D018631:ras Proteins