Visit our Expo - Redox and Inflammation signaling 2012

Session III : Protein kinase cascades as therapeutic targets Poster III, 21
H- and N-Ras isoforms modulate transforming growth factor-beta 1-induced
proliferation and extracellular matrix síntesis.
Isabel Fuentes-Calvo, Begoña Cenador, Alejandro Esteller, Eugenio Santos1, José M.
López-Novoa and Carlos Martínez-Salgado2.
Departamento de Fisiología y Farmacología, Universidad de Salamanca, Avda. Campo
Charro s/n, 37007 Salamanca, 1Centro de Investigación del Cáncer, Campus Miguel de
Unamuno s/n, 37007 Salamanca, and 2Unidad de Investigación, Hospital Universitario
de Salamanca, Paseo San Vicente 58-182, 37007 Salamanca.
Transforming growth factor beta 1 (TGF-beta 1) has a relevant role in the origin and
maintenance of glomerulosclerosis (GSC) and tubule-interstitial fibrosis (TIF). Ras proteins
are small GTPases with prooncogenic effect that act as transducers of extracellular signals
that regulate cell survival, growth and differentiation. TGF-beta and Ras signalling pathways
are close related: TGF-ß1 overcomes Ras mitogenic effects and Ras counteracts TGF-beta
signalling. TIF 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-ß1-mediated 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 bigger after stimulation with
TGF-beta 1. TGF-beta 1-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 can suggest that H- and N-ras isoforms down-regulate 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.
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