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Absence of K‐Ras Reduces Proliferation and Migration But Increases Extracellular Matrix Synthesis in Fibroblasts

The involvement of Ras‐GTPases in the development of renal fibrosis has been addressed in the last decade. We have previously shown that H‐ and N‐Ras isoforms participate in the regulation of fibrosis. Herein, we assessed the role of K‐Ras in cellular processes involved in the development of fibrosis: proliferation, migration, and extracellular matrix (ECM) proteins synthesis. K‐Ras knockout (KO) mouse embryonic fibroblasts (K‐ras−/−) stimulated with transforming growth factor‐β1 (TGF‐β1) exhibited reduced proliferation and impaired mobility than wild‐type fibroblasts. Moreover, an increase on ECM production was observed in K‐Ras KO fibroblasts in basal conditions. The absence of K‐Ras was accompanied by reduced Ras activation and ERK phosphorylation, and increased AKT phosphorylation, but no differences were observed in TGF‐β1‐induced Smad signaling. The MEK inhibitor U0126 decreased cell proliferation independently of the presence of K‐ras but reduced migration and ECM proteins expression only in wild‐type fibroblasts, while the PI3K‐AKT inhibitor LY294002 decreased cell proliferation, migration, and ECM synthesis in both types of fibroblasts. Thus, our data unveil that K‐Ras and its downstream effector pathways distinctively regulate key biological processes in the development of fibrosis. Moreover, we show that K‐Ras may be a crucial mediator in TGF‐β1‐mediated effects in this cell type. J. Cell. Physiol. 231: 2224–2235, 2016. © 2016 Wiley Periodicals, Inc.