H-Ras isoform modulates extracellular matrix synthesis, proliferation, and migration in fibroblasts

Abstract

Ras GTPases are ubiquitous plasma membrane transducers of extracellular stimuli. In addition to their role as oncogenes, Ras GTPases are key regulators of cell function. Each of the Ras isoforms exhibits specific modulatory activity on different cellular pathways. This has prompted researchers to determine the pathophysiological roles of each isoform. There is a proven relationship between the signaling pathways of transforming growth factor-β1 (TGF-β1) and Ras GTPases. To assess the individual role of H-Ras oncogene in basal and TGF-β1-mediated extracellular matrix (ECM) synthesis, proliferation, and migration in fibroblasts, we analyzed these processes in embryonic fibroblasts obtained from H-Ras knockout mice ( H-ras−/−). We found that H- ras−/− fibroblasts exhibited a higher basal phosphatidylinositol-3-kinase (PI3K)/Akt activation than wild-type (WT) fibroblasts, whereas MEK/ERK 1/2 activation was similar in both types of cells. Fibronectin and collagen synthesis were higher in H -ras−/− fibroblasts and proliferation was lower in H -ras−/− than in WT fibroblasts. Moreover, H-Ras appeared indispensable to maintain normal fibroblast motility, which was highly restricted in H- ras−/− cells. These results suggest that H-Ras (through downregulation of PI3K/Akt activation) could modulate fibroblast activity by reducing ECM synthesis and upregulating both proliferation and migration. TGF-β1 strongly increased ERK and Akt activation in WT but not in H- ras−/− fibroblasts, suggesting that H-Ras is necessary to increase ERK 1/2 activation and to maintain PI3K downregulation in TGF-β1-stimulated fibroblasts. TGF-β1 stimulated ECM synthesis and proliferation, although ECM synthesis was higher and proliferation lower in H- ras−/− than in WT fibroblasts. Hence, H-Ras activation seems to play a key role in the regulation of these effects.

Effect of Angiotensin II and Small GTPase Ras Signaling Pathway Inhibition on Early Renal Changes in a Murine Model of Obstructive Nephropathy

“…Activation of Ras signaling pathway occurs after early UUO [22, 23], demonstrating a contribution of Ras downstream effectors to renal injury with a main involvement of ERK1/2 in apoptotic events and Akt in proliferative and fibrotic response [23]. There are several Ras isoforms (H-, N- and K-Ras) with different functional properties in fibrotic processes and in fibroblast biology [24–26]. Thus, we have observed that H-Ras knock-out (KO) mice show lower fibrosis after UUO [27], whereas in embryonic fibroblasts obtained from H-Ras or N-Ras KO mice, fibronectin and collagen synthesis were higher and proliferation and migration were lower than in wild type fibroblasts [24, 25].…”

“…There are several Ras isoforms (H-, N- and K-Ras) with different functional properties in fibrotic processes and in fibroblast biology [24–26]. Thus, we have observed that H-Ras knock-out (KO) mice show lower fibrosis after UUO [27], whereas in embryonic fibroblasts obtained from H-Ras or N-Ras KO mice, fibronectin and collagen synthesis were higher and proliferation and migration were lower than in wild type fibroblasts [24, 25]. Moreover, K-Ras knock-down decreases stimulated proliferation in renal fibroblasts [28] and inhibits fibrosis in a rat experimental model [29].…”

Long-term treatment with chaethomellic acid A reduces glomerulosclerosis and arteriolosclerosis in a rat model of chronic kidney disease

“…Some studies highlight the importance of Ha-Ras isoform in the development of fibrosis [4,16,17]. Therefore, we have evaluated the effect of CAA, which selectively blocks Ha-Ras farnesylation [19], on renal fibrosis.…”

“…There are three closely related major isoforms of Ras proteins: Harvey (Ha)-, Kirsten (Ki)-, and neural (N)-Ras, which are expressed in mammalian cells and have different biological effects [9,[12][13][14], namely in fibroblasts biology and fibrotic processes [6,[15][16][17]. It has been reported that depletion of Ha-Ras isoform in cultured fibroblasts obtained from Ha-Ras knock-out (KO) mice up-regulates extracellular matrix proteins (ECM) synthesis and mediates proliferation and migration by modulating PI3K/Akt and MEK/ERK activation [16,17].…”

“…It has been reported that depletion of Ha-Ras isoform in cultured fibroblasts obtained from Ha-Ras knock-out (KO) mice up-regulates extracellular matrix proteins (ECM) synthesis and mediates proliferation and migration by modulating PI3K/Akt and MEK/ERK activation [16,17]. In an in vivo study, fibrosis was lower in H-Ras KO than in wild type mice after unilateral ureteral obstruction (UUO) [4].…”