Unidad de Fisiopatología Renal y Cardiovascular, Instituto “Reina Sofía” de Investigación Nefrológica, Departamento de Fisiología y Farmacología, Universidad de Salamanca, Salamanca, Spain.
Am J Physiol Cell Physiol. 2012 Feb 15;302(4):C686-97. doi: 10.1152/ajpcell.00103.2011. Epub 2011 Nov 16.
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.
Ras GTPases 是细胞外刺激的普遍存在的质膜转导蛋白。除了作为癌基因的作用外，Ras GTPases 还是细胞功能的关键调节剂。每种 Ras 同工型在不同的细胞途径中表现出特定的调节活性。这促使研究人员确定每种同工型的病理生理作用。转化生长因子-β1 (TGF-β1) 的信号通路与 Ras GTPases 之间存在已证实的关系。为了评估 H-Ras 癌基因在基础和 TGF-β1 介导的细胞外基质 (ECM) 合成、增殖和迁移中的个体作用，我们分析了来自 H-Ras 敲除小鼠 (H-ras(-/-)) 的胚胎成纤维细胞中的这些过程。我们发现 H-ras(-/-) 成纤维细胞的基础磷脂酰肌醇-3-激酶 (PI3K)/Akt 激活比野生型 (WT) 成纤维细胞更高，而两种类型的细胞中 MEK/ERK 1/2 激活相似。H-ras(-/-) 成纤维细胞中的纤连蛋白和胶原蛋白合成更高，增殖率低于 WT 成纤维细胞。此外，H-Ras 似乎是维持正常成纤维细胞迁移所必需的，而 H-ras(-/-) 细胞中的迁移受到高度限制。这些结果表明，H-Ras（通过下调 PI3K/Akt 激活）可以通过减少 ECM 合成和上调增殖和迁移来调节成纤维细胞活性。TGF-β1 强烈增加 WT 但不增加 H-ras(-/-) 成纤维细胞中的 ERK 和 Akt 激活，表明 H-Ras 是增加 ERK 1/2 激活和维持 TGF-β1 刺激的成纤维细胞中 PI3K 下调所必需的。TGF-β1 刺激 ECM 合成和增殖，尽管 ECM 合成在 H-ras(-/-) 成纤维细胞中高于 WT 成纤维细胞，而增殖率低于 WT 成纤维细胞。因此，H-Ras 的激活似乎在调节这些作用中起着关键作用。
