|Budget Amount *help
¥2,700,000 (Direct Cost : ¥2,700,000)
Fiscal Year 1999 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 1998 : ¥1,800,000 (Direct Cost : ¥1,800,000)
Ras family is a subfamily of low molecular weight GTP-binding protein and consists of Ras, R-Ras, Ral and Rap. To compare the biological roles of two highly homologous proteins, Ras and R-Ras, IL-3-dependent hematopoietic BaF3 cells and C2C12 myoblasts were utilized. R-Ras, as well as Ras, was found to suppress apoptosis of BaF3 cells upon IL-3 withdrawal. The difference between the two molecules was that activation of Ras alone was enough to inhibit apoptosis, while R-Ras required IGF-1. Further studies. revealed that the observed difference was due to the lack of ERK-activating activity in R-Ras. In the case of C2C12 cells, activation of Ras and R-Ras resulted in different phenotypes. R-Ras promoted differentiation of C2C12 cells, whereas Ras inhibited it. On the other hand, Ras was found to be involved in chemotaxis of C2C12 cells by FGF, HGF and IGF-1, while involvement of R-Ras in the chemotaxis was unlikely since activation of R-Ras was not induced by the three growth factors. Thus, the present study show that Ras and R-Ras play a similar role in survival of hematopoietic cells, but distinct roles in myogenesis.
The relation between Ras and Ral was also examined. Since RalGEF is a Ras effector, existence of the Ras > RalGEF > Ral pathway has been indicated. To examine a role of Ral in Ras-induced cellular transformation, effect of expression of Ral mutants on Ras-dependent anchorage-independent growth was investigated using human fibrosarcoma HT1080 cells. As a result, it was suggested that Ral is involved in Ras-induced anchorage-independent growth of HT1080 cells and that Ral may modulate the anchorage-independent growth through regulation of the amount of a cell cycle inhibitor, p27Kip1.