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R-ras interacts with rasGAP, neurofibromin and c-raf but does not regulate cell growth or differentiation
I Rey1, P Taylor-Harris, H van Erp
1Chester Beatty Laboratories, Institute of Cancer Research, London, UK.
Abstract:
Within the superfamily of ras-related GTP-binding proteins, only ras itself has been shown to act as an oncogene. Seven other proteins, however, have greater than 50% amino acid identity to ras and one of them, rap1A, has been shown to interact with the ras GTPase activating protein, ras-GAP, and to inhibit ras function when overexpressed. In this paper, we have examined the biological and biochemical activities of another close relative of ras, R-ras. We show that in vitro, R-ras shares a number of activities with ras; it interacts with the catalytic domain of ras-GAP, with the GAP-related domain of neurofibromin and with the ser/thr kinase, c-raf. Furthermore, R-ras stimulates the expression of c-fos when microinjected into Swiss 3T3 cells. However, unlike ras, R-ras does not include DNA synthesis or membrane ruffling in quiescent fibroblasts, nor does it induce maturation of Xenopus oocytes or differentiation of PC12 cells. In addition, we show that unlike rap1A, R-ras does not interfere with ras-stimulated gene transcription. We conclude from these experiments that although R-ras and ras share some biochemical activities, they control distinct biological processes.
Insights
R-ras shares biochemical activities with ras, interacting with key proteins like ras-GAP and c-raf. However, R-ras controls distinct biological processes, unlike ras, and does not affect ras-stimulated gene transcription.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncogenes
Background:
- Ras-related GTP-binding proteins are crucial in cell signaling.
- Ras is the only known oncogene in this superfamily.
- R-ras is a close relative of ras with high amino acid identity.
Purpose of the Study:
- To investigate the biological and biochemical activities of R-ras.
- To compare R-ras function with that of ras and rap1A.
- To determine if R-ras influences ras-mediated signaling pathways.
Main Methods:
- In vitro biochemical assays to assess protein interactions.
- Microinjection into Swiss 3T3 cells to study gene expression.
- Functional assays in fibroblasts, Xenopus oocytes, and PC12 cells.
Main Results:
- R-ras interacts with ras-GAP, neurofibromin, and c-raf in vitro.
- R-ras stimulates c-fos expression in Swiss 3T3 cells.
- R-ras does not induce DNA synthesis, membrane ruffling, oocyte maturation, or PC12 cell differentiation.
Conclusions:
- R-ras exhibits some biochemical similarities to ras.
- R-ras regulates distinct biological processes separate from ras.
- R-ras does not interfere with ras-stimulated gene transcription, unlike rap1A.