Related Experiment Videos
R-Ras is regulated by activators and effectors distinct from those that control Ras function
S Y Huff1, L A Quilliam, A D Cox
1University of North Carolina at Chapel Hill, Department of Microbiology and Immunology, 27599, USA.
Abstract:
Like Ras, constitutively activated mutants of the Ras-related protein R-Ras cause tumorigenic transformation of NIH3T3 cells. However, since R-Ras causes a transformed phenotype distinct from that induced by Ras, it is likely that R-Ras controls signaling pathways and cellular processes distinct from those regulated by Ras. To address this possibility, we determined if R-Ras is regulated by activators and effectors distinct from those that regulate Ras function. We observed that Ras guanine nucleotide exchange factors failed to activate R-Ras in vivo, indicating that R-Ras is activated by distinct GEFs. Consistent with this, mutants of R-Ras with mutations analogous to the Ras(15A)/(17N) dominant negative proteins did not antagonize Ras GEF function and lacked the growth inhibitory activity seen with these mutant Ras proteins. Thus, R-Ras, but not Ras, is dispensable for the viability of NIH3T3 cells. Finally, whereas constitutively activated Ras can overcome the growth inhibitory action of the Ras(17N) dominant negative protein via Raf-dependent and -independent activities, transforming mutants of R-Ras failed to do so. This inability was consistent with our observation that Ras-, but not R-Ras-transformed, NIH3T3 cells possessed constitutively upregulated Raf kinase activities. Thus, R-Ras and Ras are regulators of distinct signaling pathways and cellular processes.
Insights
Ras and Ras-related protein R-Ras have distinct cellular roles. R-Ras regulates different signaling pathways than Ras, impacting cell viability and transformation distinctly, highlighting their unique functions in cellular processes.
Area of Science:
- Cell Biology
- Molecular Biology
- Oncology
Background:
- Ras proteins are key regulators of cell signaling and growth.
- Ras-related protein R-Ras also influences cell transformation but via distinct mechanisms.
- Understanding the differences in Ras and R-Ras signaling is crucial for cancer research.
Purpose of the Study:
- To investigate whether R-Ras is regulated by distinct activators and effectors compared to Ras.
- To elucidate the specific signaling pathways and cellular processes controlled by R-Ras.
- To compare the functional outcomes of Ras and R-Ras activation in NIH3T3 cells.
Main Methods:
- Utilized NIH3T3 cells for transformation assays.
- Employed dominant-negative mutant proteins to assess pathway interference.
- Analyzed guanine nucleotide exchange factor (GEF) activity in vivo.
- Measured Raf kinase activity in transformed cells.
Main Results:
- Ras GEFs did not activate R-Ras, indicating distinct GEFs for R-Ras.
- R-Ras mutants did not inhibit Ras GEF function or exhibit growth inhibitory activity.
- R-Ras is dispensable for NIH3T3 cell viability, unlike Ras.
- Transforming R-Ras mutants could not overcome Ras(17N) inhibition, unlike activated Ras.
- Ras-transformed cells showed upregulated Raf kinase activity, but R-Ras-transformed cells did not.
Conclusions:
- R-Ras and Ras are regulated by distinct GEFs and control separate signaling pathways.
- R-Ras and Ras modulate distinct cellular processes, including cell viability and transformation.
- These findings highlight the divergent roles of R-Ras and Ras in cellular regulation and tumorigenesis.