Related Experiment Videos
Protein turnover in 3T3 cells transformed with the oncogene c-H-ras1
1Department of Biochemistry and Biophysics, Texas A & M University, College Station 77843-2128.
Abstract:
We have examined protein turnover, growth, DNA synthesis and proliferation in three independent clones of 3T3-NR6 cells transformed with the oncogene c-H-ras1. We find that, firstly, the half-maximum concentration of serum and insulin regulating protein turnover in ras-transformed cells is significantly reduced from 0.5 to 0.3% for serum and from 4 nM to 0.5 nM for insulin, and, secondly, ras-transformed cells consistently have lower rates of protein degradation. The catabolic effect of conditioned medium or serum withdrawal is attenuated in transformed lines by maintaining lower basal rates of protein breakdown and higher basal rates of DNA and protein synthesis. Serum stimulation of growth in transformed cells is achieved in the short term by lower rates of protein breakdown rather than higher rates of protein synthesis: rates of protein synthesis become significantly higher 24 h after serum stimulation. Therefore transformed cells have higher rates of proliferation and grow to higher densities, but display characteristics common to normal cells because rates of protein synthesis decrease and protein degradation increase as a function of cell density. We conclude that higher basal rates of protein synthesis and growth with retention of the normal proliferative response to serum result from the pleiotropic nature of ras transformation, whereas lower rates of protein degradation and increased sensitivity to serum and insulin imply a direct regulatory role for ras.
Insights
Oncogene c-H-ras1 transformation in 3T3-NR6 cells reduces the need for serum and insulin for protein turnover. Ras-transformed cells exhibit lower protein degradation and enhanced growth, suggesting a direct regulatory role for ras.
Area of Science:
- Cell Biology
- Molecular Biology
- Oncology
Background:
- The oncogene c-H-ras1 plays a critical role in cell signaling pathways.
- Understanding the impact of ras transformation on cellular processes is crucial for cancer research.
Purpose of the Study:
- To investigate the effects of c-H-ras1 oncogene transformation on protein turnover, DNA synthesis, and proliferation in 3T3-NR6 cells.
- To elucidate the regulatory mechanisms by which ras transformation influences cellular growth and metabolism.
Main Methods:
- Analysis of protein turnover, DNA synthesis, and cell proliferation in three independent clones of 3T3-NR6 cells transformed with c-H-ras1.
- Quantification of half-maximum concentrations of serum and insulin regulating protein turnover.
- Assessment of protein degradation rates under various conditions, including conditioned medium and serum withdrawal.
Main Results:
- Ras-transformed cells showed a significantly reduced half-maximum concentration for serum (0.3%) and insulin (0.5 nM) in regulating protein turnover.
- Transformed cells exhibited consistently lower rates of protein degradation compared to control cells.
- The catabolic effects of conditioned medium or serum withdrawal were attenuated in ras-transformed cells due to lower basal protein breakdown and higher basal synthesis rates.
Conclusions:
- Higher basal rates of protein synthesis and growth, along with a retained proliferative response to serum, are attributed to the pleiotropic effects of ras transformation.
- Reduced protein degradation and increased sensitivity to serum and insulin suggest a direct regulatory role for the ras oncogene in these cellular processes.