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pp60c-src is a substrate for phosphorylation when cells are stimulated to enter cycle
Abstract:
The endogenous cellular oncogene products, pp60c-src, exhibits a protein kinase activity, but is itself a phosphoprotein. Based on the assumption that pp60c-src might play a role in the control of cell proliferation, we have studied its behaviour as a substrate for phosphorylation known to occur when quiescent, serum-deprived cells are stimulated to enter cell cycle following addition of either serum, platelet-derived growth factor or the phorbol ester derivative, 12-O-tetradecanoyl-phorbol-13-acetate. For this purpose a partial purification of pp60c-src on DEAE ion-exchange chromatography was combined with immune precipitation. A 2-4-fold increase in serine phosphorylation of pp60c-src was consistently observed after stimulation of quiescent cells to growth.
Insights
The cellular oncogene pp60c-src (proto-oncogene c-Src) shows increased serine phosphorylation when quiescent cells are stimulated to proliferate. This suggests a role for pp60c-src in cell cycle control.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncogenes
Background:
- The proto-oncogene c-Src (pp60c-src) is an endogenous cellular oncogene product.
- pp60c-src possesses protein kinase activity and is itself a phosphoprotein.
Purpose of the Study:
- To investigate the role of pp60c-src in cell proliferation control.
- To study the phosphorylation of pp60c-src as a substrate during cell cycle entry.
Main Methods:
- Partial purification of pp60c-src using DEAE ion-exchange chromatography.
- Immune precipitation techniques were employed.
- Analysis of pp60c-src phosphorylation in quiescent cells stimulated with serum, platelet-derived growth factor, or 12-O-tetradecanoyl-phorbol-13-acetate.
Main Results:
- A 2-4 fold increase in serine phosphorylation of pp60c-src was consistently observed.
- Phosphorylation levels increased upon stimulation of quiescent cells to enter the cell cycle.
Conclusions:
- pp60c-src phosphorylation is enhanced when cells are stimulated to grow.
- These findings support the hypothesis that pp60c-src plays a role in the regulation of cell proliferation.