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Glycoprotein tyrosine phosphorylation in Rous sarcoma virus-transformed chicken embryo fibroblasts
L M Kozma1, A B Reynolds, M J Weber
1Department of Microbiology and Cancer Center, University of Virginia School of Medicine, Charlottesville 22908.
Abstract:
The level of tyrosine phosphorylation of cellular glycoproteins isolated by wheat germ agglutinin chromatography in cells infected with a variety of kinase-positive/transformation-defective src mutants was examined in an effort to identify cellular membrane proteins whose phosphorylation correlates with phenotypic transformation. We have identified two glycoproteins, with molecular masses of 95 and 135 kilodaltons, whose phosphorylation correlates with morphological transformation, growth in soft agar, and an increase in the rate of 2-deoxyglucose uptake. The strong correlation obtained between transformation and phosphorylation of these proteins suggests that they may be substrates for pp60src which are important in the process of transformation.
Insights
Researchers identified two key glycoproteins whose increased tyrosine phosphorylation correlates with cell transformation. This finding suggests these proteins are important substrates for pp60src in driving cellular changes.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- Cellular transformation is a complex process often driven by viral oncogenes like src.
- Understanding the molecular mechanisms of transformation requires identifying key cellular targets of oncogenic proteins.
Purpose of the Study:
- To identify cellular membrane glycoproteins whose tyrosine phosphorylation levels correlate with phenotypic transformation induced by src mutants.
- To investigate potential substrates of pp60src involved in the transformation process.
Main Methods:
- Wheat germ agglutinin chromatography was used to isolate cellular glycoproteins.
- Tyrosine phosphorylation levels of isolated glycoproteins were analyzed in cells infected with kinase-positive/transformation-defective src mutants.
Main Results:
- Two specific glycoproteins, with molecular masses of 95 and 135 kilodaltons, showed increased tyrosine phosphorylation.
- This phosphorylation strongly correlated with morphological transformation, anchorage-independent growth (soft agar), and increased glucose uptake.
Conclusions:
- The identified 95 and 135 kDa glycoproteins are likely substrates of pp60src.
- Their phosphorylation appears critical for mediating key aspects of cellular transformation, including altered morphology and metabolism.