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Identification and characterization of a cytoskeleton-associated, epidermal growth factor sensitive pp60c-src
M C Maa1, L K Wilson, J S Moyers
1Department of Microbiology, University of Virginia Health Sciences Center, Charlottesville 22908.
Oncogene
|December 1, 1992
Summary
Researchers identified a 75-kDa protein (p75) as a substrate of pp60c-src, crucial for enhanced responses to epidermal growth factor (EGF). This protein
Area of Science:
- Cell Biology
- Molecular Biology
- Signal Transduction
Background:
- Epidermal Growth Factor (EGF) stimulation enhances mitogenic responses in fibroblasts overexpressing c-src.
- Identifying specific substrates of pp60c-src is key to understanding this enhanced response.
Purpose of the Study:
- To identify and characterize pp60c-src substrates involved in the enhanced mitogenic response to EGF.
- To investigate the role of a 75-kDa protein (p75) as a potential substrate.
Main Methods:
- Overexpression of c-src in murine C3H10T1/2 fibroblasts.
- Stimulation with growth factors (EGF, PDGF, insulin, FGF).
- Immunological assays, phosphotyrosine content analysis, Western blotting.
- Cellular fractionation and immunofluorescence microscopy.
Main Results:
- A 75-kDa protein (p75) was identified as a pp60c-src substrate, showing increased phosphotyrosine content upon EGF stimulation.
- p75 undergoes rapid and prolonged tyrosyl phosphorylation after EGF treatment, suggesting roles in both early and late cellular events.
- Phosphorylation is dependent on membrane-associated, enzymatically active pp60c-src and shows differential responses to various growth factors.
- p75 localizes with pp60c-src at the plasma membrane and perinuclear region, with partial co-staining for actin.
Conclusions:
- p75 is a direct substrate of pp60c-src, playing a significant role in the enhanced response to EGF.
- The findings provide insights into the molecular mechanisms underlying c-src-mediated cell growth regulation.