Specific desensitization of the epidermal growth factor receptor by pp60v-src
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G M Gray1, C N Wei, I G Macara
1Division of Toxicology, Environmental Health Sciences Center, University of Rochester Medical Center, New York 14642.
Abstract:
BALB/c 3T3 cells infected with a temperature-sensitive mutant (LA90) of RSV have been used to investigate possible heterologous interactions between the pp60v-src tyrosyl kinase and the epidermal growth factor (EGF) and bradykinin receptors. The LA90 pp60v-src exhibits a very rapid activation t1/2 (less than 5 min) of protein kinase activity on decreasing the temperature from 40 degrees C to 35 degrees C. This change in temperature was also found to induce a very rapid decrease in the affinity for 125I-EGF of receptors on the RSV-LA90-infected cells but not of those on control parental cells. However, no significant changes were detected in the binding of 3H-bradykinin to either cell line. Two separable processes control the desensitization of the EGF receptor by pp60v-src, both of which are independent of protein kinase C. The first is rapid and transient, while the second is sensitive to cycloheximide and persists long after inactivation of pp60v-src.
Insights
This study reveals how Rous sarcoma virus (RSV) pp60v-src protein kinase rapidly affects epidermal growth factor (EGF) receptor affinity in infected cells. These interactions involve two distinct, protein kinase C-independent desensitization processes.
Area of Science:
- Cell biology
- Molecular oncology
- Virology
Background:
- Investigating heterologous interactions between viral proteins and cellular receptors is crucial for understanding oncogenesis.
- The pp60v-src protein kinase, encoded by Rous sarcoma virus (RSV), is a key player in viral transformation and cellular signaling.
- Epidermal growth factor (EGF) and bradykinin receptors are critical for cell growth and response to external stimuli.
Purpose of the Study:
- To explore the heterologous interactions between RSV pp60v-src tyrosyl kinase and cellular receptors, specifically the epidermal growth factor (EGF) and bradykinin receptors.
- To elucidate the mechanisms by which pp60v-src influences receptor function and cellular signaling pathways.
Main Methods:
- Utilized BALB/c 3T3 cells infected with a temperature-sensitive mutant (LA90) of RSV.
- Assessed protein kinase activity of LA90 pp60v-src at different temperatures (40°C vs. 35°C).
- Measured the binding affinity of 125I-EGF and 3H-bradykinin to receptors on infected and control cells.
Main Results:
- Rapid activation of pp60v-src protein kinase activity observed upon temperature shift from 40°C to 35°C (t1/2 < 5 min).
- Significant decrease in 125I-EGF receptor binding affinity in RSV-LA90-infected cells, but not in control cells.
- No significant changes detected in 3H-bradykinin receptor binding in either cell line.
- Identified two distinct, protein kinase C-independent processes controlling EGF receptor desensitization by pp60v-src.
Conclusions:
- RSV pp60v-src kinase rapidly modulates EGF receptor affinity, impacting cellular signaling.
- EGF receptor desensitization by pp60v-src involves two separable, protein kinase C-independent mechanisms.
- Further research into these interactions can reveal novel therapeutic targets in viral oncogenesis.