Related Experiment Videos
Inhibition of epidermal growth factor-induced cellular proliferation
Abstract:
The authors tested whether two oncogenic poxviruses, Shope fibroma virus (SFV) and malignant rabbit fibroma virus (MV), coded for an epidermal growth factor (EGF)-like protein. Virus-free lysates of SFV or MV-infected rabbit kidney cells do not appreciably affect proliferation of EGF-unresponsive RK-13 cells. Comparable lysates inhibit the background proliferation of two EGF-responsive cell lines, human foreskin fibroblasts and normal rat kidney cells. Inhibition of EGF-stimulated proliferation is also observed in a dose-dependent fashion. This inhibition is greatest when the virus lysate preparations are added either simultaneously with or before EGF. When EGF is added to cultures 24 hours before the SFV or MV preparations, the latter then have little or no effect on EGF-induced target cell proliferation. The inhibitory factor competed with radiolabeled EGF for its receptor site. Electroblotting shows a protein of 35 kd molecular weight in the lysates of virus-infected RK-13 cells which reacts with anti-EGF antibody. These findings interpreted to indicate that SFV and MV code for an inhibitor of EGF activity, and that this inhibition occurs at least in part by competitive inhibition of EGF-EGF receptor interactions.
Insights
Two oncogenic poxviruses, Shope fibroma virus (SFV) and malignant rabbit fibroma virus (MV), produce a protein that inhibits epidermal growth factor (EGF) activity by blocking EGF receptor interactions.
Area of Science:
- Virology
- Cell Biology
- Molecular Biology
Background:
- Oncogenic poxviruses Shope fibroma virus (SFV) and malignant rabbit fibroma virus (MV) are known to infect rabbits.
- Epidermal growth factor (EGF) is a crucial signaling molecule regulating cell proliferation.
Purpose of the Study:
- To investigate whether SFV and MV encode proteins that interfere with EGF signaling.
- To characterize the mechanism of this interference.
Main Methods:
- Infection of rabbit kidney cells with SFV or MV.
- Preparation of virus-free cell lysates.
- Assessing the effect of lysates on the proliferation of EGF-responsive and unresponsive cell lines.
- Competition assays with radiolabeled EGF.
- Electroblotting to detect viral proteins reacting with anti-EGF antibody.
Main Results:
- Lysates from SFV- or MV-infected cells inhibited the proliferation of EGF-responsive cells, but not EGF-unresponsive cells.
- Inhibition was dose-dependent and most effective when lysates were added before or with EGF.
- A 35 kDa protein in infected cell lysates reacted with anti-EGF antibody.
- The inhibitory factor competed with EGF for its receptor.
Conclusions:
- SFV and MV encode an inhibitor of EGF activity.
- This inhibition occurs, at least partly, through competitive inhibition of EGF-EGF receptor interactions.
- The identified viral protein is likely responsible for the observed inhibition of EGF signaling.