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Viral proteins expressed on the surface of murine leukemia cells
Abstract:
Leukemic cells of AKR mice contain as constituents of their membranes the murine leukemia virus envelope protein gp70 and the precursor polyprotein of the viral internal (core) structural proteins. Both gp70 and the core polyprotein are represented on the cell surface as glycoproteins, as evidenced by incorporation of [3H]glucosamine into their structure and the binding of these proteins to lectins. The glycosylated core polyprotein exists in at least two serologically distinguishable forms: the 95,000-dalton polyprotein reacts with antisera prepared against the viral proteins p30, p12, and p10, whereas the 85,000-dalton polyprotein reacts with antisera prepared against the viral proteins p30 and p12, but not p10. Additional heterogeneity in these cell surface polyproteins has been observed wtih leukemias induced by exogenous leukemia viruses. Spontaneous leukemia cells of AKR mice invariably express gp70 and the core polyprotein on their cell surface; normal thymocytes of young AKR mice express gp70, but not the core polyprotein on their surface.
Insights
AKR mouse leukemia cells express viral glycoproteins gp70 and core polyproteins on their surface. Normal thymocytes express gp70 but lack the core polyprotein, indicating distinct cell surface protein profiles in leukemia.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Murine leukemia viruses (MLVs) are associated with leukemogenesis in mice.
- Viral envelope protein gp70 and internal core structural proteins are key viral components.
- Cell surface expression of viral proteins can influence host immune responses and disease progression.
Purpose of the Study:
- To characterize the cell surface expression of viral proteins in AKR mouse leukemia.
- To investigate the glycosylation status and heterogeneity of viral core polyproteins.
- To compare protein expression between leukemic and normal thymocytes.
Main Methods:
- Radioisotope labeling with [3H]glucosamine to assess glycosylation.
- Lectin binding assays to detect glycoproteins.
- Serological analysis using antisera against specific viral proteins (p30, p12, p10).
Main Results:
- Leukemic AKR mouse cells express both gp70 and precursor viral core polyproteins on their surface as glycoproteins.
- The core polyprotein exists in at least two serologically distinct forms (95,000-dalton and 85,000-dalton) with differential reactivity to antisera.
- Normal thymocytes express gp70 but not the core polyprotein, while leukemic cells express both.
Conclusions:
- AKR mouse leukemia cells exhibit a distinct cell surface proteome characterized by the presence of MLV envelope and core proteins.
- The heterogeneity observed in core polyproteins may reflect post-translational modifications or differential processing.
- Differential expression of these viral proteins on leukemic versus normal cells suggests their potential role in leukemia development and immune evasion.