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Internalization of virus binding proteins during entry of reovirus into K562 erythroleukemia cells
1Division of Clinical Virology, J. N. Gamble Institute of Medical Research, Cincinnati, Ohio 45219.
Abstract:
Virus overlay protein blot assays of cell membranes of mouse L929 fibroblasts have revealed multiple reovirus binding proteins with molecular masses ranging from approximately 26 to 200 kDa. To determine whether this observation is unique to L cells, membranes of human K562 erythroleukemia cells and human A431 epidermoid cells were subjected to virus overlay protein blot assays. The profiles of reovirus binding proteins of these cells are similar to that of L cells and reovirus is capable of binding to at least 30 membrane proteins. To determine the fate of reovirus binding proteins during viral entry into K562 cells which are infectible by reovirus, cell surface proteins were derivatized with biotin. During viral entry, biotinylated cell surface proteins with molecular masses of 55, 74, 78, 80, 90, 94, 98, and 115 kDa became internalized. The 90- and 115-kDa proteins also bound reovirus, indicating that they are likely to be reovirus receptors. Thus many virus binding proteins are present at the surface of host cells but very few are internalized during entry of reovirus. K562 cells also express glycophorin A which is the putative reovirus receptor on erythrocytes. However, during entry of reovirus into K562 cells, glycophorin A did not appear to become internalized. Reovirus could be shown to attach to erythrocytes but viral entry into these cells could not be demonstrated.
Insights
Reovirus binds to numerous cell surface proteins across different cell types. However, only specific proteins are internalized during viral entry, suggesting a selective process for reovirus infection.
Area of Science:
- Virology
- Cell Biology
- Molecular Biology
Background:
- Reovirus binding to host cells is mediated by cell surface proteins.
- Previous studies identified multiple reovirus binding proteins on mouse L929 fibroblasts.
Purpose of the Study:
- To investigate the diversity of reovirus binding proteins on human cell lines.
- To identify reovirus binding proteins that are internalized during viral entry.
- To determine the role of glycophorin A in reovirus entry into K562 cells.
Main Methods:
- Virus overlay protein blot assays were performed on L929, K562, and A431 cell membranes.
- Cell surface proteins of K562 cells were biotinylated to track internalization during reovirus entry.
- Reovirus attachment and entry into erythrocytes were also assessed.
Main Results:
- Reovirus binds to at least 30 membrane proteins in L929, K562, and A431 cells.
- Specific biotinylated proteins (55, 74, 78, 80, 90, 94, 98, 115 kDa) were internalized during reovirus entry into K562 cells.
- 90- and 115-kDa proteins, which bind reovirus, are likely receptors; glycophorin A was not internalized.
- Reovirus attached to erythrocytes but did not enter.
Conclusions:
- Multiple cell surface proteins bind reovirus, but internalization is selective.
- Specific internalized proteins, notably 90- and 115-kDa, are likely reovirus receptors.
- Glycophorin A is not significantly involved in reovirus entry into K562 cells, despite binding capacity.