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Localization of viral-envelope-glycoprotein-binding sites in fibronectin
Abstract:
Purified viral-envelope glycoproteins from influenza A virus were found to bind to two fragments of the fibronectin molecule. Human plasma fibronectin was digested by leucocyte cathepsin G, and three different fragments, of Mr 30000, 40000 and 12000-140000, with specific binding functions were isolated. Micelles of radiolabelled influenza A glycoprotein were allowed to bind to these fragments immobilized on polystyrene micro-titre wells. The C-terminal 120000-14000-Mr fragments that carry the cell-binding activity bound viral proteins most efficiently, whereas the 40000-Mr gelatin-binding fragment bound considerably less. The N-terminal 30000-Mr Staphylococcus aureus-binding fragment was negative in the assays. Laminin, a basement-membrane protein, also bound viral proteins, though less effectively than fibronectin. The binding was abolished if laminin or fibronectin fragments were pretreated with neuraminidase. This suggests that the sialic acids in the sugar moieties of these glycoproteins are involved in the binding. The affinity of viral-envelope glycoproteins for certain domains of fibronectin and for laminin may play a role in virus-cell interactions.
Insights
Influenza A virus glycoproteins bind to fibronectin fragments, particularly those involved in cell adhesion. This interaction, mediated by sialic acids, may be crucial for how viruses attach to host cells.
Area of Science:
- Virology
- Biochemistry
- Cell Biology
Background:
- Influenza A virus utilizes surface glycoproteins for host cell interaction.
- Fibronectin is a key extracellular matrix protein involved in cell adhesion and signaling.
Purpose of the Study:
- To investigate the binding affinity of influenza A virus envelope glycoproteins to specific fibronectin fragments.
- To elucidate the role of fibronectin domains and sialic acids in virus-host cell interactions.
Main Methods:
- Purification of influenza A virus envelope glycoproteins.
- Enzymatic digestion of human plasma fibronectin and isolation of specific fragments.
- Binding assays using radiolabeled viral glycoproteins and immobilized fibronectin fragments.
Main Results:
- Influenza glycoproteins preferentially bound to C-terminal fibronectin fragments (120-140 kDa) associated with cell-binding activity.
- Binding to the 40 kDa gelatin-binding fragment was significantly lower.
- The N-terminal 30 kDa fragment showed no binding.
- Neuraminidase treatment abolished binding, indicating the involvement of sialic acids.
Conclusions:
- Influenza A virus glycoproteins exhibit specific binding to certain fibronectin domains, particularly those mediating cell adhesion.
- Sialic acid residues on viral glycoproteins are essential for this interaction.
- These findings suggest a potential mechanism for virus-cell attachment involving fibronectin and viral glycoproteins.