Changes in cell surface structure by viral transformation studied by binding of lectins differing in sugar...

Area of Science:

• Cell Biology
• Virology
• Biochemistry

Background:

• Viral transformation induces significant changes in cellular structures.
• Cell surface glycoproteins and glycolipids are crucial for cell-cell interactions and are often altered during viral oncogenesis.
• Lectins, proteins that bind specific carbohydrates, can be used as probes to detect these cell surface alterations.

Purpose of the Study:

• To investigate alterations in cell surface carbohydrate structures following viral transformation.
• To quantify changes in lectin binding affinities to normal versus virally transformed cells.
• To correlate specific lectin binding changes with viral-induced modifications of the cell surface.

Main Methods:

• Utilized radioiodinated (125I) lectins with defined carbohydrate specificities: Concanavalin-A (glucose/mannose), wheat germ agglutinin (N-acetylglucosamine), castor bean agglutinin (galactose), Wistaria floribunda agglutinin (N-acetylgalactosamine), and soybean agglutinin (N-acetylgalactosamine).
• Assayed direct lectin binding to cells grown on coverslips, comparing a bovine adenovirus type-3 transformed clone (SS7) with its normal counterpart (C31).
• Investigated the effect of ethylenediaminetetraacetic acid (EDTA) dispersion on lectin binding and assessed the impact of cell density on lectin binding.

Main Results:

• Transformed SS7 cells exhibited a 5-6 fold increase in Wistaria floribunda agglutinin binding compared to normal C31 cells.
• Concanavalin-A binding was approximately two-fold higher in normal cells than in transformed cells.
• Binding of soybean agglutinin, wheat germ agglutinin, and castor bean agglutinin showed no significant differences between normal and transformed cells.
• EDTA treatment reduced Wistaria floribunda agglutinin binding to transformed cells by half.
• Lectin binding per cell decreased with increasing cell density, particularly for Wistaria floribunda agglutinin on normal cells.

Conclusions:

• Viral transformation by bovine adenovirus type-3 induces specific alterations in cell surface carbohydrate expression, detectable by differential lectin binding.
• The increased Wistaria floribunda agglutinin binding suggests an upregulation or exposure of N-acetylgalactosamine residues on transformed cells.
• The decreased Concanavalin-A binding indicates a reduction or masking of accessible glucose/mannose residues on transformed cells.
• These observed changes in lectin binding sites reflect significant modifications of the cell surface structure due to viral transformation.