Carbohydrate-carbohydrate binding of ganglioside to integrin alpha(5) modulates alpha(5)beta(1) function

Area of Science:

• Cell Biology
• Biochemistry
• Glycobiology

Background:

• Gangliosides GT1b and GD3 are key components of keratinocyte membranes.
• These gangliosides are known to inhibit keratinocyte adhesion to fibronectin.
• The precise mechanism behind this inhibitory effect remains unclear.

Purpose of the Study:

• To elucidate the mechanism by which gangliosides GT1b and GD3 inhibit keratinocyte adhesion to fibronectin.
• To investigate the interaction between gangliosides and alpha(5)beta(1) integrin.
• To identify the specific molecular components involved in this interaction.

Main Methods:

• Utilized purified insect recombinant alpha(5) and beta(1) proteins and alpha(5)beta(1) integrin from SCC12 cells.
• Performed co-immunoprecipitation assays to detect GT1b and alpha(5)beta(1) interactions.
• Conducted direct binding assays with purified gangliosides and integrin.
• Investigated the role of carbohydrate moieties using deglycosylated integrin forms.
• Employed concanavalin A inhibition assays to probe carbohydrate binding specificities.

Main Results:

• GT1b and GD3 were shown to inhibit the binding of alpha(5)beta(1) integrin to fibronectin.
• Direct binding was observed between GT1b/GD3 and alpha(5)beta(1) integrin, particularly the alpha(5) subunit.
• Ganglioside binding to alpha(5)beta(1) integrin was dependent on the carbohydrate moieties of the integrin.
• Concanavalin A inhibited the GT1b-alpha(5)beta(1) interaction, indicating binding to mannose structures.
• GT1b preferentially bound to high-mannose structures on the integrin.

Conclusions:

• Highly sialylated gangliosides regulate alpha(5)beta(1) integrin-mediated epithelial cell adhesion to fibronectin.
• The mechanism involves carbohydrate-carbohydrate interactions between gangliosides (e.g., GT1b) and mannose structures on the alpha(5) subunit of alpha(5)beta(1) integrin.