Human tandem-repeat-type galectins bind bacterial non-βGal polysaccharides.

Area of Science:

• Glycobiology
• Immunology
• Microbiology

Background:

• Galectins are key regulators of cellular processes through protein-glycan interactions.
• Certain galectins exhibit antibacterial properties by targeting histo-blood group epitopes.
• The precise carbohydrate-binding specificities of galectins beyond β-galactosides remain incompletely understood.

Purpose of the Study:

• To investigate whether carbohydrate determinants other than β-galactosides serve as binding sites for human galectins.
• To explore the binding capabilities of human galectins-4, -8, and -9 to a diverse array of bacterial polysaccharides.
• To assess the potential of a novel array-based screening tool for identifying galectin-carbohydrate interactions.

Main Methods:

• Construction and utilization of an array containing various bacterial polysaccharides.
• Testing the binding activity of human galectins (galectin-4, -8, -9) against the polysaccharide array.
• Inclusion of positive controls (histo-blood group ABH-epitopes, E. coli 086 polysaccharide) to validate the experimental setup.

Main Results:

• Significant galectin binding signals were detected, varying with specific galectin and polysaccharide combinations.
• Binding was observed even for polysaccharides lacking typical β-galactoside structures, such as rhamnan.
• The presence of β-galactoside-related epitopes did not guarantee binding, indicating complex recognition mechanisms.

Conclusions:

• The developed array serves as a valuable tool for screening galectin-carbohydrate interactions.
• Human galectins can bind to bacterial polysaccharides through determinants beyond β-galactosides.
• These findings provide crucial direction for future functional and structural studies of galectin-mediated immunity and bacterial interactions.