Interaction of Bordetella adenylate cyclase toxin with complement receptor 3 involves multivalent glycan binding

Area of Science:

• Microbiology
• Immunology
• Glycobiology

Background:

• Bordetella pertussis adenylate cyclase toxin (CyaA) is a key virulence factor.
• Complement receptor 3 (CR3, CD11b/CD18) is a cell surface receptor involved in immune responses.
• CyaA interacts with CR3, but the specific molecular determinants are not fully understood.

Purpose of the Study:

• To investigate the role of N-linked oligosaccharide chains (N-glycans) on CR3 in the interaction with CyaA.
• To determine which specific N-glycans on CR3 are critical for CyaA binding and cytotoxic activity.

Main Methods:

• Site-directed mutagenesis was used to substitute asparagine residues in CR3 N-glycosylation sites with glutamine.
• CR3 mutant variants were analyzed for CyaA binding and cytotoxic effects.
• Mass spectrometry was employed to analyze the N-glycosylation patterns of CR3.

Main Results:

• N-glycans located in the C-terminal region of the CD11b subunit of CR3 are essential for CyaA binding.
• These specific N-glycans are critical for the cytotoxic activity of CyaA.
• Mutating these N-glycosylation sites significantly reduced or abolished CyaA's effects.

Conclusions:

• N-glycans on the C-terminal CD11b subunit of CR3 form a specific patch for CyaA interaction.
• This interaction involves multivalent contacts, enhancing the affinity and specificity between CR3 and CyaA.
• Targeting these N-glycans could be a strategy to inhibit CyaA virulence.