Recognition of Lewis x derivatives present on mucins by flagellar components of Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa binds to human respiratory mucins by mechanisms involving flagellar component-receptor interactions. The adhesion of P. aeruginosa strain PAK is mediated by the flagellar cap protein, FliD, without the involvement of flagellin. Two distinct types of FliD proteins have been identified in P. aeruginosa: A type, found in strain PAK, and B type, found in strain PAO1. In the present work, studies performed with the P. aeruginosa B-type strain PAO1 indicate that both the FliD protein and the flagellin of this strain are involved in the binding to respiratory mucins. Using polyacrylamide-based fluorescent glycoconjugates in a flow cytometry assay, it was previously demonstrated that P. aeruginosa recognizes Le(x) (or Lewis x) derivatives found at the periphery of human respiratory mucins. The aim of the present work was therefore to determine whether these carbohydrate epitopes (or glycotopes) are receptors for FliD proteins and flagellin. The results obtained by both flow cytometry and a microplate adhesion assay indicate that the FliD protein of strain PAO1 is involved in the binding of glycoconjugates bearing Le(x) or sialyl-Le(x) determinants, while the binding of flagellin is restricted to the glycoconjugate bearing Le(x) glycotope. In contrast, the type A cap protein of P. aeruginosa strain PAK is not involved in the binding to glycoconjugates bearing Le(x), sialyl-Le(x), or sulfosialyl-Le(x) glycotopes. This study demonstrates a clear association between a specific Pseudomonas adhesin and a specific mucin glycotope and demonstrates that fine specificities exist in mucin recognition by P. aeruginosa.

FIG. 1

Comparative binding of P. aeruginosa PAO1 and its fliD and fliC mutants to human airway mucins. PAO1-D, fliD mutant of PAO1; PAO1-D(375Db), PAO1-D complemented with the complete fliD gene on a multicopy plasmid vector, pPZ375Db; PAO1-D(375), PAO1-D with the vector pPZ375; PAO1-C, fliC mutant of PAO1. Differences in binding between strain PAO1 and its mutants marked by one asterisk were not significant, whereas those marked by two asterisks were considered significant (P < 0.05) by Student's t test. The binding of PAO1-D(375Db) and that of PAO1-D(375) were also significantly different.

FIG. 2

Comparative binding of P. aeruginosa PAO1 and its fliD and fliC mutants to the polyacrylamide derivative bearing the sialyl-Le^x glycotope. PAO1-D, fliD mutant of PAO1; PAO1-D(375 Db), PAO1-D complemented with the complete fliD gene on a multicopy plasmid vector, pPZ375Db; PAO1-D(375), PAO1-D with the vector pPZ375; PAO1-C, fliC mutant of PAO1. Differences in binding between strain PAO1 and its mutants marked by one asterisk were not significant, whereas those marked by two asterisks were considered significant (P < 0.05) by Student's t test. The binding of PAO1-D(375Db) and that of PAO1-D(375) were also significantly different.

FIG. 3

Comparative binding of P. aeruginosa PAO1 and its fliD and fliC mutants to the polyacrylate derivative bearing the Le^x glycotope. PAO1-D, fliD mutant of PAO1; PAO1-D(375 Db), PAO1-D complemented with the complete fliD gene on a multicopy plasmid vector, pPZ375Db; PAO1-C, fliC mutant of PAO1. Differences in binding between strain PAO1 and its mutants marked by one asterisk were not significant, whereas those marked by two asterisks were considered significant.