The galactophilic lectin (PA-IL, gene LecA) from Pseudomonas aeruginosa. Its binding requirements and the localization of lectin receptors in various mouse tissues

The opportunistic pathogen Pseudomonas aeruginosa contains lectins of which one of them, PA-IL (gene lecA), shows preference for α-galactosylated glycans. The bacterial lectin is probably important in the carbohydrate-mediated adhesion of the microorganism to endothelia and epithelia and thereby the lectin facilitates entering and damaging of the cells. The requirements for the interaction between PA-IL and the carbohydrate epitopes to which the bacterial lectin may bind were here studied using α-galactosylated neoglycoproteins that were immobilized on Microtiter plates. It is concluded that the carbohydrate recognizing site of the lectin can have a binding requirement of only one saccharide. Lectin histochemistry was performed on sections from wild type mice and from knock-out mice, which lack function of the α1,3-galactosyltransferase gene. All assays with the P. aeruginosa lectin were compared with the results obtained using an isolectin from the legume shrub Griffonia simplicifolia: the GSI-B4 isolectin, which is highly specific for glycans terminating in Galα1-R. In the wild-type mice, lectin histochemistry showed a strong capillary reaction in heart, kidney and adrenal gland while none of the two lectins were able to detect capillaries in the pancreas. This could indicate a differential glycosylation with respect to endothelial cell Galα epitopes among different organs. Further, since no PA-IL binding to the endothelial cells in the KO mouse was observed, it seems that, in the mouse, the Pseudomonas lectin adheres to the Galα1-3Galβ1-4GlcNAc carbohydrate on endothelial cells in most organs and tissues. Finally, lectin staining of the basement membrane of the acini in the exocrine pancreas suggests the presence of Galα1-3Gal epitopes in WT mice basement membranes that are not detected by the P. aeruginosa lectin.