Role of alphavbeta5 integrins and vitronectin in Pseudomonas aeruginosa PAK interaction with A549 respiratory cells

Bacterial adherence to mammalian cells and their internalization are thought to participate in Pseudomonas aeruginosa pathogenicity. In this study, we explored the role of alpha5beta1 and alphavbeta5 integrins and their natural ligands, fibronectin (Fn) and vitronectin (Vn), in P. aeruginosa interaction with epithelial cells by using the PAK reference bacterial strain, A549 respiratory, and SKOV-3 human ovarian cell lines. The host cell cytoskeleton and cellular tyrosine kinases seem to be solicited during the PAK-respiratory cell interaction: cytochalasin D and genistein decreased the bacterial adherence and internalization. Blocking antibodies to alphavbeta5 integrins were the only antibodies tested to have inhibitory activity against PAK adherence to A549 cells. PAK internalization by A549 and SKOV-3 cells was markedly decreased in the presence of blocking antibodies to Vn and alphavbeta5 integrins. Addition of Vn in excess restored PAK invasion of both A549 and SKOV-3 cells in the presence of anti-Vn antibodies. Immunofluorescence experiments revealed that, in the presence of bacteria, the Vn fibrillar network disappeared, and alphavbeta5 staining was concentrated in sites where adherent bacteria were present. Taken together, these findings suggest that alphavbeta5 integrins, and their natural ligand Vn, are involved in PAK entry into human epithelial cells.