Maximal adherence and invasion of INT 407 cells by Campylobacter jejuni requires the CadF outermembrane protein and microfilament reorganization

The binding of Campylobacter jejuni to fibronectin (Fn), a component of the extracellular matrix, is mediated by a 37 kDa outer-membrane protein termed CadF for Campylobacter adhesion to fibronectin. The specificity of C.jejuni binding to Fn, via CadF, was demonstrated using antibodies reactive against Fn and CadF. More specifically, the anti-CadF antibody reduced the binding of two C. jejuni clinical isolates to immobilized Fn by greater than 50%. Furthermore, a C. jejuni wild-type isolate, in contrast to the isogenic CadF mutant, was found to compete with another C. jejuni wildtype isolate for host cell receptors. Given the relationship between the pericellular Fn matrix and the cytoskeleton, the involvement of host cell cytoskeletal components in C. jejuni internalization was also examined. Cytochalasin D and mycalolide B microfilament depolymerizing agents resulted in a significant reduction in C. jejuni invasion. Studies targeting paxillin, a focal adhesion signalling molecule, identified an increased level of tyrosine phosphorylation upon C. jejuni infection of INT 407 cells. Collectively, these data suggest CadF promotes the binding of C. jejuni to Fn, which in turn stimulates a signal transduction pathway involving paxillin.