Signal transduction events involved in human epithelial cell invasion by Campylobacter jejuni 81-176

Analyses of invasive enteric bacteria (e.g. Shigella, Salmonella, Listeria, and Campylobacter) have shown that these pathogens initiate orchestrated signal transduction cascades in host cells leading to host cytoskeletal rearrangements that result in bacterial uptake. This current study was specifically aimed at examining the involvement of host membrane caveolae and certain protein kinases in epithelial cell invasion by C. jejuni strain 81-176, for which we have previously characterized the kinetics of entry and a unique microtubule-dependent mechanism of internalization. Utilizing in vitro cultured cell invasion assays with a gentamicin-kill step, disruption of membrane caveolae by pretreatment of INT407 cell monolayers with filipin III reduced C. jejuni 81-176 entry by >95%. Strain 81-176 uptake into INT407 cells was markedly inhibited by monolayer pretreatment with the protein kinase inhibitors genistein and staurosporine, or specific inhibitors of PI 3-kinase, wortmannin and LY294002. Western blot analysis using monoclonal anti-protein tyrosine phosphorylation antibody revealed distinctive changes during invasion in phosphorylation of at least nine proteins. Further inhibitor studies indicated that heterotrimeric G proteins, plus ERK and p38 MAP kinase activation are also involved in C. jejuni 81-176 invasion. These results suggest that C. jejuni 81-176 interact at host cell surface membrane caveolae with G protein-coupled receptors, which presumably trigger G-proteins and kinases to activate host proteins including PI 3-kinase and MAP kinases, that appear to be intimately involved in the events controlling 81-176 internalization.