Figure 11

Model for C. jejuni -induced signaling leading to Cdc42 activation and bacterial invasion. C. jejuni adheres to host cells via the fibronectin-binding protein CadF, which acts as a bridge engaging the integrin-β1 receptor. Integrin occupancy and clustering in lipid rafts leads to recruitment and activation of the non-receptor tyrosine kinase FAK. Phosphorylation of FAK and Src triggers a cascade of signals resulting in the formation of protein complexes leading to activation of other signaling factors as indicated. Assembly of integrin-dependent signal complexes leads to phosphorylation and transactivation of PDGFR and EGFR, followed by stimulation of PI3-K and Vav2. Activated Vav2 then induces the activation of Cdc42. This signaling potentially causes localized actin and/or microtubule rearrangements at the site of C. jejuni entry, resulting in bacterial uptake. In addition to CadF, the C. jejuni flagellum also appears to play a role in the described signal cascades. If the flagellum participates by sole bacterial motility, by translocating bacterial effector proteins or targeting a host receptor directly is not yet clear and needs to be investigated in future studies.