Vimentin and PSF Act in Concert to Regulate IbeA plus E-coli K1 Induced Activation and Nuclear Translocation of NF-κB in Human Brain Endothelial Cells

Background: IbeA-induced NF-kappa B signaling through its primary receptor vimentin as well as its co-receptor PSF is required for meningitic E. coli K1 penetration and leukocyte transmigration across the blood-brain barrier (BBB), which are the hallmarks of bacterial meningitis. However, it is unknown how vimentin and PSF cooperatively contribute to IbeA-induced cytoplasmic activation and nuclear translocation of NF-kappa B, which are required for bacteria-mediated pathogenicities. Methodology/Principal Findings: IbeA-induced E. coli K1 invasion, polymorphonuclear leukocyte (PMN) transmigration and IKK/NF-kappa B activation are blocked by Caffeic acid phenethyl ester (CAPE), an inhibitor of NF-kappa B. IKK alpha/beta phosphorylation is blocked by ERK inhibitors. Co-immunoprecipitation analysis shows that vimentin forms a complex with I kappa B, NF-kappa B and tubulins in the resting cells. A dissociation of this complex and a simultaneous association of PSF with NF-kappa B could be induced by IbeA in a time-dependent manner. The head domain of vimentin is required for the complex formation. Two cytoskeletal components, vimentin filaments and microtubules, contribute to the regulation of NF-kappa B. SiRNA-mediated knockdown studies demonstrate that IKK alpha/beta phosphorylation is completely abolished in HBMECs lacking vimentin and PSF. Phosphorylation of ERK and nuclear translocation of NF-kappa B are entirely dependent on PSF. These findings suggest that vimentin and PSF cooperatively contribute to IbeA-induced cytoplasmic activation and nuclear translocation of NF-kappa B activation. PSF is essential for translocation of NF-kappa B and ERK to the nucleus. Conclusion/Significance: These findings reveal previously unappreciated facets of the IbeA-binding proteins. Cooperative contributions of vimentin and PSF to IbeA-induced cytoplasmic activation and nuclear translocation of NF-kappa B may represent a new paradigm in pathogen-induced signal transduction and lead to the development of novel strategies for the prevention and treatment of bacterial meningitis.