Human brain endothelial ATP synthase β-subunit is mannose-insensitive binding target of FimH

Binding of meningitis-causing Escherichia coli K1 to human brain microvascular endothelial cells (HBMEC) contributes to traversal of the blood-brain barrier, which occurs in part by the mannose-sensitive binding of FimH. In this study, we showed that FimH also binds to HBMEC, independent of mannose, and identified ATP synthase β-subunit and actin proteins from the surface biotinylated HBMEC as the mannose-insensitive binding targets for FimH. Co-immunoprecipitation experiments in the presence of α-methyl mannose verified the binding of FimH to ATP synthase β-subunit of HBMEC. ATP synthase β-subunit antibody decreased E. coli K1 binding to HBMEC in the presence of α-methyl mannose. Taken together, these findings demonstrate that FimH of E. coli K1 binds to HBMEC in both mannose-sensitive and-insensitive manner.