Regulation of T oll‐like receptor 2 interaction with Ecgp96 controls E scherichia coli K 1 invasion of brain endothelial cells

Summary The interaction of outer membrane protein A ( OmpA ) with its receptor, Ecgp96 (a homologue of Hsp90β ), is critical for the pathogenesis of E scherichia coli   K 1 meningitis. Since Hsp90 chaperones T oll‐like receptors ( TLRs ), we examined the role of TLRs in E . coli   K 1 infection. Herein, we show that newborn TLR2 −/− mice are resistant to E . coli   K 1 meningitis, while TLR4 −/− mice succumb to infection sooner. In vitro , OmpA + E . coli infection selectively upregulates Ecgp96 and TLR2 in human brain microvascular endothelial cells ( HBMEC ), whereas OmpA − E . coli upregulates TLR4 in these cells. Furthermore, infection with OmpA + E . coli causes Ecgp96 and TLR2 translocate to the plasma membrane of HBMEC as a complex. Immunoprecipitation studies of the plasma membrane fractions from infected HBMEC reveal that the C termini of Ecgp96 and TLR2 are critical for OmpA + E . coli invasion. Knockdown of TLR2 using siRNA results in inefficient membrane translocation of Ecgp96 and significantly reduces invasion . In addition, the interaction of Ecgp96 and TLR2 induces a bipartite signal, one from Ecgp96 through PKC‐α while the other from TLR2 through MyD88 , ERK1/2 and NF‐κB . This bipartite signal ultimately culminates in the efficient production of NO , which in turn promotes E . coli   K 1 invasion of HBMEC .