Fig 6.

Diagrammatic representation of STAT3 regulation of Rac1 in E. coli K1 invasion of HBMEC. Whereas earlier studies showed that FimH and CNF1 activate RhoA for E. coli internalization of HBMEC (12, 13), we hypothesize, based on the information obtained in the present study, that OmpA and IbeA trigger the phosphorylation of STAT3, which aids in converting GDP-Rac1 to GTP-Rac1 (through an as-yet-unknown mechanism involving the GEF, Vav2). Inhibitors or downregulators of either STAT3 or Rac1 decrease E. coli invasion of HBMEC. This study shows for the first time a molecular mechanism of E. coli regulation of Rac1 activation via STAT3 for E. coli internalization into HBMEC.