Differential recognition of members of the carcinoembryonic antigen family by Afa/Dr adhesins of diffusely adhering Escherichia coli (Afa/Dr DAEC)

Abstract

Little is known about the molecular bases underlying the virulence of diffusely adhering Escherichia coli (DAEC) harbouring the Afa/Dr family of adhesins. These adhesins recognize as receptors the GPI-anchored proteins CD55 (decay-accelerating factor, DAF) and CD66e (carcinoembryonic antigen, CEA). CD66e is a member of the CEA-related cell adhesion molecules (CEACAM) family, comprising seven members. We analysed the interactions of Afa/Dr DAEC with the CEACAMs using CEACAM-expressing CHO and HeLa cells. The results demonstrate that only E. coli expressing a subfamily of Afa/Dr adhesins, named here Afa/Dr-I, including Or, F1845 and AfaE-III adhesins, bound onto CHO cells expressing CEACAMI, CEA or CEACAM6. Whereas all the Afa/Dr adhesins elicit recruitment of CD55 around adhering bacteria, only the Afa/Dr-1 subfamily elicits the recruitment of CEACAM1, CEA and CEACAM6. In addition, although CEACAM3 is not recognized as a receptor by the subfamily of Afa/Dr adhesins, if is recruited around bacteria in HeLa cells. The recruited CEACAM1, CEA and CEACAMS around adhering bacteria resist totally or in part a detergent extraction, whereas the recruited CEACAM3 does not. Finally, the results show that recognition of CEA and CEACAMS, but not CEACAM1, is accompanied by tight attachment to bacteria of cell surface microvilli-like extensions, which are elongated. Moreover, recognition of CEA is accompanied by an activation of the Rho GTPase Cdc42 and by a phosphorylafion of ERM, which in turn elicit the observed cell surface microvilli-like extensions.