Date of this Version
The Journal of Biological Chemistry (2002), 277(4), p. 2876-2885. DOI: 10.1074/jbc.M110230200
Intimin-γ is an outer membrane protein of enterohemorrhagic Escherichia coli (EHEC) O157:H7 that is required for the organism to adhere tightly to HEp-2 cells and to colonize experimental animals. Another EHEC O157:H7 protein, the Transferred intimin receptor (Tir), is considered the primary receptor for intimin-γ. Nevertheless, Tir-independent binding of intimin-γ to HEp-2 cells has been reported. This observation suggests the existence of a eukaryotic receptor(s) for intimin-γ. In this study, we sought to identify that receptor(s). First, we determined by equilibrium binding titration that the association of purified intimin-γ with HEp-2 cells was specific and consistent with a single host cell receptor. Second, we isolated a protein from lysates of HEp-2 cells that bound intimin-γ and subsequently identified this molecule as nucleolin, a protein involved in cell growth regulation that can be cell surface-expressed. Third, we established that purified intimin-γ and nucleolin were co-localized on the surface of HEp-2 cells and that the site of EHEC O157:H7 attachment was associated with regions of nucleolin expression. Finally, we demonstrated that mouse anti-nucleolin sera significantly decreased the adherence of EHEC O157:H7 to HEp-2 cells. From this, we conclude that nucleolin is the HEp-2 cell receptor for intimin-γ expressed by EHEC O157:H7.