Enteropathogenic E-coli Tir binds Nck to initiate actin pedestal formationin host cells

Enteropathogenic Escherichia coli (EPEC) is a bacterial pathogen that cause s infantile diarrhea worldwide(1). EPEC injects a bacterial protein, transl ocated intimin receptor (Tir), into the host-cell plasma membrane where it acts as a receptor for the bacterial outer membrane protein, intimin(2). Th e interaction of Tir and intimin triggers a marked rearrangement of the hos t actin cytoskeleton into pedestals beneath adherent bacteria. On delivery into host cells, EPEC Tir is phosphorylated on tyrosine 474 of the intracel lular carboxy-terminal domain, an event that is required for pedestal forma tion(3). Despite its essential role, the function of Tir tyrosine phosphory lation has not yet been elucidated. Here we show that tyrosine 474 of Tir d irectly binds the host-cell adaptor protein Nck, and that Nck is required f or the recruitment of both neural Wiskott-Aldrich-syndrome protein (N-WASP) and the actin-related protein (Arp)2/3 complex to the EPEC pedestal, direc tly linking Tir to the cytoskeleton. Cells with null alleles of both mammal ian Nick genes are resistant to the effects of EPEC on the actin cytoskelet on. These results implicate Nick adaptors as host-cell determinants of EPEC virulence.