EspFU Is a Translocated EHEC Effector that Interacts with Tir and N-WASP and Promotes Nck-Independent Actin Assembly

• DOI: 10.1016/j.devcel.2004.07.004
• Publication Date: 2004-08-10T15:56:00Z
• Authors: Kenneth G. Campel...; Douglas Robbins; John M. Leong
• Keywords: 570; Genomic Islands; Blotting, Western; Immunoblotting; 610; Nerve Tissue Proteins; Escherichia coli O157; 03 medical and health sciences; Escherichia coli; Humans; Phosphotyrosine; Adaptor Proteins, Signal Transducing; Cell Nucleus; Oncogene Proteins; 0303 health sciences; Escherichia coli Proteins; Genetic Complementation Test; Intracellular Signaling Peptides and Proteins; Actins; Microscopy, Fluorescence; Mutation; Carrier Proteins; Gene Deletion; Developmental Biology; HeLa Cells

Several microbial pathogens including enteropathogenic E. coli (EPEC) exploit mammalian tyrosine-kinase signaling cascades to recruit Nck adaptor proteins and activate N-WASP-Arp2/3-mediated actin assembly. To promote localized actin "pedestal formation," EPEC translocates the bacterial effector protein Tir into the plasma membrane, where it is tyrosine-phosphorylated and binds Nck. Enterohemorrhagic E. coli (EHEC) also generates Tir-dependent pedestals, but in the absence of phosphotyrosines and Nck recruitment. To identify additional EHEC effectors that stimulate phosphotyrosine-independent actin assembly, we systematically generated EHEC mutants containing specific deletions in putative pathogenicity-islands. Among 0.33 Mb of deleted sequences, only one ORF was critical for pedestal formation. It lies within prophage-U, and encodes a protein similar to the known effector EspF. This proline-rich protein, EspFU, is the only EHEC effector of actin assembly absent from EPEC. Whereas EHEC Tir cannot efficiently recruit N-WASP or trigger actin polymerization, EspFU associates with Tir, binds N-WASP, and potently stimulates Nck-independent actin assembly.