Enterohaemorrhagic and enteropathogenic Escherichia coli Tir proteins trigger a common Nck-independent actin assembly pathway

Cell Microbiol. 2007 Sep;9(9):2242-53. doi: 10.1111/j.1462-5822.2007.00954.x. Epub 2007 May 23.


The Tir proteins of enterohaemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC respectively) are each translocated into the host plasma membrane where they promote F-actin pedestals in epithelial cells beneath adherent bacteria, but the two proteins act by different means. The canonical EPEC Tir becomes phosphorylated on tyrosine residue 474 (Y474) to recruit the host adaptor protein Nck, and also stimulates an inefficient, Nck-independent pathway utilizing tyrosine residue 454 (Y454). In contrast, the canonical EHEC Tir lacks Y474 and instead utilizes residues 452-463 to recruit EspF(U), an EHEC-specific effector that stimulates robust Nck-independent actin assembly. EHEC Tir Y458 and EPEC Tir Y454 are both part of an asparagine-proline-tyrosine (NPY) sequence. We report that each of the EHEC Tir NPY residues is required for EspF(U) recruitment and pedestal formation, and each of the EPEC Tir NPY residues is critical for inefficient, Nck-independent pedestal formation. Introduction of EspF(U) into EPEC dramatically enhanced Nck-independent actin assembly by EPEC Tir in a manner dependent on NPY(454). These results suggest that EPEC and EHEC Tir trigger a common Nck-independent actin assembly pathway and are both derived from an ancestral Tir molecule that utilized NPY to stimulate low-level pedestal formation.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Actins / metabolism*
  • Adaptor Proteins, Signal Transducing
  • Amino Acid Sequence
  • Animals
  • Carrier Proteins / metabolism
  • Enterohemorrhagic Escherichia coli / cytology
  • Enterohemorrhagic Escherichia coli / metabolism*
  • Enteropathogenic Escherichia coli / cytology
  • Enteropathogenic Escherichia coli / metabolism*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • HeLa Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Molecular Sequence Data
  • Oncogene Proteins / metabolism*
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism*


  • Actins
  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • Escherichia coli Proteins
  • EspFU protein, E coli
  • Intracellular Signaling Peptides and Proteins
  • Nck protein
  • Oncogene Proteins
  • Receptors, Cell Surface
  • Tir protein, E coli