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Infection and Immunity, May 1999, p. 2389-2398, Vol. 67, No. 5
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Enterohemorrhagic Escherichia coli O157:H7 Produces Tir, Which Is Translocated to the Host Cell Membrane but Is Not Tyrosine Phosphorylated

Rebekah DeVinney, Markus Stein,dagger Dieter Reinscheid,Dagger Akio Abe, Sharon Ruschkowski, and B. Brett Finlay*

Biotechnology Laboratory, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada

Received 2 December 1998/Returned for modification 26 January 1999/Accepted 16 February 1999

Intimate attachment to the host cell leading to the formation of attaching and effacing (A/E) lesions is an essential feature of enterohemorrhagic Escherichia coli (EHEC) O157:H7 pathogenesis. In a related pathogen, enteropathogenic E. coli (EPEC), this activity is dependent upon translocation of the intimin receptor, Tir, which becomes tyrosine phosphorylated within the host cell membrane. In contrast, the accumulation of tyrosine-phosphorylated proteins beneath adherent EHEC bacteria does not occur, leading to questions about whether EHEC uses a Tir-based mechanism for adherence and A/E lesion formation. In this report, we demonstrate that EHEC produces a functional Tir that is inserted into host cell membranes, where it serves as an intimin receptor. However, unlike in EPEC, in EHEC Tir is not tyrosine phosphorylated yet plays a key role in both bacterial adherence to epithelial cells and pedestal formation. EHEC, but not EPEC, was unable to synthesize Tir in Luria-Bertani medium but was able to secrete Tir into M9 medium, suggesting that Tir synthesis and secretion may be regulated differently in these two pathogens. EHEC Tir and EPEC Tir both bind intimin and focus cytoskeletal rearrangements, indicating that tyrosine phosphorylation is not needed for pedestal formation. EHEC and EPEC intimins are functionally interchangeable, but EHEC Tir shows a much greater affinity for EHEC intimin than for EPEC intimin. These findings highlight some of the differences and similarities between EHEC and EPEC virulence mechanisms, which can be exploited to further define the molecular basis of pedestal formation.

* Corresponding author. Mailing address: Biotechnology Laboratory, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada. Phone: (604) 822-2210. Fax: (604) 822-9830. E-mail: bfinlay{at}unixg.ubc.ca.

dagger Present address: Via Fiorentina 11, 53000 Siena, Italy.

Dagger Present address: Abteilung Angewandte Mikrobiologie und Mykologie, Universitaet Ulm, D-89069 Ulm, Germany.

Infection and Immunity, May 1999, p. 2389-2398, Vol. 67, No. 5
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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