Enterohaemorrhagic Escherichia coli Tir requires a C-terminal 12-residue peptide to initiate EspF-mediated actin assembly and harbours N-terminal sequences that influence pedestal length.

Full Abstract

Enterohaemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC) both utilize type III secretion systems that translocate the effector protein Tir into the plasma membrane of mammalian cells in order to stimulate localized actin assembly into 'pedestals'. The Tir molecule that EPEC delivers is phosphorylated within its C-terminus on tyrosine-474, and a clustered 12-residue phosphopeptide encompassing this residue initiates an efficient signalling cascade that triggers actin polymerization. In addition to Y474, tyrosine-454 of EPEC Tir is phosphorylated, although inefficiently, and promotes actin polymerization at low levels. In contrast to EPEC Tir, EHEC Tir lacks Y474 and triggers pedestal formation in a phosphotyrosine-independent manner by interacting with an additional effector protein, EspF(U). To identify EHEC Tir sequences that regulate localized actin assembly, we circumvented the strict requirements for type III translocation and directly expressed Tir derivatives in mammalian cells by transfection. Infection of Tir-expressing cells with a Tir-deficient EHEC strain demonstrated that ectopically expressed Tir localizes to the plasma membrane, is modified by mammalian serine-threonine kinases and is fully functional for actin pedestal formation. Removal of portions of the cytoplasmic N-terminus of Tir resulted in the generation of abnormally long pedestals, indicating that this region of EHEC Tir influences pedestal length. In the presence of the entire N-terminal domain, a 12-residue peptide from the C-terminus of EHEC Tir is both necessary and sufficient to recruit EspF(U) and initiate actin pedestal formation. This peptide encompasses the portion of EHEC Tir analogous to the EPEC Tir-Y454 region and is present within the Tir molecules of all pedestal-forming bacteria, suggesting that this sequence harbours a conserved signalling function.

Learn Faster Today Improve your study skills

Author information

Author/s: Campellone, Kenneth G (KG); Brady, Michael J (MJ); Alamares, Judith G (JG); Rowe, Daniel C (DC); Skehan, Brian M (BM); Tipper, Donald J (DJ); Leong, John M (JM);

Affiliation: Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, 01655, USA.

Grants: NIH-R01-AI46454 (Agency:NIAID NIH HHS)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural

Journal: Cellular microbiology (Cell Microbiol), published in England. (Language: eng)

Reference: 2006-Sep; vol 8 (issue 9) : pp 1488-503

Dates: Created 2006/08/22; Completed 2006/10/03; Revised 2007/11/14;

PMID: 16922867, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

External Links for this article (including full text providers, if available):

Click Electronic Full-text Provider Links to see options for finding the electronic full text links to this article. Note there may be a subscription or fee required for access to the full text. See our FAQ for information on finding FREE full text articles.

This article may also be located in paper journal collections available in many libraries. Use the Journal and Publication Information above to find the full article.

MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Actins - metabolism
Amino Acid Sequence
Carrier Proteins - genetics; metabolism
Cell Membrane - metabolism
Escherichia coli O157 - genetics; growth & development; metabolism
Escherichia coli Proteins - chemistry; genetics; metabolism
Genetic Complementation Test
Hela Cells
Humans

Humans
Microfilaments - metabolism
Microscopy, Fluorescence - methods
Models, Genetic
Mutation - genetics
Peptide Fragments - chemistry; genetics; physiology
Phosphorylation
Receptors, Cell Surface - chemistry; genetics; metabolism
Sequence Homology, Amino Acid

Associated Chemicals: Actins (0) ; Carrier Proteins (0) ; Escherichia coli Proteins (0) ; EspFU protein, E coli (0) ; Peptide Fragments (0) ; Receptors, Cell Surface (0) ; Tir protein, E coli (0)

These are the highest related articles currently in the database:

See 100+ related articles.