Co-ordinate regulation of distinct host cell signalling pathways by multifunctional enteropathogenic Escherichia coli effector molecules

Mol Microbiol. 2002 May;44(4):1095-1107. doi: 10.1046/j.1365-2958.2002.02952.x.

Abstract

Enteropathogenic Escherichia coli (EPEC) is a major cause of paediatric diarrhoea and a model for the family of attaching and effacing (A/E) pathogens. A/E pathogens encode a type III secretion system to transfer effector proteins into host cells. The EPEC Tir effector protein acts as a receptor for the bacterial surface protein intimin and is involved in the formation of Cdc42-independent, actin-rich pedestal structures beneath the adhered bacteria. In this paper, we demonstrate that EPEC binding to HeLa cells also induces Tir-independent, cytoskeletal rearrangement evidenced by the early, transient formation of filopodia-like structures at sites of infection. Filopodia formation is dependent on expression of the EPEC Map effector molecule - a protein that targets mitochondria and induces their dysfunction. We show that Map-induced filopodia formation is independent of mitochondrial targeting and is abolished by cellular expression of the Cdc42 inhibitory WASP-CRIB domain, demonstrating that Map has at least two distinct functions in host cells. The transient nature of the filopodia is related to an ability of EPEC to downregulate Map-induced cell signalling that, like pedestal formation, was dependent on both Tir and intimin proteins. The ability of Tir to downregulate filopodia was impaired by disrupting a putative GTPase-activating protein (GAP) motif, suggesting that Tir may possess such a function, with its interaction with intimin triggering this activity. Furthermore, we also found that Map-induced cell signalling inhibits pedestal formation, revealing that the cellular effects of Tir and Map must be co-ordinately regulated during infection. Possible implications of the multifunctional nature of EPEC effector molecules in pathogenesis are discussed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Adhesins, Bacterial / metabolism
  • Bacterial Adhesion
  • Carrier Proteins / metabolism
  • Cytoskeleton / metabolism
  • Cytoskeleton / microbiology
  • Diarrhea / metabolism
  • Diarrhea / microbiology
  • Down-Regulation
  • Epithelial Cells / metabolism
  • Epithelial Cells / microbiology
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Escherichia coli / pathogenicity*
  • Escherichia coli / ultrastructure
  • Escherichia coli Infections / metabolism
  • Escherichia coli Infections / microbiology
  • Escherichia coli Proteins*
  • HeLa Cells
  • Humans
  • Models, Biological
  • Protein Binding
  • Pseudopodia / physiology
  • Receptors, Cell Surface / metabolism
  • Signal Transduction*
  • cdc42 GTP-Binding Protein / metabolism

Substances

  • Actins
  • Adhesins, Bacterial
  • Carrier Proteins
  • Escherichia coli Proteins
  • Receptors, Cell Surface
  • Tir protein, E coli
  • eaeA protein, E coli
  • cdc42 GTP-Binding Protein