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A more recent version of this article appeared on January 1, 2009
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Submitted on May 23, 2008
Revised on October 17, 2008
Accepted on October 23, 2008

*Department of Cell and Animal Biology,
Confocal Unit, Institute of Life Sciences, The Hebrew University of Jerusalem, Givat Ram, Jerusalem 91904, Israel;
School of Engineering, Bar Ilan University, Ramat Gan 52900, Israel;
Section on Molecular Signal Transduction, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892; ||Program in Cell Biology, Hospital for Sick Children, Toronto, M5G 1X8, Canada; ¶Department of Medical Microbiology, Otto von Guericke University, D-39120 Magdeburg, Germany; #Department of Molecular Genetics and Biotechnology, The Hebrew University Faculty of Medicine, Jerusalem, 91120, Israel
Monitoring Editor: Asma Nusrat
Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] are phosphoinositides (PIs) present in small amounts in the inner leaflet of the plasma membrane (PM) lipid bilayer of host target cells. They are thought to modulate the activity of proteins involved in enteropathogenic Escherichia coli (EPEC) infection. However, the role of PI(4,5)P2 and PI(3,4,5)P3 in EPEC pathogenesis remains obscure. Here we show that EPEC induces a transient PI(4,5)P2 accumulation at bacterial infection sites. Simultaneous actin accumulation, likely involved in the construction of the actin-rich pedestal, is also observed at these sites. Acute PI(4,5)P2 depletion partially diminishes EPEC adherence to the cell surface and actin pedestal formation. These findings are consistent with a bimodal role, whereby PI(4,5)P2 contributes to EPEC association with the cell surface and to the maximal induction of actin pedestals. Finally, we show that EPEC induces PI(3,4,5)P3 clustering at bacterial infection sites, in a translocated intimin receptor (Tir)-dependent manner. Tir phosphorylated on tyrosine 454, but not on tyrosine 474, forms complexes with an active phosphatidylinositol 3-kinase (PI3K), suggesting that PI3K recruited by Tir prompts the production of PI(3,4,5)P3 beneath EPEC attachment sites. The functional significance of this event may be related to the ability of EPEC to modulate cell death, and innate immunity.
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