Actin pedestal formation by enterohemorrhagic Escherichia coli enhances bacterial host cell attachment and concomitant type III translocation Journal Article

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Authors: Battle, S. E.; Brady, M. J.; Vanaja, S. K.; Leong, J. M.; Hecht, G. A.
Article Title: Actin pedestal formation by enterohemorrhagic Escherichia coli enhances bacterial host cell attachment and concomitant type III translocation
Abstract: Attachment of enterohemorrhagic Escherichia coli (EHEC) to intestinal epithelial cells is critical for colonization and is associated with localized actin assembly beneath bound bacteria. The formation of these actin "pedestals" is dependent on the translocation of effectors into mammalian cells via a type III secretion system (T3SS). Tir, an effector required for pedestal formation, localizes in the host cell plasma membrane and promotes attachment of bacteria to mammalian cells by binding to the EHEC outer surface protein Intimin. Actin pedestal formation has been shown to foster intestinal colonization by EHEC in some animal models, but the mechanisms responsible for this remain undefined. Investigation of the role of Tir-mediated actin assembly promoting host cell binding is complicated by other, potentially redundant EHEC-encoded binding pathways, so we utilized cell binding assays that specifically detect binding mediated by Tir-Intimin interaction. We also assessed the role of Tir-mediated actin assembly in two-step assays that temporally segregated initial translocation of Tir from subsequent Tir-Intimin interaction, thereby permitting the distinction of effects on translocation from effects on cell attachment. In these experimental systems, we compromised Tir-mediated actin assembly by chemically inhibiting actin assembly or by infecting mammalian cells with EHEC mutants that translocate Tir but are specifically defective in Tir-mediated pedestal formation. We found that an inability of Tir to promote actin assembly resulted in a significant and striking decrease in bacterial binding mediated by Tir and Intimin. Bacterial mutants defective for pedestal formation translocated type III effectors to mammalian cells with reduced efficiency, but the decrease in translocation could be entirely accounted for by the decrease in host cell attachment.
Journal Title: Infection and immunity
Volume: 82
Issue: 9
ISSN: 1098-5522; 0019-9567
Publisher: American Society for Microbiology. All Rights Reserved  
Journal Place: United States
Date Published: 2014
Start Page: 3713
End Page: 3722
Language: eng
DOI/URL:

10.1128/IAI.01523-13
Notes: LR: 20150303; CI: Copyright (c) 2014; GR: I01 BX000785/BX/BLRD VA/United States; GR: P01 DK067887/DK/NIDDK NIH HHS/United States; GR: R01 AI46454/AI/NIAID NIH HHS/United States; GR: R01 DK050694/DK/NIDDK NIH HHS/United States; GR: R01 DK050694/DK/NIDDK NIH HHS/United States; GR: R01 DK058964/DK/NIDDK NIH HHS/United States; GR: R01 DK058964/DK/NIDDK NIH HHS/United States; GR: R01 DK097043/DK/NIDDK NIH HHS/United States; GR: R56 DK050694/DK/NIDDK NIH HHS/United States; GR: U54 AI057159/AI/NIAID NIH HHS/United States; JID: 0246127; 0 (Actins); 0 (Adhesins, Bacterial); 0 (Carrier Proteins); 0 (Escherichia coli Proteins); 0 (EspFU protein, E coli); 147094-99-3 (eaeA protein, E coli); OID: NLM: PMC4187837; 2014/06/23 [aheadofprint]; ppublish