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Shigella IpaD has a dual role: signal transduction from the type III secretion system needle tip and intracellular secretion regulation

Research output: Contribution to journalArticle

  • A Dorothea Roehrich
  • Enora Guillossou
  • Ariel J Blocker
  • Isabel Martinez-Argudo
Original languageEnglish
Pages (from-to)690-706
JournalMolecular Microbiology
Volume87
Issue number3
Early online date11 Jan 2013
DOIs
DateE-pub ahead of print - 11 Jan 2013
DatePublished (current) - Feb 2013

Abstract

Type III secretion systems (T3SSs) are protein injection devices essential for the interaction of many Gram-negative bacteria with eukaryotic cells. While Shigella assembles its T3SS when the environmental conditions are appropriate for invasion, secretion is only activated after physical contact with a host cell. First, the translocators are secreted to form a pore in the host cell membrane, followed by effectors which manipulate the host cell. Secretion activation is tightly controlled by conserved T3SS components: the needle tip proteins IpaD and IpaB, the needle itself and the intracellular gatekeeper protein MxiC. To further characterize the role of IpaD during activation, we combined random mutagenesis with a genetic screen to identify ipaD mutant strains unable to respond to host cell contact. Class II mutants have an overall defect in secretion induction. They map to IpaD's C-terminal helix and likely affect activation signal generation or transmission. The Class I mutant secretes translocators prematurely and is specifically defective in IpaD secretion upon activation. A phenotypically equivalent mutant was found in mxiC. We show that IpaD and MxiC act in the same intracellular pathway. In summary, we demonstrate that IpaD has a dual role and acts at two distinct locations during secretion activation.

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© 2013 Blackwell Publishing Ltd.

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