The Dot/Icm type IV secretion system of Legionella pneumophila is essential for the induction of apoptosis in human macrophages

Steven D. Zink, Lisa Pedersen, Nicholas P. Cianciotto, Yousef Abu Kwaik*

*Corresponding author for this work

Research output: Contribution to journalArticle

88 Scopus citations

Abstract

We have previously shown that Legionella pneumophila induces caspase 3-dependent apoptosis in mammalian cells during early stages of infection. In this report, we show that nine L. pneumophila strains with mutations in the dotA, dotDCB, icmT, icmGCD, and icmJB loci are completely defective in the induction of apoptosis, in addition to their severe defects in intracellular replication and pore formation-mediated cytotoxicity. Importantly, all nine dot/icm mutants were complemented for all their defective phenotypes with the respective wild-type loci. We show that the role of the Dot/Icm type IV secretion system in the induction of apoptosis is independent of the RtxA toxin, the dot/icm-regulated pore-forming toxin, and the type II secretion system. However, the pore-forming toxin, which is triggered upon entry into the postexponential growth phase, enhances the ability of L. pneumophila to induce apoptosis. Our data provide the first example of the role of a type IV secretion system of a bacterial pathogen in the induction of apoptosis in the host cell.

Original languageEnglish (US)
Pages (from-to)1657-1663
Number of pages7
JournalInfection and immunity
Volume70
Issue number3
DOIs
StatePublished - 2002

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases

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