Molecular dissection of Salmonella-induced membrane ruffling versus invasion

Cell Microbiol. 2010 Jan;12(1):84-98. doi: 10.1111/j.1462-5822.2009.01380.x. Epub 2009 Sep 2.

Abstract

Type III secretion system-mediated injection of a cocktail of bacterial proteins drives actin rearrangements, frequently adopting the shape of prominent protuberances of ruffling membrane, and culminating in host cell invasion of Gram-negative pathogens like Salmonella typhimurium. Different Salmonella effectors are able to bind actin and activate Rho-family GTPases, which have previously been implicated in mediating actin-dependent Salmonella entry by interacting with N-WASP or WAVE-complex, well-established activators of the actin nucleation machine Arp2/3-complex. Using genetic deletion and RNA interference studies, we show here that neither individual nor collective removal of these Arp2/3- complex activators affected host cell invasion as efficiently as Arp2/3-complex knock-down, although the latter was also not essential. However, interference with WAVE-complex function abrogated Salmonella-induced membrane ruffling without significantly affecting entry efficiency, actin or Arp2/3-complex accumulation. In addition, scanning electron microscopy images captured entry events in the absence of prominent membrane ruffles. Finally, localization and RNA interference studies indicated a relevant function in Salmonella entry for the novel Arp2/3-complex regulator WASH. These data establish for the first time that Salmonella invasion is separable from bacteria-induced membrane ruffling, and uncover an additional Arp2/3-complex activator as well as an Arp2/3-complex-independent actin assembly activity that contribute to Salmonella invasion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin-Related Protein 2-3 Complex
  • Bacterial Proteins / genetics
  • Bacterial Proteins / physiology*
  • Blotting, Western
  • Cell Line
  • Cell Membrane / metabolism*
  • Cell Membrane / microbiology
  • Cell Membrane / ultrastructure
  • Fibroblasts / metabolism
  • Fibroblasts / microbiology
  • Fibroblasts / ultrastructure
  • Humans
  • Microscopy, Electron, Scanning
  • Microscopy, Fluorescence
  • Proteins / genetics
  • Proteins / physiology
  • RNA Interference
  • Salmonella typhimurium / physiology*
  • Wiskott-Aldrich Syndrome Protein, Neuronal / metabolism
  • Wiskott-Aldrich Syndrome Protein, Neuronal / physiology
  • tRNA Methyltransferases

Substances

  • Actin-Related Protein 2-3 Complex
  • Bacterial Proteins
  • Proteins
  • WASL protein, human
  • Wiskott-Aldrich Syndrome Protein, Neuronal
  • TRMO protein, human
  • tRNA Methyltransferases