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(NAS Colloquium) Virulence and Defense in Host--Pathogen Interactions Common Features Between Plants and Animals (2001) / Chapter Skim
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Striking a Balance: Modulation of the Actin Cytoskeleton by Salmonella
Pages 3-10

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From page 3...
... Stimulation of Cdc42 and Rac leads to marked actin cytoskeleton rearrangements, which are further enhanced by SipA, a Salmonella protein also delivered into the host cell by the type 111 secretion system. SipA lowers the critical concentration of G-actin, stabilizes F-actin at the site of bacterial entry, and increases the bundling activity of the host-cell protein T-plastin (fimbrin)
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From page 4...
... The latter process depends on the function of a subset of type III secreted proteins that, although dispensable for protein secretion, are essential for the translocation of effecter proteins into the host cell. In Salmonella, those proteins are SipB, SipC, and SipD (9-12~.
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From page 5...
... . Rewing Up Rho GTPases: Signaling for Entry and Beyond Salmonella entry into host cells strictly depends on the function of the actin cytoskeleton as addition of drugs that interfere with actin dynamics effectively block bacterial internalization (22, 23~.
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From page 6...
... . Consistent with this activity, microinjection or transient expression of SopE in cultured cells leads to marked actin cytoskeleton rearrangements and membrane ruffling that resemble the changes induced by Salmonella infections (Fig.
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From page 7...
... It is therefore likely that the calcium fluxes stimulated by Salmonella are also the consequence of the activation of Cdc42 and Rac by SopE and SopB. Fine-Tuning the Actin Cytoskeleton Rearrangements: The Role of the Actin-Binding Protein SipA Microinjection or transient expression in host cells of the bacterial-encoded exchange factor SopE leads to actin cytoskeletal rearrangements and membrane ruffling.
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From page 8...
... It is possible that this activity may aid bacterial entry by contributing to the actin nucleation events that lead to membrane ruffling and bacterial uptake. However, SipC by itself is not sufficient to induce actin cytoskeleton rearrangements because an S
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From page 9...
... The existence of other putative effector proteins of unknown function that also are delivered into host cells by the centisome 63 type III secretion system indicates that we are just beginning to understand the complexities of this system. The interaction of Salmonella with host cells is therefore an eloquent example of the sophisticated nature of the mechanisms used by bacterial pathogens that have sustained longstanding associations with their hosts.
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Key Terms

  • actin cytoskeleton
  • iii secretion
  • host cells
  • cytoskeleton rearrangements
  • effector proteins

  • host cell
  • iii secreted
  • bacterial effector
  • transient expression
  • bacterial entry

  • bacterial internalization
  • secreted proteins
  • membrane ruffling
  • cellular responses
  • effector protein

  • membrane ruffles
  • bundling activity
  • exchange factor
  • protein sipa
  • morphological changes

  • secreted protein
  • cultured cells
  • bacterial envelope
  • cells leads
  • salmonella infection

  • electron micrographs
  • protein secretion
  • critical concentration
  • bacterial uptake
  • salmonella entry


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