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Modulation of Nod2-dependent NF-kappaB signaling by the actin cytoskeleton

Sylvie Legrand-Poels1, Gaelle Kustermans, Françoise Bex

  • 1Laboratory of Virology and Immunology, CBIG-GIGA, University of Liège, Liège, Belgium. S.Legrand@ulg.ac.be

Journal of Cell Science
|March 16, 2007
PubMed

Insights

Actin disruption activates the Nod2 protein, a key player in immune responses. This finding reveals how cellular structure changes influence immune signaling pathways, impacting pathogen defense.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • Actin cytoskeleton dynamics are crucial for cellular functions, including immune responses.
  • Nuclear Factor-kappaB (NF-kappaB) signaling is central to inflammation and immunity.
  • Nod2 (Nucleotide-binding oligomerization domain-containing protein 2) is an intracellular pattern recognition receptor involved in innate immunity.

Purpose of the Study:

  • To investigate the mechanism linking actin disruption to NF-kappaB activation.
  • To explore the role of the human Nod2 protein in this process.
  • To understand how Nod2 interacts with the actin cytoskeleton during immune signaling.

Main Methods:

  • Treatment of myelomonocytic and intestinal epithelial cells with actin-disrupting agents (Cytochalasin D, Latrunculin B).
  • Assessment of NF-kappaB activation and IKK (Inhibitor of kappaB kinase) activity.
  • Analysis of Nod2 protein localization and interaction with the actin cytoskeleton using cell fractionation, confocal microscopy, and co-immunoprecipitation.
  • Utilizing Rac1 dominant-negative constructs to study membrane ruffle involvement.

Main Results:

  • Actin disruption by Cytochalasin D significantly enhanced Nod2-mediated NF-kappaB signaling.
  • Nod2 translocated from the detergent-insoluble fraction to the soluble fraction upon actin disruption, indicating dependence on the actin cytoskeleton.
  • Nod2 colocalized with F-actin in membrane ruffles and associated with activated Rac1.
  • Disruption of membrane ruffles primed Nod2-dependent NF-kappaB signaling.

Conclusions:

  • Actin cytoskeleton dynamics regulate Nod2 localization and activity.
  • Nod2's association with Rac1 in dynamic cytoskeletal structures allows for rapid signal activation during infection.
  • This mechanism may serve to repress Nod2 signaling in unstimulated cells and facilitate rapid immune responses upon bacterial challenge.

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