Beta-PIX and Rac1 GTPase mediate trafficking and negative regulation of NOD2

J Immunol. 2008 Aug 15;181(4):2664-71. doi: 10.4049/jimmunol.181.4.2664.


The nucleotide-binding domain and leucine-rich repeat containing protein NOD2 serves as a cytoplasmic pattern recognition molecule sensing bacterial muramyl dipeptide (MDP), whereas TLR2 mediates cell surface recognition of bacterial lipopeptides. In this study, we show that NOD2 stimulation activated Rac1 in human THP-1 cells and primary human monocytes. Rac1 inhibition or knock-down, or actin cytoskeleton disruption increased MDP-stimulated IL-8 secretion and NF-kappaB activation, whereas TLR2-dependent cell activation was suppressed by Rac1 inhibition. p21-activated kinase [Pak]-interacting exchange factor (beta-PIX) plays a role in this negative regulation, because knock-down of beta-PIX also led to increased NOD2-mediated but not TLR2-mediated IL-8 secretion, and coimmunoprecipitation experiments demonstrated that NOD2 interacted with beta-PIX as well as Rac1 upon MDP stimulation. Moreover, knock-down of beta-PIX or Rac1 abrogated membrane recruitment of NOD2, and interaction of NOD2 with its negative regulator Erbin. Overall, our data indicate that beta-PIX and Rac1 mediate trafficking and negative regulation of NOD2-dependent signaling which is different from Rac1's positive regulatory role in TLR2 signaling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Cells, Cultured
  • Down-Regulation* / immunology
  • Enzyme Activation / immunology
  • Guanine Nucleotide Exchange Factors / deficiency
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / physiology*
  • Humans
  • Nod2 Signaling Adaptor Protein / agonists
  • Nod2 Signaling Adaptor Protein / antagonists & inhibitors*
  • Nod2 Signaling Adaptor Protein / metabolism*
  • Nod2 Signaling Adaptor Protein / physiology
  • Protein Transport / immunology
  • Rho Guanine Nucleotide Exchange Factors
  • Signal Transduction / immunology
  • rac1 GTP-Binding Protein / deficiency
  • rac1 GTP-Binding Protein / genetics
  • rac1 GTP-Binding Protein / physiology*


  • ARHGEF7 protein, human
  • Guanine Nucleotide Exchange Factors
  • NOD2 protein, human
  • Nod2 Signaling Adaptor Protein
  • Rho Guanine Nucleotide Exchange Factors
  • rac1 GTP-Binding Protein