title: Control of NOD2 and Rip2-dependent innate immune activation by GEF-H1.
abstract: BACKGROUND
  Genetic variants of nucleotide-binding oligomerization domain 2 (NOD2) lead to aberrant microbial recognition and can cause chronic inflammatory diseases in patients with Crohn's disease (CD).
  
  
  METHODS
  We utilized gene-specific siRNA mediated knockdown and expression of guanine nucleotide exchange factor H1 (GEF-H1) in wildtype, Rip2-, and Nod2-deficient macrophages, HCT-116 and HEK 293 cells to determine the role of GEF-H1 in NOD2 and Rip2-mediated NF-κB-dependent induction of proinflammatory cytokine expression. Confocal microscopy was used to determine subcellular distribution of GEF-H1, Rip2, and NOD2.
  
  
  RESULTS
  We identified GEF-H1 as an unexpected component of innate immune regulation during microbial pattern recognition by NOD2. Surprisingly, GEF-H1-mediated the activation of Rip2 during signaling by NOD2, but not in the presence of the 3020 insC variant of NOD2 associated with CD. GEF-H1 functioned downstream of NOD2 as part of Rip2-containing signaling complexes and was responsible for phosphorylation of Rip2 by Src tyrosine kinase. Rip2 variants lacking the tyrosine target of GEF-H1-mediated phosphorylation were unable to mediate NF-κB activation in Rip2-deficient macrophages and failed to transduce NOD2 signaling. GEF-H1 is required downstream of NOD2 as part of Rip2-containing signaling complexes for the activation of innate immune responses.
  
  
  CONCLUSIONS
  GEF-H1 connects tyrosine kinase function to NOD-like receptor signaling and is fundamental to the regulation of microbial recognition by ubiquitous innate immune mechanisms mediated by Rip2 kinase.
authors: Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
authors: Yun
authors: Y
authors: Zhao
authors: Carmen
authors: C
authors: Alonso
authors: Isabel
authors: I
authors: Ballester
authors: Joo Hye
authors: JH
authors: Song
authors: Sun Young
authors: SY
authors: Chang
authors: Bayasi
authors: B
authors: Guleng
authors: Seiji
authors: S
authors: Arihiro
authors: Peter J
authors: PJ
authors: Murray
authors: Ramnik
authors: R
authors: Xavier
authors: Koichi S
authors: KS
authors: Kobayashi
authors: Hans-Christian
authors: HC
authors: Reinecker
mesh_terms: D002478:Cells, Cultured; D003424:Crohn Disease / Q000276:immunology*; D016207:Cytokines / Q000096:biosynthesis / Q000276:immunology; D055785:Gene Knockdown Techniques; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000276:immunology*; D045325:HCT116 Cells; D057809:HEK293 Cells; D006801:Humans; D007113:Immunity, Innate; D007249:Inflammation / Q000276:immunology; D008264:Macrophages / Q000276:immunology; D016328:NF-kappa B / Q000378:metabolism; D053473:Nod2 Signaling Adaptor Protein / Q000276:immunology*; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2 / Q000276:immunology* / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: C577356:ARHGEF2 protein, human; D016207:Cytokines; D020662:Guanine Nucleotide Exchange Factors; D016328:NF-kappa B; C429018:NOD2 protein, human; D053473:Nod2 Signaling Adaptor Protein; D064067:Rho Guanine Nucleotide Exchange Factors; D019061:src-Family Kinases; C506253:RIPK2 protein, human; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2