Control of NOD2 and Rip2-dependent innate immune activation by GEF-H1

Center for the Study of Inflammatory Bowel Disease, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
Inflammatory Bowel Diseases (Impact Factor: 4.46). 04/2012; 18(4):603-12. DOI: 10.1002/ibd.21851
Source: PubMed


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).
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.
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.
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.

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Available from: Joo-Hye Song,
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    • "In addition to RIP2, multiple proteins were shown to interact with NOD2 and regulate its downstream signaling events. Some of these proteins include phosphatase 2A [9], ATG16L1 [10], ERBIN (a member of the leucine-rich repeat- and PDZ domain-containing family) [11], [12], guanine nucleotide exchange factor H1 [13], caspase-12 [14], CARD8 [15], A20 [16], TRIM27 [17], TRAF4 [18], GRIM-19 (a protein with homology to the NADPH dehydrogenase complex)[19], IPAF/CLAN/NLRC4 [20], and NALP1 [21]. The multimeric complexes of NOD2 are expected to function as a signaling platform referred to as the “NODosome”, homologous to other NOD-like receptor complexes, such as the “inflammasome” [22] and the “apoptosome” [23]. "
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