title: The phosphatidylinositol 3-kinase/Akt pathway negatively regulates Nod2-mediated NF-kappaB pathway.
abstract: Nucleotide-binding oligomerization domain containing proteins (Nods) are intracellular pattern recognition receptors (PRRs) that recognize conserved moieties of bacterial peptidoglycan and activate downstream signaling pathways, including NF-kappaB pathway. Here, we show that Nod2 agonist muramyldipeptide (MDP) induces Akt phosphorylation in time and dose-dependent manner. The pharmacological inhibitor of phosphatidylinositol 3-kinase (PI3K) (wortmannin) and dominant-negative forms of p85 (the regulatory subunit of PI3K) or Akt enhance, while constitutive active forms of p110 (the catalytic subunit of PI3K) or Akt inhibit, NF-kappaB activation and the target gene interleukin (IL)-8 induced by MDP. In addition, the pharmacological inhibitors of PI3K (wortmannin and LY294002) enhance phosphorylation of NF-kappaB p65 on Ser529 and Ser536 residues, which result in enhanced p65 transactivation activity. Furthermore, we show that the inhibition of PI3K by the pharmacological inhibitors prevent the inactivation of glycogen synthase kinase (GSK)-3beta, suggesting that the negative regulation of PI3K/Akt on MDP-induced NF-kappaB activation is at least in part mediated through inactivation of GSK-3beta. Taken together, our results demonstrate that PI3K/Akt pathway is activated by Nod2 agonist MDP and negatively regulates NF-kappaB pathway downstream of Nod2 activation. Our results suggest that PI3K/Akt pathway may involve in the resolution of inflammatory responses induced by Nod2 activation.
authors.affiliation: The Western Human Nutrition Research Center, The Agricultural Research Service, United States Department of Agriculture, and Department of Nutrition, University of California, 430 West Health Science Drive, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhao
authors.forename: Joo Y
authors.initials: JY
authors.lastname: Lee
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Hwang
mesh_terms: D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D053473:Nod2 Signaling Adaptor Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D016328:NF-kappa B; D053473:Nod2 Signaling Adaptor Protein; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; C429018:NOD2 protein, human