1. Prostaglandin E receptor type 4-associated protein interacts directly with NF-kappaB1 and attenuates macrophage activation.
- Author
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Minami M, Shimizu K, Okamoto Y, Folco E, Ilasaca ML, Feinberg MW, Aikawa M, and Libby P
- Subjects
- Amino Acid Motifs physiology, Animals, Atherosclerosis genetics, Atherosclerosis metabolism, Cell Cycle Proteins genetics, Cell Line, Chemokines biosynthesis, Chemokines genetics, Dinoprostone genetics, Dinoprostone metabolism, Gene Silencing, Humans, Lipopolysaccharides pharmacology, MAP Kinase Kinase 1 genetics, MAP Kinase Kinase 1 metabolism, MAP Kinase Kinase 2 genetics, MAP Kinase Kinase 2 metabolism, Mice, Mice, Knockout, NF-kappa B p50 Subunit genetics, Phosphorylation drug effects, Protein Binding genetics, Receptors, Prostaglandin E genetics, Receptors, Prostaglandin E, EP4 Subtype, Signal Transduction drug effects, Signal Transduction genetics, Bone Marrow Cells metabolism, Cell Cycle Proteins metabolism, Macrophage Activation drug effects, Macrophage Activation genetics, Macrophages metabolism, NF-kappa B p50 Subunit metabolism, Receptors, Prostaglandin E metabolism
- Abstract
Macrophage activation participates pivotally in the pathophysiology of chronic inflammatory diseases, including atherosclerosis. Through the receptor EP4, prostaglandin E(2) (PGE(2)) exerts an anti-inflammatory action in macrophages, suppressing stimulus-induced expression of certain proinflammatory genes, including chemokines. We recently identified a novel EP4 receptor-associated protein (EPRAP), whose function in PGE(2)-mediated anti-inflammation remains undefined. Here we demonstrate that PGE(2) pretreatment selectively inhibits lipopolysaccharide (LPS)-induced nuclear factor kappaB1 (NF-kappaB1) p105 phosphorylation and degradation in mouse bone marrow-derived macrophages through EP4-dependent mechanisms. Similarly, directed EPRAP expression in RAW264.7 cells suppresses LPS-induced p105 phosphorylation and degradation, and subsequent activation of mitogen-activated protein kinase kinase 1/2. Forced expression of EPRAP also inhibits NF-kappaB activation induced by various proinflammatory stimuli in a concentration-dependent manner. In co-transfected cells, EPRAP, which contains multiple ankyrin repeat motifs, directly interacts with NF-kappaB1 p105/p50 and forms a complex with EP4. In EP4-overexpressing cells, PGE(2) enhances the protective action of EPRAP against stimulus-induced p105 phosphorylation, whereas EPRAP silencing in RAW264.7 cells impairs the inhibitory effect of PGE(2)-EP4 signaling on LPS-induced p105 phosphorylation. Additionally, EPRAP knockdown as well as deficiency of NF-kappaB1 in macrophages attenuates the inhibitory effect of PGE(2) on LPS-induced MIP-1beta production. Thus, PGE(2)-EP4 signaling augments NF-kappaB1 p105 protein stability through EPRAP after proinflammatory stimulation, limiting macrophage activation.
- Published
- 2008
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