Abstract
PKCepsilon has been shown to play a key role in the effect of the Gram-negative bacterial product LPS; however, the target for PKCepsilon in LPS signaling is unknown. LPS signaling is mediated by Toll-like receptor 4, which uses four adapter proteins, MyD88, MyD88 adapter-like (Mal), Toll/IL-1R domain-containing adapter inducing IFN-beta (Trif), and Trif-related adapter molecule (TRAM). Here we show that TRAM is transiently phosphorylated by PKCepsilon on serine-16 in an LPS-dependent manner. Activation of IFN regulatory factor 3 and induction of the chemokine RANTES, which are both TRAM-dependent, were attenuated in PKCepsilon-deficient cells. TRAMS16A is inactive when overexpressed and is attenuated in its ability to reconstitute signaling in TRAM-deficient cells. We have therefore uncovered a key process in Toll-like receptor 4 signaling, identifying TRAM as the target for PKCepsilon.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing / genetics
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Adaptor Proteins, Signal Transducing / metabolism*
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Adaptor Proteins, Vesicular Transport / metabolism
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Animals
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Cell Membrane / metabolism
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Cells, Cultured
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Fibroblasts / cytology
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Fibroblasts / physiology
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Humans
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Isoenzymes / genetics
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Isoenzymes / metabolism*
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Lipopolysaccharides / metabolism
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Mice
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Mice, Knockout
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Phosphorylation
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Protein Kinase C-epsilon / genetics
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Protein Kinase C-epsilon / metabolism*
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Receptors, Interleukin / genetics
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Receptors, Interleukin / metabolism*
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Signal Transduction / physiology*
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Toll-Like Receptor 4 / genetics
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Toll-Like Receptor 4 / metabolism*
Substances
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Adaptor Proteins, Signal Transducing
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Adaptor Proteins, Vesicular Transport
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Isoenzymes
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Lipopolysaccharides
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Receptors, Interleukin
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Recombinant Fusion Proteins
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TICAM-1 protein, mouse
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Ticam2 protein, mouse
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Tlr4 protein, mouse
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Toll-Like Receptor 4
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Protein Kinase C-epsilon