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Mutational analysis identifies residues crucial for homodimerization of myeloid differentiation factor 88 (MyD88) and for its function in immune cells.

ABSTRACT: Myeloid differentiation factor 88 (MyD88) is an adaptor protein that transduces intracellular signaling pathways evoked by the Toll-like receptors (TLRs) and interleukin-1 receptors (IL-1Rs). MyD88 is composed of an N-terminal death domain (DD) and a C-terminal Toll/IL-1 receptor (TIR) domain, separated by a short region. Upon ligand binding, TLR/IL-1Rs hetero- or homodimerize and recruit MyD88 through their respective TIR domains. Then, MyD88 oligomerizes via its DD and TIR domain and interacts with the interleukin-1 receptor-associated kinases (IRAKs) to form the Myddosome complex. We performed site-directed mutagenesis of conserved residues that are located in exposed regions of the MyD88-TIR domain and analyzed the effect of the mutations on MyD88 signaling. Our studies revealed that mutation of Glu(183), Ser(244), and Arg(288) impaired homodimerization of the MyD88-TIR domain, recruitment of IRAKs, and activation of NF-?B. Moreover, overexpression of two green fluorescent protein (GFP)-tagged MyD88 mini-proteins (GFP-MyD88151-189 and GFP-MyD88168-189), comprising the Glu(183) residue, recapitulated these effects. Importantly, expression of these dominant negative MyD88 mini-proteins competed with the function of endogenous MyD88 and interfered with TLR2/4-mediated responses in a human monocytic cell line (THP-1) and in human primary monocyte-derived dendritic cells. Thus, our studies identify novel residues of the TIR domain that are crucially involved in MyD88 homodimerization and TLR signaling in immune cells.

SUBMITTER: Loiarro M

PROVIDER: S-EPMC3798488 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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Mutational analysis identifies residues crucial for homodimerization of myeloid differentiation factor 88 (MyD88) and for its function in immune cells.

Loiarro Maria M Volpe Elisabetta E Ruggiero Vito V Gallo Grazia G Furlan Roberto R Maiorino Chiara C Battistini Luca L Sette Claudio C

The Journal of biological chemistry 20130909 42

Myeloid differentiation factor 88 (MyD88) is an adaptor protein that transduces intracellular signaling pathways evoked by the Toll-like receptors (TLRs) and interleukin-1 receptors (IL-1Rs). MyD88 is composed of an N-terminal death domain (DD) and a C-terminal Toll/IL-1 receptor (TIR) domain, separated by a short region. Upon ligand binding, TLR/IL-1Rs hetero- or homodimerize and recruit MyD88 through their respective TIR domains. Then, MyD88 oligomerizes via its DD and TIR domain and interacts ...[more]

PMID: 24019529

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Project description:BackgroundClostridium butyricum (C. butyricum, CB) is a probiotic to modulate the intestinal disorders and CB supplement has been found to have a great impact on inflammation and cancer treatment. However, the effects and mechanisms of CB on colorectal cancer (CRC) are not clear. We performed this study to investigate the influence of CB on the progression of CRC and the potential mechanisms in vivo and in vitro.MethodsWe established azoxymethane (AOM)/dextran sulfate sodium salt (DSS) model mice (male, 6-week-old C57BL/6J) and divided them into the control (Ctrl) and CB groups at the end of the second DSS cycle. Mice in the CB group received treatment with CB [1×108 colony forming unit (CFU) in 100 µL phosphate buffered saline (PBS)] 3 times a week for 40 days by gavage administration. The apoptotic cells in tumor tissues were assessed by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining. IL-6 and IL-10 were detected using enzyme linked immunosorbent assay (ELISA) assayes. Microbiota was analyzed through 16S rDNA sequencing. The location of CB was detected by the fluorescence in situ hybridization (FISH) assay. The function of CB on the proliferation of cell lines, HT-29 and CT-26, was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assayes. The expression of myeloid differentiation factor 88 (MyD88) and nuclear factor-kappa B (NF-κB) in cells and tissues was evaluated by real time quantitative PCR (RT-qPCR) and western blot.ResultsMice in the CB group showed a lower incidence and total volume of CRC, more apoptotic cells in the tumor tissue, a lower level of IL-6, and a higher level of IL-10 compared with those in the Ctrl group. CB altered the composition of the gut microbiota and was enriched in the small intestine and tumor tissue. Moreover, CB restrained the proliferation and the expression of MyD88 and NF-κB in CRC cell lines and colon tissue.ConclusionsCB restrained the progression of CRC, improved the inflammation of AOM/DSS mice, altered the composition of their gut microbiota, and regulated the expression of MyD88 and NF-κB. We concluded that CB plays its role in CRC via MyD88 and the NF-κB signaling pathway.

Dataset Information

Mutational analysis identifies residues crucial for homodimerization of myeloid differentiation factor 88 (MyD88) and for its function in immune cells.

Publications

Mutational analysis identifies residues crucial for homodimerization of myeloid differentiation factor 88 (MyD88) and for its function in immune cells.

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