1. Modulation of TLR signaling by multiple MyD88-interacting partners including leucine-rich repeat Fli-I-interacting proteins.
- Author
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Dai P, Jeong SY, Yu Y, Leng T, Wu W, Xie L, and Chen X
- Subjects
- Adaptor Proteins, Signal Transducing, Animals, Binding, Competitive immunology, Carrier Proteins metabolism, Cell Line, Cell Line, Tumor, Cytoskeletal Proteins metabolism, Cytoskeletal Proteins physiology, Humans, Macrophages immunology, Macrophages metabolism, Mice, Mice, Inbred C3H, Microfilament Proteins physiology, Myeloid Differentiation Factor 88 metabolism, NF-kappa B antagonists & inhibitors, NF-kappa B metabolism, NF-kappa B physiology, Protein Binding immunology, RNA-Binding Proteins metabolism, Receptors, Cytoplasmic and Nuclear physiology, Toll-Like Receptor 4 agonists, Toll-Like Receptor 4 physiology, Trans-Activators, Carrier Proteins physiology, Microfilament Proteins metabolism, Myeloid Differentiation Factor 88 physiology, RNA-Binding Proteins physiology, Receptors, Cytoplasmic and Nuclear metabolism, Signal Transduction immunology, Toll-Like Receptor 4 metabolism
- Abstract
Emerging evidences suggest TLR-mediated signaling is tightly regulated by a specific chain of intracellular protein-protein interactions, some of which are yet to be identified. Previously we utilized a dual-tagging quantitative proteomics approach to uncover MyD88 interactions in LPS-stimulated cells and described the function of Fliih, a leucine-rich repeat (LRR) protein that negatively regulates NF-kappaB activity. Here we characterize two distinct LRR-binding MyD88 interactors, LRRFIP2 and Flap-1, and found that both are positive regulators of NF-kappaB activity. Upon LPS stimulation, LRRFIP2 was also found to positively regulate cytokine production in macrophages, suggesting a functional role in TLR4-mediated inflammatory response. Furthermore, we observed that immediately following LPS stimulation both LRRFIP2 and Flap-1 compete with Fliih for interacting with MyD88 to activate the signaling. By using a novel multiplex quantitative proteomic approach, we found that at endogenous levels these positive and negative regulators interact with MyD88 in a timely and orderly manner to differentially mediate the NF-kappaB activity through the course of signaling from initiation to prolongation, and to repression. Based on these data, we describe a mechanistic model in which selective modulation of TLR signaling is achieved by temporal and dynamic interactions of MyD88 with its regulators.
- Published
- 2009
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