Modulation of TLR signaling by multiple MyD88-interacting partners including leucine-rich repeat Fli-I-interacting proteins

J Immunol. 2009 Mar 15;182(6):3450-60. doi: 10.4049/jimmunol.0802260.

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.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Animals
  • Binding, Competitive / immunology
  • Carrier Proteins / metabolism
  • Carrier Proteins / physiology*
  • Cell Line
  • Cell Line, Tumor
  • Cytoskeletal Proteins / metabolism
  • Cytoskeletal Proteins / physiology
  • Humans
  • Macrophages / immunology
  • Macrophages / metabolism
  • Mice
  • Mice, Inbred C3H
  • Microfilament Proteins / metabolism*
  • Microfilament Proteins / physiology
  • Myeloid Differentiation Factor 88 / metabolism
  • Myeloid Differentiation Factor 88 / physiology*
  • NF-kappa B / antagonists & inhibitors
  • NF-kappa B / metabolism
  • NF-kappa B / physiology
  • Protein Binding / immunology
  • RNA-Binding Proteins / metabolism
  • RNA-Binding Proteins / physiology*
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Receptors, Cytoplasmic and Nuclear / physiology
  • Signal Transduction / immunology*
  • Toll-Like Receptor 4 / agonists
  • Toll-Like Receptor 4 / metabolism*
  • Toll-Like Receptor 4 / physiology
  • Trans-Activators

Substances

  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • Cytoskeletal Proteins
  • FLII protein, human
  • FlII protein, mouse
  • LRRFIP1 protein, human
  • LRRFIP2 protein, human
  • MYD88 protein, human
  • Microfilament Proteins
  • Myeloid Differentiation Factor 88
  • NF-kappa B
  • RNA-Binding Proteins
  • Receptors, Cytoplasmic and Nuclear
  • TLR4 protein, human
  • Toll-Like Receptor 4
  • Trans-Activators