AIP1 functions as Arf6-GAP to negatively regulate TLR4 signaling

J Biol Chem. 2010 Feb 5;285(6):3750-3757. doi: 10.1074/jbc.M109.069385. Epub 2009 Nov 30.

Abstract

Toll-like receptor 4 (TLR4) is unique among the Toll-like receptors in its ability to utilize TLR/IL1R-domain-containing adaptor protein (TIRAP), which recruits TLR4-MyD88 to phosphatidylinositol 4,5-bisphosphate (PIP(2))-rich sites on the plasma membrane, to activate NF-kappaB and MAPK pathways. Here, we show that AIP1 disrupts formation of the TLR4- TIRAP-MyD88 complex without directly binding to any of the complex components. AIP1 via its pleckstrin homology and C2 domains binds to phosphatidylinositol 4-phosphate, a lipid precursor of PIP(2). Knock-out of AIP1 in cells increases and overexpression of AIP1 reduces cellular PIP(2) levels. We further show that AIP1 is a novel GTPase-activating protein (GAP) for Arf6, a small GTPase regulating cellular PIP(2) production and formation of the TLR4-TIRAP-MyD88 complex. Thus, deletion of the GAP domain on AIP1 results in a loss of its ability to mediate the inhibition of Arf6- and TLR4-induced signaling events. We conclude that AIP1 functions as a novel Arf6-GAP to negatively regulate PIP(2)-dependent TLR4-TIRAP-MyD88 signaling.

Publication types

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

MeSH terms

  • ADP-Ribosylation Factor 6
  • ADP-Ribosylation Factors / genetics
  • ADP-Ribosylation Factors / metabolism*
  • Adaptor Proteins, Signal Transducing
  • Amino Acid Sequence
  • Animals
  • COS Cells
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cattle
  • Cell Line
  • Cells, Cultured
  • Chlorocebus aethiops
  • GTPase-Activating Proteins / genetics
  • GTPase-Activating Proteins / metabolism*
  • Guanylate Kinases
  • Humans
  • Immunoblotting
  • Lipopolysaccharides / pharmacology
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / metabolism
  • Mice
  • Mice, Knockout
  • Mitogen-Activated Protein Kinases / metabolism
  • Molecular Sequence Data
  • Myeloid Differentiation Factor 88 / genetics
  • Myeloid Differentiation Factor 88 / metabolism
  • NF-kappa B / metabolism
  • Phosphatidylinositol 4,5-Diphosphate / metabolism
  • Protein Binding
  • Receptors, Interleukin-1 / genetics
  • Receptors, Interleukin-1 / metabolism
  • Sequence Homology, Amino Acid
  • Toll-Like Receptor 4 / genetics
  • Toll-Like Receptor 4 / metabolism*
  • Transfection

Substances

  • ADP-Ribosylation Factor 6
  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • GTPase-Activating Proteins
  • Lipopolysaccharides
  • MYD88 protein, human
  • Membrane Glycoproteins
  • Myeloid Differentiation Factor 88
  • NF-kappa B
  • Phosphatidylinositol 4,5-Diphosphate
  • Receptors, Interleukin-1
  • TIRAP protein, human
  • Toll-Like Receptor 4
  • Mitogen-Activated Protein Kinases
  • Guanylate Kinases
  • MAGI2 protein, human
  • ADP-Ribosylation Factors
  • ARF6 protein, human
  • Arf6 protein, mouse