Mal connects TLR2 to PI3Kinase activation and phagocyte polarization

EMBO J. 2009 Jul 22;28(14):2018-27. doi: 10.1038/emboj.2009.158. Epub 2009 Jul 2.

Abstract

The recognition of bacterial lipoproteins by toll-like receptor (TLR) 2 is pivotal for inflammation initiation and control in many bacterial infections. TLR2-dependent signalling is currently believed to essentially require both adaptor proteins MyD88 (myeloid differentiation primary response gene 88) and Mal/TIRAP (MyD88-adapter-like/TIR-domain-containing adaptor protein). TLR2-dependent, but MyD88-independent responses have not been described yet. We report here on a novel-signalling pathway downstream of TLR2, which does not adhere to the established model. On stimulation of the TLR2/6 heterodimer with diacylated bacterial lipoproteins, Mal directly interacts with the regulatory subunit of phosphoinositide 3-kinase (PI3K), p85alpha, in an inducible fashion. The Mal-p85alpha interaction drives PI3K-dependent phosphorylation of Akt, phosphatidylinositol(3,4,5)P3 (PIP(3)) generation and macrophage polarization. MyD88 is not essential for PI3K activation and Akt phosphorylation; however, cooperates with Mal for PIP(3) formation and accumulation at the leading edge. In contrast to TLR2/6, TLR2/1 does not require Mal or MyD88 for Akt phosphorylation. Hence, Mal specifically connects TLR2/6 to PI3K activation, PIP(3) generation and macrophage polarization.

Publication types

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

MeSH terms

  • Animals
  • Cell Line
  • Cell Polarity
  • Humans
  • Macrophages / cytology
  • Macrophages / immunology*
  • Membrane Glycoproteins / metabolism*
  • Mice
  • Minor Histocompatibility Antigens
  • Myeloid Differentiation Factor 88 / genetics
  • Myeloid Differentiation Factor 88 / metabolism
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Receptors, Interleukin-1 / metabolism*
  • Signal Transduction*
  • Toll-Like Receptor 2 / immunology
  • Toll-Like Receptor 2 / metabolism*

Substances

  • MYD88 protein, human
  • Membrane Glycoproteins
  • Minor Histocompatibility Antigens
  • Myeloid Differentiation Factor 88
  • Receptors, Interleukin-1
  • TIRAP protein, human
  • TLR2 protein, human
  • Toll-Like Receptor 2
  • Phosphotransferases (Alcohol Group Acceptor)
  • phosphatidylinositol phosphate 4-kinase