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IRAK4 dimerization and trans-autophosphorylation are induced by Myddosome assembly

Ryan Ferrao1, Hao Zhou2, Yibing Shan3

  • 1Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA; Weill Cornell Graduate School of Medical Sciences, New York, NY 10065, USA.

Molecular Cell
|September 10, 2014
PubMed

Insights

Interleukin-1 receptor-associated kinase 4 (IRAK4) is activated through dimerization, a process crucial for its autophosphorylation and downstream signaling in immune pathways. This study reveals how IRAK4 dimerization drives its autoactivation mechanism.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Immunology

Background:

  • Trans-autophosphorylation is a common protein kinase activation mechanism, but its details remain unclear.
  • Interleukin-1 receptor-associated kinase 4 (IRAK4) is essential for Toll-like receptor and interleukin-1 receptor signaling, mediating NF-κB activation via the Myddosome complex.

Purpose of the Study:

  • To elucidate the molecular basis of IRAK4 activation through trans-autophosphorylation.
  • To investigate the role of dimerization in IRAK4 kinase activity and signaling.

Main Methods:

  • Determined the dissociation constant (KD) for unphosphorylated IRAK4 dimerization.
  • Obtained the crystal structure of the unphosphorylated IRAK4 dimer.
  • Assessed IRAK4 autophosphorylation in vitro and ligand-dependent signaling in cellular models.

Main Results:

  • Unphosphorylated IRAK4 dimerizes with a KD of 2.5 μM.
  • Myddosome assembly significantly enhances IRAK4 autophosphorylation.
  • Crystal structure reveals a conformation poised for trans-autophosphorylation.
  • Dimerization is essential for both in vitro IRAK4 autophosphorylation and cellular signaling.

Conclusions:

  • IRAK4 activation occurs via an oligomerization-driven allosteric mechanism.
  • Dimerization facilitates trans-autophosphorylation by positioning the activation loop phosphosite.
  • This mechanism of autoactivation may be applicable to other kinases activated by autophosphorylation.

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