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IRAK4 dimerization and trans-autophosphorylation are induced by Myddosome assembly.

ABSTRACT: Trans-autophosphorylation is among the most prevalent means of protein kinase activation, yet its molecular basis is poorly defined. In Toll-like receptor and interleukin-1 receptor signaling pathways, the kinase IRAK4 is recruited to the membrane-proximal adaptor MyD88 through death domain (DD) interactions, forming the oligomeric Myddosome and mediating NF-?B activation. Here we show that unphosphorylated IRAK4 dimerizes in solution with a KD of 2.5 ?M and that Myddosome assembly greatly enhances IRAK4 kinase domain (KD) autophosphorylation at sub-KD concentrations. The crystal structure of the unphosphorylated IRAK4(KD) dimer captures a conformation that appears to represent the actual trans-autophosphorylation reaction, with the activation loop phosphosite of one IRAK4 monomer precisely positioned for phosphotransfer by its partner. We show that dimerization is crucial for IRAK4 autophosphorylation in vitro and ligand-dependent signaling in cells. These studies identify a mechanism for oligomerization-driven allosteric autoactivation of IRAK4 that may be general to other kinases activated by autophosphorylation.

SUBMITTER: Ferrao R

PROVIDER: S-EPMC4169746 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature

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IRAK4 dimerization and trans-autophosphorylation are induced by Myddosome assembly.

Ferrao Ryan R Zhou Hao H Shan Yibing Y Liu Qun Q Li Qiubai Q Shaw David E DE Li Xiaoxia X Wu Hao H

Molecular cell 20140904 6

Trans-autophosphorylation is among the most prevalent means of protein kinase activation, yet its molecular basis is poorly defined. In Toll-like receptor and interleukin-1 receptor signaling pathways, the kinase IRAK4 is recruited to the membrane-proximal adaptor MyD88 through death domain (DD) interactions, forming the oligomeric Myddosome and mediating NF-κB activation. Here we show that unphosphorylated IRAK4 dimerizes in solution with a KD of 2.5 μM and that Myddosome assembly greatly enhan ...[more]

PMID: 25201411

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Project description:Diffuse large B‑cell lymphoma (DLBCL), the most common type of non‑Hodgkin's lymphoma, is classified into germinal center and activated B cell (ABC) subtypes. The myeloid differentiation primary response gene 88 (MYD88) L265P mutation is the most prevalent oncogenic mutation among patients with ABC DLBCL, the subtype that has the more inferior outcome. MYD88 oligomerization driven by the L265P mutant augments myddosome assembly and triggers the activation of nuclear factor kappa‑light‑chain‑enhancer of activated B cells (NF‑κB) signaling, highlighting MYD88 oligomerization as a potential therapeutic target for this malignancy. The synthetic peptidomimetic compound ST2825, which has previously been used as an anti‑inflammatory agent, has been reported to inhibit MYD88 dimerization. In the present study, the anticancer effects of ST2825 were investigated using L265P‑expressing ABC DLBCL cell lines. Using confocal microscopy and high‑molecular‑weight fraction experiments, it was revealed that L265P‑associated myddosome assembly was disrupted by ST2825. The results also revealed that disrupting myddosome assembly promoted the death of ABC DLBCL cells harboring the L265P mutation, as well as downregulating survival signals, including the inhibition of NF‑κB and the suppression of IL‑10 and interferon‑β production. Further co‑immunoprecipitation studies demonstrated that MYD88 bound to BTK in L265P‑DLBCL cells, and that this binding was abrogated following ST2825 treatment. Furthermore, the combination of myddosome‑assembly disruption and BTK or BCL‑2 signaling inhibition led to synergistic ABC DLBCL cell death, and more robust inhibition of NF‑κB activity or increased apoptosis, respectively. The results of the present study provide evidence that the synthetic peptidomimetic compound ST2825, which targets myddosome assembly, may serve as a pharmacological inhibitor. ST2825 has the potential for clinical use in patients with L265P DLBCL, and other B‑cell neoplasms driven by activated MYD88 signaling.

Dataset Information

IRAK4 dimerization and trans-autophosphorylation are induced by Myddosome assembly.

Publications

IRAK4 dimerization and trans-autophosphorylation are induced by Myddosome assembly.

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