Mechanism of dysfunction of human variants of the IRAK4 kinase and a role for its kinase activity in interleukin-1 receptor signaling
Mechanism of dysfunction of human variants of the IRAK4 kinase and a role for its kinase activity in interleukin-1 receptor signaling
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DOI：
10.1074/jbc.ra118.003831
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发表时间：
2018-09-28
影响因子：
4.8
通讯作者：
Rao, Vikram R.
中科院分区：
文献类型：
--
作者：
De, Saurav;Karim, Fawziya;Rao, Vikram R.
白介素 1 受体 (IL1R) 相关激酶 4 (IRAK4) 是先天免疫信号传导的中央调节因子，控制 IL1R 和 Toll 样受体 (TLR) 介导的反应，并包含支架和激酶活性。缺乏 IRAK4 活性的人类患有常染色体隐性原发性免疫缺陷 (PID)。在这里，我们表征了两种 IRAK4 PID 变体 G298D 和复合变体 R12C (R12C/R391H/T458I) 功能障碍的分子机制。使用这些变体和激酶失活的 D329A 变体来描述 IRAK4 的支架和激酶活性对 IL1R 信号传导的贡献，我们发现 G298D 变体是激酶失活的并且以极低的水平表达，在功能上充当无效突变。 R12C 复合变体具有 WT 激酶活性，但不能与骨髓分化初级反应 88 (MyD88) 和 IRAK1 相互作用，从而导致 IL-1 诱导的信号传导和细胞因子产生受损。在用 WT 或 R12C 或 D329A 变体补充的 IRAK4 缺陷细胞中对 IL-1 信号传导进行定量表明，MyD88 相互作用的丧失对 IL-1 诱导的信号传导和细胞因子表达的影响比 IRAK4 激酶活性的丧失更大。重要的是，在表达激酶失活IRAK4的IRAK4缺陷细胞和用选择性IRAK4抑制剂处理的原代细胞中，激酶失活IRAK4与MyD88的关联性更强，而与IRAK1的关联性更弱。 IRAK4 激酶活性的丧失仅部分抑制 IL-1 诱导的细胞因子和 NF-B 信号传导。因此，IRAK4-MyD88支架功能对于IL-1信号传导至关重要，但IRAK4激酶活性可以通过调节IRAK4、MyD88和IRAK1的关联来控制IL-1信号强度。
Interleukin-1 receptor (IL1R)-associated kinase 4 (IRAK4) is a central regulator of innate immune signaling, controlling IL1R and Toll-like receptor (TLR)-mediated responses and containing both scaffolding and kinase activities. Humans deficient in IRAK4 activity have autosomal recessive primary immune deficiency (PID). Here, we characterized the molecular mechanism of dysfunction of two IRAK4 PID variants, G298D and the compound variant R12C (R12C/R391H/T458I). Using these variants and the kinase-inactive D329A variant to delineate the contributions of IRAK4's scaffolding and kinase activities to IL1R signaling, we found that the G298D variant is kinase-inactive and expressed at extremely low levels, acting functionally as a null mutation. The R12C compound variant possessed WT kinase activity, but could not interact with myeloid differentiation primary response 88 (MyD88) and IRAK1, causing impairment of IL-1-induced signaling and cytokine production. Quantitation of IL-1 signaling in IRAK4-deficient cells complemented with either WT or the R12C or D329A variant indicated that the loss of MyD88 interaction had a greater impact on IL-1-induced signaling and cytokine expression than the loss of IRAK4 kinase activity. Importantly, kinase-inactive IRAK4 exhibited a greater association with MyD88 and a weaker association with IRAK1 in IRAK4-deficient cells expressing kinase-inactive IRAK4 and in primary cells treated with a selective IRAK4 inhibitor. Loss of IRAK4 kinase activity only partially inhibited IL-1-induced cytokine and NF-B signaling. Therefore, the IRAK4-MyD88 scaffolding function is essential for IL-1 signaling, but IRAK4 kinase activity can control IL-1 signal strength by modulating the association of IRAK4, MyD88, and IRAK1.