Medical Research Council Protein Phosphorylation and Ubiquitylation Unit and Division of Cell Signaling and Immunology, Sir James Black Centre, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom.
Proc Natl Acad Sci U S A. 2013 Sep 17;110(38):15247-52. doi: 10.1073/pnas.1314715110. Epub 2013 Aug 28.
Polyubiquitin (pUb) chains formed between the C terminus of ubiquitin and lysine 63 (K63) or methionine 1 (M1) of another ubiquitin have been implicated in the activation of the canonical IκB kinase (IKK) complex. Here, we demonstrate that nearly all of the M1-pUb chains formed in response to interleukin-1, or the Toll-Like Receptors 1/2 agonist Pam3CSK4, are covalently attached to K63-pUb chains either directly as K63-pUb/M1-pUb hybrids or indirectly by attachment to the same protein. Interleukin-1 receptor (IL-1R)-associated kinase (IRAK) 1 is modified first by K63-pUb chains to which M1-pUb linkages are added subsequently, and myeloid differentiation primary response gene 88 (MyD88) and IRAK4 are also modified by both K63-pUb and M1-pUb chains. We show that the heme-oxidized IRP2 ubiquitin ligase 1 interacting protein (HOIP) component of the linear ubiquitin assembly complex catalyzes the formation of M1-pUb chains in response to interleukin-1, that the formation of K63-pUb chains is a prerequisite for the formation of M1-pUb chains, and that HOIP interacts with K63-pUb but not M1-pUb linkages. These findings identify K63-Ub oligomers as a major substrate of HOIP in cells where the MyD88-dependent signaling network is activated. The TGF-beta-activated kinase 1 (TAK1)-binding protein (TAB) 2 and TAB3 components of the TAK1 complex and the NFκB Essential Modifier (NEMO) component of the canonical IKK complex bind to K63-pUb chains and M1-pUb chains, respectively. The formation of K63/M1-pUb hybrids may therefore provide an elegant mechanism for colocalizing both complexes to the same pUb chain, facilitating the TAK1-catalyzed activation of IKKα and IKKβ. Our study may help to resolve the debate about the relative importance of K63-pUb and M1-pUb chains in activating the canonical IKK complex.
多聚泛素（pUb）链是由泛素 C 末端与赖氨酸 63（K63）或甲硫氨酸 1（M1）之间形成的，它们与经典 IκB 激酶（IKK）复合物的激活有关。在这里，我们证明，几乎所有在白细胞介素 1 或 Toll 样受体 1/2 激动剂 Pam3CSK4 反应中形成的 M1-pUb 链，要么直接作为 K63-pUb/M1-pUb 杂合体，要么间接通过与同一蛋白结合，共价连接到 K63-pUb 链上。白细胞介素 1 受体（IL-1R）相关激酶（IRAK）1 首先被 K63-pUb 链修饰，随后再添加 M1-pUb 连接物，髓样分化初级反应基因 88（MyD88）和 IRAK4 也被 K63-pUb 和 M1-pUb 链修饰。我们表明，线性泛素组装复合物的血红素氧化酶诱导的 IRP2 泛素连接酶 1 相互作用蛋白（HOIP）组成部分催化白细胞介素 1 反应中 M1-pUb 链的形成，K63-pUb 链的形成是 M1-pUb 链形成的前提，HOIP 与 K63-pUb 相互作用，但不与 M1-pUb 连接物相互作用。这些发现确定了 K63-Ub 低聚物是细胞中 MyD88 依赖性信号网络激活时 HOIP 的主要底物。TGF-β激活激酶 1（TAK1）结合蛋白（TAB）2 和 TAB3 是 TAK1 复合物的成分，NFκB 必需修饰物（NEMO）是经典 IKK 复合物的成分，分别与 K63-pUb 链和 M1-pUb 链结合。因此，K63/M1-pUb 杂合体的形成可能为将两个复合物聚集到同一 pUb 链上提供了一种优雅的机制，从而促进 TAK1 催化的 IKKα 和 IKKβ 的激活。我们的研究可能有助于解决 K63-pUb 和 M1-pUb 链在激活经典 IKK 复合物方面的相对重要性的争论。
