Kathania Mahesh, Zeng Minghui, Yadav Viveka Nand, Moghaddam Seyed Javad, Yang Baoli, Venuprasad K
Baylor Institute for Immunology Research, Baylor Research Institute, Dallas, TX 75204;
Department of Pathology, University of Michigan, Ann Arbor, MI 48109;
J Immunol. 2015 Mar 1;194(5):2160-7. doi: 10.4049/jimmunol.1402742. Epub 2015 Jan 28.
The ubiquitin-ligating enzyme (E3) Itch plays a crucial role in the regulation of inflammation, and Itch deficiency leads to severe airway inflammation. However, the molecular mechanisms by which Itch function is regulated remain elusive. In this study, we found that nontypeable Haemophilus influenzae induces the association of Itch with Ndfip1. Both Itch(-/-) and Ndfip1(-/-) mice exhibited severe airway inflammation in response to nontypeable Haemophilus influenza, which was associated with elevated expression of proinflammatory cytokines. Ndfip1 enhanced Itch ligase activity and facilitated Itch-mediated Tak1 ubiquitination. Mechanistically, Ndfip1 facilitated recruitment of ubiquitin-conjugating enzyme (E2) UbcH7 to Itch. The N-terminal region of Ndfip1 binds to UbcH7, whereas the PY motif binds to Itch. Hence, Ndfip1 acts as an adaptor for UbcH7 and Itch. Reconstitution of full-length Ndfip1 but not the mutants that fail to interact with either UbcH7 or Itch, restored the defect in Tak1 ubiquitination and inhibited elevated proinflammatory cytokine expression by Ndfip1(-/-) cells. These results provide new mechanistic insights into how Itch function is regulated during inflammatory signaling, which could be exploited therapeutically in inflammatory diseases.
泛素连接酶（E3）Itch在炎症调节中起关键作用，Itch缺乏会导致严重的气道炎症。然而，Itch功能受调控的分子机制仍不清楚。在本研究中，我们发现不可分型流感嗜血杆菌可诱导Itch与Ndfip1结合。Itch基因敲除（Itch(-/-)）小鼠和Ndfip1基因敲除（Ndfip1(-/-)）小鼠对不可分型流感嗜血杆菌均表现出严重的气道炎症，这与促炎细胞因子表达升高有关。Ndfip1增强了Itch连接酶活性并促进了Itch介导的Tak1泛素化。机制上，Ndfip1促进泛素结合酶（E2）UbcH7与Itch的结合。Ndfip1的N端区域与UbcH7结合，而PY基序与Itch结合。因此，Ndfip1作为UbcH7和Itch的衔接蛋白。全长Ndfip1的重建而非不能与UbcH7或Itch相互作用的突变体，恢复了Tak1泛素化缺陷并抑制了Ndfip1(-/-)细胞中促炎细胞因子表达的升高。这些结果为炎症信号传导过程中Itch功能如何被调控提供了新的机制见解，这可能在炎症性疾病的治疗中得到应用。
