Department of Radiotherapy, Cancer Center, State Key Laboratory of Biotherapy, West China Hospital, National Clinical Research Center for Geriatrics, Sichuan University, Chengdu 610041, China.
State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China.
Proc Natl Acad Sci U S A. 2024 Jun 18;121(25):e2316551121. doi: 10.1073/pnas.2316551121. Epub 2024 Jun 12.
The NLRP3 inflammasome, a pivotal component of innate immunity, has been implicated in various inflammatory disorders. The ubiquitin-editing enzyme A20 is well known to regulate inflammation and maintain homeostasis. However, the precise molecular mechanisms by which A20 modulates the NLRP3 inflammasome remain poorly understood. Here, our study revealed that macrophages deficient in A20 exhibit increased protein abundance and elevated mRNA level of NIMA-related kinase 7 (NEK7). Importantly, A20 directly binds with NEK7, mediating its K48-linked ubiquitination, thereby targeting NEK7 for proteasomal degradation. Our results demonstrate that A20 enhances the ubiquitination of NEK7 at K189 and K293 ubiquitinated sites, with K189 playing a crucial role in the binding of NEK7 to A20, albeit not significantly influencing the interaction between NEK7 and NLRP3. Furthermore, A20 disrupts the association of NEK7 with the NLRP3 complex, potentially through the OTU domain and/or synergistic effect of ZnF4 and ZnF7 motifs. Significantly, NEK7 deletion markedly attenuates the activation of the NLRP3 inflammasome in A20-deficient conditions, both in vitro and in vivo. This study uncovers a mechanism by which A20 inhibits the NLRP3 inflammasome.
NLRP3 炎性小体是先天免疫的关键组成部分，与各种炎症性疾病有关。泛素修饰酶 A20 是众所周知的调节炎症和维持体内平衡的酶。然而，A20 调节 NLRP3 炎性小体的确切分子机制仍知之甚少。在这里，我们的研究表明，缺乏 A20 的巨噬细胞表现出 NIMA 相关激酶 7（NEK7）的蛋白丰度增加和 mRNA 水平升高。重要的是，A20 直接与 NEK7 结合，介导其 K48 连接的泛素化，从而将 NEK7 靶向蛋白酶体降解。我们的结果表明，A20 增强了 NEK7 在 K189 和 K293 泛素化位点的泛素化，K189 在 NEK7 与 A20 的结合中起着关键作用，尽管它对 NEK7 与 NLRP3 的相互作用没有显著影响。此外，A20 破坏了 NEK7 与 NLRP3 复合物的关联，可能是通过 OTU 结构域和/或 ZnF4 和 ZnF7 结构域的协同作用。重要的是，NEK7 的缺失显著减弱了 A20 缺陷条件下 NLRP3 炎性小体的激活，无论是在体外还是体内。这项研究揭示了 A20 抑制 NLRP3 炎性小体的一种机制。
