Institute of Pharmacology and Structural Biology , University of Toulouse, CNRS , Toulouse, France.
Lee Kong Chian School of Medicine, Nanyang Technological University , Singapore, Singapore.
J Exp Med. 2023 Oct 2;220(10). doi: 10.1084/jem.20230104. Epub 2023 Aug 29.
Human airway and corneal epithelial cells, which are critically altered during chronic infections mediated by Pseudomonas aeruginosa, specifically express the inflammasome sensor NLRP1. Here, together with a companion study, we report that the NLRP1 inflammasome detects exotoxin A (EXOA), a ribotoxin released by P. aeruginosa type 2 secretion system (T2SS), during chronic infection. Mechanistically, EXOA-driven eukaryotic elongation factor 2 (EEF2) ribosylation and covalent inactivation promote ribotoxic stress and subsequent NLRP1 inflammasome activation, a process shared with other EEF2-inactivating toxins, diphtheria toxin and cholix toxin. Biochemically, irreversible EEF2 inactivation triggers ribosome stress-associated kinases ZAKα- and P38-dependent NLRP1 phosphorylation and subsequent proteasome-driven functional degradation. Finally, cystic fibrosis cells from patients exhibit exacerbated P38 activity and hypersensitivity to EXOA-induced ribotoxic stress-dependent NLRP1 inflammasome activation, a process inhibited by the use of ZAKα inhibitors. Altogether, our results show the importance of P. aeruginosa virulence factor EXOA at promoting NLRP1-dependent epithelial damage and identify ZAKα as a critical sensor of virulence-inactivated EEF2.
人呼吸道和角膜上皮细胞在铜绿假单胞菌介导的慢性感染过程中受到严重破坏，这些细胞特异性表达炎症小体传感器 NLRP1。在这里，我们与一项配套研究一起报告称，NLRP1 炎症小体可检测到铜绿假单胞菌 II 型分泌系统 (T2SS) 释放的外毒素 A (EXOA)，这是在慢性感染过程中发生的。从机制上讲，EXOA 驱动的真核延伸因子 2 (EEF2) 核糖体酰化和共价失活促进了核糖体毒性应激和随后的 NLRP1 炎症小体激活，这一过程与其他 EEF2 失活毒素、白喉毒素和霍乱毒素共享。从生物化学上讲，不可逆的 EEF2 失活触发核糖体应激相关激酶 ZAKα 和 P38 依赖性 NLRP1 磷酸化，随后被蛋白酶体驱动的功能降解。最后，来自患者的囊性纤维化细胞表现出增强的 P38 活性和对 EXOA 诱导的依赖核糖体毒性应激的 NLRP1 炎症小体激活的过度敏感，这一过程可被 ZAKα 抑制剂抑制。总而言之，我们的研究结果表明，铜绿假单胞菌毒力因子 EXOA 在促进 NLRP1 依赖性上皮细胞损伤方面具有重要作用，并确定 ZAKα 是一种对失活 EEF2 有感应作用的关键传感器。
