Mouse caspase-11 and human caspase-4 and caspase-5 recognize cytosolic lipopolysaccharide (LPS) to induce pyroptosis by cleaving the pore-forming protein GSDMD^1,2,3,4,5. This non-canonical inflammasome defends against Gram-negative bacteria^6,7. Shigella flexneri, which causes bacillary dysentery, lives freely within the host cytosol where these caspases reside. However, the role of caspase-11-mediated pyroptosis in S. flexneri infection is unknown. Here we show that caspase-11 did not protect mice from S. flexneri infection, in contrast to infection with another cytosolic bacterium, Burkholderia thailandensis⁸. S. flexneri evaded pyroptosis mediated by caspase-11 or caspase 4 (hereafter referred to as caspase-11/4) using a type III secretion system (T3SS) effector, OspC3. OspC3, but not its paralogues OspC1 and 2, covalently modified caspase-11/4; although it used the NAD⁺ donor, this modification was not ADP-ribosylation. Biochemical dissections uncovered an ADP-riboxanation modification on Arg314 and Arg310 in caspase-4 and caspase-11, respectively. The enzymatic activity was shared by OspC1 and 2, whose ankyrin-repeat domains, unlike that of OspC3, could not recognize caspase-11/4. ADP-riboxanation of the arginine blocked autoprocessing of caspase-4/11 as well as their recognition and cleavage of GSDMD. ADP-riboxanation of caspase-11 paralysed pyroptosis-mediated defence in Shigella-infected mice and mutation of ospC3 stimulated caspase-11- and GSDMD-dependent anti-Shigella humoral immunity, generating a vaccine-like protective effect. Our study establishes ADP-riboxanation of arginine as a bacterial virulence mechanism that prevents LPS-induced pyroptosis.

小鼠 caspase-11 和人类 caspase-4 和 caspase-5 识别细胞溶质脂多糖 (LPS)，通过切割成孔蛋白 GSDMD ^{1、2、3、4、5}来诱导细胞焦亡。这种非典型炎症小体可抵御革兰氏阴性菌^6,7。引起细菌性痢疾的福氏志贺氏菌自由生活在这些半胱天冬酶所在的宿主细胞质中。然而，caspase-11 介导的细胞焦亡在S中的作用。 福氏感染是未知的。在这里，我们表明 caspase-11 不能保护小鼠免受S。 福氏菌感染，与另一种细胞溶质细菌Burkholderia thailandensis的感染形成对比⁸。年代。 flexneri使用 III 型分泌系统 (T3SS) 效应器 OspC3 避免了由 caspase-11 或 caspase 4（以下称为 caspase-11/4）介导的细胞焦亡。OspC3，但不是其旁系同源物 OspC1 和 2，共价修饰 caspase-11/4；尽管它使用了 NAD ⁺供体，但这种修饰不是 ADP 核糖基化。生化解剖发现分别在 caspase-4 和 caspase-11 中的 Arg314 和 Arg310 上存在 ADP 核糖化修饰。酶活性由 OspC1 和 2 共享，其锚蛋白重复结构域与 OspC3 不同，不能识别 caspase-11/4。精氨酸的 ADP 核糖化阻断了 caspase-4/11 的自动加工以及它们对 GSDMD 的识别和切割。Caspase-11 的 ADP 核糖化瘫痪了细胞焦亡介导的防御志贺氏菌感染小鼠和ospC3突变刺激 caspase-11 和 GSDMD 依赖性抗志贺氏菌体​​液免疫，产生类似疫苗的保护作用。我们的研究确立了精氨酸的 ADP 核糖化作为防止 LPS 诱导的细胞焦亡的细菌毒力机制。