Bacterial lipopolysaccharide triggers human caspase-4 (murine caspase-11) to cleave gasdermin-D and induce pyroptotic cell death. How lipopolysaccharide sequestered in the membranes of cytosol-invading bacteria activates caspases remains unknown. Here we show that in interferon-γ-stimulated cells guanylate-binding proteins (GBPs) assemble on the surface of Gram-negative bacteria into polyvalent signaling platforms required for activation of caspase-4. Caspase-4 activation is hierarchically controlled by GBPs; GBP1 initiates platform assembly, GBP2 and GBP4 control caspase-4 recruitment, and GBP3 governs caspase-4 activation. In response to cytosol-invading bacteria, activation of caspase-4 through the GBP platform is essential to induce gasdermin-D-dependent pyroptosis and processing of interleukin-18, thereby destroying the replicative niche for intracellular bacteria and alerting neighboring cells, respectively. Caspase-11 and GBPs epistatically protect mice against lethal bacterial challenge. Multiple antagonists of the pathway encoded by Shigella flexneri, a cytosol-adapted bacterium, provide compelling evolutionary evidence for the importance of the GBP–caspase-4 pathway in antibacterial defense.

细菌脂多糖触发人 caspase-4（鼠 caspase-11）切割 gasdermin-D 并诱导细胞焦亡。隔离在细胞质入侵细菌膜中的脂多糖如何激活半胱天冬酶仍然未知。在这里，我们表明，在干扰素-γ 刺激的细胞中，鸟苷酸结合蛋白 (GBP) 在革兰氏阴性菌表面组装成激活 caspase-4 所需的多价信号平台。Caspase-4 激活由 GBP 分级控制；GBP1 启动平台组装，GBP2 和 GBP4 控制 caspase-4 募集，GBP3 控制 caspase-4 激活。为响应细胞质入侵细菌，通过 GBP 平台激活 caspase-4 对于诱导 gasdermin-D 依赖性焦亡和白细胞介素 18 的加工至关重要，从而破坏细胞内细菌的复制生态位并分别警告相邻细胞。Caspase-11 和 GBPs 上位保护小鼠免受致命的细菌攻击。由编码的途径的多种拮抗剂福氏志贺氏菌是一种适应细胞质的细菌，为 GBP-caspase-4 途径在抗菌防御中的重要性提供了令人信服的进化证据。