Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA.
Department of Physiology and Biophysics, and the Department of Ophthalmology, University of California, Irvine, CA, USA.
Nat Commun. 2020 May 5;11(1):2212. doi: 10.1038/s41467-020-16043-9.
Gasdermin-D (GSDMD) in inflammasome-activated macrophages is cleaved by caspase-1 to generate N-GSDMD fragments. N-GSDMD then oligomerizes in the plasma membrane (PM) to form pores that increase membrane permeability, leading to pyroptosis and IL-1β release. In contrast, we report that although N-GSDMD is required for IL-1β secretion in NLRP3-activated human and murine neutrophils, N-GSDMD does not localize to the PM or increase PM permeability or pyroptosis. Instead, biochemical and microscopy studies reveal that N-GSDMD in neutrophils predominantly associates with azurophilic granules and LC3 autophagosomes. N-GSDMD trafficking to azurophilic granules causes leakage of neutrophil elastase into the cytosol, resulting in secondary cleavage of GSDMD to an alternatively cleaved N-GSDMD product. Genetic analyses using ATG7-deficient cells indicate that neutrophils secrete IL-1β via an autophagy-dependent mechanism. These findings reveal fundamental differences in GSDMD trafficking between neutrophils and macrophages that underlie neutrophil-specific functions during inflammasome activation.
Gasdermin-D (GSDMD) 在炎症小体激活的巨噬细胞中被半胱天冬酶-1 切割，生成 N-GSDMD 片段。然后，N-GSDMD 在质膜 (PM) 上寡聚化形成孔，增加膜通透性，导致细胞焦亡和 IL-1β 释放。相比之下，我们报告称，尽管 N-GSDMD 是 NLRP3 激活的人源和鼠源中性粒细胞中 IL-1β 分泌所必需的，但 N-GSDMD 并不定位在 PM 上，也不会增加 PM 通透性或细胞焦亡。相反，生化和显微镜研究表明，中性粒细胞中的 N-GSDMD 主要与嗜天青颗粒和 LC3 自噬体相关。N-GSDMD 向嗜天青颗粒的转运导致中性粒细胞弹性蛋白酶漏入细胞质，导致 GSDMD 的二次切割产生另一种切割的 N-GSDMD 产物。使用 ATG7 缺陷细胞进行的遗传分析表明，中性粒细胞通过自噬依赖性机制分泌 IL-1β。这些发现揭示了中性粒细胞和巨噬细胞之间 GSDMD 转运的根本差异，这是炎症小体激活期间中性粒细胞特异性功能的基础。
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