Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zurich, Basel, Switzerland.
Biozentrum, University of Basel, Basel, Switzerland.
EMBO J. 2018 Jul 13;37(14). doi: 10.15252/embj.201798321. Epub 2018 Jun 13.
Gasdermin-D (GSDMD), a member of the gasdermin protein family, mediates pyroptosis in human and murine cells. Cleaved by inflammatory caspases, GSDMD inserts its N-terminal domain (GSDMD) into cellular membranes and assembles large oligomeric complexes permeabilizing the membrane. So far, the mechanisms of GSDMD insertion, oligomerization, and pore formation are poorly understood. Here, we apply high-resolution (≤ 2 nm) atomic force microscopy (AFM) to describe how GSDMD inserts and assembles in membranes. We observe GSDMD inserting into a variety of lipid compositions, among which phosphatidylinositide (PI(4,5)P2) increases and cholesterol reduces insertion. Once inserted, GSDMD assembles arc-, slit-, and ring-shaped oligomers, each of which being able to form transmembrane pores. This assembly and pore formation process is independent on whether GSDMD has been cleaved by caspase-1, caspase-4, or caspase-5. Using time-lapse AFM, we monitor how GSDMD assembles into arc-shaped oligomers that can transform into larger slit-shaped and finally into stable ring-shaped oligomers. Our observations translate into a mechanistic model of GSDMD transmembrane pore assembly, which is likely shared within the gasdermin protein family.
Gasdermin-D (GSDMD)，gasdermin 蛋白家族的一员，介导人和鼠细胞中的细胞焦亡。炎性半胱天冬酶（caspase）切割 GSDMD 后，其 N 端结构域（GSDMD）插入细胞膜并组装成大的寡聚体复合物，使细胞膜穿孔。到目前为止，GSDMD 插入、寡聚化和孔形成的机制仍知之甚少。在此，我们应用高分辨率（≤2nm）原子力显微镜（AFM）来描述 GSDMD 在膜中的插入和组装方式。我们观察到 GSDMD 插入多种脂质组成，其中磷脂酰肌醇（PI(4,5)P2）增加而胆固醇减少插入。一旦插入，GSDMD 组装成弧形、狭缝形和环形寡聚体，每个寡聚体都能形成跨膜孔。该组装和孔形成过程不依赖于 GSDMD 是否被 caspase-1、caspase-4 或 caspase-5 切割。通过延时 AFM，我们监测 GSDMD 如何组装成弧形寡聚体，进而转变成较大的狭缝形，最终形成稳定的环形寡聚体。我们的观察结果转化为 GSDMD 跨膜孔组装的机制模型，这可能在 gasdermin 蛋白家族中是普遍存在的。
