Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA.
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA.
Nature. 2018 May;557(7703):62-67. doi: 10.1038/s41586-018-0058-6. Epub 2018 Apr 25.
Gasdermins mediate inflammatory cell death after cleavage by caspases or other, unknown enzymes. The cleaved N-terminal fragments bind to acidic membrane lipids to form pores, but the mechanism of pore formation remains unresolved. Here we present the cryo-electron microscopy structures of the 27-fold and 28-fold single-ring pores formed by the N-terminal fragment of mouse GSDMA3 (GSDMA3-NT) at 3.8 and 4.2 Å resolutions, and of a double-ring pore at 4.6 Å resolution. In the 27-fold pore, a 108-stranded anti-parallel β-barrel is formed by two β-hairpins from each subunit capped by a globular domain. We identify a positively charged helix that interacts with the acidic lipid cardiolipin. GSDMA3-NT undergoes radical conformational changes upon membrane insertion to form long, membrane-spanning β-strands. We also observe an unexpected additional symmetric ring of GSDMA3-NT subunits that does not insert into the membrane in the double-ring pore, which may represent a pre-pore state of GSDMA3-NT. These structures provide a basis that explains the activities of several mutant gasdermins, including defective mutants that are associated with cancer.
Gasdermins 介导了被半胱天冬酶或其他未知酶切割后的炎症细胞死亡。裂解的 N 端片段与酸性膜脂质结合形成孔，但孔形成的机制仍未解决。在这里，我们展示了在 3.8 和 4.2Å分辨率下，由小鼠 GSDMA3（GSDMA3-NT）的 N 端片段形成的 27 倍和 28 倍单环孔，以及在 4.6Å分辨率下的双环孔的冷冻电镜结构。在 27 倍孔中，由每个亚基的两个 β-发夹形成的 108 股反平行 β-桶被球状结构域覆盖。我们确定了一个正电荷的螺旋与酸性脂质心磷脂相互作用。GSDMA3-NT 在插入膜时发生剧烈的构象变化，形成长的、跨膜的 β-链。我们还观察到双环孔中未插入膜中的 GSDMA3-NT 亚基的意外的额外对称环，这可能代表 GSDMA3-NT 的前孔状态。这些结构提供了一个基础，解释了几种突变型 gasdermins 的活性，包括与癌症相关的缺陷型突变体。
