Plasticity in PYD assembly revealed by cryo-EM structure of the PYD filament of AIM2.
Plasticity in PYD assembly revealed by cryo-EM structure of the PYD filament of AIM2.
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DOI：
10.1038/celldisc.2015.13
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发表时间：
2015
期刊：
影响因子：
33.5
通讯作者：
Wu H
中科院分区：
文献类型：
--
作者：
Lu A;Li Y;Yin Q;Ruan J;Yu X;Egelman E;Wu H
在黑素瘤2（AIM 2）中缺少必需的胞质双链DNA受体，其与衔接子、含有半胱天冬酶募集结构域（ASC）的凋亡相关斑点样蛋白和半胱天冬酶-1组装以形成AIM 2炎性体，其导致细胞因子的蛋白水解成熟和焦萎性细胞死亡。AIM 2含有N-末端Pyrin结构域（PYD），其通过PYD/PYD相互作用与ASC相互作用并使ASCPYD丝形成成核。为了阐明AIM 2诱导的ASCPYD聚合的分子基础，我们产生了融合到绿色荧光蛋白（GFP）的AIM 2 PYD细丝，并确定了其冷冻电子显微镜（cryo-EM）结构。图谱显示螺旋的清晰定义，允许拟合晶体结构。令人惊讶的是，GFP-AIM 2 PYD细丝是1-起始螺旋，其螺旋参数与3-起始ASCPYD细丝的螺旋参数不同。然而，尽管有明显的对称性差异，螺旋网和详细的界面分析显示，在亚基包装的变化很小。GFP-AIM 2 PYD以与未标记的AIM 2 PYD相当的效率使ASCPYD丝形成成核，表明AIM 2 PYD和ASCPYD两者中的组装可塑性。AIM 2的DNA结合结构域能够形成AIM 2/DNA细丝，其中AIM 2 PYD接近模板ASCPYD细丝组装。由于ASC能够与许多含有PYD的受体相互作用以形成炎性小体，因此观察到的结构可塑性对于PYD/PYD相互作用中的这种多功能性可能至关重要。
Absent in melanoma 2 (AIM2) is an essential cytosolic double-stranded DNA receptor that assembles with the adaptor, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and caspase-1 to form the AIM2 inflammasome, which leads to proteolytic maturation of cytokines and pyroptotic cell death. AIM2 contains an N-terminal Pyrin domain (PYD) that interacts with ASC through PYD/PYD interactions and nucleates ASCPYD filament formation. To elucidate the molecular basis of AIM2-induced ASCPYD polymerization, we generated AIM2PYD filaments fused to green fluorescent protein (GFP) and determined its cryo-electron microscopic (cryo-EM) structure. The map showed distinct definition of helices, allowing fitting of the crystal structure. Surprisingly, the GFP-AIM2PYD filament is a 1-start helix with helical parameters distinct from those of the 3-start ASCPYD filament. However, despite the apparent symmetry difference, helical net and detailed interface analyses reveal minimal changes in subunit packing. GFP-AIM2PYD nucleated ASCPYD filament formation in comparable efficiency as untagged AIM2PYD, suggesting assembly plasticity in both AIM2PYD and ASCPYD. The DNA-binding domain of AIM2 is able to form AIM2/DNA filaments, within which the AIM2PYD is brought into proximity to template ASCPYD filament assembly. Because ASC is able to interact with many PYD-containing receptors for the formation of inflammasomes, the observed structural plasticity may be critically important for this versatility in the PYD/PYD interactions.