Zhang Liman, Chen Shuobing, Ruan Jianbin, Wu Jiayi, Tong Alexander B, Yin Qian, Li Yang, David Liron, Lu Alvin, Wang Wei Li, Marks Carolyn, Ouyang Qi, Zhang Xinzheng, Mao Youdong, Wu Hao
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA. Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA.
Center for Quantitative Biology, Peking-Tsinghua Joint Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China. Department of Cancer Immunology and Virology, Intel Parallel Computing Center for Structural Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA.
Science. 2015 Oct 23;350(6259):404-9. doi: 10.1126/science.aac5789. Epub 2015 Oct 8.
The NLR family apoptosis inhibitory proteins (NAIPs) bind conserved bacterial ligands, such as the bacterial rod protein PrgJ, and recruit NLR family CARD-containing protein 4 (NLRC4) as the inflammasome adapter to activate innate immunity. We found that the PrgJ-NAIP2-NLRC4 inflammasome is assembled into multisubunit disk-like structures through a unidirectional adenosine triphosphatase polymerization, primed with a single PrgJ-activated NAIP2 per disk. Cryo-electron microscopy (cryo-EM) reconstruction at subnanometer resolution revealed a ~90° hinge rotation accompanying NLRC4 activation. Unlike in the related heptameric Apaf-1 apoptosome, in which each subunit needs to be conformationally activated by its ligand before assembly, a single PrgJ-activated NAIP2 initiates NLRC4 polymerization in a domino-like reaction to promote the disk assembly. These insights reveal the mechanism of signal amplification in NAIP-NLRC4 inflammasomes.
NLR家族凋亡抑制蛋白（NAIPs）可结合保守的细菌配体，如细菌杆状蛋白PrgJ，并招募含NLR家族CARD的蛋白4（NLRC4）作为炎性小体接头来激活先天免疫。我们发现，PrgJ-NAIP2-NLRC4炎性小体通过单向三磷酸腺苷酶聚合组装成多亚基盘状结构，每个盘以单个PrgJ激活的NAIP2为起始。亚纳米分辨率的冷冻电子显微镜（cryo-EM）重建显示，伴随NLRC4激活有~90°的铰链旋转。与相关的七聚体Apaf-1凋亡小体不同，在Apaf-1凋亡小体中，每个亚基在组装前需要被其配体进行构象激活，而单个PrgJ激活的NAIP2以多米诺样反应启动NLRC4聚合，以促进盘状组装。这些见解揭示了NAIP-NLRC4炎性小体中信号放大的机制。
