Cryo-EM structure of C9ORF72-SMCR8-WDR41 reveals the role as a GAP for Rab8a and Rab11a
Cryo-EM structure of C9ORF72-SMCR8-WDR41 reveals the role as a GAP for Rab8a and Rab11a
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C9ORF72-SMCR8-WDR41 的冷冻电镜结构揭示了 Rab8a 和 Rab11a 的 GAP 作用
DOI：
10.1073/pnas.2002110117
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发表时间：
2020
影响因子：
11.1
通讯作者：
Qi Shiqian
中科院分区：
文献类型：
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作者：
Tang Dan;Sheng Jingwen;Xu Liangting;Zhan Xiechao;Liu Jiaming;Jiang Hui;Shu Xiaoling;Liu Xiaoyu;Zhang Tizhong;Jiang Lan;Zhou Cuiyan;Li Wenqi;Cheng Wei;Li Zhonghan;Wang Kunjie;Lu Kefeng;Yan Chuangye;Qi Shiqian
C9 ORF 72的大规模内含子六核苷酸重复序列（GGGGCC）扩增是肌萎缩侧索硬化（ALS）和额颞叶痴呆（FTD）的遗传起源。最近，C9 ORF 72与SMCR 8和WDR 41一起被证明可以调节自噬并作为Rab GEF发挥功能。然而，C9 ORF 72的确切功能仍不清楚。在这里，我们报告的人C9 ORF 72-SMCR 8-WDR 41复合物的低温电子显微镜（cryo-EM）结构，分辨率为3.2 μ m。该结构揭示了C9 ORF 72-SMCR 8-WDR 41的异源三聚体的二聚体组装。值得注意的是，C9 ORF 72的C末端尾和SMCR 8的DENN结构域在C9 ORF 72-SMCR 8-WDR 41复合物的两个原聚体的二聚化中起关键作用。在原聚体中，C9 ORF 72和WDR 41通过SMCR 8连接而没有直接相互作用。WDR 41通过C-末端螺旋结合SMCR 8的DENN结构域。有趣的是，C9 ORF 72-SMCR 8的突出结构特征类似于FLNC-FNIP 2复合物，即RagC/D的GTP酶激活蛋白（GAP）。结构比较和序列比对显示SMCR 8的Arg 147是保守的，对应于FLCN的精氨酸指，生化分析表明SMCR 8的Arg 147是C9 ORF 72-SMCR 8复合物对Rab 8a和Rab 11 a的刺激作用的关键。我们的研究不仅阐明了C9 ORF 72-SMCR 8-WDR 41复合物组装的基础，而且揭示了C9 ORF 72-SMCR 8复合物差距活性。
A massive intronic hexanucleotide repeat (GGGGCC) expansion inC9ORF72is a genetic origin of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Recently, C9ORF72, together with SMCR8 and WDR41, has been shown to regulate autophagy and function as Rab GEF. However, the precise function of C9ORF72 remains unclear. Here, we report the cryogenic electron microscopy (cryo-EM) structure of the human C9ORF72–SMCR8–WDR41 complex at a resolution of 3.2 Å. The structure reveals the dimeric assembly of a heterotrimer of C9ORF72–SMCR8–WDR41. Notably, the C-terminal tail of C9ORF72 and the DENN domain of SMCR8 play critical roles in the dimerization of the two protomers of the C9ORF72–SMCR8–WDR41 complex. In the protomer, C9ORF72 and WDR41 are joined by SMCR8 without direct interaction. WDR41 binds to the DENN domain of SMCR8 by the C-terminal helix. Interestingly, the prominent structural feature of C9ORF72–SMCR8 resembles that of the FLNC–FNIP2 complex, the GTPase activating protein (GAP) of RagC/D. Structural comparison and sequence alignment revealed that Arg147 of SMCR8 is conserved and corresponds to the arginine finger of FLCN, and biochemical analysis indicated that the Arg147 of SMCR8 is critical to the stimulatory effect of the C9ORF72–SMCR8 complex on Rab8a and Rab11a. Our study not only illustrates the basis of C9ORF72–SMCR8–WDR41 complex assembly but also reveals the GAP activity of the C9ORF72–SMCR8 complex.