Zhang Jiangtao, Zhan Chunhua, Fan Junping, Wu Dian, Zhang Ruixue, Wu Di, Chen Xinyao, Lu Ying, Li Ming, Lin Min, Gong Jianke, Jiang Daohua
College of Life Science and Technology, Key Laboratory of Molecular Biophysics of MOE, Huazhong University of Science and Technology, Wuhan, Hubei, China.
Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.
Nat Struct Mol Biol. 2024 Jul;31(7):1095-1104. doi: 10.1038/s41594-024-01276-9. Epub 2024 Apr 25.
RNA uptake by cells is critical for RNA-mediated gene interference (RNAi) and RNA-based therapeutics. In Caenorhabditis elegans, RNAi is systemic as a result of SID-1-mediated double-stranded RNA (dsRNA) across cells. Despite the functional importance, the underlying mechanisms of dsRNA internalization by SID-1 remain elusive. Here we describe cryogenic electron microscopy structures of SID-1, SID-1-dsRNA complex and human SID-1 homologs SIDT1 and SIDT2, elucidating the structural basis of dsRNA recognition and import by SID-1. The homodimeric SID-1 homologs share conserved architecture, but only SID-1 possesses the molecular determinants within its extracellular domains for distinguishing dsRNA from single-stranded RNA and DNA. We show that the removal of the long intracellular loop between transmembrane helix 1 and 2 attenuates dsRNA uptake and systemic RNAi in vivo, suggesting a possible endocytic mechanism of SID-1-mediated dsRNA internalization. Our study provides mechanistic insights into dsRNA internalization by SID-1, which may facilitate the development of dsRNA applications based on SID-1.
细胞摄取RNA对于RNA介导的基因干扰（RNAi）和基于RNA的治疗至关重要。在秀丽隐杆线虫中，由于SID-1介导双链RNA（dsRNA）跨细胞传递，RNAi具有系统性。尽管其功能重要，但SID-1介导dsRNA内化的潜在机制仍不清楚。在这里，我们描述了SID-1、SID-1-dsRNA复合物以及人类SID-1同源物SIDT1和SIDT2的低温电子显微镜结构，阐明了SID-1识别和导入dsRNA的结构基础。同二聚体的SID-1同源物具有保守的结构，但只有SID-1在其细胞外结构域中具有区分dsRNA与单链RNA和DNA的分子决定因素。我们表明，去除跨膜螺旋1和2之间的长细胞内环会减弱体内dsRNA摄取和系统性RNAi，这表明SID-1介导dsRNA内化可能存在一种内吞机制。我们的研究为SID-1介导的dsRNA内化提供了机制性见解，这可能有助于基于SID-1的dsRNA应用的开发。
