Multivesicular bodies associate with components of miRNA effector complexes and modulate miRNA activity
Multivesicular bodies associate with components of miRNA effector complexes and modulate miRNA activity
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DOI：
10.1038/ncb1929
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发表时间：
2009-09-01
影响因子：
21.3
通讯作者：
Voinnet, Olivier
中科院分区：
文献类型：
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作者：
Gibbings, Derrick J.;Ciaudo, Constance;Voinnet, Olivier
在动物中，P体或GW体似乎引起参与microRNA（miRNA）介导的转录后沉默的蛋白质聚集。P体的定位与已知的细胞器不重叠，因此被认为是独立于脂质双层的。尽管如此，一种miRNA效应蛋白argonaute 2（AGO2）最初被鉴定为膜相关的，并且一些miRNA已经在分泌囊泡（外来体）中被发现，所述分泌囊泡（外来体）来源于称为多泡体（MVB）的内溶酶体隔室。蛋白质可以通过三种异聚体亚复合物（统称为ESCRT（转运所需的内体分选复合物））以泛素依赖性方式分选成MVB，以进一步分泌到外泌体中和/或被溶酶体降解。在这里，我们表明，GW-体含有GW 182和AGO2，RNA诱导的沉默复合物（RISC）的两个主要组成部分，是不同的P-体，由于其聚集与内体和MVB。此外，miRNA和miRNA抑制性mRNA在这些细胞膜上富集，这表明内体和/或MVB是加载miRNA的RISC（miRISC）积累和可能作用的位点。我们进一步表明，纯化的外泌体样囊泡分泌的MVB是相当丰富的GW182，但不是P体成分，AGO2或miRNA抑制的mRNA。此外，一些ESCRT成分耗尽的细胞显示出受损的miRNA介导的基因沉默和过度积累的GW182，其与泛素化蛋白质相关。因此，GW182，可能与一部分加载miRNA的AGO2结合，被分选到MVB中用于分泌和/或溶酶体降解。我们认为，这一过程促进了膜相关miRISC的连续组装或拆卸，这可能是miRNA加载或靶点识别以及随后沉默所必需的。
In animals, P-bodies or GW-bodies appear to cause the congregation of proteins involved in microRNA (miRNA)-mediated post-transcriptional silencing. The localization of P-bodies does not overlap with that of known organelles and are thus considered independent of lipid bilayers. Nonetheless, an miRNA effector protein, argonaute 2 (AGO2), was initially identified as membrane-associated, and some miRNAs have been found in secreted vesicles (exosomes) that derive from endo-lysosomal compartments called multivesicular bodies (MVBs). Proteins can be sorted in a ubiquitin-dependent manner into MVBs by three heteromeric subcomplexes, collectively termed ESCRT (endosomal sorting complex required for transport), to be further secreted in exosomes and/or degraded by the lysosome. Here we show that GW-bodies containing GW182 and AGO2, two main components of the RNA-induced silencing complex (RISC), are distinct from P-bodies due to their congregation with endosomes and MVBs. Moreover, miRNAs and miRNA-repressible mRNAs are enriched at these cellular membranes, suggesting that endosomes and/or MVBs are sites of miRNA-loaded RISC (miRISC) accumulation and, possibly, action. We further show that purified exosome-like vesicles secreted by MVBs are considerably enriched in GW182, but not P-body components, AGO2 or miRNA-repressible mRNA. Moreover, cells depleted of some ESCRT components show compromised miRNA-mediated gene silencing and over-accumulate GW182, which associates with ubiquitylated proteins. Therefore, GW182, possibly in association with a fraction of miRNA-loaded AGO2, is sorted into MVBs for secretion and/or lysosomal degradation. We propose that this process promotes continuous assembly or disassembly of membrane-associated miRISCs, which is possibly required for miRNA loading or target recognition and subsequent silencing.