title: Multivesicular bodies associate with components of miRNA effector complexes and modulate miRNA activity.
abstract: 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.
authors.affiliation: IBMP-CNRS, UPR Université de Strasbourg, France.
authors.forename: Derrick J
authors.initials: DJ
authors.lastname: Gibbings
authors.forename: Constance
authors.initials: C
authors.lastname: Ciaudo
authors.forename: Mathieu
authors.initials: M
authors.lastname: Erhardt
authors.forename: Olivier
authors.initials: O
authors.lastname: Voinnet
mesh_terms: D060565:Argonaute Proteins; D001324:Autoantigens / Q000378:metabolism; D002460:Cell Line; D004722:Endoribonucleases / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism* / Q000648:ultrastructure; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D055354:Exosomes / Q000378:metabolism / Q000648:ultrastructure; D055785:Gene Knockdown Techniques; D006801:Humans; D035683:MicroRNAs / Q000378:metabolism*; D021381:Protein Transport; D016601:RNA-Binding Proteins; D015534:Trans-Activators / Q000378:metabolism
chemical_list: C466422:AGO2 protein, human; D060565:Argonaute Proteins; D001324:Autoantigens; D015852:Eukaryotic Initiation Factor-2; D035683:MicroRNAs; D016601:RNA-Binding Proteins; C465663:TNRC6A protein, human; D015534:Trans-Activators; D004722:Endoribonucleases; C466279:DCP1A protein, human
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