Laboratory of RNA Function, Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan.
Laboratory of RNA Function, Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan; Department of Agrobiology and Bioresources, School of Agriculture, Utsunomiya University, Utsunomiya, Tochigi 321-8505, Japan.
Cell Rep. 2019 Jul 30;28(5):1144-1153.e4. doi: 10.1016/j.celrep.2019.07.003.
The Argonaute subfamily of proteins (AGO) loads microRNAs (miRNAs) to form the effector complex that mediates target gene silencing. Empty AGO, but not miRNA-loaded AGO, is selectively degraded across species. We have reported that the degradation of empty AGO is part of a quality control pathway that eliminates dysfunctional AGO. However, how empty AGO is degraded remains unclear. Here we show that the empty state of Drosophila Ago1 is degraded by autophagy. Comprehensive LC-MS/MS analyses, together with manipulation of the Ago1 ubiquitination level, revealed that VCP, which mediates selective autophagy, recognizes empty Ago1 via the Ufd1-Npl4 heterodimer. Depletion of VCP-Ufd1-Npl4 machinery impairs degradation of empty Ago1 and miRNA-mediated target gene silencing. Our findings reveal a direct link between empty AGO degradation and selective autophagy that ensures efficient miRNA function.
Argonaute 蛋白亚家族（AGO）将 microRNAs（miRNAs）加载到形成介导靶基因沉默的效应复合物中。空载的 AGO，而不是加载 miRNA 的 AGO，在不同物种中被选择性降解。我们已经报道空载 AGO 的降解是一种质量控制途径的一部分，该途径可以消除功能失调的 AGO。然而，空载 AGO 是如何被降解的仍然不清楚。在这里，我们表明果蝇 Ago1 的空载状态通过自噬降解。综合 LC-MS/MS 分析，以及对 Ago1 泛素化水平的操作，表明介导选择性自噬的 VCP 通过 Ufd1-Npl4 异二聚体识别空载 Ago1。VCP-Ufd1-Npl4 机制的耗竭会损害空载 Ago1 的降解和 miRNA 介导的靶基因沉默。我们的发现揭示了空载 AGO 降解与选择性自噬之间的直接联系，这确保了 miRNA 功能的高效性。
