Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
Department of Natural Sciences, International Christian University, Tokyo, Japan.
Elife. 2018 May 11;7:e34064. doi: 10.7554/eLife.34064.
RAB5 is a key regulator of endosomal functions in eukaryotic cells. Plants possess two different RAB5 groups, canonical and plant-unique types, which act via unknown counteracting mechanisms. Here, we identified an effector molecule of the plant-unique RAB5 in , ARA6, which we designated PLANT-UNIQUE RAB5 EFFECTOR 2 (PUF2). Preferential colocalization with canonical RAB5 on endosomes and genetic interaction analysis indicated that PUF2 coordinates vacuolar transport with canonical RAB5, although PUF2 was identified as an effector of ARA6. Competitive binding of PUF2 with GTP-bound ARA6 and GDP-bound canonical RAB5, together interacting with the shared activating factor VPS9a, showed that ARA6 negatively regulates canonical RAB5-mediated vacuolar transport by titrating PUF2 and VPS9a. These results suggest a unique and unprecedented function for a RAB effector involving the integration of two RAB groups to orchestrate endosomal trafficking in plant cells.
RAB5 是真核细胞内内体功能的关键调节因子。植物拥有两种不同的 RAB5 群，即经典和植物特有的类型，它们通过未知的拮抗机制发挥作用。在这里，我们鉴定了植物特有的 RAB5 的一个效应分子，ARA6，我们将其命名为植物特有的 RAB5 效应子 2（PUF2）。优先与内体上的经典 RAB5 共定位以及遗传相互作用分析表明，PUF2 与经典 RAB5 一起协调液泡运输，尽管 PUF2 被鉴定为 ARA6 的效应子。PUF2 与 GTP 结合的 ARA6 和 GDP 结合的经典 RAB5 的竞争性结合，以及与共享激活因子 VPS9a 的相互作用表明，ARA6 通过滴定 PUF2 和 VPS9a 负调节经典 RAB5 介导的液泡运输。这些结果表明，一种涉及两个 RAB 群整合以协调植物细胞内体运输的 RAB 效应子具有独特的、前所未有的功能。
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