Exocyst subunit Exo70B2 is linked to immune signaling and autophagy
Exocyst subunit Exo70B2 is linked to immune signaling and autophagy
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DOI：
10.1093/plcell/koaa022
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发表时间：
2021-02-01
期刊：
影响因子：
11.6
通讯作者：
Trujillo, Marco
中科院分区：
文献类型：
--
作者：
Brillada, Carla;Teh, Ooi-Kock;Trujillo, Marco
在免疫反应过程中，分泌途径的激活对于发起有效反应至关重要，而衡量其输出对于维持细胞内稳态也很重要。胞泌复合体的Exo70亚基通过介导与蛋白质和脂质的众多相互作用，充当一种时空调节因子。然而，从分子层面理解胞泌复合体的调控仍然具有挑战性。我们发现，在拟南芥中，Exo70B2是一个真正的胞泌复合体亚基。相反，用水杨酸（SA）防御激素类似物苯并噻二唑（BTH）或免疫原性肽flg22处理，会诱导Exo70B2转运到液泡中。我们揭示Exo70B2通过两个与自噬相关蛋白8（ATG8）相互作用的基序（AIMs）与ATG8相互作用，并且其向液泡的转运依赖于自噬。与它在免疫中的作用一致，我们发现Exo70B2与激酶MPK3相互作用并被其磷酸化。模拟磷酸化对Exo70B2有双重影响：首先，抑制其在活性分泌位点的定位；其次，增加与ATG8的相互作用。磷酸化缺失变体表现出更高的效应物触发免疫（ETI），并且对诱导分泌和自噬的BTH高度敏感。我们的研究结果表明了一种分子机制，即磷酸化使Exo70B2从分泌途径转向自噬途径进行降解，从而抑制分泌活性。
During the immune response, activation of the secretory pathway is key to mounting an effective response, while gauging its output is important to maintain cellular homeostasis. The Exo70 subunit of the exocyst functions as a spatiotemporal regulator by mediating numerous interactions with proteins and lipids. However, a molecular understanding of the exocyst regulation remains challenging. We show that, in Arabidopsis thaliana, Exo70B2 behaves as a bona fide exocyst subunit. Conversely, treatment with the salicylic acid (SA) defence hormone analog benzothiadiazole (BTH), or the immunogenic peptide flg22, induced Exo70B2 transport into the vacuole. We reveal that Exo70B2 interacts with AUTOPHAGY-RELATED PROTEIN 8 (ATG8) via two ATG8-interacting motives (AIMs) and its transport into the vacuole is dependent on autophagy. In line with its role in immunity, we discovered that Exo70B2 interacted with and was phosphorylated by the kinase MPK3. Mimicking phosphorylation had a dual impact on Exo70B2: first, by inhibiting localization at sites of active secretion, and second, it increased the interaction with ATG8. Phosphonull variants displayed higher effector-triggered immunity (ETI) and were hypersensitive to BTH, which induce secretion and autophagy. Our results suggest a molecular mechanism by which phosphorylation diverts Exo70B2 from the secretory into the autophagy pathway for its degradation, to dampen secretory activity.