National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
New Phytol. 2022 Aug;235(4):1486-1500. doi: 10.1111/nph.18201. Epub 2022 May 24.
Protein sorting is an essential biological process in all organisms. Trafficking membrane proteins generally relies on the sorting machinery of the Golgi apparatus. However, many proteins have been found to be delivered to target locations via Golgi-independent pathways, but the mechanisms underlying this delivery system remain unknown. Here, we report that Sec24C mediates the direct secretory trafficking of the phytochelatin transporters ABCC1 and ABCC2 from the endoplasmic reticulum (ER) to prevacuolar compartments (PVCs) in Arabidopsis thaliana. Genetic analysis showed that the sec24c mutants are hypersensitive to cadmium (Cd) and arsenic (As) treatments due to mislocalisation of ABCC1 and ABCC2, which results in defects in the vacuole compartmentalisation of the toxic metals. Furthermore, we found that Sec24C recognises ABCC1 and ABCC2 through direct interactions to mediate their exit from the ER to PVCs, which is independent of brefeldin A-sensitive post-Golgi trafficking pathway. These findings expand our understanding of Golgi-independent trafficking, which also provide key insights regarding the mechanism of tonoplast protein sorting and open a new perspective on the function of Sec24 proteins.
蛋白质分拣是所有生物中必不可少的生物过程。膜蛋白的运输通常依赖于高尔基体的分拣机制。然而，许多蛋白质已被发现通过高尔基体非依赖途径被递送到靶位，但该递送系统的机制仍不清楚。在这里，我们报告 Sec24C 介导植物螯合肽转运蛋白 ABCC1 和 ABCC2 从内质网 (ER) 到拟南芥液泡前区室 (PVC) 的直接分泌运输。遗传分析表明，sec24c 突变体由于 ABCC1 和 ABCC2 的定位错误而对镉 (Cd) 和砷 (As) 处理敏感，这导致有毒金属的液泡区室化缺陷。此外，我们发现 Sec24C 通过直接相互作用识别 ABCC1 和 ABCC2，从而介导它们从 ER 到 PVC 的输出，这独立于布雷菲德菌素 A 敏感的高尔基体后运输途径。这些发现扩展了我们对高尔基体非依赖性运输的理解，也为液泡膜蛋白分拣的机制提供了关键见解，并为 Sec24 蛋白的功能开辟了新的视角。
