A C-terminal motif contributes to the plasma membrane localization of Arabidopsis STP transporters.
A C-terminal motif contributes to the plasma membrane localization of Arabidopsis STP transporters.
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DOI：
10.1371/journal.pone.0186326
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发表时间：
2017
期刊：
影响因子：
3.7
通讯作者：
Yamaguchi-Shinozaki K
中科院分区：
文献类型：
--
作者：
Yamada K;Osakabe Y;Yamaguchi-Shinozaki K
膜运输是高度组织化的，以维持任何生物体的细胞稳态。膜嵌入转运蛋白针对各种细胞器，以对其底物（例如离子或糖）进行适当的分配和分配。为了确保靶向和分选的保真度，包括转运蛋白在内的膜蛋白具有指定亚细胞目的地和到达目的地的运输途径的分选信号。在这里，我们发现了一种新的分选信号（称为三芳香基序），它包含三个芳香残基、两个色氨酸和一个组氨酸，用于拟南芥中 STP 家族糖转运蛋白的质膜定位。我们首先发现C端缺失破坏了酵母细胞中STP1的糖摄取活性。额外的缺失和突变分析表明，C 末端的三个芳香族残基在所有拟南芥 STP 转运蛋白中都是保守的，不仅对 STP1 的糖摄取至关重要，而且对另一种 STP 转运蛋白 STP13 的糖摄取也至关重要。我们观察到，当三芳香族基序突变时，STP1 大部分定位于酵母细胞的内膜区室，表明这种不正确的亚细胞定位导致了糖吸收的损失。重要的是，我们的进一步分析发现，三芳香族基序的突变导致植物细胞中STP1和STP13的内质网（ER）保留，表明该基序参与STP转运蛋白的ER退出步骤，以促进其质膜定位。我们一起鉴定了一种新的 ER 输出信号，并表明通过三芳香族基序进行适当的分选对于 STP 转运蛋白的糖吸收非常重要。
Membrane trafficking is highly organized to maintain cellular homeostasis in any organisms. Membrane-embedded transporters are targeted to various organelles to execute appropriate partition and allocation of their substrates, such as ions or sugars. To ensure the fidelity of targeting and sorting, membrane proteins including transporters have sorting signals that specify the subcellular destination and the trafficking pathway by which the destination is to be reached. Here, we have identified a novel sorting signal (called the tri-aromatic motif) which contains three aromatic residues, two tryptophans and one histidine, for the plasma membrane localization of sugar transporters in the STP family in Arabidopsis. We firstly found that a C-terminal deletion disrupted the sugar uptake activity of STP1 in yeast cells. Additional deletion and mutation analyses demonstrated that the three aromatic residues in the C-terminus, conserved among all Arabidopsis STP transporters, were critical for sugar uptake by not only STP1 but also another STP transporter STP13. We observed that, when the tri-aromatic motif was mutated, STP1 was largely localized at the endomembrane compartments in yeast cells, indicating that this improper subcellular localization led to the loss of sugar absorption. Importantly, our further analyses uncovered that mutations of the tri-aromatic motif resulted in the endoplasmic reticulum (ER) retention of STP1 and STP13 in plant cells, suggesting that this motif is involved at the step of ER exit of STP transporters to facilitate their plasma membrane localization. Together, we here identified a novel ER export signal, and showed that appropriate sorting via the tri-aromatic motif is important for sugar absorption by STP transporters.
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