A novel transport pathway for a yeast plasma membrane protein encoded by a localized mRNA
A novel transport pathway for a yeast plasma membrane protein encoded by a localized mRNA
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DOI：
10.1016/j.cub.2004.02.034
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发表时间：
2004-03-09
期刊：
影响因子：
9.2
通讯作者：
Seedorf, M
中科院分区：
文献类型：
--
作者：
Jüschke, C;Ferring, D;Seedorf, M
一般来说，质膜（PM）蛋白质共同插入内质网（ER）中，并在囊泡中经由高尔基体行进到PM。在酿酒酵母中，多位膜蛋白Ist 2 p由位于子细胞皮质的mRNA编码[1-3]。已经表明，IST 2 mRNA定位导致蛋白质在子细胞的PM处积累[2]。由于小型和中型子细胞仅含有皮质ER，而不含有核周ER [4]，这意味着Ist 2 p的局部翻译特别是在皮质ER处。在这里，我们表明，组成型表达的IST 2 mRNA的本地化所需的Ist 2 p的女儿，但不是母细胞的PM交付，它不会导致在女儿特定的Ist 2 p积累。与遵循标准分泌途径的PM定位的己糖转运蛋白（Hxt 1 p）相反，Ist 2 p的贩运独立于肌球蛋白介导的囊泡转运。此外，共定位实验的分泌途径的突变体表明，贩运的Ist 2 p不需要经典的分泌机制。这些数据表明，存在一种新的贩运途径连接专门领域的ER与PM。
Generally, plasma membrane (PM) proteins are co-translationally inserted into the endoplasmic reticulum (ER) and travel in vesicles via the Golgi apparatus to the PM. In the yeast Saccharomyces cerevisiae, the polytopic membrane protein Ist2p is encoded by an mRNA that is localized to the cortex of daughter cells [1-3]. It has been suggested that IST2 mRNA localization leads to the accumulation of the protein at the PM of daughter cells [2]. Since small- and medium-sized daughter cells only contain cortical, but not perinuclear ER [4], this implies the local translation of Ist2p specifically at the cortical ER. Here, we show that localization of constitutively expressed IST2 mRNA is required for delivery of Ist2p to the PM of daughter, but not mother cells and that it does not result in daughter-specific Ist2p accumulation. In contrast to a PM-located hexose transporter (Hxt1p) that follows the standard secretory pathway, the trafficking of Ist2p is independent of myosin-mediated vesicular transport. Furthermore, colocalization experiments in mutants of the secretory pathway demonstrate that trafficking of Ist2p does not require the classical secretory machinery. These data suggest the existence of a novel trafficking pathway connecting specialized domains of the ER with the PM.