Two Fission Yeast Rab7 Homologs, Ypt7 and Ypt71, Play Antagonistic Roles in the Regulation of Vacuolar Morphology
Two Fission Yeast Rab7 Homologs, Ypt7 and Ypt71, Play Antagonistic Roles in the Regulation of Vacuolar Morphology
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DOI：
10.1111/j.1600-0854.2009.00907.x
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发表时间：
2009-07-01
期刊：
影响因子：
4.5
通讯作者：
Nakamura, Taro
中科院分区：
文献类型：
--
作者：
Kashiwazaki, Jun;Iwaki, Tomoko;Nakamura, Taro
Rab家族的小鸟嘌呤三磷酸酶（GTP酶）是真核细胞中各种亚细胞区室之间的膜运输事件的关键调节剂。Rab 7是一种在晚期内吞途径和溶酶体生物发生中所需的保守蛋白。对粟酒裂殖酵母（S. Rab 7的同源物Ypt 7是从内体运输到液泡和同型液泡融合所必需的。在这里，我们确定并表征了第二个裂变酵母Rab 7同源物Ypt 71。Ypt 71定位于液泡膜。缺失ypt 71（+）的细胞表现出正常的生长速率和形态。有趣的是，ypt 71无效突变体含有大的空泡，与ypt 7无效突变体中发现的小碎片空泡相反。此外，ypt 71突变不增强或减轻ypt 7 δ细胞的温度敏感性或空泡融合缺陷。与ypt 7 δ细胞一样，ypt 71（+）的过表达导致空泡碎裂，并抑制低渗条件下的空泡融合。因此，两个S。粟酒酵母Rab 7同源物在调节液泡形态中起拮抗作用。嵌合Ypt 7/Ypt 71蛋白的分析表明，Rab 7定向空泡动力学，融合与分裂，在很大程度上取决于蛋白质的中间区域，包括RabSF 3/α 3-L7的一部分。
Small guanine triphosphatases (GTPases) of the Rab family are key regulators of membrane trafficking events between the various subcellular compartments in eukaryotic cells. Rab7 is a conserved protein required in the late endocytic pathway and in lysosome biogenesis. A Schizosaccharomyces pombe (S. pombe) homolog of Rab7, Ypt7, is necessary for trafficking from the endosome to the vacuole and for homotypic vacuole fusion. Here, we identified and characterized a second fission yeast Rab7 homolog, Ypt71. Ypt71 is localized to the vacuolar membrane. Cells deleted for ypt71(+) exhibit normal growth rates and morphology. Interestingly, a ypt71 null mutant contains large vacuoles in contrast with the small fragmented vacuoles found in the ypt7 null mutant. Furthermore, the ypt71 mutation does not enhance or alleviate the temperature sensitivity or vacuole fusion defect of ypt7 delta cells. Like ypt7 delta cells, overexpression of ypt71(+) caused fragmentation of vacuoles and inhibits vacuole fusion under hypotonic conditions. Thus, the two S. pombe Rab7 homologs act antagonistically in regulating vacuolar morphology. Analysis of a chimeric Ypt7/Ypt71 protein showed that Rab7-directed vacuole dynamics, fusion versus fission, largely depends on the medial region of the protein, including a part of RabSF3/alpha 3-L7.