The vacuolar import and degradation pathway merges with the endocytic pathway to deliver fructose-1,6-bisphosphatase to the vacuole for degradation
The vacuolar import and degradation pathway merges with the endocytic pathway to deliver fructose-1,6-bisphosphatase to the vacuole for degradation
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DOI：
10.1074/jbc.m709922200
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发表时间：
2008-09-19
影响因子：
4.8
通讯作者：
Chiang, Hui-Ling
中科院分区：
文献类型：
--
作者：
Brown, C. Randell;Wolfe, Allison B.;Chiang, Hui-Ling
当向葡萄糖饥饿的细胞中加入葡萄糖时，液泡中的果糖-1，6-二磷酸酶（FBPase）被降解。然而，在它被递送到液泡之前，FBPase被输入到称为Vid（液泡输入和降解）囊泡的中间载体中。在这里，使用生物化学和遗传学方法，我们确定了FBPase降解中对SEC 28的需求。SEC 28编码COPI（外壳蛋白复合物I）外被体蛋白的α-COP亚基。当SEC 28和其他coatomer基因突变，FBPase降解是有缺陷的和FBPase与Vid囊泡协会受损。被鉴定为Vid囊泡的组分，并且它们与Vid囊泡特异性蛋白Vid 24 p形成蛋白质复合物。此外，Vid 24 p与Vid囊泡的关联受损时，外壳基因突变。动力学研究表明，Sec 28 p可运输到多个地点。Sec 28 p存在于Vid囊泡、内吞隔室和阻断FBPase降解途径的各种突变体中的液泡膜中。在ret 2 -1外被体突变体中，sec 28 p也存在于液泡膜附近的小泡中。我们建议Sec 28 p驻留在Vid囊泡中，这些囊泡与内吞途径会聚。融合后，Sec 28 p分布在液泡膜上，在那里它集中在从这个细胞器夹断的囊泡上。FBPase还利用内吞途径运输到液泡，如其存在于Delta vph 1突变体的内吞隔室中所证明的。两者合计，我们的结果表明Vid运输途径和内吞途径之间有很强的联系。
The gluconeogenic enzyme fructose-1,6-bisphosphatase (FBPase) is degraded in the vacuole when glucose is added to glucose-starved cells. Before it is delivered to the vacuole, however, FBPase is imported into intermediate carriers called Vid ( vacuole import and degradation) vesicles. Here, using biochemical and genetic approaches, we identified a requirement for SEC28 in FBPase degradation. SEC28 encodes the alpha-COP subunit of COPI ( coat protein complex I) coatomer proteins. When SEC28 and other coatomer genes were mutated, FBPase degradation was defective and FBPase association with Vid vesicles was impaired. Coatomer proteins were identified as components of Vid vesicles, and they formed a protein complex with a Vid vesicle-specific protein, Vid24p. Furthermore, Vid24p association with Vid vesicles was impaired when coatomer genes were mutated. Kinetic studies indicated that Sec28p traffics to multiple locations. Sec28p was in Vid vesicles, endocytic compartments, and the vacuolar membrane in various mutants that block the FBPase degradation pathway. Sec28p was also found in vesicles adjacent to the vacuolar membrane in the ret2-1 coatomer mutant. We propose that Sec28p resides in Vid vesicles, and these vesicles converge with the endocytic pathway. After fusion, Sec28p is distributed on the vacuolar membrane, where it concentrates on vesicles that pinch off from this organelle. FBPase also utilizes the endocytic pathway for transport to the vacuole, as demonstrated by its presence in endocytic compartments in the Delta vph1 mutant. Taken together, our results indicate a strong connection between the Vid trafficking pathway and the endocytic pathway.