Aminopeptidase I is targeted to the vacuole by a nonclassical vesicular mechanism
Aminopeptidase I is targeted to the vacuole by a nonclassical vesicular mechanism
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DOI：
10.1083/jcb.138.1.37
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发表时间：
1997-07-14
影响因子：
7.8
通讯作者：
Klionsky, DJ
中科院分区：
文献类型：
--
作者：
Scott, SV;Baba, M;Klionsky, DJ
酵母液泡蛋白氨肽酶I（API）作为一种胞质前体被合成，它通过一种非经典的靶向机制被运输到液泡。近期的遗传学研究表明，运输API的生物合成途径使用了许多与降解性自噬途径相同的分子成分。这种重叠，加上对API输入的体外和体内分析，表明像自噬一样，API的运输是囊泡形式的。亚细胞分级分离实验表明，API前体（prAPI）最初进入一个非液泡的胞质区室。此外，从一个自噬体分解有缺陷的突变株中纯化出了含有prAPI的液泡内亚囊泡，这进一步表明prAPI是在一个囊泡内进入液泡的。纯化的液泡内亚囊泡似乎不含有液泡标记蛋白。免疫金电子显微镜证实，在一个自噬体降解有缺陷的突变株中，prAPI定位在胞质和液泡内亚囊泡中。这些数据表明，含有prAPI的胞质囊泡与液泡融合，释放出一个有膜包围的中间区室，这个中间区室随后被分解，使得API成熟。
The yeast vacuolar protein aminopeptidase I (API) is synthesized as a cytosolic precursor that is transported to the vacuole by a nonclassical targeting mechanism. Recent genetic studies indicate that the biosynthetic pathway that transports API uses many of the same molecular components as the degradative autophagy pathway. This overlap coupled with both in vitro and in vivo analysis of API import suggested that, like autophagy, API transport is vesicular. Subcellular fractionation experiments demonstrate that API precursor (prAPI) initially enters a nonvacuolar cytosolic compartment. In addition, subvacuolar vesicles containing prAPI were purified from a mutant strain defective in breakdown of autophagosomes, further indicating that prAPI enters the vacuole inside a vesicle. The purified subvacuolar vesicles do not appear to contain vacuolar marker proteins. Immunogold EM confirms that prAPI is localized in cytosolic and in subvacuolar vesicles in a mutant strain defective in autophagic body degradation. These data suggest that cytosolic vesicles containing prAPI fuse with the vacuole to release a membrane-bounded intermediate compartment that is subsequently broken down, allowing API maturation.