Amino acids regulate retrieval of the yeast general amino acid permease from the vacuolar targeting pathway.
Amino acids regulate retrieval of the yeast general amino acid permease from the vacuolar targeting pathway.
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DOI：
10.1091/mbc.e05-07-0669
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发表时间：
2006-07
影响因子：
3.3
通讯作者：
Marta Rubio‐Texeira;C. Kaiser
中科院分区：
文献类型：
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作者：
Marta Rubio‐Texeira;C. Kaiser
酿酒酵母中的一般氨基酸通透酶（Gap 1 p）的细胞内分选取决于氨基酸的可用性，使得在低氨基酸浓度下Gap 1 p被分选到质膜，而在高浓度下Gap 1 p被分选到液泡。在全基因组范围内筛选影响Gap 1 p分选的突变时，我们发现了ESCRT（转运所需的内体分选复合物）复合物的一部分成分缺失，这是形成多泡内体（MVE）所必需的。Gap 1 p-GFP在野生型细胞中通过MVE途径传递到液泡内部，但当MVE的形成被突变阻断时，Gap 1 p-GFP有效地从该隔室循环到质膜，导致细胞表面异常高的通透酶活性。重要的是，Gap 1 p-GFP到质膜的循环被高浓度的氨基酸阻断，将内体的再循环定义为生理控制下Gap 1 p运输的主要步骤。LST 4和LST 7基因的突变，以前确定其在Gap 1 p分选中的作用，类似地阻止MVE到Gap 1 p的质膜运输。然而，在其他回收复合物，如retromer突变Gap 1 p的细胞内分选没有显着的影响，这表明Gap 1 p遵循遗传上不同的途径回收。我们以前发现，Gap 1 p从高尔基体到内体的分选需要通过Rsp 5 p泛素连接酶复合物对Gap 1 p进行泛素化，但氨基酸丰度似乎并没有显着改变聚泛素化Gap 1 p的积累。因此，泛素化的作用似乎是Gap 1 p传递到MVE的信号，而氨基酸丰度似乎控制Gap 1 p从MVE到质膜的循环。
Intracellular sorting of the general amino acid permease (Gap1p) in Saccharomyces cerevisiae depends on availability of amino acids such that at low amino acid concentrations Gap1p is sorted to the plasma membrane, whereas at high concentrations Gap1p is sorted to the vacuole. In a genome-wide screen for mutations that affect Gap1p sorting we identified deletions in a subset of components of the ESCRT (endosomal sorting complex required for transport) complex, which is required for formation of the multivesicular endosome (MVE). Gap1p-GFP is delivered to the vacuolar interior by the MVE pathway in wild-type cells, but when formation of the MVE is blocked by mutation, Gap1p-GFP efficiently cycles from this compartment to the plasma membrane, resulting in unusually high permease activity at the cell surface. Importantly, cycling of Gap1p-GFP to the plasma membrane is blocked by high amino acid concentrations, defining recycling from the endosome as a major step in Gap1p trafficking under physiological control. Mutations in LST4 and LST7 genes, previously identified for their role in Gap1p sorting, similarly block MVE to plasma membrane trafficking of Gap1p. However, mutations in other recycling complexes such as the retromer had no significant effect on the intracellular sorting of Gap1p, suggesting that Gap1p follows a genetically distinct pathway for recycling. We previously found that Gap1p sorting from the Golgi to the endosome requires ubiquitination of Gap1p by an Rsp5p ubiquitin ligase complex, but amino acid abundance does not appear to significantly alter the accumulation of polyubiquitinated Gap1p. Thus the role of ubiquitination appears to be a signal for delivery of Gap1p to the MVE, whereas amino acid abundance appears to control the cycling of Gap1p from the MVE to the plasma membrane.