Cytoplasm to vacuole trafficking of aminopeptidase I requires a t-SNARE-Sec1p complex composed of Tlg2p and Vps45p
Cytoplasm to vacuole trafficking of aminopeptidase I requires a t-SNARE-Sec1p complex composed of Tlg2p and Vps45p
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DOI：
10.1093/emboj/18.21.6005
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发表时间：
1999-11-01
期刊：
影响因子：
11.4
通讯作者：
Emr, SD
中科院分区：
文献类型：
--
作者：
Abeliovich, H;Darsow, T;Emr, SD
氨肽酶I（API）通过组成型非经典囊泡转运机制（细胞质至空泡靶向（Cvt）途径）输入到酵母空泡/溶酶体中。新合成的前体API被隔离在双膜细胞质Cvt囊泡中。Cvt囊泡与液泡融合，将含有前API的单膜Cvt体释放到液泡腔中，并且当Cvt体降解时发生API的成熟，释放成熟的API。在饥饿条件下，API通过巨自噬转运到液泡，巨自噬是一种与Cvt途径具有许多相似性的诱导型非选择性机制。在这里，我们表明，Tlg 2 p，t-SNARE蛋白的突触融合蛋白家族的成员，和Vps 45 p，Sec 1 p同源物，所需的组成型CVT途径，但不是在诱导型大自噬，分馏和蛋白酶保护实验表明，Tlg 2 p是需要之前或在步骤中的API隔离到CVT囊泡。因此，Cvt途径的早期Vps 45-Tlg 2 p依赖性步骤似乎与宏观自噬中的可比较阶段在机制上不同，Vps 45 p与Tlg 2 p和Pep 12 p t-SNARES两者相关联，但API成熟在pep 12（ts）突变体中不被阻断，表明Vps 45 p在不同的运输步骤独立地调节多个t-SNARES的功能。
Aminopeptidase I (API) is imported into the yeast vacuole/lysosome by a constitutive non-classical vesicular transport mechanism, the cytoplasm to vacuole targeting (Cvt) pathway. Newly synthesized precursor API is sequestered in double-membrane cytoplasmic Cvt vesicles. The Cvt vesicles fuse with the vacuole, releasing single-membrane Cvt bodies containing pro-API into the vacuolar lumen, and maturation of API occurs when the Cvt body is degraded, releasing mature API, Under starvation conditions, API is transported to the vacuole by macroautophagy, an inducible, nonselective mechanism that shares many similarities with the Cvt pathway. Here we show that Tlg2p, a member of the syntaxin family of t-SNARE proteins, and Vps45p, a Sec1p homologue, are required in the constitutive Cvt pathway, but not in inducible macroautophagy, Fractionation and protease protection experiments indicate that Tlg2p is required prior to or at the step of API segregation into the Cvt vesicle. Thus, the early Vps45-Tlg2p-dependent step of the Cvt pathway appears to be mechanistically distinct from the comparable stage in macroautophagy, Vps45p associates with both the Tlg2p and Pep12p t-SNAREs, but API maturation is not blocked in a pep12(ts) mutant, indicating that Vps45p independently regulates the function of multiple t-SNARES at distinct trafficking steps.