The yeast adaptor protein complex, AP-3, is essential for the efficient delivery of alkaline phosphatase by the alternate pathway to the vacuole.
The yeast adaptor protein complex, AP-3, is essential for the efficient delivery of alkaline phosphatase by the alternate pathway to the vacuole.
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酵母衔接蛋白复合物AP-3对于通过液泡的替代途径有效地递送碱性磷酸酶至关重要。
DOI：
10.1083/jcb.139.7.1761
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发表时间：
1997-12-29
期刊：
影响因子：
--
通讯作者：
Lemmon SK
中科院分区：
文献类型：
--
作者：
Stepp JD;Huang K;Lemmon SK
最近在酵母和动物中描述了一种新的网格蛋白衔接子样复合物，衔接子蛋白（AP）-3。为了深入了解酵母AP-3的作用，设计了一种遗传策略来分离在缺乏由APM 3编码的AP-3 μ链的情况下所需的基因产物。通过该合成致死筛选鉴定的一个基因是VPS 45。Vps途径定义了包括羧肽酶Y在内的几种蛋白质从晚期高尔基体到液泡的路线。然而，液泡碱性磷酸酶（ALP）是通过一个替代的细胞内途径运输。这表明apm 3-Δ vps 45合成表型可能是由交替途径和Vps途径的阻断引起的。在这里，我们证明了AP-3复合物功能的丧失导致ALP的加工减慢和分选错误。ALP不再通过免疫荧光定位于液泡膜，而是在整个细胞的小点状结构中发现。这种模式与高尔基体标记Kex 2 p不同，Kex 2 p在AP-3突变体中不受影响。我们还表明，在apm 3-Δ突变体中，一些ALP通过转向Vps途径被递送到液泡。E类vps突变体积累了一个夸张的prevacuolar室含有膜蛋白的方式液泡或注定回收到高尔基体。令人惊讶的是，在AP-3 E类vps双突变体中，这些蛋白质重新出现在液泡上。我们建议，一些AP-3依赖的货物蛋白，调节后期步骤高尔基体液泡运输转移到VPS通路允许完成转移到液泡中的E类VPS突变体。
A novel clathrin adaptor-like complex, adaptor protein (AP)-3, has recently been described in yeast and in animals. To gain insight into the role of yeast AP-3, a genetic strategy was devised to isolate gene products that are required in the absence of the AP-3 μ chain encoded by APM3. One gene identified by this synthetic lethal screen was VPS45. The Vps pathway defines the route that several proteins, including carboxypeptidase Y, take from the late Golgi to the vacuole. However, vacuolar alkaline phosphatase (ALP) is transported via an alternate, intracellular route. This suggested that the apm3-Δ vps45 synthetic phenotype could be caused by a block in both the alternate and the Vps pathways. Here we demonstrate that loss of function of the AP-3 complex results in slowed processing and missorting of ALP. ALP is no longer localized to the vacuole membrane by immunofluorescence, but is found in small punctate structures throughout the cell. This pattern is distinct from the Golgi marker Kex2p, which is unaffected in AP-3 mutants. We also show that in the apm3-Δ mutant some ALP is delivered to the vacuole by diversion into the Vps pathway. Class E vps mutants accumulate an exaggerated prevacuolar compartment containing membrane proteins on their way to the vacuole or destined for recycling to the Golgi. Surprisingly, in AP-3 class E vps double mutants these proteins reappear on the vacuole. We suggest that some AP-3–dependent cargo proteins that regulate late steps in Golgi to vacuole transport are diverted into the Vps pathway allowing completion of transfer to the vacuole in the class E vps mutant.