Bryant N J, Piper R C, Weisman L S, Stevens T H
Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403-1229, USA.
J Cell Biol. 1998 Aug 10;142(3):651-63. doi: 10.1083/jcb.142.3.651.
A large number of trafficking steps occur between the last compartment of the Golgi apparatus (TGN) and the vacuole of the yeast Saccharomyces cerevisiae. To date, two intracellular routes from the TGN to the vacuole have been identified. Carboxypeptidase Y (CPY) travels through a prevacuolar/endosomal compartment (PVC), and subsequently on to the vacuole, while alkaline phosphatase (ALP) bypasses this compartment to reach the same organelle. Proteins resident to the TGN achieve their localization despite a continuous flux of traffic by continually being retrieved from the distal PVC by virtue of an aromatic amino acid-containing sorting motif. In this study we report that a hybrid protein based on ALP and containing this retrieval motif reaches the PVC not by following the CPY sorting pathway, but instead by signal-dependent retrograde transport from the vacuole, an organelle previously thought of as a terminal compartment. In addition, we show that a mutation in VAC7, a gene previously identified as being required for vacuolar inheritance, blocks this trafficking step. Finally we show that Vti1p, a v-SNARE required for the delivery of both CPY and ALP to the vacuole, uses retrograde transport out of the vacuole as part of its normal cellular itinerary.
在酵母酿酒酵母中，从高尔基体反面膜囊（TGN）到液泡之间会发生大量运输步骤。迄今为止，已确定了两条从TGN到液泡的细胞内途径。羧肽酶Y（CPY）会经过前液泡/内体区室（PVC），随后进入液泡，而碱性磷酸酶（ALP）则绕过该区室到达同一细胞器。尽管存在持续的物质运输流，但TGN驻留蛋白通过凭借含芳香族氨基酸的分选基序不断从远端PVC中回收，从而实现其定位。在本研究中，我们报告了一种基于ALP并含有该回收基序的杂合蛋白不是通过CPY分选途径到达PVC，而是通过从液泡进行信号依赖性逆行运输到达，液泡以前被认为是一个终端区室。此外，我们表明，VAC7（一个先前被确定为液泡遗传所必需的基因）中的突变会阻断这一运输步骤。最后，我们表明，Vti1p（一种将CPY和ALP都运输到液泡所必需的v-SNARE）将从液泡的逆行运输作为其正常细胞行程的一部分。
