Department of Cellular and Molecular Physiology, Penn State University College of Medicine, Hershey, Pennsylvania 17033, USA.
J Biol Chem. 2010 Jul 23;285(30):23359-70. doi: 10.1074/jbc.M109.075143. Epub 2010 May 10.
The key gluconeogenic enzyme fructose-1,6-bisphosphatase (FBPase) is induced when Saccharomyces cerevisiae are starved of glucose. However, when glucose is added to cells that have been starved for 3 days, FBPase is degraded in the vacuole. FBPase is first imported to Vid (vacuole import and degradation) vesicles, and these vesicles then merge with the endocytic pathway. In this report we show that two additional gluconeogenic enzymes, isocitrate lyase and phosphoenolpyruvate carboxykinase, were also degraded in the vacuole via the Vid pathway. These new cargo proteins and FBPase interacted with the TORC1 complex during glucose starvation. However, Tor1p was dissociated from FBPase after the addition of glucose. FBPase degradation was inhibited in cells overexpressing TOR1, suggesting that excessive Tor1p is inhibitory. Both Tco89p and Tor1p were found in endosomes coming from the plasma membrane as well as in retrograde vesicles forming from the vacuole membrane. When TORC1 was inactivated by rapamycin, FBPase degradation was inhibited. We suggest that TORC1 interacts with multiple cargo proteins destined for the Vid pathway and plays an important role in the degradation of FBPase in the vacuole.
当酿酒酵母缺乏葡萄糖时，关键的糖异生酶果糖-1,6-二磷酸酶（FBPase）会被诱导。然而，当已经饥饿 3 天的细胞中添加葡萄糖时，FBPase 在液泡中被降解。FBPase 首先被导入 Vid（液泡导入和降解）小泡，然后这些小泡与内吞途径融合。在本报告中，我们表明另外两种糖异生酶，异柠檬酸裂解酶和磷酸烯醇丙酮酸羧激酶，也通过 Vid 途径在液泡中降解。这些新的货物蛋白与葡萄糖饥饿期间的 TORC1 复合物相互作用。然而，Tor1p 在添加葡萄糖后与 FBPase 解离。在过表达 TOR1 的细胞中，FBPase 降解被抑制，这表明过多的 Tor1p 具有抑制作用。Tco89p 和 Tor1p 都存在于来自质膜的内体以及从液泡膜形成的逆行小泡中。当 TORC1 被雷帕霉素失活时，FBPase 降解被抑制。我们认为 TORC1 与多个货物蛋白相互作用，这些蛋白注定要通过 Vid 途径，并在 FBPase 在液泡中的降解中发挥重要作用。
