PDF(Pubmed)
Abstract：
Organelles of the endomembrane system contain Rab GTPases as identity markers. Their localization is determined by guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs). It remains largely unclear how these regulators are specifically targeted to organelles and how their activity is regulated. Here, we focus on the GAP Gyp7, which acts on the Rab7-like Ypt7 protein in yeast, and surprisingly observe the protein exclusively in puncta proximal to the vacuole. Mistargeting of Gyp7 to the vacuole strongly affects vacuole morphology, suggesting that endosomal localization is needed for function. In agreement, efficient endolysosomal transport requires Gyp7. In vitro assays reveal that Gyp7 requires a distinct lipid environment for membrane binding and activity. Overexpression of Gyp7 concentrates Ypt7 in late endosomes and results in resistance to rapamycin, an inhibitor of the target of rapamycin complex 1 (TORC1), suggesting that these late endosomes are signaling endosomes. We postulate that Gyp7 is part of regulatory machinery involved in late endosome function.
摘要：
内膜系统的细胞器含有RabGTP酶作为身份标记。它们的定位由鸟嘌呤核苷酸交换因子（GEF）和GTP酶激活蛋白（GAP）决定。目前还不清楚这些调节因子是如何专门针对细胞器的，以及它们的活动是如何被调节的。这里,我们专注于GAPGyp7，它作用于酵母中的Rab7样Ypt7蛋白，令人惊讶的是，该蛋白质仅在液泡附近的斑点中观察到。Gyp7对液泡的误定强烈影响液泡形态，提示功能需要内体定位。在协议中,有效的内溶酶体运输需要Gyp7。体外测定表明Gyp7需要独特的脂质环境来进行膜结合和活性。Gyp7的过表达使Ypt7在晚期内体中浓缩，并导致对雷帕霉素的抗性，雷帕霉素复合物1（TORC1）的靶抑制剂，这表明这些晚期内体是信号内体。我们假设Gyp7是参与晚期内体功能的调节机制的一部分。
