INTRACELLULAR TRANSPORT--THE MANNOSE-PHOSPHATE RECEPTOR

这项研究的长期目标是了解哺乳动物细胞中受体运输的分子基础。 这项计划的目的是研究一种受体是如何被收集到一个运输囊泡和交付到另一个亚细胞区室。 具体来说，我们试图了解的机制，一个新发现的蛋白质，TIP 47，促进收集甘露糖6-磷酸受体进入运输囊泡，芽从内涵体和携带的受体的transGolgi网络。 TIP 47识别阳离子依赖性MPR的胞质结构域中的苯丙氨酸/色氨酸信号，该信号对于其从内体的检索和递送到高尔基体是必需的。 我们在这里描述的实验，旨在调查为什么甘露糖6-磷酸受体被识别的特定贩运机制取决于他们的细胞内定位。 我们还建议继续分析Rab 9 GTIPs如何调节MPR贩运。 Rab GTP酶被认为在囊泡对接中起作用。 我们发现了一种新的Rab 9效应子p40，它优先结合Rab 9的活性GTP结合形式。 p40是一种高活性的转运因子。 我们提出的实验设计，以确定是否p40的功能在囊泡对接。 这些研究对我们理解生长控制和抗原加工具有重要意义，并将提供有关哺乳动物细胞中受体运输机制的基本信息。

The long term goal of this research is to understand the molecular basis of receptor trafficking in mammalian cells. The goal of this proposal is to study how one type of receptor is collected into a transport vesicle and delivered to another subcellular compartment. Specifically, we seek to understand the mechanism by which a newly discovered protein, TIP47, facilitates the collection of mannose 6-phosphate receptors into transport vesicles that bud from endosomes and carry the receptors to the trans Golgi network. TIP47 recognizes a phenylalanine/tryptophan signal in the cytoplasmic domain of the cation-dependent MPR that is essential for its retrieval from endosomes and delivery to the Golgi. We describe here experiments designed to investigate why mannose 6-phosphate receptors are recognized by a specific trafficking machinery depending upon their intracellular localization. We also propose to continue our analysis of the Rab9 GTPase in terms of how it regulates MPR trafficking. Rab GTPases are believed to function in vesicle docking. We have discovered a novel Rab9 effector, p40, which binds preferentially to the active, GTP-bound form of Rab9. p40 is a highly active transport factor. We propose experiments designed to determine if p40 functions in vesicle docking. These studies have important implications for our understanding of growth control and antigen processing, and will provide fundamental information regarding the mechanism of receptor trafficking in mammalian cells.