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。这项提议的目标是研究一种类型的受体如何被收集到一个运输囊泡中，并被运送到另一个亚细胞室。具体地说，我们试图了解一种新发现的蛋白质TIP47促进甘露糖6-磷酸受体聚集到运输囊泡中的机制，这些囊泡从内吞体内发芽，并将受体携带到跨高尔基体网络。TIP47识别阳离子依赖的MPR细胞质区域中的苯丙氨酸/色氨酸信号，这对于其从内体中提取并传递到高尔基体是必不可少的。我们在这里描述了旨在调查为什么甘露糖6-磷酸受体被特定的运输机制识别的实验，这取决于它们在细胞内的定位。我们还建议继续分析Rab9 GTPase如何规范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Rab9效应子p40，它优先与活性的GTP结合形式的Rab9结合。P40是一种高度活跃的运输因子。我们提出了旨在确定p40是否在囊泡对接中起作用的实验。这些研究对我们理解生长控制和抗原处理具有重要意义，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.