Coordination of membrane traffic on the exocytic pathway through rab GEF and rab

描述（由申请人提供）：膜运输对于广泛的基本细胞功能是必需的，例如控制细胞表面受体的可及性、响应胰岛素的葡萄糖转运蛋白的易位、抗原呈递、神经元传递以及上皮细胞极性的建立和维持。因此，膜运输的调节与多种人类疾病直接相关，包括癌症、糖尿病和神经变性。 Rab GTPases 是膜运输的关键调节因子。通过招募和激活一组功能多样的效应子，单个 Rab GTP 酶可以协调膜运输给定阶段内的各种子反应，包括囊泡出芽、递送、束缚和融合。此外，我们的结果表明，相邻的运输阶段也可以通过协调的 rab 调节耦合起来。我们最近定义了一种 rab 鸟嘌呤核苷酸交换因子 (GEF) 级联，其中一个处于 GTP 结合状态的 rab 募集 GEF，沿着胞吐途径激活下一个 rab。我们还有 rab GTP 酶激活蛋白 (GAP) 级联以逆流方式运行的初步证据。此处，下游 rab 招募 GAP，从而使上游 rab 失活。最终效果是 rab 转化，其中给定的膜片开始时用一只 rab 标记，但随着时间的推移，变成用另一只 rab 标记。由于每只兔子都会募集并激活一组不同的效应器，这会导致膜的功能成熟。我们将更详细地探索这两种级联机制，并测试解耦相邻阶段的膜交通的生理后果。我们将测试 Sec4p 效应器在 SNARE 组装中的作用，并探索几个新的假定 Sec4p 效应器的作用。通过这些研究，我们将开始将胞吐途径定义为一个完全协调的系统，而不是孤立的子反应的集合。膜运输是物质在细胞内不同区室之间转移的机制，膜运输的调节与包括癌症、糖尿病和神经变性在内的多种人类疾病直接相关。这项研究探讨了膜运输不同阶段协调调节的分子机制。

DESCRIPTION (provided by applicant): Membrane traffic is required for a broad range of essential cellular functions, such as controlling the accessibility of cell surface receptors, the translocation of glucose transporters in response to insulin, antigen presentation, neuronal transmission and the establishment and maintenance of epithelial cell polarity. Therefore, the regulation of membrane traffic is directly relevant to a broad range of human diseases including cancer, diabetes and neural degeneration. Rab GTPases are key regulators of membrane traffic. By recruiting and activating a functionally diverse set of effectors, a single Rab GTPase can coordinate the various sub- reactions within a given stage of membrane traffic, including vesicle budding, delivery, tethering and fusion. Furthermore, our results indicate that adjacent stages of transport can also be coupled through coordinated rab regulation. We recently defined a rab guanine nucleotide exchange factor (GEF) cascade in which one rab, in its GTP-bound state, recruits the GEF that activates the next rab along the exocytic pathway. We also have preliminary evidence for a rab GTPase activating protein (GAP) cascade operating in a counter current fashion. Here the downstream rab recruits the GAP that inactivates the upstream rab. The net effect is rab conversion in which a given patch of membrane starts out labeled with one rab, but over time becomes labeled with another rab. Since each rab recruits and activates a distinct set of effectors, this leads to a functional maturation of the membrane. We will explore these two cascade mechanisms in further detail and test the physiological consequences of uncoupling adjacent stages of membrane traffic. We will test the role of a Sec4p effector in SNARE assembly and explore the roles of several new putative Sec4p effectors. Through these studies we will begin to define the exocytic pathway as a fully coordinated system, rather than as a collection of isolated sub-reactions. Membrane traffic is the mechanism by which material is transferred between different compartments within the cell and the regulation of membrane traffic is directly relevant to a broad range of human diseases including cancer, diabetes and neural degeneration. This study addresses the molecular mechanisms by which different stages of membrane traffic are coordinately regulated.