Regulatory mechanisms of clathrin dependant traffic at the TGN and endosomes

描述（由申请人提供）：细胞行为的差异对正常的人类发育以及损伤、病原体和突变如何导致功能障碍至关重要。差异细胞行为的许多方面可归因于蛋白质定位的差异，例如粘附分子减少或酶分泌增加。跨高尔基体网络（trans-Golgi network，TGN）和内体之间的网格蛋白依赖性运输在对细胞迁移、细胞信号传导和存活重要的蛋白质的定位中起重要作用。该提案中的实验符合一个长期目标，即了解发育程序、突变和细胞信号传导如何作用于交通机制以导致细胞行为差异。这是第一步，将了解导致TGN和内体有效和准确运输的分子机制。目前还不清楚网格蛋白和它的许多衔接蛋白和辅助蛋白联合收割机如何结合，以提供交通中涉及的复杂步骤所需的所有活动。这些步骤包括选择和浓缩货物，在体内产生和靶向运输载体。先前对作用于TGN和内体的相互作用网格蛋白衔接子网络的鉴定为理解网格蛋白依赖性交通的分子机制开辟了新途径。在这个提议中，将研究导致膜交通保真度的分子机制和调节酵母膜交通的信号通路。在aim 1中，将测试关于网格蛋白和衔接子如何确保外套在正确的膜上组装，事件以正确的顺序发生以及正确的蛋白质被运输的特定假设。待测试的假设是1）协同结合和2）在紧密堆积的网格蛋白外壳中对空间的竞争决定衔接子何时起作用。一个综合的方法来测试这些假设将使用体外生物化学，细胞分级分离，膜交通和活细胞显微镜的衔接蛋白的特定突变的测定。在目标2中，将研究低营养条件下网格蛋白衔接子的新鉴定的调节。待检验的假设是：1）低营养素抑制膜运输，2）抑制作用在衔接子修饰水平，3）保守的信号传导途径与其他细胞对低营养素的反应协调运输。

DESCRIPTION (provided by applicant): Differences in cellular behavior are central to normal human development and how injury, pathogens and mutations cause dysfunction. Many aspects of differential cellular behavior can be attributed to differences in protein localization such as reduced adhesion molecules or increased secretion of enzymes. Clathrin dependent traffic between the trans-Golgi network (TGN) and endosomes plays an important role in localization of proteins important for cell migration, cell signaling and survival. The experiments in this proposal fit into a long term goal to understand how developmental programs, mutations and cell signaling act on the traffic machinery to cause differential cellular behavior. This is the first step will be understand the molecular mechanisms leading to efficient and accurate traffic at the TGN and endosomes. It is still unclear how clathrin and its many adaptor and accessory proteins combine to provide all activities required for the complicated steps involved in traffic. These steps include selecting and concentrating cargo, generating and targeting a transport carrier in vivo. Previous identification of a network of interacting clathrin adaptors that act at TGN and endosomes has opened new avenues for understanding the molecular mechanism of clathrin dependent traffic. In this proposal, molecular mechanisms leading to fidelity in membrane traffic and a signaling pathway regulating membrane traffic in yeast will be examined. In aim1, specific hypotheses will be tested about how clathrin and adaptors ensure coats assemble at the correct membrane, that events occur in the correct order and the correct proteins are transported. Hypotheses to be tested are that 1) cooperative binding and 2) competition for space in the tightly packed clathrin coat determine when an adaptor functions. A combined approach to test these hypotheses will use in vitro biochemistry, cell fractionation, assays of membrane traffic and live-cell microscopy of specific mutations in adaptor proteins. In Aim2, a newly identified regulation of clathrin adaptors in low nutrient conditions will be investigated. Hypotheses to be tested are that 1) low nutrients inhibits membrane traffic, 2) inhibition acts at the level of adaptor modification and 3) conserved signaling pathways coordinate traffic with other cellular responses to low nutrients.