Regulation of vesicular membrane traffic by ARF proteins

描述（由申请人提供）：双向囊泡运输需要分泌蛋白质，内化蛋白质，并产生脂质和蛋白质组成的不对称，这是器官发生，细胞生长和分化的基础。膜传输是一个复杂的过程，需要与几乎所有其他细胞功能相结合，包括细胞周期、蛋白质合成、核糖体组装和脂质代谢。虽然这种高度整合过程的完全丧失会对细胞造成不可修复的损害，但膜传输中更微妙的缺陷会影响许多人类疾病，包括阿尔茨海默病、囊性纤维化等。不同蛋白外壳复合物的募集是构建参与膜运输的特定囊泡的第一步。adp核糖基化因子（ARFs）是gtp酶和囊泡交通的调节剂，尽管分子机制仍然不完全清楚。我们讨论了一个模型来解释ARF在同源囊泡出芽反应中的作用，该模型强化了可溶性蛋白向芽的募集是膜运输中囊泡生物发生的起始和/或限速步骤的观点。我们认为，至少需要三个组成部分（ARF，跨膜对接位点和适配器或外壳复合体）才能形成高尔基/TGN发出的囊泡。已经描述了7种依赖arf的包被复合物。由于所有这些接头都是通过ARF招募到高尔基/TGN膜上的，因此我们寻求一种调节机制，可以提供来自共同膜源的囊泡出芽的额外调节水平和特异性。我们进一步提出蛋白磷酸化与ARF激活/失活周期相一致，通过调节GTP结合来调节囊泡的生物发生或特异性。我们建议验证以下假设：MlNTs代表一个新的arf依赖性接头家族，参与高尔基/TGN的囊泡出芽；阿尔茨海默病蛋白（淀粉样前体蛋白；APP）是将ARF-MINT复合物连接到膜上的跨膜蛋白。这为APP在我们细胞中的生理作用提供了一个模型，并可能使我们更好地理解阿尔茨海默病中APP蛋白水解产物分泌所导致的病理生理。

DESCRIPTION (provided by applicant): Bi-directional vesicular traffic is required to secrete proteins, to internalize proteins, and to generate the asymmetries in lipid and protein composition that underlie organellogenesis, cell growth and differentiation. Membrane traffic is a complex process that requires integration with virtually every other cell function, including the cell cycle, protein synthesis, ribosome assembly, and lipid metabolism. While a complete loss of such a highly integrated process would damage cells irreparably, more subtle defects in membrane traffic impact a number of human diseases, including Alzheimer's disease, cystic fibrosis, and others. The recruitment of distinct protein coat complexes is a first step in the construction of specific vesicles involved in membrane traffic. ADP-ribosylation factors (ARFs) are GTPases and regulators of vesicular traffic, though the molecular mechanisms are still only incompletely understood. We discuss a model to explain the role of ARF in a homologous vesicle budding reactions that reinforces the idea that the recruitment of soluble proteins to the bud is the initiating and/or rate-limiting step in vesicle biogenesis in membrane traffic. We propose that a minimum of three components (ARF, a transmembrane docking site, and an adaptor or coat complex) are required for formation of vesicles emanating from the Golgi/TGN. Seven of these ARF-dependent coat complexes have been described. Because all of these adaptors are recruited to Golgi/TGN membranes by ARF we sought a regulatory mechanism that could provide added levels of regulation and specificity of vesicle budding from a common membrane source. We further propose that protein phosphorylation acts in concert with cycles of ARF activation/inactivation through regulated GTP binding to regulate vesicle biogenesis or specificity. We propose to test the hypothesis that MlNTs represent a novel family of ARF-dependent adaptors involved in vesicle budding from the Golgi/TGN and that the Alzheimer's protein (amyloid precursor protein; APP) is the transmembrane protein that docks the ARF-MINT complex to membranes. This provides a model for the physiological role of APP in our cells and is likely to lead to a better understanding of the pathophysiology resulting from the secretion of proteolytic products of APP that occurs in Alzheimer's disease.