Biogenesis of Dense Core Secretory Granules in Tetrahymena

描述(申请人提供)：致密的核心分泌颗粒是负责储存和调节释放多种多肽的囊泡，包括激素、消化酶和多肽神经递质。颗粒将其内容储存在特定细胞类型的细胞质中，并仅在对细胞外刺激的分级反应中释放这些内容。遗传和环境诱导的颗粒功能损害与严重的人类疾病有关，包括糖尿病和发育问题。尽管如此，我们对颗粒合成途径的理解仍然缺乏重要的细节。分泌颗粒的功能要求特定的货运多肽与膜蛋白一起被分选到囊泡中，以促进囊泡的对接和融合。蛋白质分选必须在跨高尔基体网络中进行，但涉及的机制尚不清楚。此外，参与对接和融合的蛋白质可能定位于分泌颗粒膜的特定区域。我们的目的是了解在分选过程中和在完全形成的颗粒中颗粒膜蛋白组织的分子基础。我们将使用纤毛虫嗜热四膜虫来完成这项工作，这是一种基因可操纵的单细胞系统。我们已经在四膜虫分泌颗粒中发现了几种蛋白质，它们是与膜蛋白相互作用的强烈候选成分，我们将结合生物化学和遗传学来剖析它们的功能。

DESCRIPTION (provided by applicant): Dense core secretory granules are vesicles that are responsible for storage and regulated release of a wide variety of polypeptides including hormones, digestive enzymes, and peptide neurotransmitters. Granules store their contents in the cytoplasm of specialized cell types and release these only in graded response to extracellular stimuli. Genetic and environmentally-induced lesions in granule function are connected with serious human diseases, including diabetes and developmental problems. Nonetheless our understanding of the pathway responsible for granule synthesis is still missing important details. The function of secretory granules requires that the specific cargo polypeptides are sorted to vesicles together with membrane proteins that facilitate vesicle docking and fusion. Protein sorting must take place in the trans-Golgi network, but the mechanisms involved are not known. Furthermore, the proteins involved in docking and fusion may be localized to particular regions of the secretory granule membrane. Our aim is to understand the molecular bases for the organization of granule membrane proteins both during sorting and in the fully-formed granule. We will do this using the ciliate Tetrahymena thermophila, a genetically-manipulable single-celled system. We have discovered several proteins within Tetrahymena secretory granules that are strong candidates for components interacting with membrane proteins, and we will use a combination of biochemistry and genetics to dissect their function.