Formation of the Regulated Secretory Pathway: a View from the Cytosol

摘要 释放信号分子的能力，如肽激素，神经肽和许多生长 因子，响应于适当的细胞外刺激，是生理，行为和 发展调节这种分泌的分泌囊泡称为大致密核心囊泡 （LDCV）。它们从高尔基体网络（trans-Golgi network，TGN）中出芽，在那里它们的可溶性货物聚集在一起，形成一个密集的 核心，但细胞机制，特别是产生这些分泌的胞质机制， 囊泡仍然没有被很好地理解。最近发表的研究在C。Elegans已经确定HID-1是一种 胞浆因子参与神经肽分选，但其功能尚不清楚。HID-1是一种外设 与TGN相关的膜蛋白，其表达仅限于神经内分泌细胞，表明 它可能有助于LDCV的生物发生。我们初步的功能丧失实验 通过基因组编辑产生的神经内分泌HID-1敲除（KO）细胞已经证实HID-1确实是 是哺乳动物神经内分泌所必需的。我们现在将1）确定HID-1如何对LDCV做出贡献 2）确定HID-1如何特异性靶向 3）确定调节HID-1与TGN可逆结合的机制，并评估其对TGN的影响。 对LDCV形成的意义。这些研究将提供有关细胞生物学的宝贵信息， 一种新的外周膜蛋白参与膜运输的生物化学 对我们理解神经内分泌的影响。

Abstract The ability to release signaling molecules, such as peptide hormones, neuropeptides, and many growth factors, in response to an appropriate extracellular stimulus, is central to physiology, behavior, and development. The secretory vesicles mediating this regulated secretion are called large dense core vesicles (LDCVs). They bud from the trans-Golgi network (TGN) where their soluble cargo aggregates to form a dense core, but the cellular mechanisms, and in particular, the cytosolic machinery that produces these secretory vesicles are still not well understood. Recent published studies in C. Elegans have identified HID-1 as a cytosolic factor involved in neuropeptide sorting, but its function remains unknown. HID-1 is a peripheral membrane protein associated with the TGN and its expression is restricted to neuroendocrine cells, suggesting that it might contribute to LDCV biogenesis. Our preliminary loss-of-function experiments with rat neuroendocrine HID-1 knockout (KO) cells generated by genome-editing have confirmed that HID-1 is indeed required for mammalian neuroendocrine secretion. We will now 1) determine how HID-1 contributes to LDCV formation using a combination of biochemical and imaging assays, 2) establish how HID-1 targets specifically to the TGN, and 3) identify the mechanism regulating the reversible binding of HID-1 to the TGN and assess its significance for LDCV formation. These studies will provide invaluable information about the cell biology and biochemistry of a novel peripheral membrane protein involved in membrane trafficking with important implications for our understanding of neuroendocrine secretion.