基于高分辨率成像技术分析果蝇内质网出口-高尔基体间蛋白运输途径的空间结构

通常认为，在分泌性蛋白从内质网到细胞外间隙的过程中， COPII囊泡负责从内质网出口（ERES）运输蛋白到高尔基体（Golgi）。但这个经典运输方式无法解释大蛋白分泌。因为COPII囊泡是“笼子”，直径有限，而细胞内很多分泌性大蛋白超出囊泡大小。目前，这个小载体如何运输大货物的问题没有确切答案。我们以前设想了果蝇蛋白从ERES到Golgi的运输途径，即ERES和Golgi通过蛋白相互作用连接成管状通道结构进行蛋白运输，因此大分子不受COPII囊泡大小限制。而我们最近确实捕捉到ERES和Golgi的类连接状态。本项目拟采用高分辨率成像技术分析ERES-Golgi间蛋白运输途径的空间结构。我们将探索ERES-Golgi间各结构的三维相互位置，展示ERES-Golgi间结构的空间形态，并识别影响此结构的蛋白。本课题将推进蛋白分泌途径的研究，对理解和治疗蛋白分泌不足引起的疾病有广泛意义。

In general, during the whole process of protein secretion from endoplasmic reticulum (ER) to extracellular space, COPII vesicles transport proteins from ER exit site (ERES) to Golgi. However, this conventional transportation pathway cannot fit in the ERES-to-Golgi secretion of large proteins. The COPII vesicle is a size-limited cage, while many large proteins in the cell exceed the size of COPII vesicle and still can be effectively secreted. The raised question that how a small vesicle transports a large cargo is not certainly answered yet. Previously we proposed a model about the protein secretion pathway from ERES to Golgi in Drosophila, in which ERES and Golgi connect together through interactions among proteins of ERES, COPII vesicle, and cis-Golgi, and form a tubular organization. Thus, proteins will be transported directly from ERES to Golgi through the “tube”, and not be restricted by the size of COPII vesicles. Indeed, recently we caught connection-like status between ERES and Golgi through a transmission electron microscopy. This project intends to apply high-resolution technologies to analyze the spatial organization of ERES-Golgi trafficking. We will explore the mutual localization among different configurations involved in ERES-Golgi trafficking, exhibit the morphology of the spatial organization of ERES-Golgi, and identify proteins that affect the spatial organization of ERES-Golgi. I expect to obtain fundamental insights both specific into collagen secretion and general about protein secretion. And insights obtained in the course of this project may have broad implications for the understanding and treatment of diseases related with deficits in protein secretion.