Protein transport from the endoplasmic reticulum (ER) to Golgi stacks is mediated by the coat protein complex COPII, which is assembled at an ER subdomain called ER exit site (ERES). However, the dynamic relationship between ERESs and Golgi stacks is unknown. Here, we propose a dynamic capture-and-release model of ERESs by Golgi stacks in Arabidopsis thaliana. Using variable-angle epifluorescence microscopy with high-temporal-resolution imaging, COPII-component-bound ERESs were detected as punctate structures with sizes of 300–500 nm. Some punctate ERESs are distributed on ER tubules and sheet rims, whereas others gather around a Golgi stack in an ER-network cavity to form a beaded-ring structure. Free ERESs that wander into an ER cavity are captured by a Golgi stack in a cytoskeleton-independent manner. Then, they are released by the Golgi stack for recycling. The dynamic ERES cycling might contribute to efficient transfer of de novo synthesized cargo proteins from the ER to Golgi stacks.

蛋白质从内质网（ER）到高尔基体的转运是由外壳蛋白复合物COPII介导的，该复合物在称为ER出口位点（ERES）的ER子域组装。但是，ERES和高尔基体堆栈之间的动态关系是未知的。在这里，我们提出了拟南芥中高尔基体动态捕获和释放ERES的模型。。使用具有高角度分辨率成像的可变角度落射荧光显微镜，可检测到COPII成分结合的ERES为点状结构，大小为300-500 nm。一些点状的ERESs分布在ER小管和片状边缘上，而其他的ERESs聚集在ER网络腔中的高尔基体周围，形成串珠状的环状结构。高尔基堆栈以细胞骨架独立的方式捕获游荡到ER腔中的游离ERES。然后，它们被高尔基栈释放以进行回收。动态的ERES循环可能有助于从头合成的货物蛋白从ER高效转移到高尔基体。