Allen R D, Fok A K
Pacific Biomedical Research Center, Department of Microbiology, University of Hawaii, Honolulu 96822.
J Struct Biol. 1993 May-Jun;110(3):215-26. doi: 10.1006/jsbi.1993.1024.
Understanding vesicle trafficking to and through the Golgi stack has been greatly elucidated recently, but the question of what holds the endoplasmic reticulum (ER) and Golgi stack together in many cell types and an explanation of anterograde trafficking in the ER-Golgi transitional zone have not yet been adequately explained. We have studied these problems using both the thin sectioning and the quick-freeze deep-etch (QF-DE) technique on Paramecium cells harvested at different culture ages. Although the Golgi apparatus of Paramecium is made up of many sets of more reduced stacks of cisternae than those of many mammalian cells, the stacks in Paramecium always bear a close relationship to a transitional element of the ER from which non-clathrin-coated transition vesicles arise. In QF-DE replicas two networks of filaments are clearly shown; one is in this ER-Golgi transition zone and the other is on the trans side of the Golgi stack. The network associated with the trans-Golgi region links a number of vesicular elements. The network in the transition zone spans the distance between the ER and the cis-cisterna of the Golgi stack and has branches extending to the coats of the enmeshed nonclathrin-coated transition vesicles. These coats consist of a layer of 11-nm globular elements (the same size as coatomer complexes) which surround the 40-nm-diameter transition vesicles. We conclude that the filamentous network holds the ER and Golgi stack together and prevents the dispersal of the transition vesicles away from this zone. This network may also delineate and stabilize the transitional element within the ER and, finally, help organize anterograde transition vesicle trafficking in this ER-Golgi transition zone.
近年来，人们对囊泡向高尔基体堆叠的运输以及通过高尔基体堆叠的运输有了更深入的了解，但在许多细胞类型中，内质网（ER）和高尔基体堆叠是如何结合在一起的问题，以及内质网-高尔基体过渡区顺向运输的解释尚未得到充分说明。我们使用薄切片和快速冷冻深蚀刻（QF-DE）技术，对不同培养年龄收获的草履虫细胞进行了研究。尽管草履虫的高尔基体由多组比许多哺乳动物细胞的扁平囊堆叠更为简化的结构组成，但草履虫中的扁平囊总是与内质网的一个过渡元件密切相关，非网格蛋白包被的过渡囊泡由此产生。在QF-DE复制品中，可以清楚地看到两个丝状网络；一个位于这个内质网-高尔基体过渡区，另一个位于高尔基体堆叠的反面。与反式高尔基体区域相关的网络连接着许多囊泡元件。过渡区的网络跨越内质网和高尔基体堆叠顺式扁平囊之间的距离，并具有延伸到陷入其中的非网格蛋白包被过渡囊泡衣被的分支。这些衣被由一层11纳米的球状元件（与COPII复合体大小相同）组成，围绕着直径40纳米的过渡囊泡。我们得出结论，丝状网络将内质网和高尔基体堆叠结合在一起，并防止过渡囊泡从该区域分散。这个网络还可能勾勒并稳定内质网内的过渡元件，最终帮助组织内质网-高尔基体过渡区内的顺向过渡囊泡运输。
