The organization of endoplasmic reticulum export complexes.
The organization of endoplasmic reticulum export complexes.
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DOI：
10.1083/jcb.135.1.19
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发表时间：
1996-10
期刊：
影响因子：
--
通讯作者：
Balch WE
中科院分区：
文献类型：
--
作者：
Bannykh SI;Rowe T;Balch WE
ER的货物出口是通过形成60-70 nm的包裹COPII的囊泡载体进行的。我们应用连续薄层切片法和体视学方法来定量描述体内和体外内质网输出部位的三维组织结构。我们发现，内质网芽在体内是非随机分布的，集中在我们称之为出口复合体的区域。出口复合体的基本组织结构可以划分为单个ER池上含有COPII的活性萌发区，该区域与远距离连接的ER池上的萌发区相邻。这些萌发的病灶围绕并面对形态上独立的囊状小管单元的中心簇，这些囊管单元含有参与逆行运输的COPI涂层。这些出口复合体内的小泡含有浓缩的货物分子。出口复合体中泡状-管状集群的结构在使用快速冷冻、深蚀刻方法产生的复制品中尤其引人注目，以首次可视化其三维组织和货物组成。我们的结论是，通过招募COPII从ER萌芽仅限于高度专业化的出口复合体，这些复合体在拓扑上限制向区域焦点的顺行运输，以促进COPI与逆行回收的有效耦合。
Export of cargo from the ER occurs through the formation of 60-70nm COPII-coated vesicular carriers. We have applied serial-thin sectioning and stereology to quantitatively characterize the three-dimensional organization of ER export sites in vivo and in vitro. We find that ER buds in vivo are nonrandomly distributed, being concentrated in regional foci we refer to as export complexes. The basic organization of an export complex can be divided into an active COPII-containing budding zone on a single ER cisterna, which is adjacent to budding zones found on distantly connected ER cisternae. These budding foci surround and face a central cluster of morphologically independent vesicular-tubular elements that contain COPI coats involved in retrograde transport. Vesicles within these export complexes contain concentrated cargo molecules. The structure of vesicular-tubular clusters in export complexes is particularly striking in replicas generated using a quick-freeze, deep-etch approach to visualize for the first time their three-dimensional organization and cargo composition. We conclude that budding from the ER through recruitment of COPII is confined to highly specialized export complexes that topologically restrict anterograde transport to regional foci to facilitate efficient coupling to retrograde recycling by COPI.