Quality control in the secretory pathway: retention of a misfolded viral membrane glycoprotein involves cycling between the ER, intermediate compartment, and Golgi apparatus.
Quality control in the secretory pathway: retention of a misfolded viral membrane glycoprotein involves cycling between the ER, intermediate compartment, and Golgi apparatus.
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DOI：
10.1083/jcb.126.1.41
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发表时间：
1994-07
影响因子：
7.8
通讯作者：
Helenius, A
中科院分区：
文献类型：
--
作者：
Hammond, C;Helenius, A
内质网中合成的蛋白质通常只有在达到完全折叠和组装构象时才会被转运到高尔基复合体及其以外。为了分析错误折叠蛋白的选择性保留如何发挥作用，我们监测了具有温度依赖性折叠缺陷的膜糖蛋白（tsO45 水泡性口炎病毒的 G 蛋白）的长期命运。我们使用间接免疫荧光、免疫电子显微镜和新型 Nycodenz 梯度离心程序来分离内质网、中间室和高尔基复合体。我们还采用了折叠和再循环抑制剂二硫苏糖醇和 AIF4-，以及与钙联蛋白抗体的免疫共沉淀。结果表明，错误折叠的G蛋白并不单独保留在ER中；它可以移动到中间室和顺式高尔基体网络，但然后再循环回内质网。在 ER 中，它与钙联蛋白和 BiP/GRP78 相关。在这两个伴侣中，似乎只有 BiP/GRP78 伴随它通过回收回路。因此，这种错误折叠的糖蛋白的保留是多种机制的结果，包括内质网中钙联蛋白的结合以及从中间室和顺式高尔基体网络的选择性回收。
Proteins synthesized in the ER are generally transported to the Golgi complex and beyond only when they have reached a fully folded and assembled conformation. To analyze how the selective retention of misfolded proteins works, we monitored the long-term fate of a membrane glycoprotein with a temperature-dependent folding defect, the G protein of tsO45 vesicular stomatitis virus. We used indirect immunofluorescence, immunoelectron microscopy, and a novel Nycodenz gradient centrifugation procedure for separating the ER, the intermediate compartment, and the Golgi complex. We also employed the folding and recycling inhibitors dithiothreitol and AIF4-, and coimmunoprecipitation with calnexin antibodies. The results showed that the misfolded G protein is not retained in the ER alone; it can move to the intermediate compartment and to the cis-Golgi network but is then recycled back to the ER. In the ER it is associated with calnexin and BiP/GRP78. Of these two chaperones, only BiP/GRP78 seems to accompany it through the recycling circuit. Thus, the retention of this misfolded glycoprotein is the result of multiple mechanisms including calnexin binding in the ER and selective retrieval from the intermediate compartment and the cis-Golgi network.