Quality control of transmembrane domain assembly in the tetraspanin CD82
Quality control of transmembrane domain assembly in the tetraspanin CD82
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DOI：
10.1093/emboj/20.10.2443
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发表时间：
2001-05-15
期刊：
影响因子：
11.4
通讯作者：
Cresswell, P
中科院分区：
文献类型：
--
作者：
Cannon, KS;Cresswell, P
错误折叠的蛋白质在内质网（ER）中的滞留是质量控制的主要机制。为了发现质量控制是否可以监测疏水性ER膜内的组装，我们表征了四跨膜蛋白糖蛋白CD 82的折叠和转运。缺失一个或多个跨膜区段的CD 82的截短形式保留在ER中。缺失第一个跨膜区段的构建体（TM 2-4）保留在ER中，即使其面向ER腔的细胞外结构域，已经折叠成原生结构。通过共表达缺失片段（TM 1）作为单独的多肽来恢复向细胞表面的转运。在离开ER之前，CD 82与膜结合的伴侣钙连接蛋白瞬时缔合，但不与其可溶性同源物钙网蛋白缔合。TM 2-4与钙连接蛋白的相互作用持续时间较长，而TM 1的共表达则部分逆转了这种相互作用。这些发现建立了一个简单的研究跨膜结构域组装的系统，表明ER质量控制可以直接监测脂质双层内的组装，并提示钙连接蛋白可能在这一过程中发挥作用。
Retention of misfolded proteins in the endoplasmic reticulum (ER) is a primary mechanism of quality control. To discover whether quality control can monitor assembly inside the hydrophobic ER membrane, we characterized the folding and transport of the tetraspanin glycoprotein CD82, Truncated forms of CD82 that are missing one or more transmembrane segments remain in the ER, A construct (TM 2-4) that is missing the first transmembrane segment remains in the ER, even though its extracellular domain, which is facing the ER lumen, has folded to the native structure. Transport to the cell surface is restored by co-expressing the missing segment (TM 1) as a separate polypeptide, Prior to leaving the ER, CD82 transiently associates with the membrane-bound chaperone calnexin but not with its soluble homolog calreticulin. TM 2-4, in contrast, remains in a prolonged interaction with calnexin that is partially reversed by co-expressing TM 1, These findings establish a simple system to study transmembrane domain assembly, show that ER quality control can directly monitor assembly inside the lipid bilayer and suggest that calnexin may play a role in this process.