EDEM accelerates ERAD by preventing aberrant dimer formation of misfolded α1-antitrypsin
EDEM accelerates ERAD by preventing aberrant dimer formation of misfolded α1-antitrypsin
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DOI：
10.1111/j.1365-2443.2006.00957.x
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发表时间：
2006-05-01
期刊：
影响因子：
2.1
通讯作者：
Nagata, K
中科院分区：
文献类型：
--
作者：
Hosokawa, N;Wada, I;Nagata, K
错误折叠的糖蛋白在从内质网（ER）逆转位后通过称为ERAD（ER相关降解）的机制降解。该机制在ER质量控制中起着重要作用。我们以前报道，ER膜蛋白，EDEM，加速ERAD的错误折叠的α 1-抗胰蛋白酶变体，空（香港）（NHK），这表明EDEM可能作为一个受体的末端错误折叠的糖蛋白。在这项研究中，我们构建了几个基因操作的细胞系来验证这一假设。EDEM的表达没有改变正确折叠的分子的分泌速率，并且野生型α 1-抗胰蛋白酶在ER中的强制保留没有导致其与EDEM的关联，这表明EDEM可能起分子伴侣的作用。为了检验这种可能性，我们分析了EDEM过表达对NHK结构的影响，发现EDEM的过表达选择性地阻止了共价NHK二聚体的积累。NHK与其他两种ER膜蛋白（钙连接蛋白和H+/K+-ATP酶（β亚基））的共表达不会抑制NHK二聚体的形成或加速NHK ERAD。这些结果表明，EDEM可能通过抑制聚集，使不稳定的错误折叠的蛋白质可以容纳ERAD的错位，NHK的逆转位能力。
Misfolded glycoproteins are degraded by a mechanism known as ERAD (ER-associated degradation) after retrotranslocation out of the endoplasmic reticulum (ER). This mechanism plays an important role in ER quality control. We previously reported that an ER membrane protein, EDEM, accelerates ERAD of a misfolded alpha 1-antitrypsin variant, null (Hong Kong) (NHK), suggesting that EDEM may function as an acceptor of terminally misfolded glycoproteins. In this study, we constructed several genetically manipulated cell lines to test this hypothesis. EDEM expression did not alter the secretion rate of properly folded molecules and the forced retention of wild-type alpha 1-antitrypsin in the ER did not cause its association with EDEM, suggesting that EDEM may function as a molecular chaperone. To examine this possibility, we analyzed the effect of EDEM over-expression on the structure of NHK, and found that the accumulation of covalent NHK dimers was selectively prevented by the over-expression of EDEM. Co-expression of NHK with two other ER membrane proteins, calnexin and H+/K+-ATPase (beta subunit), did not inhibit NHK dimer formation or accelerate NHK ERAD. These results indicate that EDEM may maintain the retrotranslocation competence of NHK by inhibiting aggregation so that unstable misfolded proteins can be accommodated by the dislocon for ERAD.