Enhancement of endoplasmic reticulum (ER) degradation of misfolded null Hong Kong α1-antitrypsin by human ER mannosidase I
Enhancement of endoplasmic reticulum (ER) degradation of misfolded null Hong Kong α1-antitrypsin by human ER mannosidase I
复制标题
DOI：
10.1074/jbc.m303395200
复制
发表时间：
2003-07-11
影响因子：
4.8
通讯作者：
Nagata, K
中科院分区：
文献类型：
--
作者：
Hosokawa, N;Tremblay, LO;Nagata, K
在内质网（ER）中合成的错误折叠的糖蛋白被细胞质蛋白酶体降解，这种机制称为ERAD（ER相关降解）。在本研究中，我们证明，ERAD的错误折叠的遗传变异-空香港α（1）-抗胰蛋白酶增强的ER加工α 1，2-甘露糖苷酶（ER ManI）在HEK 293细胞中的过表达，表明ER ManI在糖蛋白质量控制的重要性。我们先前表明，EDEM，一种无酶活性的甘露糖苷酶同系物，与错误折叠的α 1-抗胰蛋白酶相互作用并加速其降解（Hosokawa，N.，和田岛Hasegawa，K.，Yorihuzi，T.，特伦布莱湖O.，Herscovics，A.，和Nagata，K.（2001）EMBO Rep.2，415 - 422）。在此，我们证明了ER ManI和EDEM对错误折叠的α（1）-抗胰蛋白酶的ERAD的联合作用。我们还表明，错误折叠的α（1）-抗胰蛋白酶NHK含有标记的葡萄糖（1）曼（9）GlcNAc和曼（5 - 9）GlcNAc释放的内切-β-N-乙酰氨基葡萄糖苷酶H在脉冲追逐实验与[2-H-3]甘露糖。ER ManI的过表达大大增加Man（8）GlcNAc的形成，诱导Glc（1）Man（8）GlcNAc的形成，并增加对Man（5 - 7）GlcNAc的修剪。我们提出了一个模型，其中错误折叠的糖蛋白与ER ManI和EDEM相互作用，然后被下游ERAD组件识别。与错误折叠糖蛋白相关的寡糖的详细表征提出了一种可能性，即触发ERAD的碳水化合物识别决定簇可能不限于Man（8）GlcNAc（2）异构体B，如先前研究所示。
Misfolded glycoproteins synthesized in the endoplasmic reticulum (ER) are degraded by cytoplasmic proteasomes, a mechanism known as ERAD (ER-associated degradation). In the present study, we demonstrate that ERAD of the misfolded genetic variant-null Hong Kong alpha(1)-antitrypsin is enhanced by overexpression of the ER processing alpha1,2-mannosidase (ER ManI) in HEK 293 cells, indicating the importance of ER ManI in glycoprotein quality control. We showed previously that EDEM, an enzymatically inactive mannosidase homolog, interacts with misfolded alpha1-antitrypsin and accelerates its degradation (Hosokawa, N., Wada, I., Hasegawa, K., Yorihuzi, T., Tremblay, L. O., Herscovics, A., and Nagata, K. (2001) EMBO Rep. 2, 415-422). Herein we demonstrate a combined effect of ER ManI and EDEM on ERAD of misfolded alpha(1)-antitrypsin. We also show that misfolded alpha(1)-antitrypsin NHK contains labeled Glc(1)Man(9)GlcNAc and Man(5-9)GlcNAc released by endo-beta-N-acetylglucosaminidase H in pulse-chase experiments with [2-H-3] mannose. Overexpression of ER ManI greatly increases the formation of Man(8)GlcNAc, induces the formation of Glc(1)Man(8)GlcNAc and increases trimming to Man(5-7)GlcNAc. We propose a model whereby the misfolded glycoprotein interacts with ER ManI and with EDEM, before being recognized by downstream ERAD components. This detailed characterization of oligosaccharides associated with a misfolded glycoprotein raises the possibility that the carbohydrate recognition determinant triggering ERAD may not be restricted to Man(8)GlcNAc(2) isomer B as previous studies have suggested.