Golgi localization of ERManI defines spatial separation of the mammalian glycoprotein quality control system.
Golgi localization of ERManI defines spatial separation of the mammalian glycoprotein quality control system.
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DOI：
10.1091/mbc.e11-02-0118
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发表时间：
2011-08-15
影响因子：
3.3
通讯作者：
Sifers RN
中科院分区：
文献类型：
--
作者：
Pan S;Wang S;Utama B;Huang L;Blok N;Estes MK;Moremen KW;Sifers RN
目前的研究提供了重叠的动态糖蛋白折叠和质量控制使用不同的细胞内隔室作为哺乳动物细胞中蛋白质稳态网络的一部分的机制的见解。高尔基复合体已被牵连作为一个可能的组成部分内质网（ER）糖蛋白的质量控制，虽然其确切的作用是缺乏阐明。ERManI是一种假定的ER驻留甘露糖苷酶，在产生靶向错误折叠的N-连接糖蛋白的ER相关降解（ERAD）信号中起限速作用。在这里，我们证明，内源性人类同源物主要驻留在高尔基复合体，在那里它受到O-糖基化。为了区分产生糖蛋白ERAD信号的细胞内位点，将COPI结合基序附加到重组蛋白的N末端以促进其逆行易位回到ER。观察到修饰ERManI的部分再分布，沿着，错误折叠α1-抗胰蛋白酶变体NHK的N-连接聚糖被修剪的速率加快。尽管有这些观察结果，NHK降解的速率并没有加速，这表明高尔基复合体是糖蛋白ERAD底物标记的位点。总之，这些数据提供了一个潜在的机制解释的空间分离，糖蛋白质量控制组件在哺乳动物细胞中的操作。
The current study provides mechanistic insight into the overlapping dynamics by which glycoprotein folding and quality control use distinct intracellular compartments as part of the proteostasis network in mammalian cells. The Golgi complex has been implicated as a possible component of endoplasmic reticulum (ER) glycoprotein quality control, although the elucidation of its exact role is lacking. ERManI, a putative ER resident mannosidase, plays a rate-limiting role in generating a signal that targets misfolded N-linked glycoproteins for ER-associated degradation (ERAD). Herein we demonstrate that the endogenous human homologue predominantly resides in the Golgi complex, where it is subjected to O-glycosylation. To distinguish the intracellular site where the glycoprotein ERAD signal is generated, a COPI-binding motif was appended to the N terminus of the recombinant protein to facilitate its retrograde translocation back to the ER. Partial redistribution of the modified ERManI was observed along with an accelerated rate at which N-linked glycans of misfolded α1-antitrypsin variant NHK were trimmed. Despite these observations, the rate of NHK degradation was not accelerated, implicating the Golgi complex as the site for glycoprotein ERAD substrate tagging. Taken together, these data provide a potential mechanistic explanation for the spatial separation by which glycoprotein quality control components operate in mammalian cells.