The ubiquitin ligase Hrd1 promotes degradation of the Z variant alpha 1-antitrypsin and increases its solubility
The ubiquitin ligase Hrd1 promotes degradation of the Z variant alpha 1-antitrypsin and increases its solubility
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DOI：
10.1007/s11010-010-0600-9
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发表时间：
2010
影响因子：
4.3
通讯作者：
Haiping Wang;Qi Li;Yujun Shen;Aimin Sun;Xiaoguang Zhu;Shengyun Fang;Yuxian Shen
中科院分区：
文献类型：
--
作者：
Haiping Wang;Qi Li;Yujun Shen;Aimin Sun;Xiaoguang Zhu;Shengyun Fang;Yuxian Shen
α1-抗胰蛋白酶（AAT）缺乏症是一种常染色体隐性遗传疾病，其特征是错误折叠的 AAT 在肝细胞内质网（ER）中滞留，并且 AAT 血清水平显着降低。先前的研究表明，泛素-蛋白酶体途径参与了 AAT（ATZ）Z 变体的降解。然而，ATZ 降解的详细机制尚不完全清楚。我们研究了内质网膜嵌入的泛素连接酶 (E3) Hrd1 是否通过内质网相关降解 (ERAD) 促进 ATZ 的去除。我们的结果表明，在用质粒编码 ATZ 转染的细胞中，Hrd1 降低了 ATZ 的细胞内水平，尤其是去污剂不溶部分的水平。还发现 ATZ 的降解依赖于 Hrd1 的功能性 E3 活性。此外，我们还证明 Hrd1 增加了 ATZ 的溶解度。放线菌酮 (CHX) 追踪和蛋白酶体抑制实验表明，泛素-蛋白酶体途径参与 Hrd1 介导的 ATZ 降解。此外，我们发现 Hrd1 有助于维持 ATZ 表达细胞的正常形态。这些数据表明，Hrd1通过ERAD增强ATZ的去除，并减弱细胞内ATZ的积累和毒性，这意味着Hrd1在治疗AAT缺陷性疾病中具有潜在价值。
Alpha 1-antitrypsin (AAT) deficiency is an autosomal recessive disorder that is characterized by the retention of misfolded AAT in the endoplasmic reticulum (ER) of hepatocytes and a significant decrease in the serum levels of AAT. Previous studies have demonstrated that the ubiquitin–proteasome pathway is involved in the degradation of the Z variant of AAT (ATZ). However, the detailed mechanisms of ATZ degradation are not fully understood. We investigated whether the ER membrane-embedded ubiquitin ligase (E3) Hrd1 promotes the removal of ATZ through ER-associated degradation (ERAD). Our results indicate that Hrd1 decreases intracellular levels of ATZ, especially the detergent-insoluble fraction, in cells transfected with a plasmid-encoding ATZ. The degradation of ATZ was also found to be dependent on the functional E3 activity of Hrd1. In addition, we demonstrated that Hrd1 increases the solubility of ATZ. Cycloheximide (CHX) chase and proteasome inhibition experiments showed that the ubiquitin–proteasome pathway is involved in Hrd1-mediated ATZ degradation. Furthermore, we found that Hrd1 helped to maintain normal morphology of ATZ expressing cells. These data indicate that Hrd1 enhances the removal of ATZ through ERAD and attenuates intracellular ATZ accumulation and toxicity, which implies a potential value for Hrd1 in the treatment of AAT deficiency diseases.