Intracellular inclusions containing mutant α1-antitrypsin Z are propagated in the absence of autophagic activity
Intracellular inclusions containing mutant α1-antitrypsin Z are propagated in the absence of autophagic activity
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DOI：
10.1074/jbc.m509409200
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发表时间：
2006-02-17
影响因子：
4.8
通讯作者：
Yoshimori, T
中科院分区：
文献类型：
--
作者：
Kamimoto, T;Shoji, S;Yoshimori, T
突变型α（1）-抗胰蛋白酶Z（α（1）-ATZ）蛋白在肝细胞的内质网内积累时具有形成聚集聚合物的倾向，其与遗传性α（1）-抗胰蛋白酶（α（1）-AT）缺乏的慢性肝损伤和肝细胞癌的发展相关。先前的研究表明，α（1）-ATZ的有效细胞内降解与α（1）-AT缺乏时的肝脏疾病保护相关，并且泛素蛋白酶体系统是α（1）-ATZ处置的主要途径，但不是唯一途径。另一种细胞内降解系统，自噬，也涉及α（1）-AT缺乏症的病理生理学。为了提供自噬介导的α（1）-ATZ处置的遗传学证据，我们使用了缺失Atg 5基因的细胞系，Atg 5基因是启动自噬所必需的。在没有自噬的情况下，α（1）-ATZ的降解被延迟，并且α（1）-ATZ的特征性细胞内含物积累。在野生型细胞中，观察到自噬体膜标记物GFP-LC 3和α（1）-ATZ的共定位，并且当通过抑制自噬体和溶酶体之间的融合来阻止自噬体的清除时，这种共定位增强。通过使用与GFP-LC 3小鼠交配的具有肝脏特异性诱导表达的α（1）-ATZ的转基因小鼠，我们还发现体内肝脏中α（1）-ATZ的表达足以诱导自噬。这些数据提供了明确的证据，自噬可以参与α（1）-ATZ的质量控制/降解途径，并表明自噬降解在防止α（1）-ATZ的毒性蓄积中起着重要作用。
Mutant alpha(1)-antitrypsin Z (alpha(1)-ATZ) protein, which has a tendency to form aggregated polymers as it accumulates within the endoplasmic reticulum of the liver cells, is associated with the development of chronic liver injury and hepatocellular carcinoma in hereditary alpha(1)-antitrypsin (alpha(1)-AT) deficiency. Previous studies have suggested that efficient intracellular degradation of alpha(1)-ATZ is correlated with protection from liver disease in alpha(1)-AT deficiency and that the ubiquitinproteasome system accounts for a major route, but not the sole route, of alpha(1)-ATZ disposal. Yet another intracellular degradation system, autophagy, has also been implicated in the pathophysiology of alpha(1)-AT deficiency. To provide genetic evidence for autophagymediated disposal of alpha(1)-ATZ, here we used cell lines deleted for the Atg5 gene that is necessary for initiation of autophagy. In the absence of autophagy, the degradation of alpha(1)-ATZ was retarded, and the characteristic cellular inclusions of alpha(1)-ATZ accumulated. In wild-type cells, colocalization of the autophagosomal membrane marker GFP-LC3 and alpha(1)-ATZ was observed, and this colocalization was enhanced when clearance of autophagosomes was prevented by inhibiting fusion between autophagosome and lysosome. By using a transgenic mouse with liver-specific inducible expression of alpha(1)-ATZ mated to the GFP-LC3 mouse, we also found that expression of alpha(1)-ATZ in the liver in vivo is sufficient to induce autophagy. These data provide definitive evidence that autophagy can participate in the quality control/degradative pathway for alpha(1)-ATZ and suggest that autophagic degradation plays a fundamental role in preventing toxic accumulation of alpha(1)-ATZ.