A role for AGL ubiquitination in the glycogen storage disorders of Lafora and Cori's disease
A role for AGL ubiquitination in the glycogen storage disorders of Lafora and Cori's disease
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DOI：
10.1101/gad.1553207
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发表时间：
2007-10-01
影响因子：
10.5
通讯作者：
Saltiel, Alan R.
中科院分区：
文献类型：
--
作者：
Cheng, Alan;Zhang, Mei;Saltiel, Alan R.
柯里氏病是一种糖原储存障碍，其特征是糖原去分支酶amylo-1，6-glucosidase，4-alpha-glucanotransferase(Agl)缺乏。在这里，我们证明了AGL的G1448R基因变体不能与糖原结合，并表现出稳定性降低，这是通过蛋白酶体抑制来挽救的。与野生型相比，AGL G1448R的泛素化程度更高，并在蛋白酶体受损时形成侵袭体。此外，E3泛素连接酶Malin与AGL的泛素化相互作用并促进其泛素化。已知Malin在Lafora病中发生突变，Lafora病是一种常染色体隐性遗传病，临床特征是聚葡糖体积聚，类似于分支不良的糖原。在HepG2细胞中的转染研究表明，AGL是胞质的，而Malin主要是核的。然而，在耗尽糖原储备4h后，接近90%的转基因细胞显示出部分AGL核染色。此外，用升高cAMP的试剂刺激细胞会增加Malin水平和Malin/Agl复合体的形成。隔夜禁食后再喂食小鼠2小时，可使肝脏AGL水平降低48%。综上所述，这些结果表明，与糖原的结合对AGL的稳定性起着至关重要的调节作用，而且它的泛素化可能在Lafora病和Cori病的病理生理中发挥重要作用。
Cori's disease is a glycogen storage disorder characterized by a deficiency in the glycogen debranching enzyme, amylo-1,6-glucosidase,4-alpha-glucanotransferase (AGL). Here, we demonstrate that the G1448R genetic variant of AGL is unable to bind to glycogen and displays decreased stability that is rescued by proteasomal inhibition. AGL G1448R is more highly ubiquitinated than its wild-type counterpart and forms aggresomes upon proteasome impairment. Furthermore, the E3 ubiquitin ligase Malin interacts with and promotes the ubiquitination of AGL. Malin is known to be mutated in Lafora disease, an autosomal recessive disorder clinically characterized by the accumulation of polyglucosan bodies resembling poorly branched glycogen. Transfection studies in HepG2 cells demonstrate that AGL is cytoplasmic whereas Malin is predominately nuclear. However, after depletion of glycogen stores for 4 h, similar to 90% of transfected cells exhibit partial nuclear staining for AGL. Furthermore, stimulation of cells with agents that elevate cAMP increases Malin levels and Malin/AGL complex formation. Refeeding mice for 2 h after an overnight fast causes a reduction in hepatic AGL levels by 48%. Taken together, these results indicate that binding to glycogen crucially regulates the stability of AGL and, further, that its ubiquitination may play an important role in the pathophysiology of both Lafora and Cori's disease.