β-amyloid is a substrate of autophagy in sporadic inclusion body myositis
β-amyloid is a substrate of autophagy in sporadic inclusion body myositis
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DOI：
10.1002/ana.21115
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发表时间：
2007-05-01
影响因子：
11.2
通讯作者：
Munz, Christian
中科院分区：
文献类型：
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作者：
Lunemann, Jan D.;Schmidt, Jens;Munz, Christian
目的：散发性包涵体肌炎（sIBM）是50岁以上患者最常见的获得性肌肉疾病。除了骨骼肌中的炎症外，淀粉样前体蛋白（APP）的过度表达及其蛋白水解片段β-淀粉样蛋白的细胞内积累在sIBM的发病机制中起着重要作用。在神经退行性疾病中，异常蛋白质的类似聚集最近已被证明易受自噬降解的影响。因此，我们分析了人类肌肉细胞系和sIBM muscle biopsizes.Methods的APP macroautophagy：共定位的APP与必要的自噬蛋白Atg 8/LC 3，这与preautophagosomal和autophagosomal膜通过脂质化，在CCL-136肌细胞系和肌肉活检免疫荧光分析。而APP在肌细胞系和组织切片中用特异性抗体可视化。Atg 8/LC 3定位分析后，GFP-Atg 8/LC 3转染或与Atg 8/LC 3特异性antiserums.Results：我们在这里证明，Atg 8/LC 3与APP共定位在培养的人肌肉细胞。此外，APP/β-淀粉样蛋白的自噬体可以观察到增加的频率在sIBM肌肉活检的肌纤维，但不是在非肌病肌肉或非空泡化肌病对照。APP/β-淀粉样蛋白和Ata 8/LC 3双阳性隔室几乎只在II型变性肌纤维中观察到（快速抽搐），部分与肌纤维上I类和II类主要组织相容性复合体（MHC）的过度表达以及CD 4（+）和CD 8（+）细胞的侵袭有关。这些发现表明，APP/β-淀粉样蛋白的目标是通过大自噬溶酶体降解，并建议自噬途径应探讨其潜在的治疗价值sIBM。
Objective: Sporadic Inclusion Body Myositis (sIBM) is the most common acquired muscle disease in patients above 50 years of age. Apart from inflammation in the skeletal muscle, overexpression of amyloid precursor protein (APP) and intracellular accumulation of its proteolytic fragment fi-amyloid play a central role in the pathogenesis of sIBM. In neurodegenerative disorders, similar aggregations of aberrant proteins have recently been shown to be susceptible to autophagic degradation. Therefore, we analyzed macroautophagy of APP in human muscle cell lines and sIBM muscle biopsies.Methods: Colocalization of APP with the essential autophagy protein Atg8/LC3, which associates with preautophagosomal and autophagosomal membranes via lipidation, was analyzed in the CCL-136 muscle cell line and muscle biopsies by immunofluorescence. While APP was visualized with specific antibodies in the muscle cell line and in tissue sections. Atg8/LC3 localization was analyzed after GFP-Atg8/LC3 transfection or with an Atg8/LC3 specific antiserum, respectively.Results: We demonstrate here that Atg8/LC3 colocalizes with APP in cultured human muscle cells. In addition, APP/beta-amyloid-containing autophagosomes can be observed at increased frequency in muscle fibers of sIBM muscle biopsies, but not in non-myopathic muscle or non-vacuolated myopathic controls. APP/beta-amyloid and Ata8/LC3 double-positive compartments were almost exclusively observed in degenerating muscle fibers of the type II (fast-twitching) and were in part associated with overexpression of major histocompatibility complex (MHC) class I and II on myofibers and invasion by CD4(+) and CD8(+) cells.Interpretation: These findings indicate that APP/beta-amyloid is targeted for lysosomal degradation via macroautophagy and suggest that the autophagy pathway should be explored for its potential therapeutic merit in sIBM.