Truncation of αB-crystallin by the myopathy-causing Q151X mutation significantly destabilizes the protein leading to aggregate formation in transfected cells
Truncation of αB-crystallin by the myopathy-causing Q151X mutation significantly destabilizes the protein leading to aggregate formation in transfected cells
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DOI：
10.1074/jbc.m706453200
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发表时间：
2008-04-18
影响因子：
4.8
通讯作者：
Quinlan, Roy A.
中科院分区：
文献类型：
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作者：
Hayes, Victoria H.;Devlin, Glyn;Quinlan, Roy A.
在这里，我们研究了引起肌病的α b -晶体蛋白Q151X突变对其结构和功能的影响。这种突变去除α b -晶体蛋白的c端结构域，预计会损害其寡聚化和伴侣活性。我们将其与另外两个α b -晶体蛋白突变体（450delA, 464delCT）以及一系列c端截断（E164X, E165X， K174X和A171X）进行了比较。我们发现Q151X突变的影响并不总是像预测的那样。具体来说，我们发现虽然Q151X突变降低了α B-crystallin的寡聚化，甚至增加了一些伴侣蛋白的活性，但它也显著地破坏了α B-crystallin的稳定性，使其自聚集。这一结论得到了我们对其他致病突变体和α b -晶体蛋白c端截断结构体的分析的支持。450delA和464delCT突变体只能与野生型α b -晶体蛋白复合体进行折叠和分析，而Q151X α b -晶体蛋白则不是这样。从这些研究中，我们得出结论，c端延伸的所有三种致病突变（450delA， 464delCT和Q151X）都破坏了α b -晶体蛋白的稳定，并增加了其自聚集的倾向。我们认为，正是这一点，而不是伴侣活性的灾难性丧失，才是本文研究的三种致病突变所报告的疾病发展的主要因素。为了支持这一假设，我们发现Q151X α b -晶体蛋白主要存在于瞬时转染细胞的细胞提取物的不溶性部分，这是由于细胞质聚集体的形成。
Here we investigate the effects of a myopathy-causing mutation in alpha B-crystallin, Q151X, upon its structure and function. This mutation removes the C-terminal domain of alpha B-crystallin, which is expected to compromise both its oligomerization and chaperone activity. We compared this to two other alpha B-crystallin mutants (450delA, 464delCT) and also to a series of C-terminal truncations (E164X, E165X, K174X, and A171X). We find that the effects of the Q151X mutation were not always as predicted. Specifically, we have found that although the Q151X mutation decreased oligomerization of alpha B-crystallin and even increased some chaperone activities, it also significantly destabilized alpha B-crystallin causing it to self-aggregate. This conclusion was supported by our analyses of both the other disease-causing mutants and the series of C-terminal truncation constructs of alpha B-crystallin. The 450delA and 464delCT mutants could only be refolded and assayed as a complex with wild type alpha B-crystallin, which was not the case for Q151X alpha B-crystallin. From these studies, we conclude that all three disease-causing mutations (450delA, 464delCT, and Q151X) in the C-terminal extension destabilize alpha B-crystallin and increase its tendency to self-aggregate. We propose that it is this, rather than a catastrophic loss of chaperone activity, which is a major factor in the development of the reported diseases for the three disease-causing mutations studied here. In support of this hypothesis, we show that Q151X alpha B-crystallin is found mainly in the insoluble fraction of cell extracts from transient transfected cells, due to the formation of cytoplasmic aggregates.