αB-crystallin is a small heat shock protein that forms a heterooligomeric complex with αA-crystallin in the ocular lens. It is also widely distributed in tissues throughout the body and has been linked with neurodegenerative diseases such as Alzheimer's, where it is associated with amyloid fibrils. Crystallins can form amorphous aggregates in cataracts as well as more structured amyloid-like fibrils. The arginine 120 to glycine (R120G) mutation in αB-crystallin (Cryab-R120G) results in high molecular weight crystallin protein aggregates and loss of the chaperone activity of the protein in vitro, and it is associated with human hereditary cataracts and myopathy. Characterizing the amorphous (unstructured) versus the highly ordered (amyloid fibril) nature of crystallin aggregates is important in understanding their role in disease and important to developing pharmacological treatments for cataracts. We investigated protein secondary structure in wild-type (WT) and Cryab-R120G knock-in mutant mouse lenses using two-dimensional infrared (2DIR) spectroscopy, which has been used to detect amyloid-like fibrils in human lenses and measure UV radiation-induced changes in porcine lenses. Our goal was to compare the aggregated proteins in this mouse lens model to human lenses and evaluate the protein structural relevance of the Cryab-R120G knock-in mouse model to general age-related cataract disease. In the 2DIR spectra, amide I diagonal peak frequencies were red-shifted to smaller wavenumbers in mutant mouse lenses as compared to WT mouse lenses, consistent with an increase in ordered secondary structure. The cross peak frequency and intensity indicated the presence of amyloid in the mutant mouse lenses. While the diagonal and cross peak changes in location and intensity from the 2DIR spectra indicated significant structural differences between the wild type and mutant mouse lenses, these differences were smaller than those found in human lenses; thus, the Cryab-R120G knock-in mouse lenses contain less amyloid-like secondary structure than human lenses. The results of the 2DIR spectroscopy study confirm the presence of amyloid-like secondary structure in Cryab-R120G knock-in mice with cataracts and support the use of this model to study age-related cataract.

中文翻译：

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通过二维红外光谱分析遗传性白内障 Cryab-R120G 敲入小鼠模型中的淀粉样蛋白二级结构。


αB-晶状体蛋白是一种小的热休克蛋白，在眼晶状体中与 αA-晶状体蛋白形成异寡聚复合物。它还广泛分布在全身组织中，并与神经退行性疾病有关，例如阿尔茨海默氏症，它与淀粉样原纤维有关。晶状体蛋白可以在白内障中形成无定形聚集体以及更具结构性的淀粉样蛋白样原纤维。 αB-晶状体蛋白 (Cryab-R120G) 中的精氨酸 120 突变为甘氨酸 (R120G) 会导致高分子量晶状体蛋白聚集，并在体外丧失该蛋白的伴侣活性，与人类遗传性白内障和肌病有关。表征晶状体蛋白聚集体的无定形（非结构化）与高度有序（淀粉样原纤维）性质对于理解其在疾病中的作用非常重要，对于开发白内障的药物治疗也很重要。我们使用二维红外 (2DIR) 光谱研究了野生型 (WT) 和 Cryab-R120G 敲入突变小鼠晶状体中的蛋白质二级结构，该光谱已用于检测人类晶状体中的类淀粉样原纤维并测量紫外线辐射 -引起猪晶状体的变化。我们的目标是比较该小鼠晶状体模型与人类晶状体中的聚集蛋白，并评估 Cryab-R120G 敲入小鼠模型与一般年龄相关性白内障疾病的蛋白质结构相关性。在 2DIR 光谱中，与 WT 小鼠晶状体相比，突变小鼠晶状体中酰胺 I 对角峰值频率红移至更小的波数，这与有序二级结构的增加一致。交叉峰频率和强度表明突变小鼠晶状体中存在淀粉样蛋白。 虽然 2DIR 光谱的位置和强度的对角线和交叉峰变化表明野生型和突变型小鼠晶状体之间存在显着的结构差异，但这些差异小于人类晶状体中发现的差异。因此，Cryab-R120G 敲入小鼠晶状体比人类晶状体含有更少的类淀粉样二级结构。 2DIR 光谱研究的结果证实了患有白内障的 Cryab-R120G 敲入小鼠中存在淀粉样蛋白样二级结构，并支持使用该模型来研究与年龄相关的白内障。