Department of Chemistry, National Taiwan Normal University, Taipei 116, Taiwan.
Department of Chemistry, Fu Jen Catholic University, New Taipei City 24205, Taiwan.
Biochemistry. 2020 Apr 21;59(15):1482-1492. doi: 10.1021/acs.biochem.0c00076. Epub 2020 Apr 13.
Aggregation of polypeptides and proteins is commonly associated with human and other vertebrate diseases. For example, amyloid plaques consisting of amyloid-β proteins are frequently identified in Alzheimer's disease and islet amyloid formed by islet amyloid polypeptide (IAPP, amylin) can be found in most patients with type 2 diabetes (T2D). Although many fluorescent dyes have been developed to stain amyloid fibrils, very few examples have been designed for IAPP. In this study, a series of environmentally sensitive fluorescent probes using flavonoid as a scaffold design are rationally designed and synthesized. One of these probes, namely 3-HF-ene-4'-OMe, can bind to IAPP fibrils but not nonfibrillar IAPP by exhibiting a much stronger fluorescent enhancement at 535 nm. In addition, this probe shows better detection sensitivity to IAPP fibrils compared with that of conventionally used thioflavin-T. We demonstrate that 3-HF-ene-4'-OMe can be used to monitor the kinetics of IAPP fibril formation even in the presence an amyloid inhibitor. To test the specificity of the probe, we attempt to incubate this probe with amyloid fibrils formed from other amyloidogenic proteins. Interestingly, this probe shows different responses when mixed with these fibrils, suggesting the mode of binding of this probe on these fibrils could be different. Moreover, we show that this probe is not toxic to pancreatic mouse β-cells. Further structural optimization based on the structure of 3-HF-ene-4'-OMe may yield a specific probe for imaging islet amyloid in the pancreas. That would improve our understanding of the relationship between islet amyloid and T2D.
多肽和蛋白质的聚集通常与人类和其他脊椎动物的疾病有关。例如，由淀粉样β蛋白组成的淀粉样斑块经常在阿尔茨海默病中被发现，而由胰岛淀粉样多肽（IAPP，胰岛淀粉样蛋白）形成的胰岛淀粉样可以在大多数 2 型糖尿病（T2D）患者中找到。尽管已经开发了许多荧光染料来染色淀粉样纤维，但很少有设计用于 IAPP 的染料。在这项研究中，设计并合理合成了一系列使用黄酮类作为支架的环境敏感荧光探针。这些探针中的一种，即 3-HF-ene-4'-OMe，可以与 IAPP 纤维结合，但不能与非纤维状 IAPP 结合，在 535nm 处表现出更强的荧光增强。此外，与传统使用的硫代黄素-T 相比，该探针对 IAPP 纤维的检测灵敏度更好。我们证明 3-HF-ene-4'-OMe 可用于监测 IAPP 纤维形成的动力学，即使在存在淀粉样抑制剂的情况下也是如此。为了测试探针的特异性，我们试图将该探针与其他淀粉样蛋白形成的淀粉样纤维孵育。有趣的是，当与这些纤维混合时，该探针显示出不同的反应，这表明该探针与这些纤维的结合方式可能不同。此外，我们表明该探针对胰腺小鼠β细胞没有毒性。进一步基于 3-HF-ene-4'-OMe 的结构优化可能会产生一种用于成像胰腺中胰岛淀粉样的特异性探针。这将有助于我们理解胰岛淀粉样与 T2D 之间的关系。
