Destabilization of human IAPP amyloid fibrils by proline mutations outside of the putative amyloidogenic domain: Is there a critical amyloidogenic domain in human IAPP?
Destabilization of human IAPP amyloid fibrils by proline mutations outside of the putative amyloidogenic domain: Is there a critical amyloidogenic domain in human IAPP?
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DOI：
10.1016/j.jmb.2005.10.052
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发表时间：
2006-01-13
影响因子：
5.6
通讯作者：
Raleigh, DP
中科院分区：
文献类型：
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作者：
Abedini, A;Raleigh, DP
胰岛淀粉样多肽(IAPP；Amylin)与2型糖尿病中淀粉样蛋白的形成有关。并不是所有的生物体都形成胰岛淀粉样蛋白，淀粉样蛋白的形成与初级序列的变化密切相关。对人和啮齿动物IAPP的研究表明，氨基酸残基20-29区是重要的淀粉样蛋白调控序列。大鼠的20-29序列含有三个脯氨酸残基，不形成淀粉样蛋白，而人类的序列不含脯氨酸，很容易形成淀粉样蛋白。这导致了这样一种观点，即20-29区域构成了决定整个序列性质的关键的淀粉样致变域。人和大鼠IAPP的不同行为可能是由于20-29区域的差异，或者仅仅是因为多个脯氨酸残基破坏淀粉样纤维的稳定。我们测试了20-29区域的关键程度，方法是研究在这一片段中与人类多肽相同但在该区域之外有三个脯氨酸残基的变体。我们设计了人IAPP的淀粉样蛋白8-37区(hIAPP(8-37)3XP)的一个变体，在第17、19和30位进行了脯氨酸替换。与野生型相比，3XP变异体更容易合成，并且具有显著更大的溶解性。傅里叶变换红外光谱、透射电子显微镜、刚果红染色和硫代黄素-T结合试验表明，该变异体形成P-折叠结构的倾向降低，形成的沉积物的结构有序性比野生型低得多。远紫外圆二色谱研究表明，hIAPP(8-37)3XP在长时间孵育后形成的少量β-折叠结构在Tris缓冲液中稀释后很容易解离为无规卷曲结构。在假定的核心区之外的Pro取代有效地消除淀粉样蛋白的形成的观察表明，IAPP聚集的模型必须考虑来自其他区域的贡献。(C)2006爱思唯尔有限公司。保留所有权利。
Islet amyloid polypeptide (IAPP; amylin) is responsible for amyloid formation in type-2 diabetes. Not all organisms form islet amyloid, and amyloid formation correlates strongly with variations in primary sequence. Studies of human and rodent IAPP have pointed to the amino acid residues 20-29 region as the important amyloid-modulating sequence. The rat 20-29 sequence contains three proline residues and does not form amyloid, while the human sequence contains no proline and readily forms amyloid. This has led to the view that the 20-29 region constitutes a critical amyloidogenic domain that dictates the properties of the entire sequence. The different behavior of human and rat IAPP could be due to differences in the 20-29 region or due simply to the fact that multiple proline residues destabilize amyloid fibrils. We tested how critical the 20-29 region is by studying a variant identical with the human peptide in this segment but with three proline residues outside this region. We designed a variant of the amyloidogenic 8-37 region of human IAPP (hIAPP(8-37) 3XP) with proline substitutions at positions 17, 19 and 30. Compared to the wild-type, the 3XP variant was much easier to synthesize and had dramatically greater solubility. Fourier transform infra red spectroscopy, transmission electron microscopy, Congo red staining and thioflavin-T binding indicate that this variant has a reduced tendency to form P-sheet structure and forms deposits with much less structural order than the wild-type. Far-UV CD studies show that the small amount of beta-sheet structure developed by hIAPP(8-37) 3XP after long periods of incubation dissociates readily into random-coil structure upon dilution into Tris buffer. The observation that proline substitutions outside the putative core domain effectively abolish amyloid formation indicates that models of IAPP aggregation must consider contributions from other regions. (c) 2006 Elsevier Ltd. All rights reserved.