Department of Biosciences and Bioengineering and Wadhwani Research Centre for Biosciences and Bioengineering, IIT Bombay, Powai, Mumbai 400076, India.
Cell Biochem Biophys. 2012 Sep;64(1):29-44. doi: 10.1007/s12013-012-9364-z.
Protein aggregation and amyloid formation are associated with both pathological conditions in humans such as Alzheimer's disease and native functions such as peptide hormone storage in the pituitary secretory granules in mammals. Here, we studied amyloid fibrils formation by three neuropeptides namely physalaemin, kassinin and substance P of tachykinin family using biophysical techniques including circular dichroism, thioflavin T, congo red binding and microscopy. All these neuropeptides under study have significant sequence similarity with Aβ(25-35) that is known to form neurotoxic amyloids. We found that all these peptides formed amyloid-like fibrils in vitro in the presence of heparin, and these amyloids were found to be nontoxic in neuronal cells. However, the extent of amyloid formation, structural transition, and morphology were different depending on the primary sequences of peptide. When Aβ(25-35) and Aβ40 were incubated with each of these neuropeptides in 1:1 ratio, a drastic increase in amyloid growths were observed compared to that of individual peptides suggesting that co-aggregation of Aβ and these neuropeptides. The electron micrographs of these co-aggregates were dissimilar when compared with individual peptide fibrils further supporting the possible incorporation of these neuropeptides in Aβ amyloid fibrils. Further, the fibrils of these neuropeptides can seed the fibrils formation of Aβ40 and reduced the toxicity of preformed Aβ fibrils. The present study of amyloid formation by tachykinin neuropeptides is not only providing an understanding of the mechanism of amyloid fibril formation in general, but also offering plausible explanation that why these neuropeptide might reduce the cytotoxicity associated with Alzheimer's disease related amyloids.
蛋白质聚集和淀粉样纤维形成与人类的病理状况有关，如阿尔茨海默病，也与哺乳动物垂体分泌颗粒中肽激素的天然储存等功能有关。在这里，我们使用生物物理技术（包括圆二色性、硫黄素 T、刚果红结合和显微镜）研究了三种神经肽，即 physalaemin、kassinin 和 tachykinin 家族的物质 P 的淀粉样纤维形成。所有这些在研究中的神经肽与已知形成神经毒性淀粉样纤维的 Aβ（25-35）具有显著的序列相似性。我们发现，所有这些肽在肝素存在的情况下都能在体外形成类似淀粉样的纤维，而且这些淀粉样纤维在神经元细胞中没有毒性。然而，淀粉样形成的程度、结构转变和形态因肽的一级序列而异。当 Aβ（25-35）和 Aβ40 与这些神经肽中的每一种以 1:1 的比例孵育时，与单独的肽相比，淀粉样纤维的生长明显增加，这表明 Aβ 和这些神经肽的共聚集。与单独的肽纤维相比，这些共聚集物的电子显微镜图像不同，进一步支持这些神经肽可能掺入 Aβ 淀粉样纤维中。此外，这些神经肽的纤维可以为 Aβ40 的纤维形成提供种子，并降低预先形成的 Aβ 纤维的毒性。这项关于 tachykinin 神经肽淀粉样纤维形成的研究不仅提供了对淀粉样纤维形成机制的一般理解，而且还提供了合理的解释，即为什么这些神经肽可能会降低与阿尔茨海默病相关淀粉样蛋白相关的细胞毒性。
