SITE-SPECIFIC STUDIES PROVIDE STRUCTURAL INFORMATION ON AMYLOID BETA OLIGOMERS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 Abeta多肽的聚集是阿尔茨海默病的主要原因。这些多肽的低聚形式特别令人感兴趣，因为它们具有很高的神经毒性，并可能在疾病进展中发挥重要作用。然而，目前关于Abeta寡聚体的结构信息很少。我们先前已经确定，根据与构象抗体的反应性，Aβ寡聚体可以至少分为两种结构类型(前纤维低聚物和纤维低聚物)。在这里，我们比较了Abeta40纤维和这两类低聚物的特定位置和整体构象稳定性。为了测量位点特异性稳定性，我们在Abeta40的整个序列中引入半胱氨酸残基，用荧光染料acryloan标记新的半胱氨酸，并在硫氰酸胍诱导的变性实验中研究它们在聚集体中的环境。我们发现，除25-30残基外，Abeta40纤维在15-35区域表现出高度的变性稳定性和中等的疏水性。这一模式与之前发表的Abeta40纤维的结构一致。纤维状低聚物表现出类似的模式，与我们的假设一致，即它们代表原纤维的碎片。然而，前纤维状低聚物在多肽的15-35区域表现出较低的变性稳定性和更疏水的环境。前纤维状低聚物独特的构象特性可能解释了它们被构象抗体区别识别的原因，并作为它们神经毒性的基础。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Aggregation of Abeta peptides is a major contributor to Alzheimer's disease. Oligomeric forms of these peptides are especially interesting due to their high neurotoxicity and potentially important role in disease progression. However, very little structural information is currently available on Abeta oligomers. We have previously established that Abeta oligomers can be divided into at least two structural classes (prefibrillar and fibrillar oligomers) based on their reactivity with conformational antibodies. Here we compared both site-specific and global conformational stability of Abeta 40 fibrils and both classes of oligomers. To measure the site-specific stability, we introduced cysteine residues throughout the sequence of Abeta 40, labeled the new cysteines with the fluorescent dye acrylodan, and investigated their environment within the aggregates in guanidine thiocyanate-induced denaturation experiments. We found that Abeta 40 fibrils show high stability towards denaturation and moderate hydrophobicity in the 15-35 region with the exception of residues 25-30. This pattern is consistent with previously published structures of Abeta 40 fibrils. Fibrillar oligomers show similar pattern consistent with our hypothesis that they represent fragments of protofibrils. However, prefibrillar oligomers show lower stability towards denaturation and more hydrophobic environment throughout the 15-35 region of the peptide. Distinct conformational properties of prefibrillar oligomers may explain their differential recognition by conformational antibodies and serve as a basis for their neurotoxicity.