SITE-SPECIFIC STUDIES PROVIDE STRUCTURAL INFORMATION ON AMYLOID BETA OLIGOMERS

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 Abeta肽的聚集是阿尔茨海默病的主要原因。这些肽的寡聚体形式由于其高神经毒性和在疾病进展中的潜在重要作用而特别令人感兴趣。然而，目前关于Abeta寡聚体的结构信息非常少。我们先前已经确定，Abeta寡聚体可以根据其与构象抗体的反应性分为至少两种结构类别（前原纤维寡聚体和原纤维寡聚体）。在这里，我们比较了Abeta 40原纤维和两类寡聚体的位点特异性和全局构象稳定性。为了测量位点特异性稳定性，我们在Abeta 40的整个序列中引入了半胱氨酸残基，用荧光染料acrylodan标记了新的半胱氨酸，并在硫氰酸胍诱导的变性实验中研究了它们在聚集体内的环境。我们发现，Abeta 40原纤维在15-35区显示出高的变性稳定性和中等的疏水性，除了残基25-30。这种模式与先前公布的Abeta 40原纤维的结构一致。原纤维寡聚体显示出类似的模式，与我们的假设一致，他们代表的片段的原纤维。然而，在肽的整个15-35区域中，前原纤维寡聚体显示出对变性的较低稳定性和更疏水的环境。前原纤维寡聚体的独特构象特性可以解释它们被构象抗体的差异识别，并作为它们的神经毒性的基础。

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.