Kurganov Boris, Doh Michael, Arispe Nelson
Department of Anatomy, Physiology and Genetics, and Institute for Molecular Medicine, Uniformed Services University School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD 20814, USA.
Peptides. 2004 Feb;25(2):217-32. doi: 10.1016/j.peptides.2004.01.001.
To compare both the peptide molecular self-aggregation and the interaction with membrane lipids of the Alzheimer's amyloid beta (Abeta)40, Abeta42 peptides, and the cytotoxic peptides human amylin and prion (106-126) peptides, we applied a liposome aggregation technology. The kinetics of the changes in the optical density (DeltaOD) of liposome suspensions generated by the aggregation of liposomes induced by these peptides, allowed us to comparatively analyze their phospholipid affinity and self-aggregation. The kinetic curves showed an initial nonlinear region where d(DeltaOD)/dt followed first order kinetics corresponding to the binding of the peptides to the membrane of the liposome, a linear region where d(DeltaOD)/dt was constant, corresponding to the interaction between two membrane-bound peptide molecules, and a final slower increasing nonlinear region that corresponds to nucleation or seeding of aggregation. The analysis of the aggregation curves demonstrated that amylin and prion peptides also showed affinity for the acidic phospholipid phosphatidylserine (PS), as it has previously been shown for the Alzheimer's Abeta40, Abeta42 peptides. Abeta42 showed the highest, and amylin the lowest, affinity for the liposome membrane. When bound to the membrane of the liposomes, all the peptides preserved the self-aggregation characteristics observed in solution. Aging the Abeta40 and Abeta42 peptide solutions that permit molecular self-aggregation reduced their capacity to induce liposome aggregation. The self-aggregation of membrane-bound prion molecules was several orders of magnitude higher than that observed for the other toxic peptides. Incorporation of the ganglioside GM1 into the membrane of liposomes enhanced the peptide-induced liposome aggregation. Kinetic analysis revealed that this enhancement was due to facilitation of the formation of bridges between membrane-bound peptide molecules, demonstrating that the peptide-membrane interaction and the peptide amyloidogenesis are independent functions performed at separate molecular regions.
为了比较阿尔茨海默病淀粉样β蛋白（Aβ）40、Aβ42肽以及细胞毒性肽人胰岛淀粉样多肽和朊病毒（106 - 126）肽的肽分子自聚集以及与膜脂的相互作用，我们应用了脂质体聚集技术。这些肽诱导脂质体聚集所产生的脂质体悬浮液的光密度变化（ΔOD）动力学，使我们能够比较分析它们对磷脂的亲和力和自聚集情况。动力学曲线显示出一个初始非线性区域，其中d(ΔOD)/dt遵循一级动力学，对应于肽与脂质体膜的结合；一个线性区域，其中d(ΔOD)/dt恒定，对应于两个膜结合肽分子之间的相互作用；以及一个最终较慢增加的非线性区域，对应于聚集的成核或播种。聚集曲线分析表明，胰岛淀粉样多肽和朊病毒肽对酸性磷脂磷脂酰丝氨酸（PS）也表现出亲和力，正如之前对阿尔茨海默病Aβ40、Aβ42肽所显示的那样。Aβ42对脂质体膜的亲和力最高，而胰岛淀粉样多肽最低。当与脂质体膜结合时，所有肽都保留了在溶液中观察到的自聚集特性。使允许分子自聚集的Aβ40和Aβ42肽溶液老化会降低它们诱导脂质体聚集的能力。膜结合朊病毒分子的自聚集比其他有毒肽观察到的自聚集高几个数量级。将神经节苷脂GM1掺入脂质体膜中增强了肽诱导的脂质体聚集。动力学分析表明，这种增强是由于促进了膜结合肽分子之间桥的形成，表明肽 - 膜相互作用和肽淀粉样变是在不同分子区域执行的独立功能。
