Pillot T, Lins L, Goethals M, Vanloo B, Baert J, Vandekerckhove J, Rosseneu M, Brasseur R
Department of Biochemistry, Universiteit Gent, Belgium.
J Mol Biol. 1997 Dec 5;274(3):381-93. doi: 10.1006/jmbi.1997.1382.
The prion protein (PrPC) is a glycoprotein of unknown function normally found at the surface of neurons and of glial cells. It is involved in diseases such as bovine spongiform encephalopathy, and Creutzfeldt-Jakob disease in the human, where PrPC is converted into an altered form (termed PrPSc). PrPSc is highly resistant towards proteolytic degradation and accumulates in the central nervous system of affected individuals. By analogy with the pathological events occuring during the development of Alzheimer's disease, controverses still exist regarding the relationship between amyloidogenesis, prion aggregation and neuronal loss. To unravel the mechanism of PrP neurotoxicity and understand the interaction of PrP with cellular membranes, a series of natural and variant peptides spanning residues 118 to 135 of PrP was synthesized. The potential of these peptides to induce fusion of unilamellar lipid vesicles was investigated. According to computer modeling calculations, the 120 to 133 domain of PrP is predicted to be a tilted lipid-associating peptide, and to insert in a oblique way into a lipid bilayer through its N-terminal end. In addition to amyloidogenic properties exhibited in vitro by these peptides, peptide-induced vesicle fusion was demonstrated by several techniques, including lipid- and core-mixing assays. Elongation of the 120 to 133 peptide towards the N- and C-terminal ends of the PrP sequence showed that the 118 to 135 PrP peptide has maximal fusogenic properties, while the variant peptides had no effect. Due to their high hydrophobicity, all peptides tested were able to interact with liposomes to induce leakage of encapsulated calcein. We demonstrate also that the propensity of the peptides to fold as an alpha-helix increases their fusogenic activity, thus accounting for the maximal fusogenic activity of the most stable helix at residues 118 to 135. These data suggest that, by analogy with the C-terminal domain of the beta-amyloid peptide, the fusogenic properties exhibited by the prion peptides might contribute to the neurotoxicity of these peptides by destabilizing cellular membranes.
朊病毒蛋白（PrPC）是一种功能未知的糖蛋白，通常存在于神经元和神经胶质细胞表面。它与诸如牛海绵状脑病以及人类克雅氏病等疾病有关，在这些疾病中，PrPC会转变为一种改变的形式（称为PrPSc）。PrPSc对蛋白水解降解具有高度抗性，并在受影响个体的中枢神经系统中积累。与阿尔茨海默病发展过程中发生的病理事件类似，关于淀粉样蛋白生成、朊病毒聚集与神经元丧失之间的关系仍存在争议。为了阐明PrP神经毒性的机制并了解PrP与细胞膜的相互作用，合成了一系列跨越PrP第118至135位残基的天然和变异肽。研究了这些肽诱导单层脂质囊泡融合的潜力。根据计算机建模计算，PrP的120至133结构域预计是一种倾斜的脂质结合肽，并通过其N末端以倾斜方式插入脂质双层。除了这些肽在体外表现出的淀粉样蛋白生成特性外，还通过包括脂质和核心混合测定在内的几种技术证明了肽诱导的囊泡融合。将120至133肽向PrP序列的N末端和C末端延伸表明，118至135 PrP肽具有最大的融合特性，而变异肽则没有作用。由于它们的高疏水性，所有测试的肽都能够与脂质体相互作用以诱导包封的钙黄绿素泄漏。我们还证明，肽折叠成α螺旋的倾向增加了它们的融合活性，从而解释了第118至135位残基处最稳定螺旋具有最大融合活性的原因。这些数据表明，类似于β淀粉样肽的C末端结构域，朊病毒肽表现出的融合特性可能通过破坏细胞膜的稳定性而导致这些肽的神经毒性。
