Clustered negative charges on the lipid membrane surface induce β-sheet formation of prion protein fragment 106-126
Clustered negative charges on the lipid membrane surface induce β-sheet formation of prion protein fragment 106-126
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DOI：
10.1021/bi700939j
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发表时间：
2007-10-16
期刊：
影响因子：
2.9
通讯作者：
Takeuchi, Hideo
中科院分区：
文献类型：
--
作者：
Miura, Takashi;Yoda, Mayumi;Takeuchi, Hideo
Prion蛋白(PrP)从富含α螺旋的正常细胞亚型(PrPC)到富含β折叠的致病亚型(PrPSc)的构象转换是Prion疾病发展过程中的一个关键事件，它发生在质膜上的凹陷、凹陷处。已知的与人PrP的106-126残基同源的多肽(PrP106-126)与PrPSc有几个共同的性质，例如形成β-折叠的能力和对PrPC表达细胞的毒性。因此，PrP106-126有望代表参与PrPSc形成的PrP的一段。我们用圆二色谱研究了含负电荷神经节苷脂的脂膜对PrP106-126二级结构的影响。该肽在含有神经节苷脂的膜上形成α-螺旋或β-片状结构。β-折叠的含量随肽/脂比的增加而增加，表明β-折叠的形成与带正电的多肽在带负电的膜表面的自结合有关。由高熔点和低熔点的带负电荷的甘油磷脂和中性甘油磷脂组成的膜也可以诱导类似的β-折叠的形成，拉曼光谱表明，在膜中发生了侧向相分离和带负电的脂类的聚集。由于含有神经节苷脂的膜也表现出横向相分离，聚集的负电荷被认为是PrP106-126β-折叠形成的原因。在小窝中，聚集的神经节苷脂分子可能与PrPC的106-126残基区域相互作用，促进PrPC向PrPSc的转化。
The conformational conversion of prion protein (PrP) from an alpha-helix-rich normal cellular isoform (PrPC) to a beta-sheet-rich pathogenic isoform (PrPSc) is a key event in the development of prion diseases, and it takes place in caveolae, cavelike invaginations of the plasma membrane. A peptide homologous to residues 106-126 of human PrP (PrP106-126) is known to share several properties with PrPSc e.g., the capability to form a beta-sheet and toxicity against PrPC-expressing cells. PrP106-126 is thus expected to represent a segment of PrP that is involved in the formation of PrPSc. We have examined the effect of lipid membranes containing negatively charged ganglioside, an important component of caveolae, on the secondary structure of PrP106-126 by circular dichroism. The peptide forms an alpha-helical or a beta-sheet structure on the ganglioside-containing membranes. The beta-sheet content increases with an increase of the peptide:lipid ratio, indicating that the beta-sheet formation is linked with self-association of the positively charged peptide on the negatively charged membrane surface. Analogous beta-sheet formation is also induced by membranes composed of negatively charged and neutral glycerophospholipids with high and low melting temperatures, respectively, in which lateral phase separation and clustering of negatively charged lipids occur as shown by Raman spectroscopy. Since ganglioside-containing membranes also exhibit lateral phase separation, clustered negative charges are concluded to be responsible for the beta-sheet formation of PrP106-126. In caveolae, clustered ganglioside molecules are likely to interact with the residue 106-126 region of PrPC to promote the PrPC-to-PrPSc conversion.