Evidence for protein X binding to a discontinuous epitope on the cellular prion protein during scrapie prion propagation
Evidence for protein X binding to a discontinuous epitope on the cellular prion protein during scrapie prion propagation
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DOI：
10.1073/pnas.94.19.10069
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发表时间：
1997-09-16
影响因子：
11.1
通讯作者：
Prusiner, SB
中科院分区：
文献类型：
--
作者：
Kaneko, K;Zulianello, L;Prusiner, SB
对人（Hu）朊病毒向转基因（Tg）小鼠的传播的研究表明，另一种暂时命名为蛋白X的分子参与了新生羊瘙痒病朊病毒蛋白同种型（PrPSc）的形成，我们报告了用嵌合Hu/Hu基因转染的羊瘙痒病感染的小鼠神经母细胞瘤细胞鉴定蛋白X与PrP（PrPC）细胞亚型结合的位点。MoPrP基因，即使蛋白X尚未被分离，在位置214或218处的Hu残基的取代阻止了PrPSc的形成。这些残基的侧链从C-末端α-螺旋的相同表面突出，并与相邻环中的残基167和171形成不连续表位。在位置167、171或218处的碱性残基的取代也阻止了PrPSc的形成：在机械水平上，这些突变的PrPs似乎通过结合蛋白X并使其无法用于朊病毒繁殖而充当“显性阴性”。我们的研究结果似乎解释了人类和绵羊PrP中碱性多态性残基的保护作用，并提出了治疗和预防朊病毒疾病的方法。
Studies on the transmission of human (Hu) prions to transgenic (Tg) mice suggested that another molecule provisionally designated protein X participates in the formation of nascent scrapie isoform of prion protein (PrPSc), We report the identification of the site at which protein X binds to the cellular isoform of PrP (PrPC) using scrapie-infected mouse (Mo) neuroblastoma cells transfected with chimeric Hu/MoPrP genes even though protein X has not yet been isolated, Substitution of a Hu residue at position 214 or 218 prevented PrPSc formation. The side chains of these residues protrude from the same surface of the C-terminal alpha-helix and form a discontinuous epitope with residues 167 and 171 in an adjacent loop. Substitution of a basic residue at positions 167, 171, or 218 also prevented PrPSc formation: at a mechanistic level, these mutant PrPs appear to act as ''dominant negatives'' by binding protein X and rendering it unavailable for prion propagation. Our findings seem to explain the protective effects of basic polymorphic residues in PrP of humans and sheep and suggest therapeutic and prophylactic approaches to prion diseases.