NORMAL AND PATHOLOGIC CELLULAR RESPONSES TO PRION PROTEIN EXPRESSION

朊病毒蛋白（PrP）是一种脑糖蛋白， 在羊瘙痒病的发病机制中， 动物的疾病，类似于人类的某些疾病（1）。 我们 对PrP在无细胞系统中的生物发生的研究发现了一种新的 新生PrP的拓扑结构可以在 内质网产生跨膜或分泌 新生多肽的形式（2）。 我们假设这种改变 PrP的拓扑结构可能是疾病过程的中心特征， 痒病 为了支持这一点，突变之间惊人的相关性 影响PrP拓扑结构和那些赋予疾病的 （3，4）。 最近，我们发现，在非洲爪蟾卵母细胞，PrP 拓扑结构仅限于分泌形式，即使卵母细胞可以 识别PrP序列中的信息， 当这些编码区被工程化时， 进入其他蛋白质的编码区，或者当 PrP被插入破坏。 因此，PrP的特征不同于那些 在无细胞系统中的直接拓扑结构，似乎限制了 多肽的两种可能的拓扑表型之一， 细胞 在这里，我们建议研究这种现象的拓扑限制 作为了解细胞对PrP反应的项目的一部分。 一是 将描述这种限制并确定其分子基础。 其次，使用拓扑限制作为生理参数，我们将 测定细胞对外源性PrP呈递和 内源性PrP表达。 我们将确定拓扑限制是否 由细胞表面的信号事件控制，并试图 开发一个无细胞系统，显示其特性。 最后我们 应确定是否可以通过产生新的基因产物来终止 在羊瘙痒病的发展过程中。 如果事实证明是这样，我们将 克隆负责的基因。 通过这种方式，一种新的细胞生物学观察 涉及PrP将被描述并吸收现有知识 蛋白质运输和羊瘙痒病发病机制的影响。 此类调查 详细的细胞反应PrP应该提供重要的 与宿主防御朊病毒疾病相关的信息。 最后， 这种方法可以让分子深入了解可能的方式， 可以防止PrP致病表型的生物发生， 改变、对抗或控制。

The prion protein (PrP) is a brain glycoprotein which has been implicated in the pathogenesis of scrapie, a progressive degenerative neurologic disease of animals which resembles certain diseases of humans (1). Our studies on the biogenesis of PrP in cell-free systems have found a novel mechanism by which the topology of nascent PrP can be regulated at the endoplasmic reticulum to generate either a transmembrane or a secretory form of the nascent polypeptide (2). We have hypothesized that alteration of the topology of PrP may be a central feature of the disease process in scrapie. In support of this, a striking correlation between mutations which affect PrP topology and those which confer disease has been observed (3, 4). Recently, we have discovered that, in Xenopus oocytes, PrP topology is restricted to the secretory form, even though oocytes can recognize information within the sequence of PrP to direct both transmembrane and secretory forms when those coding regions are engineered into the coding regions of other proteins or when the native structure of PrP is disrupted by insertions. Thus, features of PrP distinct from those which direct topology in cell-free systems, appear to restrict the polypeptide to one of its two possible topologic phenotypes in living cells. Here we propose to study this phenomenon of topologic restriction as part of a program to understand cellular responses to PrP. First, we shall characterize this restriction and determine its molecular basis. Second, using topologic restriction as a physiologic parameter, we shall assay the cellular response to both exogenous PrP presentation and endogenous PrP expression. We will determine if topologic restriction is controlled by signalling events from the cell surface and attempt to develop a cell-free system displaying its characteristics. Finally, we shall determine if it can be terminated by new gene products produced during the progression of scrapie. If this proves to be the case, we will clone the responsible genes. In this way, a new cell biologic observation involving PrP will be characterized and assimilated with existing knowledge on both protein trafficking and scrapie pathogenesis. Such investigation in detail of the cellular response to PrP should provide important information relevant to host defense against prion disease. Eventually, this approach may allow molecular insight into possible ways in which biogenesis of the disease-causing phenotype of PrP can be prevented, altered, countered or controlled.