NORMAL AND PATHOLOGIC CELLULAR RESPONSES TO PRION PROTEIN EXPRESSION

Prion蛋白(PrP)是一种脑糖蛋白，已被认为与 在瘙痒病的发病机制中，一种进行性退行性神经系统疾病 类似于人类某些疾病的动物疾病(1)。我们的 对PrP在无细胞体系中的生物发生的研究发现了一个新的 新生的PrP的拓扑结构可以在 产生跨膜或分泌物的内质网 新生多肽的形式(2)。我们已经假设了这种变化 PrP的拓扑结构的改变可能是疾病过程的中心特征 瘙痒病。支持这一点的是，突变之间的显著关联 已经观察到哪些影响PrP拓扑结构，哪些与疾病有关 (3、4)。最近，我们发现，在非洲爪哇卵母细胞中，PrP 拓扑结构仅限于分泌形式，即使卵母细胞可以 识别PrP序列中的信息以引导两者 当这些编码区被工程时的跨膜和分泌形式 进入其他蛋白质的编码区，或者当天然结构 PRP被插入打乱。因此，PrP的特征有别于 在无单元系统中的直接拓扑结构，似乎限制了 多肽与其在生物中的两种可能的拓扑表型之一 细胞。在这里，我们建议研究这种拓扑限制现象 作为了解PrP细胞反应的计划的一部分。首先，我们 应表征这种限制并确定其分子基础。 第二，使用拓扑限制作为一个生理参数，我们将 检测细胞对外源性PrP递呈和 内源性PrP表达。我们将确定拓扑限制是否为 由来自细胞表面的信号事件控制，并尝试 开发一种显示其特点的无细胞系统。最后，我们 应确定是否可以通过生产新的基因产品来终止 在瘙痒病的发展过程中。如果事实证明是这样的，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的特征将被描述并与现有知识同化 蛋白质转运和瘙痒病发病机制的关系。这样的调查 关于PrP的细胞反应的详细信息应该提供重要的 与宿主防御Pron病相关的信息。最终， 这种方法可能允许分子洞察可能的方式 可以防止PrP致病表型的生物发生， 改变、对抗或控制的。

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.