Urokinase-type plasminogen activator and Alzheimer's

描述（由申请人提供）：导致阿尔茨海默病（AD）易感性的遗传因素对我们了解和早期诊断该疾病至关重要。10号染色体区域包含至少一个迟发性阿尔茨海默病的易感位点，并且与淀粉样蛋白b （ADi）血浆水平升高有关。编码尿激酶型纤溶酶原激活物（uPA）的基因就在这个受影响的区域内。体外和体内AB负荷小鼠模型中，经AB处理的神经元均可诱导UPA。此外，uPA将纤溶酶原转化为活性蛋白酶纤溶酶，以生理效率降解非聚集和聚集的AB。综上所述，ADi诱导了uPA，而uPA反过来又会导致AB的降解，这表明一个清除AB聚集体的自我调节系统。考虑到这些数据，我们假设10号染色体位点包含uPA多态性，该多态性调节uPA促进AD清除的能力。为了评估这一假设，我们建议(i)确定与阿尔茨海默病分离的uPA多态性。在初步工作中，我们已经确定了两种uPA多态性，它们与AD易感性显著分离，并且处于强烈的连锁不平衡状态，包括(i) uPA内141位的pro被leu取代，这改变了uPA酶原与聚集纤维蛋白的结合；（ii）两个碱基对3'的SNP与ap - 1位点的结合，已知这对uPA诱导至关重要。我们还建议（ii）通过比较每种基因型纯合的个体，了解高危uPA单倍型的可能作用，以获得阿尔茨海默病的相关临床和神经病理学标记；（iii）评估与AD风险相关的uPA多态性对uPA表达和功能的影响；（iv）通过量化野生型或基因缺乏uPA的小鼠体内AB积累，评估uPA在体内AB清除中的作用。

DESCRIPTION (provided by applicant): Genetic factors that contribute to Alzheimer's disease (AD) susceptibility are critical to our understanding and early diagnosis of the disease. A chromosome 10 region contains at least one susceptibility locus for late onset Alzheimer's disease, and is associated with increased amyloid-B (ADi) plasma levels. The gene encoding urokinase-type plasminogen activator (uPA) is within this implicated region. UPA is induced by AB-treated neurons in vitro and in the Hsiao mouse model of AB burden in vivo. Moreover, uPA converts plasminogen to the active protease plasmin, which degrades both nonaggregated and aggregated AB with physiologic efficiency. In summation, ADi induces uPA, which can in turn lead to AB degradation, suggesting a self-regulated system for clearance of AB aggregates. Considering these data overall we hypothesize that the chromosome 10 loci includes a uPA polymorphism(s) that modulates uPA's ability to contribute to AD clearance. To evaluate this hypothesis, we propose to (i) identify uPA polymorphisms that segregate with Alzheimer's disease. In preliminary work we have identified two uPA polymorphisms that significantly segregate with AD susceptibility and are in strong linkage disequilibrium, including (i) a substitution of leu for pro at position 141 within uPA, which alters binding of the uPA zymogen to aggregated fibrin and (ii) a SNP two basepairs 3' to an AP-I site that is known to be critical for uPA induction. We also propose to (ii) Gain insight into the possible role of the at-risk uPA haplotype by comparing individuals homozygous for each genotype for relevant clinical and neuropathologic markers of Alzheimer's disease, (iii) Evaluate the effect of the uPA polymorphisms associated with AD risk on uPA expression and function, and (iv) Evaluate the role of uPA in AB clearance in vivo by quantifying AB accumulation in mice that are wildtype or genetically deficient for uPA. Overall, the focused approach proposed here will (i) directly evaluate the possible role of uPA polymorphisms as a risk factor(s) for Alzheimer's disease, and (ii) provide insights into possible mechanisms underlying differential uPA actions. These studies are significant in that the identification of additional genetic risk factors for Alzheimer's disease will aid in early AD diagnosis, and thereby facilitate drug discovery by identifying patients at high risk for AD prior to symptomology. Moreover, by evaluating possible mechanisms underlying the enhanced susceptibility to Alzheimer's disease, these studies may lead to the discovery of novel insights into the molecular mechanisms underlying Alzheimer's disease, and thereby suggest new therapeutic approaches.