Nicastrin: Physiological Role and Therapeutic Target Validation

尼卡斯特林：生理作用和治疗靶点验证

• 批准号: 6968996
• 负责人: PHILIP C WONG
• 金额: $ 28.48万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2010-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6968996
• 关键词: Alzheimer' s disease; amyloid proteins; aspartic endopeptidases; behavior test; biological signal transduction; developmental genetics; disease /disorder model; embryo /fetus tissue /cell culture; enzyme activity; enzyme complex; genetically modified animals; glycoproteins; growth /development; laboratory mouse; membrane proteins; presenilin; protease inhibitor; protein localization; protein metabolism; protein protein interaction

Nicastrin (NCT), a type I transmembrane glycoprotein which forms high molecular weight complexes with presenilins (PS), is an essential component of the multimeric gamma-secretase complex required for both gamma-secretase activity and APP trafficking. Our recent studies suggest that NCT, with its large ectodomain, may be a potential therapeutic target for AD. Because PS/gamma-secretase activity is required for a variety of essential signaling pathways coupled with our recent finding that cognitive deficits occur in BACE1 null mice, complete inhibition of either secretase activity may not be completely free of mechanism-based toxicity. To minimize any potential toxicity, it may be beneficial to modulate both beta- and gamma-secretase activity such that a significant amelioration of Abeta deposition occurs without affecting other critical signaling pathways. Since our recent studies showed that Abeta deposits are sensitive to the dosage of both NCT and BACE1, we hypothesize that Abeta deposits could be ameliorated by decreasing levels of NCT and BACE1. As proof of principal, we will examine in Aim 1 whether partial reductions of NCT or both NCT and BACE1 will reduce Abeta burden in brains of mutant APP;PS1 mice. Based on our recent findings, we hypothesize that NCT and Aph-1 are required to regulate the stability of each other to form a stable pre-complex for assembly of PS and Pen-2. Since our recent studies indicated that PS1-/-;NCT+/- embryos exhibited a more severe phenotype as compared to PS1-/-;NCT+/- embryos, we hypothesize that this is due to reduced level of PS2-depenedant gamma-secretase complex in PST-/-;NCT+/- embryos. In Aim 2 we will to test whether PS2-dependent gamma-secretase activity is sensitive to the dosage of NCT in the absence of PS1. In addition, we plan to test whether partial reduction of both NCT and PS1 can further reduce the level of Abeta without altering Notch signaling. Positive outcomes from these studies provide support for the view that a combination of NCT- and PS-specific inhibitors may be a useful therapeutic strategy. In Aim 3, we will examine the impact of the absence of NCT in adult peripheral tissues by generation of transgenic mice expressing NCT under the control of the neuronal-specific Thy1 promoter to genetically complement the embryonic lethality of NCT-/- mice. Results from these studies will have important implications for understanding the biology of NCT and development of anti-Abeta therapeutic strategies in AD.

Nicastrin（NCT）是与早老素（PS）形成高分子量复合物的I型跨膜糖蛋白，是γ-分泌酶活性和APP运输所需的多聚体γ-分泌酶复合物的重要组分。我们最近的研究表明，NCT，其大的胞外域，可能是一个潜在的治疗AD的目标。由于PS/γ-分泌酶活性是多种基本信号传导途径所必需的，再加上我们最近发现BACE 1基因敲除小鼠中发生认知缺陷， 任一分泌酶活性抑制可能不是完全没有基于机制的毒性。为了使任何潜在的毒性最小化，调节β-和γ-分泌酶活性可能是有益的，使得在不影响其他关键信号传导途径的情况下发生A β沉积的显著改善。由于我们最近的研究表明，Abeta沉积物对NCT和BACE 1的剂量敏感，因此我们假设可以通过降低NCT和BACE 1的水平来改善Abeta沉积物。作为原理的证明，我们将在目标1中检查NCT的部分减少或NCT和BACE 1两者的部分减少是否会减少突变型APP;PS1小鼠脑中的Abeta负荷。基于我们最近的研究结果，我们假设NCT和Aph-1需要调节彼此的稳定性，以形成用于PS和Pen-2组装的稳定的前复合物。由于我们最近的研究表明，与PS1-/-;NCT +/-胚胎相比，PS1-/-;NCT +/-胚胎表现出更严重的表型，我们推测这是由于PS2依赖的γ分泌酶复合物水平降低所致。 PST-/-;NCT+/-胚胎。在目的2中，我们将测试在没有PS1的情况下，PS2依赖性γ-分泌酶活性是否对NCT的剂量敏感。此外，我们计划测试NCT和PS1的部分减少是否可以在不改变Notch信号的情况下进一步降低Abeta的水平。这些研究的积极结果为NCT和PS特异性抑制剂的组合可能是一种有用的治疗策略的观点提供了支持。在目标3中，我们将通过产生在神经元特异性Thy 1启动子控制下表达NCT的转基因小鼠来检查成年外周组织中NCT缺失的影响 以在基因上补充NCT-/-小鼠的胚胎致死性。这些研究的结果将对理解NCT的生物学和AD中抗Abeta治疗策略的开发具有重要意义。