Biology and Therapeutic Value of Mammalian Aph-1 Homologues

哺乳动物 Aph-1 同源物的生物学和治疗价值

• 批准号: 6968997
• 负责人: PHILIP C WONG
• 金额: $ 33.51万
• 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/6968997
• 关键词: Alzheimer' s disease; amyloid proteins; amyloidosis; aspartic endopeptidases; developmental genetics; disease /disorder model; endopeptidases; enzyme complex; genetically modified animals; laboratory mouse; presenilin; protein localization; protein protein interaction

Presenilins (PS) form high molecular weight complexes with several other transmembrane proteins, termed NCT, Aph-1 and Pen-2 that are critical for generation of functional gamma-secretase complexes. However, the exact roles of these proteins, particularly for Aph-1 in mammals where two homologous genes exist, in regulation of gamma-secretase complex assembly remain uncertain. Although recent data support the notion that PS, NCT, Aph-1 and Pen-2 comprise the minimal gamma-secretase complex, the precise mechanism whereby these four components are assembled into the final active complex remain undefined. An interesting question is why there exist two mammalian Aph-1 genes, namely Aph-1a and Aph-1b, encoding three Aph-1 homologues called Aph-1aL, Aph-1aS and Aph-1b. Based on our recent find ings that the phenotype of Aph-1a null embryos resemble but not identical to those of Notch1 null or NCT null embryos, we hypothesize that Aph-1a is the principal mammalian Aph-1 homologue in presenilin-dependent gamma-secretase complexes required for embryonic development and that Aph-1 homologues are developmentally regulated. Thus, we plan in Aim 1 to address these issues by generation and characterization of Aph-1a null, Aph-1b null and Aph-1a+Aph-1b null mice. Based on our recent findings that the deletion of Aph-1a significantly reduces the levels of mature and immature NCT coupled with the finding that Aph-1 and NCT physically interact, we hypothesize that Aph-1 and NCT are required to regulate the stability of each other to form a stable precomplex for assembling PS and Pen-2. In such a model, we suggest that the three mammalian Aph-1 homologues (Aph-1aL, Aph-1aS and Aph-1b) define a set of six distinct functional gamma-secretase complexes. To test this model, we will generate and characterize a series of mice harboring different combination of Aph-1a and Aph-1b knockout allele and fibroblasts derived from these mice in Aim 2. Since we showed that Aph-1b null mice are viable and there is reduction in levels of PS and Pen-2 in brains of Aph-1-/- mice, we will test whether deletion of Aph-1b is sufficient to ameliorate Abeta deposition in brains of mutant APP;PS1 mice in Aim 3. Taken together, studies proposed here will address important mechanistic questions regarding physiological roles of mammalian Aph-1 homologues and critically evaluating Aph-1a and Aph-1b as therapeutic targets in efforts to ameliorate Abeta amyloidosis in AD.

早老素（PS）与其他几种跨膜蛋白形成高分子量复合物，称为NCT， Aph-1和Pen-2，这对于生成功能性γ -分泌酶复合物至关重要。然而，这些蛋白，特别是在哺乳动物中存在两个同源基因的Aph-1，在调节γ -分泌酶复合物组装中的确切作用仍然不确定。尽管最近的数据支持PS、NCT、Aph-1和Pen-2组成最小γ -分泌酶复合物的观点，但确切的机制是