Roles of PS1 in y-secretase integrity and trafficking

描述（由申请人提供）：早老素（PSs, PS1/PS2）的基因突变是早发性家族性阿尔茨海默病（FAD）的主要原因。PS被认为是γ -分泌酶复合物的催化成分。γ -分泌酶介导淀粉样蛋白前体蛋白（APP）的膜内裂解，在阿尔茨海默病（AD）中产生致病性小肽Abeta。到目前为止，PSs、Nicastrin （Net）、Aph-1和PEN-2已被确定为其基本成分。它们是完整的膜蛋白，在内质网中合成并通过分泌途径传播。PS1已被证明在细胞内运输γ -分泌酶组分Net中发挥作用。在我的初步研究中，我发现在没有PS的情况下，PEN-2保留在ER中，半衰期更短，这表明PEN-2的转运和稳定性需要PS，可能是通过物理相互作用。此外，某些γ分泌酶抑制剂治疗可显著增加细胞表面结合的PS1和PEN-2，但不增加Net。这是高选择性强效γ -分泌酶抑制剂首次被证明对γ -分泌酶成分的运输有不同的影响。由于这些γ -分泌酶抑制剂已被证明与PS1物理结合，我假设它们对γ -分泌酶成分的影响是由PS1介导的。事实上，我的初步数据进一步证明，抑制剂诱导的PEN-2细胞表面积累依赖于PS1。基于这些结果，我认为PS及其相关的γ -分泌酶活性对于维持γ -分泌酶复合物的完整性和适当的细胞内运输至关重要。因此，这项提议的目的是检验这一假设。PS1突变（Specific Aim1）改变PS1功能对γ -分泌酶复合物完整性和运输特性的影响将被系统地研究。这些研究将揭示PS1突变背后的细胞扰动机制，包括导致AD发病的机制。此外，详细分析γ -分泌酶抑制剂如何影响γ -分泌酶组分的运输（Specific Aim 2），特别是它们是否对PS1突变体具有相同的作用（Specific Aim 3），应该为药物设计提供有价值的信息，以减缓并最终预防AD。

DESCRIPTION (provided by applicant): Genetic mutations in presenilins (PSs, PS1/PS2) account for the majority of early-onset familial Alzheimer's disease (FAD). PS is the putative catalytic component of gamma-secretase complex. Gamma-secretase mediates the intramembrane cleavage of amyloid precursor protein (APP) that generates pathogenic small peptide Abeta in Alzheimer's disease (AD). So far, PSs, Nicastrin (Net), Aph-1, and PEN-2 have been identified as its essential components. They are integral membrane proteins that are synthesized in ER and travel through the secretory pathway. PS1 has been shown to play roles in intracellular trafficking of gamma-secretase component Net. In my preliminary studies, I found that in the absence of PS, PEN-2 is retained in the ER with a shorter half-life, suggesting PS is required for the trafficking and stability of PEN-2, probably via physical interaction. Furthermore, certain gamma-secretase inhibitor treatment results in markedly increased cell surface bound PS1 and PEN-2, but not Net. This is the first time that highly selective potent gamma-secretase inhibitors has been shown to differentially affect the trafficking of gamma-secretase components. Since these gamma-secretase inhibitors have been shown to physically bind PS1,I hypothesized that their effect on the gamma-secretase components is mediated by PS1. Indeed, my preliminary data further demonstrated that the inhibitor-induced cell surface accumulation of PEN-2 depends on PS1. Based on these results, I propose that PS and its associated gamma-secretase activity are critical for maintaining the integrity and proper intracellular trafficking of the gamma-secretase complex. The objective of this proposal is therefore to test this hypothesis. The impact of altered PS1 function by PS1 mutation (Specific Aim1) on the integrity and trafficking property of gamma-secretase complex will be systemically examined. These studies will reveal the mechanism of the cellular perturbation underlying PS1 mutations, including which results in pathogenesis of AD. Furthermore, detailed analysis of how gamma-secretase inhibitors affect the trafficking of gamma-secretase components (Specific Aim 2), especially whether they have the same effect toward PS1 mutants (Specific Aim 3) should provide valuable information for drug design to slow and ultimately prevent AD.