Mechanisms of APP ectodomain function

项目总结 细胞膜蛋白调节对生物体健康至关重要的多种细胞过程。这个 胞外结构域在全长受体的配体结合和信号转导中起关键作用。此外, 大约2%的细胞表面蛋白经历胞外结构域的脱落来释放它们的胞外结构域。 胞外结构域的脱落可能终止全长受体的功能和/或导致产生 一种可溶的诱饵受体或活性配体。淀粉样前体蛋白(APP)，一种1型膜蛋白 阿尔茨海默病的病因学中心是这样一种经历胞外结构域的细胞表面蛋白 脱落以产生各种可溶性APP(Sapp)片段。尽管应用程序ectodomain的影响是已知的 细胞和认知功能及其在疾病中的潜在应用--精确的分子机制 由于该领域的焦点是淀粉样蛋白，因此APP胞外结构域的调节功能在很大程度上仍然是个谜。 APP的β区域。因此，该实验室的目标是阐明细胞外的正常生理功能。 淀粉样前体蛋白的结构域。我们的方法旨在解决以下方面的机制差距 利用我们最近的发现，Sapp作为GABA B型受体的配体发挥作用 (GABR)和我们最近鉴定的线粒体磷酸甘油变位酶家族成员5(PGAM5) 丝氨酸/苏氨酸蛋白磷酸酶，作为APP胞外结构域的一个新的候选相互作用元件。一行 研究将阐明非神经细胞对Sapp和GABAB受体调节的细胞反应， 确定Sapp和GABA B受体相互作用下游的信号通路，并确定 SAPP对GABAB受体信号的正向调节机制。第二条研究路线 将调查APP和PGAM5进入的细胞条件和亚细胞隔间 接触，APP和PGAM5相互作用的分子基础(即结合亲和力，关键结合结构域)， 以及PGAM5对APP磷酸化和蛋白降解过程的影响。这些研究中的工作 将产生蛋白质-蛋白质相互作用潜在的分子机制的基本知识 以及这些相互作用在不同细胞类型中的细胞后果。

PROJECT SUMMARY Cell membrane proteins regulate a multitude of cellular processes that are vital for organismal health. The extracellular domain is critical for ligand binding and signal transduction of the full-length receptor. In addition, approximately 2% of cell surface proteins undergo ectodomain shedding to release their extracellular domain. Ectodomain shedding may terminate the function of the full-length receptor and/or lead to the generation of either a soluble decoy receptor or an active ligand. The Amyloid Precursor Protein (APP), a type 1 membrane protein central to the etiology of Alzheimer’s disease, is one such cell surface protein that undergoes ectodomain shedding to generate various soluble APP (sAPP) fragments. Despite the known effects of the APP ectodomain on cellular and cognitive functions and the potential applications to disease, the precise molecular mechanisms mediating the function of APP ectodomain remains largely enigmatic due to the focus of the field on the Amyloid- β region of APP. Thus, the goal of the lab is to elucidate the normal physiological functions of the extracellular domain of the Amyloid Precursor Protein. Our approaches are designed to address the mechanistic gaps in knowledge by leveraging our recent discovery that sAPP functions as a ligand for the GABA type B Receptor (GABABR) and our recent identification of Phosphoglycerate Mutase Family Member 5 (PGAM5), a mitochondrial serine/threonine protein phosphatase, as a novel candidate interactor of the APP ectodomain. One line of research will elucidate the cellular responses of non-neuronal cells to sAPP and GABA B Receptor modulation, identify signaling pathways downstream of the sAPP and GABA B Receptor interaction, and determine mechanisms involved in the positive regulation of GABA B Receptor signaling by sAPP. A second line of research will investigate the cellular conditions and subcellular compartments in which APP and PGAM5 come into contact, the molecular basis of the APP and PGAM5 interaction (i.e. binding affinities, critical binding domains), and the consequences of PGAM5 on APP phosphorylation and proteolytic processing. The work in these studies will generate fundamental knowledge of the molecular mechanisms underlying the protein-protein interactions of the APP ectodomain and the cellular consequences of these interactions across different cell types.