Functional role of transmembrane domain interactions and intramembrane cleavage of microglial innate immunity receptors

小胶质细胞先天免疫受体跨膜域相互作用和膜内裂解的功能作用

• 批准号: 280695974
• 负责人: Professor Dr. Christian Haass
• 金额: --
• 依托单位: Munich Cluster for Systems Neurology (SyNergy)
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/280695974?language=en
• 关键词: Functional; role; transmembrane; domain; interactions

This project addresses a central question of this research unit, namely what defines a substrate to be cleaved by intramembrane cleaving proteases. Although many substrates of gamma-secretase have been identified until today, we still do not know the exact determinants, which make a transmembrane domain of a type 1 protein accessible for gamma-secretase processing or not. This question is not only of academic interest, but is also of greatest importance for therapeutic gamma-secretase inhibition in Alzheimer's disease patients. TREM2 processing is highly relevant for the physiological activity of microglia cells, and mutations, which have been linked to Alzheimer's disease and many other neurodegenerative disorders, were shown in our previous work to affect proteolytic processing of TREM2 and the phagocytic activity of microglia cells. TREM2 binds in vivo to TYROBP (DAP12). Whereas unbound TREM2 appears to be a good substrate for intramembrane proteolysis after shedding, DAP12, which lacks a N-terminal domain, whose removal appears to be an absolute requirement for all gamma-secretase substrates, may not be cleaved by gamma-secretase. DAP12 is known to form a highly stable homodimer. By this, we have potential substrates available, the interaction and processing of which play an essential role in microglial phagoytosis. Thus, by investigating the physiologically and pathologically highly relevant TREM2/DAP12 and DAP12/DAP12 interactions as an in vivo model we can address the questions if interactions of transmembrane domains influence intramembrane proteolysis and if transmembrane domains, which occur under physiological conditions as dimers, can be cleaved by gamma-secretase. We hypothesize that the tight interaction of the transmembrane domains of TREM2 and DAP12 may prevent or even regulate subsequent intramembrane proteolysis. This may also further affect signaling processes, which are required to initiate microglial phagocytosis. Moreover, we may be able to identify DAP12 as a gamma-secretase non-substrate although it apparently fulfills all requirements of a bona fide gamma-secretase substrate. DAP12 will then be used as a scaffold to confirm requirements of gamma-secretase substrates identified by the members of the research unit. Thus our project provides a naturally occurring biologically highly relevant test system to address central questions of this research unit.Taken together, we will elucidate determinants for gamma-secretase-cleavage (goal 1), as well as the role of transmembrane domain dimerization for intramembrane cleavage and signaling (goal 2) in vivo.

该项目解决了该研究单位的一个核心问题，即什么定义了膜内切割蛋白酶切割的底物。 尽管直到今天，γ-分泌酶的许多底物已经被鉴定出来，但我们仍然不知道确切的决定因素，这些决定因素使得 1 型蛋白的跨膜结构域是否能够被γ-分泌酶加工。 这个问题不仅具有学术意义，而且对于阿尔茨海默病患者的γ-分泌酶抑制治疗也非常重要。 TREM2 加工与小胶质细胞的生理活性高度相关，我们之前的工作表明，与阿尔茨海默病和许多其他神经退行性疾病相关的突变会影响 TREM2 的蛋白水解加工和小胶质细胞的吞噬活性。 TREM2 在体内与 TYROBP (DAP12) 结合。 尽管未结合的 TREM2 似乎是脱落后膜内蛋白水解的良好底物，但缺少 N 末端结构域的 DAP12（其去除似乎是所有 γ 分泌酶底物的绝对要求）可能不会被 γ 分泌酶切割。 DAP12 已知可形成高度稳定的同型二聚体。 通过这种方式，我们获得了潜在的底物，其相互作用和加工在小胶质细胞吞噬作用中发挥着重要作用。 因此，通过研究生理和病理上高度相关的 TREM2/DAP12 和 DAP12/DAP12 相互作用作为体内模型，我们可以解决跨膜结构域的相互作用是否影响膜内蛋白水解以及在生理条件下作为二聚体出现的跨膜结构域是否可以被 γ-分泌酶裂解的问题。 我们假设 TREM2 和 DAP12 跨膜结构域的紧密相互作用可能阻止甚至调节随后的膜内蛋白水解。 这也可能进一步影响启动小胶质细胞吞噬作用所需的信号传导过程。 此外，我们也许能够将 DAP12 鉴定为 γ 分泌酶非底物，尽管它显然满足真正的 γ 分泌酶底物的所有要求。然后，DAP12 将用作支架，以确认研究单位成员确定的 γ-分泌酶底物的需求。因此，我们的项目提供了一个自然发生的生物学高度相关的测试系统来解决该研究单位的核心问题。总之，我们将阐明γ-分泌酶裂解（目标1）的决定因素，以及体内跨膜域二聚化对膜内裂解和信号转导（目标2）的作用。