Molecular basis of plasma membrane rupture in lytic cell death and its inhibition by cytoprotective agent glycine

项目总结/摘要 溶解性细胞死亡中的质膜破裂（PMR）-包括细胞凋亡、坏死性凋亡和凋亡后 继发性坏死-是一种灾难性的事件，释放出大尺寸的细胞内分子，称为损伤- 相关的分子模式（DAMP），这反过来又传播炎症反应。溶解性细胞死亡 在宿主防御病原体感染中起着重要作用，但其失调也涉及 许多炎性疾病和病理状况。PMR被认为是一个被动事件，直到最近 研究确定NINJ1负责执行这一过程。NINJ1是一种16 kDa的质膜 先前鉴定为通过同型结合介导细胞粘附的蛋白质。它有两个跨膜 螺旋和一个胞外两亲螺旋。NINJ1经历寡聚化以诱导PMR，并且NINJ1的寡聚化导致PMR。 两亲性螺旋似乎在这一过程中起重要作用。然而，一个高度相似的蛋白质NINJ2， 带有类似两亲性螺旋的质膜不诱导PMR。为了了解分子基础 NINJ1-寡聚化介导的PMR，我们使用低温电子显微镜（cryoEM）研究结构 NINJ1和NINJ2寡聚体。我们所取得的进展使我们对机械论的理解更加清晰 这个过程。然而，它也指出了更多的假设，需要进行测试，以充分了解 这一至关重要的过程。在最近的一项研究中，PMR也与甘氨酸细胞保护有关。这是 表明甘氨酸处理阻止NINJ1寡聚化，从而阻止骨髓中的PMR 衍生的巨噬细胞接受各种形式的裂解性细胞死亡刺激。我们将包括甘氨酸治疗在我们的 用于搜索触发NINJ1寡聚化的信号的假设检验。这进一步阐明了 甘氨酸细胞保护的分子基础将为更好的细胞保存策略的开发提供信息， 剂.

PROJECT SUMMARY/ABSTRACT Plasma membrane rupture (PMR) in lytic cell death—including pyroptosis, necroptosis, and post-apoptotic secondary necrosis—is a cataclysmic event that releases large-size intracellular molecules known as damage- associated molecular patterns (DAMPs), which in turn propagate the inflammatory response. Lytic cell death plays an important role in host defense against pathogen infections, but its dysregulation is also implicated in many inflammatory diseases and pathological conditions. PMR was thought to be a passive event, until a recent study identified NINJ1 to be responsible for carrying out this process. NINJ1 is a 16-kDa plasma membrane protein previously identified to be mediating cell adhesion through homotypic binding. It has two transmembrane helices and one extracellular amphipathic helix. NINJ1 undergoes oligomerization to induce PMR, and the amphipathic helix seems to play an important role in this process. However, a highly similar protein NINJ2 in the plasma membrane bearing a similar amphipathic helix does not induce PMR. To understand the molecular basis of NINJ1-oligomerization mediated PMR, we use cryogenic electron microscopy (cryoEM) to study the structures of NINJ1 and NINJ2 oligomers. The progress we have made is shedding light on a mechanistic understanding of this process. However, it also points to more hypotheses that need to be tested in order to fully understand this fundamentally important process. PMR is also linked to glycine cytoprotection in a very recent study. It was demonstrated that glycine treatment prevented NINJ1 oligomerization and thus prevented PMR in bone marrow derived macrophages receiving various forms of lytic cell death stimuli. We will include glycine treatment in our test of hypotheses for the search of signal that triggers NINJ1 oligomerization. This further elucidation of the molecular basis of glycine cytoprotection would inform the development of better cell preservation strategies or agents.