Role of the integral membrane protease ZMPSTE24 in membrane protein biogenesis and virus-host cell fusion

项目摘要 真核生物蛋白质组的一个重要部分是由膜蛋白组成的，其中大部分是 在内质网（ER）处插入并组装。不同的生物物理特征， 这些膜蛋白的拓扑结构、翻译后修饰和活性需要不同的细胞特性。 途径和许多组件，以确保其适当的生物发生和功能。这个项目的目标 是为了确定锌金属蛋白酶ZMPSTE 24在膜蛋白中的新机制作用， 生物学ZMPSTE 24长期以来一直是我实验室的研究重点，对人类健康和 通过其在法尼基化的前核纤层蛋白A的蛋白水解加工中的既定作用， 核支架蛋白核纤层蛋白A。这个过程中的缺陷会导致过早衰老（早衰症）疾病。 然而，ZMPSTE 24在病毒防御中的一个有趣的新功能最近被其他人发现， 令人惊讶的是，ZMPSTE 24不需要其催化活性：ZMPSTE 24赋予针对许多 包膜病毒通过与一类称为干扰素诱导的小膜蛋白相互作用， 跨膜蛋白（IFITM 1、2和3）。IFITM通过一种机制阻断病毒-宿主细胞融合， 包括“硬化”宿主细胞膜。与IFITMs的情况一样，ZMPSTE 24的过表达也是一种抑制。 强有力地保护细胞免受包膜病毒的感染，并且在该作用中不需要其蛋白水解活性。 此外，细胞和小鼠中ZMPSTE 24的耗尽导致它们死于病毒感染。这些 这些发现将ZMPSTE 24置于细胞抵抗病毒感染的第一道防线的重要位置， 通过一般的细胞生物学作用。 在这里，我们假设ZMPSTE 24定义了一个已知或新的通路中的中心组分， 膜蛋白生物合成（插入、拓扑学、稳定性/质量控制、翻译后 修饰或寡聚化），IFITM 3作为其底物。或者，ZMPSTE 24可以促进 IFITM 3的膜以某种其他方式硬化功能，直接通过募集到IFITM 3，或 间接地通过改变脂质双层的组成或性质。这个项目代表了一个令人兴奋的 我的实验室对ZMPSTE 24的长期研究的新方向，受到ZMPSTE 24的融合的启发， 新发现的在病毒防御和COVID-19大流行中的作用。然而，我们提出的研究也 与我实验室早期关于膜蛋白拓扑结构、运输和ER质量控制的研究有关。 通过IFITM破译ZMPSTE 24的抗病毒作用提出了一个有趣的难题，我们已经准备好了 解决。我们希望这里提出的研究将揭示ZMPSTE 24在以下方面的新的基本作用： 膜蛋白生物合成或膜脂质组成或流动性。此外，深入了解 ZMPSTE 24使IFITM能够阻断病毒-宿主-细胞融合的机制最终可以被利用 开发一种新型抗病毒药物。

PROJECT SUMMARY A significant fraction of the eukaryotic proteome is composed of integral membrane proteins, most of which are inserted and assembled at the endoplasmic reticulum (ER). The diverse biophysical characteristics, topology, posttranslational modifications, and activities of these membrane proteins necessitate distinct cellular pathways and numerous components to ensure their proper biogenesis and function. The goal of this project is to define a new mechanistic role of the zinc metalloprotease ZMPSTE24 in membrane protein biology. ZMPSTE24 has long been a research focus in my laboratory and is important for human health and longevity through its established role in the proteolytic processing of farnesylated prelamin A, precursor of the nuclear scaffold protein lamin A. Defects in this processing step lead to premature aging (progeria) diseases. However, an intriguing new function for ZMPSTE24 in viral defense was recently discovered by others and surprisingly does not require its catalytic activity: ZMPSTE24 confers potent antiviral activity against many enveloped viruses through its interaction with a class of small membrane proteins called interferon-induced transmembrane proteins (IFITM1, 2, and 3). The IFITMs block virus-host cell fusion by a mechanism that involves “rigidifying” host cell membranes. As is the case for IFITMs, the overexpression of ZMPSTE24 robustly protects cells from infection by enveloped viruses, and its proteolytic activity is not needed in this role. Furthermore, depletion of ZMPSTE24 in cells and mice cause them to succumb to viral infection. These findings place ZMPSTE24 at an important position in the cell’s first line of defense against viral infection, likely through a general cell biological role. Here we hypothesize that ZMPSTE24 defines a central component in a known or new pathway for membrane protein biogenesis (insertion, topology, stability/quality control, posttranslational modification, or oligomerization), with IFITM3 as its substrate. Alternatively, ZMPSTE24 may facilitate IFITM3’s membrane rigidifying function in some other way, directly by recruitment to IFITM3, or indirectly by altering the composition or properties of the lipid bilayer. This project represents an exciting new direction in my laboratory’s long-term studies of ZMPSTE24, inspired by the convergence of ZMPSTE24’s newly discovered role in viral defense and the COVID-19 pandemic. Nevertheless, the studies we propose also relate to earlier research in my laboratory on membrane protein topology, trafficking, and ER quality control. Deciphering the antiviral role of ZMPSTE24 via the IFITMs presents an intriguing puzzle that we are primed to solve. We expect the studies proposed here will uncover a new fundamental role(s) for ZMPSTE24 in membrane protein biogenesis or membrane lipid composition or fluidity. Furthermore, insight into the mechanism whereby ZMPSTE24 enables IFITMs to block virus-host-cell fusion could ultimately be harnessed to develop a novel anti-viral drug.