Mechanisms of Virus Entry into Cells and Antiviral Barriers Limiting Entry

我们在2020年发表了两篇关于该项目的文章（Ahi et al., mBio 11: e03088- 19,2020; Rahman et al., eLife 9: e58537, 2020）。我们的工作为IFITM蛋白及其所属的扩展CD225蛋白家族的功能提供了广泛的见解，并将为开发新的抗病毒疗法提供杠杆作用。这个项目现在的重点是了解其他由人类编码的CD225蛋白的抗病毒潜力（或缺乏抗病毒潜力），包括IFITM5。IFITM5参与骨形成，但不参与抗病毒免疫。我们发现IFITM5不像其免疫相关的表亲（IFITM1、IFITM2和IFITM3）那样二聚体化，这与影响膜流动性的能力下降有关。因此，我们提供了相关基因如何在复制后分化以及抗病毒活性如何获得（或在这种情况下失去）的理解。由于大多数IFITM蛋白具有形成同型二聚体的能力，我们现在正在表征异源二聚体如何促进其各自的功能。我们正在使用无偏倚的蛋白质组学和共免疫沉淀，以及基于fret的显微镜来研究IFITM蛋白与其他细胞因子的相互作用，我们正在确定这些相互作用对其已知的抗病毒功能的影响程度。这些结果也将为该蛋白家族所扮演的肿瘤发生作用提供见解。

We published two articles pertaining to this project in 2020 (Ahi et al., mBio 11: e03088-19, 2020; Rahman et al., eLife 9: e58537, 2020). Our work provides extensive insight into the function of IFITM proteins as well as the extended CD225 protein family to which they belong and will provide leverage for the development of new antiviral therapies. The focus of this project now is to understand the antiviral potential (or lack thereof) of other CD225 proteins encoded by humans, including IFITM5. IFITM5 is involved in bone formation and is not known to participate in antiviral immunity. We found that IFITM5 does not dimerize like its immune-related cousins (IFITM1, IFITM2, and IFITM3) and this is associated with a decreased capacity to impact membrane fluidity. Therefore, we provide an understanding of how related genes diverge following duplication and how antiviral activity is gained (or in this case, lost). Since most IFITM proteins possess the capacity to form homodimers, we are now in the process of characterizing how heterodimers contribute to their respective function. We are using unbiased proteomics and co-immunoprecipitation, and FRET-based microscopy to study the interaction of IFITM proteins with other cellular factors, and we are determining to what extent these interactions are consequential for their known antiviral functions. These results will also provide insight into the poorly characterized tumorigenic roles played by this family of proteins.