Mechanisms of innate resistance to virus infections

项目总结 人类细胞拥有许多对即将到来的病毒感染提供抵抗力的内在机制， 更好地理解这些自然过程将对我们正在进行的对抗现有的 以及新出现的病毒性疾病。干扰素诱导的跨膜蛋白(IFITM)是一种细胞因子， 有效地阻止多种病毒的融合。它们以稳定状态存在于细胞中，并积累到 在感染期间，更高、更有效的水平。IFITM3尤其能降低流感病毒的严重程度 在老鼠和人类中都有感染。然而，我们目前缺乏对IFITM3的机械性理解 防止流感病毒融合。同样，我们也不完全了解控制 细胞内IFITM3的丰度。我们试图通过两个具体的例子来弥合我们知识中的这些根本差距 这些目标将使我们更接近设计基于IFITM3的抗病毒药物的长期目标。目标一号将决定 IFITM3改变细胞膜以阻止病毒融合的分子机制。我们有新的 在IFITM3中发现了一个短的两亲性螺旋，我们证明了这是抗病毒活性所必需的。考虑到 两亲性螺旋具有很好的诱导膜弯曲的特性，我们将确定这一能力 螺旋与膜结合并改变膜，并将确定其在抑制流感和其他病毒方面的作用。 这项工作将为IFITMS以两亲性为基础的行动机制提供第一个证据。目标 2是基于我们的发现，细胞中IFITM3的稳定水平相反地受到 E3泛素连接酶NEDD4，并受肿瘤抑制基因PTEN正调控。我们之前已经 结果表明，NEDD4直接泛化IFITM3，靶向它在溶酶体中降解。我们现在就会 询问PTEN促进IFITM3水平和对流感病毒感染的抵抗力的机制。 我们将研究PTEN的哪些酶活性参与调节IFITM3，我们将确定 PTEN和NEDD4参与相同的调节回路，最后，我们将研究参与 PTEN在IFITM3介导的新生小鼠体内感染抵抗中的作用。总的来说，这些 两个独立的目标将揭示控制IFITM3活性和细胞的互补机制 富足。

PROJECT SUMMARY Human cells possess many intrinsic mechanisms that provide resistance to incoming virus infections, and a better understanding of these natural processes would be valuable in our ongoing fight against existing and emergent viral diseases. The interferon-induced transmembrane proteins (IFITMs) are cellular factors that potently block the fusion of multiple viruses. They are present in cells at steady state and also accumulate to higher, more effective levels during infection. IFITM3 in particular reduces the severity of influenza virus infections in both mice and humans. However, we currently lack a mechanistic understanding of how IFITM3 prevents influenza virus fusion. Likewise, we do not fully understand the regulatory processes controlling the abundance of IFITM3 in cells. We seek to bridge these fundamental gaps in our knowledge with two specific aims that will bring us closer to our long-term goal of designing IFITM3-based antivirals. Aim 1 will determine the molecular mechanism by which IFITM3 alters cellular membranes to prevent virus fusion. We have newly identified a short amphipathic helix within IFITM3 that we show is required for antiviral activity. Given that amphipathic helices are well characterized to induce membrane curvature, we will determine the ability of this helix to associate with and alter membranes, and will define its role in inhibiting influenza and other viruses. This work will provide the first evidence for an amphipathicity-based mechanism of action for the IFITMs. Aim 2 is based on our discoveries that the steady state level of IFITM3 in cells is conversely negatively regulated by the E3 ubiquitin ligase NEDD4 and positively regulated by the tumor suppressor PTEN. We have previously shown that NEDD4 directly ubiquitinates IFITM3, targeting it for degradation in lysosomes. We will now interrogate the mechanism by which PTEN promotes IFITM3 levels and resistance to influenza virus infection. We will examine which enzymatic activity of PTEN is involved in regulating IFITM3, we will determine whether PTEN and NEDD4 are involved in the same regulatory circuit, and finally, we will examine the involvement of PTEN in IFITM3-mediated resistance to infection in vivo using newly generated mouse models. Overall, these two independent aims will reveal complementary mechanisms that control IFITM3 activity and cellular abundance.