RAPID: Revealing the intermolecular interactions between the SARS-CoV-2/COVID-19 fusion peptide and the host cell membrane that underlie its flexibility in host tropism

冠状病毒是一种有膜包裹的包装，表面装饰着从其表面突出的“尖刺”。这些刺突与宿主细胞相互作用以启动该细胞的感染。冠状病毒传播到其他细胞的能力取决于刺突与其靶宿主细胞膜的相互作用程度。控制这种相互作用的刺突部分被称为“融合肽”，它的工作是插入宿主细胞膜，启动将其遗传货物运送到细胞中。然而，融合肽如何与膜相互作用的细节仍然未知。 在本项目中，将研究融合肽与模拟不同种类宿主细胞的膜表面之间的各种相互作用。 该信息将提供对融合肽和宿主细胞的特征的深入了解，所述融合肽和宿主细胞促进它们的相互作用，并最终促进感染和病毒传播到新宿主。 随着对这种病毒适应新宿主的关键相互作用背后的科学更好的理解，我们将更好地了解这种病毒是如何传播的，并最终有能力制定阻止它的策略。这些基本信息有可能使新的方法设计针对融合肽的抗病毒药物。鉴于融合肽在冠状病毒家族中高度保守，这些研究将直接适用于所有冠状病毒，包括导致COVID-19的冠状病毒。冠状病毒传播能力的一个关键决定因素是它如何与其靶宿主膜相互作用。对于冠状病毒，进入宿主细胞是由从其膜包膜突出的单个糖蛋白介导的，称为刺突（S）。在S中，直接与膜相互作用的区域称为融合肽，FP。正是FP与宿主膜的物理化学相互作用将其锚定，从而使膜发生必要的变形，导致病毒基因组递送到细胞中。因此，在最基本的水平上理解FP相互作用将有助于制定限制这些相互作用以阻止感染传播的策略。 预计这些信息将有助于预测未来可能对人类构成威胁的新菌株的特征。本项目的目的是测量和确定特定的分子间相互作用，负责FP插入膜。具体而言，本项目将：1）使用原子力显微镜和生物膜模型的单分子力测量来阐明控制FP疏水相互作用的因素，以及2）使用圆二色性和等温量热法来表征FP的结构-功能关系，以将特定的相互作用与氨基酸序列和宿主表面性质相关联。该项目的智力价值在于发现宿主膜化学或FP的氨基酸序列的变化如何调节疏水相互作用并最终影响对感染传播至关重要的活性。该项目更广泛的影响是提供信息，使新的方法来设计抗病毒药物，以及确定基本的设计规则，告知FP如何促进与特定化学膜的相互作用，以预测宿主对感染的易感性。鉴于FP在整个CoV家族中高度保守，这些研究将直接适用于所有CoV，包括那些尚未出现的CoV。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

Coronavirus is a membrane-enveloped package decorated with “spikes” that protrude from its surface. These spikes interact with the host cell to initiate infection of that cell. The ability of coronavirus to spread to other cells depends on how well the spike interacts with its target host membrane. The part of the spike that controls this interaction is called the “fusion peptide” and its job is to insert into the host membrane to initiate the delivery its genetic cargo into the cell. However, the specifics of how the fusion peptide interacts with the membrane is still not known. In this project, various interactions between the fusion peptide with membrane surfaces that mimic different kinds of host cells will be studied. This information will provide insight into the characteristics of both the fusion peptide and the host cell that promotes their interaction, and ultimately, infection and viral transmission to new hosts. With a better understanding of the science behind this critical interaction for virus adaptation to new hosts, we will be better informed about how this virus spreads and ultimately equipped to develop strategies to stop it. This fundamental information has the potential to enable fresh approaches to the design of antiviral drugs that target the fusion peptide. Given that the fusion peptide is highly conserved across the coronavirus family, these studies will be directly applicable to all coronaviruses, including the coronavirus that causes COVID-19.A key determinant of the ability of coronavirus to spread is how it interacts with its target host membrane. For coronavirus, entry into a host cell is mediated by a single glycoprotein protruding from its membrane envelope, called spike (S). Within S, the region that directly interacts with the membrane is called the fusion peptide, FP. It is the physico-chemical interactions of the FP with the host membrane that anchors it, thus enabling the necessary deformations of the membrane that lead to delivery of the viral genome into the cell. Thus, understanding FP interactions at the most fundamental level will facilitate the development of strategies to limit those interactions to stop the spread of infections. This information is expected to be helpful in predicting the characteristics of emerging strains that could post a threat to humans in the future. The objective of this project is to measure and identify the specific intermolecular interactions responsible for insertion of FP into membranes. Specifically, this project will: 1) elucidate the factors that control hydrophobic interactions of FP using single molecule force measurements with atomic force microscopy and models of biological membranes, and 2) characterize the structure-function relationship of the FP using circular dichroism and isothermal calorimetry to correlate specific interactions with amino acid sequence and host surface properties. The intellectual merit of this project is discovering how changes in host membrane chemistry or amino acid sequence of the FP modulates the hydrophobic interaction and ultimately influences activity critical to the spread of infection. The broader impact of this project is providing information that will enable fresh approaches to the design of antiviral drugs, as well as to identify basic design rules that inform how the FP promotes the interaction with membranes of specific chemistry to predict host susceptibility to infection. Given that the FP is highly conserved across the CoV family, these studies will be directly applicable to all CoVs, including those yet to emerge.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.