Glycosaminoglycan-papillomavirus interactions: From structure to function and inhibition

人乳头瘤病毒(HPV)是一大类无包膜DNA肿瘤病毒。其中，HPV16是包括宫颈癌在内的各种肛门生殖系统肿瘤的主要原因。在进入宿主细胞时，HPV16首先与硫酸乙酰肝素蛋白多糖(HSPGs)结合。最近，我们的研究表明，HPV16衣壳与HSPG的糖胺多聚糖(GAG)链的初始相互作用足以引起构象变化。这促进了病毒颗粒的进一步结构变化，导致受体切换和准备颗粒去涂层，即病毒基因组从衣壳结构中释放(Cerqueira等人，2013年；Cerqueira等人，2015年)。病毒的这种结构性激活似乎严重依赖于高硫酸盐化含量、硫酸盐化模式、特定的碳水化合物骨架和Gag链的长度。这一观察提出了一种有趣的可能性，即不同类型的HPV对粘膜和皮肤上皮的趋向性取决于组织依赖的GAG的硫酸盐化模式。在这个项目中，我们旨在阐明GAG-HPV相互作用的结构先决条件和后果。为此，我们将使用一套建立的基于细胞的分析方法，结合Forschergruppe中的结构生物学方法来定义Gag和HPV衣壳的结构约束，以结合、结构激活和抑制潜力。一方面，我们将探索进化上不同的HPV类型和HS多糖的多样性，以阐明这种相互作用的共同主题和具体差异。另一方面，我们将定义导致HPV16结构激活的理想Gag结构，以及构象变化的分子细节。这项研究中使用的方法体系利用了Forschergruppe的跨学科方法，包括但不限于基于细胞的分析、质谱分析、核磁共振研究以及精密拟糖聚合物的使用。总体而言，我们希望确定HS-HPV衣壳相互作用的结构和功能后果，这将使我们能够提出HS依赖进入的全面模型，进而可用于开发预防性抗HPV化合物。

Human papillomaviruses (HPV) are a large family of non-enveloped DNA tumor viruses. Of those, HPV16 is the leading cause for a variety of anogenital tumors including cervical cancer. For entry into host cells, HPV16 initially binds to heparan sulfate proteoglycans (HSPGs). Recently, our research demonstrated that the initial interaction of HPV16 capsids with the glycosaminoglycan (GAG) chains of HSPGs is sufficient to induce a conformational change. This facilitates further structural alterations in the virus particle resulting in receptor switching and preparing the particle for uncoating, i.e. the release of the viral genome from the capsid structure (Cerqueira et al., 2013; Cerqueira et al., 2015). This structural activation of the virus appears to be critically dependent on a high sulfation content, on the sulfation pattern, on a certain carbohydrate backbone, and on the lengths of the GAG chain. This observation raises the interesting possibility that the tropism of different HPV types for mucosal vs. skin epithelia depends on a tissue-dependent sulfation patterning of GAGs.In this project, we aim to elucidate the structural prerequisites and consequences of GAG-HPV interactions. For this, we will use an established repertoire of cell-based assays in combination with structural biology approaches within the Forschergruppe to define the structural constraints of the GAG and HPV capsids for binding, structural activation, and inhibitory potential. On the one hand, we will probe the variety of evolutionary diverse HPV types and HS glycans to elucidate common themes and specific differences for this interaction. On the other hand, we will define the ideal GAG structure to cause structural activation of HPV16, as well as the molecular details of the conformational change. The repertoire of methods used in this study capitalizes on the interdisciplinary approach of the Forschergruppe and includes but is not limited to cell-based assays, mass spectrometry, nuclear magnetic resonance studies, and the use of precision glycomimetic polymers. Overall, we expect to identify structural and functional consequences of HS-HPV capsid interactions that will allow us to propose a comprehensive model of HS-dependent entry, which, in turn, could be used to develop preventative anti-HPV compounds.