Rhadinovirus Receptors - Structure, Signaling, and Cell Tropism

细胞受体是病原体趋向性的主要决定因素，并提供与宿主细胞的第一个特异性相互作用。人类卡波西肉瘤相关疱疹病毒（KSHV）和恒河猴横纹肌病毒（RRV） （KSHV的动物模型）都通过病毒gH/gL糖蛋白复合物结合受体酪氨酸激酶Eph家族的成员。A型受体EphA2不仅对KSHV感染至关重要，而且对丙型肝炎病毒（HCV）、沙眼衣原体和疟疾寄生虫（病毒、细菌和真核起源的病原体）的感染也至关重要。这种趋同进化表明，与EphA2的相互作用对各种各样的病原体极为有利，这就提出了一个问题：是什么让EphA2如此有吸引力？鉴于这四种病原体的累积疾病负担，需要进一步分析。关于特异性受体在KSHV和RRV的细胞和组织趋向性中的作用，我们的初步数据表明，除了Ephs外，RRV的gH/gL还存在其他受体，很可能也存在KSHV。特别是对于RRV，我们有强有力的证据表明Ephs和两个候选替代受体的细胞类型特异性使用。因此，提出的研究重点是gH/gL受体相互作用的几个关键方面：a)病毒-受体相互作用的结构方面，特别是gH/gL受体相互作用的晶体结构，以及个体相互作用在病毒进入和细胞趋向性中的作用。b)新型受体和作用于受体下游的宿主因子。对受体相互作用的结构基础和下游信号级联的新见解将允许设计新的干预策略，不仅针对KSHV。我们已经利用我们对特定病毒受体相互作用的初步但仍然有限的见解来产生缺乏与单个受体相互作用能力的突变病毒。我们将使用新的结构数据来改进这些突变体，我们将能够直接将新的结构信息与生物功能联系起来。我们的研究将为今后将这些突变病毒应用于限制细胞和组织趋向性的疫苗和疫苗载体奠定基础，是研制KSHV预防性疫苗的重要一步。

Cellular receptors are major determinants of pathogen tropism and provide the first specific interaction with the host cell. Both the human Kaposi's sarcoma-associated herpesvirus (KSHV) and the rhesus monkey rhadinovirus (RRV), an animal model for KSHV, bind members of the Eph family of receptor tyrosine kinases through the viral gH/gL glycoprotein complex. The A type receptor EphA2 is not only critical for infection with KSHV but also for infection with hepatitis C virus (HCV), Chlamydia trachomatis, and malaria parasites - pathogens of viral, bacterial, and eukaryotic origin. This convergent evolution suggests that interaction with EphA2 is extremely advantageous for a very diverse range of pathogens, which raises the question: What makes EphA2 so attractive? Given the cumulative disease burden of these four pathogens, further analysis is needed.With regard to the role of specific receptors for the cell and tissue tropism of the rhadinoviruses KSHV and RRV, our preliminary data indicate the existence of additional receptors other than Ephs for gH/gL of RRV, and very likely also for KSHV. For RRV in particular, we have strong evidence for cell type-specific use of Ephs and two candidate alternative receptors. The proposed research therefore focuses on several key aspects of the gH/gL receptor interaction:a) Structural aspects of virus-receptor interactions, in particular crystal structures of the gH/gL-receptor interaction, and the role of individual interactions for viral entry and cell tropism.b) Novel receptors and host factors acting downstream of receptors. New insights into the structural basis of receptor interactions and into downstream signaling cascades will allow devising novel intervention strategies, not only for KSHV. We are already using our preliminary but still limited insights about specific virus-receptor interactions to generate mutant viruses that lack the ability to interact with individual receptors. We will use novel structural data to refine these mutants, and we will be able to directly correlate novel structural information with biological function. Our research will lay the groundwork for future application of these mutant viruses as vaccines and vaccine vectors whose cell and tissue tropism is restricted, an important step towards a prophylactic KSHV vaccine.