Role of Kaposi’s sarcoma-associated herpesvirus complement control protein in cell migration and angiogenesis

根据世界卫生组织的数据，目前有七种人类致癌病毒导致了全球20%以上的肿瘤。其中，卡波西肉瘤相关疱疹病毒(KSHV)可导致三种恶性肿瘤：卡波西肉瘤(KS)、原发渗出性淋巴瘤和多中心性Castleman病。KS是撒哈拉以南非洲最常见的肿瘤，见于获得性免疫缺陷综合征患者，对移植接受者来说是一个风险。与KSHV相关的恶性肿瘤，尤其是KS，其特征是存在促炎浸润物和血管生成。尽管这种病毒与肿瘤发生有关，但目前还没有针对KSHV的特效治疗方法。此外，导致疾病的分子机制和特定病毒蛋白在疾病进展中的作用还没有得到很好的表征。KSHV补体控制蛋白(KCP)是人类补体激活调节剂的同系物，主要抑制经典的补体途径。我们通过不同的途径发现KCP与纤维连接蛋白-亮氨酸重复序列跨膜蛋白(FlRT)和趋化因子结合，提示KCP在KHSV感染过程中参与补体抑制以外的功能。Flrt1-3是I型跨膜蛋白，参与细胞黏附、细胞迁移和血管生成。趋化因子是一类趋化细胞因子，在白细胞迁移、血管生成、肿瘤发展和转移中发挥重要作用。尽管趋化因子和Flt之间存在差异，但一个共同点是它们影响细胞迁移和血管生成。有趣的是，KCP与趋化因子的结合促进了趋化因子介导的细胞迁移，这表明KCP可能有助于白细胞的渗透，并可能调节趋化因子的血管生成特性。我们的主要目的是解决这样的假设，即KCP、趋化因子和Flt之间的相互作用影响细胞迁移和血管生成，这是KS的两个特征，在发病机制中发挥作用。为了实现这一目标，我们将结合分子生物学、生物化学、基于细胞的功能分析、感染实验和结构分析。我们将利用KCP络合物晶体的X射线衍射分析，在分子水平上表征KCP、趋化因子和FLRT之间的相互作用。我们还将确定KSHV感染背景下相互作用的功能相关性。总体而言，该项目将阐明KCP在KSHV发病机制中的作用，为干预提供新的潜在靶点。此外，在细胞迁移和血管生成领域获得的知识将有助于我们理解病毒介导的肿瘤发生。

According to the WHO, there are currently seven human oncogenic viruses that are responsible for more than 20% of all tumours worldwide. One of these viruses, Kaposi’s sarcoma-associated herpesvirus (KSHV) causes three malignancies: Kaposi’s sarcoma (KS), primary effusion lymphoma and multicentric Castleman’s disease. KS is the most common tumour in sub-Saharan Africa, in patients with acquired immunodeficiency syndrome and a risk for transplant recipients. KSHV-associated malignancies, KS in particular, are characterized by the presence of a pro-inflammatory infiltrate and angiogenesis. Despite the relevance of this virus in oncogenesis, there are no specific treatments for KSHV. Moreover, the molecular mechanisms that lead to disease and the role of specific viral proteins in disease progression are not well characterized. KSHV complement control protein (KCP) is a homolog of human regulators of complement activation that inhibits predominantly the classical complement pathway. We have discovered, through different approaches, that KCP binds to fibronectin leucine-rich repeat transmembrane proteins (FLRT) and chemokines, suggesting that KCP is involved in functions other than complement inhibition during KHSV infection. FLRT1-3 are type I transmembrane proteins involved in cell adhesion, cell migration, and angiogenesis. Chemokines are chemoattractant cytokines that play fundamental roles in leukocyte migration, angiogenesis, tumour development and metastasis. Despite the differences between chemokines and FLRTs, one commonality is that they influence cell migration and angiogenesis. Interestingly, KCP binding to chemokines enhanced chemokine-mediated cell migration, suggesting that KCP could contribute to leukocyte infiltration and potentially modulate the angiogenic properties of chemokines. Our main objective is to address the hypothesis that an interaction between KCP, chemokines and FLRTs influences cell migration and angiogenesis, two hallmarks of KS, playing a role in pathogenesis. To achieve this objective we will combine molecular biology, biochemistry, cell-based functional assays, infection experiments and structural analysis. We will characterize the interactions between KCP, chemokines and FLRTs at the molecular level, using X-ray diffraction analysis of KCP complex crystals. We will also determine the functional relevance of the interactions in the context of KSHV infection. Overall, this project will shed light on the role of KCP in the pathogenesis of KSHV, providing novel potential targets for intervention. Moreover, the obtained knowledge in the fields of cell migration and angiogenesis will contribute to our understanding of virus-mediated oncogenesis.