Fractalkine: Roles in Cell Adhesion and Atherosclerosis

描述(由申请人提供)：趋化因子在血管疾病中单核细胞和巨噬细胞的运输中起着关键作用，但其作用的分子机制尚不清楚。Fractalkine是一种具有独特结构的新型趋化因子。与可溶性趋化因子不同，Fractalkine由一个类似趋化因子的结构域与膜结合的粘蛋白茎融合而成。一种可溶性的Fractalkine是在TACE的作用下产生的，TACE是一种金属蛋白酶，可以在跨膜结构域上方裂解Fractalkine。在其可溶形式中，Fractalkine是一种强大的趋化剂，但在其膜结合形式中，它捕获了携带其同源受体CX3CR1的细胞。我们已经证明，通过基因打靶而缺失CX3CR1的小鼠可以防止异位心脏移植的排斥反应和饮食诱导的动脉粥样硬化。然而，膜结合形式和可溶性形式的Fractalkine在这些血管疾病中的相对作用尚不清楚。为了研究膜结合FK的作用，我们将创造表达一种不可切割形式的Fractalkine的敲入小鼠。为了研究可溶性Fractalkine的作用，我们将创造表达可溶性FK但不表达膜结合FK的小鼠。这些研究将检验FK裂解有助于动脉粥样硬化形成的假设。最近对患者的遗传学研究表明，CX3CR1的多态与预防冠状动脉疾病相关。我们将把这种V259I/T280M突变引入小鼠CX3CR1，并测试这种多态通过防止捕获单核/巨噬细胞来保护动脉粥样硬化的假设。Fractalkine并不是唯一被发现在动脉粥样硬化中发挥作用的趋化因子。我们之前已经证明，MCP-1及其受体CCR2有助于巨噬细胞的募集和病变的形成。在这项提案的最后部分，我们将创建同时缺乏Fractalkine和CCR2的双基因敲除小鼠，以确定这些趋化因子是独立发挥作用还是协同作用促进动脉粥样硬化形成。完成这些目标将极大地促进我们对Fractalkine促进动脉粥样硬化病变形成的机制的理解。

DESCRIPTION (provided by applicant): Chemokines play a critical role in the trafficking of monocytes and macrophages in vascular disease, but the molecular mechanisms of their actions are poorly understood. Fractalkine is a novel chemokine with an unusual architecture. Unlike soluble chemokines, fractalkine consists of a chemokine-like domain fused to a membrane-bound mucin stalk. A soluble form of fractalkine is created by the action of TACE, a metalloprotease that cleaves fractalkine just above the transmembrane domain. In its soluble form fractalkine is a potent chemoattractant, but in its membrane-bound form it captures cells bearing its cognate receptor, CX3CR1. We have shown that mice in which CX3CR1 is deleted by gene targeting are protected against rejection of heterotopic cardiac transplants, and diet-induced atherosclerosis. However, the relative contributions of the membrane-bound and soluble forms of fractalkine to these vascular disease are unknown. To investigate the role of membrane-bound FK we will create knock-in mice expressing a noncleavable form of fractalkine. To investigate the role of soluble fractalkine, we will create mice that express soluble, but not membrane-bound FK. These studies will test the hypothesis that the cleavage of FK contributes to atherogenesis. Recent genetic studies in patients have revealed that a polymorphism in CX3CR1 correlates with protection from coronary artery disease. We will introduce this V259I/T280M mutation into murine CX3CR1, and test the hypothesis that the polymorphism affords protection from atherosclerosis by preventing the capture of monocyte/macrophages. Fractalkine is not the only chemokine that has been found to play a role in atherosclerosis. We have previously shown that MCP-1, and its receptor CCR2, contribute to macrophage recruitment and lesion formation. In the final portion of this proposal, we will create double knockout mice lacking both fractalkine and CCR2 to determine if these chemokines act independently or in concert to promote atherogenesis. Completion of these aims will significantly advance our understanding of the mechanisms by which fractalkine contributes to lesion formation in atherosclerosis.