Leukocyte Activation and Migration in Autoimmune Encephalomyelitis

 描述(由申请人提供)：我们研究计划的总体目标是了解多发性硬化症(MS)等自身免疫性疾病中白细胞激活和迁移的分子机制。大量的膜受体可以启动白细胞的活化和/或迁移，包括抗原受体、趋化因子受体和整合素。虽然这些受体与一系列不同的细胞外配体(第一信使)结合，但它们产生的一个常见的细胞内第二信使是PIP3(磷脂酰肌醇3，4，5-三磷酸)；PIP3反过来通过与数十种调节基因表达和/或细胞骨架重构的效应蛋白(如蛋白激酶AKT、BTK和PDK1)结合来指导白细胞的激活和迁移。这一应用的灵感来自于我们最近的发现，即常见的脂质第二信使PIP3的起源和功能由其TNFAIP8(肿瘤坏死因子-α诱导蛋白8)家族的“专业”转移蛋白控制。TNFAIP8家族具有一个特殊的疏水空腔，由PIP3等磷脂酰基链组成，是PIP3家族中唯一已知的转运蛋白家族。我们首次从实验性自身免疫性脑脊髓炎(EAE)小鼠的脊髓中克隆了TIPE2(TNFAIP8-like 2)基因，发现它优先在白细胞中表达。然后，我们培育了TIPE2缺陷小鼠，发现它们对EAE具有显著的抵抗力。出乎意料的是，TIPE2缺失的髓鞘特异性TH1和TH17细胞对髓鞘抗原高度敏感，但在向中枢神经系统迁移方面存在固有缺陷。因此，我们假设，TNFAIP8家族通过控制共同的脂质第二信使的产生和功能来赋予髓鞘特异性T细胞的脑原性，这些第二信使既介导激活又介导迁移。在没有它的情况下，由激活诱导的脂质第二信使的激增破坏了引导细胞迁移的内部PIP3“指南针”，导致产生高度活跃的非脑源性TH1和TH17细胞，而不能进行定向迁移。这一理论将在小鼠和人类系统(包括多发性硬化症)中使用遗传学、免疫学和生化方法进行测试。具体地说，我们将确定(I)TIPE2和TNFAIP8调节髓鞘特异性T细胞激活的机制，以及(Ii)TIPE2和TNFAIP8调节自身免疫性脑脊髓炎期间白细胞迁移的机制。

 DESCRIPTION (provided by applicant): The overall objective of our research program is to understand the molecular mechanisms of leukocyte activation and migration during autoimmune diseases such as multiple sclerosis (MS). A large number of membrane receptors can initiate leukocyte activation and/or migration, which include antigen receptors, chemokine receptors, and integrins. While these receptors bind to a diverse array of extracellular ligands (first messengers), a common intracellular second messenger generated by them is PIP3 (phosphatidylinositol 3,4,5-trisphosphate); PIP3 in turn directs leukocyte activation and migration by binding to dozens of effector proteins (such as protein kinases AKT, BTK, and PDK1) that regulate gene expression and/or cytoskeleton remodeling. This application is inspired by our recent discovery that the genesis and function of the common lipid second messenger PIP3 are controlled by its "professional" transfer proteins of the TNFAIP8 (tumor necrosis factor-α-induced protein 8) family. The TNFAIP8 family possesses a specific hydrophobic cavity that is constitutively occupied by the acyl chains of phosphoinositides such as PIP3, and it is the only known transfer protein family of PIP3. We initially cloned the TIPE2 (TNFAIP8-like 2) gene from spinal cord of mice with experimental autoimmune encephalomyelitis (EAE) and found that it was preferentially expressed by leukocytes. We then generated TIPE2-deficient mice and found that they were significantly resistant to EAE. Unexpectedly, TIPE2-deficient myelin-specific TH1 and TH17 cells were hyper-sensitive to myelin antigens but had an intrinsic defect in migration into CNS. We therefore hypothesize that TNFAIP8 family confers the encephalitogenicity of myelin-specific T cells by controlling the genesis and function of common lipid second messengers that mediate both activation and migration. In its absence, the activation-induced surge of lipid second messengers destroys the internal PIP3 "compass" that guides cell migration, leading to the generation of hyper-active non-encephalitogenic TH1 and TH17 cells not capable of directional migration. This theory will be tested in both murine and human systems (including MS) using genetic, immunological, and biochemical approaches. Specifically, we will determine (I) the mechanism through which TIPE2 and TNFAIP8 regulate myelin-specific T cell activation, and (II) the mechanism through which TIPE2 and TNFAIP8 regulate leukocyte migration during autoimmune encephalomyelitis.