Molecular Aspects of Human CD1d Functions

描述（由申请方提供）：CD 1d跨膜糖蛋白将脂质呈递给自然杀伤T（NKT）细胞，并激活它们产生对免疫T细胞应答启动至关重要的细胞因子。脂质结合的机制还不完全清楚，但脂质结合可以发生在内质网（ER），分泌途径和内吞途径。我们试图了解调节人CD 1d糖蛋白在ER中与其小亚基22 m和ER衍生脂质组装的机制。我们还希望确定的机制，负责交换相关的脂质在分泌过程中，并在回收过程中通过内吞途径。我们还将研究单纯疱疹病毒-1（HSV-1）允许被其感染的细胞逃避NKT细胞识别的机制。这涉及人CD 1d分子从细胞表面到溶酶体界膜的特异性再分布。CD 1d分子与MHC II类分子结合，后者受II类转录激活因子CIITA的表达调控。在共表达CIITA的转染细胞系中未观察到HSV-1感染后的CD 1d再分布，但在HSV-1感染的II类阳性树突状细胞中观察到，表明在树突状细胞中，CD 1d-MHC II类连接在感染后解偶联。我们建议确定这种现象背后的机制。树突状细胞、巨噬细胞和其他细胞类型通过多种病原体组分与先天免疫受体如Toll样受体（TLR）的相互作用而被激活。这种激活的一个结果是，激活的细胞强烈刺激NKT细胞，部分原因是CD 1d相关脂质谱的变化。巨噬细胞在TLR 4介导的激活后经历其溶酶体靶向机制的重编程，导致溶酶体蛋白质前体的分泌。这些蛋白质包括溶酶体酶和鞘脂激活蛋白原，鞘脂激活蛋白是称为鞘脂激活蛋白的脂质转移蛋白的前体。其中之一，saposin B，介导内吞途径中CD 1d分子的脂质交换。我们将确定这种重编程在TLR介导的激活后NKT刺激增强中的作用。我们还建议产生一种小鼠品系，其中小鼠CD 1d基因座被人类基因座取代，以使我们能够评估CD 1d下调在感染过程中的体内作用。

DESCRIPTION (provided by applicant): CD1d transmembrane glycoproteins present lipids to Natural Killer T (NKT) cells and activate them to produce cytokines critical for initiation of immune T cell responses. The mechanisms responsible for lipid association are incompletely understood, but lipid binding can occur in the endoplasmic reticulum (ER), the secretory pathway and the endocytic pathway. We seek to understand the mechanisms that regulate assembly of the human CD1d glycoprotein in the ER with its small subunit 22m and with ER-derived lipids. We also wish to determine the mechanisms responsible for exchanging associated lipids during secretion and during recycling through the endocytic pathway. We also will investigate the mechanism used by herpes simplex virus-1 (HSV-1) that allows cells infected by it to evade recognition by NKT cells. This involves the specific redistribution of human CD1d molecules from the cell surface to the limiting membrane of the lysosome. CD1d molecules associate with MHC class II molecules, which are regulated by expression of the class II transcriptional activator CIITA. CD1d redistribution upon HSV-1 infection is not observed in transfected cell lines that co-express CIITA, but is seen in HSV-1-infected class II-positive dendritic cells, suggesting that in dendritic cells the CD1d-MHC class II linkage is uncoupled upon infection. We propose to determine the mechanism underlying this phenomenon. Dendritic cells, macrophages, and other cell types are activated by the interaction of a variety of pathogen components with innate immune receptors such as Toll-like Receptors (TLRs). One outcome of such activation is that the activated cells robustly stimulate NKT cells, in part because of a change in the profile of CD1d-associated lipids. Macrophages undergo a reprogramming of their lysosomal targeting mechanisms upon TLR4-mediated activation that results in the secretion of precursors of lysosomal proteins. These proteins include lysosomal enzymes and prosaposin, the precursor of the lipid transfer proteins called saposins. One of these, saposin B, mediates lipid exchange by CD1d molecules in the endocytic pathway. We will determine the role of this reprogramming in the enhancement of NKT stimulation seen upon TLR-mediated activation. We also propose to generate a mouse strain in which the mouse CD1d locus is replaced by the human one, to allow us to evaluate the in vivo role of CD1d down regulation in the infectious process.