Molecular Aspects of Human CD1d Functions

描述(由申请人提供)：CD1d跨膜糖蛋白向自然杀伤T细胞(Natural Killer T，NKT)提供脂类并激活它们，以产生对启动免疫T细胞反应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CD1d糖蛋白在ER及其小亚基22M和ER衍生脂质中组装的机制。我们还希望确定通过内吞途径在分泌和循环过程中负责交换相关脂类的机制。我们还将研究单纯疱疹病毒-1(HSV-1)使感染它的细胞逃避NKT细胞识别的机制。这涉及到人类CD1d分子从细胞表面到溶酶体限制膜的特定重新分布。CD1d分子与MHC II类分子结合，受II类转录激活剂CIITA的表达调控。在共表达CIITA的转基因细胞系中未观察到HSV-1感染时CD1d的重新分布，但在HSV-1感染的II类阳性树突状细胞中可见CD1d重新分布，这表明在感染后树突状细胞中CD1d-MHC II类连接是解偶联的。我们建议确定这种现象背后的机制。树突状细胞、巨噬细胞和其他类型的细胞通过各种病原体成分与先天免疫受体如Toll样受体(TLRs)的相互作用而被激活。这种激活的一个结果是，激活的细胞有力地刺激NKT细胞，部分原因是CD1d相关脂类的轮廓发生了变化。巨噬细胞在TLR4介导的激活后对其溶酶体靶向机制进行重新编程，从而导致溶酶体蛋白前体的分泌。这些蛋白质包括溶酶体酶和被称为皂苷的脂转移蛋白的前体--丙皂苷。其中，皂苷B通过内吞途径中的CD1d分子介导脂质交换。我们将确定这种重新编程在增强TLR介导的激活时所看到的NKT刺激中的作用。我们还建议建立一个小鼠品系，其中小鼠的CD1d基因座被人的CD1d基因座取代，以使我们能够在体内评估CD1d下调调控在感染过程中的作用。与公共卫生相关：CD1d分子通过激活NKT细胞，在启动适当的T细胞对许多病毒的反应中发挥至关重要的作用。了解它们如何调节这一功能至关重要。单纯疱疹病毒是一个主要的公共卫生问题，其避免NKT识别的能力可能是其在首次感染后持续存在的关键。

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. PUBLIC HEALTH RELEVANCE: CD1d molecules play a vital role in initiating the appropriate T cell responses to many viruses by activating NKT cells. Understanding how they mediate this function is of vital importance. Herpes simplex virus is a major public health problem and its ability to avoid NKT recognition is likely to be key for its persistence after the initial infection.