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 （NKT）细胞提供脂质，并激活它们产生对启动免疫T细胞反应至关重要的细胞因子。脂质结合的机制尚不完全清楚，但脂质结合可发生在内质网（ER）、分泌途径和内吞途径。我们试图了解调节人CD1d糖蛋白在内质网及其小亚基22m和内质网衍生脂质的组装的机制。我们还希望确定在分泌和通过内吞途径循环过程中负责交换相关脂质的机制。我们还将研究单纯疱疹病毒-1 （HSV-1）使用的机制，该机制允许被其感染的细胞逃避NKT细胞的识别。这涉及到人类CD1d分子从细胞表面到溶酶体的极限膜的特异性再分配。CD1d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的转染细胞系中没有观察到CD1d在HSV-1感染后的再分布，但在HSV-1感染的II类阳性树突状细胞中可以观察到，这表明在树突状细胞中，CD1d- mhc II类连锁在感染后解耦。我们建议确定这一现象背后的机制。树突状细胞、巨噬细胞和其他类型的细胞被多种病原体成分与先天免疫受体（如toll样受体（TLRs））的相互作用激活。这种激活的一个结果是，被激活的细胞强烈刺激NKT细胞，部分原因是cd1相关脂质谱的变化。巨噬细胞在tlr4介导的激活下，对其溶酶体靶向机制进行重编程，导致溶酶体蛋白前体的分泌。这些蛋白质包括溶酶体酶和皂苷，是脂质转移蛋白皂苷的前体。其中之一皂苷B在内吞途径中通过CD1d分子介导脂质交换。我们将确定这种重编程在tlr介导的激活中增强NKT刺激的作用。我们还建议产生一种小鼠品系，其中小鼠CD1d位点被人类CD1d位点取代，以便我们能够评估CD1d下调在感染过程中的体内作用。公共卫生相关性：CD1d分子通过激活NKT细胞，在启动对许多病毒的适当T细胞反应中起着至关重要的作用。了解它们如何调节这一功能是至关重要的。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初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.