The cell biology of Toll-like receptor 9: a mechanism to prevent autoimmunity

描述(申请人提供)：Toll样受体(TLRs)的一个子集识别病毒和细菌基因组的核酸。这种识别策略可能要付出巨大的代价，因为这些类型的核酸也存在于宿主中。大多数情况下，对自身核酸的识别是可以避免的。然而，在某些情况下，TLRs有助于一种称为系统性红斑狼疮(SLE)的强有力的抗核酸免疫反应。这项建议的重点是确定防止识别自身核酸的机制，同时仍然允许检测外源核酸。我们正在使用TLR9作为核酸特异性TLR组的代表性例子来解决这一根本问题。TLR9识别双链DNA中未甲基化的CpG基序，并已被证明在许多双链DNA病毒的免疫反应中发挥作用。TLR9也参与了SLE的病理过程。TLR9生物学的一个有趣的方面是，它不会运输到细胞表面，而是定位并识别细胞内的配体。我们有证据表明，TLR9的细胞生物学受到多个水平的调控。本研究旨在明确TLR9在细胞内定位的调控机制。在目标1中，我们将定义TLR9内其细胞内保留所需的区域。在目标2中，我们将使用新的生化技术来表征控制TLR9定位和运输的途径。最后，在目标3中，我们在小鼠中表达突变受体，并测试细胞内定位对于避免自身DNA识别是必要的假设。总而言之，这些目标将解决TLR9的细胞生物学是如何调节的，并将测试这一调节在维持该受体正确的自我/非自我辨别方面的重要性。 公共卫生相关性：这项建议涉及免疫系统必须在识别感染和预防自身免疫之间保持平衡。这项研究的重点是TLR9，这是一种正常识别病毒DNA的蛋白质，但有时会不适当地识别自身DNA，从而导致自身免疫性疾病。这项研究的目标是了解TLR9如何在避免自身DNA的同时识别病毒DNA。

DESCRIPTION (provided by applicant): A subset of Toll-like receptors (TLRs) recognizes the nucleic acids of viral and bacterial genomes. This recognition strategy can come at a significant cost, as these types of nucleic acid are also present in the host. Most of the time, recognition of self nucleic acid is avoided. In some instances, though, TLRs contribute to a vigorous anti-nucleic acid immune response called systemic lupus erythematosus (SLE). This proposal focuses on defining the mechanisms that prevent recognition of self nucleic acid while still allowing detection of foreign nucleic acid. We are addressing this fundamental issue using TLR9 as a representative example of the group of nucleic acid-specific TLRs. TLR9 recognizes unmethylated CpG motifs in double-stranded DNA and has been shown to play a role in the immune response to a number of double-stranded DNA viruses. TLR9 has also been implicated in the pathology of SLE. An intriguing aspect of TLR9 biology is that it does not traffic to the cell surface, but instead localizes to and recognizes ligand within intracellular compartments. We have evidence that the cell biology of TLR9 is regulated at multiple levels. This research application aims to define the mechanisms that regulate TLR9 localization within the cell. In Aim 1 we will define the region within TLR9 necessary for its intracellular retention. In Aim 2, we will use novel biochemical techniques to characterize the pathways that control TLR9 localization and trafficking. Finally, in Aim 3 we express mutant receptors in mice and test the hypothesis that intracellular localization is necessary to avoid self DNA recognition. Collectively, these Aims will address how the cell biology of TLR9 is regulated and will test the importance of this regulation in maintaining proper self/non-self discrimination by this receptor. PUBLIC HEALTH RELEVANCE: This proposal deals with the balance that must be maintained by the immune system between recognition of infection and prevention of autoimmunity. The work focuses on TLR9, a protein that normally recognizes viral DNA, but can sometimes inappropriately recognize self DNA and cause autoimmune disease. The goal of this research is to understand how TLR9 recognizes viral DNA while avoiding self DNA.