The role of the protein tyrosine phosphatase PTP1B in mediating Toll-like receptors TLR7 and TLR9 function

Toll样受体(TLRs)体现了一个关键的细胞生物学概念：亚细胞定位决定生物过程的结果。已经广泛证明，TLR的功能需要被精确地调节，以防止识别自身配体时的不良反应，这可能导致自身免疫性或炎症性疾病。近年来，TLRs的贩运和本地化已经成为自我和非我之间的主要歧视机制，以及诱导不同的信号级联。目前，蛋白质酪氨酸磷酸酶PTP1B在TLR 7和9诱导的先天免疫反应中起到了新的作用。蛋白质组学方法鉴定PTP1B是一种新的相互作用伙伴。我们可以证明，在没有PTP1B的情况下，血浆细胞样树突状细胞对TLR7/9刺激和小鼠巨细胞病毒(MCMV)感染的I型干扰素反应在体外是受损的。相反，PTP1B缺陷细胞和小鼠在TLR7/9刺激下的促炎细胞因子反应是完整的。总体而言，我们的数据表明PTP1B作为依赖TLR7和TLR9的I型干扰素反应的关键正向调节因子具有潜在的作用。在拟议的项目中，我们将确定PTP1B在TLR7和TLR9在原代天然免疫细胞中的作用，目的如下：(1)利用细胞生物学和免疫学方法，我们将阐明PTP1B是否调控TLR7/9转运到特定的亚细胞间隔，或者在配体结合时调节TLR7/9诱导的I型干扰素下游信号通路。(2)我们将破译PTP1B的磷酸酶活性是否对其对TLR信号的正向调节作用至关重要，并旨在确定PTP1B的底物(S)或进一步的结合伙伴。(3)在体外，PTP1B对于MCMV感染的I型干扰素反应是重要的。我们将分析PTP1B在感染MCMV和体内革兰氏阳性细菌金黄色葡萄球菌的先天免疫反应中的作用。通过这些研究，我们有望从机制上深入了解核酸感应TLR的调节，并获得与TLR信号相关的专门间隔的知识。阐明调节TLR功能的分子途径最终将拓宽治疗自身免疫性疾病的机会。

Toll-like receptors (TLRs) exemplify a key cell biological concept: Subcellular localisation determines the outcome of biological processes. It has been widely demonstrated that TLR function needs to be precisely regulated to prevent adverse effects upon recognition of self ligands, which can lead to autoimmune or inflammatory disorders. In recent years, the trafficking and localisation of TLRs has emerged as a primary discriminatory mechanism between self versus non-self, as well as the induction of distinct signalling cascades. Currently, the precise regulation of endosomally located nucleic acid-sensing TLRs and their crucial cofactor UNC93B is still incompletely understood.We have accumulated several lines of evidence that the protein tyrosine phosphatase PTP1B is a novel player in the innate immune response elicited by endosomally located TLRs 7 and 9. PTP1B was identified in a proteomics approach as a novel interacting partner of UNC93B. We can show that the type I interferon response in plasmacytoid dendritic cells upon TLR7/9 stimulation and murine cytomegalovirus (MCMV) infection is impaired in the absence of PTP1B in vitro. In contrast, the proinflammatory cytokine response is intact in PTP1B deficient cells and mice upon TLR7/9 stimulation. Collectively, our data suggest a potential role for PTP1B as a critical positive regulator of the TLR7- and TLR9-dependent type I IFN response. In the proposed project we will define the role of PTP1B in TLR7 and TLR9 function in primary innate immune cells with the following aims: (1) Using cell biological and immunological methods we will elucidate whether PTP1B regulates either trafficking of TLR7/9 to specific subcellular compartments or the downstream type I IFN signalling pathway induced by TLR7/9 upon ligand binding.(2) We will decipher whether the phosphatase activity of PTP1B is crucial for its positive regulatory role on TLR signalling and aim to identify the substrate(s) or further binding partners of PTP1B.(3) In vitro, PTP1B is important for the type I IFN response to MCMV infection. We will analyse the role of PTP1B in the innate immune response to infection with MCMV and the Gram-positive bacterium Staphylococcus aureus in vivo.With these studies we expect to gain mechanistic insights into the regulation of nucleic acid-sensing TLRs and obtain knowledge about the specialised compartments associated with TLR signalling. Elucidating the molecular pathways that regulate TLR function will ultimately broaden therapeutic opportunities to treat autoimmune disease.