Transcriptional regulation of Toll-like receptor signaling

描述（由申请人提供）：toll样受体（TLRs）是微生物产物的关键传感器，对病原体先天免疫的发展至关重要。TLR激活诱导数百个基因的表达，这些基因编码炎症细胞因子、抗菌蛋白、再生和代谢调节因子；这些分子反过来介导炎症、抗微生物免疫和传染病患者的组织再生。然而，tlr不受控制或长时间的激活可能会产生毁灭性的后果，包括感染性休克和致命的炎症性疾病的发展。幸运的是，TLR的激活受到两类负调节因子的严格控制：a)抑制TLR信号传导的信号特异性调节因子，b)抑制TLR靶基因转录的基因特异性调节因子。这些调节因子确保tlr长时间或反复暴露于其配体不会导致受体的持续激活；相反，它使它们对随后的配体刺激不敏感或反应迟钝。这种现象被称为TLR耐受，或脂多糖（LPS）耐受，当脂多糖是配体参与。最近对LPS反应的基因组分析表明，LPS耐受是一种基因特异性现象，即它选择性地靶向一组基因（如炎症基因），而不是其他基因（如抗菌基因）；事实上，抗微生物基因的表达在LPS耐受的细胞中进一步上调。因为引起有害炎症反应的是炎症基因，而不是抗菌基因，所以LPS耐受性确保宿主能够持续建立其抗菌免疫，而不会引起致命的炎症性疾病，即使是慢性或长期感染。然而，通过长时间的LPS暴露激活抗菌基因，但矛盾地抑制炎症基因的分子机制尚不清楚。我们最近发现B细胞白血病(Bcl)-3通过抑制核因子(NF)- 3介导LPS耐受。B， LPS激活的三大转录因子之一。本研究的目的是阐明Bcl-3调控TLR激活和耐受性的分子机制。具体来说，我们将定义1)NF-？2) p50泛素化在TLR信号传导中的作用；3)Bcl-3抑制p50泛素化的机制。从这些研究中产生的信息不仅可能带来关于TLR信号传导机制的重要概念进展，而且还有助于开发新的基于bcl -3的传染病治疗策略。

DESCRIPTION (provided by applicant): Toll-like receptors (TLRs) are key sensors of microbial products and are essential for the development of innate immunity to pathogens. TLR activation induces the expression of hundreds of genes that encode inflammatory cytokines, antimicrobial proteins, and regeneration and metabolic regulators; these molecules in turn mediate inflammation, antimicrobial immunity and tissue regeneration seen in patients with infectious diseases. However, uncontrolled or prolonged activation of TLRs can have devastating consequences, which include the development of septic shock and fatal inflammatory diseases. Fortunately, TLR activation is tightly controlled by two classes of negative regulators: a) signal-specific regulators that inhibit TLR signaling, and b) gene-specific regulators that suppress TLR target gene transcription. These regulators ensure that prolonged or repeated exposure of TLRs to their ligands does not lead to sustained activation of the receptors; instead, it renders them insensitive or hyporesponsive to subsequent ligand stimulation. This phenomenon is referred to as TLR tolerance, or lipopolysaccharide (LPS) tolerance when LPS is the ligand involved. Recent genomic profiling of LPS responses reveals that LPS tolerance is a gene-specific phenomenon, i.e., it selectively targets one set of genes (e.g., inflammatory genes) but not others (e.g., antimicrobial genes); in fact, the expression of antimicrobial genes is further upregulated in LPS tolerized cells. Because it is the inflammatory genes, not the antimicrobial genes, that cause deleterious inflammatory responses, LPS tolerance ensures that the host is able to continuously build up its antimicrobial immunity without causing fatal inflammatory diseases even with chronic or prolonged infections. However, the molecular mechanisms through which prolonged LPS exposure activates antimicrobial genes, but paradoxically suppresses inflammatory genes are unknown. We recently discovered that B cell leukemia (Bcl)-3 mediates LPS tolerance by inhibiting nuclear factor (NF)-??B, one of the three major transcription factors activated by LPS. The goal of this investigation is to elucidate the molecular mechanisms through which Bcl-3 regulates TLR activation and tolerance. Specifically, we will define 1) the roles of NF-?B binding sites of gene promoters in TLR tolerance, 2) the roles of p50 ubiquitination in TLR signaling, and 3) the mechanisms through which Bcl-3 inhibits p50 ubiquitination. Information generated from these studies may not only bring about an important conceptual advance with regard to mechanisms of TLR signaling but also aid in the development of novel Bcl-3-based strategies for the treatment of infectious diseases. PUBLIC HEALTH RELEVANCE The proposed experiments will examine a key gene-specific regulatory mechanism essential for Toll-like receptor (TLR) signaling using combined genetic, bioinformatic and immunologic tools. This inter-disciplinary approach, will likely lead to a conceptual breakthrough with regard to the mechanism of TLR tolerance, a phenomenon widely recognized but poorly understood. Additionally, the proposed studies will also help develop novel Bcl-3-based strategies for the treatment of infectious diseases.