Dissecting how inflammation-induced tenascin-C regulates the master mediator of inflammation miR-155

在感染过程中，固有免疫细胞如巨噬细胞检测到保守的微生物成分，这些细胞具有模式识别受体，包括toll样受体（TLRs）。一旦被激活，tlr启动炎症反应，最终产生炎症介质，如细胞因子，随后引发特异性适应性免疫反应。这一过程的失调会导致炎症和自身免疫性疾病，如败血症、类风湿性关节炎和系统性红斑狼疮。因此，TLR信号必须严格调控。MicroRNAs是一种小的非编码rna，是控制TLR信号传导和细胞因子合成的重要基因表达调节剂。在巨噬细胞中，TLR激活感染后会诱导几种microrna，这些microrna通过靶向编码TLR信号系统成分和下游细胞因子的mrna的3'非翻译区（UTR）发挥作用。我们发现细胞外基质糖蛋白tenascin-C （TN-C）调节被细菌成分脂多糖（LPS）激活的巨噬细胞中促炎细胞因子TNF-a的产生。TN-C通过调节microRNA miR-155的表达来实现这一点。然而，TN-C究竟如何调控miR-155的生物发生尚不清楚。该项目的总体假设建立在我们的初步数据之上，该数据表明TN-C在转录后水平调控miR-155的生物发生。具体来说，在TN-C存在的情况下，Drosha在细胞核中对miR-155初级转录物的酶切效率显著提高。目标是：1。确定TN-C在细胞核中调控miR-155加工的分子机制。2. 确定确定的调控机制是miR-155特异性的还是适用于其他mirna。该项目将受益于Piccinini小组（分子免疫学、microRNA和细胞生物学）和Jopling小组（microRNA调控）的专业知识。

During infection conserved microbial components are detected by innate immune cells such as macrophages which possess pattern recognition receptors, including Toll-like receptors (TLRs). Once activated, TLRs initiate inflammatory responses that culminate with the production of inflammatory mediators such as cytokines that subsequently prime specific adaptive immune responses. Dysregulation of this process can lead to inflammatory and autoimmune diseases such as sepsis, rheumatoid arthritis and systemic lupus erythematosus. Therefore TLR signalling must be tightly regulated. MicroRNAs, small noncoding RNAs, are important regulators of gene expression that control TLR signalling and cytokine synthesis. Several microRNAs are induced upon infection by TLR activation in macrophages and these microRNAs function by targeting the 3' untranslated region (UTR) of mRNAs encoding components of the TLR signalling system and the downstream cytokines. We found that the extracellular matrix glycoprotein tenascin-C (TN-C) regulates the production of the pro-inflammatory cytokine TNF-a in macrophages activated by the bacterial component lipopolysaccharide (LPS). TN-C does this by regulating the expression of the microRNA miR-155. However, how TN-C exactly regulates miR-155 biogenesis is unknown. The overall hypothesis of the project builds on our preliminary data which suggests that TN-C regulates miR-155 biogenesis at the post-transcriptional level. Specifically, in the presence of TN-C enzymatic cleavage of the miR-155 primary transcript by Drosha in the nucleus is significantly more efficient. The aims are: 1. Determine the molecular mechanism by which TN-C regulates miR-155 processing in the nucleus. 2. Establish whether the identified regulatory mechanism is specific to miR-155 or applies to other miRNAs. The project will benefit from the expertise of the Piccinini group (molecular immunology, microRNAs and cell biology) and Jopling group (microRNA regulation).