Abstract
MicroRNA-155 (miR-155) has been as an important controller of TLR3 signalling. However, the interactions between miR-155 and TLR3 are poorly understood. Here, we focused on the regulation of the relationship between miR-155 and TLR3. Sequence analyses and firefly luciferase reporter assay revealed that miR-155 target were present in the coding sequences (CDS) of TLR3. And the expression of the TLR3 protein could be inhibited by a miR-155 mimic or by a virally encoded orthologue in chick embryo fibroblast cells. Notably, endogenous miR-155 induction emerged a negative regulation on TLR3 expression in TLR2, 4 and 7 ligands stimulated HD11 cells, an avian macrophage cell line. Moreover, treatment with the miR-155 antagomir increased TLR3 levels while significantly decreased the abundance of TLR3 with miR-155 agomir. In addition, our data showed that miR-155 could inhibit IFN-β production possibly though TLR3 signal pathway. All these findings might reveal a new mechanism by which miR-155 can regulate the TLR3 immune response.
Highlights
Toll-like receptor (TLR) has key roles in the recognition of pathogens and the initiation of the innate immune response that subsequently primes the specific adaptive immune response during infection [1, 2]
The target sites of the miR-155 sequence in the coding region of the Homo sapiens, Gallus gallus, Danio rerio, Equus caballus, Taeniopygia guttata and Cyprinus carpio TLR3 mRNAs were analysed by computational analyses and blast analyses of the miR-155 target sites
We identified the existence of many naturally occurring miR-155 targets in the amino acid coding sequence of TLR3 and the essential role of miR-155 in the control of TLR3 expression
Summary
Toll-like receptor (TLR) has key roles in the recognition of pathogens and the initiation of the innate immune response that subsequently primes the specific adaptive immune response during infection [1, 2]. The activation of TLR has implications for antiviral defence and has contributions for tumour suppression including apoptosis and anti-angiogenesis [3,4,5]. MicroRNAs are small noncoding RNAs that regulate gene expression at the post-transcriptional level and have been as a critical regulatory factor in the mammalian immune system [6, 7]. MicroRNAs has been documented to play vital roles in TLR immunity and been as the fine-tuners of TLR signalling [8, 9]. The members of the let-7 microRNA family [10] and miR-105 can regulate mRNA level of TLR4 and TLR2 respectively [11]. The activation of TLR signals can induce microRNAs
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