MicroRNAs: new regulators of Toll-like receptor signalling pathways

Abstract

Toll-like receptors (TLRs), a critical family of pattern recognition receptors (PRRs), are responsible for the innate immune responses via signalling pathways to provide effective host defence against pathogen infections. However, TLR-signalling pathways are also likely to stringently regulate tissue maintenance and homeostasis by elaborate modulatory mechanisms. MicroRNAs (miRNAs) have emerged as key regulators and as an essential part of the networks involved in regulating TLR-signalling pathways. In this review, we highlight our understanding of the regulation of miRNA expression profiles by TLR-signalling pathways and the regulation of TLR-signalling pathways by miRNAs. We focus on the roles of miRNAs in regulating TLR-signalling pathways by targeting multiple molecules, including TLRs themselves, their associated signalling proteins and regulatory molecules, and transcription factors and functional cytokines induced by them, at multiple levels.

Figure 1

The fine-tuning of the TLR-signalling pathways by miRNAs. An array of miRNAs are involved in regulating of the TLR-signalling pathways and innate immune responses by targeting multiple molecules at multiple levels, including TLRs themselves, TLR-associated signalling proteins, TLR-associated regulatory molecules, TLR-induced transcription factors, and TLR-induced functional cytokines.