Toll-like receptors in the functional orientation of cardiac progenitor cells复制标题

Toll样受体在心脏祖细胞功能定位中的作用

TLRs are composed of family, which response to pathogen‐associated molecular patterns (PAMPs) expressed by a numerous group of infectious microorganisms. This family is a group of transmembrane proteins that are highly conserved in all animals from insects to humans. Identification and classification of TLRs shed light on the better understanding of the innate immune system and/or cell function. Up to date, 10 members of TLRs in human and 13 orthologous members have been discovered in mice. According to the subcellular localization of TLRs, they can be divided into two main groups, including TLR1, 2, 4, 6, and 11 expressed on the plasma membrane, but other members TLR3, 7, 8, and 9 existed in the endolysosomal compartments. Each of the members of this family has specific cognate ligands. For example, TLR‐1 in cooperation with TLR‐6 or TLR‐2 can recognize different bacterial composites such as peptidoglycan, lipoprotein, and lipopeptides. Many viruses with double strand RNA are recognized by TLR3, while TLR‐7 and TLR‐8 recognize single strand RNA and imidazoquinolines. Also, TLR‐4 and TLR‐5 specifically attach to lipopolysaccharide and bacterial flagellin, respectively. TLR‐9 has a critical role in identifying oligodeoxynucleotides (CpG) motifs. The extracellular domain of TLRs contains leucine‐rich repeats that interfere with PAMPs recognition and the intracellular domain contains toll‐interleukin 1 (IL‐1) receptor required for downstream signal transduction. TLRs per se stimulate the intracellular signaling pathway by the recognition of the PAMPs, leading to the synthesis of inflammatory cytokines, type one interferon (IFN) and chemokine. By involving TLRs with their own PAMPs, the promotion of related signals results in activation of nuclear factor kappa‐light‐chain‐enhancer of activated B cells NF‐kB and activator protein 1. In addition, TLRs have a critical role in coronary heart diseases, asthma, inflammatory bowel diseases and so forth.

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