Cell Biology and Immunology Group, Wageningen Institute of Animal Sciences, Wageningen University, PO Box 338, 6700 AH, Wageningen, The Netherlands.
Immunogenetics. 2014 Feb;66(2):123-41. doi: 10.1007/s00251-013-0751-4. Epub 2013 Dec 11.
Like other vertebrate Toll-like receptors (TLRs), the TLRs of teleost fish can be subdivided into six major families, each of which recognize a general class of molecular patterns. However, there also are a number of Tlrs with unknown function, the presence of which seems unique to the bony fish, among which is Tlr20. We identified full-length complementary DNA (cDNA) sequences for tlr20 of zebrafish and common carp, two closely related fish species. Zebrafish have six copies of tlr20, whereas carp express only a single copy. Both zebrafish Tlr20 (at least Tlr20a-d) and carp Tlr20 have 26 leucine-rich repeats (LRRs). Three-dimensional modeling indicates a best fit to the crystal structure of TLR8. Phylogenetic analyses place Tlr20 in the TLR11 family closest to Tlr11 and Tlr12, which sense ligands from protozoan parasites in the mouse. Conservation of genes on zebrafish chromosome 9, which carries tlr20, with genes on mouse chromosome 14, which carries tlr11, indicates Tlr11 could be a possible ortholog of Tlr20. Confocal microscopy suggests a subcellular localization of Tlr20 at the endoplasmatic reticulum. Although in vitro reporter assays could not identify a ligand unique to Tlr20, in vivo infection experiments indicate a role for Tlr20 in the immune response of carp to protozoan parasites (Trypanoplasma borreli). Carp tlr20 is mainly expressed in peripheral blood leukocytes (PBL) with B lymphocytes, in particular, expressing relatively high levels of Tlr20. In vitro stimulation of PBL with T. borreli induces an upregulation of tlr20, supportive of a role for Tlr20 in the immune response to protozoan parasites.
像其他脊椎动物 Toll 样受体 (TLRs) 一样，鱼类的 TLRs 可分为六个主要家族，每个家族都能识别一类普遍的分子模式。然而，也有一些 TLR 的功能未知，它们的存在似乎是硬骨鱼类所特有的，其中就包括 Tlr20。我们鉴定了两种密切相关的鱼类，斑马鱼和鲤鱼的 tlr20 的全长 cDNA（cDNA）序列。斑马鱼有 6 个 tlr20 拷贝，而鲤鱼只表达一个拷贝。斑马鱼 Tlr20（至少是 Tlr20a-d）和鲤鱼 Tlr20 都有 26 个亮氨酸丰富重复（LRR）。三维建模表明与 TLR8 的晶体结构拟合度最佳。系统发育分析将 Tlr20 置于 TLR11 家族中，与 TLR11 和 TLR12 最接近，后者在小鼠中可感应原生动物寄生虫的配体。携带 tlr20 的斑马鱼染色体 9 上的基因与携带 tlr11 的小鼠染色体 14 上的基因保守，表明 TLR11 可能是 Tlr20 的一个可能的同源基因。共聚焦显微镜显示 Tlr20 在内质网上的亚细胞定位。尽管体外报告基因检测未能鉴定出 Tlr20 特有的配体，但体内感染实验表明 Tlr20 在鲤鱼对原生动物寄生虫（Borrelia trypanoplasma）的免疫反应中发挥作用。鲤鱼 tlr20 主要在外周血白细胞（PBL）中表达，其中 B 淋巴细胞表达相对较高水平的 Tlr20。用 T. borreli 体外刺激 PBL 可诱导 tlr20 的上调，支持 Tlr20 在对原生动物寄生虫的免疫反应中的作用。
