Fukui Ryutaro, Yamamoto Chikako, Matsumoto Fumi, Onji Masahiro, Shibata Takuma, Murakami Yusuke, Kanno Atsuo, Hayashi Takuto, Tanimura Natsuko, Yoshida Nobuaki, Miyake Kensuke
Division of Innate Immunity, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria.
Front Immunol. 2018 Jun 27;9:1491. doi: 10.3389/fimmu.2018.01491. eCollection 2018.
Mouse toll-like receptor 9 (TLR9) is an endosomal sensor for single-stranded DNA. TLR9 is transported from the endoplasmic reticulum to endolysosomes by a multiple transmembrane protein Unc93 homolog B1, and proteolytically cleaved at its ectodomain. The structure of TLR9 and its biochemical analyses have shown that the proteolytic cleavage of TLR9 ectodomain enables TLR9-dimerization and TLR9 activation. However, the requirement of TLR9 cleavage has not been studied. We here show that the 13 amino acids deletion at the cleavage site made TLR9 resistant to proteolytic cleavage. The deletion mutation in the gene impaired TLR9-dependent cytokine production in conventional dendritic cells from the mutant mice. Not only production of inflammatory cytokines (TNF-α and IL-12p40), chemokine (CCR5/RANTES), and type I interferon (IFN-α) induced by administration of TLR9 ligand was also impaired. These results demonstrate that the TLR9 cleavage is required for TLR9 responses .
小鼠Toll样受体9（TLR9）是一种用于检测单链DNA的内体传感器。TLR9通过一种多次跨膜蛋白Unc93同源物B1从内质网转运至内溶酶体，并在其胞外结构域进行蛋白水解切割。TLR9的结构及其生化分析表明，TLR9胞外结构域的蛋白水解切割可使TLR9二聚化并激活TLR9。然而，TLR9切割的必要性尚未得到研究。我们在此表明，切割位点处13个氨基酸的缺失使TLR9对蛋白水解切割具有抗性。该基因中的缺失突变损害了突变小鼠常规树突状细胞中TLR9依赖性细胞因子的产生。不仅通过给予TLR9配体诱导的炎性细胞因子（TNF-α和IL-12p40）、趋化因子（CCR5/RANTES）和I型干扰素（IFN-α）的产生也受到损害。这些结果表明，TLR9切割是TLR9应答所必需的。
