TLR7/8 stress response drives histiocytosis in SLC29A3 disorders
Takuma Shibata, Ryota Sato, Masato Taoka, Shin-ichiroh Saitoh, Mayumi Komine, Kiyoshi Yamaguchi, Susumu Goyama, Yuji Motoi, Jiro Kitaura, Kumi Izawa, Yoshio Yamauchi, Yumiko Tsukamoto, Takeshi Ichinohe, E. Fujita, Ryosuke Hiranuma, Ryutaro Fukui, Yoichi Furukawa, Toshio Kitamura, Toshiyuki Takai, Arinobu Tojo, Mamitaro Ohtsuki, Umeharu Ohto, Toshiyuki Shimizu, Manabu Ozawa, Nobuaki Yoshida, Toshiaki Isobe, Eicke Latz, Kojiro Mukai, Tomohiko Taguchi, Hiroaki Hemmi, Shizuo Akira, Kensuke Miyake
Abstract
Loss-of-function mutations in the lysosomal nucleoside transporter SLC29A3 cause lysosomal nucleoside storage and histiocytosis: phagocyte accumulation in multiple organs. However, little is known about the mechanism by which lysosomal nucleoside storage drives histiocytosis. Herein, histiocytosis in Slc29a3-/- mice was shown to depend on Toll-like receptor 7 (TLR7), which senses a combination of nucleosides and oligoribonucleotides (ORNs). TLR7 increased phagocyte numbers by driving the proliferation of Ly6Chi immature monocytes and their maturation into Ly6Clow phagocytes in Slc29a3-/- mice. Downstream of TLR7, FcRγ and DAP10 were required for monocyte proliferation. Histiocytosis is accompanied by inflammation in SLC29A3 disorders. However, TLR7 in nucleoside-laden splenic monocytes failed to activate inflammatory responses. Enhanced production of proinflammatory cytokines was observed only after stimulation with ssRNAs, which would increase lysosomal ORNs. Patient-derived monocytes harboring the G208R SLC29A3 mutation showed enhanced survival and proliferation in a TLR8-antagonist-sensitive manner. These results demonstrated that TLR7/8 responses to lysosomal nucleoside stress drive SLC29A3 disorders.