title: ST2 from rainbow trout quenches TLR signalling, localises at the nuclear membrane and allows the nuclear translocation of MYD88.
abstract: The mammalian interleukin 1 receptor-like 1 receptor (IL1RL1), commonly known as ST2, is thought to downregulate TLR signalling by sequestering the signalling adapter MYD88 (myeloid differentiation primary response protein 88). ST2 sequences are known in several fish species, but none of them have functionally been examined. We characterised ST2 from rainbow trout (Oncorhynchus mykiss) and the structure of its encoding gene. The primary sequence of ST2 is only weakly conserved from fish to human. However, the amino acid sequences forming the interfaces for ST2 and MYD88 interaction are well conserved throughout evolution. High similarity of the gene segmentation unambiguously proves the common ancestry of fish and mammalian ST2. Trout ST2 and trout MYD88 genes were constitutively expressed in embryonic, larval and adult trout. In vivo infection with Aeromonas salmonicida did not modulate the mRNA levels of both factors. Overexpressing trout ST2 in the mammalian HEK-293 reconstitution system of TLR2 signalling quenched the Escherichia coli-induced activation of NF-κB and SAA promoters in a dose-dependent fashion. The expression of GFP-tagged trout ST2 in human HEK-293 or trout CHSE-214 cells surprisingly revealed that (i) ST2 localised abundantly at the nuclear membrane rather than at the cell membrane and (ii) the coexpression of both ST2 and MYD88 allowed the translocation of trout MYD88 from cytoplasm to nucleus, as assessed using confocal microscopy and Western blotting. Hence, we validated that trout ST2 is a dampener of TLR signalling and interacts with MYD88. The spatial distribution of these factors raises questions about how this repressive mechanism functions.
authors: Leibniz Institute for Farm Animal Biology (FBN), Institute for Genome Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany.
authors: Alexander
authors: A
authors: Rebl
authors: Rostock University Medical Center, Department of Cell Biology, Schillingallee 69, 18057, Rostock, Germany.
authors: Henrike
authors: H
authors: Rebl
authors: Leibniz Institute for Farm Animal Biology (FBN), Institute for Genome Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany.
authors: Judith M
authors: JM
authors: Köbis
authors: Leibniz Institute for Farm Animal Biology (FBN), Institute for Genome Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany.
authors: Tom
authors: T
authors: Goldammer
authors: Leibniz Institute for Farm Animal Biology (FBN), Institute for Genome Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany. Electronic address: seyfert@fbn-dummerstorf.de.
authors: Hans-Martin
authors: HM
authors: Seyfert
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D005075:Biological Evolution; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D000072179:Interleukin-1 Receptor-Like 1 Protein / Q000235:genetics / Q000378:metabolism*; D008322:Mammals; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism*; D009685:Nuclear Envelope / Q000378:metabolism*; D017686:Oncorhynchus mykiss / Q000276:immunology*; D011485:Protein Binding; D021381:Protein Transport; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000378:metabolism
chemical_list: D029941:Fish Proteins; C079241:IL1RL1 protein, human; D000072179:Interleukin-1 Receptor-Like 1 Protein; D053594:Myeloid Differentiation Factor 88; D051193:Toll-Like Receptors
keywords: CHSE-214; Evolution; HEK-293; Interleukin 1 receptor-like 1; Oncorhynchus mykiss; TIR-domain; Toll-like receptor signalling