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Methylated glycans as conserved targets of animal and fungal innate defense.
Wohlschlager, Therese Butschi, Alex Grassi, Paola Sutov, Grigorij Gauss, Robert Hauck, Dirk Schmieder, Stefanie S Knobel, Martin Titz, Alexander Dell, Anne
Wohlschlager, Therese
Butschi, Alex
Grassi, Paola
Sutov, Grigorij
Gauss, Robert
Hauck, Dirk
Schmieder, Stefanie S
Knobel, Martin
Titz, Alexander
Dell, Anne
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2014-07-08
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Abstract
Effector proteins of innate immune systems recognize specific non-self epitopes. Tectonins are a family of β-propeller lectins conserved from bacteria to mammals that have been shown to bind bacterial lipopolysaccharide (LPS). We present experimental evidence that two Tectonins of fungal and animal origin have a specificity for O-methylated glycans. We show that Tectonin 2 of the mushroom Laccaria bicolor (Lb-Tec2) agglutinates Gram-negative bacteria and exerts toxicity toward the model nematode Caenorhabditis elegans, suggesting a role in fungal defense against bacteria and nematodes. Biochemical and genetic analysis of these interactions revealed that both bacterial agglutination and nematotoxicity of Lb-Tec2 depend on the recognition of methylated glycans, namely O-methylated mannose and fucose residues, as part of bacterial LPS and nematode cell-surface glycans. In addition, a C. elegans gene, termed samt-1, coding for a candidate membrane transport protein for the presumptive donor substrate of glycan methylation, S-adenosyl-methionine, from the cytoplasm to the Golgi was identified. Intriguingly, limulus lectin L6, a structurally related antibacterial protein of the Japanese horseshoe crab Tachypleus tridentatus, showed properties identical to the mushroom lectin. These results suggest that O-methylated glycans constitute a conserved target of the fungal and animal innate immune system. The broad phylogenetic distribution of O-methylated glycans increases the spectrum of potential antagonists recognized by Tectonins, rendering this conserved protein family a universal defense armor.
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Methylated glycans as conserved targets of animal and fungal innate defense. 2014, 111 (27):E2787-96 Proc. Natl. Acad. Sci. U.S.A.
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Article
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en
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1091-6490
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Archived with thanks to Proceedings of the National Academy of Sciences of the United States of America