title: Nematotoxicity of Marasmius oreades agglutinin (MOA) depends on glycolipid binding and cysteine protease activity.
abstract: Fruiting body lectins have been proposed to act as effector proteins in the defense of fungi against parasites and predators. The Marasmius oreades agglutinin (MOA) is a Galα1,3Gal/GalNAc-specific lectin from the fairy ring mushroom that consists of an N-terminal ricin B-type lectin domain and a C-terminal dimerization domain. The latter domain shows structural similarity to catalytically active proteins, suggesting that, in addition to its carbohydrate-binding activity, MOA has an enzymatic function. Here, we demonstrate toxicity of MOA toward the model nematode Caenorhabditis elegans. This toxicity depends on binding of MOA to glycosphingolipids of the worm via its lectin domain. We show further that MOA has cysteine protease activity and demonstrate a critical role of this catalytic function in MOA-mediated nematotoxicity. The proteolytic activity of MOA was dependent on high Ca(2+) concentrations and favored by slightly alkaline pH, suggesting that these conditions trigger activation of the toxin at the target location. Our results suggest that MOA is a fungal toxin with intriguing similarities to bacterial binary toxins and has a protective function against fungivorous soil nematodes.
authors.affiliation: Institutes of Microbiology, CH-8093 Zürich.
authors.forename: Therese
authors.initials: T
authors.lastname: Wohlschlager
authors.affiliation: Institute of Molecular Life Sciences, University of Zürich, CH-8057 Zürich, CH-8057 Zürich, Switzerland.
authors.forename: Alex
authors.initials: A
authors.lastname: Butschi
authors.affiliation: Institutes of Microbiology, CH-8093 Zürich.
authors.forename: Katrin
authors.initials: K
authors.lastname: Zurfluh
authors.affiliation: Institute of Molecular Life Sciences, University of Zürich, CH-8057 Zürich, CH-8057 Zürich, Switzerland.
authors.forename: Sibylle C
authors.initials: SC
authors.lastname: Vonesch
authors.affiliation: Cell Biology, ETH Zürich, CH-8093 Zürich.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Auf dem Keller
authors.affiliation: Functional Genomics Center, University and ETH Zürich, CH-8057 Zürich, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Gehrig
authors.affiliation: Institutes of Microbiology, CH-8093 Zürich.
authors.forename: Silvia
authors.initials: S
authors.lastname: Bleuler-Martinez
authors.affiliation: Institute of Molecular Life Sciences, University of Zürich, CH-8057 Zürich, CH-8057 Zürich, Switzerland.
authors.forename: Michael O
authors.initials: MO
authors.lastname: Hengartner
authors.affiliation: Institutes of Microbiology, CH-8093 Zürich.
authors.forename: Markus
authors.initials: M
authors.lastname: Aebi
authors.affiliation: Institutes of Microbiology, CH-8093 Zürich. Electronic address: markus.kuenzler@micro.biol.ethz.ch.
authors.forename: Markus
authors.initials: M
authors.lastname: Künzler
mesh_terms: D000373:Agglutinins / Q000737:chemistry*; D000818:Animals; D001665:Binding Sites; D017173:Caenorhabditis elegans; D002118:Calcium / Q000737:chemistry; D002384:Catalysis; D057056:Cysteine Proteases / Q000737:chemistry*; D019281:Dimerization; D017353:Gene Deletion; D006017:Glycolipids / Q000737:chemistry*; D006028:Glycosphingolipids / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D037102:Lectins / Q000737:chemistry*; D008024:Ligands; D055433:Marasmius / Q000378:metabolism*; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D000373:Agglutinins; D006017:Glycolipids; D006028:Glycosphingolipids; D037102:Lectins; D008024:Ligands; D057056:Cysteine Proteases; D002118:Calcium