title: GalNAc/Gal-binding Rhizoctonia solani agglutinin has antiproliferative activity in Drosophila melanogaster S2 cells via MAPK and JAK/STAT signaling.
abstract: Rhizoctonia solani agglutinin, further referred to as RSA, is a lectin isolated from the plant pathogenic fungus Rhizoctonia solani. Previously, we reported a high entomotoxic activity of RSA towards the cotton leafworm Spodoptera littoralis. To better understand the mechanism of action of RSA, Drosophila melanogaster Schneider S2 cells were treated with different concentrations of the lectin and FITC-labeled RSA binding was examined using confocal fluorescence microscopy. RSA has antiproliferative activity with a median effect concentration (EC(50)) of 0.35 µM. In addition, the lectin was typically bound to the cell surface but not internalized. In contrast, the N-acetylglucosamine-binding lectin WGA and the galactose-binding lectin PNA, which were both also inhibitory for S2 cell proliferation, were internalized whereas the mannose-binding lectin GNA did not show any activity on these cells, although it was internalized. Extracted DNA and nuclei from S2 cells treated with RSA were not different from untreated cells, confirming inhibition of proliferation without apoptosis. Pre-incubation of RSA with N-acetylgalactosamine clearly inhibited the antiproliferative activity by RSA in S2 cells, demonstrating the importance of carbohydrate binding. Similarly, the use of MEK and JAK inhibitors reduced the activity of RSA. Finally, RSA affinity chromatography of membrane proteins from S2 cells allowed the identification of several cell surface receptors involved in both signaling transduction pathways.
authors.affiliation: Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium.
authors.forename: Mohamad
authors.initials: M
authors.lastname: Hamshou
authors.forename: Els J M
authors.initials: EJ
authors.lastname: Van Damme
authors.forename: Gianni
authors.initials: G
authors.lastname: Vandenborre
authors.forename: Bart
authors.initials: B
authors.lastname: Ghesquière
authors.forename: Geert
authors.initials: G
authors.lastname: Trooskens
authors.forename: Kris
authors.initials: K
authors.lastname: Gevaert
authors.forename: Guy
authors.initials: G
authors.lastname: Smagghe
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism; D000373:Agglutinins / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D004187:Disaccharides / Q000378:metabolism; D004331:Drosophila melanogaster / Q000187:drug effects / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism / Q000494:pharmacology; D005690:Galactose / Q000378:metabolism; D053612:Janus Kinases / Q000378:metabolism*; D037102:Lectins / Q000378:metabolism / Q000494:pharmacology*; D008565:Membrane Proteins / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D037121:Plant Lectins / Q000378:metabolism; D011485:Protein Binding; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D040901:Proteomics; D012232:Rhizoctonia / Q000737:chemistry; D050791:STAT Transcription Factors / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D000373:Agglutinins; D004187:Disaccharides; D005656:Fungal Proteins; D037102:Lectins; D008565:Membrane Proteins; D037121:Plant Lectins; D047428:Protein Kinase Inhibitors; D050791:STAT Transcription Factors; D053612:Janus Kinases; D020928:Mitogen-Activated Protein Kinases; D000117:Acetylglucosamine; D005690:Galactose