title: Identification and characterization of a novel intelectin in the digestive tract of Xenopus laevis.
abstract: The intelectin (Intl) family is a group of secretory lectins in chordates that serve multiple functions, including innate immunity, through Ca(2+)-dependent recognition of carbohydrate chains. Although six Intl family lectins have so far been reported in Xenopus laevis, none have been identified in the intestine. Using a monoclonal antibody to the Xenopus embryonic epidermal lectin (XEEL or Intl-1), I identified cross-reactive proteins in the intestines. The proteins were purified by affinity chromatography on a galactose-Sepharose column and found to be oligomers consisting of N-glycosylated 39 kDa and 40.5 kDa subunit peptides. N-terminal amino acid sequencing of these peptides, followed by cDNA cloning, identified two novel Intls (designated Intl-3 and Intl-4) that showed 59-79% amino acid identities with known Xenopus Intl family proteins. From the amino acid sequence, immunoreactivity, and properties of the recombinant protein, Intl-3 was considered the intestinal lectin identified by the anti-XEEL antibody. The purified Intl-3 protein could potentially bind to Escherichia coli and its lipopolysaccharides (LPS), and to Staphylococcus aureus and its peptidoglycans, depending on Ca(2+). In addition, the Intl-3 protein agglutinated E. coli cells in the presence of Ca(2+). Intraperitoneal injection of LPS increased the intestinal and rectal contents of Intl-3 and XCL-1 (or 35K serum lectin) proteins within three days; however, unlike XCL-1, Intl-3 was detectable in neither the sera nor the other tissues regardless of LPS stimulation. Immunohistochemical analyses revealed accumulation of the Intl-3 protein in mucus secretory granules of intestinal goblet cells. The results of this study suggest that Xenopus Intl-3 is involved in the innate immune protection of the digestive tract against bacterial infections.
authors: Department of Chemical and Biological Sciences, Faculty of Science, Japan Women's University, Mejirodai 2-8-1, Bunkyoku, Tokyo 112-8681, Japan. Electronic address: s-nagata@fc.jwu.ac.jp.
authors: Saburo
authors: S
authors: Nagata
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003001:Cloning, Molecular; D016207:Cytokines / Q000235:genetics / Q000276:immunology*; D004926:Escherichia coli / Q000276:immunology; D041981:Gastrointestinal Tract / Q000276:immunology*; D007113:Immunity, Innate / Q000235:genetics / Q000276:immunology; D007413:Intestinal Mucosa / Q000276:immunology* / Q000378:metabolism; D007422:Intestines / Q000276:immunology*; D037102:Lectins / Q000235:genetics / Q000276:immunology*; D008070:Lipopolysaccharides / Q000378:metabolism; D010457:Peptidoglycan / Q000276:immunology; D011485:Protein Binding / Q000276:immunology; D017434:Protein Structure, Tertiary; D013211:Staphylococcus aureus / Q000276:immunology; D029867:Xenopus Proteins / Q000276:immunology*; D014982:Xenopus laevis / Q000276:immunology*
chemical_list: D016207:Cytokines; C502725:ITLN2 protein, Xenopus; C000613267:Intl-3 protein, Xenopus; C000613268:Intl-4 protein, Xenopus; D037102:Lectins; D008070:Lipopolysaccharides; D010457:Peptidoglycan; D029867:Xenopus Proteins; D002118:Calcium
keywords: Bacterial lipopolysaccharide (LPS); Goblet cells; Innate immunity; Lectin; Omentin; Xenopus