D-Galactose-Specific Sea Urchin Lectin Sugar-Specifically Inhibited Histamine Release Induced by Datura stramonium Agglutinin: Differences Between Sugar-Specific Effects of Sea Urchin Lectin and Those of D-Galactose- or L-Fucose-Specific Plant Lectins

Abstract

ABSTRACT-A new sea urchin lectin from Toxopneustes pileolus, is D(+)galactose (Gal)-, D(+)fucose (Fuc)-specific. Incubation of rat peritoneal mast cells with the lectin in the presence of 0.3 mM CaCl 2 for 10 min significantly and dose-dependently inhibited the histamine release induced by N-acetyl glucosamine (GlcNAc)-specific Datura stramonium agglutinin (DSA), an activator of the G i-protein-dependent pathway in mast cells. This inhibition by the sea urchin lectin was sugar-specifically reversed in the presence ofThe sea urchin lectin had no effect on the histamine release induced by compound 48/80, slightly inhibited the histamine release induced by substance P and mastoparan, and slightly enhanced the histamine release induced by melittin, but these effects were not dose-dependent. Compound 48/ 80, substance P, mastoparan and melittin are mast cell activators without sugar residues. It is suggested that the lectin binds to D(+)Gal residues of DSA to interfere with mast cell activation induced by DSA, a glycoprotein with arabinose and Gal residues. The effects of plant lectins with affinity to D(+)Gal, N-acetyl galactosamine and/ or sialic acid and L(-)Fuc on the histamine release induced by DSA, compound 48 /80 and substance P were also examined.Keywords: Mast cell, Histamine release, Datura stramonium agglutinin, D(+)Galactose-specific lectin, Compound 48/ 80, Substance PThe toxopneustid sea urchins, Toxopneustes pileolus and Tripneustes gratilla, have external appendages (pedicellariae and/ or spines) that contain various bioactive proteins, such as venoms and lectins (1). Bioactive proteins from the large globiferous pedicellariae of T. pileolus induced contraction in isolated longitudinal muscles of guinea pigs in a dose-dependent manner, induced hemagglutination of horse and mouse erythrocytes without hemolysis, and showed chemotactic properties for guinea pig neutrophils (1, 2). Three fractions, named the P-I, P-II and P-III fraction, were obtained from T. pileolus. The P-I fraction was not bioactive and the P-II fraction contained contractin A. Our recent study has revealed that sea urchin lectin-I (SUL-I), a monomeric protein (32 kDa) with 294 amino acid residues from the large globiferous peidcellariae of T. pileolus, is D(+)galactose (Gal)-, D(+)fucose (Fuc)-and D(+)galacturonic acid-specific, but not L(-)Fucspecific. SUL-I is a novel lectin, a major component of the P-III fraction, and different from contractin A, a 18-kDa glycoprotein from T. pileolus (1) and the toxin of 25 kDa from T. gratilla reported by Mebs (3). The P-III fraction containing SUL-I exhibits mitogenic stimulation in murine splenocytes and mesenteric lymphocytes (2, 4).Rodent peritoneal mast cells have two activation pathways, one IgE and tyrosine kinase-dependent, the other IgEindependent and Gi-protein-coupled. The latter pathway differs from the former pathway in that it is pertussis toxinsensitive. Matsuda et al. (5) showed that Datura stramonium agglutinin (DSA) N-acetyl glucosamine (GlcNAc)-specifically and dose-depende...