alpha-Neup5Ac-(2--3)-beta-D-Galp-(1--4)-[alpha-L-Fucp-(1--3)]-D-GlcpNAc and Leukemia--Promyelocytic--Acute

Free, monovalent, SLeX (Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3)-GlcNAc), SLn (Neu5Ac alpha 2-3Gal beta 1-4GlcNAc) and corresponding BSA-conjugated forms--displaying different ratios of SLeX and SLn to protein--were tested for their ability to inhibit binding of HL-60 cells to immobilized E-selectin. Free SLeX and conjugated SLeX-BSA inhibited cell binding in a dose-dependent manner. SLn and SLn-BSA did not inhibit binding. SLeX16BSA (16 mol tetrasaccharide/mol BSA) and monovalent SLeX inhibited cell binding with measured inhibitory concentrations (IC50S) of 1 microM and 1 mM, respectively, demonstrating a three-order-of-magnitude enhancement of inhibitory activity with the multivalent form of SLeX. A SLex7BSA conjugate was 10-fold less potent than those with 11 or 16 mol SLeX/mol BSA. An assay which measured neutrophil rolling on interleukin (IL)-1 beta-activated human umbilical vein endothelial cells (HUVECs) showed 50% reduction in the number of rolling neutrophils in the presence of 1 microM SLeX16BSA, whereas the level of free, monovalent SLeX oligosaccharide required to produce the same effect was approximately 0.3 mM. SLeX-BSA was found to be an excellent reagent for staining endothelial cells expressing E-selectin. Biotinylated SLeX-BSA in conjunction with Texas red avidin-stained lipopolysaccharide (LPS)-activated HUVECs, and co-incubation of activated cells with anti-E-selectin, specifically blocked staining. The distribution of E-selectin, as determined by binding of SLeX-BSA, was virtually identical with that obtained by binding of anti-E-selectin antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Cell Adhesion; Cell Adhesion Molecules; E-Selectin; Endothelium, Vascular; Humans; Indicators and Reagents; Interleukin-1; Leukemia, Promyelocytic, Acute; Lipopolysaccharides; Neutrophils; Oligosaccharides; Sialyl Lewis X Antigen; Staining and Labeling; Tumor Cells, Cultured; Umbilical Veins; Xanthenes

Activated platelets expressing P-selectin on their surface are known to adhere to monocytes and neutrophils. We examined the possibility that the leukocytes were activated by their adhesion to activated platelets and demonstrated that P-selectin-dependent platelet adhesion to neutrophils and monocytes induced production of extracellular superoxide anion (O2-) by these leukocytes. Leukocyte membrane glycoproteins containing Ser/Thr-linked carbohydrate chains were responsible for the signal reception leading to the leukocyte activation. Cytokines were shown to influence these processes. For example, treatments of neutrophils with interleukin-8 (IL-8) or granulocyte colony-stimulating factor (G-CSF) potentiated the P-selectin-induced O2- production. Furthermore, interleukin-1 (IL-1) and interferon-gamma (IFN-gamma) induced surface expression of P-selectin on platelets in the presence of a low concentration of thrombin and consequently enhanced their adhesion capacity to leukocytes. These results indicated that the adhesion of activated platelets to the leukocytes through the interaction between P-selectin and its carbohydrate ligand, sialyl Lewis X (LeX), was a crucial step for the activation of leukocyte function and supported the notion that activated platelets were actively involved in the inflammatory processes.

Topics: Blood Platelets; Humans; Inflammation; Leukemia, Promyelocytic, Acute; Monocytes; Neutrophils; Oligosaccharides; P-Selectin; Platelet Activation; Platelet Membrane Glycoproteins; Sialyl Lewis X Antigen; Superoxides; Tumor Cells, Cultured

The sialyl Lewis x determinant (NeuAc alpha 2,3Gal beta 1, 4[Fuc alpha 1,3]GlcNAc) is an essential component of leukocyte counterreceptors for E-selectin and P-selectin. The final step in sialyl Lewis x synthesis is catalyzed by alpha-1,3-fucosyltransferases acting on sialylated glycoconjugate precursors. Cultured human leukocytic cell lines express an alpha-1,3-fucosyltransferase gene termed Fuc-TIV or ELFT but do not express the other three cloned human alpha-1,3-fucosyltransferase genes to any significant degree. The physiological role of Fuc-TIV/ELFT in sialyl Lewis x biosynthesis is uncertain, however, since it can catalyze the synthesis of this determinant in some, but not all, transfected cell lines in a manner that is dependent upon the glycosylation phenotype of the host cell. We report here the molecular cloning of a cDNA encoding a new human leukocyte alpha-1,3-fucosyltransferase, termed Fuc-TVII, capable of synthesizing the sialyl Lewis x moiety. The cDNA sequence predicts a 341-amino acid-long type II transmembrane protein typical of mammalian glycosyltransferases. When expressed in mammalian cells, the Fuc-TVII cDNA directs the synthesis of cell surface sialyl Lewis x moieties but not the Lewis x, Lewis a, sialyl Lewis a, or VIM-2 determinants. Fuc-TVII can efficiently utilize alpha-2,3-sialyllactosamine in vitro to form the sialyl Lewis x tetrasaccharide but does not utilize lactosamine to form the Lewis x moiety. Northern blot analyses show that the Fuc-TVII gene is transcribed in HL-60 cells, a human promyelocytic cell line, and in YT cells, a natural killer-like cell line. Fuc-TVII represents a leukocytic alpha-1,3-fucosyltransferase that can participate in selectin ligand synthesis via its ability to catalyze the synthesis of sialyl Lewis x determinants.

Topics: Amino Acid Sequence; Animals; Base Sequence; Carbohydrate Sequence; Cell Line; Chlorocebus aethiops; CHO Cells; Chromosome Mapping; Chromosomes, Human, Pair 11; Cloning, Molecular; Cricetinae; DNA; DNA Primers; DNA, Complementary; Fucosyltransferases; Humans; Killer Cells, Natural; Leukemia, Promyelocytic, Acute; Leukocytes; Mice; Molecular Sequence Data; Oligosaccharides; Polymerase Chain Reaction; Protein Structure, Secondary; Recombinant Proteins; Sequence Homology, Amino Acid; Sialyl Lewis X Antigen; Substrate Specificity; Transfection; Tumor Cells, Cultured