concanavalin-a and castanospermine

Two new C-1 epimeric hydroxymethyl castanospermine congeners 2a and 2b, synthesized by stereocontrolled intramolecular double reductive amination of D-glucose derived beta-keto ester as a key step, showed impressive immuno-potentiating property. The bioactivity was mediated through up-regulation of T(H1)/T(H2) cytokine ratio. The finding suggested that immunmodulatory activity of polyhydroxylated indolizidine alkaloids can be tuned by minor structural/stereochemical alterations.

Topics: Adjuvants, Immunologic; Animals; Cell Proliferation; Concanavalin A; Cytokines; Drug Synergism; Indolizines; Mice; Spleen; Stereoisomerism; Th1 Cells; Th2 Cells

Glycosidase trimming inhibitors may be used to study contribution of N-linked glycan moieties in T cell function. We have studied the effects of castanospermine (Cas), swainsonine (Swain), 1-deoxynojirimycin (dNM), and 1-deoxymannojirimycin (dMM) on T cell activation and differentiation. Our analysis included a new dNM derivative, N-pentyl-1-deoxynojirimycin (pentyldNM). Previous reports showed inhibitory action of trimming inhibitors, such as Swain and Cas, on pokeweed mitogen-driven immunoglobulin (Ig) production. We extend these findings for pentyldNM and observed that glucosidase inhibitors, Cas and pentyldNM were effective in inhibiting CD2 and CD3 monoclonal antibody (mAb) driven Ig production. The pattern of inhibition by mannosidase and glucosidase inhibitors correlated with inhibitory action on T cell activation: only glucosidase trimming inhibitors (Cas and pentyldNM with comparable potency) perturbed mAb-induced T cell activation, in particular if induced by CD2 mAb. Expression of the early activation marker CD69 was not decreased in the presence of these inhibitors, while addition of exogenous recombinant interleukin-2 partially overcame inhibitory effects during proliferation. These findings suggest that glucosidase, but not mannosidase, trimming inhibitors interfere with a late phase of T cell activation. In addition, the enhanced sensitivity of CD2 mAb-induced proliferation for glucosidase trimming inhibitors suggests dependence on N-linked glycans during CD2-mediated adhesion and triggering functions.

Topics: 1-Deoxynojirimycin; Antibodies, Monoclonal; Antigens, Differentiation, T-Lymphocyte; CD2 Antigens; CD3 Complex; Concanavalin A; Glucose; Glucosidases; Humans; Immunoglobulins; Indolizines; Interleukin-2; Leukocytes, Mononuclear; Lymphocyte Activation; Mannosidases; Phytohemagglutinins; Pokeweed Mitogens; Polysaccharides; Receptors, Immunologic; Recombinant Proteins; Stimulation, Chemical; Swainsonine; T-Lymphocytes

Natural killer cells select targets for lysis based on target cell glycoproteins. Compared to controls, K-562 cells treated with kifunensine, an inhibitor of Golgi mannosidase I, accumulate more high mannose-type asparagine-linked oligosaccharide, Man9GlcNAc2, and bind more concanavalin A, an oligomannosyl binding lectin. In addition, natural killer cell lysis of kifunensine-treated cells increases 34% over that of controls. Increased sensitivity to lysis occurs after treatment with other N-glycan processing inhibitors that promote accumulation of high mannose-type glycosides (deoxymannojirimycin and swainsonine). In addition, kifunensine-treated cells form more effector:target conjugates. Monoclonal antibodies to the adhesion molecule LFA-1 and its ligand ICAM-1 reduce lysis of control targets but are less effective in blocking lysis of kifunensine-treated cells. K-562 cells bind anti-ICAM-1 but not anti-LFA-1, and this binding does not change after kifunensine treatment. These data demonstrate conclusively a role for asparagine-linked oligosaccharides in the human natural killer cell:target interaction. The presence of high mannose-type glycans on K-562 cells correlates with increased binding of effectors and a greater susceptibility to lysis. These results support the idea that target cell N-glycosides influence the NK-target interaction mediated by adhesion molecules such as ICAM-1.

Topics: 1-Deoxynojirimycin; Alkaloids; Antibodies, Monoclonal; Carbohydrate Conformation; Carbohydrate Sequence; Cell Adhesion Molecules; Concanavalin A; Cytotoxicity, Immunologic; Glycoproteins; Glycoside Hydrolases; Golgi Apparatus; Humans; Indolizines; Intercellular Adhesion Molecule-1; Killer Cells, Natural; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Lymphocyte Function-Associated Antigen-1; Mannosidases; Molecular Sequence Data; Oligosaccharides; Swainsonine; Tumor Cells, Cultured

The role of N-glycosylation in the function and biosynthesis of the vasopressin V2-receptor in LLC-PK1 renal epithelial cells was examined using various lectins and inhibitors operating at different steps of the glycosidic pathway. Tunicamycin, which blocks all N-glycosylation, and castanospermine, which inhibits glycosidase I and hence blocks formation of high-mannose-type N-glycosylated intermediates, resembled one another in affecting V2-receptor biosynthesis and internalization in a concentration-dependent manner. In contrast, swainsonine, an inhibitor of mannosidase II and hence of complex-type oligosaccharide formation, had no effect. Interestingly, the alpha-D-mannose/alpha-D-glucose-specific lectin concanavalin A, (Con A), in contrast to the beta-D-galactose-specific lectin ricin, had a marked effect on the V2-receptor in LLC-PK1 cells, increasing both receptor numbers up to twofold in vivo and specific [3H]AVP binding up to 50% in vitro in a concentration-dependent manner. The concentrations inducing half-maximal response were about 0.2 and 20 micrograms/ml for the in vivo and in vitro responses, respectively, implying distinct effects on V2-expression and ligand binding. That the in vitro effect on binding was due to a direct effect on the V2-receptor could be shown by the lack of a Con A effect on [3H]AVP binding in membranes prepared from LLC-PK1 cells down-regulated for the V2-receptor or from cells of the LLC-PK1 V2-receptor deficient mutant M18. All results were consistent with a functional role for N-glycosylation of the V2-receptor in LLC-PK1 cells.

Topics: Adenylyl Cyclases; Animals; Arginine Vasopressin; Cell Line; Cell Membrane; Concanavalin A; Epithelium; Glycosylation; Indolizines; Kidney; Receptors, Angiotensin; Receptors, Vasopressin; Ricin; Swine; Tunicamycin

The T cell receptor (TCR) is a disulfide-linked heterodimer consisting of both complex and high-mannose types of N-linked oligosaccharides. The objective of the present investigation was to examine the effect of altered oligosaccharide structure on the expression and function of the TCR. Human mononuclear lymphocytes (MNL) were treated with castanospermine (CAST) or swainsonine (SW), inhibitors of glucosidase I or mannosidase II, respectively. Treatment with these inhibitors does not prevent glycosylation, but results in synthesis of glycoproteins with high-mannose or hybrid types of oligosaccharides. Treatment of MNL with CAST (1000-10 microM) or SW (100-1 microM) for up to 72 hr had no effect on cell surface expression of of the TCR. SW potentiated Con A-induced T cell proliferation without effecting anti-CD3 (OKT3) or alloantigen-induced proliferation. CAST had no effect on Con A, anti-CD3, or alloantigen-induced T cell proliferation. The T cell proliferative response to Con A in the presence of SW was completely eliminated in the presence of monoclonal anti-TCR antibodies. Monoclonal anti-CD2, -CD3, -CD4, -CD8, or isotypic control monoclonal antibodies had no effect on SW enhancement of T cell proliferation. SW treatment potentiated Con A-induced MNL expression of both the alpha and beta subunits of the IL 2R. This effect was also specifically blocked by anti-TCR monoclonal antibodies. These results demonstrate that selective changes in the glycosylation state of the TCR complex can alter mitogen recognition and subsequent cellular activation.

Topics: Alkaloids; Antigens, Differentiation, T-Lymphocyte; CD3 Complex; Concanavalin A; Drug Synergism; Glycosylation; Humans; In Vitro Techniques; Indolizines; Lymphocyte Activation; Mannosidases; Membrane Glycoproteins; Molecular Weight; Protein Processing, Post-Translational; Receptors, Antigen, T-Cell; Receptors, Interleukin-2; Swainsonine; T-Lymphocytes

Most of the cell-surface molecules involved in T-cell immune responses are N-linked glycoproteins. We have investigated the effects of inhibitors of glycoprotein processing on specific T-cell functions, with the dual aims of examining the functional role of carbohydrate and of testing the usefulness of such compounds as immunomodulators. Treatment of a cloned murine helper T-cell line with these inhibitors differentially affects the proliferative response of the cell, depending upon the nature of the stimulus. Treatment with the plant alkaloid swainsonine, which inhibits the processing mannosidase II and causes the accumulation of glycoproteins bearing hybrid-type oligosaccharide structures, enhances the proliferative response of the T-cell clone to antigen and to the mitogen concanavalin A. Treatment with another plant alkaloid, castanospermine, which inhibits glucosidase I and causes the accumulation of glucose-containing high-mannose structures, has the opposite effect and inhibits the proliferative response of the T cell to antigen. Cell-surface oligosaccharide alteration does not affect antigen recognition, as judged by the lack of effect of either drug on interleukin 2 production following antigen stimulation. Cells treated with either alkaloid proliferate poorly to exogenous interleukin 2 and may have defective interleukin 2 receptor function. Swainsonine-treated cells apparently have compensatory alterations that can overcome the reduced responsiveness to interleukin 2. Antibody-binding studies indicate that normal quantities of many cell-surface molecules, including the T-cell receptor for antigen, are expressed by the treated cells.

Topics: Alkaloids; Animals; beta-Glucosidase; Clone Cells; Concanavalin A; Dose-Response Relationship, Immunologic; Glycoproteins; Indolizines; Interleukin-2; Lymphocyte Activation; Mannosidases; Protein Processing, Post-Translational; Swainsonine; T-Lymphocytes

The effect of oligosaccharide processing inhibitors on the fusion of L6 myoblasts was studied. The glucosidase inhibitors, castanospermine, 1-deoxynojirimycin and N-methyl-deoxynojirimycin were potent inhibitors of myoblast fusion, as was the mannosidase II inhibitor, swainsonine. Inhibition of fusion was reversed when inhibitors were removed. However, the mannosidase I inhibitor, 1-deoxymannojirimycin did not inhibit fusion. Changes in cell membrane oligosaccharide structure were followed by monitoring the binding of concanavalin A (conA) and wheat germ agglutinin (WGA) to cell surface membranes in cells treated with processing inhibitors. All the processing inhibitors resulted in increased binding of conA and decreased binding of WGA; this is consistent with the known mechanisms of inhibition of the inhibitors used in the study. Inhibition of fusion by the processing inhibitors also resulted in reduced activities of creatine phosphokinase, an enzyme used as a marker for biochemical differentiation during fusion. Treatment of a non-differentiating conA-resistant cell line with processing inhibitors did not induce fusion, but the cells did show altered lectin-binding properties. The main conclusion drawn from these studies is that cell surface glycoproteins probably containing the mannose (Man)9 structure are important for the fusion reaction.

Topics: 1-Deoxynojirimycin; Alkaloids; Cell Fusion; Cell Line; Concanavalin A; Glucosamine; Glycoproteins; Indolizines; Mannose; Muscles; Oligosaccharides; Swainsonine; Wheat Germ Agglutinins

The effect of castanospermine on the processing of N-linked oligosaccharides was examined in the parent mouse lymphoma cell line and in a mutant cell line that lacks glucosidase II. When the parent cell line was grown in the presence of castanospermine at 100 micrograms/ml, glucose-containing high-mannose oligosaccharides were obtained that were not found in the absence of inhibitor. These oligosaccharides bound tightly to concanavalin A-Sepharose and were eluted in the same position as oligosaccharides from the mutant cells grown in the absence or presence of the alkaloid. The castanospermine-induced oligosaccharides were characterized by gel filtration on Bio-Gel P-4, by h.p.l.c. analysis, by enzymic digestions and by methylation analysis of [3H]mannose-labelled and [3H]galactose-labelled oligosaccharides. The major oligosaccharide released by endoglucosaminidase H in either parent or mutant cells grown in castanospermine was a Glc3Man7GlcNAc, with smaller amounts of Glc3Man8GlcNAc and Glc3Man9GlcNAc. On the other hand, in the absence of castanospermine the mutant produces mostly Glc2Man7GlcNAc. In addition to the above oligosaccharides, castanospermine stimulated the formation of an endoglucosaminidase H-resistant oligosaccharide in both cell lines. This oligosaccharide was characterized as a Glc2Man5GlcNAc2 (i.e., Glc(1,2)Glc(1,3)Man(1,2)Man(1,2)Man(1,3)[Man(1,6)]Man-GlcNAc-GlcNAc). Castanospermine was tested directly on glucosidase I and glucosidase II in lymphoma cell extracts by using [Glc-3H]Glc3Man9GlcNAc and [Glc-3H]Glc2Man9GlcNAc as substrates. Castanospermine was a potent inhibitor of both activities, but glucosidase I appeared to be more sensitive to inhibition.

Topics: Acetylglucosaminidase; Alkaloids; Animals; Cell Line; Chromatography, Gel; Chromatography, High Pressure Liquid; Concanavalin A; Glucosidases; Glycoproteins; Indolizines; Lymphoma; Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; Methylation; Mice; Oligosaccharides