Effect of 2-deoxy-D-glucose on the multiplication of Semliki Forest virus and the reversal of the block by mannose

Effects of 2-deoxy-D-glucose and 3 deazauridine individually and in combination on the replication of Japanese B encephalitis virus

We have tested the potencies of the competitors of glucose, 2-deoxy-d-glucose, and of uridine, 3-deazauridine, on the inhibition of Japanese B encephalitis virus multiplication in BHK-21 cell cultures. The relative effectiveness of the viral inhibitors were evaluated individually and in combination in relation to cytotoxicity as a measure of the selectivity of inhibition. When the drugs were administered individually, the antiviral activity was masked by the cytotoxic effect on the host. By combining the two drugs, it was possible to inhibit Japanese encephalitis virus production at noncytotoxic concentrations. The effects of 2-deoxy-d-glucose and 3-deazauridine on the growth inhibition of BHK-21 cells in cultures were only additive, while they were clearly synergistic on the inhibition of Japanese encephalitis virus production. Thus, it was possible to achieve an increased antiviral effect without a significant increase in cytotoxicity. Although the precise biochemical mechanism of the antiviral activity of these antimetabolites in combination is not known, our results indicate the potential value of this approach in viral chemotherapy.

Properties of a baby-hamster-kidney cell line with increased resistance of 2-deoxy-D-glucose

A cultured cell line with increased resistance to 2-deoxy-D-glucose was obtained from cloned baby hamster kidney fibroblasts, BHK 21/C13, after repeated exposure to high concentrations of 2-deoxyglucose. The increased resistance could not be attributed to a decreased permeability of deoxysugar. The resistant cell line incorporated radioactive 2-deoxy-Dglucose in glycoproteins at a similar rate as parental BHK 21C13 cells. Incorporation of radioactive glucosamine, galactose and to lesser extent mannose into cellular glycoproteins was inhibited by 2-deoxyglucose to similar extents in the resistant cells and parental BHK 21/C13 cells. Changes induct cells were detected by altered to toxic plant lectins and by surface labelling as described for parental cells in the preceding paper. It is suggested that the toxicity of 2-deoxy-D-glucose to normal fibroblasts is not mediated through effects on glycosylation of cellular glycoproteins.

Effect of 2-deoxy-D-glucose on the cell-surface glycoproteins of hamster fibroblasts,

1. Growth of baby hamster kidney (BHK) cells in medium containing 2-deoxy-D-glucose is retarded in direct proportion of the 2-deoxyglucose concentration. The severity of the effect is reduced in medium containing high relative concentrations of glucose. 2. 2-Deoxyglucose inhibits the incorporation of radioactivity from mannose, galactose, glucosamine, fucose and N-acetylmannosamine precursors into acid-insoluble cellular material. Incorporation of radioactively labelled leucine into protein is not affected by 2-deoxyglucose. 3. BHK cells grown in the presence of 2-deoxyglucose become less sensitive to the toxic action of certain plant lectins, ricin of Ricinus communis and Phaseolus vulgaris phytohaemagglutinin, which bind specifically to cell surface galactose and N-acetyl-galactosamine residues. By contrast, 2-deoxyglucose increased the sensitivity of BHK cells to the weak toxicity of concanavalin A, which binds to surface mannosides. Treated cells also become more agglutinable with concanavalin A. 4. Cell surface glycoprotein labelled by lactoperoxidase-catalysed iodination have been examined by dodecylsulphate-polyacrylamide gel electrophoresis. The radio-iodinated glycoprotein prepared from cells grown in medium containing 2-deoxyglucose migrate more rapidly than glycoproteins from cells grown in the absence of inhibitor.

2-Deoxyglucose selectively inhibits Fc and complement receptor-mediated phagocytosis in mouse peritoneal macrophages II. Dissociation of the inhibitory effects of 2-deoxyglucose on phagocytosis and ATP generation

Macrophages incubated in 2-deoxy-D-glucose (2-dG)-containing medium showed a marked decrease in cellular ATP content, and were unable to ingest IgG- and complement-coated erythrocytes via the corresponding membrane receptors for these ligands. However, the inhibitory effects of 2-dG on Fc- and C3 receptor-mediated phagocytosis were not a consequence of lowered macrophage ATP levels since addition of glucose or mannose to the culture medium restored the capacity of the macrophages to ingest IgG- and C3-coated particles without increasing ATP levels. These results indicate that Fc- and C3 receptor-mediated phagocytosis (opsonin dependent) differs qualitatively from the ingestion of latex and zymosan particles (opsonin independent); they suggest that the same regulatory molecules govern the responses of phagocytic cells to signals initiated by both the Fc and C3 receptors. The possibility that these molecules are regulated by glycosylation is discussed.

Interference of nucleoside diphosphate derivatives of 2-deoxy-D-glucose with the glycosylation of virus-specific glycoproteins in vivo

The predominant effect of 2-deoxy-D-glucose on chick embryo cells infected with Semliki Forest virus is an interference with glycosylation of virus-specific glycoproteins; this results in a block of synthesis of infectious virus. Incorporation of radioactive mannose is blocked severely in the presence of 2-deoxyglucose in the cultural medium although it is readily phosphorylated and subsequently activated by GTP to yield GDP-mannose, which accumulates under these conditions. The intracellular concentrations of GDP-mannose and UDP-N-acetyl-D-hexosamine are not reduced in the presence of the inhibitor. An equimolar concentration of mannose in the cultural medium competes with the inhibitory effect of the deoxysugar and drops the cellular pool of GDP-2-deoxy-D-glucose below the level of detection, at the same time restoring the synthesis of infectious virus. When the intracellular concentration of UDP-2-deoxyglucose is reduced by addition of glucose into the cultural medium the inhibition of virus synthesis by the deoxysugar and the concentration of GDP-2-deoxyglucose within the cells remain near to the values when the inhibitor is present alone. It is concluded that among the metabolites of 2-deoxyglucose which occur in vivo after addition of 2-deoxyglucose to the culture medium, GDP-2-deoxyglucose is the agent responsible for inhibition of glycosylation of viral glycoproteins.

Changes in the surface of virus-infected cells recognized by cytotoxic T cells. II. A requirement for glycoprotein synthesis in virus-infected target cells

Infection of cells with either ectromelia or lymphocytic choriomeningitis (LCM) virus in the presence of 2-deoxy-D-glucose (2-DOG) inhibited by up to 70% the extent to which the infected cells become susceptible to virus-specific cell-mediated lysis. The concentration of 2-DOG used had little effect on the extent of total protein synthesis (incorporation of [35S] methionine) but inhibited (up to 25%) glycoprotein synthesis, as measured by incorporation of [3H] fucose. This suggested that glycoprotein synthesis was a necessary event for infected cells to become susceptible to T-cell mediated lysis. The profiles (polyacrylamide gel electrophoresis) of newly synthesized, cellular glycoproteins from unifected and ectromelia-infected cells in the presence and absence of 2-DOG were compared and found to be very complex, with only minor changes. However, when convalescent serum from infected mice was used to isolate newly synthesized components from the cell surface shortly after infection, it showed four main species ranging in size from 25,000 to 70,000 daltons. 2-DOG inhibited production of these by 70%, thus corresponding to the biological data. The nature of the new glycoproteins seen in infected cells and whether they are in fact the structures recognized by effector T cells remain to be determined.

Formation of dolichol monophosphate 2-deoxy-D-glucose and its interference with the glycosylation of mannoproteins in yeast

A crude membrane fraction from Saccharomyces cerevisiae has been found to catalyze 2-deoxy-D-glucose transfer from GDP-2-deoxy-D-glucose to endogeneous lipid and glycoprotein acceptor. Evidence will be represented that the glycolipid formed has properties characteristic dolichol monophosphate 2-deoxy-D-glucose. The 2-deoxy-D-glucosyl group can further be transferred from the glycolipid into a membrane-bound polymer fraction. More than 95% of the radioactivity incorporated can be released by beta-elimination, indicating an O-glycosidic linkage to serine or threonine. The only radioactive product obtained is 2-deoxy-D-glucose. When dolichol monophosphate 2-deoxy-[14C]glucose is incubated together with non-radioactive GDP-mannose subsequent beta-elimination yields no higher oligosaccharides in contrast to an experiment where dolichol monophosphate [14C]mannose and GDP-mannose are used as donors. The results are consistent with the assumption that the non-physiological nucleotide sugar interferes with GDP-mannose for mannosylation and terminates further elongation of the serine/threonine-bound oligomannose side chains. UDP-2-deoxy-D-glucose, used as donor, results also in the formation of a glycolipid. In this case, however, no polyprenol derivative is formed. Instead, the glycolipid displays properties characteristic of sphingolipid or a sterol glucoside.

Formation of uridine diphosphate 2-deoxy-D-glucose and guanosine diphosphate 2-deoxy-D-glucose in vitro using animal enzymes

The enzymic formation of guanosine diphosphate 2-deoxy-D-glucose and uridine diphosphate 2-deoxy-D-glucose from synthetically prepared 2-deoxy-D-glucose 1-phosphate is described. Incubation of 2-deoxy-D-glucose 1-phosphate with an enzyme preparation from bovine mammary glands and either GTP or UTP gives rise to the corresponding nucleoside-diphosphate derivative of 2-deoxy-D-glucose. Uridine diphosphate 2-deoxy-D-glucose could also be obtained by incubation of 2-deoxy-D-glucose 1-phosphate with UTP and UDP glucose pyrophosphorylase from beef liver.

Effect of tetraethyl thiuram disulfide (disulfiram) on the multiplication of enveloped viruses

Disulfiram at concentrations between 0.1 and 0.3 mM inhibits the multiplication of Semliki Forest virus (SFV), fowl plague virus (FPV), Newcastle disease virus (NDV), vesicular stomatitis virus (VSV), and pseudorabies virus (PRV), when administered 1 hour before and during adsorption. There is, however, no inhibition of virus multiplication, when the drug is added after adsorption onto chick embryo cells. Disulfiram interferes neither with the receptors of the virus nor of erythrocytes, and it does not prevent virus adsorption. Possibly an early step in virus multiplication is affected by disculfiram. Infected cells once treated with the drug recover after some time of incubation in an ingibitor-free medium. The inhibitory state can be maintained, however, if relatively low doses of disulfiram are present in the culture medium also after adsorption. Disulfiram has no effect on macromolecular synthesis of the host cells. It has, however, a marked affect on membrane function. While virus multiplication is readily inhibited by disulfiram when chick embryo or BHK cells were investigated, virus multiplication in HeLa cells is almost resestant against the action of disulfiram.

Effect of impaired glycosylation on the biosynthesis of Semliki forest virus glycoproteins

The glycoproteins of Semliki Forest virus, grown in chicken embryo cells, were labeled with radioactive sugars. The data indicate a high mannose content of the nonstructural precursor glycoprotein NSP 63. This protein can also be readily labeled with 2-deoxy-D-glucose. The envelope glycoproteins E1 and E2 are relatively rich in galactose, glucosamine, and fucose. Glycosylation can be impaired by 2-deoxy-D-glucose or D-glucosamine or by omission of sugars in the culture medium. Under these conditions characteristic changes in the electrophoretic profile of the viral polypeptides are observed: in the regions of glycoproteins NSP 97, NSP 63, and E1 and E2 new protein peaks can be detected. These polypeptides seem to be aberrant forms of the glycoproteins. When compared with the normal molecules they have lower molecular weights and contain less carbohydrates, especially mannose. Pulse-chase experiments indicate that the altered glycoproteins are degraded very slowly if at all. If, however, impairment is caused by omission of sugars in the culture medium, the radioactivity is chased after addition of glucose from the region between NSP 63 and E1 + E2 into the E1 + E2 peak. This suggests a completion of the carbohydrate chains under these conditions.

Proteins synthesized by Semliki Forest virus and its 16 temperature-sensitive mutants

The proteins synthesized in chicken embryo fibroblasts infected with wild-type Semliki Forest virus and 16 temperature-sensitive mutants derived from it were studied by polyacrylamide gel electrophoresis. In addition to the structural proteins, five nonvirion proteins (NVP) with molecular weight of 130,000, 97,000, 86,000, 78,000 and 62,000 were found varying amounts in cells infected with the different RNA+ mutants and also in the wild-type-infected cells. Pulse-chase experiments suggested that NVP 130, NVP 97, NVP 86, and NVP 62 are precursors presumably of the structural proteins. The amount of NVP 78 was not affected by the chase, and it may represent a translational product of the nonstructural part of the genome. The NVP 130 was shown to be a common precursor of the structural proteins by tryptic peptide mapping. Kinetic evidence from one of the mutants (ts-3) suggested that NVP 86 is one of the precursors of the capsid protein. A common feature of all the RNA+mutants was the inability to cleave the NVP 62 into E2 and E3, suggesting that this cleavage is a crucial reaction in the virus maturation.

Inhibition of glycosylation of the influenza virus hemagglutinin

d-Glucosamine and 2-deoxy-d-glucose interfere with the biosynthesis of the hemagglutinin glycoproteins. With increasing inhibitor concentrations a progressive decrease in size of the precursor HA and the cleavage products, HA(1) and HA(2) can be observed. The shift in molecular weight is paralleled by a decrease of the carbohydrate content. This was shown by labeling studies with radioactive sugars which revealed that the inhibitors block the incorporation into glycoproteins, whereas they have no or only slight effects on the uptake and activation of sugars. Under conditions of maximal inhibition, the hemagglutinin proteins lack all or most of their carbohydrates. These findings indicate that the inhibitory effect of d-glucosamine and 2-deoxy-d-glucose is due to an impairment of glycosylation. When glycosylation is inhibited, the precursor polypeptide is synthesized at normal rates. Its cleavage products, however, are very heterogeneous. This suggests that carbohydrate protects the hemagglutinin from proteolytic degradation.

Inhibition of the multiplication of vesicular stomatitis and Newcastle disease virus by 2-deoxy-d-glucose

The production of infectious vesicular stomatitis (VSV) and Newcastle disease virus can be completely inhibited by 2-deoxy-d-glucose in pyruvate-containing medium, if virus either grown in pyruvate-containing medium or dialyzed against phosphate-buffered saline is used for infection. Under these conditions, the synthesis of all VSV proteins is reduced. VSV RNA, which is synthesized at reduced rates, seems to be unstable. The effect is completely reversible. If virus grown in glucose-containing medium is used for infection, the production of both viruses is not significantly inhibited by 2-deoxy-d-glucose. Under these conditions the production of the VSV glycoprotein is specifically impaired, but does not lead to a marked reduction of the yield of infectious virus.