Effect of 2-deoxy-D-glucose and glucosamine on the growth and functions of respiratory syncytial and parainfluenza 3 viruses

Metabolic Modifications by Common Respiratory Viruses and Their Potential as New Antiviral Targets

Respiratory viruses are known to be the most frequent causative mediators of lung infections in humans, bearing significant impact on the host cell signaling machinery due to their host-dependency for efficient replication. Certain cellular functions are actively induced by respiratory viruses for their own benefit. This includes metabolic pathways such as glycolysis, fatty acid synthesis (FAS) and the tricarboxylic acid (TCA) cycle, among others, which are modified during viral infections. Here, we summarize the current knowledge of metabolic pathway modifications mediated by the acute respiratory viruses respiratory syncytial virus (RSV), rhinovirus (RV), influenza virus (IV), parainfluenza virus (PIV), coronavirus (CoV) and adenovirus (AdV), and highlight potential targets and compounds for therapeutic approaches.

Glycolytic requirement for NK cell cytotoxicity and cytomegalovirus control

NK cell activation has been shown to be metabolically regulated in vitro; however, the role of metabolism during in vivo NK cell responses to infection is unknown. We examined the role of glycolysis in NK cell function during murine cytomegalovirus (MCMV) infection and the ability of IL-15 to prime NK cells during CMV infection. The glucose metabolism inhibitor 2-deoxy-ᴅ-glucose (2DG) impaired both mouse and human NK cell cytotoxicity following priming in vitro. Similarly, MCMV-infected mice treated with 2DG had impaired clearance of NK-specific targets in vivo, which was associated with higher viral burden and susceptibility to infection on the C57BL/6 background. IL-15 priming is known to alter NK cell metabolism and metabolic requirements for activation. Treatment with the IL-15 superagonist ALT-803 rescued mice from otherwise lethal infection in an NK-dependent manner. Consistent with this, treatment of a patient with ALT-803 for recurrent CMV reactivation after hematopoietic cell transplant was associated with clearance of viremia. These studies demonstrate that NK cell-mediated control of viral infection requires glucose metabolism and that IL-15 treatment in vivo can reduce this requirement and may be effective as an antiviral therapy.

Beta interferon regulation of glucose metabolism is PI3K/Akt dependent and important for antiviral activity against coxsackievirus B3

An effective type I interferon (IFN)-mediated immune response requires the rapid expression of antiviral proteins that are necessary to inhibit viral replication and virus spread. We provide evidence that IFN-β regulates metabolic events important for the induction of a rapid antiviral response: IFN-β decreases the phosphorylation of AMP-activated protein kinase (AMPK), coincident with an increase in intracellular ATP. Our studies reveal a biphasic IFN-β-inducible uptake of glucose by cells, mediated by phosphatidylinositol 3-kinase (PI3K)/Akt, and IFN-β-inducible regulation of GLUT4 translocation to the cell surface. Additionally, we provide evidence that IFN-β-regulated glycolytic metabolism is important for the acute induction of an antiviral response during infection with coxsackievirus B3 (CVB3). Last, we demonstrate that the antidiabetic drug metformin enhances the antiviral potency of IFN-β against CVB3 both in vitro and in vivo. Taken together, these findings highlight an important role for IFN-β in modulating glucose metabolism during a virus infection and suggest that the use of metformin in combination with IFN-β during acute virus infection may result in enhanced antiviral responses.

IMPORTANCE

Type I interferons (IFN) are critical effectors of an antiviral response. These studies describe for the first time a role for IFN-β in regulating metabolism--glucose uptake and ATP production--to meet the energy requirements of a robust cellular antiviral response. Our data suggest that IFN-β regulates glucose metabolism mediated by signaling effectors similarly to activation by insulin. Interference with IFN-β-inducible glucose metabolism diminishes the antiviral response, whereas treatment with metformin, a drug that increases insulin sensitivity, enhances the antiviral potency of IFN-β.

The effects of 2-deoxyglucose and tunicamycin on the biosynthesis of the murine mammary tumor virus proteins, and on the assembly and release of the virus

The role of glycosylation in the biosynthesis, processing, and shedding of the murine mammary tumor virus (MuMTV) glycoproteins and in virus production was investigated in a clonal mammary tumor cell line, GR-3A, using two inhibitors of protein glycosylation, 2-deoxyglucose (2-DG) and tunicamycin (TM). It was found that both 2-DG and TM completely inhibited the synthesis of the MuMTV envelope precursor polyprotein, Pr70env, and, as a consequence, the synthesis of the viral glycoproteins gp52 and gp36. By contrast, the synthesis of Pr73gag, the polyprotein precursor of the internal structural proteins of the virus, was only inhibited by 10-15% by 2-DG and TM. Although 2-DG and TM blocked the synthesis of Pr70env, a new polypeptide, related to gp52 and gp36, with a mol wt of 60,000 (P60env) was found to be synthesized in the treated cells. The P60env molecules appeared to be degraded intracellularly since they were not found to (1) undergo site-specific cleavage; (2) accumulate inside the cell or on the cell surface; (3) be secreted into the culture medium; and (4) be incorporated into the virions produced during the drug treatment. In spite of the lack of gp52 and gp36 synthesis in the presence of TM and 2-DG, mature MuMTV particles containing the characteristic surface projections known to be composed of gp52 and gp36 continued to be assembled and released at a reduced rate for at least 30 hr. In addition, the buoyant density and the polypeptide composition of the particles were found to be identical to virions produced by untreated cells. Thus, the virions assembled and released during 2-DG and TM treatment were not defective. Our investigations into the origin of gp52 and gp36 in these particles revealed that both molecules were synthesized prior to 2-DG and TM treatment and continued to be incorporated, along with the newly synthesized viral core proteins, into budding virions during the drug treatment. Furthermore, we found that gp52 and P75env (an aberrant form of Pr70env) that were not incorporated into virions continued to be shed normally from the cell during drug treatment. In conclusion, our results suggest that MuMTV assembly is not dependent on the synchronized synthesis of the viral core and envelope polypeptides, and that the assembled virions contain the correct ratio of these polypeptides, even when their ratio in the cell varies.

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.

In vivo antiviral activity of D-glucosamine

Intraperitoneal treatments with D-glucosamine, an inhibitor of the glycosylation of the viral envelope, decreased the growth rate of tumors induced in quails or in chicks by Rous sarcoma virus and increased the survival of mice inoculated with human influenza virus.