Modification of macrophage glyceraldehyde-3-phosphate dehydrogenase in response to nitric oxide

Critical protein GAPDH and its regulatory mechanisms in cancer cells

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), initially identified as a glycolytic enzyme and considered as a housekeeping gene, is widely used as an internal control in experiments on proteins, mRNA, and DNA. However, emerging evidence indicates that GAPDH is implicated in diverse functions independent of its role in energy metabolism; the expression status of GAPDH is also deregulated in various cancer cells. One of the most common effects of GAPDH is its inconsistent role in the determination of cancer cell fate. Furthermore, studies have described GAPDH as a regulator of cell death; other studies have suggested that GAPDH participates in tumor progression and serves as a new therapeutic target. However, related regulatory mechanisms of its numerous cellular functions and deregulated expression levels remain unclear. GAPDH is tightly regulated at transcriptional and posttranscriptional levels, which are involved in the regulation of diverse GAPDH functions. Several cancer-related factors, such as insulin, hypoxia inducible factor-1 (HIF-1), p53, nitric oxide (NO), and acetylated histone, not only modulate GAPDH gene expression but also affect protein functions via common pathways. Moreover, posttranslational modifications (PTMs) occurring in GAPDH in cancer cells result in new activities unrelated to the original glycolytic function of GAPDH. In this review, recent findings related to GAPDH transcriptional regulation and PTMs are summarized. Mechanisms and pathways involved in GAPDH regulation and its different roles in cancer cells are also described.

Multiple targets of nitric oxide in the tricarboxylic acid cycle of Salmonella enterica serovar typhimurium

Host nitric oxide (NO⋅) production is important for controlling intracellular bacterial pathogens, including Salmonella enterica serovar Typhimurium, but the underlying mechanisms are incompletely understood. S. Typhmurium 14028s is prototrophic for all amino acids but cannot synthesize methionine (M) or lysine (K) during nitrosative stress. Here, we show that NO⋅-induced MK auxotrophy results from reduced succinyl-CoA availability as a consequence of NO⋅ targeting of lipoamide-dependent lipoamide dehydrogenase (LpdA) activity. LpdA is an essential component of the pyruvate and α-ketoglutarate dehydrogenase complexes. Additional effects of NO⋅ on gene regulation prevent compensatory pathways of succinyl-CoA production. Microarray analysis indicates that over 50% of the transcriptional response of S. Typhimurium to nitrosative stress is attributable to LpdA inhibition. Bacterial methionine transport is essential for virulence in NO⋅-producing mice, demonstrating that NO⋅-induced MK auxotrophy occurs in vivo. These observations underscore the importance of metabolic targets for antimicrobial actions of NO⋅.

Nitric oxide signaling and nitrosative stress in neurons: role for S-nitrosylation

Nitric oxide (NO) mediates cellular signaling pathways that regulate a plethora of physiological processes. One of the signaling mechanisms mediated by NO is through S-nitrosylation of cysteine residues in target proteins, which is now regarded as an important redox-based physiological action. Deregulation of the protein S-nitrosylation upon nitrosative stress, however, has also been linked to various human diseases, such as neurodegenerative disorders. Between these physiological and pathophysiological roles, there are mechanisms whereby a milder level of nitrosative stress provides S-nitrosylation of some proteins that counteracts the pathological processes, serving as a negative feedback mechanism. In addition, NO has recently emerged as a mediator of epigenetic gene expression and chromatin changes. In this review, these molecular mechanisms, especially those in the central nervous system and neurodegenerative disorders, are described.

Spinal cord glia and interleukin-1 do not appear to mediate persistent allodynia induced by intramuscular acidic saline in rats

Spinal glial activation and consequent interleukin-1 (IL-1) release are implicated in pain facilitation induced by inflammation/damage to skin and peripheral nerves. It is unclear whether pain facilitation induced at deep tissue sites also depends on these. We investigated whether spinal IL-1 and/or glial activation mediates bilateral allodynia induced by repeated unilateral intramuscular injections of acidic saline to rats. Given the prominent role of spinal IL-1 in various bilateral pain models, we predicted that intrathecal IL-1 receptor antagonist (IL-1ra) would suppress bilateral allodynia in this model as well. Surprisingly, neither single nor repeated intrathecal injections of IL-1ra affected allodynia, measured by the von Frey test, induced by prior intramuscular acidic saline compared with vehicle-injected controls. In addition, we tested the effect of 2 additional intrathecal manipulations that are broadly efficacious in suppressing glially mediated pain facilitation: (1) a glial metabolic inhibitor (fluorocitrate) and (2) the anti-inflammatory cytokine, interleukin-10 (IL-10). Like IL-1ra, fluorocitrate and IL-10 each failed to reverse allodynia. Finally, we observed no significant activation of glial cells, as assessed by immunohistochemistry of glial activation markers, in the lumbar spinal cord in response to intramuscular acidic saline. Taken together, the present data suggest that acidic saline-induced bilateral allodynia is created independently of glial activation.

PERSPECTIVE

From converging lines of evidence, the current studies suggest that persistent bilateral allodynia induced by repeated intramuscular acidic saline is not mediated by spinal IL-1 and/or spinal glial activation. As such, this might represent the first evidence for pain facilitation occurring in the absence of glial involvement.

Nitrosylcobalamin promotes cell death via S nitrosylation of Apo2L/TRAIL receptor DR4

We have previously demonstrated that nitrosylcobalamin (NO-Cbl), an analogue of vitamin B12 that delivers nitric oxide (NO), had potent antiproliferative activity against several human cancer cell lines. NO-Cbl induced apoptosis via a death receptor/caspase-8 pathway. In this study, we demonstrate that a functional Apo2L/TRAIL receptor was necessary for the induction of cell death by NO-Cbl. Furthermore, the Apo2L/TRAIL death receptor DR4 (TRAIL R1) was S nitrosylated following NO-Cbl treatment. Human melanoma (A375), renal carcinoma (ACHN), and ovarian carcinoma (NIH-OVCAR-3) cells were treated with NO-Cbl and subjected to the biotin switch assay; S-nitrosylated DR4 was detected in all three cell lines. NO-Cbl treatment did not cause S nitrosylation of DR5. The seven cysteine residues located in the cytoplasmic domain of DR4 were individually point mutated to alanines. NIH-OVCAR-3 cells expressing the DR4 C336A mutation lacked S nitrosylation following NO-Cbl treatment. Overexpression of wild-type DR4 sensitized cells to growth inhibition by NO-Cbl. Cells expressing the DR4 C336A mutant were more resistant to NO-Cbl and Apo2L/TRAIL than were the other six C-A mutations or wild-type cells. The C336A mutant also displayed blunted caspase-8 enzymatic activity following NO-Cbl treatment compared to the other mutants. Thus, DR4 residue C336 becomes S nitrosylated and promotes apoptosis following NO-Cbl treatment.

GAPDH as a sensor of NO stress

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a classic glycolytic enzyme, and accumulating evidence has suggested that GAPDH is a multi-functional protein. In particular, its role as a mediator for cell death has been highlighted. For the last decade, many groups reported that a pool of GAPDH translocates to the nucleus under a variety of stressors, most of which are associated with oxidative stress. At the molecular level, sequential steps lead to nuclear translocation of GAPDH during cell death as follows: first, a catalytic cysteine in GAPDH (C150 in rat GAPDH) is S-nitrosylated by nitric oxide (NO) that is generated from inducible nitric oxide synthase (iNOS) and/or neuronal NOS (nNOS); second, the modified GAPDH becomes capable of binding with Siah1, an E3 ubiquitin ligase, and stabilizes it; third, the GAPDH-Siah protein complex translocates to the nucleus, dependent on Siah1's nuclear localization signal, and degrades Siah1's substrates in the nucleus, which results in cytotoxicity. A recent report suggests that GAPDH may be genetically associated with late-onset of Alzheimer's disease. (-)-deprenyl, which has originally been used as a monoamine oxidase inhibitor for Parkinson's disease, binds to GAPDH and displays neuroprotective actions, but its molecular mechanism is still unclear. The NO/GAPDH/Siah1 death cascade will contribute to the molecular understanding of a role of GAPDH in neurodegenerative disorders and help to establish novel therapeutic strategies.

Regulation of the apoptosis-necrosis switch

Execution of the apoptotic program involves a relatively limited number of pathways. According to a general view, these would converge to activate the caspase family of proteases. However, there is increasing evidence that apoptotic-like features can also be found when caspases are inhibited. Moreover, under pathological conditions, apoptosis and nonapoptotic death paradigms are often interwined, which suggest that, in vivo, cells may use diverging execution pathways. Molecular switches between apoptosis and necrosis include adenosine triphosphate-dependent steps in the activation of caspases or steps sensitive to reactive oxygen/nitrogen species. In turn, caspase activation can cause necrosis by promoting ion overload.

Thioredoxin, a regulator of gene expression

Cancer cells have high levels of thioredoxin (Trx) and of glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Cells from patients with the cancer-prone disease Fanconi anemia (FA) exhibit reduced Trx levels. We found the activity of GAPDH to correlate directly with the endogenous Trx content and mRNA transcripts for GAPDH and TRx reduced in FA cells. The treatment of cells with reduced human Trx stimulated the synthesis of GAPDH mRNA. Similarly, the transfection of cells with an expression plasmid for Trx increased GAPDH mRNA synthesis. Trx treatment of cells and subsequent analysis of the differential gene expression by human cDNA arrays containing about 50 000 different PCR products resulted in more than 300 up- or downregulated genes. Two representative genes, GAPDH and IkappaBalpha/MAD-3, were further investigated to confirm their stimulation by Trx. Trx besides being the major carrier of redox potential of cells is also a regulator of gene expression on the transcriptional level. By regulation via Trx, cells are able to adapt to the prevailing redox conditions. These findings also enlighten the pathophysiology of FA in the respect that the characteristic diminution of Trx that results in the dysregulation of gene expression is a basis for the major symptoms of this disease.

Nitric oxide inhibition of mitochondrial respiration and its role in cell death

Nitric oxide (NO) or its derivatives (reactive nitrogen species, RNS) inhibit mitochondrial respiration in two different ways: (i) an acute, potent, and reversible inhibition of cytochrome oxidase by NO in competition with oxygen; and, (ii) irreversible inhibition of multiple sites by RNS. NO inhibition of respiration may impinge on cell death in several ways. Inhibition of respiration can cause necrosis and inhibit apoptosis due to ATP depletion, if glycolysis is also inhibited or is insufficient to compensate. Inhibition of neuronal respiration can result in excitotoxic death of neurons due to induced release of glutamate and activation of NMDA-type glutamate receptors. Inhibition of respiration may cause apoptosis in some cells, while inhibiting apoptosis in other cells, by mechanisms that are not clear. However, NO can induce (and inhibit) cell death by a variety of mechanisms unrelated to respiratory inhibition.

Glyceraldehyde-3-phosphate dehydrogenase in neurodegeneration and apoptosis signaling

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a well-studied glycolytic enzyme that plays a key role in energy metabolism. GAPDH catalyzes the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate in the glycolytic pathway. As part of the conversion, GAPDH converts NAD+ to the high-energy electron carrier NADH. GAPDH has been referred to as a "housekeeping" protein and based on the view that GAPDH gene expression remains constant under changing cellular conditions, the levels of GAPDH mRNA have frequently been used to normalize northern blots. In recent years, that view has changed since GAPDH is now known to contribute to a number of diverse cellular functions unrelated to glycolysis. Normative functions of GAPDH now include nuclear RNA export, DNA replication, DNA repair, exocytotic membrane fusion, cytoskeletal organization and phosphotransferase activity. Pathologically, GAPDH has been implicated in apoptosis, neurodegenerative disease, prostate cancer and viral pathogenesis (see Sirover (1999) for a recent review of GAPDH functions). Most recently, it has been shown that GAPDH is a target for deprenyl related compounds (Carlile et al., 2000; Kragten et al., 1998) and may contribute to the neuroprotection offered by those compounds.

Glyceraldehyde-3-phosphate dehydrogenase and apoptosis

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has long been recognized as playing an integral role in glycolysis. During the past 20 years, however, a number of novel, additional functions for GAPDH have been described. These include acting as an uracil DNA glycosylase, activator of transcription, binding to RNA, and an involvement in tubulin assembly. One of the most intriguing functions which has recently been recognized is an involvement in the initiation of apoptosis. Further, GAPDH associates with proteins implicated in human neurodegenerative disorders. This review summarizes the evidence implicating GAPDH in the initiation of one or more apoptotic cascades. The possible functions of GAPDH in the nucleus which could result in the initiation of apoptosis are also discussed.

Involvement of JAK2 and MAPK on type II nitric oxide synthase expression in skin-derived dendritic cells

In this report, we demonstrate that a fetal mouse skin-derived dendritic cell line produces nitric oxide (NO) in response to the endotoxin [lipopolysaccharide (LPS)] and to cytokines [tumor necrosis factor-alpha (TNF-alpha) and granulocyte-macrophage colony-stimulating factor (GM-CSF)]. Expression of the inducible isoform of NO synthase (iNOS) was confirmed by immunofluorescence with an antibody against iNOS. The tyrosine kinase inhibitor genistein decreased LPS- and GM-CSF-induced nitrite (NO(-2)) production. The effect of LPS and cytokines on NO(-2) production was inhibited by the Janus kinase 2 (JAK2) inhibitor tyrphostin B42. The p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB-203580 also reduced the NO(-2) production evoked by LPS, TNF-alpha, or GM-CSF, but it was not as effective as tyrphostin B42. Inhibition of MAPK kinase with PD-098059 also slightly reduced the effect of TNF-alpha or GM-CSF on NO(-2) production. Immunocytochemistry studies revealed that the transcription factor nuclear factor-kappaB was translocated from the cytoplasm into the nuclei of fetal skin-derived dendritic cells (FSDC) stimulated with LPS, and this translocation was inhibited by tyrphostin B42. Our results show that JAK2 plays a major role in the induction of iNOS in FSDC.

Modification of glyceraldehyde-3-phosphate dehydrogenase in response to nitric oxide in intestinal preconditioning

BACKGROUND

Previous studies have demonstrated that intestinal preconditioning is triggered by an initial increase in nitric oxide synthesis. This confers resistance to the organ in face of a subsequently sustained period of ischemia-reperfusion. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key enzyme in the glycolytic cascade that could be modulated by nitric oxide. The purpose of the present study is to evaluate a possible inhibitory effect on intestinal GAPDH by the nitric oxide generated during preconditioning. This could lead to a reduction of lactate accumulation during subsequent ischemia.

METHODS

GAPDH activity was measured after intestinal preconditioning, and the effect of nitric oxide synthase inhibition was evaluated.

RESULTS

Preconditioning induced a significant, but transient, decrease in GAPDH activity. This effect appears to be correlated with a reduced amount of lactate accumulation during ischemia. Inhibition of nitric oxide synthesis reversed these changes. In addition, increased synthesis of nitric oxide was detected after preconditioning.

CONCLUSIONS

In summary, this study indicates that nitric oxide generated during ischemic preconditioning could act as a glycolytic modulator during subsequent ischemia, through its effect on GAPDH activity.

Inducible NO synthase: role in cellular signalling

The discovery of endothelium-derived relaxing factor and its identification as nitric oxide (NO) was one of the most exciting discoveries of biomedical research in the 1980s. Besides its potent vasodilatory effects, NO was found under certain circumstances to be responsible for the killing of microorganisms and tumour cells by activated macrophages and to act as a novel, unconventional type of neurotransmitter. In 1992, Science picked NO as the ‘Molecule of the Year’, and over the past years NO has become established as a universal intercellular messenger that acutely affects important signalling pathways and, on a more long-term scale, modulates gene expression in target cells. These actions will form the focus of the present review.

The chemistry of DNA damage from nitric oxide and peroxynitrite

Nitric oxide is a key participant in many physiological pathways; however, its reactivity gives it the potential to cause considerable damage to cells and tissues in its vicinity. Nitric oxide can react with DNA via multiple pathways. Once produced, subsequent conversion of nitric oxide to nitrous anhydride and/or peroxynitrite can lead to the nitrosative deamination of DNA bases such as guanine and cytosine. Complex oxidation chemistry can also occur causing DNA base and sugar oxidative modifications. This review describes the different mechanisms by which nitric oxide can damage DNA. First, the physiological significance of nitric oxide is discussed. Details of nitric oxide and peroxynitrite chemistry are then given. The final two sections outline the mechanisms underlying DNA damage induced by nitric oxide and peroxynitrite.

Nuclear translocation of glyceraldehyde-3-phosphate dehydrogenase isoforms during neuronal apoptosis

Treatment with cytosine beta-D-arabinoside (AraC; 300 microM) induced a time-dependent accumulation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) protein in nuclei purified from cultured cerebellar granule cells, with a concomitant degradation of lamin B1, a nuclear membrane protein and a substrate of CPP32/caspase-3. Moreover, Asp-Glu-Val-Asp-fluoromethyl ketone (DEVD-fmk), a CPP32-selective antagonist, dose-dependently suppressed AraC-induced apoptosis of these neurons. Nuclear accumulation of GAPDH protein was associated with a progressive decrease in the activity of uracil-DNA glycosylase (UDG), one of the nuclear functions of GAPDH. The nuclear dehydrogenase activity of GAPDH was initially increased after treatment and then decreased parallel to UDG activity. Six GAPDH isoforms were detected in the nuclei of AraC-treated cells. The more alkaline isoforms, 1-3, constituted the bulk of the nuclear GAPDH, and the remaining isoforms, 4-6, were the minor species. Levels of all six isoforms were increased after treatment with AraC for 16 h; a 4-h treatment increased levels of only isoforms 4 and 5. Thus, it appears that various GAPDH isoforms are differentially regulated and may have distinct apoptotic roles. Pretreatment with GAPDH antisense oligonucleotide blocked the nuclear translocation of GAPDH isoforms, and the latter process occurred concurrently with a decrease in cytosolic GAPDH isoforms. Sodium nitroprusside-induced NAD labeling of nuclear GAPDH showed a 60% loss of GAPDH labeling after AraC treatment, suggesting that the active site of GAPDH may be covalently modified, denatured, or improperly folded. The unfolded protein response elicited by denatured GAPDH may contribute to AraC-induced neuronal death.

The effect of antisense oligodeoxynucleotides on nitric oxide secretion from macrophage-like cells

Nitric oxide (NO) plays an important role in cellular signaling and host defense, and it also contributes to the deleterious effects of immune response. Until recently, the lack of specific inhibitors of various forms of nitric oxide synthase (NOS) hampered a stringent evaluation of the role played by inducible NOS (iNOS) in cell damage. The present study investigated the use of antisense oligodeoxynucleotides (AS-ODNs) to selectively inhibit the expression of iNOS. AS-ODNs (1-10 microM) inhibited, in a time-dependent and dose-dependent manner, iNOS activity in RAW 264.7 murine macrophages. Maximal inhibitory effect was >90%, and control ODNs had little or no effect on NO production. Treatment with AS-ODNs decreased iNOS protein and mRNA level in studied cell, and control ODNs again were ineffective. The decreased levels of the target mRNA in AS-ODN-treated samples suggest that the AS-ODNs used act as substrates for ribonuclease (RNase) H. Lipofection enhanced the effect of AS-ODNs on iNOS activity. However, this potentiation appears to be different from the antisense effect, in which the AS-ODNs studied were involved. Liposaccharide/interferon-gamma (LPS/IFN-gamma) induced iNOS, and increased NO production impaired the viability of macrophages. Treatment of RAW 264.7 cells with 10 microM AS-ODNs prevented the NO-induced lethal cell damage.

A mechanistic analysis of nitric oxide-induced cellular toxicity

Nitric oxide (NO.)-induced toxicity was investigated in two different cell lines, Chinese hamster ovary (CHO-AA8) and human lymphoblastoid (TK6), over a range of NO. doses (0-9 mM) delivered for an exposure of 2 h. To determine both short-term and delayed effects leading to death, a range of assays was employed to decipher the major mechanisms of cytotoxicity. Examples of damage parameters measured in this study include inhibition of DNA synthesis, damage to mitochondria, loss of cell membrane integrity, apoptosis, changes in cell cycle distribution, and the occurrence of DNA strand breaks. Our results indicate that NO.-induced toxicity is an extremely complex process involving multiple pathways generally leading to apoptotic cell death. Results consistently demonstrate that TK6 cells are much more susceptible to NO.-induced toxicity than CHO-AA8 cells. This difference in sensitivity could be seen for all types of cellular damage examined. The earliest observable effect of NO. exposure is inhibition of DNA synthesis which is not the result of inhibition of ribonucleotide reductase but may be the result of DNA damage leading ultimately to cell cycle arrest.