Glyceraldehyde-3-phospate dehydrogenase is translocated into nuclei through Golgi apparatus during apoptosis induced by 6-hydroxydopamine in human dopaminergic SH-SY5Y cells

GAPDH in neuroblastoma: Functions in metabolism and survival

Neuroblastoma is a pediatric cancer of neural crest cells. It develops most frequently in nerve cells around the adrenal gland, although other locations are possible. Neuroblastomas rely on glycolysis as a source of energy and metabolites, and the enzymes that catalyze glycolysis are potential therapeutic targets for neuroblastoma. Furthermore, glycolysis provides a protective function against DNA damage, and there is evidence that glycolysis inhibitors may improve outcomes from other cancer treatments. This mini-review will focus on glyceraldehyde 3-phosphate dehydrogenase (GAPDH), one of the central enzymes in glycolysis. GAPDH has a key role in metabolism, catalyzing the sixth step in glycolysis and generating NADH. GAPDH also has a surprisingly diverse number of localizations, including the nucleus, where it performs multiple functions, and the plasma membrane. One membrane-associated function of GAPDH is stimulating glucose uptake, consistent with a role for GAPDH in energy and metabolite production. The plasma membrane localization of GAPDH and its role in glucose uptake have been verified in neuroblastoma. Membrane-associated GAPDH also participates in iron uptake, although this has not been tested in neuroblastoma. Finally, GAPDH activates autophagy through a nuclear complex with Sirtuin. This review will discuss these activities and their potential role in cancer metabolism, treatment and drug resistance.

Genetic variants in GAPDH confer susceptibility to sporadic Parkinson's disease in a Chinese Han population

BACKGROUND

Accumulating evidence has demonstrated that the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a part of Lewy body inclusions and involves the pathogenesis of Parkinson's disease (PD). However, it remains unknown whether or not genetic variation at the GAPDH locus contributes to the risk for PD.

METHODS

A total of 302 sporadic PD patients and 377 control subjects were recruited in our study for assessing two single nucleotide polymorphisms (rs3741918 and rs1060619) in the GAPDH gene. Both allelic association and additive models were used to analyze association between GAPDH variants and risk for PD.

RESULTS

Both polymorphisms were significantly associated with risk for PD after correction by Bonferroni multiple testing. The minor allele of rs3741918 was associated with decreased risk of sporadic PD (allelic contrast, OR = 0.74, 95% CI: 0.59-0.93, corrected P = 0.028; additive model, OR = 0.73, 95% CI: 0.58-0.92, corrected P = 0.018). While for the rs1060619 locus, the minor allele conferred increased risk for PD (allelic contrast, OR = 1.41, 95% CI: 1.14-1.75, corrected P = 0.007; additive model, OR = 1.43, 95% CI: 1.15-1.79, corrected P = 0.002).

CONCLUSION

Our study indicates that GAPDH variants confer susceptibility to sporadic PD in a Chinese Han population, which is consistent with the role of GAPDH protein in neuronal apoptosis. To our knowledge, this is the first study of genetic association between GAPDH locus and risk for PD in the Chinese population.

Compartmentation of GAPDH

The concept of the cytosol as a space that contains discrete zones of metabolites is discussed relative to the contribution of GAPDH. GAPDH is directed to very specific cell compartments. This chapter describes the utilization of GAPDH's enzymatic function for focal demands (i.e. ATP/ADP and NAD(+)/NADH), and offers a speculative role for GAPDH as perhaps moderating local concentrations of inorganic phosphate and hydrogen ions (i.e. co-substrate and co-product of the glycolytic reaction, respectively). Where known, the structural features of the binding between GAPDH and the compartment components are discussed. The nuances, which are associated with the intracellular distribution of GAPDH, appear to be specific to the cell-type, particularly with regards to the various plasma membrane proteins to which GAPDH binds. The chapter includes discussion on the curious observation of GAPDH being localized to the external surface of the plasma membrane in a human cell type. The default perspective has been that GAPDH localization is synonymous with compartmentation of glycolytic energy. The chapter discusses GAPDH translocation to the nucleus and to non-nuclear cellular structures, emphasizing its glycolytic function. Nevertheless, it is becoming clear that alternate functions of GAPDH play a role in compartmentation, particularly in the translocation to the nucleus.

Levodopa activates apoptosis signaling kinase 1 (ASK1) and promotes apoptosis in a neuronal model: implications for the treatment of Parkinson's disease

Oxidative stress is implicated in the etiology of Parkinson's disease (PD), the second most common neurodegenerative disease. PD is treated with chronic administration of l-3,4-dihydroxyphenylalanine (levodopa, L-DOPA), and typically, increasing doses are used during progression of the disease. Paradoxically, L-DOPA is a pro-oxidant and induces cell death in cellular models of PD through disruption of sulfhydryl homeostasis involving loss of the thiol-disulfide oxidoreductase functions of the glutaredoxin (Grx1) and thioredoxin (Trx1) enzyme systems [Sabens, E. A., Distler, A. M., and Mieyal, J. J. (2010) Biochemistry 49 (12), 2715-2724]. Considering this loss of both Grx1 and Trx1 activities upon L-DOPA treatment, we sought to elucidate the mechanism(s) of L-DOPA-induced apoptosis. In other contexts, both the NFκB (nuclear factor κB) pathway and the ASK1 (apoptosis signaling kinase 1) pathway have been shown to be regulated by both Grx1 and Trx1, and both pathways have been implicated in cell death signaling in model systems of PD. Moreover, mixed lineage kinase (MLK) has been considered as a potential therapeutic target for PD. Using SHSY5Y cells as model dopaminergic neurons, we found that NFκB activity was not altered by L-DOPA treatment, and the selective MLK inhibitor (CEP-1347) did not protect the cells from L-DOPA. In contrast, ASK1 was activated with L-DOPA treatment as indicated by phosphorylation of its downstream mitogen-activated protein kinases (MAPK), p38 and JNK. Chemical inhibition of either p38 or JNK provided protection from L-DOPA-induced apoptosis. Moreover, direct knockdown of ASK1 protected from L-DOPA-induced neuronal cell death. These results identify ASK1 as the main pro-apoptotic pathway activated in response to L-DOPA treatment, implicating it as a potential target for adjunct therapy in PD.

Protein S-nitrosylation: role for nitric oxide signaling in neuronal death

BACKGROUND

One of the signaling mechanisms mediated by nitric oxide (NO) is through S-nitrosylation, the reversible redox-based modification of cysteine residues, on target proteins that regulate a myriad of physiological and pathophysiological processes. In particular, an increasing number of studies have identified important roles for S-nitrosylation in regulating cell death.

SCOPE OF REVIEW

The present review focuses on different targets and functional consequences associated with nitric oxide and protein S-nitrosylation during neuronal cell death.

MAJOR CONCLUSIONS

S-Nitrosylation exhibits double-edged effects dependent on the levels, spatiotemporal distribution, and origins of NO in the brain: in general Snitrosylation resulting from the basal low level of NO in cells exerts anti-cell death effects, whereas S-nitrosylation elicited by induced NO upon stressed conditions is implicated in pro-cell death effects.

GENERAL SIGNIFICANCE

Dysregulated protein S-nitrosylation is implicated in the pathogenesis of several diseases including degenerative diseases of the central nervous system (CNS). Elucidating specific targets of S-nitrosylation as well as their regulatory mechanisms may aid in the development of therapeutic intervention in a wide range of brain diseases.

Glyceraldehyde-3-phosphate dehydrogenase: activity inhibition and protein overexpression in rotenone models for Parkinson's disease

Rotenone, a widely used pesticide and an environmental risk factor for Parkinson's disease (PD), induces nigrostriatal injury, Lewy body-like inclusions, and Parkinsonian symptoms in rat models for PD. Our previous data indicated that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) overexpression and glycolytic inhibition were co-current in rotenone-induced PC12 (rat adrenal pheochromocytoma cells) cell death. However, whether GAPDH overexpression plays any role in dopaminergic neurodegeneration in vivo remains unknown. In this study, we have found that GAPDH overexpression and GAPDH-positive Lewy body-like aggregates in nigral dopaminergic neurons while nigral GAPDH glycolytic activity decreases in rotenone-based PD animal models. Furthermore, GAPDH knockdown reduces rotenone toxicity significantly in PC12. These in vitro and in vivo data suggest that GAPDH contributes to the pathogenesis of Parkinson's disease, possibly representing a new molecular target for neuroprotective strategies and alternative therapies for PD.

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.

Oxidatively modified glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and Alzheimer's disease: many pathways to neurodegeneration

Recently, the oxidoreductase, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), has become a subject of interest as more and more studies reveal a surfeit of diverse GAPDH functions, extending beyond traditional aerobic metabolism of glucose. As a result of multiple isoforms and cellular locales, GAPDH is able to come in contact with a variety of small molecules, proteins, membranes, etc., that play important roles in normal and pathologic cell function. Specifically, GAPDH has been shown to interact with neurodegenerative disease-associated proteins, including the amyloid-beta protein precursor (AbetaPP). Studies from our laboratory have shown significant inhibition of GAPDH dehydrogenase activity in Alzheimer's disease (AD) brain due to oxidative modification. Although oxidative stress and damage is a common phenomenon in the AD brain, it would seem that inhibition of glycolytic enzyme activity is merely one avenue in which AD pathology affects neuronal cell development and survival, as oxidative modification can also impart a toxic gain-of-function to many proteins, including GAPDH. In this review, we examine the many functions of GAPDH with respect to AD brain; in particular, the apparent role(s) of GAPDH in AD-related apoptotic cell death is emphasized.

The diverse functions of GAPDH: views from different subcellular compartments

Multiple roles for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) have been recently appreciated. In addition to the cytoplasm where the majority of GAPDH is located under the basal condition, GAPDH is also found in the particulate fractions, such as the nucleus, the mitochondria, and the small vesicular fractions. When cells are exposed to various stressors, dynamic subcellular re-distribution of GAPDH occurs. Here we review these multifunctional properties of GAPDH, especially linking them to its oligomerization, posttranslational modification, and subcellular localization. This includes mechanistic descriptions of how S-nitrosylation of GAPDH under oxidative stress may lead to cell death/dysfunction via nuclear translocation of GAPDH, which is counteracted by a cytosolic GOSPEL. GAPDH is also involved in various diseases, especially neurodegenerative disorders and cancers. Therapeutic strategies to these conditions based on molecular understanding of GAPDH are discussed.

Direct binding of glyceraldehyde 3-phosphate dehydrogenase to telomeric DNA protects telomeres against chemotherapy-induced rapid degradation

Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is a glycolytic enzyme that displays several non-glycolytic activities, including the maintenance and/or protection of telomeres. In this study, we determined the molecular mechanism and biological role of the interaction between GAPDH and human telomeric DNA. Using gel-shift assays, we show that recombinant GAPDH binds directly with high affinity (K(d)=45 nM) to a single-stranded oligonucleotide comprising three telomeric DNA repeats, and that nucleotides T1, G5, and G6 of the TTAGGG repeat are essential for binding. The stoichiometry of the interaction is 2:1 (DNA:GAPDH), and GAPDH appears to form a high-molecular-weight complex when bound to the oligonucleotide. Mutation of Asp32 and Cys149, which are localized to the NAD-binding site and the active-site center of GAPDH, respectively, produced mutants that almost completely lost their telomere-binding functions both in vitro and in situ (in A549 human lung cancer cells). Treatment of A549 cells with the chemotherapeutic agents gemcitabine and doxorubicin resulted in increased nuclear localization of expressed wild-type GAPDH, where it protected telomeres against rapid degradation, concomitant with increased resistance to the growth-inhibitory effects of these drugs. The non-DNA-binding mutants of GAPDH also localized to the nucleus when expressed in A549 cells, but did not confer any significant protection of telomeres against chemotherapy-induced degradation or growth inhibition; this occurred without the involvement of caspase activation or apoptosis regulation. Overall, these data demonstrate that GAPDH binds telomeric DNA directly in vitro and may have a biological role in the protection of telomeres against rapid degradation in response to chemotherapeutic agents in A549 human lung cancer cells.

Novel roles for GAPDH in cell death and carcinogenesis

Growing evidence points to the fact that glucose metabolism has a central role in carcinogenesis. Among the enzymes controlling this energy production pathway, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is of particular interest. Initially identified as a glycolytic enzyme and considered as a housekeeping gene, this enzyme is actually tightly regulated and is involved in numerous cellular functions. Particularly intriguing are recent reports describing GAPDH as a regulator of cell death. However, its role in cell death is unclear; whereas some studies point toward a proapoptotic function, others describe a protective role and suggest its participation in tumor progression. In this study, we highlight recent findings and discuss potential mechanisms through which cells regulate GAPDH to fulfill its diverse functions to influence cell fate.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) interaction with 3' ends of Japanese encephalitis virus RNA and colocalization with the viral NS5 protein

Replication of the Japanese encephalitis virus (JEV) genome depends on host factors for successfully completing their life cycles; to do this, host factors have been recruited and/or relocated to the site of viral replication. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a cellular metabolic protein, was found to colocalize with viral RNA-dependent RNA polymerase (NS5) in JEV-infected cells. Subcellular fractionation further indicated that GAPDH remained relatively constant in the cytosol, while increasing at 12 to 24 hours postinfection (hpi) and decreasing at 36 hpi in the nuclear fraction of infected cells. In contrast, the redistribution patterns of GAPDH were not observed in the uninfected cells. Co-immunoprecipitation of GAPDH and JEV NS5 protein revealed no direct protein-protein interaction; instead, GAPDH binds to the 3' termini of plus- and minus-strand RNAs of JEV by electrophoretic mobility shift assays. Accordingly, GAPDH binds to the minus strand more efficiently than to the plus strand of JEV RNAs. This study highlights the findings that infection of JEV changes subcellular localization of GAPDH suggesting that this metabolic enzyme may play a role in JEV replication.

A prolyl oligopeptidase inhibitor, Z-Pro-Prolinal, inhibits glyceraldehyde-3-phosphate dehydrogenase translocation and production of reactive oxygen species in CV1-P cells exposed to 6-hydroxydopamine

We studied the ability of prolyl oligopeptidase (POP) inhibitors, Z-Pro-Prolinal and JTP-4819, to prevent translocation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and formation of reactive oxygen species (ROS), in 6-hydroxydopamine (6-OHDA) and cytosine arabinoside (Ara-C) treated monkey fibroblast (CV1-P) and human neuroblastoma (SH-SY5Y) cells. The cells were pretreated with POP inhibitors (30 min) before addition of toxicants. GAPDH was analyzed by Western hybridization, ROS by fluorescent 2'7'-dichlorodihydro-fluorescein diacetate, and viability by the MTT method. Both toxicants induced GAPDH translocation to the particulate fraction (mitochondria and nuclei). Z-Pro-Prolinal was able to inhibit the translocation in 6-OHDA-exposed CV1-P cells. In SH-SY5Y cells and in JTP-4819 pretreated cells, no prevention of translocation was seen. However, the intensity of GAPDH in cytosolic fraction increased. Both inhibitors blocked 6-OHDA-induced ROS-production to the control level in CV1-P but, not in SH-SY5Y cells, without affecting their viability. In conclusion, POP inhibitors are able to prevent certain cell stress related factors such as ROS production or GAPDH translocation.

Nuclear localization of glyceraldehyde-3-phosphate dehydrogenase is not involved in the initiation of apoptosis induced by 1-Methyl-4-phenyl-pyridium iodide (MPP+)

Nuclear localization of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is implicated in the process of apoptosis. To study the function of GAPDH, we expressed GAPDH C-terminally fused with or without nuclear localization signal (NLS) in SH-SY5Y and NB41A3 cells using a retrovirus expression system. GAPDH carrying NLS (GAPDH-NLS) was expressed mainly in the nucleus. However, expression of GAPDH-NLS did not cause any difference in cell survival rate as compared to that of the vector alone or GAPDH without NLS. Treatment with 1-Methyl-4-phenyl-pyridium iodide (MPP+) caused no difference in the cell survival rate or in the pattern or extent of apoptosis among the three transductants. In the cells expressing GAPDH without NLS, MPP+ did not cause visible translocation of GAPDH into nucleus before the onset of apoptosis. Since GAPDH is known to comprise a CRM1-mediated nuclear export signal, we blocked the nuclear export of GAPDH by treatment with leptomycin B, an inhibitor of CRM1-mediated nuclear export. The treatment did not cause any difference in apoptosis among the three transductants. An additional treatment with MPP+ induced no apoptotic difference in these cells. Thus, we have concluded that a simple nuclear localization of GAPDH does not induce apoptosis, and that MPP+-induced apoptosis is not caused by nuclear translocation of GAPDH.

Glyceraldehyde-3-phosphate dehydrogenase, apoptosis, and neurodegenerative diseases

Increasing evidence supports the notion that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a protein with multiple functions, including its surprising role in apoptosis. GAPDH is overexpressed and accumulates in the nucleus during apoptosis induced by a variety of insults in diverse cell types. Knockdown of GAPDH using an antisense strategy demonstrates its involvement in the apoptotic cascade in which GAPDH nuclear translocation appears essential. Knowledge concerning the mechanisms underlying GAPDH nuclear translocation and subsequent cell death is growing. Additional evidence suggests that GAPDH may be an intracellular sensor of oxidative stress during early apoptosis. Abnormal expression, nuclear accumulation, changes in physical properties, and loss of glycolytic activity of GAPDH have been found in cellular and transgenic models as well as postmortem tissues of several neurodegenerative diseases. The interaction of GAPDH with disease-related proteins as well as drugs used to treat these diseases suggests that it is a potential molecular target for drug development.

Bcl-xL blocks mitochondrial multiple conductance channel activation and inhibits 6-OHDA-induced death in SH-SY5Y cells

Apoptosis is an active process that is regulated by different signalling pathways. One of the more important organelles involved in apoptosis regulation is the mitochondrion. Electron chain transport disruption increases free radical production leading to multiple conductance channel opening, release of cytochrome c and caspase activation. This death pathway can be blocked by anti-apoptotic members of the Bcl-2 protein family that might shift redox potential to a more reduced state, preventing free radical-mediated damage. 6-Hydroxydopamine (6-OHDA) has been widely used to generate Parkinson's disease-like models. It is able to generate free radicals and to induce catecholaminergic cell death. In this paper we have used the human neuroblastoma cell line SH-SY5Y overexpressing Bcl-x(L) as a model to gain insights into the mechanisms through which Bcl-x(L) blocks 6-OHDA-induced cell death and to identify the molecular targets for this action. Herein, we present evidence supporting that the Bcl-x(L)-anti-apoptotic signal pathway seems to prevent mitochondrial multiple conductance channel opening, cytochrome c release and caspase-3 like activity following 6-OHDA treatment in the human neuroblastoma cell line SH-SY5Y.

An alternative strategy to determine the mitochondrial proteome using sucrose gradient fractionation and 1D PAGE on highly purified human heart mitochondria

An alternative strategy for mitochondrial proteomics is described that is complementary to previous investigations using 2D PAGE techniques. The strategy involves (a) obtaining highly purified preparations of human heart mitochondria using metrizamide gradients to remove cytosolic and other subcellular contaminant proteins; (b) separation of mitochondrial protein complexes using sucrose density gradients after solubilization with n-dodecyl-beta-D-maltoside; (c) 1D electrophoresis of the sucrose gradient fractions; (d) high-throughput proteomics using robotic gel band excision, in-gel digestion, MALDI target spotting and automated spectral acquisition; and (e) protein identification from mixtures of tryptic peptides by high-precision peptide mass fingerprinting. Using this approach, we rapidly identified 82 bona fide or potential mitochondrial proteins, 40 of which have not been previously reported using 2D PAGE techniques. These proteins include small complex I and complex IV subunits, as well as very basic and hydrophobic transmembrane proteins such as the adenine nucleotide translocase that are not recovered in 2D gels. The technique described here should also be useful for the identification of new protein-protein associations as exemplified by the validation of a recently discovered complex that involves proteins belonging to the prohibitin family.

Dopamine-derived endogenous N-methyl-(R)-salsolinol: its role in Parkinson's disease

A dopamine-derived alkaloid, N-methyl-(R)-salsolinol [NM(R)Sal], enantioselectively occurs in human brains and accumulates in the nigrostriatal system. It increases in the cerebrospinal fluid (CSF) of parkinsonian patients and the activity of a neutral (R)-salsolinol [(R)Sal] N-methyltransferase, a key enzyme in the biosynthesis of this toxin, increases in the lymphocytes from parkinsonian patients, suggesting its involvement in the pathogenesis of Parkinson's disease (PD). The studies of animal and cellular models of PD proved that this isoquinoline is selectively cytotoxic to dopamine neurons. Using human dopaminergic SH-SY5Y cells, NM(R)Sal induces apoptosis by the activation of the apoptotic cascade initiated in mitochondria. In this article, we review the recent advance in proving our hypothesis that the dopamine-derived neurotoxin causes the selective depletion of dopamine neurons in PD.

Expression of sphingosine kinase gene in the interactions between human gastric carcinoma cell and vascular endothelial cell

AIM: To study the interactions between human gastric carcinoma cell (HGCC) and human vascular endothelial cell (HVEC), and if the expression of sphingosine kinase (SPK) gene was involved in these interactions.

METHODS: The specific inhibitor to SPK, dimethyl sphingosine (DMS), was added acting on HGCC and HVEC, then the cell proliferation was measured by MTT. The conditioned mediums (CMs) of HGCC and HVEC were prepared. The CM of one kind of cell was added to the other kind of cell, and the cell proliferation was measured by MTT. After the action of CM, the cellular expression of SPK gene in mRNA level was detected with in situ hybridization (ISH).

RESULTS: DMS could almost completely inhibit the proliferation of HGCC and HVEC. The growth inhibitory rates could amount to 97.21%, 83.42%, respectively (P < 0.01). The CM of HGCC could stimulate the growth of HVEC (2.70 ± 0.01, P < 0.01) while the CM of HVEC could inhibit the growth of HGCC (52.97% ± 0.01%, P < 0.01). There was no significant change in the mRNA level of SPK gene in one kind of cell after the action of the CM of the other kind of cell.

CONCLUSION: SPK plays a key role in regulating the proliferation of HGCC and HVEC. There exist complicated interactions between HGCC and HVEC. HGCC can significantly stimulate the growth of HVEC while HVEC can significantly inhibit the growth of HGCC. The expression of SPK gene is not involved in the interactions.