Glyceraldehyde-3-phosphate Dehydrogenase Activity Research Articles

The role of GAPDH in the selective toxicity of CNP in melanoma cells.

Malignant melanoma is the most aggressive form of skin cancer with a rather poor prognosis. Standard chemotherapy often results in severe side effects on normal (healthy) cells finally being difficult to tolerate for the patients. Shown by us earlier, cerium oxide nanoparticles (CNP, nanoceria) selectively killed A375 melanoma cells while not being cytotoxic at identical concentrations on non-cancerous cells. In conclusion, the redox-active CNP exhibited both prooxidative as well as antioxidative properties. In that context, CNP induced mitochondrial dysfunction in the studied melanoma cells via generation of reactive oxygene species (primarily hydrogen peroxide (H2O2)), but that does not account for 100% of the toxicity. Cancer cells often show an increased glycolytic rate (Warburg effect), therefore we focused on CNP mediated changes of the glucose metabolism. It has been shown before that glyceraldehyde 3-phosphate dehydrogenase (GAPDH) activity is regulated via oxidation of a cysteine in the active center of the enzyme with a subsequent loss of activity. Upon CNP treatment, formation of cellular lactate and GAPDH activity were significantly lowered. The treatment of melanoma cells and melanocytes with the GAPDH inhibitor heptelidic acid (HA) decreased viability to a much higher extent in the cancer cells than in the studied normal (healthy) cells, highlighting and supporting the important role of GAPDH in cancer cells. We identified glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as a target protein for CNP mediated thiol oxidation.

AMPK Controls Glycolytic Compensation in Gvhd-Causing T Cells

Background: The heightened metabolic requirements of alloreactive T cells following allogeneic stem cell transplantation represents a promising area for therapeutic intervention. We have shown that during the initiation of acute graft-versus-host-disease (aGVHD), murine T cells upregulate activity of AMP-activated protein kinase (AMPK), a cellular energy sensor that regulates oxidative and mitochondrial metabolism. Further, transfer of allogeneic T cells deficient in AMPK (AMPK KO) increased recipient survival and decreased disease severity while still preserving leukemia clearance. In the current studies, we demonstrate a novel role for AMPK in controlling glycolytic compensation, both in vitro and vivo, and provide a mechanism as to why cells lacking AMPK are unable to perform this vital function. Together, these data highlight the potential clinical utility in targeting metabolic decision-making to curtail T cell-mediated inflammatory responses, with significant therapeutic implications for the prevention and treatment of aGVHD. Methods: AMPK-deficient murine T cells from AMPKa1/a2 dKO C57BL/6J mice were transplanted into allogeneic B6D2F1 recipients and recovered on day 7 post-transplant. To delete AMPK in primary human T cells, T cells were isolated from healthy donors and electroporated with Cas 9 ribonucleoprotein complexes targeting the AMPKa1 locus. Glycolytic compensation was assessed by measuring extracellular acidification rates (ECAR) using the Agilent Seahorse analyzer and a mitochondrial stress kit. Intracellular cytokine expression for IFNgamma was assessed in day 7 murine T cells following re-stimulation with F1 splenocytes in the presence of Brefeldin A. Aldolase A and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) enzymatic assays were run on cell lysates with Biovision-Abcam kits according to manufacturer instructions. To measure GAPDH activity, T cells were positively selected for CD45.1 from day 7 recipient spleens, followed by cell lysis and detection of enzymatic activity. Results: AMPK KO murine T cells recovered on day 7 were unable to mediate a compensatory increase in glycolysis following inhibition of the electron transport chain (Figure 1A), (-6.499±5.156 vs 29.11±7.064, p<0.0001). Human T cells lacking AMPK gave similar results, with glycolytic compensation impaired both in vitro and following human T cell expansion in vivo in a xenogeneic model of GVHD. Immunoprecipitation of proteins from day 7 murine T cells, using an antibody specific to phosphorylated AMPK targets, recovered lower levels of multiple glycolytic enzymes including aldolase, enolase, pyruvate kinase M, and GAPDH (Figure 1B). Functionally, murine T cells lacking AMPK exhibited impaired aldolase activity following anti-CD3/CD28 stimulation and a decrease in GAPDH activity on day 7 post-transplant. Importantly, these changes in glycolysis correlated with an impaired ability of AMPK KO T cells to produce significant amounts of IFNγ upon antigenic re-stimulation with F1 splenocytes. Discussion: Our results demonstrate that in addition to influencing oxidative metabolism, AMPK also plays a role in glycolytic metabolism during GVHD in both murine and human T cells. Further, our data suggest that the more prominent lesion in human T cells post-transplant was in glycolysis , a result supported by the novel observation that a set of glycolysis-related proteins are immunoprecipitated together at much lower rates in the absence of AMPK. These findings suggest a model in which AMPK phosphorylation provides a nidus for important interactions among glycolytic enzymes and that in the absence of AMPK, these interactions are lessened, and glycolysis is consequently reduced. Important to our understanding of GVHD pathogenesis, rates of T cell glycolysis can be directly linked to IFNγ production, where reduced glycolytic activity frees GAPDH to sequester IFNγ transcripts and thereby limit IFNγ protein translation. Altogether, these results document a prominent role for AMPK in controlling T cell glycolytic activity during GVHD development and offer an additional mechanistic explanation for the decreased severity of GVHD seen following transplantation of AMPK KO T cells. Consistently similar results in human xenogeneic T cells provides a further strong rationale for development of AMPK inhibition as a clinically translatable strategy for GVHD prevention and treatment.

Biochemical evidence that the whole compartment activity behavior of GAPDH differs between the cytoplasm and nucleus.

Some metabolic enzymes normally occur in the nucleus and cytoplasm. These compartments differ in molecular composition. Since post-translational modification and interaction with allosteric effectors can tune enzyme activity, it follows that the behavior of an enzyme as a catalyst may differ between the cytoplasm and nucleus. We explored this possibility for the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Homogenates of pristine nuclei and cytoplasms isolated from Xenopus laevis oocytes were used for whole compartment activity profiling in a near-physiological buffer. Titrations of NAD+ revealed similar whole compartment activity profiles for GAPDH in nuclear and cytoplasmic homogenates. Surprisingly however GAPDH in these compartments did not have the same behavior in assays of the dependence of initial velocity (v0) on G3P concentration. First, the peak v0 for nuclear GAPDH was up to 2.5-fold higher than the peak for cytoplasmic GAPDH. Second, while Michaelis Menten-like behavior was observed in all assays of cytoplasm, the v0 versus [G3P] plots for nuclear GAPDH typically exhibited a non-Michaelis Menten (sigmoidal) profile. Apparent Km and Vmax (G3P) values for nuclear GAPDH activity were highly variable, even between replicates of the same sample. Possible sources of this variability include in vitro processing of a metabolite that allosterically regulates GAPDH, turnover of a post-translational modification of the enzyme, and fluctuation of the state of interaction of GAPDH with other proteins. Collectively these findings are consistent with the hypothesis that the environment of the nucleus is distinct from the environment of the cytoplasm with regard to GAPDH activity and its modulation. This finding warrants further comparison of the regulation of nuclear and cytoplasmic GAPDH, as well as whole compartment activity profiling of other enzymes of metabolism with cytosolic and nuclear pools.

NTRC regulates CP12 to activate Calvin–Benson cycle during cold acclimation

NADPH-dependent thioredoxin reductase C (NTRC) is a chloroplast redox regulator in algae and plants. Here, we used site-specific mutation analyses of the thioredoxin domain active site of NTRC in the green alga Chlamydomonas reinhardtii to show that NTRC mediates cold tolerance in a redox-dependent manner. By means of coimmunoprecipitation and mass spectrometry, a redox- and cold-dependent binding of the Calvin-Benson Cycle Protein 12 (CP12) to NTRC was identified. NTRC was subsequently demonstrated to directly reduce CP12 of C. reinhardtii as well as that of the vascular plant Arabidopsis thaliana in vitro. As a scaffold protein, CP12 joins the Calvin-Benson cycle enzymes phosphoribulokinase (PRK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) to form an autoinhibitory supracomplex. Using size-exclusion chromatography, NTRC from both organisms was shown to control the integrity of this complex in vitro and thereby PRK and GAPDH activities in the cold. Thus, NTRC apparently reduces CP12, hence triggering the dissociation of the PRK/CP12/GAPDH complex in the cold. Like the ntrc::aphVIII mutant, CRISPR-based cp12::emx1 mutants also exhibited a redox-dependent cold phenotype. In addition, CP12 deletion resulted in robust decreases in both PRK and GAPDH protein levels implying a protein protection effect of CP12. Both CP12 functions are critical for preparing a repertoire of enzymes for rapid activation in response to environmental changes. This provides a crucial mechanism for cold acclimation.

Biochemical responses in mice induced by saxitoxins extracted from the cockles Acanthocardia tuberculatum.

Harmful algae blooms have increased in frequency and geographic range in recent decades, and they produce toxins strains such as saxitoxins (STXs). they block voltage-gated sodium channels and can lead to several poisonings and the death of organisms that pose a significant risk to public and environmental health. The study of STXs toxicity has been carried out but little is known about the response of antioxidant enzymes activities to STXs in mice. The purpose of this study was to evaluate biochemical responses and oxidative stress induced by STXs extracted from Acanthocardia tuberculatum. To this end, daily, mice were treated orally for 7 days with sublethal concentrations (10 mg/100 g mouse). The animal's liver was assessed using biomarkers such as activities of catalase (CAT), thiobarbituric acid reactive substances (TBARS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and succinate dehydrogenase (SDH). In the blood, plasmatic markers were analysed as glutamic oxalic transaminase (GOT), glutamic pyruvic transaminase (GPT), creatinine phosphokinase (CPK), lactate dehydrogenase (LDH), urea and creatinine. Globally, test toxicity test showed a significant decrease in the weight at 10 mg /100 g mouse, and the results showed an increase of GPT, GOT, CPK, LDH, CAT and TBARS activities and the inhibitory effect of GAPDH activities but creatinine, urea and SDH activities showed no significative difference from the control. We concluded that STXs induce oxidative stress breaking in mice the balance of the defence system and causing oxidations reactions. Moreover, STXs affect energy metabolism in mice, however, renal function in mice is not affected by exposure to STXs.

Acetate regulates GAPDH acetylation and T helper 1 cell differentiation.

The short-chain fatty acid metabolite acetyl-coenzyme A (acetyl-CoA) has emerged as a major signal transducer that can broadly affect cell fate and function, at least partly by influencing acetylation of key proteins. The mechanism by which acetyl-CoA regulates CD4+ T-cell fate determination remains poorly understood. Herein, we report that acetate modulates glyceraldehyde-3-phosphate dehydrogenase (GAPDH) acetylation and CD4+ T helper 1 (Th1) cell differentiation by altering acetyl-CoA levels. Our transcriptome profiling shows that acetate is a robust positive regulator of CD4+ T-cell gene expression typical of glycolysis. We further show that acetate potentiates GAPDH activity, aerobic glycolysis, and Th1 polarization through regulation of GAPDH acetylation levels. This acetate-dependent GAPDH acetylation occurs in a dose- and time-dependent manner, while decreasing acetyl-CoA levels by fatty acid oxidation inhibition results in a decline in acetyl-GAPDH levels. Thus, acetate functions as a potent metabolic regulator in CD4+ T-cells by promoting GAPDH acetylation and Th1 cell fate decision.

Measuring the Oxidation State and Enzymatic Activity of Glyceraldehyde Phosphate Dehydrogenase (GAPDH).

Glyceraldehyde phosphate dehydrogenase (GAPDH) is a highly conserved, essential, and abundant enzyme that catalyzes a rate-determining step of glycolysis. GAPDH catalyzes the nicotinamide adenine dinucleotide (NAD+)- and inorganic phosphate-dependent oxidation and phosphorylation of glyceraldehyde phosphate (GAP) to form 1,3-bisphosphoglycerate (BPG). As part of its mechanism of action, GAPDH employs a redox-sensitive cysteine that serves as a nucleophile to form a covalent adduct with GAP in order to set-up subsequent oxidation and phosphorylation steps. As a result of the redox sensitivity of the active site cysteine residue, GAPDH is susceptible to oxidative inactivation by oxidants such as hydrogen peroxide (H2O2). Indeed, numerous studies have demonstrated that oxidative inactivation of GAPDH has important metabolic consequences for adaptation to life in air and oxidative stress since decreased GAPDH activity results in the rerouting of carbon flux away from glycolysis and toward the pentose phosphate pathway to produce the key cellular reductant and antioxidant, NADPH. Thus, the ability to probe GAPDH oxidation and activity provides an important snapshot of the intracellular redox environment and glycolytic flux. Herein, we describe methods to measure reduced and oxidized GAPDH using thiol alkylation assays as well as GAPDH enzymatic activity.

Multi-Omics Analysis Reveals the Nitrogen Removal Mechanism Induced by Electron Flow during the Start-up of the Anammox-Centered Process.

Significant progress in understanding the key enzymes or species of anammox has been made; however, the nitrogen removal mechanism in complex coupling systems centered on anammox remains limited. In this study, by the combination of metagenomics-metatranscriptomics analyses, the nitrogen removal in the anammox-centered coupling system that entails partial denitrification (PD) and hydrolytic acidification (HA, A-PDHA) was elucidated to be the nitrogen transformation driven by the electron generation-transport-consumption process. The results showed that a total nitrogen (TN) removal efficiency of >98%, with a TN effluence of <1 mg/L and a TN removal contribution via anammox of >98%, was achieved after 59 days under famine operation and alkaline conditions during the start-up process. Further investigation confirmed that famine operation promoted the activity of genes responsible for electron generation in anammox, and increased the abundance or expression of genes related to electron consumption. Alkaline conditions enhanced the electron generation for PD by upregulating the activity of glyceraldehyde 3-phosphate dehydrogenase and strengthened electron transfer by increasing the gene encoding quinone pool. Altogether, these variations in the electron flow led to efficient nitrogen removal. These results improve our understanding of the nitrogen removal mechanism and application of the anammox-centered coupling systems in treating nitrogen wastewater.

Nephritis-Associated Plasmin Receptor (NAPlr): An Essential Inducer of C3-Dominant Glomerular Injury and a Potential Key Diagnostic Biomarker of Infection-Related Glomerulonephritis (IRGN).

Nephritis-associated plasmin receptor (NAPlr) was originally isolated from the cytoplasmic fraction of group A Streptococci, and was found to be the same molecule as streptococcal glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and plasmin receptor (Plr) on the basis of nucleotide and amino acid sequence homology. Its main functions include GAPDH activity, plasmin-binding capacity, and direct activation of the complement alternative pathway (A-P). Plasmin trapped by deposited NAPlr triggers the degradation of extracellular matrix proteins, such as glomerular basement membranes and mesangial matrix, and the accumulation of macrophages and neutrophils, leading to the induction of plasmin-related endocapillary glomerular inflammation. Deposited NAPlr at glomerular endocapillary site directly activates the complement A-P, and the endocapillary release of complement-related anaphylatoxins, C3a and C5a, amplify the in situ endocapillary glomerular inflammation. Subsequently, circulating and in situ-formed immune complexes participate in the glomerular injury resulting in NAPlr-mediated glomerulonephritis. The disease framework of infection-related glomerulonephritis (IRGN) has been further expanded. GAPDH of various bacteria other than Streptococci have been found to react with anti-NAPlr antibodies and to possess plasmin-binding activities, allowing glomerular NAPlr and plasmin activity to be utilized as key biomarkers of IRGN.

3-Bromo-Isoxazoline Derivatives Inhibit GAPDH Enzyme in PDAC Cells Triggering Autophagy and Apoptotic Cell Death.

Simple SummaryCancer cells largely use glycolysis to obtain both chemical energy (ATP) and metabolic intermediates for anabolic reactions, and several studies proved that the blockage of the glycolytic pathway is an efficient anticancer strategy. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a key tetrameric glycolytic enzyme, has raised considerable attention in recent years as a potential drug target in pathological conditions in which glycolytic flux has a crucial role. In cancers, a recognized involvement of the Warburg effect, as a key mechanism for cancer-cell energetic metabolism, favouring tumour progression and invasion, has contributed to highlight human GAPDH (hGAPDH) as an effective drug target to specifically hit cancer cells exhibiting metabolic dependence on glycolysis, without significantly affecting normal cells. In this study, we tested the effects of 3-bromo-isoxazoline derivatives specifically designed to bind and inhibit GAPDH activity, in pancreatic ductal-adenocarcinoma cells.A growing interest in the study of aerobic glycolysis as a key pathway for cancer-cell energetic metabolism, favouring tumour progression and invasion, has led to consider GAPDH as an effective drug target to specifically hit cancer cells. In this study, we have investigated a panel of 3-bromo-isoxazoline derivatives based on previously identified inhibitors of Plasmodium falciparum GAPDH (PfGAPDH). The compounds are active, to a different extent, as inhibitors of human-recombinant GAPDH. They showed an antiproliferative effect on pancreatic ductal-adenocarcinoma cells (PDAC) and pancreatic-cancer stem cells (CSCs), and among them two promising compounds were selected to be tested in vivo. Interestingly, these compounds were not effective in fibroblasts. The AXP-3019 derivative was able to block PDAC-cell growth in mice xenograft without apparent toxicity. The overall results support the assumption that selective inhibition of the glycolytic pathway, by targeting GAPDH, is an effective therapy for pancreatic cancer and that 3-bromo-isoxazoline derivatives represent a new class of anti-cancer compounds targeting glycolysis.

Comparison of endogenous development, invasion ability and apoptotic features between diclazuril resistant and sensitive strains of Eimeria tenella

Diclazuril (DIC) is widely used in the poultry industry to control coccidiosis. However, drug resistance makes it less effective, and the underlying mechanism remains unclear. One DIC-resistant E. tenella (RE) isolate and one sensitive E. tenella (SE) isolate were used to compare the differences in their endogenous development, pathogenicity, invasion-related gene expression and apoptotic characteristics. Chickens were allocated into four groups to receive RE or SE strain and their corresponding DIC treatment or not. Caeca tissues were sampled at 96 h, 120 h and 144 h post-infection (PI) for pathological analysis. Meanwhile, second-generation merozoites (Mz2) were separated at 120 h PI to detect alterations in mitochondrial membrane potential (MMP), apoptotic rate and caspase-3 activity and mRNA expression of protein phosphatase 5 (PP5), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), actin depolymerizing factor (ADF) and microneme proteins (MICs). Haematoxylin and eosin staining revealed that DIC treatment strictly blocked the development of the SE strain but slightly affected the RE strain. Meanwhile, the number of SE Mz2 and their MMP decreased at the same time the apoptotic rate increased after DIC treatment. Real-time quantitative PCR and caspase-3 activity studies demonstrated that Mz2 from the RE strain had higher mRNA expression of ADF and MICs along with no significant changes in GAPDH and caspase-3 activity under DIC pressure compared to its control; in contrast, the mRNA expression of ADF, MICs and PP5 was markedly suppressed in Mz2 from SE with upregulated caspase-3 activity and GAPDH transcription. In addition, the mRNA expression of GAPDH and PP5 in Mz2 from RE was remarkably higher than that of SE. Taken together, the higher mRNA expression of invasion-related genes and almost unaffected endogenous development provide a better understanding of coccidian resistance to DIC.

Probiotic-derived heptelidic acid exerts antitumor effects on extraintestinal melanoma through glyceraldehyde-3-phosphate dehydrogenase activity control

BackgroundSeveral microorganisms inhabit the mammalian gastrointestinal tract and are associated with the pathogenesis of various diseases, including cancer. Recent studies have indicated that several probiotics produce antitumor molecules and inhibit host tumor progression. We demonstrated that heptelidic acid (HA), a sesquiterpene lactone derived from the probiotic Aspergillus oryzae, exerts antitumor effects against pancreatic cancer in vitro and in vivo. In this study, the antitumor effects of HA against extraintestinal melanoma were assessed in vitro and in vivo.ResultsSulforhodamine B (SRB) assay revealed that the growth of B16F10 cells was significantly inhibited by HA in a concentration-dependent manner. The enzymatic activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) decreased in proportion with the growth inhibition effect of HA. Moreover, oral HA administration significantly suppressed the growth of transplanted B16F10 tumors without any significant changes in biochemical test values. Moreover, GAPDH activity in the transplanted tumor tissues in the HA group significantly decreased compared with that in the PBS group.ConclusionThis study suggests that orally administered HA was absorbed in the gastrointestinal tract, reached the cancer cells transplanted in the skin, and inhibited GAPDH activity, thereby inhibiting the growth of extraintestinal melanoma cells. Thus, this study proposes a novel system for extraintestinal tumor regulation via gut bacteria-derived bioactive mediators.

Efficient inhibition of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by sulfuration with solubilized elemental sulfur

Hydrogen sulfide (H2S), carbon monoxide (CO), and nitric oxide (NO) have garnered increasing scientific interest in recent decades due to their classifications as members of the gasotransmitter family of signaling molecules. Due to the versatility of sulfur redox chemistry in biological systems, H2S specifically is being studied for its ability to modulate cellular redox environments, particularly through the downstream production of oxidized sulfur species. A major mechanism of this regulation is through a posttranslational modification known as persulfidation, where oxidized sulfur atoms are appended to free cysteine in proteins. Currently, it is difficult to discern the activity of H2S itself versus these oxidized sulfur species, particularly sulfane sulfur (S0). We have previously developed a method of solvating S8, a source of pure S0, to more accurately study persulfidation and sulfuration in general. Here, we apply this pure S0 to glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which has previously been shown to be inhibited by S0-containing polysulfides via persulfidation. Using solvated S0, we demonstrate that native, reduced GAPDH can be completely inhibited by sulfuration with S0. Further, oxidized GAPDH activity cannot be rescued using S0, demonstrating that it is the oxidation of reduced GAPDH by S0 that curtails its activity. We also compare inhibition of GAPDH by pure S0 to different polysulfides and demonstrate the modulating effects that pendant alkyl groups have on GAPDH inhibition. These results highlight the promise of this novel, simplified system for the study of S0.

TKTL1 Knockdown Impairs Hypoxia-Induced Glucose-6-phosphate Dehydrogenase and Glyceraldehyde-3-phosphate Dehydrogenase Overexpression

Increased expression of transketolase (TKT) and its isoform transketolase-like-1 (TKTL1) has been related to the malignant leukemia phenotype through promoting an increase in the non-oxidative branch of the pentose phosphate pathway (PPP). Recently, it has also been described that TKTL1 can have a role in survival under hypoxic conditions and in the acquisition of radio resistance. However, TKTL1’s role in triggering metabolic reprogramming under hypoxia in leukemia cells has never been characterized. Using THP-1 AML cells, and by combining metabolomics and transcriptomics techniques, we characterized the impact of TKTL1 knockdown on the metabolic reprogramming triggered by hypoxia. Results demonstrated that TKTL1 knockdown results in a decrease in TKT, glucose-6-phosphate dehydrogenase (G6PD) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activities and impairs the hypoxia-induced overexpression of G6PD and GAPDH, all having significant impacts on the redox capacity of NADPH- and NADH-related cells. Moreover, TKTL1 knockdown impedes hypoxia-induced transcription of genes encoding key enzymes and transporters involved in glucose, PPP and amino acid metabolism, rendering cells unable to switch to enhanced glycolysis under hypoxia. Altogether, our results show that TKTL1 plays a key role in the metabolic adaptation to hypoxia in THP-1 AML cells through modulation of G6PD and GAPDH activities, both regulating glucose/glutamine consumption and the transcriptomic overexpression of key players of PPP, glucose and amino acids metabolism.

Metabolic Energy Insufficiency in Mice Kidney following Short-term Exposure to Lead: An In-vivo Study

Background: Metabolic stress is one of the risk factors of lead-induced functional abnormalities of the tissue. The present study aimsat determining the effect of lead on certain energy metabolic profiles in renal tissue of mice.Method: Swiss albino mice were exposed to Pb by gavages at a 5mg/kg body weight dose for 30 days. After treatment, urinary glucose,glucose 6-phosphatase, lactate dehydrogenase, TCA cycle enzymes, different proteolytic enzyme activities, total, acidic, basic and neutralproteins, protein carbonyl content, glyceraldehyde 3-phosphate dehydrogenase activity, tissue Pb deposition and renal morphologywere examined.Results: Lead exposure resulted in glycosuria and decreased glucose 6-phosphatase activity in the kidney, whereas the lactatedehydrogenase activity was increased in that tissue. The malate dehydrogenase and succinate dehydrogenase activities were stimulatedby Pb, whereas the glyceraldehyde 3-phosphate dehydrogenase activity was inhibited. Degradation of tissue protein was accompaniedwith enhanced protein carbonylation. Significant changes in trypsin, cathepsin and pronase activities were noted. Decreased aminoacid nitrogen in kidney was associated with altered transaminase activity. Additionally, fatty infiltration was observed in associationwith accumulation of elemental lead.Conclusion: It is suggested that sub-acute Pb exposure modulated certain enzymes and intermediates of major energy metabolismpathways in the renal tissue of mice to establish an adaptive mechanism against metabolic distress.

Reduction in Phosphoribulokinase Amount and Re-Routing Metabolism in Chlamydomonas reinhardtii CP12 Mutants.

The chloroplast protein CP12 is involved in the dark/light regulation of the Calvin–Benson–Bassham cycle, in particular, in the dark inhibition of two enzymes: glyceraldehyde−3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK), but other functions related to stress have been proposed. We knocked out the unique CP12 gene to prevent its expression in Chlamydomonas reinhardtii (ΔCP12). The growth rates of both wild-type and ΔCP12 cells were nearly identical, as was the GAPDH protein abundance and activity in both cell lines. On the contrary, the abundance of PRK and its specific activity were significantly reduced in ΔCP12, as revealed by relative quantitative proteomics. Isolated PRK lost irreversibly its activity over-time in vitro, which was prevented in the presence of recombinant CP12 in a redox-independent manner. We have identified amino acid residues in the CP12 protein that are required for this new function preserving PRK activity. Numerous proteins involved in redox homeostasis and stress responses were more abundant and the expressions of various metabolic pathways were also increased or decreased in the absence of CP12. These results highlight CP12 as a moonlighting protein with additional functions beyond its well-known regulatory role in carbon metabolism.

Glycative Stress and the progression of Alzheimer-type Dementia: From the Perspective of Amyloid-beta Clearance

Glycative stress is a conception of a state that causes an excess of carbohydrate-derived or fatty acid-derived short-chain aldehydes in the body. Short-chain aldehydes, which are highly reactive, undergo a carbonylation process with lysine and arginine residues in proteins and form advanced glycation endproducts (AGEs). When postprandial hyperglycemia occurs, open-ring glucose with exposed aldehyde groups (-CHO) increases and various carbohydrate-derived aldehydes are formed simultaneously (this phenomenon is named “aldehyde sparks”). Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is an enzyme abundant intracellularly as the keystone of defense against glycative stress and plays a role in metabolizing highly toxic glyceraldehyde, however, under diabetic conditions, the enzyme activity is markedly reduced by forming S-(2-succinyl) cysteine-GAPDH. We also found that a high-fat diet reduced GAPDH activity and increased glyceraldehyde and methylglyoxal. High animal fat diets in particular require caution because they increase preference dependence on animal fat. In the lipid-rich brain, they promotes the formation of lipid-derived AGEs formed by methylglyoxal and acrolein providing evidence of their close association with amyloid cascade, ultimately leading to the onset of Alzheimer-type dementia. Through the process of amylod beta (Aβ) glycation modification and cross-linking, Aβ polymerization is promoted and deposited in the brain. Thus, neurotoxicity is aggravated. Furthermore, Aβ progresses toward being persistent and Aβ clearance is reduced. Tau proteins similarly undergo glycation modification and trigger polymerization. methylglyoxal or acrolein-derived glycated Aβ clearance by primary microglia cultured cells reduced significantly compared to the unglycated Aβ provides evidence of the reduced clearance upon glycation. It was also shown that melatonin, which promotes glycolytic cross-linking degradation, may promote microglial Aβ phagocytosis. We next plan to examine the potential of plant extracts that promote glycation cross-linking degradation to improve Aβ phagocytosis. Advanced Alzheimer-type dementia with a disoriented neural network hardly recovers with treatment. In this review article, we discussed possible future therapeutic strategies for Alzheimer-type dementia by increasing Aβ clearance from the early stage such as the prevention of Aβ-glycation and the promotion of glycated-Aβ degradation, which may be a paradigm shift.

Effects of the Cobalt-60 gamma radiation on Pichia pastoris glyceraldehyde-3-phosphate dehydrogenase

Purpose Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a key enzyme of the glycolytic pathway, can play a physiological regulatory role and vital other roles in metabolism. This study investigated the effects of gamma radiation generated by Cobalt-60 source on GAPDH activity and protein levels in Pichia pastoris as an eukaryotic organism model. Materials and methods After purification of the GAPDH from P. pastoris, in vitro effects of irradiation to the dose of 2 Gy, using Cobalt-60 at the dose rate of 0.25 Gy/min, on activity and kinetic parameters were investigated. In vivo effects of gamma exposition (dose of 5 Gy) on P. pastoris GAPDH and on reactive oxygen species (ROS) markers were also explored. Results and conclusions The in vitro irradiation of the purified GAPDH reduces the specific activity and the maximum velocity (V max) without alteration of substrates binding (K m). No changes occurred in the specific activity and in kinetic parameters when P. pastoris cells were exposed to Cobalt-60 source. However, this in vivo irradiation of cells produced a significant increase of the GAPDH protein level. The changes of GAPDH activity and the increase of the enzyme population as a target for gamma radiation exposure will play a role in cells adaptation under stress conditions. On the other hand, the increase of malondialdehyde and carbonyl contents and the enhancement of catalase and superoxide dismutase in irradiated cells have been noticed. The antioxidant system can play an important role in the protection of P. pastoris GAPDH against the gamma induced-ROS damage. This is the first report of the P. pastoris GAPDH as a physiological target of gamma exposition.

Glyceraldehyde-3-phosphate dehydrogenase and glutamine synthetase inhibition in the presence of pro-inflammatory cytokines contribute to the metabolic imbalance of diabetic retinopathy

Diabetic retinopathy (DR) is the leading cause of vision impairment in working age adults. In addition to hyperglycemia, retinal inflammation is an important driving factor for DR development. Although DR is clinically described as diabetes-induced damage to the retinal blood vessels, several studies have reported that metabolic dysregulation occurs in the retina prior to the development of microvascular damage. The two most commonly affected metabolic pathways in diabetic conditions are glycolysis and the glutamate pathway. We investigated the role of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and glutamine synthetase (GS) in an in-vitro model of DR incorporating high glucose and pro-inflammatory cytokines. We found that GAPDH and GS enzyme activity were not significantly affected in hyperglycemic conditions or after exposure to cytokines alone, but were significantly decreased in the DR model. This confirmed that pro-inflammatory cytokines IL-1β and TNFα enhance the hyperglycemic metabolic deficit. We further investigated metabolite and amino acid levels after specific pharmacological inhibition of GAPDH or GS in the absence/presence of pro-inflammatory cytokines. The results indicate that GAPDH inhibition increased glucose and addition of cytokines increased lactate and ATP levels and reduced glutamate levels. GS inhibition did not alter retinal metabolite levels but the addition of cytokines increased ATP levels and caused glutamate accumulation in Müller cells. We conclude that it is the action of pro-inflammatory cytokines concomitantly with the inhibition of the glycolytic or GS mediated glutamate recycling that contribute to metabolic dysregulation in DR. Therefore, in the absence of good glycemic control, therapeutic interventions aimed at regulating inflammation may prevent the onset of early metabolic imbalance in DR.

Effect of MG‐132 on myofibrillogenesis and the ubiquitination of GAPDH in quail myotubes

In the three-step myofibrillogenesis model, mature myofibrils are formed through two intermediate structures: premyofibrils and nascent myofibrils. We have recently reported that several inhibitors of the Ubiquitin Proteosome System, for example, MG-132, and DBeQ, reversibly block progression of nascent myofibrils to mature myofibrils. In this investigation, we studied the effects of MG132 and DBeQ on the expression of various myofibrillar proteins including actin, myosin light and heavy chains, tropomyosin, myomesin, and myosin binding protein-C in cultured embryonic quail myotubes by western blotting using two loading controls-α-tubulin and glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Surprisingly, we found that MG-132 affected the level of expression of GAPDH but DBeQ did not. Reverse transcription polymerase chain reaction (RT-PCR) and quantitative reverse transcription-PCR (qRT-PCR) showed no significant effect of MG-132 on GAPDH transcription. Two-dimensional (2D) western blot analyses with extracts of control and MG-132-treated cells using anti-ubiquitin antibody indicated that MG132-treated myotubes show a stronger emitter-coupled logic signal. However, Spot% and Spot volume calculations for all spots from both western blot film signals and matched Coomassie-stained 2D polyacrylamide gel electrophoresis showed that the intensity of staining in a spot of ~39 kDa protein is 3.5-fold lower in the gel of MG-132-treated extracts. Mass spectrometry analyses identified the ~39 kDa protein as quail GAPDH. Immunohistochemical analysis of fixed MG-132-treated myotubes with anti-GAPDH antibody showed extensive clump formation, which may be analogous to granule formation by stress response factors in MG132-treated cells. This is the first report on in vivo ubiquitination of GAPDH. This may be essential for the moonlighting (Jeffery, 1999) activity of GAPDH for tailoring stress in myotubes.