Influence of Oxidative Stress on Catalytic and Non-glycolytic Functions of Glyceraldehyde-3-phosphate Dehydrogenase

Role of Oxidative Stress in the Occurrence and Development of Cognitive Dysfunction in Patients with Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea syndrome (OSAS) causes recurrent apnea and intermittent hypoxia at night, leading to several complications such as cognitive dysfunction. However, the molecular mechanisms underlying cognitive dysfunction in OSAS are unclear, and oxidative stress mediated by intermittent hypoxia is an important mechanism. In addition, the improvement of cognitive dysfunction in patients with OSAS varies by different treatment regimens; among them, continuous positive airway pressure therapy (CPAP) is mostly recognized for improving cognitive dysfunction. In this review, we discuss the potential mechanisms of oxidative stress in OSAS, the common factors of affecting oxidative stress and the Links between oxidative stress and inflammation in OSAS, focusing on the potential links between oxidative stress and cognitive dysfunction in OSAS and the potential therapies for neurocognitive dysfunction in patients with OSAS mediated by oxidative stress. Therefore, further analysis on the relationship between oxidative stress and cognitive dysfunction in patients with OSAS will help to clarify the etiology and discover new treatment options, which will be of great significance for early clinical intervention.

Glyceraldehyde-3-phosphate dehydrogenase is involved in the pathogenesis of Alzheimer's disease

One of important characteristics of Alzheimer's disease is a persistent oxidative/nitrosative stress caused by pro-oxidant properties of amyloid-beta peptide (Aβ) and chronic inflammation in the brain. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is easily oxidized under oxidative stress. Numerous data indicate that oxidative modifications of GAPDH in vitro and in cell cultures stimulate GAPDH denaturation and aggregation, and the catalytic cysteine residue Cys152 is important for these processes. Both intracellular and extracellular GAPDH aggregates are toxic for the cells. Interaction of denatured GAPDH with soluble Aβ results in mixed insoluble aggregates with increased toxicity. The above-described properties of GAPDH (sensitivity to oxidation and propensity to form aggregates, including mixed aggregates with Aβ) determine its role in the pathogenesis of Alzheimer's disease.

Grape Seed Proanthocyanidin Extract Attenuates Cafeteria-Diet-Induced Liver Metabolic Disturbances in Rats: Influence of Photoperiod

This study investigated the influence of photoperiod (day length) on the efficacy of grape seed proanthocyanidin extract (GSPE) in mitigating metabolic disorders in obese rats fed a cafeteria diet. Rats were exposed to standard (L12), long (L18), or short (L6) photoperiods and treated with GSPE or vehicle. In the standard photoperiod, GSPE reduced body weight gain (50.5%), total cholesterol (37%), and triglycerides (34.8%), while increasing the expression of hepatic metabolic genes. In the long photoperiod, GSPE tended to decrease body weight gain, increased testosterone levels (68.3%), decreased liver weight (12.4%), and decreased reverse serum amino acids. In the short photoperiod, GSPE reduced glycemia (~10%) and lowered triglyceride levels (38.5%), with effects modified by diet. The standard photoperiod showed the greatest efficacy against metabolic syndrome-associated diseases. The study showed how day length affects GSPE's benefits and underscores considering biological rhythms in metabolic disease therapies.

Chemical proteomics approaches for protein post-translational modification studies

The diversity and dynamics of proteins play essential roles in maintaining the basic constructions and functions of cells. The abundance of functional proteins is regulated by the transcription and translation processes, while the alternative splicing enables the same gene to generate distinct protein isoforms of different lengths. Beyond the transcriptional and translational regulations, post-translational modifications (PTMs) are able to further expand the diversity and functional scope of proteins. PTMs have been shown to make significant changes in the surface charges, structures, activation states, and interactome of proteins. Due to the functional complexity, highly dynamic nature, and low presence percentage, the study of protein PTMs remains challenging. Here we summarize and discuss the major chemical biology tools and chemical proteomics approaches to enrich and investigate the protein PTM of interest.

Mechanism of inactivation of glyceraldehyde-3-phosphate dehydrogenase in the presence of methylglyoxal

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is known to be one of the targets of methylglyoxal (MGO), a metabolite of glycolysis that increased in diabetes. However, the mechanism of GAPDH inactivation in the presence of MGO is unclear. The purpose of the work was to study the reaction of GAPDH with MGO and to identify the products of the reaction. It was shown that incubation of recombinant human GAPDH with MGO leads to irreversible inactivation of the enzyme, which is accompanied by a decrease in SH-group content by approximately 3.3 per tetramer GAPDH. MALDI-TOF MS analysis showed that the modification of GAPDH with MGO results in the oxidation of the catalytic cysteine residues (Cys152) to form cysteine-sulfinic acid. In addition, 2 arginine residues (R80 and R234) were identified that react with MGO to form hydroimidazolones. Incubation of SH-SY5Y neuroblastoma cells with MGO resulted in the inactivation of GAPDH and inhibition of glycolysis. The mechanism of GAPDH oxidation in the presence of MGO suggests the participation of superoxide anion, which is formed during the reaction of amino groups with methylglyoxal. The role of GAPDH in protection against the damaging effect of ROS in cells in the case of inefficiency of MGO removal by the GSH-dependent glyoxalase system is discussed.

Regulation of hyperoxia-induced neonatal lung injury via post-translational cysteine redox modifications

Preterm infants and patients with lung disease often have excess fluid in the lungs and are frequently treated with oxygen, however long-term exposure to hyperoxia results in irreversible lung injury. Although the adverse effects of hyperoxia are mediated by reactive oxygen species, the full extent of the impact of hyperoxia on redox-dependent regulation in the lung is unclear. In this study, neonatal mice overexpressing the beta-subunit of the epithelial sodium channel (β-ENaC) encoded by Scnn1b and their wild type (WT; C57Bl6) littermates were utilized to study the pathogenesis of high fraction inspired oxygen (FiO2)-induced lung injury. Results showed that O2-induced lung injury in transgenic Scnn1b mice is attenuated following chronic O2 exposure. To test the hypothesis that reversible cysteine-redox-modifications of proteins play an important role in O2-induced lung injury, we performed proteome-wide profiling of protein S-glutathionylation (SSG) in both WT and Scnn1b overexpressing mice maintained at 21% O2 (normoxia) or FiO2 85% (hyperoxia) from birth to 11-15 days postnatal. Over 7700 unique Cys sites with SSG modifications were identified and quantified, covering more than 3000 proteins in the lung. In both mouse models, hyperoxia resulted in a significant alteration of the SSG levels of Cys sites belonging to a diverse range of proteins. In addition, substantial SSG changes were observed in the Scnn1b overexpressing mice exposed to hyperoxia, suggesting that ENaC plays a critically important role in cellular regulation. Hyperoxia-induced SSG changes were further supported by the results observed for thiol total oxidation, the overall level of reversible oxidation on protein cysteine residues. Differential analyses reveal that Scnn1b overexpression may protect against hyperoxia-induced lung injury via modulation of specific processes such as cell adhesion, blood coagulation, and proteolysis. This study provides a landscape view of protein oxidation in the lung and highlights the importance of redox regulation in O2-induced lung injury.

Proteomics reveal the protective effects of chlorogenic acid on Enterococcus faecium Q233 in a simulated pro-oxidant colonic environment

Certain phytochemicals have been found to promote the beneficial effects of probiotic bacteria although the molecular mechanisms of such interactions are poorly understood. The objective of the present study was to evaluate the impact of the exposure to 0.5 mM chlorogenic acid (CA) on the redox status and proteome of Enterococcus faecium isolated from cheese and challenged with 2.5 mM hydrogen peroxide (H₂O₂). The bacterium was incubated in anaerobic conditions for 48 h at 37 °C. CA exposure led to a more intense oxidative stress and accretion of bacterial protein carbonyls than those induced by H₂O₂. The oxidative damage to bacterial proteins was even more severe in the bacterium treated with both CA and H₂O₂, yet, such combination led to a strengthening of the antioxidant defenses, namely, a catalase-like activity. The proteomic study indicated that H₂O₂ caused a decrease in energy supply and the bacterium responded by reinforcing the membrane and wall structures and counteracting the redox and pH imbalance. CA stimulated the accretion of proteins related to translation and transcription regulators, and hydrolases. This phytochemical was able to counteract certain proteomic changes induced by H₂O₂ (i.e. increase of ATP binding cassete (ABC) transporter complex) and cause the increase of Rex, a redox-sensitive protein implicated in controlling metabolism and responses to oxidative stress. Although this protection should be confirmed under in vivo conditions, such effects point to benefits in animals or humans affected by disorders in which oxidative stress plays a major role.

Aflatoxin B1-activated heterophil extracellular traps result in the immunotoxicity to liver and kidney in chickens

Aflatoxin B1 (AFB1) is a mycotoxin with strong toxicity and play a large proportion in aspergillosis. Heterophil extracellular traps (HETs) was considered as an innate immune response of chickens to resist pathogens. AFB1 has been reported to trigger macrophages extracellular traps (METs) in THP-1 cells and RAW264.7 cells, but whether AFB1 could also activate HETs release, and the mechanism underlying AFB1-activated HETs in chicken remains unclear. In this study, we confirmed that AFB1could induce HETs release, which was a network of DNA-based structures consist of citrullinated histone 3 (citH3) and elastase. Meanwhile, AFB1-activated HETs rely on the glycolytic process to provide energy, NADPH oxidase and p38 signaling pathway. Moreover, it has been verified that AFB1-activated HETs release could significantly increase the biochemical indexes of liver (ALT and AST) and kidney (CRE and BUN) in serum. In addition, histopathological observation showed that AFB1 caused swelling, necrosis and vacuolation of hepatocytes in liver, and necrosis, exfoliated of nephrocyte in kidney. Further investigation demonstrated that AFB1 significantly decreased the levels of SOD and GSH-PX but increased the level of MDA, and meanwhile induced the mRNA expressions of TNF-α, IL-6 and IL-1β, iNOS, COX-2, NLRP3, caspase-1, caspase-3 and caspase-11. However, all these AFB1-induced biochemical indexes and histopathological changes were effectively alleviated by DNase I (the standard degradant for HETs). In conclusion, it has preliminary confirmed that AFB1-activated HETs formation contributed to the immunotoxicity in chicken and provide new strategies for the therapy in aspergillosis.

Dynamics of Reactive Carbonyl Species in Pea Root Nodules in Response to Polyethylene Glycol (PEG)-Induced Osmotic Stress

Drought dramatically affects crop productivity worldwide. For legumes this effect is especially pronounced, as their symbiotic association with rhizobia is highly-sensitive to dehydration. This might be attributed to the oxidative stress, which ultimately accompanies plants' response to water deficit. Indeed, enhanced formation of reactive oxygen species in root nodules might result in up-regulation of lipid peroxidation and overproduction of reactive carbonyl compounds (RCCs), which readily modify biomolecules and disrupt cell functions. Thus, the knowledge of the nodule carbonyl metabolome dynamics is critically important for understanding the drought-related losses of nitrogen fixation efficiency and plant productivity. Therefore, here we provide, to the best of our knowledge, for the first time a comprehensive overview of the pea root nodule carbonyl metabolome and address its alterations in response to polyethylene glycol-induced osmotic stress as the first step to examine the changes of RCC patterns in drought treated plants. RCCs were extracted from the nodules and derivatized with 7-(diethylamino)coumarin-3-carbohydrazide (CHH). The relative quantification of CHH-derivatives by liquid chromatography-high resolution mass spectrometry with a post-run correction for derivative stability revealed in total 194 features with intensities above 1 × 105 counts, 19 of which were down- and three were upregulated. The upregulation of glyceraldehyde could accompany non-enzymatic conversion of glyceraldehyde-3-phosphate to methylglyoxal. The accumulation of 4,5-dioxovaleric acid could be the reason for down-regulation of porphyrin metabolism, suppression of leghemoglobin synthesis, inhibition of nitrogenase and degradation of legume-rhizobial symbiosis in response to polyethylene glycol (PEG)-induced osmotic stress effect. This effect needs to be confirmed with soil-based drought models.

Sperm preparedness and adaptation to osmotic and pH stressors relate to functional competence of sperm in Bos taurus

The adaptive ability of sperm in the female reproductive tract micromilieu signifies the successful fertilization process. The study aimed to analyze the preparedness of sperm to the prevailing osmotic and pH stressors in the female reproductive tract. Fresh bovine sperm were incubated in 290 (isosmotic-control), 355 (hyperosmotic-uterus and oviduct), and 420 (hyperosmotic-control) mOsm/kg and each with pH of 6.8 (uterus) and 7.4 (oviduct). During incubation, the changes in sperm functional attributes were studied. Sperm kinematics and head area decreased significantly (p < 0.05) immediately upon exposure to hyperosmotic stress at both pH. Proportion of sperm capacitated (%) in 355 mOsm/kg at 1 and 2 h of incubation were significantly (p < 0.05) higher than those in 290 mOsm media. The magnitude and duration of recovery of sperm progressive motility in 355 mOsm with pH 7.4 was correlated with the ejaculate rejection rate (R² = 0.7). Using this information, the bulls were divided into good (n = 5) and poor (n = 5) osmo-adapters. The osmo-responsive genes such as NFAT5, HSP90AB1, SLC9C1, ADAM1B and GAPDH were upregulated (p < 0.05) in the sperm of good osmo-adapters. The study suggests that sperm are prepared for the osmotic and pH challenges in the female reproductive tract and the osmoadaptive ability is associated with ejaculate quality in bulls.

Modification of Glyceraldehyde-3-Phosphate Dehydrogenase with Nitric Oxide: Role in Signal Transduction and Development of Apoptosis

This review focuses on the consequences of GAPDH S-nitrosylation at the catalytic cysteine residue. The widespread hypothesis according to which S-nitrosylation causes a change in GAPDH structure and its subsequent binding to the Siah1 protein is considered in detail. It is assumed that the GAPDH complex with Siah1 is transported to the nucleus by carrier proteins, interacts with nuclear proteins, and induces apoptosis. However, there are several conflicting and unproven elements in this hypothesis. In particular, there is no direct confirmation of the interaction between the tetrameric GAPDH and Siah1 caused by S-nitrosylation of GAPDH. The question remains as to whether the translocation of GAPDH into the nucleus is caused by S-nitrosylation or by some other modification of the catalytic cysteine residue. The hypothesis of the induction of apoptosis by oxidation of GAPDH is considered. This oxidation leads to a release of the coenzyme NAD+ from the active center of GAPDH, followed by the dissociation of the tetramer into subunits, which move to the nucleus due to passive transport and induce apoptosis. In conclusion, the main tasks are summarized, the solutions to which will make it possible to more definitively establish the role of nitric oxide in the induction of apoptosis.

Products of S-nitrosylation of glyceraldehyde-3-phosphate dehydrogenase: Relation between S-nitrosylation and oxidation

BACKGROUND

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is one of the major targets of NO in cells, especially in neurodegenerative diseases. S-Nitrosylation of GAPDH is accompanied by its translocation into the nucleus with subsequent apoptosis. The product of GAPDH modification by NO is considered to be S-nitrosylated GAPDH (GAPDH-SNO). However, this has not been confirmed by direct methods.

METHODS

Products of GAPDH modification in the presence of the NO donor diethylamine NONOate were analyzed by MALDI- and ESI- mass spectrometry methods.

RESULTS

The adduct between GAPDH and dimedone was detected by MALDI-MS analysis after incubation of S-nitrosylated GAPDH with dimedone, which points to the formation of cysteine-sulfenic acid (GAPDH-SOH) in the protein. Analysis of the protein hydrolysate revealed the incorporation of dimedone into the catalytic residue Cys150. An additional peak that corresponded to GAPDH-SNO was detected by ESI-MS analysis in GAPDH after the incubation with the NO donor. The content of GAPDH-SNO and GAPDH-SOH in the modified GAPDH was evaluated by different approaches and constituted 2.3 and 0.7 mol per mol GAPDH, respectively. A small fraction of GAPDH was irreversibly inactivated after NO treatment, suggesting that a minor part of the products includes cysteine-sulfinic or cysteine-sulfonic acids.

CONCLUSIONS

The main products of GAPDH modification by NO are GAPDH-SNO and GAPDH-SOH that is presumably formed due to the hydrolysis of GAPDH-SNO.

GENERAL SIGNIFICANCE

The obtained results are important for understanding the molecular mechanism of redox regulation of cell functions and the role of GAPDH in the development of neurodegenerative disorders.

Glutathione in Protein Redox Modulation through S-Glutathionylation and S-Nitrosylation

S-glutathionylation and S-nitrosylation are reversible post-translational modifications on the cysteine thiol groups of proteins, which occur in cells under physiological conditions and oxidative/nitrosative stress both spontaneously and enzymatically. They are important for the regulation of the functional activity of proteins and intracellular processes. Connecting link and “switch” functions between S-glutathionylation and S-nitrosylation may be performed by GSNO, the generation of which depends on the GSH content, the GSH/GSSG ratio, and the cellular redox state. An important role in the regulation of these processes is played by Trx family enzymes (Trx, Grx, PDI), the activity of which is determined by the cellular redox status and depends on the GSH/GSSG ratio. In this review, we analyze data concerning the role of GSH/GSSG in the modulation of S-glutathionylation and S-nitrosylation and their relationship for the maintenance of cell viability.

Cysteine Oxidations in Mitochondrial Membrane Proteins: The Case of VDAC Isoforms in Mammals

Cysteine residues are reactive amino acids that can undergo several modifications driven by redox reagents. Mitochondria are the source of an abundant production of radical species, and it is surprising that such a large availability of highly reactive chemicals is compatible with viable and active organelles, needed for the cell functions. In this work, we review the results highlighting the modifications of cysteines in the most abundant proteins of the outer mitochondrial membrane (OMM), that is, the voltage-dependent anion selective channel (VDAC) isoforms. This interesting protein family carries several cysteines exposed to the oxidative intermembrane space (IMS). Through mass spectrometry (MS) analysis, cysteine posttranslational modifications (PTMs) were precisely determined, and it was discovered that such cysteines can be subject to several oxidization degrees, ranging from the disulfide bridge to the most oxidized, the sulfonic acid, one. The large spectra of VDAC cysteine oxidations, which is unique for OMM proteins, indicate that they have both a regulative function and a buffering capacity able to counteract excess of mitochondrial reactive oxygen species (ROS) load. The consequence of these peculiar cysteine PTMs is discussed.

Glyceraldehyde-3-phosphate Dehydrogenase is a Multifaceted Therapeutic Target

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a glycolytic enzyme whose role in cell metabolism and homeostasis is well defined, while its function in pathologic processes needs further elucidation. Depending on the cell context, GAPDH may bind a number of physiologically important proteins, control their function and correspondingly affect the cell’s fate. These interprotein interactions and post-translational modifications of GAPDH mediate its cytotoxic or cytoprotective functions in the manner of a Janus-like molecule. In this review, we discuss the functional features of the enzyme in cellular physiology and its possible involvement in human pathologies. In the last part of the article, we describe drugs that can be employed to modulate this enzyme’s function in some pathologic states.

Protein S-glutathionylation reactions as a global inhibitor of cell metabolism for the desensitization of hydrogen peroxide signals

The pathogenesis of many human diseases has been attributed to the over production of reactive oxygen species (ROS), particularly superoxide (O₂^●-) and hydrogen peroxide (H₂O₂), by-products of metabolism that are generated by the premature reaction of electrons with molecular oxygen (O₂) before they reach complex IV of the respiratory chain. To date, there are 32 known ROS generators in mammalian cells, 16 of which reside inside mitochondria. Importantly, although these ROS are deleterious at high levels, controlled and temporary bursts in H₂O₂ production is beneficial to mammalian cells. Mammalian cells use sophisticated systems to take advantage of the second messaging properties of H₂O₂. This includes controlling its availability using antioxidant systems and negative feedback loops that inhibit the genesis of ROS at sites of production. At its core, ROS production depends on fuel metabolism. Therefore, desensitizing H₂O₂ signals would also require the temporary inhibition of fuel combustion and fluxes through metabolic pathways that promote ROS production. Additionally, this would also demand the diversion of fuels and nutrients into pathways that generate NADPH and other molecules required to maintain cellular redox buffering capacity. Therefore, fuel selection and metabolic flux plays an integral role in dictating the strength and duration of cellular redox signals. In the present review I provide an updated view on the function of protein S-glutathionylation, a ubiquitous redox sensitive modification involving the formation of a disulfide between the small molecular antioxidant glutathione and a cysteine residue, in the regulation of cellular metabolism on a global scale. To date, these concepts have mostly been reviewed at the level of mitochondrial bioenergetics in the contexts of health and disease. Careful examination of the literature revealed that glutathionylation is a temporary inhibitor of most metabolic pathways including glycolysis, the Krebs cycle, oxidative phosphorylation, amino acid metabolism, and fatty acid combustion, resulting in the diversion of fuels towards NADPH-producing pathways and the inhibition of ROS production. Armed with this information, I propose that protein S-glutathionylation reactions desensitize H₂O₂ signals emanating from catabolic pathways using a three-pronged regulatory mechanism; 1) inhibition of metabolic flux through pathways that promote ROS production, 2) diversion of metabolites towards pathways that support antioxidant defenses, and 3) direct inhibition of ROS-generating enzymes.

S-glutathionylation of human glyceraldehyde-3-phosphate dehydrogenase and possible role of Cys152-Cys156 disulfide bridge in the active site of the protein

BACKGROUND

We previously showed that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is S-glutathionylated in the presence of H₂O₂ and GSH. S-glutathionylation was shown to result in the formation of a disulfide bridge in the active site of the protein. In the present work, the possible biological significance of the disulfide bridge was investigated.

METHODS

Human recombinant GAPDH with the mutation C156S (hGAPDH_C156S) was obtained to prevent the formation of the disulfide bridge. Properties of S-glutathionylated hGAPDH_C156S were studied in comparison with those of the wild-type protein hGAPDH.

RESULTS

S-glutathionylation of hGAPDH and hGAPDH_C156S results in the reversible inactivation of the proteins. In both cases, the modification results in corresponding mixed disulfides between the catalytic Cys152 and GSH. In the case of hGAPDH, the mixed disulfide breaks down yielding Cys152-Cys156 disulfide bridge in the active site. In hGAPDH_C156S, the mixed disulfide is stable. Differential scanning calorimetry method showed that S-glutathionylation leads to destabilization of hGAPDH molecule, but does not affect significantly hGAPDH_C156S. Reactivation of S-glutathionylated hGAPDH in the presence of GSH and glutaredoxin 1 is approximately two-fold more efficient compared to that of hGAPDH_C156S.

CONCLUSIONS

S-glutathionylation induces the formation of Cys152-Cys156 disulfide bond in the active site of hGAPDH, which results in structural changes of the protein molecule. Cys156 is important for reactivation of S-glutathionylated GAPDH by glutaredoxin 1.

GENERAL SIGNIFICANCE

The described mechanism may be important for interaction between GAPDH and other proteins and ligands, involved in cell signaling.

Inhibitors of Glyceraldehyde 3-Phosphate Dehydrogenase and Unexpected Effects of Its Reduced Activity

The review describes the use of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) inhibitors to study the enzyme and to suppress its activity in various cell types. The main problem of selective GAPDH inhibition is a highly conserved nature of the enzyme active site and, especially, Cys150 environment important for the catalytic action of cysteine sulfhydryl group. Numerous attempts to find specific inhibitors of sperm GAPDH and enzymes from Trypanosoma sp. and Mycobacterium tuberculosis that would not inhibit GAPDH of somatic mammalian cells have failed, which has pushed researchers to search for new ways to solve this problem. The sections of the review are devoted to the studies of GAPDH inactivation by reactive oxygen species, glutathione, and glycating agents. The final section discusses possible effects of GAPDH inhibition and inactivation on glycolysis and related metabolic pathways (pentose phosphate pathway, uncoupling of the glycolytic oxidation and phosphorylation, etc.).

Protein Interaction with Charged Macromolecules: From Model Polymers to Unfolded Proteins and Post-Translational Modifications

Interaction of proteins with charged macromolecules is involved in many processes in cells. Firstly, there are many naturally occurred charged polymers such as DNA and RNA, polyphosphates, sulfated glycosaminoglycans, etc., as well as pronouncedly charged proteins such as histones or actin. Electrostatic interactions are also important for "generic" proteins, which are not generally considered as polyanions or polycations. Finally, protein behavior can be altered due to post-translational modifications such as phosphorylation, sulfation, and glycation, which change a local charge of the protein region. Herein we review molecular modeling for the investigation of such interactions, from model polyanions and polycations to unfolded proteins. We will show that electrostatic interactions are ubiquitous, and molecular dynamics simulations provide an outstanding opportunity to look inside binding and reveal the contribution of electrostatic interactions. Since a molecular dynamics simulation is only a model, we will comprehensively consider its relationship with the experimental data.

Oxidatively modified glyceraldehyde-3-phosphate dehydrogenase in neurodegenerative processes and the role of low molecular weight compounds in counteracting its aggregation and nuclear translocation

A number of independent studies have shown the contribution of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in the pathogenesis of several neurodegenerative disorders. Indeed, GAPDH aggregates have been found in many post-mortem samples of brains of patients diagnosed with Alzheimer's and Parkinson disease. Currently, it is accepted that GAPDH-mediated cell death pathways in the neurodegenerative processes are associated with apoptosis caused by GAPDH nuclear translocation and excessive aggregation under oxidative stress conditions. Also the role of GAPDH in neurodegenerative diseases is linked to it directly binding to specific amyloidogenic proteins and petides such as β-amyloid precursor protein, β-amyloid peptide and tau protein in Alzheimer's disease, huntingtin in Huntington's disease and α-synuclein in Parkinson disease. One of the latest studies indicated that GAPDH aggregates significantly accelerate amyloidogenesis of the β-amyloid peptide, which implies that aggregates of GAPDH may act as a specific aggregation "seed" in vitro. Previous detailed studies revealed that the active-site cysteine (Cys152) of GAPDH plays an essential role in the oxidative stress-induced aggregation of GAPDH associated with cell death. Furthermore, oxidative modification of this cysteine residue initiates the translocation of the enzyme to the nucleus, subsequently leading to apoptosis. The crystallographic structure of GAPDH shows that the Cys152 residue is located close to the surface of the molecule in a hydrophilic environment, which means that it can react with low molecular weight compounds such as hydroxynonenal or piceatannol. Therefore, it is highly possible that GAPDH may serve as a target for small molecule compounds with the potential to slow down or prevent the progression of neurodegenerative disorders. Recently appearing new evidence has highlighted the significance of low molecular weight compounds in counteracting the oxidation of GAPDH and consequently its aggregation and other unfavourable pathological processes. Hence, this review aims to present all recent findings concerning molecules that are able to interact with GAPDH and counteract its aggregation and translocation to the nucleus.