Moonlighting glyceraldehyde-3-phosphate dehydrogenase: posttranslational modification, protein and nucleic acid interactions in normal cells and in human pathology

Integration of high-resolution mass spectrometry technology with molecular network analysis and systems biology techniques to elucidate the active ingredients and mechanisms of Shiduqing capsules

RATIONALE

Shiduqing Capsules, a well-known Chinese patent medicine, are widely used clinically for the treatment of pruritus. However, to date, there is a lack of research on its pharmacological substances and mechanisms of action.

METHODS

In the current study, the chemical components of Shiduqing Capsules were identified using UHPLC-QE-Orbitrap-MS technology. Molecular network analysis was employed to identify structurally similar compounds to the known chemical components. The potential molecular targets of the active ingredients were predicted using the SwissTargetPrediction website. The identified targets were further analyzed using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis through the DAVID database. Molecular docking was used to validate the network pharmacology results.

RESULTS

Ultimately, A total of 51 chemical components of Shiduqing Capsules were identified. Molecular network analysis identified 21 flavonoids and 13 terpenoids. The core targets of these ingredients include TP53, AKT1, and STAT3. GO and KEGG enrichment analysis revealed 1,371 different biological functions and 177 signaling pathways. Molecular docking confirmed the high affinity between multiple core active ingredients of Shiduqing Capsules and pruritus targets.

CONCLUSION

In conclusion, the effective ingredients of Shiduqing Capsules exert a multifaceted therapeutic effect on pruritus through multiple targets and pathways.

The gap gene of Rhizobium etli is required for both free life and symbiosis with common beans

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH or Gap) is a ubiquitous enzyme essential for carbon and energy metabolism in most organisms. Despite its primary role in sugar metabolism, GAPDH is recognized for its involvement in diverse cellular processes, being considered a paradigm among multifunctional/moonlighting proteins. Besides its canonical cytoplasmic location, GAPDH has been detected on cell surfaces or as a secreted protein in prokaryotes, yet little is known about its possible roles in plant symbiotic bacteria. Here we report that Rhizobium etli, a nitrogen-fixing symbiont of common beans, carries a single gap gene responsible for both GAPDH glycolytic and gluconeogenic activities. An active Gap protein is required throughout all stages of the symbiosis between R. etli and its host plant Phaseolus vulgaris. Both glycolytic and gluconeogenic Gap metabolic activities likely contribute to bacterial fitness during early and intermediate stages of the interaction, whereas GAPDH gluconeogenic activity seems critical for nodule invasion and nitrogen fixation. Although the R. etli Gap protein is secreted in a c-di-GMP related manner, no involvement of the R. etli gap gene in c-di-GMP related phenotypes, such as flocculation, biofilm formation or EPS production, was observed. Notably, the R. etli gap gene fully complemented a double gap1/gap2 mutant of Pseudomonas syringae for free life growth, albeit only partially in planta, suggesting potential specific roles for each type of Gap protein. Nevertheless, further research is required to unravel additional functions of the R. etli Gap protein beyond its essential metabolic roles.

Local glycolysis fuels actomyosin contraction during axonal retraction

In response to repulsive cues, axonal growth cones can quickly retract. This requires the prompt activity of contractile actomyosin, which is formed by the non-muscle myosin II (NMII) bound to actin filaments. NMII is a molecular motor that provides the necessary mechanical force at the expense of ATP. Here, we report that this process is energetically coupled to glycolysis and is independent of cellular ATP levels. Induction of axonal retraction requires simultaneous generation of ATP by glycolysis, as shown by chemical inhibition and genetic knock-down of GAPDH. Co-immunoprecipitation and proximal-ligation assay showed that actomyosin associates with ATP-generating glycolytic enzymes and that this association is strongly enhanced during retraction. Using microfluidics, we confirmed that the energetic coupling between glycolysis and actomyosin necessary for axonal retraction is localized to the growth cone and near axonal shaft. These results indicate a tight coupling between on-demand energy production by glycolysis and energy consumption by actomyosin contraction suggesting a function of glycolysis in axonal guidance.

'Candidatus Liberibacter asiaticus' secretory protein SDE3 inhibits host autophagy to promote Huanglongbing disease in citrus

Antimicrobial acroautophagy/autophagy plays a vital role in degrading intracellular pathogens or microbial molecules in host-microbe interactions. However, microbes evolved various mechanisms to hijack or modulate autophagy to escape elimination. Vector-transmitted phloem-limited bacteria, Candidatus Liberibacter (Ca. Liberibacter) species, cause Huanglongbing (HLB), one of the most catastrophic citrus diseases worldwide, yet contributions of autophagy to HLB disease proliferation remain poorly defined. Here, we report the identification of a virulence effector in "Ca. Liberibacter asiaticus" (Las), SDE3, which is highly conserved among the "Ca. Liberibacter". SDE3 expression not only promotes the disease development of HLB and canker in sweet orange (Citrus sinensis) plants but also facilitates Phytophthora and viral infections in Arabidopsis, and Nicotiana benthamiana (N. benthamiana). SDE3 directly associates with citrus cytosolic glyceraldehyde-3-phosphate dehydrogenases (CsGAPCs), which negatively regulates plant immunity. Overexpression of CsGAPCs and SDE3 significantly inhibits autophagy in citrus, Arabidopsis, and N. benthamiana. Intriguingly, SDE3 undermines autophagy-mediated immunity by the specific degradation of CsATG8 family proteins in a CsGAPC1-dependent manner. CsATG8 degradation is largely rescued by treatment with an inhibitor of the late autophagic pathway, E64d. Furthermore, ectopic expression of CsATG8s enhances Phytophthora resistance. Collectively, these results suggest that SDE3-CsGAPC interactions modulate CsATG8-mediated autophagy to enhance Las progression in citrus.Abbreviations: ACP: asian citrus psyllid; ACD2: ACCELERATED CELL DEATH 2; ATG: autophagy related; Ca. Liberibacter: Candidatus Liberibacter; CaMV: cauliflower mosaic virus; CMV: cucumber mosaic virus; Cs: Citrus sinensis; EV: empty vector; GAPC: cytosolic glyceraldehyde-3-phosphate dehydrogenase; HLB: huanglongbing; H2O2: hydrogen peroxide; Las: liberibacter asiaticus; Laf: liberibacter africanus; Lam: liberibacter americanus; Pst: Pseudomonas syringae pv. tomato; PVX: potato virus X; ROS: reactive oxygen species; SDE3: sec-delivered effector 3; TEM: transmission electron microscopy; VIVE : virus-induced virulence effector; WT: wild-type; Xcc: Xanthomonas citri subsp. citri.

Rab2 stimulates LC3 lipidation on secretory membranes by noncanonical autophagy

The Golgi complex is a highly dynamic organelle that regulates various cellular activities and yet maintains a distinct structure. Multiple proteins participate in Golgi structure/organization including the small GTPase Rab2. Rab2 is found on the cis/medial Golgi compartments and the endoplasmic reticulum-Golgi intermediate compartment. Interestingly, Rab2 gene amplification occurs in a wide range of human cancers and Golgi morphological alterations are associated with cellular transformation. To learn how Rab2 'gain of function' influences the structure/activity of membrane compartments in the early secretory pathway that may contribute to oncogenesis, NRK cells were transfected with Rab2B cDNA. We found that Rab2B overexpression had a dramatic effect on the morphology of pre- and early Golgi compartments that resulted in a decreased transport rate of VSV-G in the early secretory pathway. We monitored the cells for the autophagic marker protein LC3 based on the findings that depressed membrane trafficking affects homeostasis. Morphological and biochemical studies confirmed that Rab2 ectopic expression stimulated LC3-lipidation on Rab2-containing membranes that was dependent on GAPDH and utilized a non-canonical LC3-conjugation mechanism that is nondegradative. Golgi structural alterations are associated with changes in Golgi-associated signalling pathways. Indeed, Rab2 overexpressing cells had elevated Src activity. We propose that increased Rab2 expression facilitates cis Golgi structural changes that are maintained and tolerated by the cell due to LC3 tagging, and subsequent membrane remodeling triggers Golgi associated signaling pathways that may contribute to oncogenesis.

Origin of Elevated S-Glutathionylated GAPDH in Chronic Neurodegenerative Diseases

H2O2-oxidized glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalytic cysteine residues (Cc(SH) undergo rapid S-glutathionylation. Restoration of the enzyme activity is accomplished by thiol/disulfide SN2 displacement (directly or enzymatically) forming glutathione disulfide (G(SS)G) and active enzyme, a process that should be facile as Cc(SH) reside on the subunit surface. As S-glutathionylated GAPDH accumulates following ischemic and/or oxidative stress, in vitro/silico approaches have been employed to address this paradox. Cc(SH) residues were selectively oxidized and S-glutathionylated. Kinetics of GAPDH dehydrogenase recovery demonstrated that glutathione is an ineffective reactivator of S-glutathionylated GAPDH compared to dithiothreitol. Molecular dynamic simulations (MDS) demonstrated strong binding interactions between local residues and S-glutathione. A second glutathione was accommodated for thiol/disulfide exchange forming a tightly bound glutathione disulfide G(SS)G. The proximal sulfur centers of G(SS)G and Cc(SH) remained within covalent bonding distance for thiol/disulfide exchange resonance. Both these factors predict inhibition of dissociation of G(SS)G, which was verified by biochemical analysis. MDS also revealed that both S-glutathionylation and bound G(SS)G significantly perturbed subunit secondary structure particularly within the S-loop, region which interacts with other cellular proteins and mediates NAD(P)+ binding specificity. Our data provides a molecular rationale for how oxidative stress elevates S-glutathionylated GAPDH in neurodegenerative diseases and implicates novel targets for therapeutic intervention.

Protein Interactome of Amyloid-β as a Therapeutic Target

The amyloid concept of Alzheimer's disease (AD) assumes the β-amyloid peptide (Aβ) as the main pathogenic factor, which injures neural and other brain cells, causing their malfunction and death. Although Aβ has been documented to exert its cytotoxic effect in a solitary manner, there is much evidence to claim that its toxicity can be modulated by other proteins. The list of such Aβ co-factors or interactors includes tau, APOE, transthyretin, and others. These molecules interact with the peptide and affect the ability of Aβ to form oligomers or aggregates, modulating its toxicity. Thus, the list of potential substances able to reduce the harmful effects of the peptide should include ones that can prevent the pathogenic interactions by specifically binding Aβ and/or its partners. In the present review, we discuss the data on Aβ-based complexes in AD pathogenesis and on the compounds directly targeting Aβ or the destructors of its complexes with other polypeptides.

Immunomodulatory effects of extracellular glyceraldehyde 3-phosphate dehydrogenase of exopolysaccharide-producing Lactiplantibacillus plantarum JCM 1149

Probiotic lactic acid bacteria evoke immunomodulatory effects in the host; however, the reasons for the different effects of various species and strains remain to be elucidated. To clarify the critical immunomodulatory components and impact of exopolysaccharide (EPS) in Lactiplantibacillus plantarum, 11 types of L. plantarum strains were compared for the production of EPS, inflammatory cytokines, interleukin-6 and -12, and the anti-inflammatory cytokine, interleukin-10, from THP-1 differentiated dendritic cells. EPS in the fermented medium correlated with cytokine-inducing activities. L. plantarum JCM 1149, with the highest production of EPS, also induced interleukin-6, -10, and -12 among the 11 tested strains. Notably, the cytokine-producing activities overlapped with the protein fraction in gel filtration chromatography but not with EPS, which has been reported to exert immunomodulatory effects. The 41 kDa protein that coexisted with EPS was purified as a major active component and identified as glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a known moonlighting protein. GAPDH secretion was reduced when EPS synthesis inhibitors were added to the culture medium. RNA sequencing of GAPDH-treated THP-1 cells revealed an up-regulation in the expression of genes involved in transcriptional regulation, cell surface receptor signalling, immune response, and matrix components. Here, we report, to our knowledge for the first time, that the cell surface-associated L. plantarum GAPDH plays a crucial role in cytokine production in THP-1 cells, but EPS with less activity may help GAPDH secretion.

Defining the S-Glutathionylation Proteome by Biochemical and Mass Spectrometric Approaches

Protein S-glutathionylation (SSG) is a reversible post-translational modification (PTM) featuring the conjugation of glutathione to a protein cysteine thiol. SSG can alter protein structure, activity, subcellular localization, and interaction with small molecules and other proteins. Thus, it plays a critical role in redox signaling and regulation in various physiological activities and pathological events. In this review, we summarize current biochemical and analytical approaches for characterizing SSG at both the proteome level and at individual protein levels. To illustrate the mechanism underlying SSG-mediated redox regulation, we highlight recent examples of functional and structural consequences of SSG modifications. Finally, we discuss the analytical challenges in characterizing SSG and the thiol PTM landscape, future directions for understanding of the role of SSG in redox signaling and regulation and its interplay with other PTMs, and the potential role of computational approaches to accelerate functional discovery.

Glyceraldehyde-3-phosphate dehydrogenase affects the growth of Schistosoma japonicum schistosomula

This study was conducted to evaluate the effect of glyceraldehyde-3-phosphate dehydrogenase from Schistosoma japonicum (SjGAPDH) on the growth of schistosomula. Quantitative reverse transcription PCR and immunohistochemical analysis were performed to analyze the mRNA levels and immune localization of SjGAPDH. RNA interference experiments were conducted to further examine the role of SjGAPDH in the schistosomula growth of S. japonicum. The results demonstrated that SjGAPDH mRNA was expressed during all stages of S. japonicum development, with its expression gradually increasing over time. SjGAPDH was mainly distributed on the surface and in some parenchymal cells of S. japonicum. Double-stranded RNA-mediated GAPDH knockdown reduced SjGAPDH expression by approximately 59%. Light microscopic observations revealed that the size, length, width, volume, and area of schistosomula in the SjGAPDH interference group were significantly lower than those in the enhanced green fluorescent protein control group. These findings indicate that SjGAPDH may affect the growth of S. japonicum schistosomula and could be a useful target for treating schistosomiasis.

Mechanism of GAPDH Redox Signaling by H2O2 Activation of a Two-Cysteine Switch

Oxidation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by reactive oxygen species such as H2O2 activate pleiotropic signaling pathways is associated with pathophysiological cell fate decisions. Oxidized GAPDH binds chaperone proteins with translocation of the complex to the nucleus and mitochondria initiating autophagy and cellular apoptosis. In this study, we establish the mechanism by which H2O2-oxidized GAPDH subunits undergo a subunit conformational rearrangement. H2O2 oxidizes both the catalytic cysteine and a vicinal cysteine (four residues downstream) to their respective sulfenic acids. A 'two-cysteine switch' is activated, whereby the sulfenic acids irreversibly condense to an intrachain thiosulfinic ester resulting in a major metastable subunit conformational rearrangement. All four subunits of the homotetramer are uniformly and independently oxidized by H2O2, and the oxidized homotetramer is stabilized at low temperatures. Over time, subunits unfold forming disulfide-linked aggregates with the catalytic cysteine oxidized to a sulfinic acid, resulting from thiosulfinic ester hydrolysis via the highly reactive thiosulfonic ester intermediate. Molecular Dynamic Simulations provide additional mechanistic insights linking GAPDH subunit oxidation with generating a putative signaling conformer. The low-temperature stability of the H2O2-oxidized subunit conformer provides an operable framework to study mechanisms associated with gain-of-function activities of oxidized GAPDH to identify novel targets for the treatment of neurodegenerative diseases.

Molecular characterization of glyceraldehyde-3-phosphate dehydrogenase from Eimeria tenella

Chicken coccidiosis is an extremely common and lethally epidemic disease caused by Eimeria spp. The control measures of coccidiosis depend mainly on drugs. However, the ensuing drug resistance problem has brought considerable economic loss to the poultry industry. In our previous study, comparative transcriptome analyses of a drug-sensitive (DS) strain and two drug-resistant strains (diclazuril-resistant (DZR) and maduramicin-resistant (MRR) strains) of Eimeria tenella were carried out by transcriptome sequencing. The expression of glyceraldehyde-3-phosphate dehydrogenase of E. tenella (EtGAPDH) was upregulated in the two resistant strains. In this study, we cloned and characterized EtGAPDH. Indirect immunofluorescence localization was used to observe the distribution of EtGAPDH in E. tenella. The results showed that the protein was distributed mainly on the surface of sporozoites and merozoites, and in the cytoplasm of merozoites. qPCR was performed to detect the transcription level of EtGAPDH in the different developmental stages of the E. tenella DS strain. The transcription level of EtGAPDH was significantly higher in second-generation merozoites than in the other three stages. The transcription level of EtGAPDH in the different drug-resistant strains and DS strain of E. tenella was also analyzed by qPCR. The results showed that the transcription level was significantly higher in the two drug-resistant strains (MRR and DZR) than in the DS strain. As the concentration of diclazuril and maduramicin increased, the transcription levels also increased. Western blot results showed that EtGAPDH protein was upregulated in the DZR and MRR strains. Enzyme activity showed that the enzyme activity of EtGAPDH was higher in the two resistant strains than in the DS strain. These results showed that EtGAPDH possess several roles that separate and distinct from its glycolytic function and maybe involved in the development of E. tenella resistance to anticoccidial drugs.

ACTB and GAPDH appear at multiple SDS-PAGE positions, thus not suitable as reference genes for determining protein loading in techniques like Western blotting

We performed polyacrylamide gel electrophoresis of human proteins with sodium dodecyl sulfate, isolated proteins at multiple positions, and then used liquid chromatography and tandem mass spectrometry (LC-MS/MS) to determine the protein identities. Although beta-actin (ACTB) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) are 41.7 and 36 kDa proteins, respectively, LC-MS/MS identified their peptides at all the positions studied. The National Center for Biotechnology Information (USA) database lists only one ACTB mRNA but five GAPDH mRNAs and one noncoding RNA. The five GAPDH mRNAs encode three protein isoforms, while our bioinformatics analysis identified a 17.6 kDa isoform encoded by the noncoding RNA. All LC-MS/MS-identified GAPDH peptides at all positions studied are unique, but some of the identified ACTB peptides are shared by ACTC1, ACTBL2, POTEF, POTEE, POTEI, and POTEJ. ACTC1 and ACTBL2 belong to the ACT family with significant similarities to ACTB in protein sequence, whereas the four POTEs are ACTB-containing chimeric genes with the C-terminus of their proteins highly similar to the ACTB. These data lead us to conclude that GAPDH and ACTB are poor reference genes for determining the protein loading in such techniques as Western blotting, a leading role these two genes have been playing for decades in biomedical research.

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.

Glyceraldehyde-3-phosphate dehydrogenase present in extracellular vesicles from Leishmania major suppresses host TNF-alpha expression

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) fulfills various physiological roles that are unrelated to its glycolytic function. However, to date, the nonglycolytic function of GAPDH in trypanosomal parasites is absent from the literature. Exosomes secreted from Leishmania, like entire parasites, were found to have a significant impact on macrophage cell signaling and function, indicating cross talk with the host immune system. In this study, we demonstrate that the Leishmania GAPDH (LmGAPDH) protein is highly enriched within the extracellular vesicles (EVs) secreted during infection. To understand the function of LmGAPDH in EVs, we generated control, overexpressed, half-knockout (HKO), and complement cell lines. HKO cells displayed lower virulence compared with control cells when macrophages and BALB/c mice were infected with them, implying a crucial role for LmGAPDH in Leishmania infection and disease progression. Furthermore, upon infection of macrophages with HKO mutant Leishmania and its EVs, despite no differences in TNFA mRNA expression, there was a considerable increase in TNF-α protein expression compared with control, overexpressed, and complement parasites as determined by ELISA, RT-PCR, and immunoblot data. In vitro protein translation studies suggest that LmGAPDH-mediated TNF-α suppression occurs in a concentration-dependent manner. Moreover, mRNA binding assays also verified that LmGAPDH binds to the AU-rich 3′-UTR region of TNFA mRNA, limiting its production. Together, these findings confirmed that the LmGAPDH contained in EVs inhibits TNF-α expression in macrophages during infection via posttranscriptional repression.

The moonlighting activities of dihydrolipoamide dehydrogenase: Biotechnological and biomedical applications

Dihydrolipoamide dehydrogenase (DLDH) is a homodimeric flavin-dependent enzyme that catalyzes the NAD⁺ -dependent oxidation of dihydrolipoamide. The enzyme is part of several multi-enzyme complexes such as the Pyruvate Dehydrogenase system that transforms pyruvate into acetyl-co-A. Concomitantly with its redox activity, DLDH produces Reactive Oxygen Species (ROS), which are involved in cellular apoptotic processes. DLDH possesses several moonlighting functions. One of these is the capacity to adhere to metal-oxides surfaces. This was first exemplified by the presence of an exocellular form of the enzyme on the cell-wall surface of Rhodococcus ruber. This capability was evolutionarily conserved and identified in the human, mitochondrial, DLDH. The enzyme was modified with Arg-Gly-Asp (RGD) groups, which enabled its interaction with integrin-rich cancer cells followed by "integrin-assisted-endocytosis." This allowed harnessing the enzyme for cancer therapy. Combining the TiO₂ -binding property with DLDH's ROS-production, enabled us to develop several medical applications including improving oesseointegration of TiO₂ -based implants and photodynamic treatment for melanoma. The TiO₂ -binding sites of both the bacterial and human DLDH's were identified on the proteins' molecules at regions that overlap with the binding site of E3-binding protein (E3BP). This protein is essential in forming the multiunit structure of PDC. Another moonlighting activity of DLDH, which is described in this Review, is its DNA-binding capacity that may affect DNA chelation and shredding leading to apoptotic processes in living cells. The typical ROS-generation by DLDH, which occurs in association with its enzymatic activity and its implications in cancer and apoptotic cell death are also discussed.

Redox-Oligomeric State of Peroxiredoxin-2 and Glyceraldehyde-3-Phosphate Dehydrogenase in Obstructive Sleep Apnea Red Blood Cells under Positive Airway Pressure Therapy

In this study, we examined the effect of six months of positive airway pressure (PAP) therapy on Obstructive Sleep Apnea (OSA) red blood cell (RBC) proteome by two dimensional difference gel electrophoresis (2D-DIGE) - based proteomics followed by Western blotting (WB) validation. The discovered dysregulated proteins/proteoforms are associated with cell death, H2O2 catabolic/metabolic process, stress response, and protein oligomerization. Validation by nonreducing WB was performed for peroxiredoxin-2 (PRDX2) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by using antibodies against the sulfinylated/sulfonylated cysteine of these proteins to better evaluate their redox-oligomeric states under OSA and/or in response to PAP therapy. The results indicated that the redox-oligomeric state of GAPDH and PRDX2 involving overoxidation by sulfinic/sulfonic acids were differentially modulated in OSA RBC, which might be compromising RBC homeostasis. PAP therapy by restoring this modulation induced a higher oligomerization of overoxidized GAPDH and PRDX2 in some patients that could be associated with eryptosis and the chaperone "gain" of function, respectively. This varied response following PAP may result from the complex interplay between OSA and OSA metabolic comorbidity. Hence, information on the redox status of PRDX2 and GAPDH in RBC will help to better recognize OSA subtypes and predict the therapeutic response in these patients. GAPDH monomer combined with body mass index (BMI) and PRDX2 S-S dimer combined with homeostatic model assessment for insulin resistance (HOMA-IR) showed to be very promising biomarkers to predict OSA and OSA severity, respectively.