Evidence for dual targeting control of Arabidopsis 6-phosphogluconate dehydrogenase isoforms by N-terminal phosphorylation.

The oxidative pentose-phosphate pathway (OPPP) retrieves NADPH from glucose-6-phosphate, which is important in chloroplasts at night and in plastids of heterotrophic tissues. We previously studied how OPPP enzymes may transiently locate to peroxisomes, but how this is achieved for the third enzyme remained unclear. By extending our genetic approach, we demonstrated that Arabidopsis isoform 6-phosphogluconate dehydrogenase 2 (PGD2) is indispensable in peroxisomes during fertilization, and investigated why all PGD-reporter fusions show a mostly cytosolic pattern. A previously published interaction of a plant PGD with thioredoxin m was confirmed using Trxm2 for yeast two-hybrid (Y2H) and bimolecular fluorescent complementation (BiFC) assays, and medial reporter fusions (with both ends accessible) proved to be beneficial for studying peroxisomal targeting of PGD2. Of special importance were phosphomimetic changes at Thr6, resulting in a clear targeting switch to peroxisomes, while a similar change at position Ser7 in PGD1 conferred plastid import. Apparently, efficient subcellular localization can be achieved by activating an unknown kinase, either early after or during translation. N-terminal phosphorylation of PGD2 interfered with dimerization in the cytosol, thus allowing accessibility of the C-terminal peroxisomal targeting signal (PTS1). Notably, we identified amino acid positions that are conserved among plant PGD homologues, with PTS1 motifs first appearing in ferns, suggesting a functional link to fertilization during the evolution of seed plants.

Inhibition of 6-Phosphogluconate Dehydrogenase Reverses Epirubicin Resistance Through Metabolic Reprograming in Triple-Negative Breast Cancer Cells.

At present, chemotherapy is the most effective strategy for treating triple-negative breast cancer (TNBC), but its efficacy was limited by the development of chemo-resistance. The exact mechanism of chemoresistance still remains unclear. This study aims to examine whether 6-phosphogluconate dehydrogenase (6PGD), a key enzyme in the oxidative pentose phosphate pathway (PPP), could promote the resistance of TNBC cells to epirubicin. A TNBC epirubicin-resistant cell line was developed by increasing concentration and the effectiveness was tested. The expression and knockdown efficiency of 6PGD were further validated by performing quantitative real-time PCR (qPCR) and Western blot. The effects of 6PGD on parental and drug-resistant TNBC cell lines were verified based on proliferation and apoptosis experiments. Finally, nicotinamide adenine dinucleotide phosphate (NADPH) and lactate quantitative experiments were performed to examine the mechanism of 6PGD in promoting drug resistance. Epirubicin-resistant cancer cells exhibited a higher level of 6PGD in contrast to epirubicin-sensitive cells. In addition, 6PGD inhibited by genetic and pharmacological approaches significantly suppressed the growth and survival of both epirubicin-sensitive and epirubicin-resisteant TNBC cells. It should be noted that 6PGD inhibition sensitized epirubicin-resistant TNBC cells to epirubicin treatment. Moreover, it was also found that the levels of NADPH and lactate increased in epirubicin-resistant TNBC cells but decreased in response to 6PGD inhibition. The present results indicated that 6PGD inhibition disrupted metabolic reprogramming in epirubicin-resistant TNBC cells. Our work demonstrated that 6PGD inhibition reversed the resistance of TNBC cells to epirubicin, providing an alternative therapeutic choice to tackle the challenge of epirubicin resistance in TNBC treatment.

Critical Role of 6-Phosphogluconate Dehydrogenase in TAp73-Mediated Cancer Cell Proliferation.

Cancer cells frequently alter their metabolism to support biogenesis and proliferation and survive specific metabolic stressors. The glucose-associated pentose phosphate pathway (PPP) is crucial for cancer cell proliferation. In particular, 6-phosphogluconate dehydrogenase (6PGD), the second dehydrogenase in the PPP, catalyzes the decarboxylation of 6-phosphogluconate into ribulose 5-phosphate (Ru5P). However, the mechanisms controlling 6PGD expression in cancer cells remain unclear. Herein, we show that TAp73 increases Ru5P and NADPH production through 6PGD activation to counteract reactive oxygen species and protects cells from apoptosis. Moreover, 6PGD overexpression rescues the proliferation and tumorigenic ability of TAp73-deficient cells. These findings further establish the critical role of TAp73 on glucose metabolism regulation, demonstrating that TAp73 can activate 6PGD expression to support oncogenic cell growth. IMPLICATIONS: By transcriptional upregulation of 6PGD, TAp73 promotes the generation of Ru5P and NADPH, and enhances tumor cell proliferation.

6-Phosphogluconate dehydrogenase and its crystal structures.

6-Phosphogluconate dehydrogenase (6PGDH; EC 1.1.1.44) catalyses the oxidative decarboxylation of 6-phosphogluconate to ribulose 5-phosphate in the context of the oxidative part of the pentose phosphate pathway. Depending on the species, it can be a homodimer or a homotetramer. Oligomerization plays a functional role not only because the active site is at the interface between subunits but also due to the interlocking tail-modulating activity, similar to that of isocitrate dehydrogenase and malic enzyme, which catalyse a similar type of reaction. Since the pioneering crystal structure of sheep liver 6PGDH, which allowed motifs common to the ß-hydroxyacid dehydrogenase superfamily to be recognized, several other 6PGDH crystal structures have been solved, including those of ternary complexes. These showed that more than one conformation exists, as had been suggested for many years from enzyme studies in solution. It is inferred that an asymmetrical conformation with a rearrangement of one of the two subunits underlies the homotropic cooperativity. There has been particular interest in the presence or absence of sulfate during crystallization. This might be related to the fact that this ion, which is a competitive inhibitor that binds in the active site, can induce the same 6PGDH configuration as in the complexes with physiological ligands. Mutagenesis, inhibitors, kinetic and binding studies, post-translational modifications and research on the enzyme in cancer cells have been complementary to the crystallographic studies. Computational modelling and new structural studies will probably help to refine the understanding of the functioning of this enzyme, which represents a promising therapeutic target in immunity, cancer and infective diseases. 6PGDH also has applied-science potential as a biosensor or a biobattery. To this end, the enzyme has been efficiently immobilized on specific polymers and nanoparticles. This review spans the 6PGDH literature and all of the 6PGDH crystal structure data files held by the Protein Data Bank.

6-Phosphogluconate dehydrogenase (6PGD), a key checkpoint in reprogramming of regulatory T cells metabolism and function.

Cellular metabolism has key roles in T cells differentiation and function. CD4+ T helper-1 (Th1), Th2, and Th17 subsets are highly glycolytic while regulatory T cells (Tregs) use glucose during expansion but rely on fatty acid oxidation for function. Upon uptake, glucose can enter pentose phosphate pathway (PPP) or be used in glycolysis. Here, we showed that blocking 6-phosphogluconate dehydrogenase (6PGD) in the oxidative PPP resulted in substantial reduction of Tregs suppressive function and shifts toward Th1, Th2, and Th17 phenotypes which led to the development of fetal inflammatory disorder in mice model. These in turn improved anti-tumor responses and worsened the outcomes of colitis model. Metabolically, 6PGD blocked Tregs showed improved glycolysis and enhanced non-oxidative PPP to support nucleotide biosynthesis. These results uncover critical role of 6PGD in modulating Tregs plasticity and function, which qualifies it as a novel metabolic checkpoint for immunotherapy applications.

Biochemical and structural insights into 6-phosphogluconate dehydrogenase from Leishmania donovani.

6-phosphogluconate dehydrogenase (6PGDH) participates in pentose phosphate pathway of glucose metabolism by catalyzing oxidative decarboxylation of 6-phsophogluconate (6PG) and its absence has been lethal for several eukaryotes. Despite being a validated drug target in many organisms like Plasmodium, the enzyme has not been explored in leishmanial parasites. In the present study, 6PGDH of Leishmania donovani (Ld6PGDH) is cloned and purified followed by its characterization using biochemical and structural approaches. Ld6PGDH lacks the glycine-serine-rich sequence at its C-terminal that is present in other eukaryotes including humans. Leishmanial 6PGDH possesses more affinity for substrate (6PG) and cofactor (NADP) in comparison to that of human. The enzymatic activity is inhibited by gentamicin and cefuroxime through competitive mode with functioning more potently towards leishmanial 6PGDH than its human counterpart. CD analysis has shown higher α-helical content in the secondary structure of Ld6PGDH, while fluorescence studies revealed that tryptophan residues are not completely accessible to solvent environment. The three-dimensional structure was generated through homology modelling and docked with substrate and cofactor. The docking studies demonstrated two separate binding pockets for 6PG and NADP with higher affinity for the cofactor binding, and Asn105 is interacting with substrate as well as the cofactor. Additionally, MD simulation has shown complexes of Ld6PGDH with 6PG and NADP to be more stable than its apo form. Altogether, the present study might provide the foundation to investigate this enzyme as potential target against leishmaniasis. KEY POINTS: • Ld6PGDH enzymatic activity is competitively inhibited by gentamicin and cefuroxime. • It displays more helical contents and all structural characteristics of 6PGDH family. • Interaction studies demonstrate higher affinity of cofactor than substrate for Ld6PGDH.

Cloning, purification, and characterization of the 6-phosphogluconate dehydrogenase (6 PGDH) from Giardia lamblia.

Giardia lamblia, due to the habitat in which it develops, requires a continuous supply of intermediate compounds that allow it to survive in the host. The pentose phosphate pathway (PPP) provides essential molecules such as NADPH and ribulose-5-phosphate during the oxidative phase of the pathway. One of the key enzymes during this stage is 6-phosphogluconate dehydrogenase (6 PGDH) for generating NADPH. Given the relevance of the enzyme, in the present work, the 6pgdh gene from G. lamblia was amplified and cloned to produce the recombinant protein (Gl-6 PGDH) and characterize it functionally and structurally after the purification of Gl-6 PGDH by affinity chromatography. The results of the characterization showed that the protein has a molecular mass of 54 kDa, with an optimal pH of 7.0 and a temperature of 36-42 °C. The kinetic parameters of Gl-6 PGDH were Km = 49.2 and 139.9 µM (for NADP+ and 6-PG, respectively), Vmax =26.27 µmol*min-1*mg-1, and Kcat = 24.0 s-1. Finally, computational modeling studies were performed to obtain a structural visualization of the Gl-6 PGDH protein. The generation of the model and the characterization assays will allow us to expand our knowledge for future studies of the function of the protein in the metabolism of the parasite.

Blockade of 6-phosphogluconate dehydrogenase generates CD8+ effector T cells with enhanced anti-tumor function.

Although T cell expansion depends on glycolysis, T effector cell differentiation requires signaling via the production of reactive oxygen species (ROS). Because the pentose phosphate pathway (PPP) regulates ROS by generating nicotinamide adenine dinucleotide phosphate (NADPH), we examined how PPP blockade affects T cell differentiation and function. Here, we show that genetic ablation or pharmacologic inhibition of the PPP enzyme 6-phosphogluconate dehydrogenase (6PGD) in the oxidative PPP results in the generation of superior CD8+ T effector cells. These cells have gene signatures and immunogenic markers of effector phenotype and show potent anti-tumor functions both in vitro and in vivo. In these cells, metabolic reprogramming occurs along with increased mitochondrial ROS and activated antioxidation machinery to balance ROS production against oxidative damage. Our findings reveal a role of 6PGD as a checkpoint for T cell effector differentiation/survival and evidence for 6PGD as an attractive metabolic target to improve tumor immunotherapy.

Glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase genes of winter wheat enhance the cold tolerance of transgenic Arabidopsis.

In this study, winter wheat G6PDH (TaG6PDH) and 6PGDH (Ta6PGDH) were investigated. Both their expression and their activity were upregulated under cold stress, suggesting that TaG6PDH and Ta6PGDH positively respond to cold stress in winter wheat. Exogenous abscisic acid (ABA) treatment markedly increased the expression and activity levels of TaG6PDH and Ta6PGDH in winter wheat under cold stress. Subsequently, TaG6PDH-and Ta6PGDH were overexpressed in Arabidopsis, and showed stronger reactive oxygen species (ROS)-scavenging ability and higher survival rate compared with wild-type (WT) plants under cold stress. In addition, we found that TaG6PDH and Ta6PGDH overexpression can promote the oxidative pentose phosphate pathway (OPPP) in the cytoplasm and peroxisomes of Arabidopsis. In summary, Arabidopsis overexpressing TaG6PDH and Ta6PGDH showed improved cold tolerance.

Altered expression of clock and clock-controlled genes in a hSOD1-linked amyotrophic lateral sclerosis mouse model.

Most physiological processes in mammals are subjected to daily oscillations that are governed by a circadian system. The circadian rhythm orchestrates metabolic pathways in a time-dependent manner and loss of circadian timekeeping has been associated with cellular and system-wide alterations in metabolism, redox homeostasis, and inflammation. Here, we investigated the expression of clock and clock-controlled genes in multiple tissues (suprachiasmatic nucleus, spinal cord, gastrocnemius muscle, and liver) from mutant hSOD1-linked amyotrophic lateral sclerosis (ALS) mouse models. We identified tissue-specific changes in the relative expression, as well as altered daily expression patterns, of clock genes, sirtuins (Sirt1, Sirt3, and Sirt6), metabolic enzymes (Pfkfb3, Cpt1, and Nampt), and redox regulators (Nrf2, G6pd, and Pgd). In addition, astrocytes transdifferentiated from induced pluripotent stem cells from SOD1-linked and FUS RNA binding protein-linked ALS patients also displayed altered expression of clock genes. Overall, our results raise the possibility of disrupted cross-talk between the suprachiasmatic nucleus and peripheral tissues in hSOD1G93A mice, preventing proper peripheral clock regulation and synchronization. Since these changes were observed in symptomatic mice, it remains unclear whether this dysregulation directly drives or it is a consequence of the degenerative process. However, because metabolism and redox homeostasis are intimately entangled with circadian rhythms, our data suggest that altered expression of clock genes may contribute to metabolic and redox impairment in ALS. Since circadian dyssynchrony can be rescued, these results provide the groundwork for potential disease-modifying interventions.

The structure of a novel membrane-associated 6-phosphogluconate dehydrogenase from Gluconacetobacter diazotrophicus (Gd6PGD) reveals a subfamily of short-chain 6PGDs.

The enzyme 6-phosphogluconate dehydrogenase catalyzes the conversion of 6-phosphogluconate to ribulose-5-phosphate. It represents an important reaction in the oxidative pentose phosphate pathway, producing a ribose precursor essential for nucleotide and nucleic acid synthesis. We succeeded, for the first time, to determine the three-dimensional structure of this enzyme from an acetic acid bacterium, Gluconacetobacter diazotrophicus (Gd6PGD). Active Gd6PGD, a homodimer (70 kDa), was present in both the soluble and the membrane fractions of the nitrogen-fixing microorganism. The Gd6PGD belongs to the newly described subfamily of short-chain (333 AA) 6PGDs, compared to the long-chain subfamily (480 AA; e.g., Ovis aries, Homo sapiens). The shorter amino acid sequence in Gd6PGD induces the exposition of hydrophobic residues in the C-terminal domain. This distinct structural feature is key for the protein to associate with the membrane. Furthermore, in terms of function, the short-chain 6PGD seems to prefer NAD+ over NADP+ , delivering NADH to the membrane-bound NADH dehydrogenase of the microorganisms required by the terminal oxidases to reduce dioxygen to water for energy conservation. ENZYME: ECnonbreakingspace1.1.1.343. DATABASE: Structural data are available in PDB database under the accession number 6VPB.

A single-gene approach for the subspecies classification of Mycobacteroides abscessus.

The subspecies classification of Mycobacteroides abscessus complex into M. abscessus, M. massiliense and M. bolletii requires the amplification and sequencing of multiple genes. The objective of this study was to evaluate the possibility of subspecies classification using a single PCR target. An in silico study was performed to classify 1613 strains deposited in a public database using 9 genes (partial gene sequences of hsp65, rpoB, sodA, argH, cya, glpK, gnd, and murC, and the full gene sequence of MAB_3542c). We found the housekeeping gene gnd to be able to classify the M. abscessus subspecies with high accuracy (99.94%). A single-gene PCR approach based on gnd would be a suitable replacement for the more expensive, labor-intensive and time-consuming multi-gene PCR analysis currently in use for the subspecies identification of M. abscessus.

6PGD Upregulation is Associated with Chemo- and Immuno-Resistance of Renal Cell Carcinoma via AMPK Signaling-Dependent NADPH-Mediated Metabolic Reprograming.

BACKGROUND: The essential role of 6-phosphogluconate dehydrogenase (6PGD), the enzyme catalyzing the oxidative pentose phosphate pathway, in tumor growth and metabolism has garnered attention in recent years. In this work, we are the first to demonstrate that aberrant activation of 6PGD is a feature in renal cell carcinoma (RCC) and is critically involved in renal carcinogenesis and chemo- and immuno-resistance. MATERIALS AND METHODS: 6PGD expression and activity were systematically analyzed in normal and malignant renal cells and tissues. The roles of 6PGD and its downstream mechanism were investigated using gain-of-function and loss-of-function approaches. RESULTS: 6PGD expression and enzyme activity were increased in RCC cells and patients' samples. Activation of 6PGD via gain-of-function approach promoted growth of normal kidney but not RCC cells, and alleviated the efficacy of chemotherapeutic (e.g., 5-FU) and immunotherapeutic (e.g., IFN-α) agents. In contrast, 6PGD inhibition using siRNA knockdown and pharmacological inhibitor physcion augmented the inhibitory effects of 5-FU and IFN-α in RCC. Mechanistic studies demonstrated that 6PGD inhibition activated AMPK signaling, leading to ACC1 enzyme inhibition and reduction of lipid synthesis. In addition, 6PGD inhibition disrupted NADPH and NADH homeostasis in RCC cells as shown by the decreased level of NADPH and NADH, and suppressed SIRT-1 activity. AMPK inhibition by siRNA knockdown reversed the inhibitory effects of physcion, demonstrating that the effect of 6PGD inhibition is AMPK activation dependent. CONCLUSIONS: Our work provides preclinical evidence that 6PGD inhibition may represent a potential therapeutic strategy to augment the efficacy of RCC standard of care drugs.

Pancreatic cancers suppress negative feedback of glucose transport to reprogram chromatin for metastasis.

Although metastasis is the most common cause of cancer deaths, metastasis-intrinsic dependencies remain largely uncharacterized. We previously reported that metastatic pancreatic cancers were dependent on the glucose-metabolizing enzyme phosphogluconate dehydrogenase (PGD). Surprisingly, PGD catalysis was constitutively elevated without activating mutations, suggesting a non-genetic basis for enhanced activity. Here we report a metabolic adaptation that stably activates PGD to reprogram metastatic chromatin. High PGD catalysis prevents transcriptional up-regulation of thioredoxin-interacting protein (TXNIP), a gene that negatively regulates glucose import. This allows glucose consumption rates to rise in support of PGD, while simultaneously facilitating epigenetic reprogramming through a glucose-fueled histone hyperacetylation pathway. Restoring TXNIP normalizes glucose consumption, lowers PGD catalysis, reverses hyperacetylation, represses malignant transcripts, and impairs metastatic tumorigenesis. We propose that PGD-driven suppression of TXNIP allows pancreatic cancers to avidly consume glucose. This renders PGD constitutively activated and enables metaboloepigenetic selection of additional traits that increase fitness along glucose-replete metastatic routes.

Sexual and ecological selection on a sexual conflict gene.

Sexual selection and conflict can act on genes with important metabolic functions, potentially shaping standing genetic variance in such genes and thus evolutionary potential of populations. Here, using experimental evolution, we show how reproductive competition intensity and thermal environment affect selection on phosphogluconate dehydrogenase (6Pgdh)-a metabolic gene involved in sexual selection and conflict in the bulb mite. The S allele of 6Pgdh increases male success in reproductive competition, but is detrimental to S-bearing males' partners. We found that the rate of the S allele spread increased with the proportion of males in the experimental populations, illustrating that harm to females is more easily compensated for males under more intense sexual competition. Furthermore, we found that under equal sex ratio, the S allele spreads faster at higher temperature. While the direction of selection on 6Pgdh was not reversed in any of the conditions we tested, which would be required for environmental heterogeneity to maintain polymorphism at this locus, our study highlights that ecological and sexual selection can jointly affect selection on important metabolic enzymes.

Cystine transporter regulation of pentose phosphate pathway dependency and disulfide stress exposes a targetable metabolic vulnerability in cancer.

SLC7A11-mediated cystine uptake is critical for maintaining redox balance and cell survival. Here we show that this comes at a significant cost for cancer cells with high levels of SLC7A11. Actively importing cystine is potentially toxic due to its low solubility, forcing cancer cells with high levels of SLC7A11 (SLC7A11high) to constitutively reduce cystine to the more soluble cysteine. This presents a significant drain on the cellular NADPH pool and renders such cells dependent on the pentose phosphate pathway. Limiting glucose supply to SLC7A11high cancer cells results in marked accumulation of intracellular cystine, redox system collapse and rapid cell death, which can be rescued by treatments that prevent disulfide accumulation. We further show that inhibitors of glucose transporters selectively kill SLC7A11high cancer cells and suppress SLC7A11high tumour growth. Our results identify a coupling between SLC7A11-associated cystine metabolism and the pentose phosphate pathway, and uncover an accompanying metabolic vulnerability for therapeutic targeting in SLC7A11high cancers.

6-Phosphogluconate dehydrogenase fuels multiple aspects of cancer cells: From cancer initiation to metastasis and chemoresistance.

Reprogrammed metabolism is key biochemical characteristic of malignant cells, which represents one of the emerging hallmarks of cancer. Currently, there is rising contemplation on oxidative pentose phosphate pathway (PPP) enzymes as potential therapeutic hits due to their affiliation with tumor metabolism. 6-Phosphogluconate dehydrogenase (6PGD), third oxidative decarboxylase of PPP, has received a great deal of attention during recent years due to its critical role in tumorigenesis and redox homeostasis. 6PGD has been reported to overexpress in number of cancer types and its hyperactivation is mediated through post-transcriptional and post-translational modifications by YTH domain family 2 (YTHDF2), Nrf2 (nuclear factor erythroid 2-related factor 2), EGFR (epidermal growth factor receptor) and via direct structural interactions with ME1 (malic enzyme 1). Upregulated expression of 6PGD provides metabolic as well as defensive advantage to cancer cells, thus, promoting their proliferative and metastatic potential. Moreover, enhanced 6PGD expression also performs key role in development of chemoresistance as well as radiation resistance in cancer. This review aims to discuss the historical timeline and cancer-specific role of 6PGD, pharmacological and genetic inhibitors of 6PGD and 6PGD as prognostic biomarker in order to explore its potential for therapeutic interventions. We anticipate that targeting this imperative supplier of NADPH might serve as tempting avenue to combat the deadly disease like cancer.

YTH domain family 2 promotes lung cancer cell growth by facilitating 6-phosphogluconate dehydrogenase mRNA translation.

N6-methyladenosine (m6A) is one of widespread post-transcriptional mRNA modifications in eukaryotes and the m6A modification plays critical roles in various human cancers. However, the role of m6A-binding proteins in cancer metabolism remains elusive. Here, we report that YTH domain family 2 (YTHDF2) is upregulated in lung cancer tissues, promotes lung cancer cell growth and enhances the pentose phosphate pathway (PPP) flux, which is crucial for tumor growth. Mechanistically, YTHDF2 directly binds to the m6A modification site of 6-phosphogluconate dehydrogenase (6PGD) three prime untranslated region (3'-UTR) to promote 6PGD mRNA translation in lung cancer cells. Collectively, our data indicate that YTHDF2 acts as a tumor promoter to enhance tumor growth via facilitating 6PGD mRNA translation.

Mitochondrial glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase abrogate p53 induced apoptosis in a yeast model: Possible implications for apoptosis resistance in cancer cells.

BACKGROUND: Escape from apoptosis is an important hallmark of tumor progression and drug resistance in cancer cells. It is well demonstrated that over-expression of human wtp53 in Saccharomyces cerevisiae induces apoptosis by directly targeting the mitochondria. In this study, we showed that how S.cerevisiae escaped from p53 induced apoptosis in the presence of a fermentable carbon source (sucrose), but not on non-fermentable carbon source (glycerol). METHODS: Mitochondrial fractions from yeast cultures grown in the presence of sucrose or glycerol with and without p53 expression were fractionated and analyzed by LC-MS/MS. Differentially expressed proteins were studied and detailed biochemical analysis for selected proteins was performed.The effect of mitochondrial HXK-2 over-expression induced by p53 in sucrose grown cells on cell survival was evaluated using gene deletion/tagging, co-localisation and mitochondrial ROS detection. RESULTS: We observe that mitochondria isolated from p53 over-expressing cells accumulate Pentose phosphate Pathway (PPP) enzymes including glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) which led to enhanced mitochondrial NADPH production only when cells are cultured in sucrose but not glycerol. In contrast, mitochondria isolated from Δhxk2 p53 over-expressing cells grown in sucrose did not accumulate G6PDH and 6PGDH and resulted in defective growth. CONCLUSIONS: Enhanced association of HXK2 with the mitochondria with the concomitant accumulation of G6PDG and 6PGDH results in increased NADPH that scavenges ROS and provides resistance to apoptosis. GENERAL SIGNIFICANCE: Given the extensive similarity of aerobic glycolysis between humans and yeast, the phenomena described here could as well be responsible for the escape of apoptosis in cancer cells.

Functional Genomics Reveals Synthetic Lethality between Phosphogluconate Dehydrogenase and Oxidative Phosphorylation.

The plasticity of a preexisting regulatory circuit compromises the effectiveness of targeted therapies, and leveraging genetic vulnerabilities in cancer cells may overcome such adaptations. Hereditary leiomyomatosis renal cell carcinoma (HLRCC) is characterized by oxidative phosphorylation (OXPHOS) deficiency caused by fumarate hydratase (FH) nullizyogosity. To identify metabolic genes that are synthetically lethal with OXPHOS deficiency, we conducted a genetic loss-of-function screen and found that phosphogluconate dehydrogenase (PGD) inhibition robustly blocks the proliferation of FH mutant cancer cells both in vitro and in vivo. Mechanistically, PGD inhibition blocks glycolysis, suppresses reductive carboxylation of glutamine, and increases the NADP+/NADPH ratio to disrupt redox homeostasis. Furthermore, in the OXPHOS-proficient context, blocking OXPHOS using the small-molecule inhibitor IACS-010759 enhances sensitivity to PGD inhibition in vitro and in vivo. Together, our study reveals a dependency on PGD in OXPHOS-deficient tumors that might inform therapeutic intervention in specific patient populations.