Restricted glycolysis is a primary cause of the reduced growth rate of zinc-deficient yeast cells.

Zinc is required for many critical processes, including intermediary metabolism. In Saccharomyces cerevisiae, the Zap1 activator regulates the transcription of ∼80 genes in response to Zn supply. Some Zap1-regulated genes are Zn transporters that maintain Zn homeostasis, while others mediate adaptive responses that enhance fitness. One adaptive response gene encodes the 2-cysteine peroxiredoxin Tsa1, which is critical to Zn-deficient (ZnD) growth. Depending on its redox state, Tsa1 can function as a peroxidase, a protein chaperone, or a regulatory redox sensor. In a screen for possible Tsa1 regulatory targets, we identified a mutation (cdc19S492A) that partially suppressed the tsa1Δ growth defect. The cdc19S492A mutation reduced activity of its protein product, pyruvate kinase isozyme 1 (Pyk1), implicating Tsa1 in adapting glycolysis to ZnD conditions. Glycolysis requires activity of the Zn-dependent enzyme fructose-bisphosphate aldolase 1, which was substantially decreased in ZnD cells. We hypothesized that in ZnD tsa1Δ cells, the loss of a compensatory Tsa1 regulatory function causes depletion of glycolytic intermediates and restricts dependent amino acid synthesis pathways, and that the decreased activity of Pyk1S492A counteracted this depletion by slowing the irreversible conversion of phosphoenolpyruvate to pyruvate. In support of this model, supplementing ZnD tsa1Δ cells with aromatic amino acids improved their growth. Phosphoenolpyruvate supplementation, in contrast, had a much greater effect on growth rate of WT and tsa1Δ ZnD cells, indicating that inefficient glycolysis is a major factor limiting yeast growth. Surprisingly however, this restriction was not primarily due to low fructose-bisphosphate aldolase 1 activity, but instead occurs earlier in glycolysis.

PKM2 is a Novel Osteoporosis-Associated Protein in Chinese.

Purpose:Osteoporosis is characterized by low bone mineral density (BMD) and high risk of osteoporotic fracture (OF). Peripheral blood monocytes (PBM) can differentiate into osteoclasts to resorb bone. This study was to identify PBM-expressed proteins significant for osteoporosis in Chinese Han elderly population (>65 years), and focused on two phenotypes of osteoporosis: low BMD and OF. METHODS: Label-free quantitative proteomics was employed to profile PBM proteome and to identify differentially expressed proteins (DEPs) between OF (N=27) vs. non-fractured (NF, N=24) subjects and between low BMD (N=12) vs. high BMD (N=12) subjects in women. Western blotting (WB) was conducted to validate differential expression, and ELISA to evaluate translational value for secretory protein of interest. RESULTS: We discovered 59 DEPs with fold change (FC)>1.3 (P<1×10-5), and validated the significant up-regulation of pyruvate kinase isozyme 2 (PKM2) with osteoporosis (P<0.001). PKM2 protein upregulation with OF was replicated with PBM in men (P=0.04). Plasma PKM2 protein level was significantly elevated with OF in an independent sample (N=100, FC=1.68, P=0.01). Pursuant functional assays showed that extracellular PKM2 protein supplement not only promoted monocyte trans-endothelial migration, growth, and osteoclast differentiation (marker gene expression), but also inhibited osteoblast growth, differentiation (ALP gene expression), and activity. CONCLUSION: The above findings suggest that PKM2 protein is a novel osteoporosis-associated functional protein in Chinese Han elderly population. It may serve as a risk biomarker and drug target for osteoporosis.

Phytocompounds screening of Nigella sativa in terms of human cancer by targeting sphingosine kinase-1 and pyruvate kinase-M2: a study based on in silico analysis.

Cancer is a multifactorial disease that can cause morbidity and mortality in humans. An altered gene expression in cancer leads to a change in the overall activity of the human cell. Overexpression of cancer protein may give a piece of wide information about the specific type of tumor. Sphingosine kinase-1 (SK-1) is a metabolic enzyme that is mainly overexpressed in several types of cancer and other inflammatory diseases. Similarly, pyruvate kinase-M2 (PK-M2) is an important oncogenic ATP-producing glycolytic enzyme that is upregulated in most cancer cells. The phytocompound of medicinal plants such as Nigella sativa contains a variety of micronutrients that inhibit the proliferation and activity of tumor cells. In this study, the role of phytocompounds in combating cancer was studied against the model kinase proteins, that is, PK-M2 and SK-1. In silico tool like the PASS-Way2Drug server was used to predict the anticancer properties of phytocompounds. Moreover, the CLC-Pred web server provided the cytotoxicity prediction of chemical compounds against several human cancer cell lines. The pharmacokinetics and toxicity profiles were predicted by the SwissADME and pkCSM software. The binding energies were obtained by molecular docking to confirm the intermolecular interaction of selected phytocompounds with proteins. Consequently, molecular dynamics (MD) simulation confirmed the stability, conformational changes, and dynamic behavior of the kinase proteins complexed with the lead phytocompounds, that is, epicatechin, apigenin, and kaempferol.Communicated by Ramaswamy H. Sarma.

Chlorpromazine affects glioblastoma bioenergetics by interfering with pyruvate kinase M2.

Glioblastoma (GBM) is the most frequent and lethal brain tumor, whose therapeutic outcome - only partially effective with current schemes - places this disease among the unmet medical needs, and effective therapeutic approaches are urgently required. In our attempts to identify repositionable drugs in glioblastoma therapy, we identified the neuroleptic drug chlorpromazine (CPZ) as a very promising compound. Here we aimed to further unveil the mode of action of this drug. We performed a supervised recognition of the signal transduction pathways potentially influenced by CPZ via Reverse-Phase Protein microArrays (RPPA) and carried out an Activity-Based Protein Profiling (ABPP) followed by Mass Spectrometry (MS) analysis to possibly identify cellular factors targeted by the drug. Indeed, the glycolytic enzyme PKM2 was identified as one of the major targets of CPZ. Furthermore, using the Seahorse platform, we analyzed the bioenergetics changes induced by the drug. Consistent with the ability of CPZ to target PKM2, we detected relevant changes in GBM energy metabolism, possibly attributable to the drug's ability to inhibit the oncogenic properties of PKM2. RPE-1 non-cancer neuroepithelial cells appeared less responsive to the drug. PKM2 silencing reduced the effects of CPZ. 3D modeling showed that CPZ interacts with PKM2 tetramer in the same region involved in binding other known activators. The effect of CPZ can be epitomized as an inhibition of the Warburg effect and thus malignancy in GBM cells, while sparing RPE-1 cells. These preclinical data enforce the rationale that allowed us to investigate the role of CPZ in GBM treatment in a recent multicenter Phase II clinical trial.

In vitro galactose impairs energy metabolism in the brain of young rats: protective role of antioxidants.

We, herein, investigated the in vitro effects of galactose on the activity of pyruvate kinase, succinate dehydrogenase (SDH), complex II and IV (cytochrome c oxidase) of the respiratory chain and Na+K+-ATPase in the cerebral cortex, cerebellum and hippocampus of 30-day-old rats. We also determined the influence of the antioxidants, trolox, ascorbic acid and glutathione, on the effects elicited by galactose. Galactose was added to the assay at concentrations of 0.1, 3.0, 5.0 and 10.0 mM. Control experiments were performed without galactose. Galactose, at 3.0, 5.0 and 10.0 mM, decreased pyruvate kinase activity in the cerebral cortex and at 10.0 mM in the hippocampus. Galactose, at 10.0 mM, reduced SDH and complex II activities in the cerebellum and hippocampus, and reduced cytochrome c oxidase activity in the hippocampus. Additionally, decreased Na+K+-ATPase activity in the cerebral cortex and hippocampus; conversely, galactose, at 3.0 and 5.0 mM, increased this enzyme's activity in the cerebellum. Data show that galactose disrupts energy metabolism and trolox, ascorbic acid and glutathione addition prevented the majority of alterations in the parameters analyzed, suggesting the use of antioxidants as an adjuvant therapy in Classic galactosemia.

Anti-tumor effects of novel alkannin derivatives with potent selectivity on comprehensive analysis.

BACKGROUND: Therapeutic approaches based on glycolysis and energy metabolism of tumor cells are new promising strategies for the treatment of cancer. Currently, researches on the inhibition of pyruvate kinase M2, a key rate limiting enzyme in glycolysis, have been corroborated as an effective cancer therapy. Alkannin is a potent pyruvate kinase M2 inhibitor. However, its non-selective cytotoxicity has affected its subsequent clinical application. Thus, it needs to be structurally modified to develop novel derivatives with high selectivity. PURPOSE: Our study aimed to ameliorate the toxicity of alkannin through structural modification and elucidate the mechanism of the superior derivative 23 in lung cancer therapy. METHODS: On the basis of the principle of collocation, different amino acids and oxygen-containing heterocycles were introduced into the hydroxyl group of the alkannin side chain. We examined the cell viability of all derivatives on three tumor cells (HepG2, A549 and HCT116) and two normal cells (L02 and MDCK) by MTT assay. Besides, the effect of derivative 23 on the morphology of A549 cells as observed by Giemsa and DAPI staining, respectively. Flow cytometry was performed to assess the effects of derivative 23 on apoptosis and cell cycle arrest. To further assess the effect of derivative 23 on the Pyruvate kinase M2 in glycolysis, an enzyme activity assay and western blot assay were performed. Finally, in vivo the antitumor activity and safety of the derivative 23 were evaluated by using Lewis mouse lung cancer xenograft model. RESULTS: Twenty-three novel alkannin derivatives were designed and synthesized to improve the cytotoxicity selectivity. Among these derivatives, derivative 23 showed the highest cytotoxicity selectivity between cancer and normal cells. The anti-proliferative activity of derivative 23 on A549 cells (IC50 = 1.67 ± 0.34 µM) was 10-fold higher than L02 cells (IC50 = 16.77 ± 1.44 µM) and 5-fold higher than MDCK cells (IC50 = 9.23 ± 0.29 µM) respectively. Subsequently, fluorescent staining and flow cytometric analysis showed that derivative 23 was able to induce apoptosis of A549 cells and arrest the cell cycle in the G0/G1 phase. In addition, the mechanistic studies suggested derivative 23 was an inhibitor of pyruvate kinase; it could regulate glycolysis by inhibiting the activation of the phosphorylation of PKM2/STAT3 signaling pathway. Furthermore, studies in vivo demonstrated derivative 23 significantly inhibited the growth of xenograft tumor. CONCLUSION: In this study, alkannin selectivity is reported to be significantly improved following structural modification, and derivative 23 is first shown to be able to inhibit lung cancer growth via the PKM2/STAT3 phosphorylation signaling pathway in vitro, indicating the potential value of derivative 23 in treating lung cancer.

Prenatal management of fetal anemia due to pyruvate kinase deficiency: A case report.

BACKGROUND: Pyruvate Kinase (PK) deficiency is the most common enzyme defect of glycolysis, leading to congenital hemolytic anemia, which can occur during the neonatal period. STUDY DESIGN AND METHODS: We report the prenatal management of fetal anemia related to PK deficiency in a family with a severe proband. RESULTS: The couple had a first child born with hydrops, whose PK deficiency was diagnosed at 18 months of life. He was treated with allogeneic bone marrow transplantation. The second child was free from disease. For the third pregnancy, the amniocentesis revealed a PK deficiency. Weekly ultrasound monitoring of the middle cerebral artery velocity allowed the detection of severe fetal anemia. Two intrauterine red blood cell transfusions (IUTs) were performed, raising the fetal hemoglobin from 6.6 to 14.5 g/dl at 28 weeks' gestation and from 8.9 to 15.3 g/dl at 31 weeks. A hematopoietic stem cell allograft was discussed prenatally but not chosen, as it would not have significantly changed the perinatal prognosis. The patient delivered a 2730 g girl at 37 weeks, with hemoglobin of 13.6 g/dl. The child presented with neonatal jaundice treated with phototherapy and received postnatal transfusions. DISCUSSION: When a proband is identified in a family, fetal investigation is warranted, to set up third-trimester ultrasound surveillance and perinatal management. In case of fetal severe anemia of unknown etiology, the workup on fetal blood sampling before IUT should comprise the search for erythrocytes enzymopathies, such as PK deficiency. IUTs allow safer full-term delivery in cases with PK deficiency.

Structure-Guided Approach to Discover Tuberosin as a Potent Activator of Pyruvate Kinase M2, Targeting Cancer Therapy.

Metabolic reprogramming is a key attribute of cancer progression. An altered expression of pyruvate kinase M2 (PKM2), a phosphotyrosine-binding protein is observed in many human cancers. PKM2 plays a vital role in metabolic reprogramming, transcription and cell cycle progression and thus is deliberated as an attractive target in anticancer drug development. The expression of PKM2 is essential for aerobic glycolysis and cell proliferation, especially in cancer cells, facilitating selective targeting of PKM2 in cell metabolism for cancer therapeutics. We have screened a virtual library of phytochemicals from the IMPPAT (Indian Medicinal Plants, Phytochemistry and Therapeutics) database of Indian medicinal plants to identify potential activators of PKM2. The initial screening was carried out for the physicochemical properties of the compounds, and then structure-based molecular docking was performed to select compounds based on their binding affinity towards PKM2. Subsequently, the ADMET (absorption, distribution, metabolism, excretion and toxicity) properties, PAINS (Pan-assay interference compounds) patterns, and PASS evaluation were carried out to find more potent hits against PKM2. Here, Tuberosin was identified from the screening process bearing appreciable binding affinity toward the PKM2-binding pocket and showed a worthy set of drug-like properties. Finally, molecular dynamics simulation for 100 ns was performed, which showed decent stability of the protein-ligand complex and relatival conformational dynamics throughout the trajectory. The study suggests that modulating PKM2 with natural compounds is an attractive approach in treating human malignancy after required validation.

Identification of Natural Compounds as Inhibitors of Pyruvate Kinase M2 for Cancer Treatment.

The reliance of tumor cells on aerobic glycolysis is one of the emerging hallmarks of cancer. Pyruvate kinase M2 (PKM2), an important enzyme of glycolytic pathway, is highly expressed in a number of cancer cells. Tumor cells heavily depend on PKM2 to fulfill their divergent energetic and biosynthetic requirements, suggesting it as novel drug target for cancer therapies. Based on this context, we performed enzymatic-assay-based screening of the in-house phenolic compounds library for the identification of PKM2 inhibitors. This screening identified silibinin, curcumin, resveratrol, and ellagic acid as potential inhibitors of PKM2 with IC50 values of 0.91 µM, 1.12 µM, 3.07 µM, and 4.20 µM respectively. For the determination of Ki constants and the inhibition type of hit compounds, Lineweaver-Burk graphs were plotted. Silibinin and ellagic acid performed the competitive inhibition of PKM2 with Ki constants of 0.61 µM and 5.06 µM, while curcumin and resveratrol were identified as non-competitive inhibitors of PKM2 with Ki constants of 1.20 µM and 7.34 µM. The in silico screening of phenolic compounds against three binding sites of PKM2 provided insight into the binding pattern and functionally important amino residues of PKM2. Further, the evaluation of cytotoxicity via MTT assay demonstrated ellagic acid as potent inhibitor of cancer cell growth (IC50 = 20 µM). These results present ellagic acid, silibinin, curcumin, and resveratrol as inhibitors of PKM2 to interrogate metabolic reprogramming in cancer cells. This study has also provided the foundation for further research to validate the potential of identified bioactive entities for PKM2 targeted-cancer therapies.

Unraveling the metabolism of Mycobacterium caprae using comparative genomics.

In our laboratory, Mycobacterium caprae has poor growth in standard medium (SM) 7H9-OADC supplemented with pyruvate and Tween-80. Our objectives were to identify mutations affecting M. caprae metabolism and use this information to design a culture medium to improve its growth. We selected 77 M. caprae genomes and sequenced M. caprae NLA000201913 used in our experiments. Mutations present in >95% of the strains compared to Mycobacterium tuberculosis H37Rv were analyzed in silico for their deleterious effects on proteins of metabolic pathways. Apart from the known defect in the pyruvate kinase, M. caprae has important lesions in enzymes of the TCA cycle, methylmalonyl cycle, B12 metabolism, and electron-transport chain. We provide evidence of enzymatic redundancy elimination and epistatic mutations, and possible production of toxic metabolites hindering M. caprae growth in vitro. A newly designed SM supplemented with l-glutamate allowed faster growth and increased final microbial mass of M. caprae. However, possible accumulation of metabolic waste-products and/or nutritional limitations halted M. caprae growth prior to a M. tuberculosis-like stationary phase. Our findings suggest that M. caprae relies on GABA and/or glyoxylate shunts for in vitro growth in routine media. The newly developed medium will improve experiments with this bacterium by allowing faster growth in vitro.

In-Silico Analysis of Phytocompounds of Olea europaea as Potential Anti-Cancer Agents to Target PKM2 Protein.

Globally, cancer is the second leading cause of mortality and morbidity. The growth and development of cancer are extremely complex. It is caused by a variety of pathways and involves various types of enzymes. Pyruvate kinase M2 (PKM2) is an isoform of pyruvate kinase, that catalyses the last steps of glycolysis to produce energy. PKM2 is relatively more expressed in tumour cells where it tends to exist in a dimer form. Various medicinal plants are available that contain a variety of micronutrients to combat against different cancers. The phytocompounds of the olive tree (Olea europaea) leaves play an important role in inhibiting the proliferation of several cancers. In this study, the phytocompounds of olive leaf extract (OLE) were studied using various in silico tools, such as pkCSM software to predict ADMET properties and PASS Online software to predict anticancer activity. However, the molecular docking study provided the binding energies and inhibition constant and confirmed the interaction between PKM2 and the ligands. The dynamic behaviour, conformational changes, and stability between PKM2 and the top three hit compounds (Verbascoside (Ver), Rutin (Rut), and Luteolin_7_O_glucoside (Lut)) are studied by MD simulations.

Ultrasonic treatment decreases Lyophyllum decastes fruiting body browning and affects energy metabolism.

Lyophyllum decastes is a common mushroom that is prone to browning during prolonged storage. In this study, the effects of ultrasonic treatment on metabolic gene expression, enzyme activity, and metabolic compounds related to L. decastes browning were investigated. Treatment of the fruiting body at 35 kHz and 300 W for 10 min reduced the browning index of L. decastes by 21.0 % and increased the L* value by 11.1 %. Ultrasonic treatment of the fruiting body resulted in higher levels of total phenols, flavonoids, and 9 kinds of amino acid with catalase (CAT) and peroxidase (POD) activities maintained at high levels. Higher cytochrome c oxidase (CCO), succinate dehydrogenase (SDH), phosphofructokinase (PFK), and pyruvate kinase (PK) activities may be ascribed to increased antioxidant capacity. Moreover, ultrasonication retained higher adenosine triphosphate (ATP) concentrations with an increased energy charge, while there were lower levels of adenosine diphosphate (ADP) and reduced and oxidized nicotinamide adenine dinucleotide (NADH and NAD+), respectively. Meanwhile, lower lignin contents were observed, along with retarded polyphenol oxidase (PPO) and lipoxygenase (LOX) activities. Lower PPO activity reduced the fruiting body enzymatic browning rate through decreased expression of LdPpo1, LdPpo2, and LdPpo3 during storage at 4 °C for 16 days. This activity may be used to determine the effectiveness of ultrasonication.

Cancer metabolism control by natural products: Pyruvate kinase M2 targeting therapeutics.

Glycolysis is the primary source of energy for cancer growth and metastasis. The shift in metabolism from mitochondrial oxidative phosphorylation to aerobic glycolysis is called the Warburg effect. Cancer progression due to aerobic glycolysis is often associated with the activation of oncogenes or the loss of tumor suppressors. Therefore, inhibition of glycolysis is one of the effective strategies in cancer control. Pyruvate kinase M2 (PKM2) is a key glycolytic enzyme overexpressed in breast, prostate, lung, colorectal, and liver cancers. Here, we discuss published studies regarding PKM2 inhibitors from natural products that are promising drug candidates for cancer therapy. We have highlighted the potential of natural PKM2 inhibitors for various cancer types. Moreover, we encourage researchers to evaluate the combinational effects between natural and synthetic PKM2 inhibitors. Also, further high-quality studies are needed to firmly establish the clinical efficacy of natural products.

Effect of modified Jianpi Yangzheng on regulating content of PKM2 in gastric cancer cells-derived exosomes.

BACKGROUND: Modified Jianpi Yangzheng decoction (mJPYZ), as an empirical decoction of Traditional Chinese medicine has been shown significantly to prolong the survival of patients with advanced stage gastric cancer. Pyruvate kinase M2 (PKM2), has attracted attention for its important role on cellular aerobic glycolysis, however, few studies focus on PKM2 non-metabolic roles in tumor progression. PURPOSE: Our study aimed to investigate the potential role of gastric cancer exosomes containing PKM2 in regulating tumor-associated macrophages (TAM) and the mechanism of mJPYZ against gastric cancer. METHODS: Colony Formation Assay, flow cytometry and TUNEL staining were employed to estimate the effect of mJPYZ on gastric cancer in tumor-bearing mice and cells. Western blot analyzed apoptosis-related protein expression changes. Network pharmacology and bioinformatics predicted potential exosomes modulation of mJPYZ in gastric cancer. Exosomes were isolated and co-cultured with TAM. Diff-Quik Staining observed the TAM morphological changes when incubating with gastric cancer cells exosomes. Flow cytometry and immunofluorescence were performed to demonstrate whether exosomes PKM2 involved in TAM polarization. RESULTS: mJPYZ induced apoptosis of gastric cancer cells by targeting PKM2 and downregulating PI3K/Akt/mTOR axis in vivo and in vitro. Network pharmacology showed potential exosomes modulation of mJPYZ in gastric cancer. We extracted exosomes and found mJPYZ decreased the abundance of serum exosomes PKM2 in patients with advanced gastric cancer and xenograft tumor model. Additionally, we firstly detected and confirmed that PKM2 is a package protein of exosomes extracted from gastric cancer cells, and mJPYZ could diminish the content of exosomal PKM2 in gastric cancer cells. Importantly, mJPYZ reduced the delivery of exosomal PKM2 from tumor cells to macrophages, and alleviated exosomal PKM2-induced differentiation of M2-TAM in tumor microenvironment, eventually inhibited gastric cancer progression. CONCLUSION: Gastric cancer exosomes containing PKM2 could lead to M2 macrophages differentiation, thereby promoting gastric cancer progression. Our findings provide a rationale for potential application of mJPYZ in the treatment of gastric cancer via PKM2.

Shikonin inhibited glycolysis and sensitized cisplatin treatment in non-small cell lung cancer cells via the exosomal pyruvate kinase M2 pathway.

The active ingredient of the traditional Chinese medicine comfrey is shikonin, a naphthoquinone compound. The focus of this study was to investigate the effect of shikonin on the proliferation, invasion, migration, and chemoresistance of non-small cell lung cancer (NSCLC) cells, and to explore its underlying molecular biological mechanisms. The results show that shikonin inhibited the viability, proliferation, invasion, and migration of NSCLC cells A549 and PC9, and induced apoptosis. As the inhibitor of pyruvate kinase M2 (PKM2), a key enzyme in glycolysis, shikonin inhibited glucose uptake and the production of lactate, the final metabolite of aerobic glycolysis. In vivo chemotherapeutic assay showed that shikonin reduced the tumor volume and weight in NSCLC mice model and increased the sensitivity to cisplatin chemotherapy. Histoimmunology experiments showed the combination of shikonin and cisplatin downregulated the expression of PKM2 and its transcriptionally regulated downstream gene glucose transporter 1 (Glut1) in tumor tissue. In an assessment of glucose metabolism, micro-PET/CT data showed a combination of shikonin and cisplatin inhibited the fluorodeoxy glucose (18F-FDG) uptake into tumor. Since exosomal PKM2 affected the sensitivity to cisplatin in NSCLC cells, we also demonstrated shikonin could inhibit exosome secretion and exosomal PKM2 through the administration of exosomal inhibitor GW4869. Furthermore, shikonin sensitized cisplatin treatment by reducing the extracellular secretion of exosomal PKM2. In conclusion, we suggest that shikonin not only inhibits PKM2 intracellularly but also reduces glycolytic flux and increases cisplatin sensitivity through the exosomal pathway.

Emodin ameliorates antioxidant capacity and exerts neuroprotective effect via PKM2-mediated Nrf2 transactivation.

Pyruvate kinase M2 (PKM2) is overexpressed in neuronal cells. However, there are few studies on the involvement of PKM2 modulators in neurodegenerative diseases. Emodin, a dominating anthraquinone derivative extracting from the rhizome of rhubarb, has received expanding consideration due to its pharmacological properties. Our data reveal that emodin could resist hydrogen peroxide- or 6-hydroxydopamine-mediated mitochondrial fission and apoptosis in PC12 cells (a neuron-like rat pheochromocytoma cell line). Notably, emodin at nontoxic concentrations significantly inhibits PKM2 activity and promotes dissociation of tetrameric PKM2 into dimers in cells. The PKM2 dimerization enhances the interaction of PKM2 and NFE2-related factor 2 (Nrf2), which further triggers the activation of the Nrf2/ARE pathway to upregulate a panel of cytoprotective genes. Modulating the PKM2/Nrf2/ARE axis by emodin unveils a novel mechanism for understanding the pharmacological functions of emodin. Our findings indicate that emodin is a potential candidate for the treatment of oxidative stress-related neurodegenerative disorders.

Multiple functions of pyruvate kinase M2 in various cell types.

Glucose metabolism is a mechanism by which energy is produced in form of adenosine triphosphate (ATP) by mitochondria and precursor metabolites are supplied to enable the ultimate enrichment of mature metabolites in the cell. Recently, glycolytic enzymes have been shown to have unconventional but important functions. Among these enzymes, pyruvate kinase M2 (PKM2) plays several roles including having conventional metabolic enzyme activity, and also being a transcriptional regulator and a protein kinase. Compared with the closely related PKM1, PKM2 is highly expressed in cancer cells and embryos, whereas PKM1 is dominant in mature, differentiated cells. Posttranslational modifications such as phosphorylation and acetylation of PKM2 change its cellular functions. In particular, PKM2 can translocate to the nucleus, where it regulates the transcription of many target genes. It is notable that PKM2 also acts as a protein kinase to phosphorylate several substrate proteins. Besides cancer cells and embryonic cells, astrocytes also highly express PKM2, which is crucial for lactate production via expression of lactate dehydrogenase A (LDHA), while mature neurons predominantly express PKM1. The lactate produced in cancer cells promotes tumor progress and that in astrocytes can be supplied to neurons and may act as a major source for neuronal ATP energy production. Thereby, we propose that PKM2 along with its different posttranslational modifications has specific purposes for a variety of cell types, performing unique functions.

Identification of the antibacterial mechanism of cryptotanshinone on methicillin-resistant Staphylococcus aureus using bioinformatics analysis.

Cryptotanshinone (CT) is an extract from the traditional Chinese medicine Salvia miltiorrhiza, which inhibits the growth of methicillin-resistant Staphylococcus aureus (MRSA) in vitro. This study aims to determine the antibacterial mechanisms of CT by integrating bioinformatics analysis and microbiology assay. The microarray data of GSE13203 was retrieved from the Gene Expression Omnibus (GEO) database to screen the differentially expressed genes (DEGs) of S. aureus strains that were treated with CT treatment. Gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were used to identify the potential target of CT. Data mining on the microarray dataset indicated that pyruvate kinase (PK) might be involved in the antimicrobial activities of CT. The minimum inhibition concentrations (MICs) of CT or vancomycin against the MRSA strain ATCC43300 and seven other clinical strains were determined using the broth dilution method. The effects of CT on the activity of PK were further measured. In vitro tests verified that CT inhibited the growth of an MRSA reference strain and seven other clinical strains. CT hampered the activity of the PK of ATCC43300 and five clinical MRSA strains. CT might hinder bacterial energy metabolism by inhibiting the activity of PK.

Shikonin alleviates choroidal neovascularization by inhibiting proangiogenic factor production from infiltrating macrophages.

Choroidal neovascularization (CNV), a feature of neovasular age-related macular degeneration (AMD), acts as a leading cause of vision loss in the elderly. Shikonin (SHI), a natural bioactive compound extracted from Chinese herb radix arnebiae, exerts anti-inflammatory and anti-angiogenic roles and also acts as a potential pyruvate kinase M2 (PKM2) inhibitor in macrophages. The major immune cells macrophages infiltrate the CNV lesions, where the production of pro-angiognic cytokines from macrophage facilitates the development of CNV. PKM2 contributes to the neovascular diseases. In this study, we found that SHI oral gavage alleviated the leakage, area and volume of mouse laser-induced CNV lesion and inhibited macrophage infiltration without ocular cytotoxicity. Moreover, SHI inhibited the secretion of pro-angiogenic cytokine, including basic fibroblast growth factor (FGF2), insulin-like growth factor-1 (IGF1), chemokine (C-C motif) ligand 2 (CCL2), placental growth factor and vascular endothelial growth factor (VEGF), from primary human macrophages by down-regulating PKM2/STAT3/CD163 pathway, indicating a novel potential therapy strategy for CNV.

Lipid metabolism: new twists to the Yin and Yang of PKM2 in cancer.

While canonical and non-canonical functions of pyruvate kinase M2 (PKM2) are recognized to mediate often-opposing roles in cancer, its contribution to cellular and systemic fatty acid homeostasis remains poorly understood. A new study by Liu et al (2021) uncovers ER transmembrane protein TMEM33 as a novel target of PKM2, which is essential for regulation of cancer cell cholesterol metabolism. These findings highlight the diversity of tissue-specific functions of PKM2 and potential implications for cancer treatment.