Pyruvate kinase

About: Pyruvate kinase is a research topic. Over the lifetime, 5683 publications have been published within this topic receiving 180020 citations. The topic is also known as: ATP:pyruvate 2-O-phosphotransferase & phosphoenolpyruvate kinase.

PARP14 promotes the Warburg effect in hepatocellular carcinoma by inhibiting JNK1-dependent PKM2 phosphorylation and activation

Abstract: Most tumour cells use aerobic glycolysis (the Warburg effect) to support anabolic growth and evade apoptosis. Intriguingly, the molecular mechanisms that link the Warburg effect with the suppression of apoptosis are not well understood. In this study, using loss-of-function studies in vitro and in vivo, we show that the anti-apoptotic protein poly(ADP-ribose) polymerase (PARP)14 promotes aerobic glycolysis in human hepatocellular carcinoma (HCC) by maintaining low activity of the pyruvate kinase M2 isoform (PKM2), a key regulator of the Warburg effect. Notably, PARP14 is highly expressed in HCC primary tumours and associated with poor patient prognosis. Mechanistically, PARP14 inhibits the pro-apoptotic kinase JNK1, which results in the activation of PKM2 through phosphorylation of Thr365. Moreover, targeting PARP14 enhances the sensitization of HCC cells to anti-HCC agents. Our findings indicate that the PARP14-JNK1-PKM2 regulatory axis is an important determinant for the Warburg effect in tumour cells and provide a mechanistic link between apoptosis and metabolism.

Characterization of a glucose-repressed pyruvate kinase (Pyk2p) in Saccharomyces cerevisiae that is catalytically insensitive to fructose-1,6-bisphosphate.

Abstract: We have characterized the gene YOR347c of Saccharomyces cerevisiae and shown that it encodes a second functional pyruvate kinase isoenzyme, Pyk2p. Overexpression of the YOR347c/PYK2 gene on a multicopy vector restored growth on glucose of a yeast pyruvate kinase 1 (pyk1) mutant strain and could completely substitute for the PYK1-encoded enzymatic activity. PYK2 gene expression is subject to glucose repression. A pyk2 deletion mutant had no obvious growth phenotypes under various conditions, but the growth defects of a pyk1 pyk2 double-deletion strain were even more pronounced than those of a pyk1 single-mutation strain. Pyk2p is active without fructose-1,6-bisphosphate. However, overexpression of PYK2 during growth on ethanol did not cause any of the deleterious effects expected from a futile cycling between pyruvate and phosphoenolpyruvate. The results indicate that the PYK2-encoded pyruvate kinase may be used under conditions of very low glycolytic flux.

Dichloroacetate induces apoptosis and cell-cycle arrest in colorectal cancer cells

Abstract: Colorectal cancer is the third most common cancer in the world and the fourth leading cause of cancer-related death (Shike et al, 1990). In 2007 colorectal cancer accounted for 17.1 deaths per 100 000 persons in the United Kingdom (UK Bowel Cancer Statistics, 2009). Despite recent advances, the prognosis of patients with advanced and metastatic colorectal cancer remains poor. Targeting tumour metabolism for cancer therapy is a rapidly developing area (Pan and Mak, 2007). Early observations concerning the metabolic differences between cancer and normal cells were made by Otto Warburg, who showed that cancer cells are inherently dependent on glycolysis for production of chemical energy (Warburg, 1956). There is now mounting evidence that this increased glycolysis results from the influence of multiple molecular pathways, including adaptive responses to the hypoxic tumour microenvironment, oncogenic signalling, and mitochondrial dysfunction (Gatenby and Gillies, 2004; Gillies and Gatenby, 2007; Wu et al, 2007). The glycolytic phenotype offers growth advantages to cancer cells by resisting apoptosis, and facilitating tumour spread and metastasis (Yeluri et al, 2009). A key regulator of cellular metabolism is pyruvate dehydrogenase (PDH). Pyruvate dehydrogenase converts pyruvate, produced from glycolysis, to acetyl-CoA, which is oxidised in the tricarboxylic acid cycle within mitochondria. Pyruvate dehydrogenase activity is tightly regulated by inhibitory phosphorylation by pyruvate dehydrogenase kinase (PDK). Phosphorylation occurs on the E1α sub-unit of PDH (PDHE1α) at three sites: Ser232, Ser293, and Ser300 (Rardin et al, 2009). Dichloroacetate (DCA) is an inhibitor of all the four isoenzymes of PDK(1–4) (Stacpoole, 1989), and has recently been shown to reduce growth of lung, endometrial, and breast cancer cell lines (Bonnet et al, 2007; Wong et al, 2008; Sun et al, 2009). It has been reported to reduce growth of these cancer cells mainly by reducing inhibitory phosphorylation of PDH, thereby promoting mitochondrial oxidative phosphorylation and inducing apoptosis through mitochondrial, NFAT-Kv 1.5, and p53 upregulated modulator of apoptosis (PUMA)-mediated pathways. Colorectal cancer cells have been found to undergo increased glycolysis (Bi et al, 2006), and the tumour microenvironment has been found to be hypoxic and acidotic, mainly due to poorly developed blood supply (Dewhirst et al, 1989; Milosevic et al, 2004). We have previously shown that this is especially true for the more aggressive phenotype (Thorn et al, 2009), and expression of the important markers of hypoxia is increased in colorectal cancer especially at the invasive margin (Rajaganeshan et al, 2008, 2009). The purpose of this study was to investigate the effects of DCA on the growth of colorectal cancer cells in an attempt to examine PDK inhibition as a novel therapeutic strategy against colorectal cancer.

Identification and Characterization of MAE1, the Saccharomyces cerevisiae Structural Gene Encoding Mitochondrial Malic Enzyme

Abstract: Pyruvate, a precursor for several amino acids, can be synthesized from phosphoenolpyruvate by pyruvate kinase. Nevertheless, pyk1 pyk2 mutants of Saccharomyces cerevisiae devoid of pyruvate kinase activity grew normally on ethanol in defined media, indicating the presence of an alternative route for pyruvate synthesis. A candidate for this role is malic enzyme, which catalyzes the oxidative decarboxylation of malate to pyruvate. Disruption of open reading frame YKL029c , which is homologous to malic enzyme genes from other organisms, abolished malic enzyme activity in extracts of glucose-grown cells. Conversely, overexpression of YKL029c/MAE1 from the MET25 promoter resulted in an up to 33-fold increase of malic enzyme activity. Growth studies with mutants demonstrated that presence of either Pyk1p or Mae1p is required for growth on ethanol. Mutants lacking both enzymes could be rescued by addition of alanine or pyruvate to ethanol cultures. Disruption of MAE1 alone did not result in a clear phenotype. Regulation of MAE1 was studied by determining enzyme activities and MAE1 mRNA levels in wild-type cultures and by measuring β-galactosidase activities in a strain carrying a MAE1 :: lacZ fusion. Both in shake flask cultures and in carbon-limited chemostat cultures, MAE1 was constitutively expressed. A three- to fourfold induction was observed during anaerobic growth on glucose. Subcellular fractionation experiments indicated that malic enzyme in S. cerevisiae is a mitochondrial enzyme. Its regulation and localization suggest a role in the provision of intramitochondrial NADPH or pyruvate under anaerobic growth conditions. However, since null mutants could still grow anaerobically, this function is apparently not essential.