Browsing by Author "Clem, Amy L."
Now showing 1 - 4 of 4
- Results Per Page
- Sort Options
Item A novel small molecule antagonist of choline kinase-alpha that simultaneously suppresses MAPK and PI3K/AKT signaling(Springernature, 2011-07) Clem, Brian F.; Clem, Amy L.; Goswami, Umesh; Arumugam, Sengodagounder; Telang, Sucheta; Trent, John O.; Chesney, Jason A.; Yalçın, Abdullah; Uludağ Üniversitesi/Veterinerlik Fakültesi/Biyokimya Anabilim Dalı.; 0000-0001-8519-8375; ABI-4164-2020; A-5261-2016; 36857831000Choline kinase-alpha expression and activity are increased in multiple human neoplasms as a result of growth factor stimulation and activation of cancer-related signaling pathways. The product of choline kinase-alpha, phosphocholine, serves as an essential metabolic reservoir for the production of phosphatidylcholine, the major phospholipid constituent of membranes and substrate for the production of lipid second messengers. Using in silico screening for small molecules that may interact with the choline kinase-alpha substrate binding domain, we identified a novel competitive inhibitor, N-(3,5-dimethylphenyl)-2-[[5-(4-ethylphenyl)-1H-1,2,4-triazol-3-yl] sulfanyl] acetamide (termed CK37) that inhibited purified recombinant human choline kinase-alpha activity, reduced the steady-state concentration of phosphocholine in transformed cells, and selectively suppressed the growth of neoplastic cells relative to normal epithelial cells. Choline kinase-alpha activity is required for the downstream production of phosphatidic acid, a promoter of several Ras signaling pathways. CK37 suppressed mitogen-activated protein kinase and phosphatidylinositol 3-kinase/AKT signaling, disrupted actin cytoskeletal organization, and reduced plasma membrane ruffling. Finally, administration of CK37 significantly decreased tumor growth in a lung tumor xenograft mouse model, suppressed tumor phosphocholine, and diminished activating phosphorylations of extracellular signal-regulated kinase and AKT in vivo. Together, these results further validate choline kinase-alpha as a molecular target for the development of agents that interrupt Ras signaling pathways, and indicate that receptor-based computational screening should facilitate the identification of new classes of choline kinase-alpha inhibitors.Item Nuclear targeting of 6-Phosphofructo-2-kinase (PFKFB3) increases proliferation via cyclin-dependent kinases(American Society of Biochemistry Molecular Biology, 2009-09-04) Clem, Brian F.; Simmons, Alan J.; Lane, Andrew N.; Nelson, Kristin; Clem, Amy L.; Brock, Erin; Wattenberg, Brinks W.; Telang, Sucheta; Chesney, Jason; Yalçın, Abdullah; Uludağ Üniversitesi/Veterinerlik Fakültesi/Biyokimya Anabilim Dalı.; 0000-0001-8519-8375; ABI-4164-2020; A-5261-2016; 36857831000The regulation of metabolism and growth must be tightly coupled to guarantee the efficient use of energy and anabolic substrates throughout the cell cycle. Fructose 2,6-bisphosphate (Fru-2,6-BP) is an allosteric activator of 6-phosphofructo-1-kinase (PFK-1), a rate-limiting enzyme and essential control point in glycolysis. The concentration of Fru-2,6-BP in mammalian cells is set by four 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatases (PFKFB1-4), which interconvert fructose 6-phosphate and Fru-2,6-BP. The relative functions of the PFKFB3 and PFKFB4 enzymes are of particular interest because they are activated in human cancers and increased by mitogens and low oxygen. We examined the cellular localization of PFKFB3 and PFKFB4 and unexpectedly found that whereas PFKFB4 localized to the cytoplasm (i.e. the site of glycolysis), PFKFB3 localized to the nucleus. We then overexpressed PFKFB3 and observed no change in glucose metabolism but rather a marked increase in cell proliferation. These effects on proliferation were completely abrogated by mutating either the active site or nuclear localization residues of PFKFB3, demonstrating a requirement for nuclear delivery of Fru-2,6-BP. Using protein array analyses, we then found that ectopic expression of PFKFB3 increased the expression of several key cell cycle proteins, including cyclin-dependent kinase (Cdk)-1, Cdc25C, and cyclinD3 and decreased the expression of the cell cycle inhibitor p27, a universal inhibitor of Cdk-1 and the cell cycle. We also observed that the addition of Fru-2,6-BP to HeLa cell lysates increased the phosphorylation of the Cdk-specific Thr-187 site of p27. Taken together, these observations demonstrate an unexpected role for PFKFB3 in nuclear signaling and indicate that Fru-2,6-BP may couple the activation of glucose metabolism with cell proliferation.Publication PFKFB2 regulates glycolysis and proliferation in pancreatic cancer cells(Springer, 2020-05-15) Özcan, Selahattin C.; Sarıoğlu, Aybike; Altunok, Tuğba H.; Akkoç, Ahmet; Güzel, Saime; Güler, Sabire; Imbert-Fernandez, Yoannis; Muchut, Robertino J.; Iglesias, Alberto A.; Gürpınar, Yunus; Clem, Amy L.; Chesney, Jason A.; Yalçın, Abdullah; Sarıoğlu, Aybike; Altunok, Tuğba H.; AKKOÇ, AHMET; GÜZEL, SAİME; GÜLER, SABİRE; Gürpınar, Yunus; YALÇIN, ABDULLAH; Bursa Uludağ Üniversitesi/Veteriner Fakültesi/Biyokimya Anabilim Dalı.; Bursa Uludağ Üniversitesi/Veteriner Fakültesi/Patoloji Anabilim Dalı.; Bursa Uludağ Üniversitesi/Veteriner Fakültesi/Histoloji ve Embriyoloji Anabilim Dalı.; 0000-0002-8287-6617; 0000-0003-1263-3799; 0000-0003-0796-5000; 0000-0002-7698-0872; 0000-0001-8519-8375; S-2474-2018; GCY-0775-2022; DTZ-3578-2022; AAH-4275-2021; HNI-3945-2023; ABI-4164-2020Tumor cells increase glucose metabolism through glycolysis and pentose phosphate pathways to meet the bioenergetic and biosynthetic demands of rapid cell proliferation. The family of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatases (PFKFB1-4) are key regulators of glucose metabolism via their synthesis of fructose-2,6-bisphosphate (F2,6BP), a potent activator of glycolysis. Previous studies have reported the co-expression of PFKFB isozymes, as well as the mRNA splice variants of particular PFKFB isozymes, suggesting non-redundant functions. Majority of the evidence demonstrating a requirement for PFKFB activity in increased glycolysis and oncogenic properties in tumor cells comes from studies on PFKFB3 and PFKFB4 isozymes. In this study, we show that the PFKFB2 isozyme is expressed in tumor cell lines of various origin, overexpressed and localizes to the nucleus in pancreatic adenocarcinoma, relative to normal pancreatic tissue. We then demonstrate the differential intracellular localization of two PFKFB2 mRNA splice variants and that, when ectopically expressed, cytoplasmically localized mRNA splice variant causes a greater increase in F2,6BP which coincides with an increased glucose uptake, as compared with the mRNA splice variant localizing to the nucleus. We then show that PFKFB2 expression is required for steady-state F2,6BP levels, glycolytic activity, and proliferation of pancreatic adenocarcinoma cells. In conclusion, this study may provide a rationale for detailed investigation of PFKFB2's requirement for the glycolytic and oncogenic phenotype of pancreatic adenocarcinoma cells.Item Selective inhibition of choline kinase simultaneously attenuates MAPK and PI3K/AKT signaling(Springernature, 2010-01-07) Clem, Brian F.; Makoni, S.; Clem, Amy L.; Nelson, Kristin K.; Thornburg, Joshua M.; Siow, Deanna L.; Lane, Andrew N.; Brock, Stephanie E.; Goswami, Umesh; Eaton, John W.; Telang, Sucheta; Chesney, Jason A.; Yalçın, Abdullah; Uludağ Üniversitesi/Veterinerlik Fakültesi/Temel Bilimler Bölümü.; 0000-0001-8519-8375; ABI-4164-2020; 36857831000Choline is an essential anabolic substrate for the synthesis of phospholipids. Choline kinase phosphorylates choline to phosphocholine that serves as a precursor for the production of phosphatidylcholine, the major phospholipid constituent of membranes and substrate for the synthesis of lipid signaling molecules. Nuclear magnetic resonance (NMR)-based metabolomic studies of human tumors have identified a marked increase in the intracellular concentration of phosphocholine relative to normal tissues. We postulated that the observed intracellular pooling of phosphocholine may be required to sustain the production of the pleiotropic lipid second messenger, phosphatidic acid. Phosphatidic acid is generated from the cleavage of phosphatidylcholine by phospholipase D2 and is a key activator of the mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/AKT survival signaling pathways. In this study we show that the steady-state concentration of phosphocholine is increased by the ectopic expression of oncogenic H-Ras(V12) in immortalized human bronchial epithelial cells. We then find that small interfering RNA (siRNA) silencing of choline kinase expression in transformed HeLa cells completely abrogates the high concentration of phosphocholine, which in turn decreases phosphatidylcholine, phosphatidic acid and signaling through the MAPK and PI3K/AKT pathways. This simultaneous reduction in survival signaling markedly decreases the anchorage-independent survival of HeLa cells in soft agar and in athymic mice. Last, we confirm the relative importance of phosphatidic acid for this pro-survival effect as phosphatidic acid supplementation fully restores MAPK signaling and partially rescues HeLa cells from choline kinase inhibition. Taken together, these data indicate that the pooling of phosphocholine in cancer cells may be required to provide a ready supply of phosphatidic acid necessary for the feed-forward amplification of cancer survival signaling pathways.