The rate of de novo pyrimidine biosynthesis in mammalian cells is regulated by CAD, a large multifunctional protein that catalyzes the first three steps in the pathway. The flux through the pathway is precisely controlled and increases in tumors and in cells induced to proliferate. Carbamoyl phosphate synthetase, the CAD component that catalyzes the initial, rate limiting step, the locus of regulation, is controlled by UTP inhibition, PRPP activation, by protein kinase A (PKA) mediated phosphorylation and by phosphorylation of CAD via the MAP kinase cascade in response to EGF stimulation. The pathway is up-regulated just prior to S phase by MAP kinase mediated phosphorylation and subsequently down-regulated as the cells exit the S phase by dephosphorylation of the MAP kinase site and phosphorylation by PKA. The first Specific Aim is to elucidate the mechanism and physiological significance of three newly discovered, putative regulatory mechanisms; 1) autophosphorylation of CAD that results in large changes in catalytic activity and regulation, 2) protein kinase C that acts in concert with MAP kinase to activate CAD and 3) the regulated signaling complexes of CAD, MAP kinase, PKA and PP1 that may regulate the timing of the sequential phosphorylations. The synergistic and antagonist interactions between the individual control mechanisms that allow them to work in concert to respond to varying demands for pyrimidine nucleotides are of special interest. The second Specific Aim is to assess the physiological significance of the growth state dependent changes in CAD intracellular dynamics. Microscopic and biochemical approaches have shown that an appreciable fraction of the CAD phosphorylated by MAP kinase is localized in the nucleus and that a fraction of the CAD in the cytosol is associated with the microtubules. The postulated direct transfer of dihydroorotate to the mitochondrial dehydrogenase, catalyzing the next step in the pathway, will be investigated in vivo using a histochemical assay. Fluorescence microscopy of live cells in conjunction with mutants and constructs that target CAD to different cellular compartments will be used to elucidate the functional significance of CAD nucleocytoplasmic dynamics. The overall objective is to develop a comprehensive model for the regulation of the pathway in normal and neoplastic cells taking into consideration the integration of signals and the interplay of these diverse regulatory mechanisms. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM060371-07
Application #
7369817
Study Section
Special Emphasis Panel (ZRG1-BIO (01))
Program Officer
Jones, Warren
Project Start
2000-02-01
Project End
2012-02-29
Budget Start
2008-03-01
Budget End
2012-02-29
Support Year
7
Fiscal Year
2008
Total Cost
$227,730
Indirect Cost
Name
Eastern Michigan University
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
623664018
City
Ypsilanti
State
MI
Country
United States
Zip Code
48197
Hervé, Guy; Evans, Hedeel Guy; Fernado, Roshini et al. (2017) Activation of Latent Dihydroorotase from Aquifex aeolicus by Pressure. J Biol Chem 292:629-637
Evans, Hedeel Guy; Fernando, Roshini; Vaishnav, Asmita et al. (2014) Intersubunit communication in the dihydroorotase-aspartate transcarbamoylase complex of Aquifex aeolicus. Protein Sci 23:100-9
Edwards, Brian F P; Fernando, Roshini; Martin, Philip D et al. (2013) The mononuclear metal center of type-I dihydroorotase from Aquifex aeolicus. BMC Biochem 14:36
Popa, Elena; Perera, Nirosha; Kibédi-Szabó, Csaba Z et al. (2012) The smallest active carbamoyl phosphate synthetase was identified in the human gut archaeon Methanobrevibacter smithii. J Mol Microbiol Biotechnol 22:287-99
Zhang, Pengfei; Martin, Philip D; Purcarea, Cristina et al. (2009) Dihydroorotase from the hyperthermophile Aquifex aeolicus is activated by stoichiometric association with aspartate transcarbamoylase and forms a one-pot reactor for pyrimidine biosynthesis. Biochemistry 48:766-78
Sigoillot, Frederic D; Kotsis, Damian H; Masko, Elizabeth M et al. (2007) Protein kinase C modulates the up-regulation of the pyrimidine biosynthetic complex, CAD, by MAP kinase. Front Biosci 12:3892-8
Kothe, Michael; Purcarea, Cristina; Guy, Hedeel I et al. (2005) Direct demonstration of carbamoyl phosphate formation on the C-terminal domain of carbamoyl phosphate synthetase. Protein Sci 14:37-44
Martin, Philip D; Purcarea, Cristina; Zhang, Pengfei et al. (2005) The crystal structure of a novel, latent dihydroorotase from Aquifex aeolicus at 1.7A resolution. J Mol Biol 348:535-47
Sigoillot, Frederic D; Kotsis, Damian H; Serre, Valerie et al. (2005) Nuclear localization and mitogen-activated protein kinase phosphorylation of the multifunctional protein CAD. J Biol Chem 280:25611-20
Sigoillot, Frederic D; Sigoillot, Severine M; Guy, Hedeel I (2004) Breakdown of the regulatory control of pyrimidine biosynthesis in human breast cancer cells. Int J Cancer 109:491-8

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