The aim of this research project is to understand the biochemical events governing metabolite transport in mammalian cells. We plan to describe the molecular properties of plasma membrane components which are required for transport and also to determine how the activity of these components is regulated in response to the metabolic needs of the cell. Our approach is to study the mechanism of purine base and nucleoside transport in Chinese hamster lung fibroblasts growing in tissue culture. Both wild-type cells and mutant clones which are resistant to 8-azaguanine (8-AG) and 5-bromo-2-deoxyuridine (BUdR) will be used in these experiments. Clones whose drug resistance is due to loss of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) will be employed to examine parameters of hypoxanthine exodus. Resistant mutants with normal phosphorylation and phosphoribosylation will be examined for defects in base and nucleoside transport. The interaction of bases and nucleosides for transport sites on the membrane will be studied in 8-AGr, BUdRr double mutants lacking both HGPRT and thymidine kinase. A rapid sampling method for transport assays using fibroblast monolayers will allow accurate determination of kinetic parameters. In addition, we plan to develop a continuous assay method for hypoxanthine transport in erythrocyte ghosts and phospholipid vesicles. This investigation depends on biochemically and genetically defined systems which should allow us to identify and study the membrane proteins that regulate purine utilization in mammalian cells. We believe that this will be a significant step towards understanding disorders which alter purine pools such as Lesch-Nyhan syndrome, gouty arthritis, and inherited immunodeficiency diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK017436-15
Application #
3225750
Study Section
Neurological Sciences Subcommittee 1 (NLS)
Project Start
1977-01-01
Project End
1990-06-30
Budget Start
1989-01-01
Budget End
1990-06-30
Support Year
15
Fiscal Year
1989
Total Cost
Indirect Cost
Name
Baylor College of Medicine
Department
Type
Schools of Medicine
DUNS #
074615394
City
Houston
State
TX
Country
United States
Zip Code
77030
Tehrani, M H; Barnes Jr, E M (1997) Sequestration of gamma-aminobutyric acidA receptors on clathrin-coated vesicles during chronic benzodiazepine administration in vivo. J Pharmacol Exp Ther 283:384-90
Tehrani, M H; Tate, C A; al-Dahan, M I (1995) Age-related levels of GABA/benzodiazepine binding sites in cerebrum of F-344 rats: effects of exercise. Neurobiol Aging 16:199-204
Tehrani, M H; Barnes Jr, E M (1995) Reduced function of gamma-aminobutyric acidA receptors in tottering mouse brain: role of cAMP-dependent protein kinase. Epilepsy Res 22:13-21
Tehrani, M H; Barnes Jr, E M (1994) GABAA receptors in mouse cortical homogenates are phosphorylated by endogenous protein kinase A. Brain Res Mol Brain Res 24:55-64
Calkin, P A; Barnes Jr, E M (1994) gamma-Aminobutyric acid-A (GABAA) agonists down-regulate GABAA/benzodiazepine receptor polypeptides from the surface of chick cortical neurons. J Biol Chem 269:1548-53
Baumgartner, B J; Harvey, R J; Darlison, M G et al. (1994) Developmental up-regulation and agonist-dependent down-regulation of GABAA receptor subunit mRNAs in chick cortical neurons. Brain Res Mol Brain Res 26:9-17
Calkin, P A; Baumgartner, B J; Barnes Jr, E M (1994) Agonist administration in ovo down-regulates cerebellar GABAA receptors in the chick embryo. Brain Res Mol Brain Res 26:18-25
Tehrani, M H; Barnes Jr, E M (1993) Identification of GABAA/benzodiazepine receptors on clathrin-coated vesicles from rat brain. J Neurochem 60:1755-61
Tehrani, M H; Barnes Jr, E M (1991) Agonist-dependent internalization of gamma-aminobutyric acidA/benzodiazepine receptors in chick cortical neurons. J Neurochem 57:1307-12
Tehrani, M H; Hablitz, J J; Barnes Jr, E M (1989) cAMP increases the rate of GABAA receptor desensitization in chick cortical neurons. Synapse 4:126-31

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