Modulation of intracellular cyclic AMP (cAMP) levels has been shown to impact on a number of cellular processes underlying changes in protein phosphorylation state, regulation of ion channel conductance, and gene expression. The concentration of intracellular cAMP is principally controlled at the level of its synthesis through the hormonal regulation of adenylyl cyclase, the enzyme catalyzing the conversion of ATP to cAMP. Adenylyl cyclase activity is regulated by hormones that couple through heterotrimeric G proteins that when activated, dissociate into alpha and beta-gamma dimers; both alpha and beta-gamma are capable of regulating the cyclase. Nine isoforms of adenylyl cyclase, encoded by separate genes, have been identified to date, and have been shown to be regulated by individual G protein subunits in an isoform-specific fashion. An additional property of adenylyl cyclases is their ability to integrate multiple simultaneous hormonal inputs. The importance of proper adenylyl cyclase regulation is underscored by the identification of mutations in the receptor and G protein components found in a number of human disease states such as hyperfunctioning thyroid adenomas, pseudohypoparathyroidism and McCune-Albright syndrome. In the first aim the principal investigator proposes to examine the structural basis for the type-specific regulation of adenylyl cyclases by G protein beta-gamma and inhibitory Gi-alpha subunits. In the second aim, the principal investigator will use genetic and biochemical approaches to identify and characterize activating mutant alleles of adenylyl cyclase. In the third aim, he will examine the behavior of adenylyl cyclase mutants in cell culture systems, and determine the consequences of these mutations on intracellular cAMP regulation. In the final aim, the principal investigator will examine the possible involvement of adenylyl cyclase mutations in pathophysiological states and examine the oncogenic potential of activating mutant adenylyl cyclase alleles. These proposed studies should provide a significant understanding of the mechanisms underlying the regulation of adenylyl cyclases and in general, G protein-coupled effector systems, and will provide the basis for elucidating possible defects in adenylyl cyclase structure or function as the basis for abnormal signal transduction in human disease states.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
7R01GM053645-06
Application #
6490093
Study Section
Biochemistry Study Section (BIO)
Program Officer
Jones, Warren
Project Start
1996-02-01
Project End
2004-12-31
Budget Start
2002-01-01
Budget End
2002-12-31
Support Year
6
Fiscal Year
2002
Total Cost
$240,813
Indirect Cost
Name
University of Texas Sw Medical Center Dallas
Department
Pharmacology
Type
Schools of Medicine
DUNS #
City
Dallas
State
TX
Country
United States
Zip Code
75390
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Clapp, Peter; Capper, Austin B; Taussig, Ronald (2002) Genetic selection of regulatory mutants of mammalian adenylyl cyclases. Methods Enzymol 345:241-51
Scott, J K; Huang, S F; Gangadhar, B P et al. (2001) Evidence that a protein-protein interaction 'hot spot' on heterotrimeric G protein betagamma subunits is used for recognition of a subclass of effectors. EMBO J 20:767-76
Watts, V J; Taussig, R; Neve, R L et al. (2001) Dopamine D2 receptor-induced heterologous sensitization of adenylyl cyclase requires Galphas: characterization of Galphas-insensitive mutants of adenylyl cyclase V. Mol Pharmacol 60:1168-72
Hou, Y; Chang, V; Capper, A B et al. (2001) G Protein beta subunit types differentially interact with a muscarinic receptor but not adenylyl cyclase type II or phospholipase C-beta 2/3. J Biol Chem 276:19982-8
Shoshani, I; Taussig, R; Iyengar, R et al. (2000) Synthesis and use of 3'-(azidoiodosalicyl) derivatives of 2', 5'-dideoxyadenosine as photoaffinity ligands for adenylyl cyclase. Arch Biochem Biophys 376:221-8
Zimmermann, G; Zhou, D; Taussig, R (1999) Activating mutation of adenylyl cyclase reverses its inhibition by G proteins. Mol Pharmacol 56:895-901
Lan, K L; Sarvazyan, N A; Taussig, R et al. (1998) A point mutation in Galphao and Galphai1 blocks interaction with regulator of G protein signaling proteins. J Biol Chem 273:12794-7
Taussig, R; Zimmermann, G (1998) Type-specific regulation of mammalian adenylyl cyclases by G protein pathways. Adv Second Messenger Phosphoprotein Res 32:81-98
Zimmermann, G; Zhou, D; Taussig, R (1998) Genetic selection of mammalian adenylyl cyclases insensitive to stimulation by Gsalpha. J Biol Chem 273:6968-75

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