Members of a family of guanine nucleotide-binding regulatory proteins (G proteins) are responsible for transmission of information from many membrane-bound receptors for hormones, neurotransmitters, autacoids, and physical stimuli to their intracellular effectors. Although there are several such pathways, the best studied are those for dual (stimulatory and inhibitory) regulation of adenylyl cyclase and for light-stimulated hydrolysis of cyclic GMP in retinal rods and cones. The broad gaol of the research proposed in this application is to elucidate molecular mechanisms of transmembrane signaling in pathways that include such G proteins as crucial regulatory elements.
Specific aims can be organized with regard to the G protein or effector system to be investigated. Gs is the G protein responsible for stimulation of adenylyl cyclase activity and activation of dihydropyridine-sensitive Ca2+ channels. The alpha subunit of Gs has been synthesized in E. coli and characterized. Large amounts of recombinant Gs alpha have been purified to homogeneity for the purpose of collaborative attempts to crystallize the protein and determine its three dimensional structure. The nature of covalent modifications of Gs alpha thought to be necessary for high-affinity interactions between the G protein and its effectors will also explored. The Gi/Go family of G proteins will be studied as homogeneous products after expression in E. coli. Their basic biochemical properties (e.g., kinetics of guanine nucleotide binding and hydrolysis) will be defined, as will the specificity of their interactions with receptors (e.g., alpha and beta adrenergic) and effectors (e.g., adenylyl cyclase, K+ channels, Ca2+ channels). The specificity and mechanisms of interactions of these proteins with receptors and effectors will also be studied by expression of various mutant Gi alpha and Go alpha subunits in appropriate cultured cell lines. The significance of amino-terminal myristoylation of these alpha subunits will also be investigated. Gz is a newly appreciated G protein with unique structural features. Its biological role is unknown. Gz will be purified from bovine brain and characterized; Gz alpha will also be expressed in E. coli. Biochemical and molecular biological approaches will be taken to elucidate its functions. Newly clone cDNAs that encode individual forms of adenylyl cyclase will be expressed in appropriate cell systems, and the properties of the enzymes that they encode will be determined. Antibodies will be raised to individual forms of the protein. The functional domains of this complex membrane-bound enzyme will be studied. The significance of the """"""""channel- like"""""""" topology of adenylyl cyclase will be investigated.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Method to Extend Research in Time (MERIT) Award (R37)
Project #
Application #
Study Section
Pharmacology A Study Section (PHRA)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Texas Sw Medical Center Dallas
Schools of Medicine
United States
Zip Code
Thomas, Celestine J; Tall, Gregory G; Adhikari, Anirban et al. (2008) Ric-8A catalyzes guanine nucleotide exchange on G alphai1 bound to the GPR/GoLoco exchange inhibitor AGS3. J Biol Chem 283:23150-60
Kumar, Premlata; Wu, Qian; Chambliss, Ken L et al. (2007) Direct Interactions with G alpha i and G betagamma mediate nongenomic signaling by estrogen receptor alpha. Mol Endocrinol 21:1370-80
Gibson, Scott K; Gilman, Alfred G (2006) Gialpha and Gbeta subunits both define selectivity of G protein activation by alpha2-adrenergic receptors. Proc Natl Acad Sci U S A 103:212-7
Krumins, Andrejs M; Gilman, Alfred G (2006) Targeted knockdown of G protein subunits selectively prevents receptor-mediated modulation of effectors and reveals complex changes in non-targeted signaling proteins. J Biol Chem 281:10250-62
Tall, Gregory G; Gilman, Alfred G (2005) Resistance to inhibitors of cholinesterase 8A catalyzes release of Galphai-GTP and nuclear mitotic apparatus protein (NuMA) from NuMA/LGN/Galphai-GDP complexes. Proc Natl Acad Sci U S A 102:16584-9
Malik, Sundeep; Ghosh, Mousumi; Bonacci, Tabetha M et al. (2005) Ric-8 enhances G protein betagamma-dependent signaling in response to betagamma-binding peptides in intact cells. Mol Pharmacol 68:129-36
Krumins, Andrejs M; Barker, Sheryll A; Huang, Chunfa et al. (2004) Differentially regulated expression of endogenous RGS4 and RGS7. J Biol Chem 279:2593-9
Chen, Zhu; Raman, Malavika; Chen, Linda et al. (2003) TAO (thousand-and-one amino acid) protein kinases mediate signaling from carbachol to p38 mitogen-activated protein kinase and ternary complex factors. J Biol Chem 278:22278-83
Tall, Gregory G; Krumins, Andrejs M; Gilman, Alfred G (2003) Mammalian Ric-8A (synembryn) is a heterotrimeric Galpha protein guanine nucleotide exchange factor. J Biol Chem 278:8356-62
Hooks, Shelley B; Waldo, Gary L; Corbitt, James et al. (2003) RGS6, RGS7, RGS9, and RGS11 stimulate GTPase activity of Gi family G-proteins with differential selectivity and maximal activity. J Biol Chem 278:10087-93

Showing the most recent 10 out of 136 publications