Cell surface receptors coupled to the heterotrimeric GTP-binding proteins are universally responsible for the transmembrane transmission of extracellular messengers such as hormones, neurotransmitters and a variety of sensory stimuli. Because of this direct involvement in the regulation of the most crucial cellular functions, G-protein coupled receptors (GPCRs) are among the most important targets of therapeutic intervention. It's estimated that about 50% of drugs in use act on GPCRs. Thus, understanding of the receptor and the G- protein functions at the molecular level is among the highest priorities of public health research. Several competing models aim at describing the universal mechanism of G- protein activation by GPCRs, but none has presented compelling and conclusive experimental evidence so far. HYPOTHESIS: G-protein 23-subunit complex is a key molecular switch at the center of the gear-shift model of G-protein activation. We will test this hypothesis using the prototypical GPCR rhodopsin (R) and the G-protein transducin (Gt) responsible for phototransduction in retinal rod cells as a model system. Three interconnected Specific Aims will test various aspects of the hypothesis, such as questions of the molecular organization of the receptor- G-protein complex, the high-resolution picture of the receptor-G-protein interface, the mechanism of signal transfer from the receptor, and the roles of individual G- protein subunits, especially the G23 subunit complex, in this dynamic process. This project aims at understanding the universal principles underlying cell- to-cell communications and cellular responses to a variety of sensory stimuli. Several competing theories describing these basic molecular mechanisms will be tested to gain insights into the inner workings of cell surface receptor proteins and specific protein-protein interactions. Because almost half of all therapeutics on the market today target these signaling pathways, knowledge obtained as a result of these studies will be essential in new drug design and fighting a wide range of diseases such as heart problems, asthma and vision disorders.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM063203-09
Application #
8138391
Study Section
Biochemistry and Biophysics of Membranes Study Section (BBM)
Program Officer
Flicker, Paula F
Project Start
2001-04-01
Project End
2014-08-31
Budget Start
2011-09-01
Budget End
2014-08-31
Support Year
9
Fiscal Year
2011
Total Cost
$273,742
Indirect Cost
Name
Saint Louis University
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
050220722
City
Saint Louis
State
MO
Country
United States
Zip Code
63103
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Kolesnikov, Alexander V; Rikimaru, Loryn; Hennig, Anne K et al. (2011) G-protein betagamma-complex is crucial for efficient signal amplification in vision. J Neurosci 31:8067-77
Taylor, Christina M; Rockweiler, Nicole B; Liu, Cassie et al. (2010) Using ligand-based virtual screening to allosterically stabilize the activated state of a GPCR. Chem Biol Drug Des 75:325-32
Van Eps, Ned; Anderson, Lori L; Kisselev, Oleg G et al. (2010) Electron paramagnetic resonance studies of functionally active, nitroxide spin-labeled peptide analogues of the C-terminus of a G-protein alpha subunit. Biochemistry 49:6877-86
Kisselev, Oleg G; Downs, Maureen A (2006) Rhodopsin-interacting surface of the transducin gamma subunit. Biochemistry 45:9386-92
Downs, Maureen A; Arimoto, Rieko; Marshall, Garland R et al. (2006) G-protein alpha and beta-gamma subunits interact with conformationally distinct signaling states of rhodopsin. Vision Res 46:4442-8
Kisselev, Oleg G (2005) Focus on molecules: rhodopsin. Exp Eye Res 81:366-7
Kisselev, Oleg G; Downs, Maureen A; McDowell, J Hugh et al. (2004) Conformational changes in the phosphorylated C-terminal domain of rhodopsin during rhodopsin arrestin interactions. J Biol Chem 279:51203-7
Kisselev, Oleg G; Downs, Maureen A (2003) Rhodopsin controls a conformational switch on the transducin gamma subunit. Structure 11:367-73