The heterotrimeric G protein Gq regulates neuromuscular control as well as platelet activation, blood pressure and cardiac function, and plays a central role in the development of hypertension and cardiac hypertrophy. Activated G?q directly interacts with proteins that have been shown to be important for these processes, including the effector enzymes phospholipase C2 (PLC2) and p63RhoGEF, and the GTPase activating protein regulator of G protein signaling protein 2 (RGS2). We recently determined structures of the autoinhibited catalytic core of invertebrate PLC2 and the G?q -p63RhoGEF-RhoA complex, which led to dramatic new insights into how G?q regulates effector activity, and of the RGS2-G1q complex, the first structure of an RGS protein in complex with a member of the G1q subfamily.
In Aim 1, we will confirm our model for how G?q allosterically regulates PLC2 in living cells and in the model organism C. elegans, and investigate how the C-terminal regulatory region of PLC23 enhances catalysis and affinity for G1q using functional studies and X-ray crystallographic and electron microscopic analyses of full-length PLC2 in complex with G1q.
In Aim 2, we determine the autoinhibited basal structure of p63RhoGEF by solution NMR and assess how its structure is perturbed upon complex formation with G?q which will help fully describe its mechanism of activation.
In Aim 3, we will determine the role of unique interactions formed between RGS2 and the helical domain of G?q and test their contribution to the selective regulation of G1q by RGS2. Collectively, our experiments are expected to reveal the molecular basis for how G?q activates its effectors, and how RGS2 appears to have uniquely evolved to regulate G?q . This knowledge is essential for understanding fundamental processes that underlie cardiac and neuromuscular function, and for developing new approaches to treat cardiovascular disease.

Public Health Relevance

The interactions of G?q with PLC2, GRK2, p63RhoGEF, and RGS2 are all strongly linked to cardiovascular physiology and/or disease in humans, and to neurotransmission at neuromuscular junctions in animal models. Our studies will shed significant light on the molecular processes that regulate cardiovascular physiology and potentially open new avenues for therapeutic intervention.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL086865-07
Application #
8589422
Study Section
Biochemistry and Biophysics of Membranes Study Section (BBM)
Program Officer
Adhikari, Bishow B
Project Start
2007-01-15
Project End
2015-11-30
Budget Start
2013-12-01
Budget End
2014-11-30
Support Year
7
Fiscal Year
2014
Total Cost
$354,627
Indirect Cost
$122,877
Name
University of Michigan Ann Arbor
Department
Pharmacology
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
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Taylor, Veronica G; Bommarito, Paige A; Tesmer, John J G (2016) Structure of the Regulator of G Protein Signaling 8 (RGS8)-Gαq Complex: MOLECULAR BASIS FOR Gα SELECTIVITY. J Biol Chem 291:5138-45
Tesmer, John J G (2016) Hitchhiking on the heptahelical highway: structure and function of 7TM receptor complexes. Nat Rev Mol Cell Biol 17:439-50
Yang, Pei; Homan, Kristoff T; Li, Yaoxin et al. (2016) Effect of Lipid Composition on the Membrane Orientation of the G Protein-Coupled Receptor Kinase 2-Gβ1γ2 Complex. Biochemistry 55:2841-8
Li, Lingyong; Homan, Kristoff T; Vishnivetskiy, Sergey A et al. (2015) G Protein-coupled Receptor Kinases of the GRK4 Protein Subfamily Phosphorylate Inactive G Protein-coupled Receptors (GPCRs). J Biol Chem 290:10775-90
Homan, Kristoff T; Tesmer, John J G (2015) Molecular basis for small molecule inhibition of G protein-coupled receptor kinases. ACS Chem Biol 10:246-56
Schumacher, Sarah M; Gao, Erhe; Zhu, Weizhong et al. (2015) Paroxetine-mediated GRK2 inhibition reverses cardiac dysfunction and remodeling after myocardial infarction. Sci Transl Med 7:277ra31

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