Ric-8A and Ric-8B are positive regulators of heterotrimeric G protein a subunit function. We have recently defined the cellular action of Ric-8 proteins towards Ga subunits. Ric-8 proteins act as molecular chaperones of nucleotide-free Ga conformations during biosynthetic Ga protein folding. In cells in which Ric-8 genes are deleted, cellular abundances of subsets of Ga subunits were reduced by 95%. Ric-8 proteins also exhibit in vitro guanine nucleotide exchange stimulatory activity towards Ga subunits, and we now believe this to be an in vitro phenomenon stemming from the capacity of Ric-8 to induce a partially folded Ga state that has reduced affinity for GDP. We will develop our hypothesis that Ric-8 proteins are Ga subunit molecular chaperones and investigate the mechanisms by which Ric-8 proteins work with other cellular chaperones including the TRiC/CCT (Chaperonin) complex and HSC70/90 systems to fold individual Ga subunits. We have preliminary evidence that there are complex rules and unique chaperone requirements of individual Ga subunits. We will then test a hypothesis that mouse tissue-specific Ric-8A gene deletion can genetically suppress oncogenic G protein or overactive GPCR-driven cancers. Two mouse melanoma models will be used in which GNAQ/11-Q209L (constitutively-active) alleles are the oncogenic driver mutations of metastatic ocular melanoma, and ectopic mGluR5 expression from a melanocyte promoter elicited robust melanoma. We hypothesize that melanocyte mGluR5 inappropriately activates Gq/11 to promote melanoma. Upon proof-of-concept that Ric-8 deletion will suppress the actions of these oncogenes by reducing Gaq/11 cellular abundances, we will perform screens to identify small molecule inhibitors of Ric-8 and G protein interactions. Our goal is to develop Ric-8 inhibitors as a means to indirectly block G protein disease signaling by reducing the abundance of (mutant) Ga subunits folded by Ric-8. Ric-8 inhibitors may prove efficacious against oncogenic G protein diseases and/or as augmentation therapies for existing GPCR therapeutics. We will also conduct a small project to investigate Ric-8A regulation by phosphorylation events and 14-3-3 binding to Ric-8A.

Public Health Relevance

Ric-8 proteins are newly defined regulators of heterotrimeric G protein a subunit biosynthetic production. G proteins transduce drug, hormone, and neurotransmitter influence into physiological cellular actions. The mechanisms by which Ric-8 proteins aid G protein production will be investigated and means of blocking Ric-8 proteins as a way to reduce G protein abundances in pathophysiological states will be explored.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
7R01GM088242-08
Application #
9325285
Study Section
Molecular and Integrative Signal Transduction Study Section (MIST)
Program Officer
Maas, Stefan
Project Start
2009-09-01
Project End
2018-08-31
Budget Start
2016-07-01
Budget End
2016-08-31
Support Year
8
Fiscal Year
2015
Total Cost
$70,263
Indirect Cost
$24,932
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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Schenk, Noah A; Dahl, Peter J; Hanna 4th, Michael G et al. (2018) A simple supported tubulated bilayer system for evaluating protein-mediated membrane remodeling. Chem Phys Lipids 215:18-28
Tourdot, Benjamin E; Stoveken, Hannah; Trumbo, Derek et al. (2018) Genetic Variant in Human PAR (Protease-Activated Receptor) 4 Enhances Thrombus Formation Resulting in Resistance to Antiplatelet Therapeutics. Arterioscler Thromb Vasc Biol 38:1632-1643
Papasergi-Scott, Makaía M; Stoveken, Hannah M; MacConnachie, Lauren et al. (2018) Dual phosphorylation of Ric-8A enhances its ability to mediate G protein ? subunit folding and to stimulate guanine nucleotide exchange. Sci Signal 11:
Carr 3rd, Richard; Koziol-White, Cynthia; Zhang, Jie et al. (2016) Interdicting Gq Activation in Airway Disease by Receptor-Dependent and Receptor-Independent Mechanisms. Mol Pharmacol 89:94-104
Stoveken, Hannah M; Bahr, Laura L; Anders, M W et al. (2016) Dihydromunduletone Is a Small-Molecule Selective Adhesion G Protein-Coupled Receptor Antagonist. Mol Pharmacol 90:214-24
Sánchez-Fernández, Guzmán; Cabezudo, Sofía; Caballero, Álvaro et al. (2016) Protein Kinase C ? Interacts with a Novel Binding Region of G?q to Act as a Functional Effector. J Biol Chem 291:9513-25
Patel, B R; Tall, G G (2016) Ric-8A gene deletion or phorbol ester suppresses tumorigenesis in a mouse model of GNAQ(Q209L)-driven melanoma. Oncogenesis 5:e236
Papasergi, Makaía M; Patel, Bharti R; Tall, Gregory G (2015) The G protein ? chaperone Ric-8 as a potential therapeutic target. Mol Pharmacol 87:52-63
Stoveken, Hannah M; Hajduczok, Alexander G; Xu, Lei et al. (2015) Adhesion G protein-coupled receptors are activated by exposure of a cryptic tethered agonist. Proc Natl Acad Sci U S A 112:6194-9

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