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 #
2R01GM088242-06
Application #
8757091
Study Section
Molecular and Integrative Signal Transduction Study Section (MIST)
Program Officer
Gaillard, Shawn R
Project Start
2009-09-01
Project End
2018-08-31
Budget Start
2014-09-01
Budget End
2015-08-31
Support Year
6
Fiscal Year
2014
Total Cost
Indirect Cost
Name
University of Rochester
Department
Pharmacology
Type
School of Medicine & Dentistry
DUNS #
City
Rochester
State
NY
Country
United States
Zip Code
14627
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
Sánchez-Fernández, Guzmán; Cabezudo, Sofía; Caballero, Álvaro et al. (2016) Protein Kinase C ζ Interacts with a Novel Binding Region of Gαq to Act as a Functional Effector. J Biol Chem 291:9513-25
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
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; 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
Papasergi, Makaía M; Patel, Bharti R; Tall, Gregory G (2015) The G protein α chaperone Ric-8 as a potential therapeutic target. Mol Pharmacol 87:52-63
Kan, Wei; Adjobo-Hermans, Merel; Burroughs, Michael et al. (2014) M3 muscarinic receptor interaction with phospholipase C β3 determines its signaling efficiency. J Biol Chem 289:11206-18
Tall, Gregory G (2013) Ric-8 regulation of heterotrimeric G proteins. J Recept Signal Transduct Res 33:139-43
Chan, Puiyee; Thomas, Celestine J; Sprang, Stephen R et al. (2013) Molecular chaperoning function of Ric-8 is to fold nascent heterotrimeric G protein * subunits. Proc Natl Acad Sci U S A 110:3794-9
Tall, Gregory G; Patel, Bharti R; Chan, Puiyee (2013) Ric-8 folding of G proteins better explains Ric-8 apparent amplification of G protein-coupled receptor signaling. Proc Natl Acad Sci U S A 110:E3148

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