title: Activation of the regulator of G protein signaling 14-Gαi1-GDP signaling complex is regulated by resistance to inhibitors of cholinesterase-8A.
abstract: RGS14 is a brain scaffolding protein that integrates G protein and MAP kinase signaling pathways. Like other RGS proteins, RGS14 is a GTPase activating protein (GAP) that terminates Gαi/o signaling. Unlike other RGS proteins, RGS14 also contains a G protein regulatory (also known as GoLoco) domain that binds Gαi1/3-GDP in cells and in vitro. Here we report that Ric-8A, a nonreceptor guanine nucleotide exchange factor (GEF), functionally interacts with the RGS14-Gαi1-GDP signaling complex to regulate its activation state. RGS14 and Ric-8A are recruited from the cytosol to the plasma membrane in the presence of coexpressed Gαi1 in cells, suggesting formation of a functional protein complex with Gαi1. Consistent with this idea, Ric-8A stimulates dissociation of the RGS14-Gαi1-GDP complex in cells and in vitro using purified proteins. Purified Ric-8A stimulates dissociation of the RGS14-Gαi1-GDP complex to form a stable Ric-8A-Gαi complex in the absence of GTP. In the presence of an activating nucleotide, Ric-8A interacts with the RGS14-Gαi1-GDP complex to stimulate both the steady-state GTPase activity of Gαi1 and binding of GTP to Gαi1. However, sufficiently high concentrations of RGS14 competitively reverse these stimulatory effects of Ric-8A on Gαi1 nucleotide binding and GTPase activity. This observation correlates with findings that show RGS14 and Ric-8A share an overlapping binding region within the last 11 amino acids of Gαi1. As further evidence that these proteins are functionally linked, native RGS14 and Ric-8A coexist within the same hippocampal neurons. These findings demonstrate that RGS14 is a newly appreciated integrator of unconventional Ric-8A and Gαi1 signaling.
authors.affiliation: Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, United States.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Vellano
authors.forename: Feng-Jue
authors.initials: FJ
authors.lastname: Shu
authors.forename: Suneela
authors.initials: S
authors.lastname: Ramineni
authors.forename: Cindee K
authors.initials: CK
authors.lastname: Yates
authors.forename: Gregory G
authors.initials: GG
authors.lastname: Tall
authors.forename: John R
authors.initials: JR
authors.lastname: Hepler
mesh_terms: D000818:Animals; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D020710:RGS Proteins; C491399:Rgs14 protein, mouse; C485884:Ric8a protein, mouse; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D019206:GTP-Binding Protein alpha Subunits, Gi-Go