Document Type
Article
Publication Date
3-19-2025
Abstract
Heterotrimeric G proteins are stimulated under normal circumstances by G protein-coupled receptors to promote downstream intracellular signaling. Mutations can occur in αq at glutamine 209 (Q209) that cause constitutive, G protein-coupled receptor independent signaling due to disruption of GTPase activity. Specifically, Q209L/P mutations are oncogenic drivers of uveal melanoma. YM-254890 (YM) has been shown to selectively inhibit both WT and constitutively active (CA) αqQ209L/P by preventing the release of GDP and exchange for GTP, thereby halting downstream signaling. Because αqQL/P are thought to be primarily GTP-bound and GTPase deficient, the current mechanistic understanding of YM inhibition needs further investigation to clarify how a GDP-dissociation inhibitor could potently inhibit these oncogenic mutants. Here, we expand on the current knowledge of CA αq cellular regulation by demonstrating a direct role for the αq chaperone and guanine nucleotide exchange factor Ric-8A in YM sensitivity. Through signaling assays in RIC-8A KO cells, we found that myristoylated αqQL/P mutants (αqAG-QL/P), previously demonstrated to be YM-resistant, became YM-sensitive, and this was reversed by reintroduction of Ric-8A. Additionally, αqQL demonstrated increased YM sensitivity in the absence of Ric-8A, which was directly altered by the reintroduction of Ric-8A. Pull-down and BRET assays with the RGS-homology domain of GRK2, which can only bind activated αq, further demonstrated that Ric-8A expression enhances activation of αq, its ability to bind effectors, and therefore its ability to signal. With the understanding of YM acting as a GDP-dissociation inhibitor, we propose that Ric-8A hinders YM inhibitory effects by promoting GTP-bound, activated αqQL/P.
Recommended Citation
Dwyer, Morgan; Luo, Jiansong; Todd, Tyson; Blumer, Kendall; Tall, Gregory; and Wedegaertner, Philip, "The Guanine Nucleotide Exchange Factor Ric-8A Regulates the Sensitivity of Constitutively Active Gαq to the Inhibitor YM-254890" (2025). Department of Biochemistry and Molecular Biology Faculty Papers. Paper 278.
https://jdc.jefferson.edu/bmpfp/278
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
PubMed ID
40118458
Language
English
Included in
Biochemistry Commons, Biological Phenomena, Cell Phenomena, and Immunity Commons, Molecular Biology Commons, Polycyclic Compounds Commons
Comments
This article is the author's final published version in Journal of Biological Chemistry, Volume 301, Issue 5, 2025, Article number 108426.
The published version is available at https://doi.org/10.1016/j.jbc.2025.108426.
Copyright © 2025 THE AUTHORS