Discovery and characterization of the first cellularly active, non‐covalent inhibitor of a regulator of G protein signaling protein (RGS protein) (1054.10)

Abstract

Regulator of G‐Protein Signaling (RGS) proteins are known to regulate the complex signaling pathways activated by GPCRs. Recent studies have implicated RGS proteins in the development and progression of pathologies, including some cancers. Over the past 10 years there have been several attempts to modulate these RGS proteins with all reported compounds working through a covalent Cysteine modification. These attempts have proven useful and laid the foundation for successful targeting of RGS proteins.Recently, our lab has focused on RGS17. This protein has been implicated in the growth, proliferation and metastasis of prostate cancer as well as small‐cell and non‐small cell lung cancers. We implemented a novel high‐throughput screening campaign to determine the first Gαo: RGS17 protein: protein interaction (ppi) inhibitors. This campaign yielded three compounds (UI5, UI1590 and UI1956) that inhibited the Gαo: RGS17 ppi in both biochemical and activity assays, while exhibiting single digit μΜ to nM dissociation constants by Isothermal Titration Calorimetry. These newly discovered inhibitors have cellular activity, disrupting RGS17 membrane localization in HEK293 cells down to 10 μM. Most importantly, UI1956 was specific for RGS17, as it had no effect on the ppi of RGS4 and RGS8 when incubated with Gαo. Finally, UI5, UI1590 and UI1956 did not covalently modify RGS17 as determined by mass spectrometry. Research is supported by American Foundation for Pharmaceutical Education (AFPE), The University of Iowa’s Center for Biocatalysis and Bioprocessing (5T32GM008365‐23) and The National Institutes of Health (R01CA160470).