In Silico Design of Novel RGS2–G_alpha-q Interaction Inhibitors with Anticancer Activity

Regulators of G-protein signaling (RGS) are a family of approximately 30 proteins that bind to and deactivate the alpha subunits of G-proteins (G_α) by accelerating their GTP hydrolysis rates, which terminates G-protein coupled receptor (GPCR) signaling. Thus, RGS proteins are essential in regulating GPCR signaling, and most members are implicated as critical nodes in human diseases such as hypertension, depression, and others. Regulator of G-protein signaling 2 (RGS2), a member of the R4 family of RGS proteins, is overexpressed in many solid breast cancers, and its levels in prostate cancer significantly correlate with the metastatic stage and poor prognosis. We sought to develop RGS2 inhibitors as potential chemotherapeutic agents utilizing structure-based drug design approaches. Available structures of the RGS2-G_α complex were used to extract a pharmacophore model for searching chemical databases. Docking of identified hits to RGS2 as well as other RGS structures was used to screen the hits for potent and selective RGS2 inhibitors. Whole cell assays showed the top 10 ranking compounds, AJ-1-AJ-10, to inhibit RGS2-G_αq interactions. Differential scanning fluorimetry showed AJ-3 to bind RGS2 but not G_αq. All 10 compounds inhibited the growth of several RGS2 expressing cancers in cell culture assays. In addition, AJ-3 inhibited the migration of LNCaP prostate cancer cells in wound healing assays. This is the first group of RGS2 inhibitors identified by structure-based approaches and that show anticancer activity. These results highlight the potential RGS2 inhibitors have to be a new class of chemotherapeutic agents.