PT  - JOURNAL ARTICLE
AU  - David Roman
AU  - Levi L Blazer
AU  - C. Aaron Monroy
AU  - Richard R. Neubig
TI  - Allosteric Inhibition of the RGS-Gα Protein-Protein Interaction by CCG-4986
AID  - 10.1124/mol.109.063388
DP  - 2010 Jun 07
TA  - Molecular Pharmacology
PG  - mol.109.063388
4099  - http://molpharm.aspetjournals.org/content/early/2010/06/07/mol.109.063388.short
4100  - http://molpharm.aspetjournals.org/content/early/2010/06/07/mol.109.063388.full
AB  - Regulator of G protein signaling (RGS) proteins act to temporally modulate the activity of G protein subunits following G protein coupled receptor (GPCR) activation. RGS proteins exert their effect by directly binding to the activated Gα subunit of the G protein, catalyzing the accelerated hydrolysis of GTP and returning the G protein to its inactive, heterotrimeric form. In previous studies, we have sought to inhibit this GTPase Accelerating (GAP) activity of the RGS protein using small molecules. In this study, we investigated the mechanism of CCG-4986, a previously reported small molecule RGS inhibitor. Here we find that CCG-4986 inhibits RGS4 function through the covalent modification of two spatially distinct cysteine residues on RGS4. We confirm that modification of C132, located near the RGS/Gα interaction surface modestly inhibits Gα binding and GTPase acceleration. In addition, we report that modification of C148, a residue located on the opposite face of RGS4, can disrupt RGS/Gα interaction through an allosteric mechanism which almost completely inhibits the Gα-RGS protein-protein interaction. These findings demonstrate three important points: 1) the modification of C148 allosteric site results in significant changes to the RGS interaction surface with Gα, 2) this identifies a "hot-spot" on RGS4 for binding of small molecules and triggering an allosteric change that may be significantly more effective than targeting the actual protein-protein interaction surface and 3) due to the modification of a positional equivalent of C148 in RGS8 by CCG-4986, but lack of inhibition that indicates RGS proteins exhibit fundamental differences in their responses to small molecule ligands.The American Society for Pharmacology and Experimental Therapeutics