Selective Uncoupling of RGS Action by a Single Point Mutation in the G Protein α-Subunit

• Published in: The Journal of biological chemistry Vol. 273; no. 10; pp. 5780 - 5784
• Main Authors: DiBello, Paul R., Garrison, Tiffany Runyan, Apanovitch, Donald M., Hoffman, Ginger, Shuey, David J., Mason, Kimberly, Cockett, Mark I., Dohlman, Henrik G.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 06.03.1998
• Subjects: Animals; Calcium - metabolism; CHO Cells; Cricetinae; Fungal Proteins - genetics; GTP Phosphohydrolases - analysis; GTP-Binding Proteins - genetics; GTPase-Activating Proteins; Guanosine Triphosphate - metabolism; Inositol Phosphates - metabolism; Models, Molecular; Mutagenesis - genetics; Pheromones - analysis; Point Mutation - genetics; Protein Binding - physiology; Proteins - genetics; Proteins - physiology; Recombinant Fusion Proteins - metabolism; Saccharomyces cerevisiae Proteins; Serotonin - pharmacology; Signal Transduction - physiology; Transfection - genetics
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.273.10.5780

Heterotrimeric G proteins function as molecular relays, shuttling between cell surface receptors and intracellular effectors that propagate a signal. G protein signaling is governed by the rates of GTP binding (catalyzed by the receptor) and GTP hydrolysis. RGS proteins (regulators of G protein signaling) were identified as potent negative regulators of G protein signaling pathways in simple eukaryotes and are now known to act as GTPase-activating proteins (GAPs) for G protein α-subunits in vitro. It is not known, however, if Gα GAP activity is responsible for the regulatory action of RGS proteins in vivo. We describe here a Gα mutant in yeast (gpa1sst) that phenotypically mimics the loss of its cognate RGS protein (SST2). The gpa1sst mutant is resistant to an activated allele of SST2 in vivo and is unresponsive to RGS GAP activityin vitro. The analogous mutation in a mammalian Gqα is also resistant to RGS action in transfected cells. These mutants demonstrate that RGS proteins act through Gα and that RGS-GAP activity is responsible for their desensitizing activity in cells. The Gαsst mutant will be useful for uncoupling RGS-mediated regulation from other modes of signal regulation in whole cells and animals.