An N-terminal region of Caenorhabditis elegans RGS proteins EGL-10 and EAT-16 directs inhibition of G(alpha)o versus G(alpha)q signaling.
Regulator of G protein signaling (RGS) proteins contain an RGS domain that inhibits G(alpha) signaling by activating G(alpha) GTPase activity. Certain RGS proteins also contain a Ggamma-like (GGL) domain and a poorly characterized but conserved N-terminal region. We assessed the functions of these subregions in the Caenorhabditis elegans RGS proteins EGL-10 and EAT-16, which selectively inhibit GOA-1 (G(alpha)(o)) and EGL-30 (G(alpha)(q)), respectively. Using transgenes in C. elegans, we expressed EGL-10, EAT-16, their subregions, or EGL-10/EAT-16 chimeras. The chimeras showed that the GGL/RGS region of either protein can act on either GOA-1 or EGL-30 and that a key factor determining G(alpha) target selectivity is the manner in which the N-terminal and GGL/RGS regions are linked. We also found that coexpressing N-terminal and GGL/RGS fragments of EGL-10 gave full EGL-10 activity, whereas either fragment alone gave little activity. Biochemical analysis showed that coexpressing the two fragments caused both to increase in abundance and also caused the GGL/RGS fragment to move to the membrane, where the N-terminal fragment is localized. By coimmunoprecipitation, we found that the N-terminal fragment complexes with the C-terminal fragment and its associated Gbeta subunit, GPB-2. We conclude that the N-terminal region directs inhibition of G(alpha) signaling by forming a complex with the GGL/RGS region and affecting its stability, membrane localization, and G(alpha) target specificity.
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D015153:Blotting, Western; D017173:Caenorhabditis elegans / Q000737:chemistry*; D029742:Caenorhabditis elegans Proteins; D002462:Cell Membrane / Q000378:metabolism; D002875:Chromosomes / Q000648:ultrastructure; D000939:Epitopes; D020555:GTP-Binding Protein Regulators; D015801:Helminth Proteins / Q000737:chemistry*; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D015151:Immunoblotting; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism; D020710:RGS Proteins / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013997:Time Factors; D019076:Transgenes
D029742:Caenorhabditis elegans Proteins; C120636:EAT-16 protein, C elegans; C105577:EGL-10 protein, C elegans; D000939:Epitopes; D020555:GTP-Binding Protein Regulators; D015801:Helminth Proteins; D011506:Proteins; D020710:RGS Proteins; D020962:Heterotrimeric GTP-Binding Proteins