Two RGS proteins that inhibit Galpha(o) and Galpha(q) signaling in C. elegans neurons require a Gbeta(5)-like subunit for function.
BACKGROUND
Gbeta proteins have traditionally been thought to complex with Ggamma proteins to function as subunits of G protein heterotrimers. The divergent Gbeta(5) protein, however, can bind either Ggamma proteins or regulator of G protein signaling (RGS) proteins that contain a G gamma-like (GGL) domain. RGS proteins inhibit G protein signaling by acting as Galpha GTPase activators. While Gbeta(5) appears to bind RGS proteins in vivo, its association with Ggamma proteins in vivo has not been clearly demonstrated. It is unclear how Gbeta(5) might influence RGS activity. In C. elegans there are exactly two GGL-containing RGS proteins, EGL-10 and EAT-16, and they inhibit Galpha(o) and Galpha(q) signaling, respectively.


RESULTS
We knocked out the gene encoding the C. elegans Gbeta(5) ortholog, GPB-2, to determine its physiological roles in G protein signaling. The gpb-2 mutation reduces the functions of EGL-10 and EAT-16 to levels comparable to those found in egl-10 and eat-16 null mutants. gpb-2 knockout animals are viable, and exhibit no obvious defects beyond those that can be attributed to a reduction of EGL-10 or EAT-16 function. GPB-2 protein is nearly absent in eat-16; egl-10 double mutants, and EGL-10 protein is severely diminished in gpb-2 mutants.


CONCLUSIONS
Gbeta(5) functions in vivo complexed with GGL-containing RGS proteins. In the absence of Gbeta(5), these RGS proteins have little or no function. The formation of RGS-Gbeta(5) complexes is required for the expression or stability of both the RGS and Gbeta(5) proteins. Appropriate RGS-Gbeta(5) complexes regulate both Galpha(o) and Galpha(q) proteins in vivo.
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA.
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D000818:Animals; D030801:Animals, Genetically Modified; D001522:Behavior, Animal; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins; D020555:GTP-Binding Protein Regulators; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D044387:GTP-Binding Protein beta Subunits; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015870:Gene Expression; D015801:Helminth Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D020962:Heterotrimeric GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D009474:Neurons / Q000378:metabolism; D010058:Oviposition; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D019076:Transgenes
D029742:Caenorhabditis elegans Proteins; C120636:EAT-16 protein, C elegans; C105577:EGL-10 protein, C elegans; C427883:GPB-2 protein, C elegans; D020555:GTP-Binding Protein Regulators; D044387:GTP-Binding Protein beta Subunits; C094668:Gnb5 protein, mouse; D015801:Helminth Proteins; D020710:RGS Proteins; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins