1. GIV/Girdin activates Gαi and inhibits Gαs via the same motif
- Author
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Gupta, Vijay, Bhandari, Deepali, Leyme, Anthony, Aznar, Nicolas, Midde, Krishna K, Lo, I-Chung, Ear, Jason, Niesman, Ingrid, López-Sánchez, Inmaculada, Blanco-Canosa, Juan Bautista, von Zastrow, Mark, Garcia-Marcos, Mikel, Farquhar, Marilyn G, and Ghosh, Pradipta
- Subjects
Biochemistry and Cell Biology ,Biological Sciences ,2.1 Biological and endogenous factors ,Generic health relevance ,Amino Acid Motifs ,Amino Acid Sequence ,Cell Proliferation ,Chemotaxis ,Cyclic AMP ,Cyclic AMP Response Element-Binding Protein ,Cyclic AMP-Dependent Protein Kinases ,Cyclin-Dependent Kinase 5 ,Down-Regulation ,Endosomes ,Epidermal Growth Factor ,Extracellular Signal-Regulated MAP Kinases ,Fluorescence Resonance Energy Transfer ,GTP-Binding Protein alpha Subunits ,Gi-Go ,GTP-Binding Protein alpha Subunits ,Gs ,GTP-Binding Protein beta Subunits ,GTP-Binding Protein gamma Subunits ,Guanosine Triphosphate ,HeLa Cells ,Humans ,Microfilament Proteins ,Mutant Proteins ,Phosphorylation ,Protein Binding ,Protein Kinase C-theta ,Signal Transduction ,Structure-Activity Relationship ,Vesicular Transport Proteins ,heterotrimeric G proteins ,cAMP ,cancer invasion ,growth factor receptor tyrosine kinase ,guanine nucleotide dissociation inhibitor ,Hela Cells - Abstract
We previously showed that guanine nucleotide-binding (G) protein α subunit (Gα)-interacting vesicle-associated protein (GIV), a guanine-nucleotide exchange factor (GEF), transactivates Gα activity-inhibiting polypeptide 1 (Gαi) proteins in response to growth factors, such as EGF, using a short C-terminal motif. Subsequent work demonstrated that GIV also binds Gαs and that inactive Gαs promotes maturation of endosomes and shuts down mitogenic MAPK-ERK1/2 signals from endosomes. However, the mechanism and consequences of dual coupling of GIV to two G proteins, Gαi and Gαs, remained unknown. Here we report that GIV is a bifunctional modulator of G proteins; it serves as a guanine nucleotide dissociation inhibitor (GDI) for Gαs using the same motif that allows it to serve as a GEF for Gαi. Upon EGF stimulation, GIV modulates Gαi and Gαs sequentially: first, a key phosphomodification favors the assembly of GIV-Gαi complexes and activates GIV's GEF function; then a second phosphomodification terminates GIV's GEF function, triggers the assembly of GIV-Gαs complexes, and activates GIV's GDI function. By comparing WT and GIV mutants, we demonstrate that GIV inhibits Gαs activity in cells responding to EGF. Consequently, the cAMP→PKA→cAMP response element-binding protein signaling axis is inhibited, the transit time of EGF receptor through early endosomes are accelerated, mitogenic MAPK-ERK1/2 signals are rapidly terminated, and proliferation is suppressed. These insights define a paradigm in G-protein signaling in which a pleiotropically acting modulator uses the same motif both to activate and to inhibit G proteins. Our findings also illuminate how such modulation of two opposing Gα proteins integrates downstream signals and cellular responses.
- Published
- 2016