DAPLE protein inhibits nucleotide exchange on Gαs and Gαq via the same motif that activates Gαi

• Published in: The Journal of biological chemistry Vol. 295; no. 8; pp. 2270 - 2284
• Main Authors: Marivin, Arthur, Maziarz, Marcin, Zhao, Jingyi, DiGiacomo, Vincent, Olmos Calvo, Isabel, Mann, Emily A., Ear, Jason, Blanco-Canosa, Juan B., Ross, Elliott M., Ghosh, Pradipta, Garcia-Marcos, Mikel
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 21-02-2020; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Sequence; Animals; Cattle; cell signaling; G protein; G-protein–coupled receptor (GPCR); GTP-Binding Protein alpha Subunits - metabolism; GTPase; guanine nucleotide dissociation inhibitor (GDI); Guanine Nucleotide Exchange Factors - metabolism; guanine nucleotide–exchange factor (GEF); Gα-binding and -activating (GBA); HEK293 Cells; Humans; Intracellular Signaling Peptides and Proteins - chemistry; Intracellular Signaling Peptides and Proteins - metabolism; Microfilament Proteins - chemistry; Microfilament Proteins - metabolism; Models, Biological; Mutant Proteins - metabolism; Peptides - metabolism; Protein Binding; protein–protein interaction; Signal Transduction; Gα-binding and -activating (GBA); guanine nucleotide–exchange factor (GEF); G-protein–coupled receptor (GPCR); cell signaling; protein–protein interaction; GTPase; G protein; guanine nucleotide dissociation inhibitor (GDI)
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.RA119.011648

Besides being regulated by G-protein–coupled receptors, the activity of heterotrimeric G proteins is modulated by many cytoplasmic proteins. GIV/Girdin and DAPLE (Dvl-associating protein with a high frequency of leucine) are the best-characterized members of a group of cytoplasmic regulators that contain a Gα-binding and -activating (GBA) motif and whose dysregulation underlies human diseases, including cancer and birth defects. GBA motif–containing proteins were originally reported to modulate G proteins by binding Gα subunits of the Gi/o family (Gαi) over other families (such as Gs, Gq/11, or G12/13), and promoting nucleotide exchange in vitro. However, some evidence suggests that this is not always the case, as phosphorylation of the GBA motif of GIV promotes its binding to Gαs and inhibits nucleotide exchange. The G-protein specificity of DAPLE and how it might affect nucleotide exchange on G proteins besides Gαi remain to be investigated. Here, we show that DAPLE's GBA motif, in addition to Gαi, binds efficiently to members of the Gs and Gq/11 families (Gαs and Gαq, respectively), but not of the G12/13 family (Gα12) in the absence of post-translational phosphorylation. We pinpointed Met-1669 as the residue in the GBA motif of DAPLE that diverges from that in GIV and enables better binding to Gαs and Gαq. Unlike the nucleotide-exchange acceleration observed for Gαi, DAPLE inhibited nucleotide exchange on Gαs and Gαq. These findings indicate that GBA motifs have versatility in their G-protein–modulating effect, i.e. they can bind to Gα subunits of different classes and either stimulate or inhibit nucleotide exchange depending on the G-protein subtype.