Mechanisms that control mobilization of cytosolic calcium [Ca2+]i are key for regulation of numerous eukaryotic cell functions. One such paradigmatic mechanism involves activation of phospholipase Cβ (PLCβ) enzymes by G protein βγ subunits from activated Gαi-Gβγ heterotrimers. Here we report identification of a master switch to enable this control for PLCβ enzymes in living cells. We find that the Gαi-Gβγ-PLCβ-Ca2+ signaling module is entirely dependent on the presence of active Gαq. If Gαq is pharmacologically inhibited or genetically ablated, Gβγ can bind to PLCβ, but does not elicit Ca2+ signals. Removal of an auto-inhibitory linker that occludes the active site of the enzyme is required and sufficient to empower ‘stand-alone control’ of PLCβ by Gβγ. Dependence on Gαq of Gi-Gβγ-Ca2+ is a mechanism placing an entire signaling branch of G protein-coupled receptors (GPCRs) under hierarchical control of Gq, and changes our understanding of how Gi-GPCRs trigger [Ca2+]i via PLCβ enzymes.
Keywords: G protein-coupled receptor, GPCR, heterotrimeric G protein, Gq, Gi, phospholipase Cβ, Ca2+ signaling, FR900359, PTX, GPR17
Pfeil, Eva Marie and Vescovo, Maddalena and Vögtle, Timo and Brands, Julian and Rick, Ulrike and Merten, Nicole and Albrecht, Ina-Maria and Kawakami, Koki and Ono, Yuki and Ngako Kadji, Francois Marie and Aoki, Junken and Häberlein, Felix and Matthey, Michaela and Garg, Jaspal and Hennen, Stephanie and Jobin, Marie-Lise and Seier, Kerstin and Calebiro, Davide and Pfeifer, Alexander and Heinemann, Akos and Wenzel, Daniela and König, Gabriele and Nieswandt, Bernhard and Fleischmann, Bernd K. and Inoue, Asuka and Simon, Katharina and Kostenis, Evi, Heterotrimeric G Protein Subunit Gαq is a Master Switch for Gβγ-Mediated Calcium Mobilization by Gi-Coupled GPCRs. Available at SSRN: https://ssrn.com/abstract=3578140 or http://dx.doi.org/10.2139/ssrn.3578140
This version of the paper has not been formally peer reviewed.
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