A molecular mechanism to diversify Ca2+ signaling downstream of Gs protein-coupled receptors.

A long-held tenet in inositol-lipid signaling is that cleavage of membrane phosphoinositides by phospholipase Cβ (PLCβ) isozymes to increase cytosolic Ca²⁺ in living cells is exclusive to Gq- and Gi-sensitive G protein-coupled receptors (GPCRs). Here we extend this central tenet and show that Gs-GPCRs also partake in inositol-lipid signaling and thereby increase cytosolic Ca²⁺. By combining CRISPR/Cas9 genome editing to delete Gα_s, the adenylyl cyclase isoforms 3 and 6, or the PLCβ1-4 isozymes, with pharmacological and genetic inhibition of Gq and G11, we pin down Gs-derived Gβγ as driver of a PLCβ2/3-mediated cytosolic Ca²⁺ release module. This module does not require but crosstalks with Gα_s-dependent cAMP, demands Gα_q to release PLCβ3 autoinhibition, but becomes Gq-independent with mutational disruption of the PLCβ3 autoinhibited state. Our findings uncover the key steps of a previously unappreciated mechanism utilized by mammalian cells to finetune their calcium signaling regulation through Gs-GPCRs. Gs heterotrimers are considered to be poor providers of free Gβγ subunits. Here, the authors show that—despite this—Gs-derived Gβγ dimers are active transducers of GPCR-initiated Ca2+ signals involving phosphoinositide-based signaling routes. [ABSTRACT FROM AUTHOR]