Replacement of the α5 helix of Gα 16 with Gα s-specific sequences enhances promiscuity of Gα 16 toward G s-coupled receptors

Abstract

G 16 can couple indiscriminately to a large number of G protein-coupled receptors (GPCRs), making it a prime candidate as a universal adaptor for GPCRs. In order to increase the promiscuity of Gα 16, three chimeras incorporating increasing lengths of G s-specific residues (25, 44 or 81 residues) into the C-terminus of Gα 16 were constructed and named 16s25, 16s44 and 16s81, respectively. The chimeras were examined for their ability to mediate receptor-induced stimulation of phospholipase C (PLC) and Ca 2+ mobilization. 16s25 was more effective than 16s44 and 16s81 at coupling to G s-linked receptors. 16s25 coupled productively to 10 different G s-coupled receptors examined and, for 50% of these receptors, 16s25-mediated PLC activities were higher than those mediated via Gα 16. Similar results were observed for agonist-induced Ca 2+ mobilizations. These results show that incorporating the α5 helix of Gα s into Gα 16 can increase the promiscuity of 16s25 towards G s-coupled receptors.