Abstract.
The mammalian G proteins G15 and G16 couple a wide variety of receptors to phospholipase C (PLC) in co-transfected systems, and it has been suggested that they can be used as tools in agonist-screening systems. Using the reversed tetracycline-controlled transactivation system we generated rat pituitary GH3 cell clones that expressed Gα15 and Gα16 conditionally to study the coupling of endogenous receptors to both G proteins. In cells expressing moderate levels of Gα15, activation of various endogenous receptors increased inositol phosphate production, whereas conditional expression of Gα16 had no significant effect on agonist-dependent PLC activity. Activation of PLC through Gα15 in response to carbachol did not increase cytosolic [Ca2+] ([Ca2+]i) but stimulated protein kinase C. While carbachol decreased the secretory activity in non-induced GH3 cells, it increased secretion in cells expressing Gα15. Our data demonstrate that Gα15 has a higher functional promiscuity than Gα16 when studied in a system that preserves physiological G protein and receptor levels. In addition, Gα15-mediated coupling of a receptor to PLC can change the cellular response to receptor agonists, indicating that downstream cellular functions can be used to detect receptor activation in screening systems employing a promiscuous G protein.
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Offermanns, S., Negulescu, P., Hu, YH. et al. Conditionally expressed Gα15 couples to endogenous receptors in GH3 cells. Naunyn-Schmied Arch Pharmacol 364, 140–148 (2001). https://doi.org/10.1007/s002100100444
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DOI: https://doi.org/10.1007/s002100100444