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Published August 2001 | public
Journal Article

Conditionally expressed Gα_(15) couples to endogenous receptors in GH_3 cells


The mammalian G proteins G_(15) and G_(16) 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 GH_3 cell clones that expressed Gα_(15) and Gα_(16) conditionally to study the coupling of endogenous receptors to both G proteins. In cells expressing moderate levels of Gα_(15), activation of various endogenous receptors increased inositol phosphate production, whereas conditional expression of Gα_(16) had no significant effect on agonist-dependent PLC activity. Activation of PLC through Gα_(15) in response to carbachol did not increase cytosolic [Ca2+] ([Ca^(2+)]_i) but stimulated protein kinase C. While carbachol decreased the secretory activity in non-induced GH_3 cells, it increased secretion in cells expressing Gα_(15). Our data demonstrate that Gα_(15) has a higher functional promiscuity than Gα_(16) when studied in a system that preserves physiological G protein and receptor levels. In addition, Gα_(15)-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.

Additional Information

© 2001 Springer-Verlag. Received: 23 March 2001; Accepted: 19 April 2001; Published online: 8 June 2001. This work was supported by grants from the National Institutes of General Medical Sciences (GM 34236), from the National Institutes of Mental Health (MH 49176) and from the Deutsche Forschungsgemeinschaft.

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