Ecdysone-based system for controlled inducible expression of metabotropic glutamate receptor subtypes 2, 5, and 8

Stable and inducible expression of human metabotropic glutamate receptor types 2, 5, and 8 was achieved in HEK293 cells using the ecdysone inducible system. Treatment of the respective cell lines with ponasterone A resulted in time- and concentration-dependent induction of receptor expression. In all cases, the functional activation of receptors was determined by measuring increases in intracellular calcium. The physiologically Gα₁- coupled receptors mGluR2 and mGluR8 were successfully coupled to phospholipase C activation using the chimeric G protein Gα_q/o. The pharmacological properties of recombinant receptors were characterized and proved to be similar to native receptors. Our data suggest that the ecdysone system has a number of characteristics that make it well suited for expressing mGluRs and that the combined use of this system and chimeric G proteins allows receptors to be characterized using a rapid and straightforward Ca²⁺ assay.