The functional cooperation of 5-HT 1A and mGlu4R in HEK-293 cell line

Background The serotonin 5-HT 1A receptor (5-HT 1A R) and metabotropic glutamate receptor 4 (mGlu4) have been implicated as sites of antipsychotic drug action. 5-HT 1A R belongs to the A class of G protein-coupled receptors (GPCRs); mGlu4 is a representative of class C GPCRs. Both receptors preferentially couple with Gi protein to inhibit cAMP formation. The present work aimed to examine the possibility of mGlu4 and 5-HT 1A receptor cross-talk, the phenomenon that could serve as a molecular basis of the interaction of these receptor ligands observed in behavioral studies. Methods First, in vitro studies were performed to examine the pharmacological modulation of interaction of the mGlu4 and 5-HT 1A receptors in the T-REx 293 cell line using SNAP- or HALO–tag and cAMP accumulation assay. Next, the colocalization of these two receptors was examined in some regions of the mouse brain by applying RNAScope dual fluorescence in situ hybridization, immunohistochemical labeling, and proximity ligation assay (PLA). Results The ex vivo and in vitro results obtained in the present work suggest the existence of interactions between mGlu4 and 5-HT 1A receptors. The changes were observed in cAMP accumulation assay and were dependent on expression and activation of mGlu4R in T-REx 293cell line. Moreover, the existence of spots with proximity expression of both receptors were showed by PLA, immunofluorescence labeling and RNAscope methods. Conclusion The existence of interactions between mGlu4 and 5-HT1A receptors may represent another signaling pathway involved in the development and treatment psychiatric disorders such as schizophrenia or depression.