| Popis: |
Atypical antipsychotic drugs targeting the 5-HT2A receptor (2AR) are widely used in the treatment of schizophrenia and psychosis. Recent studies point to a new class of potential antipsychotic drugs targeting the metabotropic glutamate receptor 2 (mGluR2). We recently reported that a heteromeric complex formed between these two receptors integrates the actions of serotonergic and glutamatergic drugs, modulating the balance between Gi and Gq signaling in a way that can predict the psychoactive properties of these drugs (Fribourg et al. 2011, Cell. 147(5):1011-23). The biological relevance of the mGluR2/2AR crosstalk was challenged by a more recent study in which co-expression of the two receptors in HEK-293 cells had no significant effect on either Gi or Gq signaling in response to several serotonergic and glutamatergic drugs (Delille et al., 2012, Neuropharmacology 62(7):2184-91). To address this controversy, we generated several clones of HEK-293 cells expressing different levels of the two receptors in the background of the G protein inwardly rectifying GIRK1/GIRK4 channel, which can serve as a reporter for both Gi and Gq signaling. Using the ratiometric calcium indicator Fura-2 for quantification of Gq signaling we identified clones showing various degrees of functional crosstalk between the two receptors (crosstalk positive clones) and clones that were crosstalk negative. Functional crosstalk correlated with the expression levels of the two receptors, as measured by real time RT-PCR and flow-cytometry. GIRK channel activity, measured by electrophysiology, confirmed cross-signaling from both Gi and Gq sides in a crosstalk positive clone, but not a crosstalk negative one. In the later, a combination of ligands targeting both receptors was necessary in order to elicit functional crosstalk. We are currently testing positive allosteric modulators of the mGluR2 for their ability to suppress Gq signaling through 2AR. |
