Functional Interaction between Adenosine A 2A and mGlu 5 Receptors Mediates STEP Phosphatase Activation and Promotes STEP/mGlu 5 R Binding in Mouse Hippocampus and Neuroblastoma Cell Line.

(1) Background: Recently, we found that adenosine A 2A receptor (A 2A R) stimulation results in an increase in STEP phosphatase activity. In order to delve into the mechanism through which A 2A R stimulation induced STEP activation, we investigated the involvement of mGlu 5 R since it is well documented that A 2A R and mGlu 5 R physically and functionally interact in several brain areas. (2) Methods: In a neuroblastoma cell line (SH-SY5Y) and in mouse hippocampal slices, we evaluated the enzymatic activity of STEP by using a para-nitrophenyl phosphate colorimetric assay. A co-immunoprecipitation assay and a Western blot analysis were used to evaluate STEP/mGlu 5 R binding. (3) Results: We found that the A 2A R-dependent activation of STEP was mediated by the mGlu 5 R. Indeed, the A 2A R agonist CGS 21680 significantly increased STEP activity, and this effect was prevented not only by the A 2A R antagonist ZM 241385, as expected, but also by the mGlu 5 R antagonist MPEP. In addition, we found that mGlu 5 R agonist DHPG-induced STEP activation was reversed not only by the mGlu 5 R antagonist MPEP but also by ZM 241385. Finally, via co-immunoprecipitation experiments, we found that mGlu 5 R and STEP physically interact when both receptors are activated (4) Conclusions: These results demonstrated a close functional interaction between mGlu 5 and A 2A receptors in the modulation of STEP activity.