The A2A-adenosine receptor is a Gs-coupled receptor, which has several unique structural and functional characteristics. Recently, the C-terminus of the receptor has been appreciated as a binding site for several “accessory” proteins, of which only half a dozen are established. It is clear that (i) this list cannot be exhaustive and (ii) that all these proteins cannot bind simultaneously to the receptor. The challenging, but very important task is to document which of all these interactions do occur in the living organisms. Here we propose to meet this challenge by characterizing the interactome of the A2A-receptor by using a two-step proteomics approach; i.e., the receptor will first be expressed in tagged versions in cells, which can be differentiated into neurons. This will allow for optimization of the conditions and for an initial survey of interaction partners; subsequently, we intend to generate mice, in which the receptor has been engineered to afford the isolation of receptor-complexes from native tissues, in particular the striatum. To the best of our knowledge, the proposed strategy has not yet been pursued with other GPCRs. Thus, if successful, it may set a precedent and provide the proof-of-principle for the entire family of GPCRs. At the very least, the current approach provides the ‘acid test’ for all purported interactors of the A2A-receptor.