The A2A adenosine receptor is densely expressed in dopamine-rich areas of the brain and in the vasculature. It is the target of an adjunct medication for Parkinson’s Disease, istradefylline in Japan, an A2A receptor antagonist.
The A2A adenosine receptor is an example of a Gs-coupled receptor, activation of which in the cardiovascular system leads to inhibition of platelet aggregation and vasorelaxation. This new report (1) highlights the link between the receptor and the G protein to focus on areas of unexpected flexibility in the ligand binding region. Further, classical understanding of receptor:G protein interaction identifies a prominent role for the third intracellular loop and the proximal end of the C-terminus (in some GPCR, such as the beta2-AR, a fourth intracellular loop is formed by palmitoylation of an intracellular cysteine residue, which the A2A lacks). The model generated from this cryo-EM study with a nanobody suggests a potentially novel role for an interaction between the first intracellular loop and the Gbeta subunit.
Comments by Steve Alexander (@mqzspa)
(1) Garcia-Nafría J et al. (2018). Cryo-EM structure of the adenosine A2A receptor coupled to an engineered heterotrimeric G protein. eLife, 7. pii: e35946. doi: 10.7554/eLife.35946. [PMID: 29726815]