Adenosine A1 and A2A receptors (A1R/A2AR)

The Adenosine A1 and A2A receptors are members of the G protein-coupled receptor (GPCR) family that mediate the physiological effects of adenosine, a ubiquitous purine nucleoside. The A1 receptor is primarily coupled to Gi/o proteins, leading to the inhibition of adenylate cyclase and a reduction in cAMP levels, which results in inhibitory effects on neurotransmission and heart rate. In contrast, the A2A receptor is coupled to Gs proteins, stimulating adenylate cyclase and increasing cAMP, which promotes vasodilation and modulates immune and inflammatory responses. These receptors are significant therapeutic targets; for instance, A2A antagonists like istradefylline are used as adjunctive treatments in Parkinson's disease to improve motor function by modulating dopaminergic signaling in the striatum. Additionally, non-selective antagonists like caffeine are widely consumed for their stimulant effects, while selective A2A agonists are utilized in cardiac stress testing to induce coronary vasodilation. In oncology, A2A receptor blockade is being investigated as a strategy to enhance anti-tumor immunity by preventing adenosine-mediated immunosuppression in the tumor microenvironment.

Other names

ADORA1ADORA2AAdenosine A1 receptorAdenosine A2A receptorA1 adenosine receptorA2A adenosine receptor

Drugs targeting these receptors typically act as either non-selective or selective antagonists (e.g., caffeine, istradefylline) to block the inhibitory effects of endogenous adenosine, or as agonists (e.g., regadenoson) to induce physiological responses like vasodilation for diagnostic imaging.