Claim: The adenosine A2A receptor functions by encoding a protein whose activity is mediated by G proteins.
Evidence: The adenosine A2A receptor, also known as ADORA2A, is an adenosine receptor, and also denotes the human gene encoding it. The adenosine receptors (or P1 receptors) are a class of purinergic G protein-coupled receptors with adenosine as the endogenous ligand. This protein is a member of the G protein-coupled receptor (GPCR) family which possess seven transmembrane alpha helices, as well as an extracellular N-terminus and an intracellular C-terminus. There are four known types of adenosine receptors in humans: A1, A2A, A2B and A3; each is encoded by a different gene. The gene encodes a protein which is one of several receptor subtypes for adenosine. The activity of the encoded protein, a G protein-coupled receptor family member, is mediated by G proteins which activate adenylyl cyclase, which induce synthesis of intracellular cAMP.