fig4

Figure 4. Adenosine receptors. Adenosine interacts with four distinct receptors - A1R, A2AR, A2BR, and A3R. Each of these receptors is linked to a G protein-coupled receptor. The A1R and A3R couple with the Gi protein to inhibit Adenylyl Cyclase. In contrast, the G protein coupled to A2AR and A2BR activates Adenylyl Cyclase, leading to an increased formation of intracellular cyclic AMP. A2BRs also couple to Gq which mobilizes Ca²⁺ upon activation. AMP: Adenosine monophosphate; A2AR: A2A receptors; A2BR: A2B receptors; cAMP: cyclic adenosine monophospha.