adenosine receptor subfamily, member of the class A family of seven-transmembrane G protein-coupled receptors
The adenosine receptors (or P1 receptors), a family of G protein-coupled purinergic receptors, bind adenosine as their endogenous ligand. There are four types of adenosine receptors in human, designated as A1, A2A, A2B, and A3. Each type is encoded by a different gene and has distinct functions with some overlap. For example, both A1 and A2A receptors are involved in regulating myocardial oxygen consumption and coronary blood flow in the heart, while the A2A receptor also has a broad spectrum of anti-inflammatory effects in the body. These two receptors also expressed in the brain, where they have important roles in the release of other neurotransmitters such as dopamine and glutamate, while the A2B and A3 receptors found primarily in the periphery and play important roles in inflammation and immune responses. The A1 and A3 receptors preferentially interact with G proteins of the G(i/o) family, thereby lowering the intracellular cAMP levels, whereas the A2A and A2B receptors interact with G proteins of the G(s) family, activating adenylate cyclase to elevate cAMP levels.
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