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. Author manuscript; available in PMC: 2017 Jun 16.
Published in final edited form as: Am J Transplant. 2016 Apr 28;16(10):2781–2794. doi: 10.1111/ajt.13801

Figure 1. Overview of purinergic signaling.

Figure 1

Intracellular ATP is released from cells through the opening of pannexin hemi channels or via P2X7 receptors and can serve as an extracellular signaling molecule. ATP subsequently signals with various P2 receptors, both ligand-gated P2X and G protein–coupled P2Y receptors, in an autocrine manner, which has been implicated in a wide variety of physiological processes. Eventually, ATP is hydrolyzed by ENTPDases expressed on cell surfaces, including CD39 and the ecto-5′-nucleotidase CD73, which promote the generation of adenosine. Adenosine signals on G protein–coupled P1 receptors and is metabolized to inosine by the enzyme adenosine deaminase. ADP, adenosine diphosphate; AMP, adenosine monophosphate; ATP, adenosine triphosphate.