Pannexins (Pannexin 1, Pannexin 2 and Pannexin 3) belong to the superfamily of gap junction proteins. Pannexin 1 (PANX1) is ubiquitously expressed, Pannexin 2 (PANX2) is specifically expressed in the human brain and widespread in rodents and Pannexin 3 (PANX3) is also detected in the brain.nThe gating properties of Pannexins were studied in Xenopus oocytes and results demonstrate that only PANX1 is able to form homomeric hemichannels, and is also able to form heteromeric hemichannels with PANX2 but not with PANX3. Not surprising, PANX1 gating properties depend whether it forms homomeric or heteromeric hemichannels.nA number of different stimuli are known to open these channels and include mechanical stress, extracellular ATP, increases in intracellular Ca2+ and inflammation.nPossible roles for Pannexins include paracrine signaling in vascular endothelial cells and taste cell signaling.