RT Journal Article SR Electronic T1 Connexin 43 Hemichannels Are Permeable to ATP JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 4702 OP 4711 DO 10.1523/JNEUROSCI.5048-07.2008 VO 28 IS 18 A1 Kang, Jian A1 Kang, Ning A1 Lovatt, Ditte A1 Torres, Arnulfo A1 Zhao, Zhuo A1 Lin, Jane A1 Nedergaard, Maiken YR 2008 UL http://www.jneurosci.org/content/28/18/4702.abstract AB Astrocytes are electrically nonexcitable cells that communicate by means of Ca2+ signaling. Long-distance intercellular Ca2+ waves are initiated by release of ATP and activation of purinergic receptors on nearby cells. Previous studies have implicated connexin 43 (Cx43) in ATP release, but definitive proof that ATP exits through Cx43 hemichannels does not exist. Here, through several alternative approaches, we show that ATP anions can permeate through Cx43 hemichannels. First, openings of Cx43 hemichannels were detected in both cell-attached and inside-out patch recordings in C6 cells expressing Cx43, but not in C6 cells expressing Cx43-eGFP (enhanced green fluorescent protein) or a C-terminus truncation mutant of Cx43. Second, Cx43 hemichannel openings were inhibited by three structurally different gap-junction channel blockers, but not by the P2X7 blocker Brilliant blue G. Third, bioluminescence imaging of ATP combined with single-channel recording in the inside-out patch configuration showed that ATP efflux coincided with channel openings and was absent when the Cx43 hemichannel was closed. Fourth, ion replacement experiments confirmed that Cx43 hemichannels are permeable to ATP. In summary, these observations provide the first direct evidence for efflux of ATP through Cx43 hemichannels. Furthermore, a putative Cx43 hemichannel with characteristics identical to the Cx43 hemichannel in C6 cells was identified in the membrane of hippocampal astrocytes in acutely prepared slices.