Pannexin 1: the molecular substrate of astrocyte "hemichannels".
Purinergic signaling plays distinct and important roles in the CNS, including the transmission of calcium signals between astrocytes. Gap junction hemichannels are among the mechanisms proposed by which astrocytes might release ATP; however, whether the gap junction protein connexin43 (Cx43) forms these "hemichannels" remains controversial. Recently, a new group of proteins, the pannexins, have been shown to form nonselective, high-conductance plasmalemmal channels permeable to ATP, thereby offering an alternative for the hemichannel protein. Here, we provide strong evidence that, in cultured astrocytes, pannexin1 (Panx1) but not Cx43 forms hemichannels. Electrophysiological and fluorescence microscope recordings performed in wild-type and Cx43-null astrocytes did not reveal any differences in hemichannel activity, which was mostly eliminated by treating Cx43-null astrocytes with Panx1-short interfering RNA [Panx1-knockdown (Panx1-KD)]. Moreover, quantification of the amount of ATP released from wild-type, Cx43-null, and Panx1-KD astrocytes indicates that downregulation of Panx1, but not of Cx43, prevented ATP release from these cells.
Iglesias
Rodolfo
R
The Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Dahl
Gerhard
G
Qiu
Feng
F
Spray
David C
DC
Scemes
Eliana
E
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology*; D001557:Benzenesulfonates / Q000494:pharmacology; D002229:Carbenoxolone / Q000494:pharmacology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D018031:Connexin 43 / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000378:metabolism*; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004558:Electric Stimulation / Q000379:methods; D004622:Embryo, Mammalian; D005456:Fluorescent Dyes / Q000378:metabolism; D015767:Mefloquine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D018408:Patch-Clamp Techniques / Q000379:methods; D034741:RNA, Small Interfering / Q000494:pharmacology
D001557:Benzenesulfonates; D018031:Connexin 43; D017630:Connexins; D005456:Fluorescent Dyes; D009419:Nerve Tissue Proteins; C503631:Panx1 protein, mouse; D034741:RNA, Small Interfering; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000255:Adenosine Triphosphate; C006796:brilliant blue; D002229:Carbenoxolone; D015767:Mefloquine