Pannexin 1, an ATP Release Channel, Is Activated by Caspase Cleavage of Its Pore-associated C-terminal Autoinhibitory Region

Pannexin 1 (PANX1) channels mediate release of ATP, a “find-me” signal that recruits macrophages to apoptotic cells; PANX1 activation during apoptosis requires caspase-mediated cleavage of PANX1 at its C terminus, but how the C terminus inhibits basal channel activity is not understood. Here, we pro...

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Veröffentlicht in:The Journal of biological chemistry 2012-03, Vol.287 (14), p.11303-11311
Hauptverfasser: Sandilos, Joanna K., Chiu, Yu-Hsin, Chekeni, Faraaz B., Armstrong, Allison J., Walk, Scott F., Ravichandran, Kodi S., Bayliss, Douglas A.
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Sprache:eng
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Zusammenfassung:Pannexin 1 (PANX1) channels mediate release of ATP, a “find-me” signal that recruits macrophages to apoptotic cells; PANX1 activation during apoptosis requires caspase-mediated cleavage of PANX1 at its C terminus, but how the C terminus inhibits basal channel activity is not understood. Here, we provide evidence suggesting that the C terminus interacts with the human PANX1 (hPANX1) pore and that cleavage-mediated channel activation requires disruption of this inhibitory interaction. Basally silent hPANX1 channels localized on the cell membrane could be activated directly by protease-mediated C-terminal cleavage, without additional apoptotic effectors. By serial deletion, we identified a C-terminal region just distal to the caspase cleavage site that is required for inhibition of hPANX1; point mutations within this small region resulted in partial activation of full-length hPANX1. Consistent with the C-terminal tail functioning as a pore blocker, we found that truncated and constitutively active hPANX1 channels could be inhibited, in trans, by the isolated hPANX1 C terminus either in cells or when applied directly as a purified peptide in inside-out patch recordings. Furthermore, using a cysteine cross-linking approach, we showed that relief of inhibition following cleavage requires dissociation of the C terminus from the channel pore. Collectively, these data suggest a mechanism of hPANX1 channel regulation whereby the intact, pore-associated C terminus inhibits the full-length hPANX1 channel and a remarkably well placed caspase cleavage site allows effective removal of key inhibitory C-terminal determinants to activate hPANX1. Background: Pannexin 1 is activated by caspase cleavage of its C-terminal tail during apoptosis. Results: Cleavage removes a critical adjacent region to activate membrane-associated PANX1; activation requires dissociation of the C terminus from the pore. Conclusion: An intrinsic inhibitory interaction between the C terminus and the pore constrains PANX1 activity. Significance: PANX1 activation is caused by disruption of C-terminal-mediated inhibition.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M111.323378