The pannexin 1 channel activates the inflammasome in neurons and astrocytes.
The inflammasome is a multiprotein complex involved in innate immunity. Activation of the inflammasome causes the processing and release of the cytokines interleukins 1beta and 18. In primary macrophages, potassium ion flux and the membrane channel pannexin 1 have been suggested to play roles in inflammasome activation. However, the molecular mechanism(s) governing inflammasome signaling remains poorly defined, and it is undetermined whether these mechanisms apply to the central nervous system. Here we show that high extracellular potassium opens pannexin channels leading to caspase-1 activation in primary neurons and astrocytes. The effect of K(+) on pannexin 1 channels was independent of membrane potential, suggesting that stimulation of inflammasome signaling was mediated by an allosteric effect. The activation of the inflammasome by K(+) was inhibited by the pannexin 1 channel blocker probenecid, supporting a role of pannexin 1 in inflammasome activation. Co-immunoprecipitation of neuronal lysates indicates that pannexin 1 associates with components of the multiprotein inflammasome complex, including the P2X7 receptor and caspase-1. Moreover antibody neutralization of the adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD) blocked ATP-induced cell death in oocytes co-expressing P2X7 receptor and pannexin 1. Thus, in contrast to macrophages and monocytes in which low intracellular K(+) has been suggested to trigger inflammasome activation, in neural cells, high extracellular K(+) activates caspase-1 probably through pannexin 1.
Silverman
William R
WR
Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, Florida 33136, USA.
de Rivero Vaccari
Juan Pablo
JP
Locovei
Silviu
S
Qiu
Feng
F
Carlsson
Steven K
SK
Scemes
Eliana
E
Keane
Robert W
RW
Dahl
Gerhard
G
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000502:physiology*; D020170:Caspase 1 / Q000378:metabolism; D016923:Cell Death / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D017630:Connexins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020868:Gene Silencing; D007249:Inflammation / Q000503:physiopathology*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015213:Neuroimmunomodulation / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D011339:Probenecid / Q000494:pharmacology; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058486:Receptors, Purinergic P2X7; D014982:Xenopus laevis
D017630:Connexins; D009419:Nerve Tissue Proteins; C526260:Nlrp1a protein, rat; C546470:P2rx7 protein, rat; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; C479936:pannexin 1, rat; D020170:Caspase 1; D011339:Probenecid; D011188:Potassium