Pannexin1 channels act downstream of P2X₇receptors in ATP-induced murine T-cell death

Abstract

Death of murine T cells induced by extracellular ATP is mainly triggered by activation of purinergic P2X 7 receptors (P2X 7Rs). However, a link between P2X 7Rs and pannexin1 (Panx1) channels, which are non-selective, has been recently demonstrated in other cell types. In this work, we characterized the expression and cellular distribution of pannexin family members (Panxs 1, 2 and 3) in isolated T cells. Panx1 was the main pannexin family member clearly detected in both helper (CD4+) and cytotoxic (CD8+) T cells, whereas low levels of Panx2 were found in both T-cell subsets. Using pharmacological and genetic approaches, Panx1 channels were found to mediate most ATP-induced ethidium uptake since this was drastically reduced by Panx1 channel blockers (10Panx1, Probenecid and low carbenoxolone concentration) and absent in T cells derived from Panx1-/- mice. Moreover, electrophysiological measurements in wild-type CD4+ cells treated with ATP unitary current events and pharmacological sensitivity compatible with Panx1 channels were found. In addition, ATP release from T cells treated with 4Br-A23187, a calcium ionophore, was completely blocked with inhibitors of both connexin hemichannels and Panx1 channels. Panx1 channel blockers drastically reduced the ATP-induced T-cell mortality, indicating that Panx1 channels mediate the ATP-induced T-cell death. However, mortality was not reduced in T cells of Panx1-/- mice, in which levels of P2X 7Rs and ATP-induced intracellular free Ca2+ responses were enhanced suggesting that P2X 7Rs take over Panx1 channels lose-function in mediating the onset of cell death induced by extracellular ATP.

Pathological ATPergic Signaling in Major Depression and Bipolar Disorder

“…Moreover, during long-lasting activation of P2X7Rs, the single-channel current amplitude and the permeation characteristics remained constant (Pippel et al, 2017). Although convincing evidence indicates that pore opening is due to the recruitment of an accessory protein, the pannexin-1 channel (Panx-1; Pelegrin and Surprenant, 2006;Gulbransen et al, 2012;Shoji et al, 2014;Chen et al, 2017), the observation that, for example, the P2X7R pore formation is retained in Panx-1 −/− cells supports the opposite notion (Hanley et al, 2012).…”

High glucocorticoid levels during gestation activate the inflammasome in hippocampal oligodendrocytes of the offspring

“…Since ATP can be released by reactive microglia and astrocytes (Orellana et al, ), it is conceivable that the DEX treatment described herein induces ATP release from microglia and astrocytes. This possibility is supported by the effect of La 3+ and A740003 [a general P2X receptor blocker (Shoji et al, ) and selective blocker of P2X 7 R (Honore et al, )], respectively, since they completely inhibited the increase in oligodendrocyte hemichannel activity in brain slices of the offspring from DEX‐treated mice. This would indicate that the continuous release of ATP keeps extracellular ATP concentration high enough to activate P2X 7 Rs.…”

Corrigendum to “Evaluation and comparison of three different separation techniques for analysis of retroamide enantiomers and their biological evaluation against h-P2X7 receptor” [J. Chromatogr. B 986–987 (2015) 35–43]

“…However, whether P2X7 itself directly mediates pore formation by channel dilation or whether other P2X7-associated proteins such as pannexin 1 form the pores is still a matter of debate. Interestingly, inhibition of pannexin-1 significantly reduced ATP-induced mouse T cell death (26). This suggests that drastic elevation of intracellular Ca 2+ , either through P2X7 itself or via other associated nonselective pore-forming proteins, may represent an essential common event triggered in the early phase leading to cell death.…”