title: Pannexin1 channels act downstream of P2X 7 receptors 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.
authors.affiliation: Departamento de Fisiología; Pontificia Universidad Católica de Chile; Santiago, Chile.
authors.forename: Kenji F
authors.initials: KF
authors.lastname: Shoji
authors.affiliation: Departamento de Fisiología; Pontificia Universidad Católica de Chile; Santiago, Chile.
authors.forename: Pablo J
authors.initials: PJ
authors.lastname: Sáez
authors.affiliation: Departamento de Fisiología; Pontificia Universidad Católica de Chile; Santiago, Chile.
authors.forename: Paloma A
authors.initials: PA
authors.lastname: Harcha
authors.affiliation: Department of Immunology; University of Connecticut Health Center; Farmington, CT USA.
authors.forename: Hector L
authors.initials: HL
authors.lastname: Aguila
authors.affiliation: Departamento de Fisiología; Pontificia Universidad Católica de Chile; Santiago, Chile; Instituto Milenio; Centro Interdisciplinario de Neurociencias de Valparaíso; Valparaíso, Chile.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Sáez
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D000001:Calcimycin / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D017630:Connexins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7 / Q000378:metabolism*; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D059008:Time-Lapse Imaging
chemical_list: D017630:Connexins; D009419:Nerve Tissue Proteins; C503631:Panx1 protein, mouse; C516139:Panx2 protein, mouse; D058486:Receptors, Purinergic P2X7; D000001:Calcimycin; D000255:Adenosine Triphosphate
keywords: P2X7Rs; dye uptake; membrane permeability; necrosis; pannexons