title: The P2X7 receptor and Pannexin-1 are both required for the promotion of multinucleated macrophages by the inflammatory cytokine GM-CSF.
abstract: The P2X(7) receptor (P2X(7)R), an ATP-gated ion channel, has been implicated in the process of cell-to-cell fusion into multinucleated macrophages (MA), but its contribution to MA fusion driven by physiological/pathological stimuli is not clearly established. Based on several lines of evidence, we demonstrate that P2X(7)R is critical for the induction of multinucleated MA by the inflammatory cytokine GM-CSF: 1) pharmacological inhibition of P2X(7)R with oxidized ATP (oATP), KN-62, and the selective antagonist A740003 abrogated GM-CSF action on rat alveolar MA and murine peritoneal MA; 2) a murine J774 P2X(7) low MA clone, selected for defective P2X(7)R function, was unresponsive; 3) MA from mice lacking P2X(7)R failed to respond to GM-CSF, in contrast to wild-type. GM-CSF also stimulated ATP-induced membrane permeabilization in J774 P2X(7) high MA and rat alveolar MA, an effect absent in the P2X(7) low MA clone and inhibited by the P2X(7) blockers oATP and KN-62. Notably, the stimulatory effects of GM-CSF on pore formation and MA fusion were both inhibited by blocking functional Pannexin-1 (Panx-1), and GM-CSF failed to stimulate MA fusion in cells from Panx-1 knockout mice. We provide further evidence that extracellular ATP release from peritoneal MA is dependent on P2X(7) but not on Panx-1 expression and that its metabolism to adenosine mediates P2X(7)-dependent MA fusion. These data demonstrate that both P2X(7) and Panx-1 are required for GM-CSF promotion of MA fusion but likely act independently through different signaling pathway(s).
authors.affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada. ilemaire@uottawa.ca
authors.forename: Irma
authors.initials: I
authors.lastname: Lemaire
authors.forename: Simonetta
authors.initials: S
authors.lastname: Falzoni
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.forename: Patrizia
authors.initials: P
authors.lastname: Pellegatti
authors.forename: Francesco
authors.initials: F
authors.lastname: Di Virgilio
mesh_terms: D000818:Animals; D015153:Blotting, Western; D017630:Connexins / Q000276:immunology* / Q000378:metabolism; D015726:Giant Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000276:immunology* / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000276:immunology* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D051381:Rats; D017208:Rats, Wistar; D058486:Receptors, Purinergic P2X7 / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology
chemical_list: D017630:Connexins; D009419:Nerve Tissue Proteins; D058486:Receptors, Purinergic P2X7; D016178:Granulocyte-Macrophage Colony-Stimulating Factor