title: Differential regulation of P2X7 receptor activation by extracellular nicotinamide adenine dinucleotide and ecto-ADP-ribosyltransferases in murine macrophages and T cells.
abstract: Extracellular NAD induces the ATP-independent activation of the ionotropic P2X(7) purinergic receptor (P2X(7)R) in murine T lymphocytes via a novel covalent pathway involving ADP-ribosylation of arginine residues on the P2X(7)R ectodomain. This modification is catalyzed by ART2.2, a GPI-anchored ADP-ribosyltransferase (ART) that is constitutively expressed in murine T cells. We previously reported that ART2.1, a related ecto-ART, is up-regulated in inflammatory murine macrophages that constitutively express P2X(7)R. Thus, we tested the hypothesis that extracellular NAD acts via ART2.1 to regulate P2X(7)R function in murine macrophages. Coexpression of the cloned murine P2X(7)R with ART2.1 or ART2.2 in HEK293 cells verified that P2X(7)R is an equivalent substrate for ADP-ribosylation by either ART2.1 or ART2.2. However, in contrast with T cells, the stimulation of macrophages or HEK293 cells with NAD alone did not activate the P2X(7)R. Rather, NAD potentiated ATP-dependent P2X(7)R activation as indicated by a left shift in the ATP dose-response relationship. Thus, extracellular NAD regulates the P2X(7)R in both macrophages and T cells but via distinct mechanisms. Although ADP-ribosylation is sufficient to gate a P2X(7)R channel opening in T cells, this P2X(7)R modification in macrophages does not gate the channel but decreases the threshold for gating in response to ATP binding. These findings indicate that extracellular NAD and ATP can act synergistically to regulate P2X(7)R signaling in murine macrophages and also suggest that the cellular context in which P2X(7)R signaling occurs differs between myeloid and lymphoid leukocytes.
authors: Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44120, USA.
authors: Shiyuan
authors: S
authors: Hong
authors: Nicole
authors: N
authors: Schwarz
authors: Anette
authors: A
authors: Brass
authors: Michel
authors: M
authors: Seman
authors: Friedrich
authors: F
authors: Haag
authors: Friedrich
authors: F
authors: Koch-Nolte
authors: William P
authors: WP
authors: Schilling
authors: George R
authors: GR
authors: Dubyak
mesh_terms: D036002:ADP Ribose Transferases / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D004306:Dose-Response Relationship, Immunologic; D005110:Extracellular Space / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D006801:Humans; D018836:Inflammation Mediators / Q000502:physiology; D008264:Macrophages / Q000201:enzymology / Q000276:immunology* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008814:Mice, Inbred NZB; D018345:Mice, Knockout; D009243:NAD / Q000502:physiology*; D017434:Protein Structure, Tertiary; D018048:Receptors, Purinergic P2 / Q000096:biosynthesis / Q000172:deficiency / Q000378:metabolism* / Q000502:physiology; D058486:Receptors, Purinergic P2X7; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D013379:Substrate Specificity / Q000235:genetics / Q000276:immunology; D013601:T-Lymphocytes / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism
chemical_list: D018836:Inflammation Mediators; C546468:P2RX7 protein, human; C546469:P2rx7 protein, mouse; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D009243:NAD; D036002:ADP Ribose Transferases; C449322:Art2a protein, mouse; C449339:Art2b protein, mouse