title: Diadenosine homodinucleotide products of ADP-ribosyl cyclases behave as modulators of the purinergic receptor P2X7.
abstract: ADP-ribosyl cyclases from both vertebrates and invertebrates were previously shown to produce two isomers of P1,P2 diadenosine 5',5'"-P1, P2-diphosphate, P18 and P24, from cyclic ADP-ribose (cADPR) and adenine. P18 and P24 are characterized by an unusual N-glycosidic linkage in one of the adenylic mononucleotides (Basile, G., Taglialatela-Scafati, O., Damonte, G., Armirotti, A., Bruzzone, S., Guida, L., Franco, L., Usai, C., Fattorusso, E., De Flora, A., and Zocchi, E. (2005) Proc. Natl. Acad. Sci. U.S.A. 102, 14509-14514). P24, but not P18, proved to increase the intracellular Ca(2+) concentration ([Ca(2+)](i)) in HeLa cells and to negatively affect mitochondrial function. Here we show that micromolar P24, but not P18, triggers a slow and sustained influx of extracellular Ca(2+) through the opening of the purinergic receptor/channel P2X7. On the other hand, P18 inhibits the Ca(2+) influx induced by 0.6 mm ATP in HEK293 cells stably transfected with P2X7, with an IC(50) of approximately 1 mum. Thus, P18 is devoid of intrinsic P2X7 stimulatory activity and behaves as an ATP antagonist. A P2X7-mediated increase of the basal [Ca(2+)](i) has been demonstrated to negatively affect Schwann cell (SC) function in rats with the inherited, peripheral neuropathy Charcot-Marie-Tooth 1A (CMT1A) (Nobbio, L., Sturla, L., Fiorese, F., Usai, C., Basile, G., Moreschi, I., Benvenuto, F., Zocchi, E., De Flora, A., Schenone, A., and Bruzzone S. (2009) J. Biol. Chem. 284, 23146-23158). Preincubation of CMT1A SC with 200 nm P18 restored the basal [Ca(2+)](i) to values similar to those recorded in wild-type SC. These results identify P18 as a new P2X7 antagonist, potentially useful in the treatment of CMT1A.
authors.affiliation: Department of Experimental Medicine, Section of Biochemistry, and Center of Excellence for Biomedical Research (CEBR), University of Genova, Viale Benedetto XV/1, 16132 Genova, Italy. santina.bruzzone@unige.it
authors.forename: Santina
authors.initials: S
authors.lastname: Bruzzone
authors.forename: Giovanna
authors.initials: G
authors.lastname: Basile
authors.forename: Madhu Parakkottil
authors.initials: MP
authors.lastname: Chothi
authors.forename: Lucilla
authors.initials: L
authors.lastname: Nobbio
authors.forename: Cesare
authors.initials: C
authors.lastname: Usai
authors.forename: Emanuela
authors.initials: E
authors.lastname: Jacchetti
authors.forename: Angelo
authors.initials: A
authors.lastname: Schenone
authors.forename: Andreas H
authors.initials: AH
authors.lastname: Guse
authors.forename: Francesco
authors.initials: F
authors.lastname: Di Virgilio
authors.forename: Antonio
authors.initials: A
authors.lastname: De Flora
authors.forename: Elena
authors.initials: E
authors.lastname: Zocchi
mesh_terms: D036541:ADP-ribosyl Cyclase / Q000378:metabolism*; D051997:ADP-ribosyl Cyclase 1 / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002455:Cell Division; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004622:Embryo, Mammalian; D004996:Ethidium / Q000378:metabolism; D005682:Gadolinium / Q000494:pharmacology; D006367:HeLa Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007448:Invertebrates; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D011161:Porifera / Q000201:enzymology; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058486:Receptors, Purinergic P2X7; D014162:Transfection; D014714:Vertebrates
chemical_list: C546468:P2RX7 protein, human; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D005682:Gadolinium; D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D004996:Ethidium; D002118:Calcium