title: ADP-ribose gates the fertilization channel in ascidian oocytes.
abstract: We report an ion channel in the plasma membrane of unfertilized oocytes of the ascidian Ciona intestinalis that is directly gated by the second messenger ADP-ribose. The ion channel is permeable to Ca2+ and Na+ and is characterized by a reversal potential between 0 and +20 mV and a unitary conductance of 140 pS. Preinjection of the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) or antagonists of intracellular Ca2+ release channels into oocytes did not inhibit the ADP-ribose current, demonstrating that the channel is activated in a Ca2+-independent manner. Both the fertilization current and the current induced by the injection of nicotinamide nucleotides are blocked by nicotinamide, suggesting that the ADP-ribose channel is activated at fertilization in a nicotinamide-sensitive manner. These data suggest that ascidian sperm trigger the hydrolysis of nicotinamide nucleotides in the oocyte to ADP-ribose and that this mechanism is responsible for the production of the fertilization current.
authors.affiliation: Stazione Zoologica "Anton Dohrn," 80121 Naples, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Wilding
authors.forename: G L
authors.initials: GL
authors.lastname: Russo
authors.forename: A
authors.initials: A
authors.lastname: Galione
authors.forename: M
authors.initials: M
authors.lastname: Marino
authors.forename: B
authors.initials: B
authors.lastname: Dale
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002463:Cell Membrane Permeability; D002614:Chelating Agents / Q000494:pharmacology; D002938:Ciona intestinalis / Q000502:physiology*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004553:Electric Conductivity; D005260:Female; D005306:Fertilization / Q000502:physiology*; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009243:NAD / Q000494:pharmacology; D009249:NADP / Q000494:pharmacology; D009536:Niacinamide / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D012964:Sodium / Q000378:metabolism
chemical_list: D002614:Chelating Agents; D007473:Ion Channels; D009243:NAD; D000246:Adenosine Diphosphate Ribose; D009536:Niacinamide; D004533:Egtazic Acid; D009249:NADP; D012964:Sodium; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium