ADP-ribose gates the fertilization channel in ascidian oocytes.
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.
Wilding
M
M
Stazione Zoologica "Anton Dohrn," 80121 Naples, Italy.
Russo
G L
GL
Galione
A
A
Marino
M
M
Dale
B
B
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
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