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 Ca 2+ and Na + and is characterized by a reversal potential between 0 and +20 mV and a unitary conductance of 140 pS. Preinjection of the Ca 2+ chelator 1,2-bis(2- aminophenoxy)ethane,N,N,N',N'-tetraacetic acid (BAPTA) or antagonists of intracellular Ca 2+ release channels into oocytes did not inhibit the ADP- ribose current, demonstrating that the channel is activated in a Ca 2+- 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.
ADP-ribose gates the fertilization channel in ascidian oocytes
Russo;G L;
1998
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 Ca 2+ and Na + and is characterized by a reversal potential between 0 and +20 mV and a unitary conductance of 140 pS. Preinjection of the Ca 2+ chelator 1,2-bis(2- aminophenoxy)ethane,N,N,N',N'-tetraacetic acid (BAPTA) or antagonists of intracellular Ca 2+ release channels into oocytes did not inhibit the ADP- ribose current, demonstrating that the channel is activated in a Ca 2+- 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.