Wilding M, Russo G L, Galione A, Marino M, Dale B
Stazione Zoologica "Anton Dohrn," 80121 Naples, Italy.
Am J Physiol. 1998 Nov;275(5):C1277-83. doi: 10.1152/ajpcell.1998.275.5.C1277.
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.
我们报道了在海鞘玻璃海鞘未受精卵母细胞质膜中的一种离子通道，它直接由第二信使ADP-核糖门控。该离子通道对Ca2+和Na+通透，其特征在于反转电位在0至+20 mV之间，单位电导为140 pS。将Ca2+螯合剂1,2-双(2-氨基苯氧基)乙烷-N,N,N',N'-四乙酸(BAPTA)或细胞内Ca2+释放通道拮抗剂预先注射到卵母细胞中并不抑制ADP-核糖电流，表明该通道以不依赖Ca2+的方式被激活。受精电流和注射烟酰胺核苷酸诱导的电流都被烟酰胺阻断，表明ADP-核糖通道在受精时以烟酰胺敏感的方式被激活。这些数据表明，海鞘精子触发卵母细胞中烟酰胺核苷酸水解为ADP-核糖，并且这种机制负责受精电流的产生。
