Oregon Health and Science University, Portland, Oregon 97239, USA.
J Neurosci. 2013 Apr 24;33(17):7384-92. doi: 10.1523/JNEUROSCI.5839-12.2013.
A long-held tenet of neuromuscular transmission is that calcium-dependent neurotransmitter release is mediated by N-type calcium channels in frog but P/Q-type channels in mammals. The N-type assignment in frog is based principally on pharmacological sensitivity to ω-conotoxin GVIA. Our studies show that zebrafish neuromuscular transmission is also sensitive to ω-conotoxin GVIA. However, positional cloning of a mutant line with compromised neuromuscular function identified a mutation in a P/Q- rather than N-type channel. Cloning and heterologous expression of this P/Q-type channel confirmed a block by ω-conotoxin GVIA raising the likelihood that all vertebrates, including frog, use the P/Q-type calcium channel for neuromuscular transmission. In addition, our P/Q defective mutant line offered a means of testing the ability of roscovitine, known to potentiate frog neuromuscular transmission, to mediate behavioral and functional rescue. Acute treatment led to rapid improvement of both, pointing to potential therapeutic benefit for myasthenic disorders involving calcium channel dysfunction.
神经肌肉传递的一个长期原则是，钙依赖性神经递质释放是由青蛙中的 N 型钙通道介导的，但在哺乳动物中则是由 P/Q 型通道介导的。青蛙中的 N 型分配主要基于对 ω-芋螺毒素 GVIA 的药物敏感性。我们的研究表明，斑马鱼的神经肌肉传递也对 ω-芋螺毒素 GVIA 敏感。然而，对一种神经肌肉功能受损的突变系的定位克隆发现了一种 P/Q 型而不是 N 型通道的突变。该 P/Q 型通道的克隆和异源表达证实了 ω-芋螺毒素 GVIA 的阻断，这增加了所有脊椎动物（包括青蛙）都使用 P/Q 型钙通道进行神经肌肉传递的可能性。此外，我们的 P/Q 缺陷突变系为测试罗昔司特，已知可增强青蛙神经肌肉传递的能力，提供了一种方法来介导行为和功能恢复。急性治疗导致两者迅速改善，这表明对于涉及钙通道功能障碍的肌无力疾病具有潜在的治疗益处。
