Skeletal muscle contraction depends on activation of clustered acetylcholine receptors (AchRs) and muscle-specific Na⁺ channels (Nav1.4). Some Nav1.4 channels are highly enriched at the neuromuscular junction (NMJ), and their clustering is thought to be essential for effective muscle excitation. However, this has not been experimentally tested, and how NMJ Na⁺ channels are clustered is unknown. Here, using muscle-specific ankyrinR, ankyrinB, and ankyrinG single, double, and triple-conditional knockout mice, we show that Nav1.4 channels fail to cluster only after deletion of all three ankyrins. Remarkably, ankyrin-deficient muscles have normal NMJ morphology, AchR clustering, sarcolemmal levels of Nav1.4, and muscle force, and they show no indication of degeneration. However, mice lacking clustered NMJ Na⁺ channels have significantly reduced levels of motor activity and their NMJs rapidly fatigue after repeated nerve-dependent stimulation. Thus, the triple redundancy of ankyrins facilitates NMJ Na⁺ channel clustering to prevent neuromuscular synapse fatigue.

骨骼肌收缩取决于成簇乙酰胆碱受体 (AchRs) 和肌肉特异性 Na ⁺通道 (Nav1.4) 的激活。一些 Nav1.4 通道在神经肌肉接头 (NMJ) 处高度富集，并且它们的聚集被认为对于有效的肌肉兴奋是必不可少的。然而，这还没有经过实验测试，NMJ Na ⁺通道是否聚集是未知的。在这里，我们使用肌肉特异性 ankyrinR、ankyrinB 和 ankyrinG 单、双和三条件敲除小鼠，表明 Nav1.4 通道只有在删除所有三个锚蛋白后才能聚集。值得注意的是，缺乏锚蛋白的肌肉具有正常的 NMJ 形态、AchR 聚集、Nav1.4 的肌膜水平和肌肉力量，并且它们没有显示出退化的迹象。然而，缺乏聚集的 NMJ Na ⁺通道的小鼠运动活动水平显着降低，并且在反复神经依赖性刺激后，它们的 NMJ 会迅速疲劳。因此，锚蛋白的三重冗余有利于 NMJ Na ⁺通道聚集以防止神经肌肉突触疲劳。