Activity-dependent alternative splicing increases persistent sodium current and promotes seizure.
Activity-dependent alternative splicing increases persistent sodium current and promotes seizure.
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DOI：
10.1523/jneurosci.6042-11.2012
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发表时间：
2012-05-23
期刊：
影响因子：
--
通讯作者：
Baines RA
中科院分区：
文献类型：
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作者：
Lin WH;Günay C;Marley R;Prinz AA;Baines RA
电压门控钠通道（Nav）的活性被选择性剪接改变。然而，人类Nav 's剪接的改变是否会导致癫痫仍有待最终证实。我们在这里表明，改变剪接的果蝇Nav（麻痹，DmNav）有助于确定癫痫突变体的癫痫样行为。我们将注意力集中在一对互斥的交替外显子（称为K和L）上，它们构成了表达通道III域中电压传感器（S4）的一部分。外显子L的存在导致一个大的、非失活的、持久的INap。许多形式的人类癫痫与这种电流的增加有关。在野生型（WT）果蝇幼虫中，约70-80%的DmNav转录本含有外显子L，其余的含有外显子k。在突变体和易电击突变体中，DmNav剪接包含外显子L的比例增加到约100%。这种剪接的改变是通过暴露于抗癫痫苯妥英或抑制性递质GABA来降低突触活性水平来阻止的。相反，通过喂食微毒素增强WT的突触活性，足以增加INap并通过将外显子L增加到100%来促进癫痫发作。我们还表明，潜在的活性依赖机制需要Pasilla（一种rna结合蛋白）的存在。最后，我们使用计算模型表明，增加INap足以增强与癫痫表型一致的膜兴奋性。因此，突触兴奋的增加有利于外显子L的包含，这反过来又进一步增加了神经元的兴奋性。因此，至少在果蝇中，这种自我强化循环可能会促进癫痫发作的发生。
Activity of voltage-gated Na channels (Nav) is modified by alternative splicing. However, whether altered splicing of human Nav’s contributes to epilepsy remains to be conclusively shown. We show here that altered splicing of the Drosophila Nav (paralytic, DmNav) contributes to seizure-like behaviour in identified seizure-mutants. We focus attention on a pair of mutually-exclusive alternate exons (termed K and L), which form part of the voltage sensor (S4) in domain III of the expressed channel. The presence of exon L results in a large, non-inactivating, persistent INap. Many forms of human epilepsy are associated with an increase in this current. In wildtype (WT) Drosophila larvae ~70-80% of DmNav transcripts contain exon L, the remainder contain exon K. Splicing of DmNav to include exon L is increased to ~100% in both the slamdance and easily-shocked seizure-mutants. This change to splicing is prevented by reducing synaptic activity levels through exposure to the antiepileptic phenytoin or the inhibitory transmitter GABA. Conversely, enhancing synaptic activity in WT, by feeding of picrotoxin, is sufficient to increase INap and promote seizure through increased inclusion of exon L to 100%. We also show that the underlying activity-dependent mechanism requires the presence of Pasilla, an RNA-binding protein. Finally, we use computational modelling to show that increasing INap is sufficient to potentiate membrane excitability consistent with a seizure phenotype. Thus, increased synaptic excitation favors inclusion of exon L which, in turn, further increases neuronal excitability. Thus, at least in Drosophila, this self-reinforcing cycle may promote the incidence of seizure.