Drosophila QVR/SSS modulates the activation and C-type inactivation kinetics of Shaker K(+) channels.
Drosophila QVR/SSS modulates the activation and C-type inactivation kinetics of Shaker K(+) channels.
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DOI：
10.1523/jneurosci.0502-11.2011
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发表时间：
2011-08-03
期刊：
影响因子：
--
通讯作者：
Hoshi T
中科院分区：
文献类型：
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作者：
Dean T;Xu R;Joiner W;Sehgal A;Hoshi T
不眠/失眠（qvr/sss）基因编码一种小的糖基磷脂酰肌醇锚定蛋白，在果蝇的睡眠调节中起着关键作用。qvr/sss中的功能丧失突变严重抑制睡眠，并影响原位Shaker K+电流的多种变化，包括幅度降低、达到峰值的时间变慢和累积失活。最近，我们证明了SLEEPLESS（SSS）蛋白可能通过与质膜的直接相互作用来调节Shaker通道的活性。我们在这里表明，SSS加速异源表达的振荡器通道的激活，对失活或快速N型失活没有影响。此外，这种SSS诱导的加速对脂筏的药理学破坏敏感，并充分解释了在qvr/sss突变体中观察到的原位Shaker电流达到峰值的时间较慢。我们还发现SSS降低异源表达的Shaker通道的C型失活速率，为qvr/sss功能丧失突变诱导的累积失活表型提供了潜在机制。基于体外结果的动力学建模表明，SSS依赖性调节通道动力学占近40%的减少，在缺乏SSS的苍蝇振动电流幅度。qvr/sss无效突变体中的睡眠持续时间通过qvr/sss转基因恢复正常，该转基因完全挽救了Shaker动力学表型，但仅部分挽救了电流幅度的降低。总之，这些结果表明，SSS在调节果蝇睡眠中的作用与SSS对Shaker动力学的影响比电流大小更密切相关。
The quiver/sleepless (qvr/sss) gene encodes a small, glycosylphosphatidylinositol-anchored protein that plays a critical role in the regulation of sleep in Drosophila. Loss-of-function mutations in qvr/sss severely suppress sleep and effect multiple changes in in situ Shaker K+ currents, including decreased magnitude, slower time-to-peak, and cumulative inactivation. Recently, we demonstrated that SLEEPLESS (SSS) protein modulates Shaker channel activity, possibly through a direct interaction at the plasma membrane. We show here that SSS accelerates the activation of heterologously expressed Shaker channels with no effect on deactivation or fast N-type inactivation. Furthermore, this SSS-induced acceleration is sensitive to the pharmacological disruption of lipid rafts and sufficiently accounts for the slower time-to-peak of in situ Shaker currents seen in qvr/sss mutants. We also find that SSS decreases the rate of C-type inactivation of heterologously expressed Shaker channels, providing a potential mechanism for the cumulative inactivation phenotype induced by qvr/sss loss of function mutations. Kinetic modeling based on the in vitro results suggests that the SSS-dependent regulation of channel kinetics accounts for nearly 40% of the decrease in Shaker current magnitude in flies lacking SSS. Sleep duration in qvr/sss null mutants is restored to normal by a qvr/sss transgene that fully rescues the Shaker kinetic phenotypes but only partially rescues the decrease in current magnitude. Together, these results suggest that the role of SSS in the regulation of sleep in Drosophila correlates more strongly with the effects of SSS on Shaker kinetics than current magnitude.