Analysis of conditional paralytic mutants in Drosophila sarco-endoplasmic reticulum calcium ATPase reveals novel mechanisms for regulating membrane excitability
Analysis of conditional paralytic mutants in Drosophila sarco-endoplasmic reticulum calcium ATPase reveals novel mechanisms for regulating membrane excitability
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DOI：
10.1534/genetics.104.031930
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发表时间：
2005-02-01
期刊：
影响因子：
3.3
通讯作者：
Ramaswami, M
中科院分区：
文献类型：
--
作者：
Sanyal, S;Consoulas, C;Ramaswami, M
不同的钙释放和螯合机制对可兴奋细胞生理学各个方面的贡献还不完全清楚。SERCA是肌质内质网钙ATP酶，是钙摄取进入内质网的主要介质，在此过程中起着核心作用。通过分离和广泛表征果蝇SERCA基因中的条件突变，我们描述了这种关键蛋白在神经肌肉生理学中的新作用，并对SERCA功能进行了遗传分析。在运动神经末梢，SERCA抑制延缓钙螯合并降低诱发兴奋性连接电流的幅度。这表明，在确定诱发释放的量子含量的直接贡献的商店衍生的钙。SERCA突变体的条件性麻痹也以延长的神经活性驱动的肌肉收缩为标志，从而反映了SERCA在终止收缩中的遗传保守作用。对突变体离子电流的进一步分析揭示了调节电压门控钙通道和钙激活钾通道的SERCA依赖性机制，这些通道共同控制肌肉兴奋性。最后，我们的鉴定SERCA中的显性功能丧失突变表明了SERCA在体内的新的分子内和分子间相互作用，被当前的结构模型所忽视。
Individual contributions made by different calcium release and sequestration mechanisms to various aspects of excitable cell physiology are incompletely understood. SERCA, a sarco-endoplasmic reticulum calcium ATPase, being the main agent for calcium uptake into the ER, plays a central role in this process. By isolation and extensive characterization of conditional mutations in the Drosophila SERCA gene, we describe novel roles of this key protein in neuromuscular physiology and enable a genetic analysis of SERCA function. At motor nerve terminals, SERCA inhibition retards calcium sequestration and reduces the amplitude of evoked excitatory junctional currents. This suggests a direct contribution of store-derived calcium in determining the quantal content of evoked release. Conditional paralysis of SERCA mutants is also marked by prolonged neural activity-driven muscle contraction, thus reflecting the phylogenetically conserved role of SERCA in terminating contraction. Further analysis of ionic currents from mutants uncovers SERCA-dependent mechanisms regulating voltage-gated calcium channels and calcium-activated potassium channels that together control muscle excitability. Finally, our identification of dominant loss-of-function mutations in SERCA indicates novel intra- and intermolecular interactions for SERCA in vivo, overlooked by current structural models.