Smooth muscle-selective alternatively spliced exon generates functional variation in Cav1.2 calcium channels
Smooth muscle-selective alternatively spliced exon generates functional variation in Cav1.2 calcium channels
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DOI：
10.1074/jbc.m409436200
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发表时间：
2004-11-26
影响因子：
4.8
通讯作者：
Soong, TW
中科院分区：
文献类型：
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作者：
Liao, P;Yu, DJ;Soong, TW
电压门控钙通道在肌肉收缩、神经传递、兴奋-转录偶联和激素分泌等许多重要过程中发挥重要作用。迄今为止，已经报道了10个钙通道α(1)亚基，其中4个为l型钙通道编码。在我们之前的工作中，我们通过转录扫描发现在l型Ca(v)1.2 α(1)-亚基中存在19个可选剪接的外显子。在这里，我们报道了在动脉平滑肌Ca(v)1.2通道中发现的选择性剪接外显子9*的平滑肌选择性表达。针对9*外显子的特异性多克隆抗体定位了含9*的Ca(v)1.2通道在动脉平滑肌壁上的强烈表达，但在心肌中的表达较低。HEK293细胞中含有9*的Ca(v)1.2通道的全细胞膜片钳记录显示，在电压依赖性激活和电流-电压关系中，分别有-9和-11 mv的超极化移位。然而，+/-外显子9*剪接变异体的稳态失活特性和对硝苯地平阻断的敏感性没有显著差异。这种选择性剪接外显子的细胞选择性表达强烈表明，通过选择性剪接形成孔的α(1)-亚基，钙通道功能的定制和微调。通过钙通道Ca(v)1.2 α(1)亚基的选择性剪接产生的蛋白质组学变异可能为肌肉或神经元细胞响应各种生理信号或疾病提供一种灵活的机制。
Voltage-gated calcium channels play a major role in many important processes including muscle contraction, neurotransmission, excitation-transcription coupling, and hormone secretion. To date, 10 calcium channel alpha(1)-subunits have been reported, of which four code for L-type calcium channels. In our previous work, we uncovered by transcript-scanning the presence of 19 alternatively spliced exons in the L-type Ca(v)1.2 alpha(1)-subunit. Here, we report the smooth muscle-selective expression of alternatively spliced exon 9* in Ca(v)1.2 channels found on arterial smooth muscle. Specific polyclonal antibody against exon 9* localized the intense expression of 9*-containing Ca(v)1.2 channels on the smooth muscle wall of arteries, but the expression on cardiac muscle was low. Whole-cell patch clamp recordings of the 9*-containing Ca(v)1.2 channels in HEK293 cells demonstrated -9 and -11-mV hyperpolarized shift in voltage-dependent activation and current-voltage relationships, respectively. The steady-state inactivation property and sensitivity to blockade by nifedipine of the +/-exon 9* splice variants were, however, not significantly different. Such cell-selective expression of an alternatively spliced exon strongly indicates the customization and fine tuning of calcium channel functions through alternative splicing of the pore-forming alpha(1)-subunit. The generation of proteomic variations by alternative splicing of the calcium channel Ca(v)1.2 alpha(1)-subunit can potentially provide a flexible mechanism for muscle or neuronal cells to respond to various physiological signals or to diseases.