Tang Zhen Zhi, Hong Xin, Wang Jing, Soong Tuck Wah
Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Blk MD9, 2 Medical Drive, Singapore 117597, Singapore.
Cell Calcium. 2007 May;41(5):417-28. doi: 10.1016/j.ceca.2006.08.002. Epub 2006 Sep 18.
l-type (Ca(v)1.2) voltage-gated calcium channels play an essential role in muscle contraction in the cardiovascular system. Alternative splicing of the pore-forming Ca(v)1.2 subunit provides potent means to enrich the functional diversity of the channels. There are 11 alternatively spliced exons identified in rat Ca(v)1.2 gene and random rearrangements may generate up to hundreds of combinatorial splicing profiles. Due to such complexity, the real combinatorial splicing profiles of Ca(v)1.2 have not been solved. This study investigated whether the 11 alternatively spliced exons are spliced randomly or linked and if linked, how many combinatorial splicing profiles can be arranged in cardiac- and smooth-muscle cells. By examining three full-length cDNA libraries of the Ca(v)1.2 transcripts isolated from rat heart and aorta, our results showed that the arrangements of some of the alternatively spliced exons are tissue-specific and tightly linked, giving rise to only 41 alternative combinatorial profiles, of which 29 have not been reported. Interestingly, the 41 combinatorial profiles were distinctively distributed in the three Ca(v)1.2 libraries and the one named "heart 1-50" contained unexpected splice variants. Significantly, the tissue-specific cardiac- and smooth-muscle combinatorial splicing profiles of Ca(v)1.2 channels demonstrated distinct electrophysiological properties that may help rationalize the differences observed in native currents. The unique sequences in these tissue-specific splice variants may provide the potential targets for drug design and screening.
L型（Ca(v)1.2）电压门控钙通道在心血管系统的肌肉收缩中起着至关重要的作用。构成孔道的Ca(v)1.2亚基的可变剪接为丰富通道的功能多样性提供了有力手段。在大鼠Ca(v)1.2基因中已鉴定出11个可变剪接外显子，随机重排可能产生多达数百种组合剪接模式。由于这种复杂性，Ca(v)1.2的实际组合剪接模式尚未得到解决。本研究调查了这11个可变剪接外显子是随机剪接还是相互关联的，如果是相互关联的，在心肌细胞和平滑肌细胞中可以排列出多少种组合剪接模式。通过检查从大鼠心脏和主动脉分离的Ca(v)1.2转录本的三个全长cDNA文库，我们的结果表明，一些可变剪接外显子的排列是组织特异性的且紧密相连，仅产生41种替代组合模式，其中29种尚未见报道。有趣的是，这41种组合模式在三个Ca(v)1.2文库中分布明显不同，名为“心脏1-50”的文库包含意外的剪接变体。值得注意的是，Ca(v)1.2通道的组织特异性心肌和平滑肌组合剪接模式表现出明显不同的电生理特性，这可能有助于解释在天然电流中观察到的差异。这些组织特异性剪接变体中的独特序列可能为药物设计和筛选提供潜在靶点。
