Cav1.2 Transcript Regulation in Heart and Smooth Muscle

描述（由申请人提供）：已发现人心脏L型钙通道的新的第一外显子，使发现的具有不同5'末端的转录物的数量达到三个，每个转录物可能由其自身的启动子调节。其中两个转录本具有重要意义，因为它们分别占心脏和平滑肌中转录本的大部分。该补助金假设，这两个主要的转录在心脏和血管和内脏平滑肌的差异表达不仅产生显着差异的通道活性，蛋白激酶C的敏感性和稳态失活，但也有更大的能力，分别调节表达的三种组织类型。已知肾上腺素能药物在心脏中转录上调然后下调该通道，但缺乏平滑肌的等效信息。本基金将检验三个特定的假设：1）在非洲爪蟾卵母细胞和人类细胞中异源表达不同的转录本导致具有不同幅度、动力学、开放概率、对蛋白激酶C的敏感性和稳态失活特性的Ca电流; 2）肾上腺素能药物对心脏和平滑肌中两种主要转录本的影响不同; 3）并且存在心脏特异性转录因子，其结合心脏启动子中的通道响应元件，而大多数平滑肌表达由结合其他主通道启动子中的响应元件的其他转录因子驱动。结果将确定不同的N-末端如何影响通道特性，以及不同的转录本如何在血管平滑肌中与心脏和内脏平滑肌不同地调节。它们可以为药物干预涉及L型钙通道表达改变的疾病（如高血压）提供新的靶点。

DESCRIPTION (provided by applicant): A novel first exon for the human cardiac L-type calcium channel has been discovered, bringing to three the number of transcripts found with different 5' ends, each likely regulated by its own promoter. Two of these transcripts are of critical significance, since they account for the majority of transcripts in heart and smooth muscle, respectively. This grant hypothesizes that differential expression of these two principal transcripts in heart and in vascular and visceral smooth muscle not only generates significant differences in channel activity, sensitivity to protein kinase C, and steady-state inactivation but also greater ability to separately regulate expression in the three tissue types. Adrenergic agents are known to transcriptionally upregulate and then downregulate this channel in heart, but equivalent information is lacking for smooth muscle. This grant will test three specific hypotheses: 1) that heterologous expression of the different transcripts in Xenopus oocytes and human cells results in Ca currents with different amplitude, kinetics, open probability, sensitivity to protein kinase C and steady state inactivation properties; 2) that the two principal transcripts are differentially affected in heart and smooth muscle by adrenergic agents; 3) and that there are heart-specific transcription factors that bind to response elements in the heart promoter for the channel, whereas most smooth muscle expression is driven by other transcription factors that bind to response elements in the other principal channel promoter. The results will determine how the different N-termini affect channel properties and how the different transcripts are differentially regulated in vascular smooth muscle as opposed to heart and visceral smooth muscle. They could suggest new targets for pharmaceutical intervention in disorders involving alterations in expression of L-type Ca channels, such as hypertension.