MOLECULAR BIOLOGY OF CARDIAC SODIUM/CALCIUM EXCHANGE

心肌细胞的肌膜（质膜）具有高水平的 Na+-Ca 2+交换活性。 Na+-Ca 2+交换是其重要机制 用于调节心肌Ca 2+，从而也调节收缩性。 该实验室最近克隆了Na+-Ca 2+交换器， 交换器的分子分析开始。 的长期目标 本项目旨在了解这些基因的分布、调控和基因表达。 交换器的结构。 为实现这一目标，本项目的具体目标如下：1. 异构体和分布。cDNA克隆代表的亚型的 Na+-Ca 2+交换器将被分离、测序和表达。 同种型 将评估功能和分布。2.调控 的影响 甲状腺激素，慢性洋地黄治疗， 将测定交换蛋白和RNA水平。 这三 所有干预措施都影响Na+-Ca 2+交换活性， 实验将在分子水平上分析这些影响。3.基因 结构 转录调控元件和内含子/外显子 边界将被分析。 上游调控的表征 元件将有助于理解不同基因的调控表达， 交换基因产物。 内含子/外显子图谱有助于理解 进化和蛋白质结构域的关系。4.反义 寡核苷酸 具有与mRNA反义的序列的寡核苷酸 将Na+-Ca 2+交换剂引入细胞中。 这应该能阻止 交换蛋白的合成与兴奋-收缩反应 将分析耦合途径。 Na ~+-Ca ~（2+）交换体是心肌收缩的重要调节因子. 对这种重要的心脏转运蛋白的进一步分子知识将 有助于理解正常和患病心脏的工作原理。

The sarcolemma (plasma membrane) of myocardial cells has high levels of Na+-Ca2+ exchange activity. Na+-Ca 2+ exchange is an important mechanism for regulating myocardial Ca 2+ and thereby also regulates contractility. This laboratory has recently cloned the Na+-Ca 2+ exchanger allowing molecular analysis of the exchanger to begin. The long-term objective of this project is to understand the distribution, regulation, and gene structure of the exchanger. Towards this goal, the specific aims of the project are as follows: 1. Isoforms and distribution. cDNA clones representing isoforms of the Na+-Ca2+ exchanger will be isolated, sequenced and expressed. Isoforms function and distribution will be assessed. 2. Regulation. The effects of thyroid hormone, chronic digitalis treatment, and ischemia on exchanger protein and RNA levels will be determined. These three interventions all affect Na+-Ca2+ exchange activity, and the proposed experiments will analyze these effects at the molecular level. 3. Gene structure. Transcriptional regulatory elements and intron/exon boundaries will be analyzed. Characterization of upstream regulatory elements will aid in understanding the regulated expression of different exchanger gene products. Intron/exon maps are useful in understanding evolutionary and protein domain relationships. 4. Antisense oligonucleotides. Oligonucleotides with sequences antisense to mRNA for the Na+-Ca2+ exchanger will be introduced into cells. This should block synthesis of exchanger protein and the response of excitation-contraction coupling pathways will be analyzed. The Na+-Ca 2+ exchanger is an important regulator of contractility. Further molecular knowledge of this essential cardiac transporter will aid in understanding the workings of both normal and diseased hearts.