THE ROLE OF THE BKCA CHANNEL IN THE REGULATION OF UTERINE EXCITABILITY

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 早产仅占所有分娩的10%，但80%以上的新生儿死亡和95%以上的主要新生儿发病率与早产有关。尽管采取了预防措施，但在过去十年中，早产率增加了13%。对子宫收缩的机制和调节缺乏了解，阻碍了早产有效治疗的进展。目前使用的宫缩药物在延长妊娠方面效果不大，提示应研究其他预防早产的方法。已经提出的一类潜在的治疗靶点是K+通道，因为它们能够有效地缓冲细胞的兴奋。电生理学研究表明，子宫肌层细胞含有多种类型的K+通道，可能成为潜在的治疗靶点，包括大电导钙激活的K+通道(BKCa通道)。BKCa通道在子宫收缩中起重要作用。阻断BKCa通道可使子宫肌层细胞去极化并增加收缩活动，而开放剂则可诱导子宫松弛。此外，这些通道被β-肾上腺素能药物和其他子宫松弛药激活。在分娩过程中的人子宫肌层中发现了一种在电导特性上与BKCa通道相似，但缺乏电压和钙敏感性的通道，它可能代表着与其β亚基解偶联的BKCa通道，它介导了对该通道的钙和电压敏感性。因此，BKCa通道调节的一个值得研究的潜在方面是，最近发现的辅助β亚基在调节怀孕期间这些通道的属性和功能中可能起到的作用。本研究的目的是确定分娩过程中BKCa通道的分子结构，并阐明K+通道β亚基在调节子宫活动中所起的作用。其具体目的是：1)确定分娩期间人BKCa通道转录本的表达模式；2)表征分娩期间子宫肌层中BKCaα和β亚基蛋白的表达；以及3)表征分娩时人子宫组织中BKCa通道α和β亚基的表达和组装。这些实验将使用分子和生化方法来确定调节子宫兴奋性的BKCa通道机制。这些研究将确定该通道在分娩过程中的重要性，并确定该通道作为子宫肌膜复极的潜在介体和宫缩治疗的可能靶点的作用。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Preterm births account for only 10% of all deliveries, however are associated with over 80% of newborn deaths and more than 95% of major newborn morbidity. Despite efforts toward prevention, there has been a 13% increase in the rate of preterm births over the past decade. The lack of understanding of the mechanism and regulation of uterine contraction has hampered progress towards an effective treatment for preterm labor. Currently used tocolytic agents have little effect in prolonging gestation, suggesting that other methods of preventing preterm labor should be investigated. One potential class of therapeutic targets that has been proposed is K+ channels due to their ability to potently buffer cell excitation. Electrophysiological reports have shown that myometrial cells contain a variety of K+ channel types that may be potential therapeutic targets, including large-conductance Ca2+-activated K+ channels (BKCa channels). BKCa channels play a significant role in uterine contractility. Block of BKCa channels depolarizes myometrial cells and increases contractile activity, while openers induce uterine relaxation. Additionally, these channels are activated by beta-adrenergic agents and other uterine relaxants. A channel similar to the BKCa channel in conductance properties, but lacking its voltage- and Ca2+ - sensitivity, has been described in human myometrium in labor, and may represent the BKCa channel uncoupled from its beta subunit, which mediates Ca2+ - and voltage-sensitivity to this channel. Therefore, one potential aspect of BKCa channel regulation that should be investigated is the role that the recently identified accessory beta subunits may play in modulating the properties and function of these channels during pregnancy. The objective of this proposal is to determine the molecular architetcture of the BKCa channel during parturition and to elucidate the role that K+ channel beta subunits play in regulating uterine activity. The specific aims are to: 1) determine the expression pattern of the human BKCa channel transcript during parturition; 2) characterize BKCa alpha and beta subunit protein expression in myometrial smooth muscle during parturition; and 3) characterize BKCa channel alpha and beta subunit expression and assembly in human uterine tissue at parturition. These experiments will use molecular and biochemical approaches to define the BKCa channel mechanisms which regulate uterine excitability. The studies will determine the importance of this channel during parturition, and identify the role of this channel as a potential mediator of myometrial membrane repolarization and as a possible target for tocolytic therapy.