A NOVEL MOLECULAR MECHANISM FOR STIMULATING UTERINE CONTRACTILITY BY OXYTOCIN

 描述（由申请人提供）：适当的分娩时机对新生儿和母亲的即时和终身健康都很重要，但这一事件往往时机不当;在美国，大约12%的婴儿早产，多达10%的怀孕被描述为过期妊娠。在妊娠的大部分时间里，子宫保持静止、非收缩状态，其中子宫肌层平滑肌细胞（MSMCs）处于超极化、非兴奋和静止状态。在足月时，MSMC变得去极化、兴奋和收缩。目前，我们对如何控制这种转变的理解有限，这阻碍了我们治疗功能失调性分娩的能力。许多离子通道在MSMCs中表达，并有助于调节子宫兴奋性。特别是，K+通道通过超极化膜来控制MSMC膜电位，从而在维持静止中发挥重要作用。控制MSMC兴奋性的另一个关键调节因子是催产素，它与催产素受体（OTR）结合，OTR是一种Gα q偶联的G蛋白偶联受体（GαqCR）。结果，蛋白激酶C（PKC）被激活，Ca 2+从细胞内储存释放，引起肌动球蛋白收缩的激活。此外，已经提出催产素通过电压依赖性钙通道通过使MSMC质膜去极化来触发Ca 2+内流。然而，负责这种去极化的分子机制尚未建立。在这里，我们建议验证中心假设，即钠激活的K+通道SLO2.1在控制MSMC的静息膜电位方面发挥关键作用，并且其活性在足月时通过催产素介导的抑制或表达减少而下调，导致膜去极化。有几条证据支持这一假设。首先，我们的初步数据表明，SLO 2.1在人MSMCs中表达。其次，我们报告说，SLO 2.1活性调制催产素在异源系统和MSMCs。最后，已知SLO2.1受GαqCRs调控。本项目的目标是：1）确定平滑肌细胞中SLO 2.1通道的时空分布，2）研究催产素对SLO 2.1通道的调节; 3）评估SLO 2.1通道对子宫收缩力调节的贡献。 这项研究将建立调节SLO 2.1活性的分子通路，为调节子宫兴奋性的治疗提供生物学基础。

 DESCRIPTION (provided by applicant): Proper timing of delivery is important to the immediate and life-long health of both the newborn and the mother, but this event is often mistimed; in the U.S., approximately 12% of babies are born prematurely and up to 10% of pregnancies are described as post-term. For most of pregnancy, the uterus is maintained in a quiescent, non-contractile state in which the myometrial smooth muscle cells (MSMCs) are hyperpolarized, non-excitable, and quiescent. At term, the MSMCs become depolarized, excitable, and contractile. Currently, our limited understanding of how this transition is controlld hampers our ability to treat dysfunctional labor. Numerous ion channels are expressed in the MSMCs and contribute to regulation of uterine excitability. In particular, K+ channels play an important role in maintaining quiescence by controlling MSMC membrane potential by hyperpolarizing the membrane. Another key regulator in control of MSMC excitability is the hormone oxytocin, which binds to the oxytocin receptor (OTR), a Gαq-coupled G-protein coupled receptor (GαqCR). As a result, Protein Kinase C (PKC) is activated and Ca2+ is released from intracellular stores, causing activation of actomyosin contraction. Additionally, it has been proposed that oxytocin triggers Ca2+ influx through voltage-dependent calcium channels by depolarizing the MSMC plasma membrane. However, the molecular mechanism responsible for this depolarization has not been established. Here, we propose to test the central hypothesis that the sodium-activated K+ channel SLO2.1 plays a key role in controlling the resting membrane potential of MSMCs and that its activity is down-regulated at term by either oxytocin-mediated inhibition or decreased expression, resulting in membrane depolarization. Several lines of evidence support this hypothesis. First, our preliminary data indicate that SLO2.1 is expressed in human MSMCs. Second, we report that SLO2.1 activity is modulated by oxytocin in both heterologous systems and MSMCs. Finally, SLO2.1 is known to be regulated by GαqCRs. The goals of this projects are the 1) define the temporal and spatial distribution of SLO2.1 channels in MSMCs, 2) investigate modulation of SLO2.1 channels by oxytocin; and 3) assess the contribution of SLO2.1 channels to regulation of uterine contractility. The research proposed here will establish the molecular pathways that regulate SLO2.1 activity, providing a biological basis for therapies designed to modulate uterine excitability.