Grotegut Chad A, Mao Lan, Pierce Stephanie L, Swamy Geeta K, Heine R Phillips, Murtha Amy P
Departments of Obstetrics and Gynecology (C.A.G., S.L.P., G.K.S., R.P.H., A.P.M.) and Medicine (L.M.), Duke University, Durham, North Carolina 27710.
Mol Endocrinol. 2016 Apr;30(4):455-68. doi: 10.1210/me.2015-1147. Epub 2016 Feb 17.
Oxytocin is a potent uterotonic agent and is used clinically for induction and augmentation of labor, as well as for prevention and treatment of postpartum hemorrhage. Oxytocin increases uterine contractility by activating the oxytocin receptor (OXTR), a member of the G protein-coupled receptor family, which is prone to molecular desensitization. After oxytocin binding, the OXTR is phosphorylated by a member of the G protein-coupled receptor kinase (GRK) family, which allows for recruitment of β-arrestin, receptor internalization, and desensitization. According to previous in vitro analyses, desensitization of calcium signaling by the OXTR is mediated by GRK6. The objective of this study was to determine the role of GRK6 in mediating uterine contractility. Here, we demonstrate that uterine GRK6 levels increase in pregnancy and using a telemetry device to measure changes in uterine contractility in live mice during labor, show that mice lacking GRK6 produce a phenotype of enhanced uterine contractility during both spontaneous and oxytocin-induced labor compared with wild-type or GRK5 knockout mice. In addition, the observed enhanced contractility was associated with high rates of term stillbirth. Lastly, using a heterologous in vitro model, we show that β-arrestin recruitment to the OXTR, which is necessary for homologous OXTR desensitization, is dependent on GRK6. Our findings suggest that GRK6-mediated OXTR desensitization in labor is necessary for normal uterine contractile patterns and optimal fetal outcome.
催产素是一种强效子宫收缩剂,临床上用于引产和增强宫缩,以及预防和治疗产后出血。催产素通过激活催产素受体(OXTR)增加子宫收缩力,OXTR是G蛋白偶联受体家族的成员,易于发生分子脱敏。催产素结合后,OXTR被G蛋白偶联受体激酶(GRK)家族的成员磷酸化,这允许募集β-抑制蛋白、受体内化和脱敏。根据先前的体外分析,OXTR对钙信号的脱敏由GRK6介导。本研究的目的是确定GRK6在介导子宫收缩中的作用。在这里,我们证明妊娠期间子宫GRK6水平升高,并使用遥测设备测量活鼠分娩期间子宫收缩的变化,结果显示与野生型或GRK5基因敲除小鼠相比,缺乏GRK6的小鼠在自然分娩和催产素诱导的分娩过程中均表现出子宫收缩增强的表型。此外,观察到的收缩增强与足月死产率高有关。最后,使用异源体外模型,我们表明β-抑制蛋白募集到OXTR是同源OXTR脱敏所必需的,这依赖于GRK6。我们的研究结果表明,分娩过程中GRK6介导的OXTR脱敏对于正常的子宫收缩模式和最佳的胎儿结局是必要的。