REGULATION OF MYOMETRIAL RELAXATION: AGONIST-SPECIFIC cGMP ACTION

描述（由申请人提供）：我们的研究目的是确定早产时人类子宫肌层独有的信号转导机制或其改变，因为这是目前尚不清楚的，而且目前对早产（PTL）的治疗完全不足。无论任何女性PTL的病因（胎儿或母体）有何不同，在无法解释的病例中，子宫肌层信号通路或其激活/失活的时间都不可避免地会发生变化。我们将在人类和豚鼠肌层细胞和组织中采用实验方法，以了解早产的平滑肌机制，并提供一个或多个以前未知的治疗靶点。因为肌痛静止与一氧化氮诱导的cGMP升高无关；虽然颗粒观酰环化酶的肽激活剂（pGC-Type C）以cGMP依赖的方式放松肌层，但我们认为目前对cGMP在肌平滑肌中的作用的理解存在一个难题。我们将研究pGC激活后cGMP升高的假设，并在不同于可溶性胍基环化酶的隔室中起作用。我们认为肌层pGC被划分为肌细胞小泡和/或富含脂质的膜筏，并与已知的PKG增加钙进入肌浆网的能力一起，通过PKGII型激活肌球蛋白磷酸酶（MP）同工酶，该酶含有亮氨酸拉链，允许其被PKGII激活。这反过来降低rMLC的磷酸化，从而促进子宫肌的松弛。肌层被可溶性胍基环化酶激活剂松弛，虽然导致cGMP的积累，但这是在与富含脂质信号域不平衡的可溶性腔室中进行的，尽管PKGI被激活，但不会导致MP的激活。我们认为，细胞可溶性区室中的cGMP不通过PKGI调节肌平滑肌的松弛。从生理、生化和分子等方面探讨子宫平滑肌的假说，有助于进一步了解子宫肌静息的调控机制。发现子宫肌层信号的精确和独特性质将有助于更好地理解分娩和早产的调节，并可能导致PTL的新治疗靶点。

DESCRIPTION (provided by applicant): Our research objective is to determine the signal transduction mechanisms that are unique to, or altered in the human myometrium in preterm labor because this is presently unknown and because current treatments for premature labor (PTL) are wholly inadequate. No matter the varied causes of PTL (fetal or maternal) in any given woman, in unexplained cases, changes will inevitably be found in myometrial signaling pathways or the timing of their activation/inactivation. We will take experimental approaches in human and guinea pig myometrial cells and tissues that will converge in an understanding of the smooth muscle mechanisms of prematurity and provide one or more therapeutic targets not previously known. Because myometrial quiescence is independent of nitric oxide induced global elevations of cGMP; while the peptide activator of particulate guanylyl cyclase (pGC-Type C) relaxes the myometrium in a cGMP-dependent fashion, we suggest that a conundrum exists in our current understanding of cGMP action in myometrial smooth muscle. We will investigate the hypothesis that the cGMP elevation following activation of pGC exists and acts in a compartment distinct from that of soluble guanylyl cyclase. We propose that myometrial pGC is compartmented to myocyte caveolae and/or lipid-rich membrane rafts and, together with the known ability of PKG to increase the uptake of calcium into sarcoplasmic reticulum, acts via PKG Type II to activate a myosin phosphatase (MP) isozyme containing a leucine zipper that permits its activation by PKGII. This in turn lowers the phosphorylation of the rMLC and thus promotes relaxation of uterine muscle. Relaxation of the myometrium by activators of soluble guanylyl cyclase, while leading to the accumulation of cGMP, does so in a soluble compartment that is not in equilibrium with the lipid-rich signaling domain and does not lead to activation of MP despite activation of PKGI. We propose that cGMP in the soluble compartment of the cell acting via PKGI does not regulate relaxation of myometrial smooth muscle. Exploring our hypotheses in uterine smooth muscle with physiological, biochemical and molecular methods will further our understanding of the regulation of myometrial quiescence. Discovery of the precise and unique nature of myometrial signaling will lead to a better understanding of the regulation of labor and preterm labor and may lead to new therapeutic targets in PTL.