REGULATION OF MYOMETRIAL RELAXATION: AGONIST-SPECIFIC cGMP ACTION

描述(申请人提供)：我们的研究目标是确定早产时人类子宫肌层特有或改变的信号转导机制，因为这一点目前尚不清楚，而且目前对早产(PTL)的治疗完全不充分。无论何种原因的PTL(胎儿或母体)，在不明原因的情况下，肌层信号通路或其激活/失活的时间将不可避免地发生变化。我们将在人类和豚鼠子宫肌层细胞和组织中采取实验方法，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。由于子宫肌层的静止不依赖于一氧化氮诱导的cGMP的整体升高，而颗粒鸟苷酸环化酶的多肽激活剂(PGC-Type C)以cGMP依赖的方式松弛肌层，我们认为目前对cGMP在肌层平滑肌中作用的理解存在一个难题。我们将研究这样的假设，即激活PGC后cGMP的升高存在，并且作用在与可溶性鸟苷酸环化酶不同的一个隔室中。我们认为，子宫肌层PGC被划分为肌细胞小窝和/或富脂膜筏，并与已知的PKG增加钙摄取到肌浆网的能力一起，通过PKG II型激活含有亮氨酸拉链的肌球蛋白磷酸酶(MP)同工酶，允许其被PKGII激活。这反过来降低了rMLC的磷酸化，从而促进了子宫肌肉的松弛。可溶性鸟苷酸环化酶激活剂对子宫肌层的松弛作用，虽然导致cGMP的积聚，但在一个与富含脂质的信号结构域不平衡的可溶室中完成，并且不会导致MP的激活，尽管PKGI被激活。我们认为cGMP通过PKGI作用于细胞的可溶室，并不调节子宫肌层平滑肌的松弛。用生理、生化和分子的方法探索我们对子宫平滑肌的假说，将进一步加深我们对子宫肌层静止的调节的理解。肌层信号的精确和独特性质的发现将有助于更好地理解分娩和早产的调节，并可能导致PTL的新的治疗靶点。

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.