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中人类子宫肌层特有或改变的信号转导机制，因为这是目前未知的，并且因为目前对早产（PTL）的治疗完全不足。无论任何特定女性的PTL（胎儿或母体）的不同原因，在无法解释的情况下，子宫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，这些方法将有助于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。由于子宫肌层静止是独立的一氧化氮诱导的全球cGMP的升高，而颗粒鸟苷酸环化酶（pGC-C型）的肽激活剂放松肌层在cGMP依赖的方式，我们认为，一个难题存在于我们目前的了解cGMP的作用在子宫肌层平滑肌。我们将调查的假设，cGMP升高激活后的pGC存在，并在一个不同于可溶性鸟苷酸环化酶的隔室中的行为。我们提出，子宫肌层pGC被分隔成肌细胞小窝和/或富含脂质的膜筏，并且连同PKG增加钙摄入肌浆网的已知能力一起，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，从而允许PKG II激活。这反过来又降低了rMLC的磷酸化，从而促进子宫肌肉的松弛。通过可溶性鸟苷酸环化酶的激活剂的子宫肌层的松弛，同时导致cGMP的积累，在不与富含脂质的信号传导结构域平衡的可溶性隔室中这样做，并且尽管PKGI激活，但不导致MP的激活。我们认为，cGMP在细胞的可溶性隔室通过PKGI作用不调节子宫肌层平滑肌的松弛。从生理学、生物化学和分子生物学的角度探讨子宫平滑肌细胞静止的可能机制，将有助于我们进一步了解子宫平滑肌细胞静止的调控机制。发现子宫肌层信号传导的精确和独特性质将导致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.