Abstract
BackgroundThe timely onset of powerful uterine contractions during parturition occurs through thick and thin filament interactions, similar to other smooth muscle tissues. Calponin is one of the thin filament proteins. Phosphorylation of calponin induced by PKC-epsilon can promote the contraction of vascular smooth muscle. While the mechanism by which calponin regulates the contraction of pregnant myometrium has rarely been explored. Here, we explore whether PKC-epsilon/h1 calponin pathway contribute to regulation of myometrial contractility and development of parturition.MethodsWe detected the expression of h1 calponin, phosphorylated h1 calponin, PKC-epsilon and phosphorylated PKC-epsilon in the different stages of mice during pregnancy and in labor by the method of western blot and recorded the contraction activity of myometrium strips at the 19th day during pregnancy with different treatments by the organ bath experiments.ResultsThe level of the four proteins including h1 calponin, phosphorylated h1 calponin, PKC-epsilon and phosphorylated PKC-epsilon was significantly increased in pregnant mice myometrium as compared with that in nonpregnant mice. The ratios of phosphorylated h1 calponin/h1 calponin and phosphorylated PKC-epsilon/PKC-epsilon were reached the peak after the onset of labor in myometrium in the mice. After the treatment of more than 10(9-) mol/L Psi-RACK (PKC-epsilon activator), the contractility of myometrium strips from mice was reinforced and the level of phosphorylated h1 calponin increased at the same time which could be interrupted by the specific inhibitor of PKC-epsilon. Meanwhile, the change of the ratio of phosphorylated h1 calponin/h1 calponin was consistent with that of contraction force of mice myometrium strips.ConclusionsThese data suggest that in mice myometrium, phosphorylation of h1 calponin induced by the PKC-epsilon might facilitate the contraction of uterine in labor and regulate pregnant myometrial contractility.
Highlights
The timely onset of powerful uterine contractions during parturition occurs through thick and thin filament interactions, similar to other smooth muscle tissues
The expression and phosphorylation of h1 calponin were increased during pregnancy and labor We explored the expression level of h1 calponin and phospho-h1 calponin in the samples of myometrium strips from nonpregnant mice or pregnant mice in different stages of pregnancy by the method of western blot with h1 calponin and phospho- h1 calponin (p- h1 calponin) antibodies
The phospho-h1 calponin levels were significantly expressively increased in mice myometrium from the 17th Day during pregnancy till the labor in contrast with that in nonpregnant mice
Summary
The timely onset of powerful uterine contractions during parturition occurs through thick and thin filament interactions, similar to other smooth muscle tissues. Phosphorylation of calponin induced by PKC-epsilon can promote the contraction of vascular smooth muscle. We explore whether PKC-epsilon/h1 calponin pathway contribute to regulation of myometrial contractility and development of parturition. Several contractile-associated proteins have been proposed to contribute to reversal of quiescence and promote contraction of the uterus during homologous genes: a basic calponin (smooth musclespecific basic CaP, h1-calponin, h1 CaP) [5], a neutral calponin (h2-calponin) [6] and an acidic Calponin (h3 calponin) [7]. A series of animal experiments have been conducted about the role of calponin in smooth muscle contraction, the findings show the h1 calponin is specific to differentiated smooth muscle cells and up-regulated during post-natal development [8], which consistent with a role in contractile function. It has been postulated that agonist-induced, Ca2 + -independent contraction of smooth muscle is mediated by PKC-ε through its ability to phosphorylate calponin
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