In adult Hydra, epitheliomuscle cells form the monolayered ecto- and endodermal epithelia. Their basal myonemes function as a longitudinal and circular muscle, respectively. Based on the observation that a Rho/Rock pathway, controlling the cell shape changes during detachment of Hydra buds, is not involved in body movement, at least two actomyosin compartments must exist in these cells: a basal one for body movement and a cortical one for cell shape changes. We therefore analyzed the regional and subcellular localization of the Ser19-phosphorylated myosin regulatory light chain (pMLC20). Along the body column, pMLC20 was detected strongly in the basal myonemes and weakly in the apical cell compartments of ectodermal epitheliomuscle cells. In cells of the bud base undergoing morphogenesis, pMLC20 was localized to intracellular stress fibers as well as to the apical and additionally to the lateral cortical compartment. Pharmacological inhibition revealed that pMLC20 is induced in these compartments by at least two independent pathways. In myonemes, MLC is phosphorylated mainly by myosin light chain kinase (MLCK). In contrast, the cortical apical and lateral MLC phosphorylation in constricting ectodermal cells of the bud base is stimulated via the Rho/ROCK pathway.

中文翻译：

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替代途径控制形态发生和身体收缩过程中上皮肌细胞中的肌动球蛋白收缩能力。

在成年的九头蛇中，上皮肌细胞形成单层外胚层和内胚层上皮。它们的基底肌层分别起纵向和环状肌的作用。根据观察，在九头蛇芽脱落过程中控制细胞形状变化的Rho / Rock途径不参与人体运动，这些细胞中必须至少存在两个肌动球蛋白区室：一个用于细胞运动的基础肌动蛋白区，一个用于皮质运动的肌动蛋白区室。改变细胞形状。因此，我们分析了Ser19-磷酸化肌球蛋白调节轻链（pMLC20）的区域和亚细胞定位。沿体柱，在外胚层上皮肌细胞的基底肌层中强烈检测到pMLC20，而在根尖细胞室中检测到弱。在发生形态发生的芽基细胞中，pMLC20定位于细胞内应力纤维以及根尖和皮质外侧隔室。药理学抑制作用表明，至少有两个独立的途径在这些区室中诱导了pMLC20。在肌群中，MLC主要被肌球蛋白轻链激酶（MLCK）磷酸化。相比之下，通过Rho / ROCK途径刺激收缩芽基的外胚层细胞中的皮质顶和外侧MLC磷酸化。