Epithelial-Mesenchymal-Transition: roles and regulation of myosin II

描述(申请人提供)：该项目的长期目标是了解细胞如何调节细胞力的产生，从而驱动细胞迁移和其他收缩行为，如侵袭和基质重塑。目前的提交集中在一种上皮向间充质转化(EMT)的模型上，在该模型中，行为上皮的正常小鼠乳腺细胞可以被触发，以响应细胞因子TGFb而切换到间质、更具侵袭性的状态。我们最近发现，在这个乳腺模型的EMT过程中，肌球蛋白II的功能发生了戏剧性的调节，包括非肌肉肌球蛋白II的亚型转换，以及MHC磷酸化的上调。根据我们团队和其他人早期的研究，MHC磷酸化是细胞迁移过程中肌球蛋白II细丝组装控制的关键调节因子，我们的新研究支持这样一个模型，即肌球蛋白II异构体开关和MHC磷酸化可能是增强侵袭性迁移行为和侵袭性的关键介质，而侵袭性是向间充质状态转换的标志。我们提出了一系列的细胞生物学研究，以确定诱导肌球蛋白II亚型(肌球蛋白IIB)的机械作用，以及在EMT过程中诱导的肌球蛋白II重链磷酸化的作用，并确定经历EMT的细胞如何上调肌球蛋白II重链磷酸化。在广泛的水平上，这些研究对于理解细胞如何在正常发育事件中上调其运动行为具有相关性，如中胚层启动和神经管形成。这些研究也与理解发生在乳腺导管形成过程中的发育决定有很强的相关性，在乳腺导管形成过程中，细胞分化为上皮细胞而不是间充质细胞。最后，这些研究对于理解细胞收缩/运动机制在肿瘤进展到转移状态和组织纤维化等病理环境中如何上调具有很强的相关性。

DESCRIPTION (provided by applicant): The long-term goal of this project is to understand how cells regulate cellular force production that drives cell migration and other contractile behaviors such as invasion and matrix remodeling. The current submissions focuses on a model of epithelial-to-mesenchymal transition (EMT), in which normal mouse mammary gland cells, which are epithelial in behavior, can be triggered to switch to a mesenchymal, more invasive state in response to the cytokine TGFb. We have recently discovered dramatic regulation of myosin II functions during EMT in this mammary gland model, including nonmuscle myosin II isoform switch, and an upregulation of MHC phosphorylation. Given earlier studies by our group and others documenting MHC phosphorylation as a critical regulator of myosin II filament assembly control during cell migration, our new studies support a model that myosin II isoform switches and MHC phosphorylation may be critical mediators of the enhanced invasive migration behavior and invasiveness that is a hallmark of the switch to the mesenchymal state. We propose a series of cell biological studies to establish the mechanical role of the induced myosin II isoform (myosin IIB), to establish the role of myosin II heavy chain phosphorylation that is induced during EMT, and to identify how cells that go through EMT upregulate myosin II heavy chain phosphorylation. At a broad level, these studies have relevance for understanding how cells upregulate their motility behavior during normal developmental events such as mesoderm initiation and neural tube formation. These studies also have strong relevance to understanding developmental decisions that occur during mammary ductal formation, where cells differentiate towards epithelial versus mesenchymal fates. Finally, these studies have very strong relevance to understanding how cellular contractile/motility machinery is upregulated in pathological settings such as tumor progression to metastatic states and tissue fibrosis.