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

描述（由申请人提供）：该项目的长期目标是了解细胞如何调节驱动细胞迁移和其他收缩行为（如侵袭和基质重塑）的细胞力生产。目前的研究集中在上皮-间质转化（EMT）模型上，在这个模型中，正常的小鼠乳腺细胞是上皮细胞，在细胞因子TGFb的作用下，可以被触发转换到间质，更具侵袭性的状态。我们最近在乳腺模型中发现EMT期间肌球蛋白II功能的显著调节，包括非肌肉肌球蛋白II异构体开关和MHC磷酸化上调。鉴于我们小组和其他人早期的研究记录了MHC磷酸化是细胞迁移过程中肌球蛋白II丝组装控制的关键调节因子，我们的新研究支持了一个模型，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，这是切换到间质状态的标志。我们提出了一系列的细胞生物学研究，以建立诱导的肌球蛋白II亚型（myosin IIB）的机械作用，建立肌球蛋白II重链磷酸化在EMT期间诱导的作用，并确定细胞如何通过EMT上调肌球蛋白II重链磷酸化。在广泛的水平上，这些研究与理解细胞在正常发育事件（如中胚层起始和神经管形成）中如何上调其运动行为有关。这些研究也与理解乳腺导管形成过程中发生的发育决定密切相关，在乳腺导管形成过程中，细胞分化为上皮细胞和间充质细胞。最后，这些研究与理解细胞收缩/运动机制在病理环境（如肿瘤进展到转移状态和组织纤维化）中如何上调有很强的相关性。

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.