DYNAMICS OF THE ACTIN CYTOSKELETON IN OSTEOCLASTS

项目概述：骨骼强度是通过严格控制骨形成和骨降解的平衡来实现的。负责这种调节降解的细胞是破骨细胞，一种单核细胞系的大的多核细胞。破骨细胞经历一个活动周期，包括迁移、极化、骨吸收和去极化。这些事件需要整合素的参与和肌动蛋白细胞骨架的广泛重排。破骨细胞未能完成这些过程会导致细胞功能下降，并可能对骨骼健康造成严重后果，如骨质疏松症。本研究的目的是研究在迁移和极化过程中，破骨细胞中肌动蛋白细胞骨架的动力学，并了解正常破骨细胞这方面功能所需的细胞元素。本研究的第一个目标是针对运动肌球蛋白IIA分子，它与参与破骨细胞迁移和极化的动态肌动蛋白结构密切相关。该马达的潜在功能将通过抑制其活性和跟踪其在活细胞中的运输来评估。第二个目标是了解其他肌球蛋白亚型在破骨细胞中的作用，特别是因为它们可能与细胞信号通路有关。最后，我们在破骨细胞中确定了原肌球蛋白的同种异构体。原肌球蛋白是一种丝状蛋白，可以调节肌动蛋白的稳定性，以及肌动蛋白与其他肌动蛋白结合蛋白的可及性。我们将通过交替抑制或增强原肌球蛋白的表达来研究这些原肌球蛋白的功能，并确定它们对破骨细胞中肌动蛋白重排的影响。这些研究将为这种动态细胞类型中肌动蛋白细胞骨架介导的关键过程提供新的理解。相关性：骨形成和退化的持续过程必须保持平衡，以维持骨骼健康。骨降解是由一种叫做破骨细胞的细胞完成的，破骨细胞依靠其内部形状和结构的变化来保持活性。这项工作的目的是了解一些调节破骨细胞形状的蛋白质，作为理解这些细胞的活性是如何被调节的更大努力的一部分。

DESCRIPTION (provided by applicant): Project Summary: Skeletal strength is achieved through a stringently controlled balance of bone formation and bone degradation. The cells responsible for this regulated degradation are osteoclasts, large multinucleated cells of the monocytic lineage. Osteoclasts undergo a cycle of activity that includes migration, polarization, bone resorption, and depolarization. These events require engagement of integrins and extensive rearrangements of the actin cytoskelton. Failure of osteoclasts to undergo these processes results in diminished cell function and potentially severe consequences to skeletal health such as osteopetrosis. The goal of this proposal is to examine the dynamics of the actin cytoskeleton in osteoclasts during events such as migration and polarization, and to understand the cellular elements required for this aspect of normal osteoclast function. The first aim of this proposal is directed toward the molecular motor myosin IIA, which is closely associated with dynamic actin structures involved in osteoclast migration and polarization. The potential functions of this motor will be assessed both by suppressing its activity and by following its trafficking in living cells. The goal of the second aim is directed toward understanding roles of other myosin isoforms in osteoclasts, particularly as they might pertain to cell signaling pathways. Finally, we have identified isoforms of tropomyosins with defined distributions in osteoclasts. Tropomyosins are filamentous proteins that can regulate the stability of actin, as well as its accessibility to other actin-binding proteins. We will examine the functions of these tropomyosins by alternately suppressing or enhancing their expression, and determining the effects on actin rearrangements in osteoclasts. These studies will provide new understanding of crucial processes mediated by the actin cytoskeleton in this dynamic cell type. Relevance: The ongoing process of bone formation and degradation must be kept in balance to maintain skeletal health. Bone degradation is performed by cells called osteoclasts, which depend on changes in their internal shape and structure for activity. The objective of this work is to understand some of the proteins that regulate the shape of osteoclasts, as part of a greater effort to comprehend how the activity of these cells is regulated.