DYNAMICS OF THE ACTIN CYTOSKELETON IN OSTEOCLASTS

描述（由申请人提供）：项目总结：通过严格控制骨形成和骨降解的平衡来实现骨强度。负责这种受调节的降解的细胞是破骨细胞，单核细胞谱系的大的多核细胞。破骨细胞经历包括迁移、极化、骨吸收和去极化的活动周期。这些事件需要整合素的参与和肌动蛋白细胞因子的广泛重排。破骨细胞不能经历这些过程会导致细胞功能减弱，并对骨骼健康造成潜在的严重后果，如骨硬化症。这个建议的目的是检查动态的肌动蛋白细胞骨架在破骨细胞的迁移和极化等事件，并了解这方面的正常破骨细胞功能所需的细胞元素。这个建议的第一个目的是针对分子运动肌球蛋白IIA，这是密切相关的动态肌动蛋白结构参与破骨细胞迁移和极化。通过抑制其活性和跟踪其在活细胞中的运输，将评估该马达的潜在功能。第二个目标的目标是针对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涉及细胞信号通路。最后，我们确定了在破骨细胞中具有明确分布的原肌球蛋白的亚型。原肌球蛋白是一种丝状蛋白质，可以调节肌动蛋白的稳定性，以及它对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这些原肌球蛋白的表达来检查它们的功能，并确定对破骨细胞肌动蛋白重排的影响。这些研究将提供新的理解，在这个动态的细胞类型的肌动蛋白细胞骨架介导的关键过程。相关性：骨形成和降解的持续过程必须保持平衡，以保持骨骼健康。骨降解是由称为破骨细胞的细胞进行的，破骨细胞依赖于其内部形状和结构的变化来进行活动。这项工作的目的是了解一些调节破骨细胞形状的蛋白质，作为更大努力的一部分，以了解这些细胞的活性是如何调节的。

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.