A role for annexin V in bone cell mechanotransduction

描述(由申请人提供)：骨骼的物理环境在建立和维护具有结构能力的骨骼方面起着重要作用。然而，物理信号产生这种生物效应的机制尚不清楚。虽然生物物理信号在骨细胞中引发了各种细胞反应，但这些反应的启动机制尚不清楚。在这项研究中，我们认为膜联蛋白V(AnxV)是一种依赖于钙离子的磷脂结合蛋白，是启动机械转导所必需的关键蛋白。AnxV有许多属性，这表明它非常适合作为机械感受器的角色，可能是机械敏感的离子通道。这些功能包括作为钙离子选择性膜离子通道的功能，以及与细胞外基质蛋白(如胶原)和细胞骨架元素(如肌动蛋白)相互作用的能力。 假设：我们的中心假设是，骨细胞通过一种需要AnxV的机制来检测物理信号并将其转化为生物反应。 目的：我们的目标是通过确定AnxV在骨细胞对振荡液体流动的反应中的作用来检验这一假说，振荡液体流动是骨骼中一种与生理相关的物理信号。我们将确定AnxV作为钙离子选择性、机械敏感性离子通道的角色，是否需要在人成骨样MG63细胞和小鼠成骨细胞MLO-Y4细胞(目标1、2和3)中诱导钙内流、钙离子整体增加以及最终基因表达。我们还将确定AnxV的表达和细胞位置是否受液体流动的调节(目标4)。 意义：这些研究的长期目标是增加我们对骨细胞如何选择生物物理信号并将其转化为适当的生物反应的理解。关键的“机械转导”蛋白的识别也可能为未来抗击骨质疏松等骨骼疾病的治疗干预提供新的靶点。

DESCRIPTION (provided by applicant): The physical environment of the skeleton is known to play an important role in the establishment and maintenance of structurally competent bone. However, the mechanisms by which physical signals exert such biological effects are unclear. While biophysical signals elicit a variety of cellular responses in bone cells, the mechanism by which these responses are initiated is unknown. In this study we propose that annexin V (AnxV), a CA2+-dependent phospholipid binding protein, is a critical protein required for initiating mechanotransduction. AnxV has a number of attributes, which suggest that it is ideally suited for a role as a mechanoreceptor, possibly a mechanosensitive ion channel. These include the ability to function as a Ca2+ selective membrane ion channel, and the ability to interact with both extracellular matrix proteins such as collagen, and cytoskeletal elements such as actin. Hypothesis: our central hypothesis is that bone cells detect and transduce physical signals into biological responses via a mechanism requiring AnxV. Aims: Our goal is test this hypothesis by determining the role of AnxV in the response of bone cells to oscillating fluid flow, a physiologically relevant physical signal in bone. We will determine whether AnxV, in a role as a Ca2+ selective, mechanosensitive ion channel, is required for flow-induced Ca2+ influx, global increases in Ca2+i and ultimately gene expression in human osteoblast-like MG63 cells and murine osteocytic MLO-Y4 cells (Aims 1, 2 and 3). We will also determine whether expression and cellular location of AnxV are regulated by fluid flow (Aim 4). Significance: The long-term goal of these studies is to increase our understanding of how biophysical signals are selected and converted into an appropriate biological response by bone cells. Identification of critical "mechanotransducer" proteins may also provide novel targets for future therapeutic interventions in the fight against bone diseases such as osteoporosis.