Collagen-Annexin Interactions in Tissue Mineralization

本研究的长期目标是阐明膜联蛋白II、V和VI在软骨细胞终末分化中的作用，以及膜联蛋白V与II型和X型胶原的相互作用。生长板软骨细胞的终末分化包括矿化和细胞程序性死亡(凋亡)等一系列事件。这些事件在正常的骨形成过程中起着至关重要的作用。然而，如果它们发生在病理条件下，如骨关节炎，它们将导致软骨破坏。因此，了解控制软骨细胞终末分化的细胞机制是非常重要的。上一次筹资期间的重大进展导致了以下三个新的假说，将在当前的提案中得到检验：(I)生长板软骨细胞质膜上膜联蛋白通道的形成以及由II型和X型激活的膜联蛋白V通道 (Ii)最佳的膜联蛋白通道形成和膜联蛋白V/胶原的相互作用需要膜联蛋白II、V和VI之间的相互作用；(Iii)膜联蛋白介导的钙稳态变化调节生长板软骨细胞的终末分化事件。这些假说将通过以下具体目标得到解决：1.我们将确定膜联蛋白II、V和VI通道的形成以及膜联蛋白V/胶原相互作用在生长板软骨细胞钙稳态改变中的作用，并测试通过与胶原和细胞骨架结合的膜联蛋白是否在这些细胞中起机械传感器的作用。2.我们将确定膜联蛋白II、V和VI之间的相互作用可能是膜联蛋白通道形成的主要调节因素，以及膜联蛋白V/胶原蛋白的相互作用。3.我们将确定监管角色 Annexins和Annexin V/胶原在终末分化事件中的相互作用，包括生长板软骨细胞的矿化和凋亡。本研究直接涉及控制软骨细胞终末分化的机制，并探索了一种新的调节骨骼细胞内钙稳态的机制。因此，这一建议不仅将极大地促进我们对终末分化事件如何调控的理解，而且可能为在病理条件下预防终末分化事件提供新的治疗靶点。

Our long term goal of this study is to elucidate the roles of annexins II, V and VI and the interactions between annexin V and types II and X collagen in terminal differentiation events of chondrocytes. Terminal differentiation of growth plate chondrocytes consists of a series of events including mineralization and programmed cell death (apoptosis). These events play a crucial role during normal bone formation. If they, however, occur during pathological conditions, such as osteoarthritis, they will lead to cartilage destruction. Thus, an understanding of the cellular mechanisms controlling terminal differentiation of chondrocytes is of great importance. Major advances during the last funding period led to the following three new hypotheses which will be tested in the current proposal: (i) annexin channel formation in the plasma membrane of growth plate chondrocytes and annexin V channel activation by types II and X :ollagen lead to calcium influx into growth plate chondrocytes and alteration of calcium homeostasis; (ii) optimal annexin channel formation and annexin V/collagen interactions require the interactions between annexin II, V and VI; (iii) annexin-mediated alteration of calcium homeostasis regulates terminal differentiation events of growth plate chondrocytes. These hypotheses will be addressed through the following specific aims: 1. We will determine the function of annexin II, V and VI channel formation and annexin V/collagen interactions in alteration of calcium homeostasis in growth plate chondrocytes and test whether annexins through binding to collagen and cytoskeleton act as mechanosensors in these cells. 2. We will determine the interactions between annexin II, V and VI as a possible major regulator of annexin channel formation and annexin V/collagen interactions. 3. We will determine the regulatory roles of annexins and annexin V/collagen interactions in terminal differentiation events including mineralization and apoptosis of growth plate chondrocytes.This study relates directly to the mechanisms which control terminal differentiation of chondrocytes and investigates a novel mechanism regulating calcium homeostasis in skeletal cells.Thus, this proposal will not only greatly advance our understanding of how terminal differentiation events are regulated, but it might also provide novel therapeutic targets to prevent terminal differentiation events during patholoaical conditions.