Integrin Function in Cartilage

描述（由申请人提供）：本项目的长期目标是确定通过整合素受体产生的信号调节软骨细胞功能的基本机制。驱动这项工作的总体假设是软骨细胞外基质（ECM）的变化，包括ECM蛋白片段的产生，被软骨细胞整联蛋白识别并启动旨在重塑ECM的级联事件，但在关节炎中导致进一步的基质破坏（“软骨细胞软骨溶解”）。的重点 建议是确定基本的细胞机制，控制信号产生通过？五个？1整合素，其调节分解代谢介质包括细胞因子和基质金属蛋白酶（MMP）的产生。在以前的资金期间，我们已经确定了介导MMP-13的生产响应纤连蛋白片段（FN-F）刺激的信号通路？五个？1整合素和已发现的活性氧（ROS）是必需的第二信使。使用创新的蛋白质组学方法，我们发现MAP激酶家族成员JNK 2在FN-f刺激的细胞中被氧化，形成Cys-SOH（次磺酸）中间体。 磺酸的形成是ROS调节细胞信号传导的主要机制，但其在软骨细胞信号传导中的作用尚未研究。在他的竞争性更新中，我们建议确定次磺酸形成调节软骨细胞中JNK 2活性的机制。我们将通过研究JNK 2-/-小鼠中关节炎诱导的OA的发展来确定JNK 2激活在体内OA中的作用。 最后，我们将确定当软骨细胞被FN-f刺激时，HB-EGF是否上调并释放，促进Rac活性以激活增强MMP-13表达和软骨基质破坏的共信号通路。 这些研究将通过定义介导软骨基质破坏的信号网络中的关键枢纽对该领域产生重大影响。通过发现ROS调节这种信号网络的新机制，这些信息可用于开发一种独特的方法来改变关节炎中氧化还原调节的分解代谢信号网络，该方法针对特定的蛋白质修饰。这代表了相对于一般抑制ROS产生的显著进步，一般抑制ROS产生在治疗由过量ROS促进的病症（包括关节炎）中尚未被证明是成功的。 公共卫生相关性：骨关节炎是老年人慢性残疾的最常见原因，但缺乏减缓疾病进展的治疗方法。该项目的结果将提供有关骨关节炎中软骨破坏的基本机制的新信息。需要这些信息来发现新的靶点并开发新的治疗方法来减缓或阻止疾病的进展。

DESCRIPTION (provided by applicant): The long-term goal of this project is to determine the basic mechanisms by which signals generated through integrin receptors regulate chondrocyte function. The overall hypothesis driving this work is that changes in the cartilage extracellular matrix (ECM), including production of ECM protein fragments, are recognized by chondrocyte integrins and initiate a cascade of events intended to remodel the ECM but which in arthritis result in further matrix destruction ("chondrocytic chondrolysis"). The focus of this proposal is to determine the basic cellular mechanisms that control signals generated through the ?5?1 integrin which regulate production of catabolic mediators including cytokines and matrix metalloproteinases (MMPs). During the previous funding period, we have defined the signaling pathways that mediate MMP-13 production in response to fibronectin fragment (FN-f) stimulation of the ?5?1integrin and discovered reactive oxygen species (ROS) are necessary second messengers. Using an innovative proteomics approach we found that the MAP kinase family member JNK2 is oxidized in FN-f stimulated cells forming a Cys-SOH (sulfenic acid) intermediate. Sulfenic acid formation serves as a major mechanism by which ROS regulate cell signaling but its role in chondrocyte signaling has not been investigated. In his competitive renewal, we propose to determine the mechanism by which sulfenic acid formation regulates JNK2 activity in chondrocytes. We will determine the role of JNK2 activation in OA in vivo by studying the development of surgically-induced OA in JNK2-/- mice. Finally, we will determine if HB-EGF, upregulated and released when chondrocytes are stimulated by FN-f, promotes Rac activity to activate a co-signaling pathway that augments MMP-13 expression and cartilage matrix destruction. These studies will have significant impact on the field by defining key hubs in a signaling network that mediates cartilage matrix destruction. By discovering novel mechanisms by which ROS regulate this signaling network, the information can be used to develop a unique approach to altering redox-regulated catabolic signaling networks in arthritis that targets specific protein modifications. This represents a significant advance over the general inhibition of ROS production which has not proven successful in treating conditions promoted by excessive ROS, including arthritis. PUBLIC HEALTH RELEVANCE: Osteoarthritis is the most common cause of chronic disability in older adults but treatments to slow the progression of the disease are lacking. The results from this project will provide new information about basic mechanisms relevant to cartilage breakdown in osteoarthritis. This information is needed in order to discover new targets and develop new therapies for slowing or stopping the progression of the disease.