Signaling Mechanisms of Focal Adhesion Protein Kindlin-2 in Chondrogenesis

 描述(申请人提供)：整合素信号对软骨形成至关重要，它的改变是骨关节炎等骨骼疾病发展的一个原因。这个项目利用了关于Kindlin-2的令人兴奋的新发现，Kindlin-2是整合素信号的关键调节因子，并试图确定其在控制软骨形成细胞行为中的作用。申请人的研究表明，去除软骨细胞中的Kindlin-2会导致小鼠软骨形成的严重缺陷。此外，Kindlin-2的缺失损害了转化生长因子-β1信号和软骨形成的主要调节因子Sox9的表达。此外，有证据表明，Kindlin-2不仅定位于局灶性粘连(FA)，还定位于软骨细胞的细胞核。基于这些和其他研究，申请人假设Kindlin-2与其细胞质和核结合伙伴协同工作，调节转化生长因子-β1信号和Sox9的表达，从而控制软骨细胞功能和软骨形成。为了测试这一点，申请者提出了以下三个目标。目的1确定Kindlin-2调控软骨细胞Sox9表达的机制。申请者将使用分子、细胞和遗传策略的组合来测试这一假设，即Kindlin-2不仅通过其在FA的相互作用，而且通过其在细胞核中的相互作用来调节Sox9的表达。目的2 S研究Kindlin-2在转化生长因子-β-1激活和信号转导中的作用及机制。申请者将检验这一假设，即Kindlin-2通过与转化生长因子-β1信号通路的关键组成部分相互作用来调节转化生长因子-β1的激活和下游信号。目的3确定Kindlin-2-Sox9信号轴在体内软骨形成中的作用。申请者将使用条件基因敲除和转基因小鼠模型来确定Kindlin-2-Sox9信号轴在体内软骨形成中的功能贡献。这些研究将阐明软骨形成中的三个关键调控元件(整合素信号、转化生长因子-β1信号和Sox9表达)之间的相互作用及其潜在机制，这将显著提高我们对软骨细胞行为的基本机制的理解，并可能导致开发新的策略来缓解常见的骨骼疾病，如骨关节炎。

 DESCRIPTION (provided by applicant): Integrin signaling is critical for chondrogenesis, and its alteration is a causal factor in the development of skeletal diseases such as osteoarthritis. This project takes advantage of exciting new findings on Kindlin-2, a key regulator of integrin signaling, and seeks to define its role in control of chondrogenic cell behavior. Studies by the applicants have shown that ablation of Kindlin-2 in chondrogenic cells results in severe defects in chondrogenesis in mice. Furthermore, loss of Kindlin-2 impairs TGF-β1 signaling and the expression of Sox9, a master regulator of chondrogenesis. Additionally, there is evidence that Kindlin-2 localizes not only to focal adhesions (FAs) but also to the nuclei of chondrocytes. Based on these and other studies, the applicants hypothesize that Kindlin-2 works in concert with its cytoplasmic and nuclear binding partners to regulate TGF-β1 signaling and Sox9 expression and thereby control chondrocyte functions and chondrogenesis. To test this, the applicants propose the following three aims. Aim 1 is to determine the mechanisms by which Kindlin-2 regulates Sox9 expression in chondrocytes. The applicants will employ a combination of molecular, cellular and genetic strategies to test the hypothesis that Kindlin-2 regulates Sox9 expression through not only its interactions at FAs but also its interactions in the nuclei. Aim 2 s to determine the roles and mechanisms of Kindlin-2 in TGF-β1 activation and signaling. The applicants will test the hypothesis that Kindlin-2 regulates TGF-β1 activation and downstream signaling by interacting with key components of the TGF-β1 signaling pathway. Aim 3 is to determine the functions of the Kindlin-2-Sox9 signaling axis in chondrogenesis in vivo. The applicants will employ conditional knockout and transgenic mouse models to define the functional contribution of the Kindlin-2-Sox9 signaling axis to chondrogenesis in vivo. These studies will shed light on the interplay between three key control elements in chondrogenesis (integrin signaling, TGF-β1 signaling and Sox9 expression) and the underlying mechanisms, which will significantly improve our understanding of the fundamental mechanisms governing chondrocyte behavior and may lead to development of novel strategies for alleviating common skeletal diseases such as osteoarthritis.