Signaling Mechanisms of Focal Adhesion Protein Kindlin-2 in Chondrogenesis

 描述（由申请人提供）：整合素信号传导对于软骨形成至关重要，其改变是骨关节炎等骨骼疾病发展的因果因素。该项目利用了Kindlin-2的令人兴奋的新发现，Kindlin-2是整合素信号传导的关键调节因子，并试图确定其在控制软骨细胞行为中的作用。申请人的研究已经表明，软骨形成细胞中Kindlin-2的消融导致小鼠中软骨形成的严重缺陷。此外，Kindlin-2的缺失损害了TGF-β1信号传导和Sox 9的表达，Sox 9是软骨形成的主要调节因子。此外，有证据表明Kindlin-2不仅定位于粘着斑（FA），而且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与其细胞质和细胞核结合配偶体协同工作以调节TGF-β1信号传导和Sox 9表达，从而控制软骨细胞功能和软骨形成。为了验证这一点，申请人提出了以下三个目标。目的1探讨Kindlin-2对软骨细胞Sox 9表达的调控机制。申请人将采用分子、细胞和遗传策略的组合来检验Kindlin-2不仅通过其在FA处的相互作用而且通过其在细胞核中的相互作用来调节Sox 9表达的假设。目的探讨Kindlin-2在转化生长因子β 1（TGF-β1）活化和信号转导中的作用及其机制.申请人将检验Kindlin-2通过与TGF-β1信号传导途径的关键组分相互作用调节TGF-β1活化和下游信号传导的假设。目的3：研究Kindlin-2-Sox 9信号轴在软骨形成中的作用。申请人将采用条件性敲除和转基因小鼠模型来确定Kindlin-2-Sox 9信号传导轴对体内软骨形成的功能贡献。这些研究将阐明软骨形成中三个关键控制元件（整合素信号传导、TGF-β1信号传导和Sox 9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基本机制的理解，并可能导致开发缓解常见骨骼疾病（如骨关节炎）的新策略。

 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.