Role of the first secreted tyrosine kinase in bone development, homeostasis, and repair.

 描述(申请人提供)：细胞外基质(ECM)是分泌骨骼发育-转录控制的高度动态成分。虽然对骨骼发育过程中细胞外基质成分的转录控制进行了深入的研究，但对细胞外基质及其调节因子的后期成分了解相对较少。我们已经确定了一类新的分泌型蛋白调节器，这是第一个已知的分泌型蛋白酪氨酸激酶(VLK)，它对正常的软骨内骨形成是必不可少的。我们发现，VLK磷酸化了广泛的分泌蛋白，在骨骼发育和骨量维持中起着既定的作用。VLK还可以磷酸化驻留的ER蛋白，使其在骨ECM分泌中发挥特殊作用，从而不仅可以直接修改分泌的蛋白质，还可以通过控制分泌过程间接地调节软骨内成骨和骨折内软骨细胞的磷酸化。在这个提案中，我们计划建立VLK-Repair的功能角色。我们将使用体外和体内相结合的方法来确定软骨内细胞中VLK的底物，在体内确定VLK介导的磷酸化的空间和时间模式，建立VLK如何改变软骨细胞分化和软骨内成骨，并检测特定分泌底物的VLK磷酸化的功能。这些研究将为骨细胞外基质功能的调节提供新的机制，为骨发育、内环境平衡和修复的治疗调节提供新的途径。

 DESCRIPTION (provided by applicant): The extracellular matrix (ECM) is a highly dynamic component of the developing -transcriptional control of the secreted skeleton. While the transcriptional control of ECM composition during skeletal development is intensively studied, the post-- components of the ECM and its regulators are relatively poorly understood. We have identified a novel class of regulator of secreted proteins, the first known secreted protein tyrosine kinase (VLK) that is essential for normal endochondral bone formation. We find that VLK phosphorylates a wide range of secreted proteins with established roles in skeletal development and maintenance of bone mass. VLK also phosphorylates resident ER proteins with specific roles in bone ECM secretion, and thus may modify secreted proteins not only directly, but also indirectly through control of the secretion process in -mediated phosphorylations both during endochondral ossification and during fracture endochondral cells. In this proposal, we plan to establish the functional role of VLK- repair. We will use a combination of in vitro and in vivo approaches to identify substrates for VLK in endochondral cells, identify spatial and temporal patterns of VLK mediated phosphorylations in vivo, establish how VLK modifies chondrocyte differentiation and endochondral ossification, and examine the function of VLK phosphorylation of specific secreted substrates. These studies will define a new mechanism for the regulation of ECM function in bone, providing a new approach to the therapeutic modulation of skeletal development, homeostasis, and repair.