Role of proprotein convertases in the regulation of osteoblast functions

大多数脊椎动物都有一个矿化的内部骨骼，这是一个独特的器官，它使3亿多年前的四足动物得以进化出铰接的四肢，并征服了大陆。骨是通过骨化过程形成和维持的，这涉及到一种高度特化的细胞类型：成骨细胞的作用。这种细胞仅存在于脊椎动物中，具有合成和分泌构成骨细胞外基质的蛋白质并诱导该基质矿化的独特能力。在过去的20年里，人们对指导成骨细胞形成和活性的遗传程序进行了广泛的研究。然而，在成骨细胞分泌细胞外基质蛋白的能力中涉及的生化和酶的过程仍然知之甚少。因此，我们建议在我们的研究计划中研究成骨细胞中蛋白转化酶的功能，这是一个酶家族，可以切断数百种其他分泌蛋白，激活或灭活它们。这个过程也被称为蛋白质成熟。与其他分泌细胞一样，成骨细胞的功能很可能依赖于几种分泌蛋白的成熟，但到目前为止，对成骨细胞中蛋白转化酶的作用的研究还很肤浅。为了了解蛋白转化酶在骨化过程中所起的作用，我们的实验室利用了最广泛使用的脊椎动物模式生物——小鼠。利用在这种生物体中开发的遗传工具，我们将设计出仅在成骨细胞中缺乏特定蛋白转化酶的修饰小鼠。然后，我们将描述这些动物的骨骼特征，以揭示这些酶在骨基质形成和矿化中的作用。我们的实验室还掌握了在细胞培养中研究生物体外成骨细胞功能的技术。这些方法将使我们能够更好地了解蛋白质转化酶在成骨细胞功能中的细胞和生化作用。该研究项目对于理解成骨细胞中蛋白转化酶的蛋白成熟如何控制骨化具有重要意义。它还将产生成骨细胞生物学这方面的新知识，因此对这一领域做出重要贡献。

Most vertebrates possess a mineralized internal skeleton, a unique organ that allowed the evolution of articulated limbs and the conquest of continents by tetrapodes more then 300 millions years ago. Bones are formed and maintained through the process of ossification, which implicates the action of a highly specialized cell type: the osteoblast. This cell, which exists only in bony vertebrates, possesses the exclusive capacity to synthesize and secrete the proteins composing the bone extracellular matrix and to induce the mineralization of this matrix. The genetic program directing the formation and the activity of osteoblasts has been extensively studied over the past 20 years. However, the biochemical and enzymatic processes implicated in the capacity of osteoblasts to secrete extracellular matrix proteins remain poorly understood. Hence, we are proposing in our research program to study in the osteoblast the functions of proprotein convertases, a family of enzymes, which cut hundreds of other secreted proteins, either activating or inactivating them. This process is also called protein maturation. Like other secretory cells, osteoblasts function most likely depends on the maturation of several secreted proteins, yet the role of proprotein convertases in osteoblasts has only been superficially studied so far. To understand the role played by proprotein convertases in ossification, our laboratory takes advantage of the most widely used vertebrate model organism, the mouse. Using genetic tools developed in this organism, we will engineer modified mice lacking specific proprotein convertases only in osteoblasts. We will then characterize the bones of these animals to unravel the role of these enzymes in bone matrix formation and mineralization. Our laboratory also masters techniques to study osteoblast function outside of the organism in cell culture. These approaches will allow us to better appreciate the cellular and biochemical role played by proprotein convertases in osteoblast function. This research program is important to understand how protein maturation by proprotein convertases in osteoblasts controls ossification. It will also generate novel knowledge on this aspect of osteoblast biology and therefore make important contributions to this field.