Role of proprotein convertases in the regulation of osteoblast functions

大多数脊椎动物都拥有矿化的内部骨骼，这是一种独特的器官，使关节肢体得以进化，并在3亿多年前由四足动物征服大陆。骨骼是在骨化过程中形成和维持的，这意味着一种高度专业化的细胞类型：成骨细胞的作用。这种细胞只存在于脊椎动物中，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专属能力。在过去的20年里，指导成骨细胞形成和活性的遗传程序得到了广泛的研究。然而，成骨细胞分泌细胞外基质蛋白的生化和酶过程仍然知之甚少。因此，在我们的研究计划中，我们建议在成骨细胞中研究原蛋白转换酶的功能，这是一个酶家族，它可以切割数百种其他分泌的蛋白质，激活或灭活它们。这一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，对成骨细胞中原蛋白转换酶的作用研究还很肤浅。为了了解原蛋白转换酶在骨化中所起的作用，我们的实验室利用了应用最广泛的脊椎动物模式生物--小鼠。利用在这种有机体中开发的遗传工具，我们将改造仅在成骨细胞中缺乏特定原蛋白转换酶的改良小鼠。然后，我们将对这些动物的骨骼进行表征，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。这些方法将使我们更好地了解原蛋白转换酶在成骨细胞功能中所起的细胞和生化作用。这项研究计划对于了解成骨细胞中由原蛋白转换酶引起的蛋白质成熟如何控制骨化很重要。它还将在成骨细胞生物学的这一方面产生新的知识，从而为该领域做出重要贡献。

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.