Functional Structural Biology of Noncollagenous Bone Matrix Proteins

骨是一种复杂的无机-有机复合材料，具有重要的力学和生理意义。尽管是次要成分，非胶原基质蛋白（ncp）发挥调节作用，赋予钙化的有机基质内聚性。虽然转基因小鼠模型和细胞培养研究在了解ncp的整体生物活性及其对骨骼的构建和维持的贡献方面取得了实质性进展，但它们的分子结构如何介导矿物质沉积仍然是争论的主题。目前的许多信息来自于计算机预测和人工试管分析。这种关于蛋白质-矿物质关系的实验和理论研究，虽然信息量极大，但充其量只是对人体复杂生物环境中分子尺度上真正发生的事情的“粗略近似”。因此，有必要在更多与生理相关的条件下验证这些研究的结果。为了实现这一目标，本提案将利用一种综合的“功能结构生物学”方法来理解分子结构、基序和结构域如何定义ncp与矿物相的关系。

Bone is a complex inorganic-organic composite with critical mechanical and physiological implications. Despite being minor components, noncollagenous matrix proteins (NCPs) play regulatory roles and impart cohesion to the calcified organic matrix. While transgenic mouse models and cell culture studies have allowed substantial progress in understanding the overall biological activity of NCPs and their contribution to building and maintaining bone, how their molecular structure mediates mineral deposition is still subject of debate. Much of the current information derives from in silico predictions and artificial test tube assays. While extremely informative, such experimental and theoretical studies on protein­mineral relationships are at best “crude approximations” of what really happens at the molecular scale in the complex biological environment of the body. There is therefore a need to validate results from such studies under more physiologically- relevant conditions. Towards this objective, this proposal will exploit an integrative ‘functional structural biology’ approach to understand how molecular structure, motifs and domains define the relationship of NCPs to the mineral phase. The laboratory has been focusing on a NCP called bone sialoprotein (BSP) because it is associated with initial mineralization events. We have obtained novel data on this NCP that could not have been predicted from current knowledge and that have important functional implications. Our short-term objective is to obtain a comprehensive understanding of the functional domains of the BSP molecule using a combination of basic structural biology approaches, molecular modifications, cell culture and experimental manipulations, which will take into account the physiology of the body and address the limitations of in silico predictions and artificial test tube assays. Taking advantage of the knowledge acquired for BSP, in the longer term we intend to extend our studies to the other bone NCPs in order to obtain a comprehensive understanding of how this family of proteins regulates basic cellular and matrix events during mineral deposition. This research program will provide highly qualified personnel (HQP both students and technical trainees) with a unique training environment, based on molecular and structural biology, only available in few laboratories throughout the world. This training will not only be applicable to bone biology but also to a broad range of fundamental biological questions. It will also provide needed fundamental information on molecular structure-function relationships of a group of proteins that play important roles in the basic biology of bone and hard tissues, in general, thereby contributing to our understanding of a critical tissue in tetrapod biology.