Intracellular and Extracellular function of dentin phosphophoryn

描述（由申请人提供）：骨骼和牙齿的适当矿化对人体正常生长发育和肌肉骨骼功能具有重要意义。破坏正常的生物矿化可导致病理性矿化或脱矿过程。理解生物矿化的复杂过程依赖于对矿化组织的有机基质的结构和功能的了解。骨和牙本质有机基质中的酸性磷蛋白被认为是脊椎动物骨和牙齿的成核过程和无机磷酸钙晶体生长的调节剂。成牙细胞是牙本质形成细胞，来源于神经嵴，产生一组独特的表型产物。在牙本质基质中发现的一种这样的蛋白质是牙本质磷酸化蛋白（DPP）。从牙本质中分离出来的DPP具有独特的组成，其中天冬氨酸和丝氨酸残基包含至少75%的氨基酸，其中85-90%的丝氨酸被磷酸化。直到最近，民进党的功能还被认为是结构性的；然而，最近的研究表明，DPP可能在细胞信号传导中具有其他功能。因此，提出的研究是非常重要的，因为它将为DPP的功能及其对细胞功能和生物过程（如牙本质生物矿化）的影响提供重要的机制见解。我们假设DPP对成牙细胞的存活、分化和有机基质的矿化至关重要。为了验证这一假设，我们建议使用分子方法：(a)研究dpp介导的导致细胞增殖和存活激活的粘附信号事件；(b)确定DPP激活Smad1的机制和下游转录反应导致成牙髓细胞终分化；(c)阐明DPP在介导羟基磷灰石成核和生长中的作用。从基质矿化和信号传导角度理解DPP功能的进展在生物矿化领域具有广泛的意义。

DESCRIPTION (provided by applicant): The proper mineralization of bones and teeth has great importance in normal human growth and development and musculoskeletal function. Disruption of normal biomineralization can lead to pathological mineralization or demineralization process. Understanding the complex process of biomineralization relies on knowledge of the structure and function of the organic matrix of mineralized tissues. Acidic phosphoproteins of the organic matrix of bone and dentin have been implicated as regulators of the nucleation process and growth of the inorganic calcium phosphate crystals of bone and teeth in vertebrates. The odontoblasts, which are dentin forming cells are neural crest derived and produce a unique set of phenotypic products. One such protein identified in the dentin matrix is dentin phosphophoryn (DPP). DPP isolated from dentin, has a unique composition with aspartyl and seryl residues comprising at least 75% of the amino acids with 85-90% of the serines being phosphorylated. Until recently, the function of DPP was thought to be structural; however, recent studies have suggested that DPP may have other functions in cell signaling. Therefore, the proposed studies are highly significant as it will provide important mechanistic insights into the function of DPP and its effects on cellular functions and in biological processes such as dentin biomineralization. We hypothesize that DPP is essential for the survival, terminal differentiation of the odontoblasts and in the mineralization of the organic matrix. To test this hypothesis we propose to use molecular approaches to: (a) investigate DPP-mediated adhesive signaling events leading to activation of cell proliferation and survival; (b) identify the mechanism by which DPP activates Smad1 and the downstream transcriptional responses leading to odontoblast terminal differentiation; (c) elucidate the role of DPP in mediating nucleation and growth of hydroxyapatite. Progress in understanding the function of DPP from the perspective of matrix mineralization and signaling has broad ramifications in the field of biomineralization. PUBLIC HEALTH RELEVANCE: During tooth development, the preodontoblasts polarize and elongate as they mature to the secretory form and secrete collagen and a variety of noncollagenous proteins. The major acidic phosphoprotein synthesized by the odontoblasts is "dentin phosphophoryn" DPP. DPP is a highly acidic protein and has been implicated to function as a regulator of mineral deposition during dentin formation. In this proposal we intend to identify the mechanism by which DPP functions in the extracellular matrix as a regulator of mineralization and intracellularly as a cell signaling molecule. DPP mediated signaling can regulate odontoblast proliferation and differentiation. Results from this study should help us define the various functions of DPP, and its potential use in dentin regeneration.