Structural and functional characterization of the receptor protein tyrosine phosp

描述（由申请人提供）：最近，受体蛋白酪氨酸磷酸酶（RPTP）已被确定参与骨形成。RPRP害怕吗?在初代成骨细胞分化的第5天至第25天，诱导作用强烈，比其他已知的诱导终代成骨细胞分化的基因如Bglap、Ibsp、Dmp1、Akp2和PheX的诱导作用更强。RPTP害怕吗?？肝素结合分子多营养因子（PTN）是一种15- 17 kDa的小趋化因子，也被独立鉴定为成骨细胞刺激因子-1 （OSF- 1）。PTN过表达的小鼠显示出膜内骨形成的显著增加和对长期骨生长的多重影响。PTN发挥其刺激作用的分子机制尚不清楚。目前的一种假设是，ptn诱导了RPTP的二聚化。？导致细胞内RPTP丢失磷酸酶活性。在没有PTN信号的情况下，RPTP¿？？？可以使-连环蛋白去磷酸化，形成-连环蛋白/a-连环蛋白/ e -钙粘蛋白分子复合物，将肌动蛋白丝系在细胞膜上。这是正常细胞-细胞粘附所必需的。通过RPTP发送PTN信号？？？受体导致catenin/ e -钙粘蛋白复合物形成的衰减，这是由于酪氨酸-catenin去磷酸化的丧失、肌动蛋白细胞骨架的破坏和细胞-细胞粘附的丧失。我们的目标是对由多营养蛋白、RPTP组成的整个系统进行体外研究。和RPTP还有吗? ?phosphatase-domain基质。这些研究将对理解该信号网络中蛋白质之间的分子相互作用具有重要意义。此外，更重要的是，这一新发现的信号系统的生物物理表征和三维结构理解将开辟一个新的领域，并导致未来新的PTN/RPTP基于结构的药物设计。小分子结合剂可能能够治疗骨关节炎、骨质减少/骨质疏松症和其他与骨密度变化相关的疾病。

DESCRIPTION (provided by applicant): Recently, the receptor proteine tyrosine phosphatase (RPTP¿?) has been identified as involved in bone formation. RPRP¿? was strongly induced between day 5 and 25 of primary osteoblast differentiation, more so than other genes known to be induced upon terminal osteoblast differentiation such as Bglap, Ibsp, Dmp1, Akp2 and PheX. RPTP¿? ?has previously been described mainly in neuronal cells, and was the first described receptor for the heparin-binding molecule pleiotrophin (PTN), a small chemokine of 15- 17 kDa, that was also independently identified as Osteoblast-stimulating factor-1 (OSF- 1). Mice engineered to over-express PTN show a marked increase in intramembraneous bone formation and multiple effects on long-term bone growth. The molecular mechanism with which PTN exerts its stimulatory effects is not known in detail. A current hypothesis is that PTN-induced dimerization of RPTP¿?? ?results in loss of intracellular RPTP¿?? phosphatase activity. In the absence of PTN signaling, RPTP¿?? ?is shown to dephosphorylate ¿-catenin, resulting in the formation of a ¿-catenin/a-catenin/E-cadherin molecular complex, which tethers actin filaments to the cell membrane. This is necessary for normal cell-cell adhesion. PTN signaling though the RPTP¿?? ?receptor leads to decay of ¿catenin/E-cadherin complex formation, due to loss of tyrosine dephosphorylation of ¿-catenin, disruption of the actin cytoskeleton and loss of cell-cell adhesion. Our aims are to perform in vitro studies of the entire system consisting of pleiotrophin, RPTP¿??? and RPTP¿?? phosphatase-domain substrates. These studies will be highly relevant for understanding the molecular interactions between the proteins in this signaling network. Also, more importantly, biophysical characterization and three dimensional structural understanding of this newly discovered signaling system will open up a new field and lead to future structure-based drug design of new PTN/RPTP¿??? small-molecule binding agents that might be able to treat osteoarthritis, osteopenia/osteoporosis, and other diseases associated with changes in bone density. PUBLIC HEALTH RELEVANCE: The receptor protein tyrosine phosphatase ¿?? ?(RPTP¿? ) is a key transmembrane protein that regulates different aspects of normal cell function. We plan to study the interactions between this protein and its known ligand pleiotrophin plus other proteins know to interact with RPTP¿?, using a variety of biophysical techniques.