Structural and functional characterization of the receptor protein tyrosine phosp

描述(申请人提供)：最近，受体蛋白酪氨酸磷酸酶(RPTP？)已被确认与骨形成有关。RPRP？在原代成骨细胞分化的第5天至第25天，诱导作用较强，比已知的成骨细胞终末分化时诱导的基因如Bgap、IBSP、Dmp1、Akp2和PHEX更强。RPTP以前主要在神经细胞中被描述，并且是第一个被描述为肝素结合分子多营养素(PTN)的受体，PTN是一种15-17 kDa的小趋化因子，也被独立地鉴定为成骨细胞刺激因子-1(OSF-1)。基因工程过表达PTN的小鼠显示出膜内骨形成的显着增加和对长期骨生长的多重影响。PTN发挥刺激作用的分子机制尚不清楚。目前的一个假说是，PTN诱导的RPTP二聚化导致细胞内RPTP的丢失。磷酸酶活性。在没有PTN信号的情况下，RPTP？被证明能使连环蛋白去磷酸化，形成一个连环蛋白/α-连环蛋白/E-钙粘连蛋白分子复合体，将肌动蛋白细丝连接到细胞膜上。这对于正常的细胞间黏附是必要的。PTN信号通过RPTP受体导致连环蛋白/E-钙粘蛋白复合体形成的衰退，这是由于连环蛋白酪氨酸去磷酸化的丧失，肌动蛋白细胞骨架的破坏和细胞间黏附的丧失。我们的目标是对整个系统进行体外研究，包括多营养素、RPTP？和RPTP？？磷酸酶结构域底物。这些研究将对理解这个信号网络中蛋白质之间的分子相互作用具有很高的相关性。此外，更重要的是，对这一新发现的信号系统的生物物理表征和三维结构的了解将开辟一个新的领域，并导致未来基于结构的新型PTN/RPTP的药物设计。小分子结合剂，可能能够治疗骨关节炎、骨量减少/骨质疏松症以及其他与骨密度变化相关的疾病。 公共卫生相关性：受体蛋白酪氨酸磷酸酶(RPTP)是一种关键的跨膜蛋白，调节正常细胞功能的不同方面。我们计划利用各种生物物理技术，研究这种蛋白质与其已知的配体多营养素以及其他已知与RPTP相互作用的蛋白质之间的相互作用。

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.