Wnt signaling

描述(由申请人提供)：WNT信号因其在调节胚胎发育和肿瘤发生中的作用而闻名。第一个Wnt基因是凭借其诱发小鼠乳腺肿瘤的能力而被鉴定出来的。研究表明，Wnt信号与许多不同类型的肿瘤有关。最典型的Wnt信号通路是典型的Wnt信号通路，它是由典型的Wnts与其受体复合体结合而启动的，该复合体由低密度脂蛋白受体相关蛋白(LRP)5/6和卷曲蛋白(Fz)组成，最终导致-catenin的稳定和基因转录的激活。尽管我们对Wnt信号机制的了解有了显著的进步，但仍然存在显著的差距。这些包括Wnt调节LRP磷酸化的机制、早期的细胞内事件以及Wnt共同受体FZ和下游信号分子DVL参与Wnt/2-catenin信号通路的生化基础。通过筛选人蛋白激酶的siRNA文库，我们鉴定了一组能抑制典型的Wnt信号的磷脂酰肌醇(PtdIns)蛋白激酶siRNA。我们进一步证明了Wnt3a可以诱导哺乳动物细胞中PtdIns(4，5)P2的积聚，这种积聚依赖于FZ和DVL。我们还证明了PtdIns(4，5)P2是WNT3a诱导的正则信号事件所必需的。此外，我们还发现异三聚体G蛋白可能参与了Wnt调控的PtdIns(4，5)P2的形成。此外，我们的初步结果支持PtdIns(4，5)P2调节LRP磷酸化的两种可能机制。综上所述，我们推测Wnt3a可能通过FZ、DVL和G激活PtdIns激酶，刺激PtdIns(4，5)P2的形成，进而刺激LRP5/6的磷酸化，这是一个早期的Wnt信号事件。特别是，在本应用中，我们将：1)研究WNT3a诱导PtdIns(4，5)P2形成的机制。2)研究PtdIns(4，5)P2调节LRP磷酸化的机制。公共卫生相关性：细胞间的交流对于包括人类在内的多细胞生物体的正常功能是必不可少的。这一过程中的问题会导致包括肿瘤形成在内的各种病理情况。这项研究计划是为了了解Wnt蛋白是如何调节细胞功能的，以及该机制中的缺陷如何导致疾病。Wnt蛋白是细胞间交流的关键分子之一。

DESCRIPTION (provided by applicant): Wnt signaling is known for its roles in regulation of embryonic development and in tumorigenesis. The first Wnt gene was identified by virtue of its ability to induce mammary tumors in mice. Studies have now implicated Wnt signaling in many different types of tumors. The best characterized Wnt signaling pathway, the canonical Wnt signaling pathway, is initiated by the binding of canonical Wnts to their receptor complexes consisting of the LDL receptor-related protein (LRP) 5/6 and frizzled (Fz) proteins, which eventually leads to the stabilization of -catenin and activation of gene transcription. Despite remarkable advances in our understanding of Wnt signaling mechanisms, significant gaps still remain. These include the mechanism by which Wnt regulates LRP phosphorylation, an early intracellular event and the biochemical basis for the involvement of Wnt co-receptor Fz and downstream signaling molecule Dishevelled (Dvl) in the Wnt/2-catenin signaling pathway. By screening a siRNA library for human kinases, we identified a group of phosphatidylinositide (PtdIns) kinase siRNAs that could inhibit canonical Wnt signaling. We went on demonstrating that Wnt3a could induce the accumulation of PtdIns (4,5) P2 in mammalian cells, which depends on both Fz and Dvl. We also showed that PtdIns (4,5) P2 is required for Wnt3a-induced canonical signaling events. Moreover, we found that there is possible involvement of heterotrimeric G proteins in Wnt-regulated PtdIns (4,5) P2 formation. Furthermore, we have preliminary results to support the two possible mechanisms by which PtdIns (4,5)P2 may regulate LRP phosphorylation. Putting all of these together, we hypothesize that Wnt3a may, via Fz, Dvl and G, activate PtdIns kinases to stimulate the formation of PtdIns (4,5)P2, which in turn stimulates the phosphorylation of LRP5/6, an early Wnt signaling event. Specially, in this application we will: 1) Investigate the mechanisms by which Wnt3a induces the formation of PtdIns (4,5)P2. 2) Investigate the mechanisms by which PtdIns (4,5)P2 regulates LRP phosphorylation. PUBLIC HEALTH RELEVANCE: Cell-cell communication is essential for normal functions of multi-cellular organisms including human. Problems in this process would lead to various pathological conditions including tumorigenesis. This research proposal is to understand how the Wnt protein, one of the key molecules in cell-cell communication, regulate cellular functions and how the defects in this mechanism would cause diseases.