Crystallographic Studies of the Wnt Signaling Pathway

描述（申请人描述）：wnt信号通路在 在胚胎发生过程中指导细胞命运的关键作用。此外，本发明还提供了一种方法， Wnt信号转导通路的不适当激活在 多种人类癌症，特别是结肠癌。胞质蛋白 β-连环蛋白是将WNT信号传递到细胞核的中心。在 在缺乏Wnt信号时，β-连环蛋白被一种 蛋白激酶GSK-3 β，导致β-连环蛋白被 泛素连接酶复合物，因此涉及蛋白体中的降解。在 Wnt信号的存在，β-连环蛋白由于抑制而稳定 GSK-3 β，使β-连环蛋白与Tcf家族形成复合物 核中的转录因子。在结肠癌中，β-连环蛋白降解 被肿瘤抑制基因APC（腺瘤性息肉病）的突变所阻断 coli）和/或β-连环蛋白本身。因此，β-连环蛋白/Tcf复合物 组成型形成并激活致癌靶基因，包括myc 和细胞周期蛋白D1。 这项建议有两个主要目标。第一，了解 β-连环蛋白/Tcf相互作用结构基础 和生物化学方法，并了解其他两种蛋白质，APC和 钙粘蛋白与β-连环蛋白相互作用。这些研究将表明， 有可能设计出可以破坏β-连环蛋白/Tcf的特定化合物， 相互作用，但不是β-连环蛋白/钙粘蛋白和β-连环蛋白/APC 交互.这些化合物将用于开发新的治疗方法， 结肠癌本建议的第二个目标是审查中央 Wnt途径中的调节事件，即β-连环蛋白的磷酸化 GSK-3 β，GSK-3 β/Axin/β-连环蛋白的晶体学研究 复杂.为了实现我们的第一个目标，我们已经明确并确定 β-连环蛋白的犰狳重复区的结构与 Tcf 3的β-连环蛋白结合域。其他结晶 蛋白质-蛋白质复合物正在进行中。

Description (applicant's description): The wnt signaling pathway plays a critical role in directing cell fates during embryogenesis. In addition, inappropriate activation of the wnt signal transduction pathway has a role in a variety of human cancers, in particular colon cancers. The cytoplasmic protein beta-catenin is central to the transmission of wnt signals to the nucleus. In the absence of a wnt signal, beta-catenin is constitutively phosphorylated by a protein kinase GSK-3beta, causing the beta-catenin to be recognized by an ubiquitin ligase complex and thus directed to degradation in proteosomes. In the presence of a wnt signal, beta-catenin is stabilized due to the inhibition of GSK-3beta, allowing the beta-catenin to form a complex with Tcf family transcription factors in the nuclei. In colon cancers, beta-catenin degradation is blocked by mutations of the tumor suppressor gene APC (adenomatous polyposis coli), and/or beta-catenin itself. As a consequence, beta-catenin/Tcf complexes are constitutively formed and activate oncogenic target genes, including myc and cyclin Dl. This proposal has two major objectives. The first is to understand the structural basis of beta-catenin/Tcf interaction using both crystallographic and biochemical approaches, and to understand how two other proteins, APC and cadherin, interact with beta-catenin. These studies will suggest whether it is possible to design specific compounds that can disrupt the beta-catenin/Tcf interaction, but not the beta-catenin/cadherin and beta-catenin/APC interactions. Such compounds will be useful for developing new treatments for colon cancer. The second goal of this proposal is to examine the central regulatory event in the wnt pathway, i.e. the phosphorylation of beta-catenin by GSK-3beta, by crystallographic studies of the GSK-3beta/Axin/beta-catenin complex. To achieve our first objective, we have crystallized and determined the structure of the armadillo repeat region of beta-catenin in complex with the beta-catenin-binding domain of Tcf3. Crystallization of other protein-protein complexes is in progress.