Crystallographic Studies of the Wnt Signaling Pathway

描述(申请人的描述)：WNT信号通路扮演着一个 在胚胎发育过程中指导细胞命运的关键作用。此外, WNT信号转导通路的不适当激活在 多种人类癌症，尤其是结肠癌。细胞质蛋白 β-连环蛋白是WNT信号向细胞核传递的中心。在……里面 在没有WNT信号的情况下，β-连环蛋白被一种 蛋白激酶GSK-3β，使β-连环蛋白被一种 泛素连接酶复合体，从而直接在蛋白酶体中降解。在……里面 WNT信号的存在，β-连环蛋白由于抑制而稳定 GSK-3β，使β-连环蛋白与Tcf家族形成复合体 细胞核中的转录因子。在结肠癌中，β-连环蛋白的降解 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复合体 是结构性形成的并激活致癌靶基因，包括myc 和Cyclin DL。 这项提议有两个主要目标。首先是要理解 β-连环蛋白/Tcf相互作用的两种结晶学结构基础 和生化方法，并了解另外两种蛋白质，APC和 钙粘附素，与β-连环素相互作用。这些研究将表明它是否是 有可能设计特定的化合物来破坏β-连环蛋白/Tcf 相互作用，但不包括β-连环蛋白/钙粘附素和β-连环蛋白/APC 互动。这些化合物将有助于开发新的治疗方法 结肠癌。这项提案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-3β，通过对GSK-3β/Axin/β-连环蛋白的结晶学研究 很复杂。为了实现我们的第一个目标，我们明确并下定了决心 β-连环蛋白-β-连环蛋白复合体中犰螂重复序列的结构 Tcf3的β-连环蛋白结合域。他者的结晶 蛋白质-蛋白质复合体正在进行中。

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.