The roles of Wnt-associated deubiquitinases

经典Wnt信号通路促进由β-连环蛋白调节的充分表征的转录程序，称为Wnt/β-连环蛋白信号传导。我们最近发现，Wnt信号传导还通过调节除β-连环蛋白以外的GSK 3靶蛋白的稳定性和活性来促进丰富的翻译后程序，称为Wnt介导的蛋白质稳定化（Wnt/STOP信号传导）。然而，Wnt/STOP如何有助于Wnt生理功能仍然是未被探索的，并形成了这个建议的基础。我鉴定了一组含有Wnt相关激酶GSK 3保守位点并被Wnt/STOP稳定的去泛素化酶（DUB）。对Wnt/STOP靶向DUB之一的探索揭示，它参与抑制Wnt/β-连环蛋白信号传导的反馈回路。进一步的上位性和共定位实验表明，该DUB在β-连环蛋白破坏复合物的水平上起作用。与其作为Wnt/β-连环蛋白信号传导的新型负调节剂的作用一致，DUB候选物通常在Wnt相关肿瘤中突变。通过研究这种DUB的作用，我们的目标是解开Wnt/STOP和Wnt/β-连环蛋白级联之间的意外串扰，这可能在组织更新和肿瘤发生中具有相关意义。因此，我建议i）通过生物化学和细胞生物学分析阐明候选DUB在Wnt/β-连环蛋白和Wnt/STOP信号传导中的作用机制;和ii）使用转基因小鼠和类器官分析其生理作用。

The canonical Wnt signalling pathway promotes well-characterised transcriptional programmes regulated by beta-catenin, referred to as Wnt/beta-catenin signalling. We have recently discovered that Wnt signalling also promotes a rich post-translational programme by regulating the stability and activity of GSK3 target proteins other than beta-catenin, referred to as Wnt-mediated stabilisation of proteins (Wnt/STOP signalling). However, how Wnt/STOP contributes to the Wnt physiological functions remains mostly unexplored, and forms the basis of this proposal. I identified a group of deubiquitinases (DUBs) that contain conserved sites for the Wnt-associated kinase GSK3 and are stabilised by Wnt/STOP. Exploration of one of the Wnt/STOP targeted DUBs revealed that it is involved in a feedback loop to inhibit Wnt/beta-catenin signalling. Further epistasis and co-localisation experiments indicated that this DUB functions at the level of the beta-catenin destruction complex. Consistent with its roles as a novel negative regulator of Wnt/beta-catenin signalling, the DUB candidate is often mutated in Wnt-associated tumours. By investigating the roles of this DUB we aim to unravel an unexpected cross talk between the Wnt/STOP and the Wnt/beta-catenin cascades, which may have relevant implications in tissue renewal and oncogenesis. I therefore propose to i) elucidate the mechanisms of action of the candidate DUB within Wnt/beta-catenin and Wnt/STOP signalling, by biochemical and cell biological analyses; and ii) analyse its physiological roles using transgenic mice and organoids.