School of Life Sciences, University of Sussex, Brighton, UK
School of Cellular and Molecular Medicine, University of Bristol, UK.
Haematologica. 2019 Jul;104(7):1365-1377. doi: 10.3324/haematol.2018.202846. Epub 2019 Jan 10.
Canonical Wnt/β-catenin signaling is frequently dysregulated in myeloid leukemias and is implicated in leukemogenesis. Nuclear-localized β-catenin is indicative of active Wnt signaling and is frequently observed in acute myeloid leukemia (AML) patients; however, some patients exhibit little or no nuclear β-catenin even where cytosolic β-catenin is abundant. Control of the subcellular localization of β-catenin therefore represents an additional mechanism regulating Wnt signaling in hematopoietic cells. To investigate the factors mediating the nuclear-localization of β-catenin, we carried out the first nuclear/cytoplasmic proteomic analysis of the β-catenin interactome in myeloid leukemia cells and identified putative novel β-catenin interactors. Comparison of interacting factors between Wnt-responsive cells (high nuclear β-catenin) Wnt-unresponsive cells (low nuclear β-catenin) suggested the transcriptional partner, LEF-1, could direct the nuclear-localization of β-catenin. The relative levels of nuclear LEF-1 and β-catenin were tightly correlated in both cell lines and in primary AML blasts. Furthermore, LEF-1 knockdown perturbed β-catenin nuclear-localization and transcriptional activation in Wnt-responsive cells. Conversely, LEF-1 overexpression was able to promote both nuclear-localization and β-catenin-dependent transcriptional responses in previously Wnt-unresponsive cells. This is the first β-catenin interactome study in hematopoietic cells and reveals LEF-1 as a mediator of nuclear β- catenin level in human myeloid leukemia.
经典 Wnt/β-连环蛋白信号通路在髓系白血病中经常失调，并且与白血病的发生有关。核内定位的β-连环蛋白表明 Wnt 信号通路活跃，在急性髓系白血病（AML）患者中经常观察到；然而，一些患者表现出很少或没有核内β-连环蛋白，即使细胞质中β-连环蛋白丰富。因此，β-连环蛋白亚细胞定位的控制代表了调节造血细胞中 Wnt 信号的另一种机制。为了研究介导β-连环蛋白核定位的因素，我们对髓系白血病细胞中的β-连环蛋白相互作用体进行了首次核/细胞质蛋白质组学分析，并鉴定了潜在的新的β-连环蛋白相互作用体。Wnt 反应性细胞（高核β-连环蛋白）与 Wnt 非反应性细胞（低核β-连环蛋白）之间相互作用因子的比较表明，转录伴侣 LEF-1 可以指导β-连环蛋白的核定位。在两种细胞系和原发性 AML 原始细胞中，核 LEF-1 和β-连环蛋白的相对水平紧密相关。此外，LEF-1 敲低扰乱了 Wnt 反应性细胞中β-连环蛋白的核定位和转录激活。相反，LEF-1 过表达能够促进先前 Wnt 非反应性细胞中的核定位和β-连环蛋白依赖性转录反应。这是造血细胞中首次进行的β-连环蛋白相互作用体研究，揭示了 LEF-1 作为人髓系白血病中核β-连环蛋白水平的介导物。
