Center for Stem Cell and Translational Medicine, School of Life Sciences, Anhui University, Hefei, Anhui, 230601, China.
College of Medical Technology, Anhui Medical College, Hefei, Anhui, 230601, China.
J Cell Sci. 2024 May 1;137(9). doi: 10.1242/jcs.261241. Epub 2024 May 16.
Activation of the Wnt-β-catenin signaling pathway by CHIR99021, a specific inhibitor of GSK3β, induces Tcf7l1 protein degradation, which facilitates the maintenance of an undifferentiated state in mouse embryonic stem cells (mESCs); however, the precise mechanism is still unclear. Here, we showed that the overexpression of transducin-β-like protein 1 (Tbl1, also known as Tbl1x) or its family member Tblr1 (also known as Tbl1xr1) can decrease Tcf7l1 protein levels, whereas knockdown of each gene increases Tcf7l1 levels without affecting Tcf7l1 transcription. Interestingly, only Tbl1, and not Tblr1, interacts with Tcf7l1. Mechanistically, Tbl1 translocates from the cytoplasm into the nucleus in association with β-catenin (CTNNB1) after the addition of CHIR99021 and functions as an adaptor to promote ubiquitylation of the Tcf7l1 protein. Functional assays further revealed that enforced expression of Tbl1 is capable of delaying mESC differentiation. In contrast, knockdown of Tbl1 attenuates the effect of CHIR99021 on Tcf7l1 protein stability and mESC self-renewal. Our results provide insight into the regulatory network of the Wnt-β-catenin signaling pathway involved in promoting the maintenance of naïve pluripotency.
Wnt-β-catenin 信号通路的激活由特异性 GSK3β抑制剂 CHIR99021 诱导，导致 Tcf7l1 蛋白降解，从而促进小鼠胚胎干细胞（mESCs）的未分化状态的维持；然而，确切的机制仍不清楚。在这里，我们表明转导素-β 样蛋白 1（Tbl1，也称为 Tbl1x）或其家族成员 Tblr1（也称为 Tbl1xr1）的过表达可以降低 Tcf7l1 蛋白水平，而敲低每个基因都会增加 Tcf7l1 水平，而不影响 Tcf7l1 转录。有趣的是，只有 Tbl1，而不是 Tblr1，与 Tcf7l1 相互作用。在机制上，在用 CHIR99021 处理后，Tbl1 与 β-连环蛋白（CTNNB1）一起从细胞质转位到细胞核，并作为衔接蛋白促进 Tcf7l1 蛋白的泛素化。功能测定进一步表明，强制表达 Tbl1 能够延迟 mESC 分化。相比之下，敲低 Tbl1 会减弱 CHIR99021 对 Tcf7l1 蛋白稳定性和 mESC 自我更新的影响。我们的结果为参与促进原始多能性维持的 Wnt-β-catenin 信号通路的调节网络提供了深入了解。
