State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
J Biol Chem. 2010 Apr 30;285(18):13397-404. doi: 10.1074/jbc.M109.083246. Epub 2010 Mar 1.
The TAK1-NLK cascade is a mitogen-activated protein kinase-related pathway that plays an inhibitory role in canonical Wnt/beta-catenin signaling through regulating the LEF1/TCF family transcriptional factors. TAB2 (TAK1-binding protein 2) is a putative TAK1 interacting protein that is involved in the regulation of TAK1. Here, we found that TAB2 could directly interact with NLK and function as a scaffold protein to facilitate the interaction between TAK1 and NLK. Knocking down TAB2 using small interfering RNA abolished the interaction of TAK1 with NLK in mammalian cells. The intermediate region (residues 292-417) of TAB2 was mapped for its binding to NLK. TAB2-DeltaM, a TAB2 mutant lacking this region, showed a lower affinity for NLK and became defective in its scaffolding function. In addition, TAB2, but not TAB2-DeltaM, mediated TAK1-dependent activation of NLK and LEF1 polyubiquitylation, resulting in the inhibition of canonical Wnt signaling. Moreover, Wnt3a stimulation led to an increase in the interaction of TAB2 with NLK and the formation of a TAK1.TAB2.NLK complex, suggesting that this TAK1-TAB2-NLK pathway may constitute a negative feedback mechanism for canonical Wnt signaling.
TAK1-NLK 级联是一种丝裂原活化蛋白激酶相关途径，通过调节 LEF1/TCF 家族转录因子，在经典 Wnt/β-连环蛋白信号通路中发挥抑制作用。TAB2（TAK1 结合蛋白 2）是一种假定的 TAK1 相互作用蛋白，参与 TAK1 的调节。在这里，我们发现 TAB2 可以直接与 NLK 相互作用，并作为支架蛋白促进 TAK1 和 NLK 之间的相互作用。使用小干扰 RNA 敲低 TAB2 可消除哺乳动物细胞中 TAK1 与 NLK 的相互作用。TAB2 与 NLK 结合的中间区域（残基 292-417）被定位。缺乏该区域的 TAB2-DeltaM 突变体与 NLK 的亲和力较低，并且其支架功能出现缺陷。此外，TAB2 而非 TAB2-DeltaM 介导 TAK1 依赖性 NLK 和 LEF1 多泛素化的激活，从而抑制经典 Wnt 信号通路。此外，Wnt3a 刺激导致 TAB2 与 NLK 的相互作用增加，并形成 TAK1.TAB2.NLK 复合物，表明该 TAK1-TAB2-NLK 途径可能构成经典 Wnt 信号的负反馈机制。
