Abstract：
Wnt/β-catenin signaling plays a crucial role in the migration of mesenchymal stem cells (MSCs). However, our study has revealed an intriguing phenomenon where Dickkopf-1 (DKK1), an inhibitor of Wnt/β-catenin signaling, promotes MSC migration at certain concentrations ranging from 25 to 100 ng/mL while inhibiting Wnt3a-induced MSC migration at a higher concentration (400 ng/mL). Interestingly, DKK1 consistently inhibited Wnt3a-induced phosphorylation of LRP6 at all concentrations. We further identified cytoskeleton-associated protein 4 (CKAP4), another DKK1 receptor, to be localized on the cell membrane of MSCs. Overexpressing the CRD2 deletion mutant of DKK1 (ΔCRD2), which selectively binds to CKAP4, promoted the accumulation of active β-catenin (ABC), the phosphorylation of AKT (Ser473) and the migration of MSCs, suggesting that DKK1 may activate Wnt/β-catenin signaling via the CKAP4/PI3K/AKT cascade. We also investigated the effect of the CKAP4 intracellular domain mutant (CKAP4-P/A) that failed to activate the PI3K/AKT pathway and found that CKAP4-P/A suppressed DKK1 (100 ng/mL)-induced AKT activation, ABC accumulation, and MSC migration. Moreover, CKAP4-P/A significantly weakened the inhibitory effects of DKK1 (400 ng/mL) on Wnt3a-induced MSC migration and Wnt/β-catenin signaling. Based on these findings, we propose that DKK1 may activate the PI3K/AKT pathway via CKAP4 to balance the inhibitory effect on Wnt/β-catenin signaling and thus regulate Wnt3a-induced migration of MSCs. Our study reveals a previously unrecognized role of DKK1 in regulating MSC migration, highlighting the importance of CKAP4 and PI3K/AKT pathways in this process.
摘要：
Wnt/β-catenin信号在间充质干细胞(MSCs)的迁移中起着至关重要的作用。然而,我们的研究揭示了一个有趣的现象，其中DKK1，Wnt/β-catenin信号的抑制剂，在25ng/ml至100ng/ml的某些浓度下促进MSC迁移，同时在较高浓度（400ng/ml）下抑制Wnt3a诱导的MSC迁移。有趣的是,DKK1在所有浓度下一致地抑制Wnt3a诱导的LRP6磷酸化。我们进一步鉴定了CKAP4，另一种DKK1受体，定位于MSCs的细胞膜上。过表达DKK1的CRD2缺失突变体（ΔCRD2），选择性结合CKAP4，促进活性β-连环蛋白（ABC）的积累，AKT（Ser473）的磷酸化和MSCs的迁移，提示DKK1可能通过CKAP4/PI3K/AKT级联激活Wnt/β-catenin信号。我们还研究了未能激活PI3K/AKT途径的CKAP4胞内结构域突变体（CKAP4-P/A）的作用，发现CKAP4-P/A抑制DKK1（100ng/ml）诱导的AKT激活，ABC积累，MSC迁移。此外，CKAP4-P/A显著减弱DKK1(400ng/ml)对Wnt3a诱导的MSC迁移和Wnt/β-catenin信号传导的抑制作用。基于这些发现,我们认为DKK1可能通过CKAP4激活PI3K/AKT通路，以平衡对Wnt/β-catenin信号的抑制作用，从而调节Wnt3a诱导的MSCs迁移。我们的研究揭示了DKK1在调节MSC迁移中的作用，强调CKAP4和PI3K/AKT通路在此过程中的重要性。
