Petrov N S, Popov B V
Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064, Russia.
Biochemistry (Mosc). 2014 Jun;79(6):524-30. doi: 10.1134/S0006297914060054.
The canonical Wnt signal pathway is a key regulator of self-renewal and cell fate determination in various types of stem cells. The total pool of β-catenin consists of two different forms: the signaling form of the protein transmits the Wnt signals from the cell membrane to the target genes, whereas the membrane β-catenin is involved in formation of cell-to-cell contact at cadherin junctions. Earlier we developed an in vitro model of epithelial differentiation of mesenchymal stem cells (MSCs) co-cultured with epithelial A-549 cells. The purpose of the present work was to study the role of Wnt2 secreted by the A-549 cells in paracrine induction of β-catenin in co-cultured MSCs. Using the somatic gene knockdown technique, we obtained A-549 cell cultures with down-regulated WNT2. The MSCs co-cultured with the control A-549 cells displayed an increase in the levels of total cellular and signaling β-catenin and transactivation of a reporter construction containing the Lef/Tcf protein family binding sites. In contrast, β-catenin was not induced in the MSCs co-cultured with the A-549 cells with down-regulated WNT2 expression, but the total protein level was increased. We suggest that Wnt2 secreted by A-549 cells induces in co-cultured MSCs the Wnt/β-catenin signaling pathway, whereas the associated increase in total β-catenin level should be due to another mechanism.
经典Wnt信号通路是各类干细胞自我更新和细胞命运决定的关键调节因子。β-连环蛋白的总量由两种不同形式组成：该蛋白的信号传导形式将Wnt信号从细胞膜传递至靶基因，而膜β-连环蛋白则参与钙黏蛋白连接处细胞间接触的形成。此前我们建立了间充质干细胞（MSC）与上皮A-549细胞共培养的上皮分化体外模型。本研究的目的是探讨A-549细胞分泌的Wnt2在旁分泌诱导共培养的MSC中β-连环蛋白的作用。利用体细胞基因敲低技术，我们获得了WNT2表达下调的A-549细胞培养物。与对照A-549细胞共培养的MSC显示，细胞总β-连环蛋白和信号传导β-连环蛋白水平增加，以及含有Lef/Tcf蛋白家族结合位点的报告基因构建体的反式激活。相反，与WNT2表达下调的A-549细胞共培养的MSC中未诱导出β-连环蛋白，但总蛋白水平增加。我们认为，A-549细胞分泌的Wnt2在共培养的MSC中诱导Wnt/β-连环蛋白信号通路，而总β-连环蛋白水平的相关增加应归因于另一种机制。
