Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
J Cell Biochem. 2013 Jul;114(7):1488-97. doi: 10.1002/jcb.24490.
Wnt-signaling pathway is implicated in pancreatic development and functional regulation of mature beta-cells. Wnt3a/Wnt pathway activation expands islet cell mass in vitro by increasing proliferation and decreasing apoptosis of beta-cells, thereby enhancing its function. However, the signaling pathways that mediate these effects remain unknown. By using a clonal beta-cell line (NIT-1), we examined the role of IRS2/PI3K in the mediation of Wnt3a-stimulated beta-cell growth. Real-time PCR and Western blot were employed to investigate the activity of Wnt/β-catenin and IRS2/PI3K signaling. Proliferation of NIT-1 cells was assessed by BrdU incorporation, and apoptosis was quantitatively determined by TUNEL and flow cytometry (FCM). Dkk1, an inhibitor of Wnt signaling, and wortmannin, an inhibitor of PI3K, were also used. Results showed that Wnt3a rapidly activated Wnt/β-catenin signaling, promoted IRS2 expression and Akt phosphorylation in NIT-1 cells. These effects were completely abrogated by Dkk1 or partially eliminated by wortmannin. Wnt3a also promoted NIT-1 cell proliferation, inhibited cytokine-induced beta-cell apoptosis, and increased insulin secretion. Both of these effects were also eliminated by Dkk1 or wortmannin. Our results demonstrated that Wnt3a regulates proliferation, apoptosis and enhances function of pancreatic NIT-1 beta cells via activation of Wnt/β-catenin signaling, involving crosstalk with IRS2/PI3K signaling, with the effect of Wnt signaling on beta-cells also being IRS2/PI3K/AKT dependent.
Wnt 信号通路参与胰腺发育和成熟β细胞的功能调节。Wnt3a/Wnt 通路激活可通过增加β细胞的增殖和减少凋亡来扩大胰岛细胞的质量，从而增强其功能。然而，介导这些效应的信号通路仍不清楚。我们使用克隆β细胞系（NIT-1），研究了 IRS2/PI3K 在介导 Wnt3a 刺激的β细胞生长中的作用。实时 PCR 和 Western blot 用于研究 Wnt/β-catenin 和 IRS2/PI3K 信号的活性。通过 BrdU 掺入评估 NIT-1 细胞的增殖，通过 TUNEL 和流式细胞术（FCM）定量测定细胞凋亡。还使用了 Dkk1（Wnt 信号抑制剂）和 wortmannin（PI3K 抑制剂）。结果表明，Wnt3a 可快速激活 Wnt/β-catenin 信号通路，促进 NIT-1 细胞中 IRS2 的表达和 Akt 的磷酸化。这些作用被 Dkk1 完全阻断或被 wortmannin 部分消除。Wnt3a 还促进 NIT-1 细胞增殖，抑制细胞因子诱导的β细胞凋亡，并增加胰岛素分泌。这两种作用也被 Dkk1 或 wortmannin 消除。我们的结果表明，Wnt3a 通过激活 Wnt/β-catenin 信号通路调节胰腺 NIT-1β细胞的增殖、凋亡和增强功能，涉及 IRS2/PI3K 信号的串扰，Wnt 信号对β细胞的作用也依赖于 IRS2/PI3K/AKT。
