Helicobacter pylori VacA-induced Inhibition of GSK3 through the PI3K/Akt Signaling Pathway
Helicobacter pylori VacA-induced Inhibition of GSK3 through the PI3K/Akt Signaling Pathway
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DOI：
10.1074/jbc.m806981200
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发表时间：
2009-01-16
影响因子：
4.8
通讯作者：
Hirayama, Toshiya
中科院分区：
文献类型：
--
作者：
Nakayama, Masaaki;Hisatsune, Junzo;Hirayama, Toshiya
幽门螺杆菌VacA毒素参与了胃损伤的发病机制和严重程度。我们发现，AZ-521细胞与VacA孵育导致蛋白激酶B（Akt）和糖原合成酶激酶-3 β（GSK 3 β）通过PI 3 K依赖性途径磷酸化。在磷酸化和抑制GSK 3 β后，β-连环蛋白从GSK 3 β/β-连环蛋白复合物中释放，随后发生核转位。甲基-β-环糊精（MCD）和磷脂酰肌醇特异性磷脂酶C（PIPLC），而不是5-硝基-2-（3-苯丙氨基）-苯甲酸（NPPB）和巴弗洛霉素A1，抑制VacA诱导的Akt磷酸化，表明它不需要VacA内化，并且不依赖于空泡化。用TOPtkLuciferase报告质粒或对照FOPtkLucifease报告质粒转染的AZ-521细胞的VacA处理导致TOPtkLuciferase的活化，但不导致FOPtkLucifease的活化。此外，VacA反式激活β-连环蛋白依赖性细胞周期蛋白D1启动子在荧光素酶报告基因测定。用H. vacA突变株感染AZ-521细胞。pylori不能诱导Akt和GSK 3 β的磷酸化，或从GSK 3 β/β-连环蛋白复合物中释放β-连环蛋白。综上所述，这些结果支持以下结论：VacA激活PI 3 K/Akt信号通路，导致GSK 3 β的磷酸化和抑制，以及随后的β-连环蛋白向细胞核的易位，这与VacA对β-连环蛋白调节的转录活性的影响一致。这些数据引入了Wnt依赖性信号传导可能在H.幽门螺杆菌感染，包括胃癌的发展。
Helicobacter pylori VacA toxin contributes to the pathogenesis and severity of gastric injury. We found that incubation of AZ-521 cells with VacA resulted in phosphorylation of protein kinase B (Akt) and glycogen synthase kinase-3 beta (GSK3 beta) through a PI3K-dependent pathway. Following phosphorylation and inhibition of GSK3 beta,beta-catenin was released from a GSK3 beta/beta-catenin complex, with subsequent nuclear translocation. Methyl-beta-cyclodextrin (MCD) and phosphatidylinositol-specific phospholipase C (PIPLC), but not 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) and bafilomycin A1, inhibited VacA-induced phosphorylation of Akt, indicating that it does not require VacA internalization and is independent of vacuolation. VacA treatment of AZ-521 cells transfected with TOPtkLuciferase reporter plasmid or control FOPtkLucifease reporter plasmid resulted in activation of TOPtkLuciferase, but not FOPtkLucifease. In addition, VacA transactivated the beta-catenin-dependent cyclin D1 promoter in a luciferase reporter assay. Infection of AZ-521 cells by a vacA mutant strain of H. pylori failed to induce phosphorylation of Akt and GSK3 beta, or release of beta-catenin from a GSK3 beta/beta-catenin complex. Taken together, these results support the conclusion that VacA activates the PI3K/Akt signaling pathway, resulting in phosphorylation and inhibition of GSK3 beta, and subsequent translocation of beta-catenin to the nucleus, consistent with effects of VacA on beta-catenin-regulated transcriptional activity. These data introduce the possibility that Wnt-dependent signaling might play a role in the pathogenesis of H. pylori infection, including the development of gastric cancer.