Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749, Korea.
Helicobacter. 2011 Aug;16(4):276-83. doi: 10.1111/j.1523-5378.2011.00851.x.
Infection of cagA-positive Helicobacter pylori is associated with increased expression of MMPs in gastric epithelial cells. The role of phosphorylated CagA in the induction of MMP-9, a protease-degrading basement membrane, in gastric epithelial cells has not been clearly defined yet. The aim of this study is to analyze whether the presence of CagA and its phosphorylation status play a role in increased expression of MMP-9 in gastric epithelial cells.
Induction of MMP-9 secretion was analyzed in gastric epithelial AGS cells harboring CagA with or without EPIYA motif, which is injected by H. pylori or ectopically expressed. In addition, signaling pathways involved in the CagA-dependent MMP-9 production have been studied.
The 147C strain of H. pylori expressing tyrosine-phosphorylated CagA (EPIYA present) induced higher MMP-9 secretion by AGS cells than the 147A strain expressing non-tyrosine-phosphorylated CagA (EPIYA absent). In addition, in bacteria-free CagA-inducible AGS cells, expression of wild-type CagA induced more MMP-9 secretion than phosphorylation-resistant CagA. Inhibition of CagA phosphorylation by the Src family kinase inhibitor PP1 downregulated CagA-mediated MMP-9 secretion. Knockdown of SHP-2 phosphatase dramatically reduced MMP-9 secretion. ERK inhibitors, PD98059 and U0126, and NF-κB pathway inhibitors, sulfasalazine and N-acetyl-l-cysteine, also inhibited MMP-9 expression.
These results support a model whereby the EPIYA motif of CagA is phosphorylated by Src family kinases in gastric epithelial cells, which initiates activation of SHP-2. In addition, they suggest that the resultant activation of ERK pathway along with CagA-dependent NF-κB activation is critical for the induction of MMP-9 secretion.
感染 cagA 阳性幽门螺杆菌与胃上皮细胞中 MMPs 的表达增加有关。磷酸化 CagA 在诱导胃上皮细胞中蛋白酶降解基底膜的 MMP-9 方面的作用尚未明确。本研究旨在分析 CagA 的存在及其磷酸化状态是否在胃上皮细胞中 MMP-9 的表达增加中起作用。
分析了含有 CagA 及其 EPIYA 基序（由 H. pylori 注射或异位表达）的胃上皮细胞 AGS 中 MMP-9 分泌的诱导情况。此外，还研究了参与 CagA 依赖性 MMP-9 产生的信号通路。
表达酪氨酸磷酸化 CagA（存在 EPIYA）的 H. pylori 147C 菌株比表达非酪氨酸磷酸化 CagA（不存在 EPIYA）的 147A 菌株诱导 AGS 细胞产生更高水平的 MMP-9。此外，在无细菌的 CagA 诱导型 AGS 细胞中，野生型 CagA 的表达诱导的 MMP-9 分泌多于磷酸化抗性 CagA。Src 家族激酶抑制剂 PP1 抑制 CagA 磷酸化可下调 CagA 介导的 MMP-9 分泌。SHP-2 磷酸酶的敲低显著降低了 MMP-9 的分泌。ERK 抑制剂 PD98059 和 U0126 以及 NF-κB 通路抑制剂柳氮磺胺吡啶和 N-乙酰-L-半胱氨酸也抑制了 MMP-9 的表达。
这些结果支持了这样一种模型，即 CagA 的 EPIYA 基序在胃上皮细胞中被 Src 家族激酶磷酸化，从而启动 SHP-2 的激活。此外，它们表明 ERK 通路以及 CagA 依赖性 NF-κB 激活的激活对于 MMP-9 分泌的诱导至关重要。
