Structural basis and functional consequence of Helicobacter pylori CagA multimerization in cells
Structural basis and functional consequence of Helicobacter pylori CagA multimerization in cells
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DOI：
10.1074/jbc.m606172200
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发表时间：
2006-10-27
影响因子：
4.8
通讯作者：
Hatakeyama, Masanori
中科院分区：
文献类型：
--
作者：
Ren, Shumei;Higashi, Hideaki;Hatakeyama, Masanori
幽门螺杆菌cagA阳性菌株与胃腺癌有关。CagA基因产物CagA被送入胃上皮细胞，定位在质膜上，并在EPIYA重复区域经历酪氨酸磷酸化，该区域包含EPIYA-A片段、EPIYA-B片段和Western CagA特异性EPIYA-C片段或东亚CagA特异性EPIYA-D片段。在宿主细胞中，CagA通过酪氨酸磷酸化的EPIYA-C或EPIYA-D片段与SHP-2磷酸酶特异性结合并解除调控，从而诱导一种被称为蜂鸟表型的细长细胞形状。在这项研究中，我们发现CagA在细胞中以一种不依赖于其酪氨酸磷酸化的方式进行多聚化。利用一系列CagA突变体，我们在EPIYA-C片段以及位于EPIYA-C或EPIYA-D片段下游的序列中鉴定了一个保守的氨基酸序列基序(FPLXRXXXVXDL-SKVG)，它介导了EPIYA-C片段和EPIYA-D片段下游的CagA多聚体。我们还发现，一个多聚体但不能结合SHP-2的磷酸化抗性CagA抑制了野生型CagA-SHP-2复合体的形成，并取消了对蜂鸟表型的诱导。因此，SHP-2通过其两个Src同源2结构域与预先形成的酪氨酸磷酸化的CagA多聚体结合。这些结果反过来表明，CagA多聚化是CagA-SHP-2相互作用和随后SHP-2放松调控的先决条件。目前的工作提出了抑制CagA多聚化取消CagA促进胃癌发生的病理生理活性的可能性。
Helicobacter pylori cagA-positive strains are associated with gastric adenocarcinoma. The cagA gene product CagA is delivered into gastric epithelial cells where it localizes to the plasma membrane and undergoes tyrosine phosphorylation at the EPIYA-repeat region, which contains the EPIYA-A segment, EPIYA-B segment, and Western CagA-specific EPIYA-C or East Asian CagA-specific EPIYA-D segment. In host cells, CagA specifically binds to and deregulates SHP-2 phosphatase via the tyrosine-phosphorylated EPIYA-C or EPIYA-D segment, thereby inducing an elongated cell shape known as the hummingbird phenotype. In this study, we found that CagA multimerizes in cells in a manner independent of its tyrosine phosphorylation. Using a series of CagA mutants, we identified a conserved amino acid sequence motif (FPLXRXXXVXDL-SKVG), which mediates CagA multimerization, within the EPIYA-C segment as well as in a sequence that located immediately downstream of the EPIYA-C or EPIYA-D segment. We also found that a phosphorylation-resistant CagA, which multimerizes but cannot bind SHP-2, inhibits the wild-type CagA-SHP-2 complex formation and abolishes induction of the hummingbird phenotype. Thus, SHP-2 binds to a preformed and tyrosine-phosphorylated CagA multimer via its two Src homology 2 domains. These results, in turn, indicate that CagA multimerization is a prerequisite for CagA-SHP-2 interaction and subsequent deregulation of SHP-2. The present work raises the possibility that inhibition of CagA multimerization abolishes pathophysiological activities of CagA that promote gastric carcinogenesis.