幽门螺杆菌 CagL 中的 RGD 辅助序列有助于与整合素相互作用和 CagA 的注射。
An RGD helper sequence in CagL of Helicobacter pylori assists in interactions with integrins and injection of CagA.
机构信息
Department of Chemistry, Bielefeld University Bielefeld, Germany.
出版信息
Front Cell Infect Microbiol. 2012 May 23;2:70. doi: 10.3389/fcimb.2012.00070. eCollection 2012.
Helicobacter pylori is a specific gastric pathogen that colonizes the stomach in more than 50% of the world's human population. Infection with this bacterium can induce several types of gastric pathology, ranging from chronic gastritis to peptic ulcers and even adenocarcinoma. Virulent H. pylori isolates encode components of a type IV secretion system (T4SS), which form a pilus for the injection of virulence proteins such as CagA into host target cells. This is accomplished by a specialized adhesin on the pilus surface, the protein CagL, a putative VirB5 ortholog, which binds to host cell β(1) integrin, triggering subsequent delivery of CagA across the host cell membrane. Like the human extracellular matrix protein fibronectin, CagL contains an RGD (Arg-Gly-Asp) motif and is able to trigger intracellular signaling pathways by RGD-dependent binding to integrins. While CagL binding to host cells is mediated primarily by the RGD motif, we identified an auxiliary binding motif for CagL-integrin interaction. Here, we report on a surface exposed FEANE (Phe-Glu-Ala-Asn-Glu) interaction motif in spatial proximity to the RGD sequence, which enhances the interactions of CagL with integrins. It will be referred to as RGD helper sequence (RHS). Competitive cell adhesion assays with recombinant wild type CagL and point mutants, competition experiments with synthetic cyclic and linear peptides, and peptide array experiments revealed amino acids essential for the interaction of the RHS motif with integrins. Infection experiments indicate that the RHS motif plays a role in the early interaction of H. pylori T4SS with integrin, to trigger signaling and to inject CagA into host cells. We thus postulate that CagL is a versatile T4SS surface protein equipped with at least two motifs to promote binding to integrins, thereby causing aberrant signaling within host cells and facilitating translocation of CagA into host cells, thus contributing directly to H. pylori pathogenesis.
幽门螺杆菌是一种特定的胃病原体,在全球超过 50%的人口的胃中定植。这种细菌的感染可诱导多种类型的胃病,从慢性胃炎到消化性溃疡甚至腺癌。毒力幽门螺杆菌分离株编码 IV 型分泌系统(T4SS)的成分,该系统形成用于将毒力蛋白如 CagA 注射到宿主靶细胞中的菌毛。这是通过菌毛表面上的一种特殊粘附素,即假定的 VirB5 同源物 CagL 来完成的,它与宿主细胞的β(1)整合素结合,触发随后的 CagA 穿过宿主细胞膜的输送。与人类细胞外基质蛋白纤连蛋白一样,CagL 含有一个 RGD(精氨酸-甘氨酸-天冬氨酸)基序,并且能够通过与整合素的 RGD 依赖性结合触发细胞内信号通路。虽然 CagL 与宿主细胞的结合主要由 RGD 基序介导,但我们确定了 CagL-整合素相互作用的辅助结合基序。在这里,我们报告了一个在空间上接近 RGD 序列的暴露的 FEANE(苯丙氨酸-谷氨酸-丙氨酸-天冬氨酸-谷氨酸)相互作用基序,该基序增强了 CagL 与整合素的相互作用。它将被称为 RGD 辅助序列(RHS)。用重组野生型 CagL 和点突变体进行竞争细胞粘附测定、用合成的环状和线性肽进行竞争实验以及肽阵列实验揭示了与 RHS 基序与整合素相互作用有关的氨基酸。感染实验表明,RHS 基序在 H. pylori T4SS 与整合素的早期相互作用中起作用,以触发信号转导并将 CagA 注入宿主细胞。因此,我们假设 CagL 是一种多功能的 T4SS 表面蛋白,至少配备了两个基序以促进与整合素的结合,从而导致宿主细胞内异常信号转导,并促进 CagA 进入宿主细胞,从而直接促进 H. pylori 的发病机制。
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