RESUMEN
BACKGROUND: Helicobacter pylori (Hp) colonizes the human stomach and can induce gastric cancer and mucosa-associated lymphoid tissue (MALT) lymphoma. Clinical observations suggest a role for the Hp virulence factor cytotoxin-associated gene A (CagA) in pathogenesis. The pathogenic activity of CagA is partly regulated by tyrosine phosphorylation of C-terminal Glu-Pro-Ile-Tyr-Ala (EPIYA) motifs in host cells. However, CagA differs considerably in EPIYA motifs, whose functions have been well characterized in epithelial cells. Since CagA is fragmented in immune cells, different CagA variants may exhibit undetected functions in B cells. METHODS: B cells were infected with Hp isolates and isogenic mutants expressing different CagA EPIYA variants. CagA translocation and tyrosine phosphorylation were investigated by Western blotting. Apoptosis was analyzed by flow cytometry and metabolic activity was detected by an MTT assay. RESULTS: Isogenic CagA EPIYA variants are equally well translocated into B cells, followed by tyrosine phosphorylation and cleavage. B cell apoptosis was induced in a CagA-independent manner. However, variants containing at least one EPIYA-C motif affected metabolic activity independently of phosphorylation or multiplication of EPIYA-C motifs. CONCLUSIONS: The diverse structure of CagA regulates B cell physiology, whereas B cell survival is independent of CagA.
Asunto(s)
Infecciones por Helicobacter/metabolismo , Infecciones por Helicobacter/fisiopatología , Helicobacter pylori/genética , Helicobacter pylori/patogenicidad , Linfoma de Células B de la Zona Marginal/metabolismo , Linfoma de Células B de la Zona Marginal/fisiopatología , Neoplasias Gástricas/metabolismo , Neoplasias Gástricas/fisiopatología , Citotoxinas/genética , Citotoxinas/metabolismo , Regulación Bacteriana de la Expresión Génica , Regulación Neoplásica de la Expresión Génica , Variación Genética , Genotipo , Interacciones Huésped-Patógeno/genética , HumanosRESUMEN
Persistent infections with the bacterial group-I carcinogen Helicobacter pylori (H. pylori) have been associated with a broad range of gastric disorders, including gastritis, ulceration, gastric cancer or mucosa-associated lymphoid tissue (MALT) lymphoma. Pathogenesis of H. pylori requires a balance between immune tolerance and defense. Although H. pylori induces inflammatory responses, the immune system cannot eliminate the pathogen. The detailed molecular mechanisms of how H. pylori interferes with cells of the immune system, in particular infiltrated B cells, are not well investigated. Previously, it was shown that the bacterial effector and oncoprotein cytotoxin-associated gene A (CagA) is delivered into B cells followed by its tyrosine-phosphorylation. To investigate the functional consequences in B cells colonized by CagA-positive H. pylori, we analyzed the global transcriptome of H. pylori-infected Mec-1 cells by RNA sequencing. We found 889 differentially expressed genes (DEGs) and validated JUN, FOSL2, HSPA1B, SRC, CXCR3, TLR-4, TNF-α, CXCL8, CCL2, CCL4, MHC class I and MHC class II molecules by qPCR, western blot, flow cytometry and ELISA assays. The H. pylori-specific mRNA expression signature reveals a downregulation of inflammation- and migration-associated genes, whereas central signal transduction regulators of cell survival and death are upregulated.
Asunto(s)
Linfocitos B/inmunología , Linfocitos B/metabolismo , Infecciones por Helicobacter/genética , Infecciones por Helicobacter/microbiología , Helicobacter pylori/fisiología , Interacciones Huésped-Patógeno/genética , Transcriptoma , Biología Computacional/métodos , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Infecciones por Helicobacter/complicaciones , Infecciones por Helicobacter/inmunología , Interacciones Huésped-Patógeno/inmunología , Humanos , Activación de Linfocitos/genética , Activación de Linfocitos/inmunología , Linfoma de Células B de la Zona Marginal/etiología , Reproducibilidad de los Resultados , Neoplasias Gástricas/etiologíaRESUMEN
Helicobacter pylori (H. pylori) has been identified as a leading cause of gastric cancer, which is one of the most frequent and malignant types of tumor. It is characterized by its rapid progression, distant metastases, and resistance to conventional chemotherapy. A number of receptor tyrosine kinases and non-receptor tyrosine kinases have been implicated in H. pylori-mediated pathogenesis and tumorigenesis. In this review, recent findings of deregulated EGFR, c-Met, JAK, FAK, Src, and c-Abl and their functions in H. pylori pathogenesis are summarized.