Characterization ofHelicobacter pylori VacA-containing vacuoles (VCVs), VacA intracellular trafficking and interference with calcium signalling in T lymphocytes

Abstract

The human pathogen Helicobacter pylori colonizes half of the global population. Residing at the stomach epithelium, it contributes to the development of diseases such as gastritis, duodenal and gastric ulcers, and gastric cancer. A major factor is the secreted vacuolating toxin VacA, which forms anion-selective channels in the endosome membrane that cause the compartment to swell, but the composition and purpose of the resulting VacA-containing vacuoles (VCVs) are still unknown. VacA exerts influence on the host immune response in various ways, including inhibition of T-cell activation and proliferation and suppression of the host immune response. In this study, for the first time the composition of VCVs from T cells was comprehensively analysed to investigate VCV function. VCVs were successfully isolated via immunomagnetic separation, and the purified vacuoles were analysed by mass spectrometry. We detected a set of 122 VCV-specific proteins implicated among others in immune response, cell death and cellular signalling processes, all of which VacA is known to influence. One of the individual proteins studied further was stromal interaction molecule (STIM1), a calcium sensor residing in the endoplasmic reticulum (ER) that is important in store-operated calcium entry. Live cell imaging microscopy data demonstrated colocalization of VacA with STIM1 in the ER and indicated that VacA may interfere with the movement of STIM1 towards the plasma membrane-localized calcium release activated calcium channel protein ORAI1 in response to Ca(2+) store depletion. Furthermore, VacA inhibited the increase of cytosolic-free Ca(2+) in the Jurkat E6-1 T-cell line and human CD4(+) T cells. The presence of VacA in the ER and its trafficking to the Golgi apparatus was confirmed in HeLa cells, identifying these two cellular compartments as novel VacA target structures.

Mononuclear-macrophages but not neutrophils act as major infiltrating anti-leptospiral phagocytes during leptospirosis

“…Intracellular free Ca 2+ is a critical factor for activation of phagocytes such as inducing phagocytosis, the respiratory burst, maturation of phagosomes, and secretion of bactericidal substances [71]. Previous studies showed that high [Ca 2+ ]i is involved in killing intracellular Listeria monocytogenes and Helicobacter pylori [71,72]. In the present study, we revealed that the total ROS and NO levels and [Ca 2+ ]i in the L .…”

Pathogenesis of Helicobacter pylori infection

“…A classical feature of VacA activity is its capability to induce vacuoles in host cells. In a recent study, the composition of these vacuoles was analyzed by mass spectrometry . A set of 122 specific proteins implicated in immune responses, cell death, and cell signaling were identified.…”

“…A set of 122 specific proteins implicated in immune responses, cell death, and cell signaling were identified. VacA also interacts with proteins from the endoplasmic reticulum and Golgi, which identified these two compartments as new VacA targets . Another report showed that a stem‐loop structure in the 5′ untranslated region of the vacA transcript is important for vacA transcription and toxin activity .…”

Helicobacter pylori VacA, a distinct toxin exerts diverse functionalities in numerous cells: An overview

“…10 The suppression is resulting into inhibition of activation and proliferation of T cell causing induction of cell cycle arrest. In order to block calcineurin, VacA inhibits calcium influx after preventing ER calcium sensing protein STIM1 to bind with calcium release activated calcium (CRAC) Channel protein, ORAI1.…”

“…This may subsequently lead to the blocking at the level of Ca 2+ calmodulin dependent phosphatase calcineurin 10. It is reported that VacA suppresses nuclear translocation of NFAT thereby causing downregulation of interleukin-2 (IL2) gene transcription.…”