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Brindle A, Bainbridge C, Kumar MR, Todryk S, Padget K. The Bisdioxopiperazine ICRF-193 Attenuates LPS-induced IL-1β Secretion by Macrophages. Inflammation 2024; 47:84-98. [PMID: 37656316 PMCID: PMC10798930 DOI: 10.1007/s10753-023-01895-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 07/25/2023] [Accepted: 08/18/2023] [Indexed: 09/02/2023]
Abstract
Inhibiting pathological secretion of Interleukin-1β has shown beneficial effects in disease models and in the clinic and thus there is interest in finding inhibitors that can reduce its release from macrophages in response to their activation by foreign pathogens. We used an in vitro human macrophage model to investigate whether ICRF-193, a Topoisomerase II inhibitor could modulate IL1B mRNA expression and IL-1β secretion. These macrophage-like cells readily secrete IL-1β in response to Lipopolysaccharide (LPS). Upon exposure to a non-toxic dose of ICRF-193, IL-1β secretion was diminished by ~ 40%; however, level of transcription of IL1B was unaffected. We show that there was no Topoisomerase 2B (TOP2B) binding to several IL1B gene sites, which may explain why ICRF-193 does not alter IL1B mRNA levels. Hence, we show for the first time that ICRF-193 can reduce IL-1β secretion. Its low cost and the development of water-soluble prodrugs of ICRF-193 warrants its further investigation in the modulation of pathological secretion of this cytokine for the treatment of inflammatory disorders. (165 words).
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Affiliation(s)
- Ashleigh Brindle
- Faculty of Health and Life Sciences, Northumbria University at Newcastle, Newcastle Upon Tyne, NE1 8ST, UK
| | - Callum Bainbridge
- Faculty of Health and Life Sciences, Northumbria University at Newcastle, Newcastle Upon Tyne, NE1 8ST, UK
| | - Muganti R Kumar
- Faculty of Health and Life Sciences, Northumbria University at Newcastle, Newcastle Upon Tyne, NE1 8ST, UK
| | - Stephen Todryk
- Faculty of Health and Life Sciences, Northumbria University at Newcastle, Newcastle Upon Tyne, NE1 8ST, UK.
| | - Kay Padget
- Faculty of Health and Life Sciences, Northumbria University at Newcastle, Newcastle Upon Tyne, NE1 8ST, UK
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2
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Wang L, Yi J, Yin XY, Hou JX, Chen J, Xie B, Chen G, Wang QF, Wang LN, Wang XY, Sun J, Huo LM, Che TJ, Wei HL. Vacuolating Cytotoxin A Triggers Mitophagy in Helicobacter pylori-Infected Human Gastric Epithelium Cells. Front Oncol 2022; 12:881829. [PMID: 35912184 PMCID: PMC9329568 DOI: 10.3389/fonc.2022.881829] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 06/20/2022] [Indexed: 11/30/2022] Open
Abstract
Helicobacter pylori (H. pylori)-derived vacuolating cytotoxin A (VacA) causes damage to various organelles, including mitochondria, and induces autophagy and cell death. However, it is unknown whether VacA-induced mitochondrial damage can develop into mitophagy. In this study, we found that H. pylori, H. pylori culture filtrate (HPCF), and VacA could activate autophagy in a gastric epithelial cell line (GES-1). VacA-caused mitochondrial depolarization retards the import of PINK1 into the damaged mitochondria and evokes mitophagy. And, among mass spectrometry (LC-MS/MS) identified 25 mitochondrial proteins bound with VacA, Tom20, Tom40, and Tom70, TOM complexes responsible for PINK1 import, were further identified as having the ability to bind VacA in vitro using pull-down assay, co-immunoprecipitation, and protein–protein docking. Additionally, we found that the cell membrane protein STOM and the mitochondrial inner membrane protein PGAM5 also interacted with VacA. These findings suggest that VacA captured by STOM forms endosomes to enter cells and target mitochondria. Then, VacA is transported into the mitochondrial membrane space through the TOM complexes, and PGAM5 aids in inserting VacA into the inner mitochondrial membrane to destroy the membrane potential, which promotes PINK1 accumulation and Parkin recruitment to induce mitophagy. This study helps us understand VacA entering mitochondria to induce the mitophagy process.
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Affiliation(s)
- Li Wang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Juan Yi
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Xiao-Yang Yin
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Jin-Xia Hou
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Jing Chen
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Bei Xie
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Gang Chen
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Qun-Feng Wang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Li-Na Wang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Xiao-Yuan Wang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Jing Sun
- Geriatrics Department, The Second Hospital of Lanzhou University, Lanzhou, China
| | - Lei-Ming Huo
- Neurosurgery Department, The First Hospital of Lanzhou University, Lanzhou, China
| | - Tuan-Jie Che
- Key Laboratory of Functional Genomics and Molecular Diagnosis of Gansu Province, Lanzhou Baiyuan Gene Technology Co., Ltd, Lanzhou, China
- *Correspondence: Tuan-Jie Che, ; Hu-Lai Wei,
| | - Hu-Lai Wei
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
- Key Laboratory of Functional Genomics and Molecular Diagnosis of Gansu Province, Lanzhou Baiyuan Gene Technology Co., Ltd, Lanzhou, China
- *Correspondence: Tuan-Jie Che, ; Hu-Lai Wei,
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Protein Tyrosine Phosphatase Receptor Type Z in Central Nervous System Disease. Int J Mol Sci 2022; 23:ijms23084414. [PMID: 35457233 PMCID: PMC9024684 DOI: 10.3390/ijms23084414] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 04/12/2022] [Accepted: 04/14/2022] [Indexed: 01/06/2023] Open
Abstract
Gliomas are among the most common tumors of the central nervous system and include highly malignant subtypes, such as glioblastoma, which are associated with poor prognosis. Effective treatments are therefore urgently needed. Despite the recent advances in neuroimaging technologies, differentiating gliomas from other brain diseases such as multiple sclerosis remains challenging in some patients, and often requires invasive brain biopsy. Protein tyrosine phosphatase receptor type Z (PTPRZ) is a heavily glycosylated membrane protein that is highly expressed in the central nervous system. Several reports analyzing mouse tumor models suggest that PTPRZ may have potential as a therapeutic target for gliomas. A soluble cleaved form of PTPRZ (sPTPRZ) in the cerebrospinal fluid is markedly upregulated in glioma patients, making it another promising diagnostic biomarker. Intriguingly, PTPRZ is also involved in the process of remyelination in multiple sclerosis. Indeed, lowered PTPRZ glycosylation by deletion of the glycosyltransferase gene leads to reduced astrogliosis and enhanced remyelination in mouse models of demyelination. Here, we review the expression, molecular structure, and biological roles of PTPRZ. We also discuss glioma and demyelinating diseases, as well as the pathological role of PTPRZ and its application as a diagnostic marker and therapeutic target.
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Zhang Y, Dong Q, Tian L, Zhang S, Zuo N, Zhang S, Ding Z. Risk factors for recurrence of Helicobacter pylori infection after successful eradication in Chinese children: A prospective, nested case-control study. Helicobacter 2020; 25:e12749. [PMID: 32770644 DOI: 10.1111/hel.12749] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 06/24/2020] [Accepted: 07/13/2020] [Indexed: 01/10/2023]
Abstract
BACKGROUND Limited research has been published on the recurrence of Helicobacter pylori infection and risk factors in Chinese children. Our study aimed to identify risk factors for Helicobacter pylori infection recurrence after successful eradication in children. MATERIALS AND METHODS A prospective, nested case-control study was performed. A cohort of 230 children with successful eradication of Helicobacter pylori in Baoding (China) was selected from January 2018 to February 2019. A standardized questionnaire was used to obtain socioeconomic details. Eradication regimens and Helicobacter pylori antibiotic susceptibility testing results were also recorded. Interleukin-1β level, interferon-γ level, and genetic susceptibility (IFNGR1 and PTPRZ1 gene polymorphisms) were analyzed. All children were followed for 1 year. RESULTS Among 218 (94.8%) children who were successfully followed, 41 children (18.8%) had a Helicobacter pylori infection recurrence. The recurrence rate was higher in children ≤10 years old than >10 years old (22.8% vs 7.1%, P = .01). There was no significant difference between the recurrence group and the non-recurrence group in terms of types of therapy and antibiotic sensitivity (P > .05). Multivariable regression results indicated that residence in urban areas, higher household income, and having lunch at home were significantly protective against recurrence (OR 0.155, 0.408, and 0.351 respectively), whereas Helicobacter pylori infection in family members increased the risk of recurrence (OR 2.283). The levels of IL-1β and IFN-γ exhibited no significant difference between the recurrence group and the non-recurrence group. The allele frequency of G in the IFNGR1-56 site, A in the IFNGR1-600 site, and T in the IFNGR1-565 site was significantly higher in the recurrence group when compared to the non-recurrence group (P < .05). CONCLUSIONS The Helicobacter pylori infection recurrence rate is high in children in Baoding region and is closely correlated to socioeconomic factors. The IFNGR1 gene polymorphism may be an independent risk factor for Helicobacter pylori infection recurrence.
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Affiliation(s)
- Yuanda Zhang
- Department of Gastroenterology, Baoding Key Laboratory of Clinical Study on Respiratory and Digestive Diseases in Children, Baoding Children's Hospital, Baoding, China
| | - Qingwei Dong
- Department of Gastroenterology, Baoding Key Laboratory of Clinical Study on Respiratory and Digestive Diseases in Children, Baoding Children's Hospital, Baoding, China
| | - Lei Tian
- Department of Gastroenterology, Baoding Key Laboratory of Clinical Study on Respiratory and Digestive Diseases in Children, Baoding Children's Hospital, Baoding, China
| | - Shaohui Zhang
- Department of Gastroenterology, Baoding Key Laboratory of Clinical Study on Respiratory and Digestive Diseases in Children, Baoding Children's Hospital, Baoding, China
| | - Naying Zuo
- Department of Gastroenterology, Baoding Key Laboratory of Clinical Study on Respiratory and Digestive Diseases in Children, Baoding Children's Hospital, Baoding, China
| | - Sisi Zhang
- Department of Gastroenterology, Baoding Key Laboratory of Clinical Study on Respiratory and Digestive Diseases in Children, Baoding Children's Hospital, Baoding, China
| | - Zhaolu Ding
- Department of Pediatrics, Beijing United Family Hospital, Beijing, China
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5
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Use of in vitro bone models to screen for altered bone metabolism, osteopathies, and fracture healing: challenges of complex models. Arch Toxicol 2020; 94:3937-3958. [PMID: 32910238 PMCID: PMC7655582 DOI: 10.1007/s00204-020-02906-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 09/03/2020] [Indexed: 02/06/2023]
Abstract
Approx. every third hospitalized patient in Europe suffers from musculoskeletal injuries or diseases. Up to 20% of these patients need costly surgical revisions after delayed or impaired fracture healing. Reasons for this are the severity of the trauma, individual factors, e.g, the patients’ age, individual lifestyle, chronic diseases, medication, and, over 70 diseases that negatively affect the bone quality. To investigate the various disease constellations and/or develop new treatment strategies, many in vivo, ex vivo, and in vitro models can be applied. Analyzing these various models more closely, it is obvious that many of them have limits and/or restrictions. Undoubtedly, in vivo models most completely represent the biological situation. Besides possible species-specific differences, ethical concerns may question the use of in vivo models especially for large screening approaches. Challenging whether ex vivo or in vitro bone models can be used as an adequate replacement for such screenings, we here summarize the advantages and challenges of frequently used ex vivo and in vitro bone models to study disturbed bone metabolism and fracture healing. Using own examples, we discuss the common challenge of cell-specific normalization of data obtained from more complex in vitro models as one example of the analytical limits which lower the full potential of these complex model systems.
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6
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Abuderman AWA, Syed R, Mateen A, Malik A, Ola MS. Epidemiological characterization, genetic alterations of Helicobacter pylori infection in chronic gastric disorder and prognostic values of heterozygosity loss in chromosome 3p. Mol Biol Rep 2019; 46:4323-4332. [PMID: 31250359 DOI: 10.1007/s11033-019-04886-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Accepted: 05/15/2019] [Indexed: 11/30/2022]
Abstract
From the literature review, there seem to be no studies conducted on infection caused by Helicobacter pylori in patients with gastric MALT lymphoma in the KSA region. The present research is an attempt to understand the prevalence of patients infected with H. pylori in the selected region and the role of allelic imbalance of chromosome 3p regions to understand the clinical manifestations and features associated with MALT lymphomagenesis. The researcher analyzed the frequency of infection in patients from the region of Saudi Arabia by examining the data collected from hospitals and biopsy tissue samples as per the recommended protocol. The endoscopic diagnosis was performed to collect biopsy samples. Histology and AP-PCR DNA fingerprinting analyses were performed from the endoscopic gastric mucosal biopsies collected from patients with associated gastric MALT lymphoma. The existence of H. pylori was examined based on the results of gastric mucosal biopsies stained with hematoxylin-eosin (H&E) and Steiner's silver stains. MALT, MALT lymphoma tissue samples and H. pylori-positive chronic gastritis were examined for LOH at chromosome 3p24 using standard procedures and techniques. The findings of the paper revealed the H. pylori was found to be positive in 17% of the cases significantly high among the age group of 31-50 years. Patients with MALT, MALT lymphoma, and H. pylori-associated gastritis presented features such as lymphocyte accumulation, vacuolation, Peyer's patch appearance, and lymphatic follicles. H. pylori were found to appear as a dense colored accumulated mass in the gastric epithelial layer. The findings from AP-PCR generated DNA fingerprints revealed intense band including two prominent bands in MALT lymphoma. Among other loci, 3p24 was the only one locus that showed high percentages of LOH as reported earlier in all cancer-related cases. The findings of this research paper empower the fact that allelic imbalances play a vital role in the development of MALT lymphoma. However, future researches should be conducted to identify the chromosome regions of the AP-PCR generated DNA fingerprints of human gastric MALT lymphoma in order to confirm this proposition.
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Affiliation(s)
- Abdul Wahab Ali Abuderman
- Department of Basic Medical Science, College of Medicine, Prince Sattam Bin Abdulaziz University, Al-Kharj, Saudi Arabia
| | - Rabbani Syed
- Department of Pharmaceutics, College of Pharmacy, King Saud University, PO Box 2457, Riyadh, 11451, Saudi Arabia.
| | - Ayesha Mateen
- Department of Clinical Laboratory Science, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Abdul Malik
- Department of Clinical Laboratory Science, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Mohammad Shamsul Ola
- Department of Biochemistry, College of Science, King Saud University, PO Box 2455, Riyadh, Saudi Arabia
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7
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Stepchenko AG, Lyanova BM, Krylova ID, Ilyin YV, Georgieva SG, Pankratova EV. Differentiation of Monocytic Cells Is Accompanied by a Change in the Expression of the Set of Oct-1 Isoforms. DOKL BIOCHEM BIOPHYS 2019; 483:306-308. [PMID: 30607726 DOI: 10.1134/s1607672918060066] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Indexed: 11/22/2022]
Abstract
Changes in the expression level of Oct-1A, Oct-1L, Oct-1X, and Oct-1Z isoforms and CD14 surface antigen during differentiation of HL-60 monocytic cells induced in vitro by dimethyl sulfoxide were studied, and the expression level of the four Oct-1 isoforms in vivo in human monocytes was determined.
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Affiliation(s)
- A G Stepchenko
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, ul. Vavilova 32, Moscow, 119991, Russia
| | - B M Lyanova
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, ul. Vavilova 32, Moscow, 119991, Russia
| | - I D Krylova
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, ul. Vavilova 32, Moscow, 119991, Russia. .,Moscow State Pedagogical University, Moscow, 119992, Russia.
| | - Yu V Ilyin
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, ul. Vavilova 32, Moscow, 119991, Russia
| | - S G Georgieva
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, ul. Vavilova 32, Moscow, 119991, Russia
| | - E V Pankratova
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, ul. Vavilova 32, Moscow, 119991, Russia
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8
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TP53 gain-of-function mutation promotes inflammation in glioblastoma. Cell Death Differ 2018; 26:409-425. [PMID: 29786075 DOI: 10.1038/s41418-018-0126-3] [Citation(s) in RCA: 116] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 04/09/2018] [Accepted: 05/02/2018] [Indexed: 12/21/2022] Open
Abstract
Glioblastoma (GBM), the most severe and common brain tumor in adults, is characterized by multiple somatic mutations and aberrant activation of inflammatory responses. Immune cell infiltration and subsequent inflammation cause tumor growth and resistance to therapy. Somatic loss-of-function mutations in the gene encoding tumor suppressor protein p53 (TP53) are frequently observed in various cancers. However, numerous studies suggest that TP53 regulates malignant phenotypes by gain-of-function (GOF) mutations. Here we demonstrate that a TP53 GOF mutation promotes inflammation in GBM. Ectopic expression of a TP53 GOF mutant induced transcriptomic changes, which resulted in enrichment of gene signatures related to inflammation and chemotaxis. Bioinformatics analyses revealed that a gene signature, upregulated by the TP53 GOF mutation, is associated with progression and shorter overall survival in GBM. We also observed significant correlations between the TP53 GOF mutation signature and inflammation in the clinical database of GBM and other cancers. The TP53 GOF mutant showed upregulated C-C motif chemokine ligand 2 (CCL2) and tumor necrosis factor alpha (TNFA) expression via nuclear factor kappa B (NFκB) signaling, consequently increasing microglia and monocyte-derived immune cell infiltration. Additionally, TP53 GOF mutation and CCL2 and TNFA expression correlated positively with tumor-associated immunity in patients with GBM. Taken together, our findings suggest that the TP53 GOF mutation plays a crucial role in inflammatory responses, thereby deteriorating prognostic outcomes in patients with GBM.
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9
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Fahimi F, Tohidkia MR, Fouladi M, Aghabeygi R, Samadi N, Omidi Y. Pleiotropic cytotoxicity of VacA toxin in host cells and its impact on immunotherapy. ACTA ACUST UNITED AC 2017; 7:59-71. [PMID: 28546954 PMCID: PMC5439391 DOI: 10.15171/bi.2017.08] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Revised: 02/09/2017] [Accepted: 02/13/2017] [Indexed: 12/17/2022]
Abstract
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Introduction: In the recent decades, a number of studies have highlighted the importance of Helicobacter pylori in the initiation and development of peptic ulcer and gastric cancer. Some potential virulence factors (e.g., urease, CagA, VacA, BabA) are exploited by this microorganism, facilitating its persistence through evading human defense mechanisms. Among these toxins and enzymes, vacuolating toxin A (VacA) is of a great importance in the pathogenesis of H. pylori. VacA toxin shows different pattern of cytotoxicity through binding to different cell surface receptors in various cells.
Methods: To highlight attempts in treatment for H. pylori infection, here, we discussed the VacA potential as a candidate for development of vaccine and targeted immunotherapy. Furthermore, we reviewed the related literature to provide key insights on association of the genetic variants of VacA with the toxicity of the toxin in cells.
Results: A number of investigations on the receptor(s) binding of VacA toxin confirmed the pleiotropic nature of VacA that uses a unique mechanism for internalization through some membrane components such as lipid rafts and glycophosphatidylinositol (GPI)-anchored proteins (GPI-AP). Considering the high potency of VacA toxin in the clinical presentations in infection and assisting persistence and colonization of H. pylori, it is considered as one of the pivotal components in production vaccines and monoclonal antibodies (mAbs).
Conclusion: It is possible to generate mAbs with a considerable potential to convert into secretory immunoglobulins that could penetrate into the niche of H. pylori and inhibit its normal functionalities. Further, conjugation of H. pylori targeting Ab fragments with the toxic agents or drug delivery systems (DDSs) offers new generation of H. pylori treatments.
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Affiliation(s)
- Farnaz Fahimi
- Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Mohammad Reza Tohidkia
- Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Mehdi Fouladi
- Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Reza Aghabeygi
- School of Advanced Biomedical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Naser Samadi
- School of Advanced Biomedical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Yadollah Omidi
- Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran.,School of Advanced Biomedical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran.,Department of Pharmaceutics, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran
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10
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Zhou ZL, Ma J, Tong MH, Chan BP, Wong AST, Ngan AHW. Nanomechanical measurement of adhesion and migration of leukemia cells with phorbol 12-myristate 13-acetate treatment. Int J Nanomedicine 2016; 11:6533-6545. [PMID: 27994457 PMCID: PMC5153271 DOI: 10.2147/ijn.s118065] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
The adhesion and traction behavior of leukemia cells in their microenvironment is directly linked to their migration, which is a prime issue affecting the release of cancer cells from the bone marrow and hence metastasis. In assessing the effectiveness of phorbol 12-myristate 13-acetate (PMA) treatment, the conventional batch-cell transwell-migration assay may not indicate the intrinsic effect of the treatment on migration, since the treatment may also affect other cellular behavior, such as proliferation or death. In this study, the pN-level adhesion and traction forces between single leukemia cells and their microenvironment were directly measured using optical tweezers and traction-force microscopy. The effects of PMA on K562 and THP1 leukemia cells were studied, and the results showed that PMA treatment significantly increased cell adhesion with extracellular matrix proteins, bone marrow stromal cells, and human fibroblasts. PMA treatment also significantly increased the traction of THP1 cells on bovine serum albumin proteins, although the effect on K562 cells was insignificant. Western blots showed an increased expression of E-cadherin and vimentin proteins after the leukemia cells were treated with PMA. The study suggests that PMA upregulates adhesion and thus suppresses the migration of both K562 and THP1 cells in their microenvironment. The ability of optical tweezers and traction-force microscopy to measure directly pN-level cell–protein or cell–cell contact was also demonstrated.
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Affiliation(s)
| | - Jing Ma
- School of Biological Sciences, University of Hong Kong, Hong Kong, People's Republic of China
| | | | | | - Alice Sze Tsai Wong
- School of Biological Sciences, University of Hong Kong, Hong Kong, People's Republic of China
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11
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Yahiro K, Hirayama T, Moss J, Noda M. New Insights into VacA Intoxication Mediated through Its Cell Surface Receptors. Toxins (Basel) 2016; 8:toxins8050152. [PMID: 27187473 PMCID: PMC4885067 DOI: 10.3390/toxins8050152] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 05/05/2016] [Accepted: 05/06/2016] [Indexed: 12/17/2022] Open
Abstract
Helicobacter pylori (H. pylori), a major cause of gastroduodenal diseases, produces VacA, a vacuolating cytotoxin associated with gastric inflammation and ulceration. The C-terminal domain of VacA plays a crucial role in receptor recognition on target cells. We have previously identified three proteins (i.e., RPTPα, RPTPβ, and LRP1) that serve as VacA receptors. These receptors contribute to the internalization of VacA into epithelial cells, activate signal transduction pathways, and contribute to cell death and gastric ulceration. In addition, other factors (e.g., CD18, sphingomyelin) have also been identified as cell-surface, VacA-binding proteins. Since we believe that, following interactions with its host cell receptors, VacA participates in events leading to disease, a better understanding of the cellular function of VacA receptors may provide valuable information regarding the mechanisms underlying the pleiotropic actions of VacA and the pathogenesis of H. pylori-mediated disease. In this review, we focus on VacA receptors and their role in events leading to cell damage.
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Affiliation(s)
- Kinnosuke Yahiro
- Department of Molecular Infectiology, Graduate School of Medicine, Chiba University, 1-8-1, Inohana, Chuo-ku, Chiba 260-8670, Japan.
| | - Toshiya Hirayama
- Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, 1-12-4, Sakamoto, Nagasaki 852-8523, Japan.
| | - Joel Moss
- Cardiovascular and Pulmonary Branch, NHLBI, NIH, Building 10, Room 6D03, MSC 1590, Bethesda, MD 20892-1590, USA.
| | - Masatoshi Noda
- Department of Molecular Infectiology, Graduate School of Medicine, Chiba University, 1-8-1, Inohana, Chuo-ku, Chiba 260-8670, Japan.
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12
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Junaid M, Linn AK, Javadi MB, Al-Gubare S, Ali N, Katzenmeier G. Vacuolating cytotoxin A (VacA) - A multi-talented pore-forming toxin from Helicobacter pylori. Toxicon 2016; 118:27-35. [PMID: 27105670 DOI: 10.1016/j.toxicon.2016.04.037] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 03/12/2016] [Accepted: 04/18/2016] [Indexed: 12/18/2022]
Abstract
Helicobacter pylori is associated with severe and chronic diseases of the stomach and duodenum such as peptic ulcer, non-cardial adenocarcinoma and gastric lymphoma, making Helicobacter pylori the only bacterial pathogen which is known to cause cancer. The worldwide rate of incidence for these diseases is extremely high and it is estimated that about half of the world's population is infected with H. pylori. Among the bacterial virulence factors is the vacuolating cytotoxin A (VacA), which represents an important determinant of pathogenicity. Intensive characterization of VacA over the past years has provided insight into an ample variety of mechanisms contributing to host-pathogen interactions. The toxin is considered as an important target for ongoing research for several reasons: i) VacA displays unique features and structural properties and its mechanism of action is unrelated to any other known bacterial toxin; ii) the toxin is involved in disease progress and colonization by H. pylori of the stomach; iii) VacA is a potential and promising candidate for the inclusion as antigen in a vaccine directed against H. pylori and iv) the vacA gene is characterized by a high allelic diversity, and allelic variants contribute differently to the pathogenicity of H. pylori. Despite the accumulation of substantial data related to VacA over the past years, several aspects of VacA-related activity have been characterized only to a limited extent. The biologically most significant effect of VacA activity on host cells is the formation of membrane pores and the induction of vacuole formation. This review discusses recent findings and advances on structure-function relations of the H. pylori VacA toxin, in particular with a view to membrane channel formation, oligomerization, receptor binding and apoptosis.
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Affiliation(s)
- Muhammad Junaid
- Department of Pharmacy, Division of Pharmacology, University of Malakand, Khyber Pakhtunkhwa 18550, Pakistan; Bacterial Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand.
| | - Aung Khine Linn
- Bacterial Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand.
| | - Mohammad Bagher Javadi
- Bacterial Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand.
| | - Sarbast Al-Gubare
- Bacterial Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand.
| | - Niaz Ali
- Department of Basic Medical Sciences, Khyber Medical University, Peshawar 25000, Pakistan.
| | - Gerd Katzenmeier
- Bacterial Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand.
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13
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Sequence and apoptotic activity of VacA cytotoxin cloned from a Helicobacter pylori Thai clinical isolate. BIOMED RESEARCH INTERNATIONAL 2014; 2014:398350. [PMID: 24963483 PMCID: PMC4052787 DOI: 10.1155/2014/398350] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2013] [Revised: 03/06/2014] [Accepted: 03/08/2014] [Indexed: 02/07/2023]
Abstract
The vacuolating cytotoxin VacA produced by Helicobacter pylori induces the formation of large cytoplasmic vacuoles in host gastric epithelial cells as well as a release of cytochrome C from mitochondria resulting in cell apoptosis. Considerable sequence diversity in VacA relating to different degrees of disease severity is observed with clinical samples from a multitude of geographic places. In this study we describe expression in Escherichia coli, purification to homogeneity and in vitro assay of its apoptotic activity of a VacA toxin from a H. pylori isolate of a Thai patient with gastrointestinal lymphoma. Sequencing revealed that the deduced amino acid sequence of the cloned Thai isolate VacA is similar to H. pylori s1/m2 type strains. The percent sequence similarity to the model strain 60190 was lower due to the presence of extra amino acids in the mid (m) region. The purified VacA toxin exhibited significant apoptotic activity on both T84 and MDCK epithelial cell lines, as revealed by DAPI staining, whereby the observed activity was significantly higher on MDCK cells. These findings could relate to a modulation of VacA activity on host cells in the Thai isolate-VacA toxin that may differ from those of the model strain.
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14
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Aspatwar A, Tolvanen MEE, Ortutay C, Parkkila S. Carbonic anhydrase related proteins: molecular biology and evolution. Subcell Biochem 2014; 75:135-156. [PMID: 24146378 DOI: 10.1007/978-94-007-7359-2_8] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The catalytically inactive isoforms of α-carbonic anhydrases are known as carbonic anhydrase related proteins (CARPs). The CARPs occur independently or as domains of other proteins in animals (both vertebrates and invertebrates) and viruses. The catalytic inactivity of CARPs is due to the lack of histidine residues required for the coordination of the zinc atom. The phylogenetic analysis shows that these proteins are highly conserved across the species. The three CARPs in vertebrates are known as CARP VIII, X and XI. CARPs orthologous to CARP VIII are found in deuterostome invertebrates, whereas protostomes only possess orthologs of CARP X. The CA-like domains of receptor-type protein tyrosine phosphatases (PTPR) are found only in PTPRG and PTPRZ. Most of these CARPs are predominantly expressed in central nervous system. Among the three vertebrate CA isoforms, CARP VIII is functionally associated with motor coordination in human, mouse and zebrafish and certain types of cancers in humans. Vertebrate expression studies show that CARP X is exclusively expressed in the brain. CARP XI is only found in tetrapods and is highly expressed in the central nervous system (CNS) of humans and mice and is also associated with several cancers. CARP VIII, PTPRZ and PTPRG have been shown to coordinate the function of other proteins by protein-protein interaction, and viral CARPs participate in attachment to host cells, but the precise biological function of CARPs X and XI is still unknown. The findings so far suggest many novel functions for the CARP subfamily, most likely related to binding to other proteins.
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Affiliation(s)
- Ashok Aspatwar
- Institute of Biomedical Technology and School of Medicine, University of Tampere and BioMediTech, Tampere, Finland,
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15
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Borrell-Pagès M, Romero JC, Badimon L. LRP5 negatively regulates differentiation of monocytes through abrogation of Wnt signalling. J Cell Mol Med 2013; 18:314-25. [PMID: 24266894 PMCID: PMC3930418 DOI: 10.1111/jcmm.12190] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 10/17/2013] [Indexed: 01/22/2023] Open
Abstract
Molecular changes involved in cell differentiation are only partially known. Circulating inflammatory cells need to differentiate to perform specialized functions in target tissues. Here, we hypothesized that low-density lipoprotein receptor–related protein 5 (LRP5) is involved, through its participation in the canonical Wnt/β-catenin signalling, in the differentiation process of monocytic cells. To this aim, we characterized differentiation mechanisms of HL60 cells and primary human monocytes. We show that silencing the LRP5 gene increased differentiation of HL60 cells and human monocytes, suggesting that LRP5 signalling abrogates differentiation. We demonstrate that the mechanisms behind this blockade include sequestration of β-catenin at the cellular membrane, inhibition of the Wnt signalling and increase of apoptosis. We further demonstrate the involvement of LRP5 and the Wnt/β-catenin signalling in the process because cellular differentiation can be rescued by the addition of downstream Wnt target genes to the monocytic cells.
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Affiliation(s)
- Maria Borrell-Pagès
- Cardiovascular Research Center, CSIC-ICCC, Hospital de la Santa Creu i Sant Pau, IIB-Sant Pau, Barcelona, Spain
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16
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Pachathundikandi SK, Tegtmeyer N, Backert S. Signal transduction of Helicobacter pylori during interaction with host cell protein receptors of epithelial and immune cells. Gut Microbes 2013; 4:454-74. [PMID: 24280762 PMCID: PMC3928158 DOI: 10.4161/gmic.27001] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Helicobacter pylori infections can induce pathologies ranging from chronic gastritis, peptic ulceration to gastric cancer. Bacterial isolates harbor numerous well-known adhesins, vacuolating cytotoxin VacA, protease HtrA, urease, peptidoglycan, and type IV secretion systems (T4SS). It appears that H. pylori targets more than 40 known host protein receptors on epithelial or immune cells. A series of T4SS components such as CagL, CagI, CagY, and CagA can bind to the integrin α 5β 1 receptor. Other targeted membrane-based receptors include the integrins αvβ 3, αvβ 5, and β 2 (CD18), RPTP-α/β, GP130, E-cadherin, fibronectin, laminin, CD46, CD74, ICAM1/LFA1, T-cell receptor, Toll-like receptors, and receptor tyrosine kinases EGFR, ErbB2, ErbB3, and c-Met. In addition, H. pylori is able to activate the intracellular receptors NOD1, NOD2, and NLRP3 with important roles in innate immunity. Here we review the interplay of various bacterial factors with host protein receptors. The contribution of these interactions to signal transduction and pathogenesis is discussed.
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17
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Vaidya M, Panchal H. In silico investigation and structural characterization of virulent factor and a metallo peptidase present in Helicobacter pylori strain J99. Interdiscip Sci 2013; 4:302-9. [PMID: 23354820 DOI: 10.1007/s12539-012-0145-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Revised: 06/07/2012] [Accepted: 06/25/2012] [Indexed: 01/04/2023]
Abstract
VacA is a high-molecular weight multimeric pore-forming protein encoded by the chromosomal gene vacA of Helicobacter pylori J99 strian. It plays a significant role in the development of gastric cancer in human by inducing the formation of vacuoles. Genomics and proteomics features of an organism have provided a plethora of potential drug targets. The crystal structure of VacA is not available in any structural database; hence a 3D structure is very essential for structural studies and discovery of potential inhibitors against proteins. In this study 3D structure of VacA is modelled a by using Bhageerath: an energy based web enabled computer software suite. According to our study VacA steriochemical validation shows 91.7% residues are in allowed region of Ramachandran plot. Further validation was done by WHAT CHECK to provide evidence that the distribution of the main chain bond lengths and omega bond angles were within limits with Z-score 1.0 and error values are negligible. The modelled protein was submitted to Protein Model Database and can be downloaded with PMDID PM0077963. Further we found that metallo peptidase "M3" cleaves VacA and helps in import mechanism in mitochondria. Structure of metallo peptidase is also not available in any structural database so we modelled and validated its structure. With the help of docking studies we blocked the active site of metallo peptidase by ligand LA3 and 294 with binding energy -5.9 and -5.2 KJ/mol respectively, thus prevented import mechanism of VacA in mitochondria. The inhibitors identified from our study were LA3 and 294 ligands. The investigation concluded that these drugs could be used as the potential inhibitors against the damage of stomach and duodenum, which ultimately reduces the likelihood of ulcer as well as gastric cancer.
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Affiliation(s)
- Megha Vaidya
- G.H. Patel P.G. Department of Computer Science & Technology, Sardar Patel University, Vallabh Vidyanagar, Gujarat, India.
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18
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Receptor type protein tyrosine phosphatases (RPTPs) - roles in signal transduction and human disease. J Cell Commun Signal 2012; 6:125-38. [PMID: 22851429 DOI: 10.1007/s12079-012-0171-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 07/12/2012] [Indexed: 01/06/2023] Open
Abstract
Protein tyrosine phosphorylation is a fundamental regulatory mechanism controlling cell proliferation, differentiation, communication, and adhesion. Disruption of this key regulatory mechanism contributes to a variety of human diseases including cancer, diabetes, and auto-immune diseases. Net protein tyrosine phosphorylation is determined by the dynamic balance of the activity of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Mammals express many distinct PTKs and PTPs. Both of these families can be sub-divided into non-receptor and receptor subtypes. Receptor protein tyrosine kinases (RPTKs) comprise a large family of cell surface proteins that initiate intracellular tyrosine phosphorylation-dependent signal transduction in response to binding of extracellular ligands, such as growth factors and cytokines. Receptor-type protein tyrosine phosphatases (RPTPs) are enzymatic and functional counterparts of RPTKs. RPTPs are a family of integral cell surface proteins that possess intracellular PTP activity, and extracellular domains that have sequence homology to cell adhesion molecules. In comparison to extensively studied RPTKs, much less is known about RPTPs, especially regarding their substrate specificities, regulatory mechanisms, biological functions, and their roles in human diseases. Based on the structure of their extracellular domains, the RPTP family can be grouped into eight sub-families. This article will review one representative member from each RPTP sub-family.
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19
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Rassow J. Helicobacter pylori vacuolating toxin A and apoptosis. Cell Commun Signal 2011; 9:26. [PMID: 22044628 PMCID: PMC3266207 DOI: 10.1186/1478-811x-9-26] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 11/01/2011] [Indexed: 12/16/2022] Open
Abstract
VacA, the vacuolating cytotoxin A of Helicobacter pylori, induces apoptosis in epithelial cells of the gastic mucosa and in leukocytes. VacA is released by the bacteria as a protein of 88 kDa. At the outer surface of host cells, it binds to the sphingomyelin of lipid rafts. At least partially, binding to the cells is facilitated by different receptor proteins. VacA is internalized by a clathrin-independent mechanism and initially accumulates in GPI-anchored proteins-enriched early endosomal compartments. Together with early endosomes, VacA is distributed inside the cells. Most of the VacA is eventually contained in the membranes of vacuoles. VacA assembles in hexameric oligomers forming an anion channel of low conductivity with a preference for chloride ions. In parallel, a significant fraction of VacA can be transferred from endosomes to mitochondria in a process involving direct endosome-mitochondria juxtaposition. Inside the mitochondria, VacA accumulates in the mitochondrial inner membrane, probably forming similar chloride channels as observed in the vacuoles. Import into mitochondria is mediated by the hydrophobic N-terminus of VacA. Apoptosis is triggered by loss of the mitochondrial membrane potential, recruitment of Bax and Bak, and release of cytochrome c.
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Affiliation(s)
- Joachim Rassow
- Ruhr-Universität Bochum, Institut für Physiologische Chemie, Medizinische Fakultät, Gebäude MA3, D-44780 Bochum, Germany.
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20
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Allison CC, Ferrero RL. Role of virulence factors and host cell signaling in the recognition of Helicobacter pylori and the generation of immune responses. Future Microbiol 2010; 5:1233-55. [PMID: 20722601 DOI: 10.2217/fmb.10.84] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Helicobacter pylori colonizes a large proportion of the world's population, with infection invariably leading to chronic, lifelong gastritis. While the infection often persists undiagnosed and without causing severe pathology, there are a number of host, bacterial and environmental factors that can influence whether infection provokes a mild inflammatory response or results in significant morbidity. Intriguingly, the most virulent H. pylori strains appear to deliberately induce the epithelial signaling cascades responsible for activating the innate immune system. While the reason for this remains unclear, the resulting adaptive immune responses are largely ineffective in clearing the bacterium once infection has become established and, as a result, inflammation likely causes more damage to the host itself.
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Affiliation(s)
- Cody C Allison
- Centre for Innate Immunity & Infectious Diseases, Monash Institute of Medical Research, Clayton, Australia.
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21
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Jones KR, Whitmire JM, Merrell DS. A Tale of Two Toxins: Helicobacter Pylori CagA and VacA Modulate Host Pathways that Impact Disease. Front Microbiol 2010; 1:115. [PMID: 21687723 PMCID: PMC3109773 DOI: 10.3389/fmicb.2010.00115] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 09/27/2010] [Indexed: 12/16/2022] Open
Abstract
Helicobacter pylori is a pathogenic bacterium that colonizes more than 50% of the world's population, which leads to a tremendous medical burden. H. pylori infection is associated with such varied diseases as gastritis, peptic ulcers, and two forms of gastric cancer: gastric adenocarcinoma and mucosa-associated lymphoid tissue lymphoma. This association represents a novel paradigm for cancer development; H. pylori is currently the only bacterium to be recognized as a carcinogen. Therefore, a significant amount of research has been conducted to identify the bacterial factors and the deregulated host cell pathways that are responsible for the progression to more severe disease states. Two of the virulence factors that have been implicated in this process are cytotoxin-associated gene A (CagA) and vacuolating cytotoxin A (VacA), which are cytotoxins that are injected and secreted by H. pylori, respectively. Both of these virulence factors are polymorphic and affect a multitude of host cellular pathways. These combined facts could easily contribute to differences in disease severity across the population as various CagA and VacA alleles differentially target some pathways. Herein we highlight the diverse types of cellular pathways and processes targeted by these important toxins.
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Affiliation(s)
- Kathleen R Jones
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences Bethesda, MD, USA
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22
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Isomoto H, Moss J, Hirayama T. Pleiotropic actions of Helicobacter pylori vacuolating cytotoxin, VacA. TOHOKU J EXP MED 2010; 220:3-14. [PMID: 20046046 DOI: 10.1620/tjem.220.3] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Helicobacter pylori produces a vacuolating cytotoxin, VacA, and most virulent H. pylori strains secrete VacA. VacA binds to two types of receptor-like protein tyrosine phosphatase (RPTP), RPTPalpha and RPTPbeta, on the surface of host cells. VacA bound to RPTPbeta, relocates and concentrates in lipid rafts in the plasma membrane. VacA causes vacuolization, membrane anion-selective channel and pore formation, and disruption of endosomal and lysosomal activity in host cells. Secreted VacA is processed into p33 and p55 fragments. The p55 domain not only plays a role in binding to target cells but also in the formation of oligomeric structures and anionic membrane channels. Oral administration of VacA to wild-type mice, but not to RPTPbeta knockout mice, resulted in gastric ulcers, in agreement with the clinical effect of VacA. VacA with s1/m1 allele has more potent cytotoxic activity in relation to peptic ulcer disease and appears to be associated with human gastric cancer. VacA activates pro-apoptotic Bcl-2 family proteins, and induces apoptosis via a mitochondria-dependent pathway. VacA can disrupt other signal transduction pathways; VacA activates p38 MAPK, enhancing production of IL-8 and PGE(2), and PI3K/Akt, suppressing GSK-3beta activity. VacA has immunomodulatory actions on T cells and other immune cells, possibly contributing to the chronic infection seen with this organism. H. pylori virulence factors including VacA and CagA, which is encoded by cytotoxin-associated gene A, along with host genetic and environmental factors, constitute a complex network to regulate chronic gastric injury and inflammation, which is involved in a multistep process leading to gastric carcinogenesis.
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Affiliation(s)
- Hajime Isomoto
- Department of Endoscopy, Nagasaki University Hospital, Nagasaki, Japan
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23
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Backert S, Tegtmeyer N. the versatility of the Helicobacter pylori vacuolating cytotoxin vacA in signal transduction and molecular crosstalk. Toxins (Basel) 2010; 2:69-92. [PMID: 22069547 PMCID: PMC3206623 DOI: 10.3390/toxins2010069] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 12/31/2009] [Accepted: 01/14/2010] [Indexed: 12/13/2022] Open
Abstract
By modulating important properties of eukaryotic cells, many bacterial protein toxins highjack host signalling pathways to create a suitable niche for the pathogen to colonize and persist. Helicobacter pylori VacA is paradigm of pore-forming toxins which contributes to the pathogenesis of peptic ulceration. Several cellular receptors have been described for VacA, which exert different effects on epithelial and immune cells. The crystal structure of VacA p55 subunit might be important for elucidating details of receptor interaction and pore formation. Here we discuss the multiple signalling activities of this important toxin and the molecular crosstalk between VacA and other virulence factors.
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Affiliation(s)
- Steffen Backert
- Ardmore House, School of Biomolecular and Biomedical Sciences, Belfield Campus, University College Dublin, Dublin-4, Ireland.
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24
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Paniagua GL, Monroy E, Rodríguez R, Arroniz S, Rodríguez C, Cortés JL, Camacho A, Negrete E, Vaca S. Frequency of vacA, cagA and babA2 virulence markers in Helicobacter pylori strains isolated from Mexican patients with chronic gastritis. Ann Clin Microbiol Antimicrob 2009; 8:14. [PMID: 19405980 PMCID: PMC2683802 DOI: 10.1186/1476-0711-8-14] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Accepted: 04/30/2009] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Helicobacter pylori has been strongly associated with chronic gastritis, peptic and duodenal ulcers, and it is a risk factor for gastric cancer. Three major virulence factors of H. pylori have been described: the vacuolating toxin (VacA), the cytotoxin-associated gene product (CagA) and the adhesion protein BabA2. Since considerable geographic diversity in the prevalence of H. pylori virulence factors has been reported, the aim of this work was to establish the H. pylori and vacA, cagA and babA2 gene status in 238 adult patients, from a marginal urban area of Mexico, with chronic gastritis. METHODS H. pylori was identified in cultures of gastric biopsies by nested PCR. vacA and cagA genes were detected by multiplex PCR, whereas babA2 gene was identified by conventional PCR. RESULTS H. pylori-positive biopsies were 143 (60.1%). All H. pylori strains were vacA+; 39.2% were cagA+; 13.3% were cagA+ babA2+ and 8.4% were babA2+. Mexican strains examined possessed the vacA s1, m1 (43.4%), s1, m2 (24.5%), s2, m1 (20.3%) and s2, m2 (11.9%) genotypes. CONCLUSION These results show that the Mexican patients suffering chronic gastritis we have studied had a high incidence of infection by H. pylori. Forty four percent (63/143) of the H. pylori strains analyzed in this work may be considered as highly virulent since they possessed two or three of the virulence markers analyzed: vacA s1 cagA babA2 (9.8%, 14/143), vacA s1 babA2 (4.9%, 7/143), and vacA s1 cagA (29.4%, 42/143). However, a statistically significant correlation was not observed between vacAs1, cagA and babA2 virulence markers (chi2 test; P > 0.05).
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Affiliation(s)
- Gloria Luz Paniagua
- Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de Mexico, Avenida de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, 54090, Estado de Mexico, Mexico
| | - Eric Monroy
- Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de Mexico, Avenida de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, 54090, Estado de Mexico, Mexico
| | - Raymundo Rodríguez
- Hospital General Regional 72 del Instituto Mexicano del Seguro Social, Av. G. Baz s/n, Tlanepantla, 54000, Estado de Mexico, Mexico
| | - Salvador Arroniz
- Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de Mexico, Avenida de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, 54090, Estado de Mexico, Mexico
| | - Cristina Rodríguez
- Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de Mexico, Avenida de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, 54090, Estado de Mexico, Mexico
| | - José Luis Cortés
- Hospital General Regional 72 del Instituto Mexicano del Seguro Social, Av. G. Baz s/n, Tlanepantla, 54000, Estado de Mexico, Mexico
| | - Ausencio Camacho
- Hospital General Regional 72 del Instituto Mexicano del Seguro Social, Av. G. Baz s/n, Tlanepantla, 54000, Estado de Mexico, Mexico
| | - Erasmo Negrete
- Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de Mexico, Avenida de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, 54090, Estado de Mexico, Mexico
| | - Sergio Vaca
- Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de Mexico, Avenida de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, 54090, Estado de Mexico, Mexico
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25
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Atherton JC. The pathogenesis of Helicobacter pylori-induced gastro-duodenal diseases. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2007; 1:63-96. [PMID: 18039108 DOI: 10.1146/annurev.pathol.1.110304.100125] [Citation(s) in RCA: 448] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Helicobacter pylori is the main cause of peptic ulceration, distal gastric adenocarcinoma, and gastric lymphoma. Only 15% of those colonized develop disease, and pathogenesis depends upon strain virulence, host genetic susceptibility, and environmental cofactors. Virulence factors include the cag pathogenicity island, which induces proinflammatory, pro-proliferative epithelial cell signaling; the cytotoxin VacA, which causes epithelial damage; and an adhesin, BabA. Host genetic polymorphisms that lead to high-level pro-inflammatory cytokine release in response to infection increase cancer risk. Pathogenesis is dependent upon inflammation, a Th-1 acquired immune response and hormonal changes including hypergastrinaemia. Antral-predominant inflammation leads to increased acid production from the uninflamed corpus and predisposes to duodenal ulceration; corpus-predominant gastritis leads to hypochlorhydria and predisposes to gastric ulceration and adenocarcinoma. Falling prevalence of H. pylori in developed countries has led to a falling incidence of associated diseases. However, whether there are disadvantages of an H. pylori-free stomach, for example increased risk of esosphageal adenocarcinoma, remains unclear.
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Affiliation(s)
- John C Atherton
- Wolfson Digestive Diseases Centre and Institute of Infections, Immunity, and Inflammation, University of Nottingham, Nottingham NG7 2UH, United Kingdom.
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26
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Role of arginine metabolism in immunity and immunopathology. Immunobiology 2007; 212:795-812. [PMID: 18086380 DOI: 10.1016/j.imbio.2007.09.008] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Accepted: 09/28/2007] [Indexed: 12/22/2022]
Abstract
A heterogeneous set of cells that are commonly grouped as "myeloid cells", interacts in a complex landscape of physiological and pathological situations. In this review we attempt to trace a profile of the "myeloid connection" through different normal and pathological states, by analyzing common metabolic pathways of the amino acid l-arginine. Myeloid cells exert various, often divergent, actions on the immune response through mechanisms that exploit mediators of this peculiar metabolic pathway, ranging from l-arginine itself to its downstream metabolites, like nitric oxide and polyamines. Various pathological situations, including neoplastic and autoimmune diseases, as well as injury repair and infections are discussed here, showing how l-arginine metabolism is able to play a dual role, both as an active protector and a possible threat to the organism.
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27
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Affiliation(s)
- Toshiya Hirayama
- Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University
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28
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Abstract
VacA, the only protein toxin produced by Helicobacter pylori, vacuolates cultured cells. The presence of 2 VacA receptors has been demonstrated. One is the receptor-type protein tyrosine phosphatase (RPTP) zeta/beta (PTP zeta/beta), and the other is RPTP alpha. VacA binds to PTP zeta/beta, resulting in gastric epithelial detachment through the tyrosine phosphorylation of Git-1, which then leads to gastric ulceration by the direct action of gastric acid. Thus, disturbance of adhesion between gastric epithelial cells and the extracellular matrix due to an abnormal PTP zeta/beta signal is the main mechanism of gastric ulceration.
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Affiliation(s)
- Daisuke Shirasaka
- Division of Digestive Disease, Kobe University Graduate School of Medicine, Kobe, Japan.
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29
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Brest P, Hofman V, Lassalle S, Césaro A, Ricci V, Selva E, Auberger P, Hofman P. Human polymorphonuclear leukocytes are sensitive in vitro to Helicobacter pylori vaca toxin. Helicobacter 2006; 11:544-55. [PMID: 17083376 DOI: 10.1111/j.1523-5378.2006.00457.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
BACKGROUND Interactions between bacterial components and polymorphonuclear leukocytes (PMNL) play a major pathogenic role in Helicobacter pylori-associated diseases. Activation of PMNL can be induced by contact with whole bacteria or by different H. pylori products released in the extracellular space either by active secretion or by bacterial autolysis. Among these products, H. pylori VacA is a secreted toxin inducing vacuolation and apoptosis of epithelial cells. METHODS AND RESULTS We found that non-opsonic human PMNL were sensitive to the vacuolating effect of VacA+ broth culture filtrate (BCF) and of purified VacA toxin. PMNL incubated with VacA+ BCF showed Rab7-positive large intracytoplasmic vacuoles. PMNL preincubation with H. pylori BCF of different phenotypes dramatically potentialized the oxidative burst induced by zymosan, increased phagocytosis of opsonized fluorescent beads, and up-regulated CD11b cell surface expression, but independently of the BCF VacA phenotype. Moreover, by using purified VacA toxin we showed that vacuolation induced in PMNL did not modify the rate of spontaneous PMNL apoptosis measured by caspase 3 activity. CONCLUSIONS Taken together, these data showed that human PMNL is a sensitive cell population to H. pylori VacA toxin. However, activation of PMNL (i.e., oxidative burst, phagocytosis, CD11b up-regulation) and PMNL apoptosis are not affected by VacA, raising question about the role of VacA toxin on PMNL in vivo.
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Affiliation(s)
- Patrick Brest
- INSERM ERI-21, Pasteur'Hospital and Faculty of Medicine, University of Nice, Nice, France
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Nakayama M, Hisatsune J, Yamasaki E, Nishi Y, Wada A, Kurazono H, Sap J, Yahiro K, Moss J, Hirayama T. Clustering of Helicobacter pylori VacA in lipid rafts, mediated by its receptor, receptor-like protein tyrosine phosphatase beta, is required for intoxication in AZ-521 Cells. Infect Immun 2006; 74:6571-80. [PMID: 17030583 PMCID: PMC1698068 DOI: 10.1128/iai.00356-06] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Helicobacter pylori vacuolating cytotoxin, VacA, induces multiple effects on epithelial cells through different cellular events: one involves pore formation, leading to vacuolation, mitochondrial damage, and apoptosis, and the second involves cell signaling, resulting in stimulation of proinflammatory responses and cell detachment. Our recent data demonstrated that VacA uses receptor-like protein tyrosine phosphatase beta (RPTPbeta) as a receptor, of which five residues (QTTQP) at positions 747 to 751 are involved in binding. In AZ-521 cells, which mainly express RPTPbeta, VacA, after binding to RPTPbeta in non-lipid raft microdomains on the cell surface, is localized with RPTPbeta in lipid rafts in a temperature- and VacA concentration-dependent process. Methyl-beta-cyclodextrin (MCD) did not block binding to RPTPbeta but inhibited translocation of VacA with RPTPbeta to lipid rafts and all subsequent events. On the other hand, 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), which disrupts anion channels, did not inhibit translocation of VacA to lipid rafts or VacA-induced activation of p38 mitogen-activated protein (MAP) kinase, but inhibited VacA internalization followed by vacuolation. Thus, p38 MAP kinase activation did not appear to be required for internalization. In contrast, phosphatidylinositol-specific phospholipase C (PI-PLC) inhibited translocation, as well as p38 MAP kinase/ATF-2 activation, internalization, and VacA-induced vacuolation. Neither NPPB nor PI-PLC affected VacA binding to cells and to its receptor, RPTPbeta. Thus, receptor-dependent translocation of VacA to lipid rafts is critical for signaling pathways leading to p38 MAP kinase/ATF-2 activation and vacuolation.
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Affiliation(s)
- Masaaki Nakayama
- Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki 8528523, Japan
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31
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De Guzman BB, Hisatsune J, Nakayama M, Yahiro K, Wada A, Yamasaki E, Nishi Y, Yamazaki S, Azuma T, Ito Y, Ohtani M, van der Wijk T, den Hertog J, Moss J, Hirayama T. Cytotoxicity and recognition of receptor-like protein tyrosine phosphatases, RPTPalpha and RPTPbeta, by Helicobacter pylori m2VacA. Cell Microbiol 2006; 7:1285-93. [PMID: 16098216 DOI: 10.1111/j.1462-5822.2005.00556.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Helicobacter pylori vacuolating cytotoxin, VacA, induces vacuolation in mammalian cell lines. Sequence differences in the middle of VacA molecules define two families, termed m1VacA and m2VacA, which differ in cell specificity. Similar to m1VacA, m2VacA is activated by acid or alkali, which enhances its binding to cells. Immunoprecipitation experiments showed that, in AZ-521 cells, activated m2VacA, similar to m1VacA, binds to two receptor-like protein tyrosine phosphatases, RPTPalpha and RPTPbeta suggesting that activated m2VacA as well as m1VacA may contribute to gastrointestinal disease following H. pylori infection. G401 cells express RPTPalpha, not RPTPbeta, and responded to both m1VacA and m2VacA. HeLa cells likewise expressed RPTPalpha, not RPTPbeta, but, in contrast to other cell lines, responded poorly to m2VacA. m1VacA associated with RPTPalpha of HeLa cells to an extent similar to that in other toxin-sensitive cells, whereas activated m2VacA bound HeLa cell RPTPalpha less well, consistent with its low vacuolating activity against these cells. The molecular mass of RPTPalpha from HeLa cells is less than that of the protein from G401 cells, although their extracellular amino acid sequences are virtually identical, with only two amino acid differences noted. Different post-translational modifications of RPTPalpha in HeLa cells may be responsible for the reduced susceptibility to m2VacA.
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Affiliation(s)
- Blanquita B De Guzman
- Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki 8528523, Japan
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32
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Skibinski DAG, Genisset C, Barone S, Telford JL. The cell-specific phenotype of the polymorphic vacA midregion is independent of the appearance of the cell surface receptor protein tyrosine phosphatase beta. Infect Immun 2006; 74:49-55. [PMID: 16368956 PMCID: PMC1346600 DOI: 10.1128/iai.74.1.49-55.2006] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
There are two alleles, m1 and m2, of the midregion of the vacuolating cytotoxin gene (vacA) of Helicobacter pylori which code for toxins with different cell specificities. Here we describe the construction of five chimeric strains in which regions of vacA were exchanged between the two genotypes. By analyzing the toxicity of these strains for HeLa and RK13 cells we have confirmed that a 148-amino-acid region determines the phenotypic differences between the two forms of the protein and that this entire region is important for cytotoxicity. Furthermore, we have used our chimeric strains to investigate whether variations in the midregion of VacA have an effect on phorbol 12-myristate 13-acetate (PMA)-induced VacA sensitivity in HL-60 cells. The PMA-induced VacA sensitivity of HL-60 cells has been previously associated with the appearance of the cell surface receptor protein tyrosine phosphatase beta (RPTPbeta). Our data indicate that both the m1 and m2 forms of VacA are able to utilize RPTPbeta, and the cell-specific phenotype of the midregion is independent of the presence of RPTPbeta. It appears that another as-yet-unidentified receptor exists in HL-60 cells that accounts for the m2 phenotype in this cell line. Also, by studying the effect of PMA on levels of RPTPbeta in other cell lines and toxicity of VacA in these cell lines we have shown that RPTPbeta does not play a major role in the vacuolation of HeLa cells.
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Yahiro K, Shirasaka D, Tagashira M, Wada A, Morinaga N, Kuroda F, Choi O, Inoue M, Aoyama N, Ikeda M, Hirayama T, Moss J, Noda M. Inhibitory effects of polyphenols on gastric injury by Helicobacter pylori VacA toxin. Helicobacter 2005; 10:231-9. [PMID: 15904481 DOI: 10.1111/j.1523-5378.2005.00315.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Helicobacter pylori induces gastric damage and may be involved in the pathogenesis of gastric cancer. H. pylori-vacuolating cytotoxin, VacA, is one of the important virulence factors, and is responsible for H. pylori-induced gastritis and ulceration. The aim of this study is to assess whether several naturally occurring polyphenols inhibit VacA activities in vitro and in vivo. MATERIALS AND METHODS Effects of polyphenols on VacA were quantified by the inhibition of: 1, vacuolation; 2, VacA binding to AZ-521 or G401 cells or its receptors; 3, VacA internalization. Effects of hop bract extract (HBT) containing high molecular weight polymerized catechin on VacA in vivo were investigated by quantifying gastric damage after oral administration of toxins to mice. RESULTS HBT had the strongest inhibitory activity among the polyphenols investigated. HBT inhibited, in a concentration-dependent manner: 1, VacA binding to its receptors, RPTP(alpha) and RPTP(beta); 2, VacA uptake; 3, VacA-induced vacuolation in susceptible cells. In addition, oral administration of HBT with VacA to mice reduced VacA-induced gastric damage at 48 hours. In vitro, VacA formed a complex with HBT. CONCLUSIONS HBT may suppress the development of inflammation and ulceration caused by H. pylori VacA, suggesting that HBT may be useful as a new type of therapeutic agent for the prevention of gastric ulcer and inflammation caused by VacA.
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Affiliation(s)
- Kinnosuke Yahiro
- Department of Molecular Infectiology, Graduate School of Medicine, Chiba University, Chiba, Japan
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Abstract
Bacterial protein toxins alter eukaryotic cellular processes and enable bacteria to successfully colonize their hosts. In recent years, there has been increased recognition that many bacterial toxins are multifunctional proteins that can have pleiotropic effects on mammalian cells and tissues. In this review, we examine a multifunctional toxin (VacA) that is produced by the bacterium Helicobacter pylori. The actions of H. pylori VacA represent a paradigm for how bacterial secreted toxins contribute to colonization and virulence in multiple ways.
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Affiliation(s)
- Timothy L Cover
- Departments of Medicine, and Microbiology and Immunology, Division of Infectious Diseases, Vanderbilt University School of Medicine and Veterans Administration Medical Center, Nashville, Tennessee 37232, USA.
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35
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Torres VJ, Ivie SE, McClain MS, Cover TL. Functional properties of the p33 and p55 domains of the Helicobacter pylori vacuolating cytotoxin. J Biol Chem 2005; 280:21107-14. [PMID: 15817461 DOI: 10.1074/jbc.m501042200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Helicobacter pylori secretes an 88-kDa vacuolating cytotoxin (VacA) that may contribute to the pathogenesis of peptic ulcer disease and gastric cancer. VacA cytotoxic activity requires assembly of VacA monomers into oligomeric structures, formation of anion-selective membrane channels, and entry of VacA into host cells. In this study, we analyzed the functional properties of recombinant VacA fragments corresponding to two putative VacA domains (designated p33 and p55). Immunoprecipitation experiments indicated that these two domains can interact with each other to form protein complexes. In comparison to the individual VacA domains, a mixture of the p33 and p55 proteins exhibited markedly enhanced binding to the plasma membrane of mammalian cells. Furthermore, internalization of the VacA domains was detected when cells were incubated with the p33/p55 mixture but not when the p33 and p55 proteins were tested individually. Incubation of cells with the p33/p55 mixture resulted in cell vacuolation, whereas the individual domains lacked detectable cytotoxic activity. Interestingly, sequential addition of p55 followed by p33 resulted in VacA internalization and cell vacuolation, whereas sequential addition in the reverse order was ineffective. These results indicate that both the p33 and p55 domains contribute to the binding and internalization of VacA and that both domains are required for vacuolating cytotoxic activity. Reconstitution of toxin activity from two separate domains, as described here for VacA, has rarely been described for pore-forming bacterial toxins, which suggests that VacA is a pore-forming toxin with unique structural properties.
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Affiliation(s)
- Victor J Torres
- Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2605, USA
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36
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Ohnita K, Isomoto H, Honda S, Wada A, Wen CY, Nishi Y, Mizuta Y, Hirayama T, Kohno S. Helicobacter pylori strain-specific modulation of gastric inflammation in Mongolian gerbils. World J Gastroenterol 2005; 11:1549-53. [PMID: 15770736 PMCID: PMC4305702 DOI: 10.3748/wjg.v11.i10.1549] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: The cag pathogenicity island (PAI) is one of potential virulence determinants of Helicobacter pylori. The Mongolian gerbil is a suitable experimental animal for the screening of virulence factors of H pylori.
METHODS: Five-week-old Mongolian gerbils were inoculated with a standard H pylori strain (ATCC 43504) possessing the cag PAI or a clinical isolate lacking the genes’ cluster (OHPC-0002). The animals were killed at 2, 4, 8, 24 and 48 wk after inoculation (n = 5 each), and macroscopic and histopathological findings in the stomachs were compared.
RESULTS: In gerbils infected with ATCC 43504, a more severe degree of infiltration of polynuclear and mononuclear cells and lymphoid follicles was observed from 4 wk after inoculation compared to gerbils infected with OHPC-0002 especially in the antrum and transitional zone from the fundic to pyloric gland area. In addition, glandular atrophy, intestinal metaplasia, gastric ulcer and hyperplastic polyps were noted in gerbils infected with ATCC 43504, whereas only mild gastric erosions occurred in those infected with OHPC-0002.
CONCLUSION: Our results indicate that the cag PAI could be directly involved in gastric immune and inflammatory responses in the Mongolian gerbils, leading to a more advanced gastric disease.
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Affiliation(s)
- Ken Ohnita
- Second Department of Internal Medicine, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki, Japan
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37
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Henderson IR, Navarro-Garcia F, Desvaux M, Fernandez RC, Ala'Aldeen D. Type V protein secretion pathway: the autotransporter story. Microbiol Mol Biol Rev 2004; 68:692-744. [PMID: 15590781 PMCID: PMC539010 DOI: 10.1128/mmbr.68.4.692-744.2004] [Citation(s) in RCA: 635] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Gram-negative bacteria possess an outer membrane layer which constrains uptake and secretion of solutes and polypeptides. To overcome this barrier, bacteria have developed several systems for protein secretion. The type V secretion pathway encompasses the autotransporter proteins, the two-partner secretion system, and the recently described type Vc or AT-2 family of proteins. Since its discovery in the late 1980s, this family of secreted proteins has expanded continuously, due largely to the advent of the genomic age, to become the largest group of secreted proteins in gram-negative bacteria. Several of these proteins play essential roles in the pathogenesis of bacterial infections and have been characterized in detail, demonstrating a diverse array of function including the ability to condense host cell actin and to modulate apoptosis. However, most of the autotransporter proteins remain to be characterized. In light of new discoveries and controversies in this research field, this review considers the autotransporter secretion process in the context of the more general field of bacterial protein translocation and exoprotein function.
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Affiliation(s)
- Ian R Henderson
- Division of Immunity and Infection, University of Birmingham, Birmingham B15 2TT, UK.
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38
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Yahiro K, Wada A, Yamasaki E, Nakayama M, Nishi Y, Hisatsune J, Morinaga N, Sap J, Noda M, Moss J, Hirayama T. Essential domain of receptor tyrosine phosphatase beta (RPTPbeta) for interaction with Helicobacter pylori vacuolating cytotoxin. J Biol Chem 2004; 279:51013-21. [PMID: 15383529 DOI: 10.1074/jbc.m406473200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Helicobacter pylori produces a potent exotoxin, VacA, which causes progressive vacuolation as well as gastric injury. Although VacA was able to interact with two receptor-like protein tyrosine phosphatases, RPTPbeta and RPTPalpha, RPTPbeta was found to be responsible for gastric damage caused by VacA. To define the region of RPTPbeta involved in VacA binding, we made mutants of human cDNA RPTPbeta-B, a short receptor form of RPTPbeta. Immunoprecipitation experiments to assess VacA binding to RPTPbeta-B mutants indicated that five residues (QTTQP) at positions 747-751 of the extracellular domain of RPTPbeta-B (which is commonly retained in RPTPbeta-A, a long form of RPTPbeta) play a crucial role in its interaction with VacA, resulting in vacuolation as well as Git-1 phosphorylation. Transfected cells expressing deletion mutant Delta752, which lacks QTTQP, or the double point mutant Delta747 (T748A,T749A) had diminished vacuolation in response to VacA. Treatment of RPTPbeta-B and Delta747 (which have QTTQP at 747-751) with neuraminidase and O-glycosidase diminished their VacA binding, whereas chondroitinase ABC did not have an effect. No inhibitory effect of pleiotrophin, a natural RPTPbeta ligand, on VacA binding to RPTPbeta-B or Delta747 was observed, supporting the conclusion that the extracellular region of RPTPbeta-B responsible for VacA binding is different from that involved in binding pleiotrophin. These data define the region in the RPTPbeta extracellular domain critical for VacA binding, in particular the sequence QTTQP at positions 747-751 with crucial threonines at positions 748 and 749 and are consistent with a role for terminal sialic acids possibly because of threonine glycosylation.
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Affiliation(s)
- Kinnosuke Yahiro
- Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki 8528523, Japan
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39
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Fischer W, Gebert B, Haas R. Novel activities of the Helicobacter pylori vacuolating cytotoxin: from epithelial cells towards the immune system. Int J Med Microbiol 2004; 293:539-47. [PMID: 15149029 DOI: 10.1078/1438-4221-00300] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
H. pylori has developed a unique set of virulence factors, which allow its survival in a unique ecological niche, the human stomach. The vacuolating cytotoxin (VacA) and the cytotoxin-associated antigen (CagA) are major bacterial factors involved in modulating the host. VacA, so far mainly regarded as a cytotoxin for the gastric epithelial cell layer, apparently has profound effects in modulating the immune response. In this review we discuss some of the classical effects of VacA, such as cell vacuolation, and compare them with more recently identified mechanisms of VacA on immune cells.
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Affiliation(s)
- Wolfgang Fischer
- Max von Pettenkofer Institut für Hygiene und Medizinische Mikrobiologie, LMU München, München, Germany
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40
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de Bernard M, Cappon A, Del Giudice G, Rappuoli R, Montecucco C. The multiple cellular activities of the VacA cytotoxin of Helicobacter pylori. Int J Med Microbiol 2004; 293:589-97. [PMID: 15149036 DOI: 10.1078/1438-4221-00299] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Helicobacter pylori has elaborated a unique set of virulence factors that allow it to colonize the stomach wall. These factors include urease, helicoidal shape, flagella, adhesion and pro-inflammatory molecules. Here we discuss the molecular and cellular mechanisms of action of the vacuolating cytotoxin VacA. Its activities are discussed in terms of tissue alterations which promote the release of nutrients necessary to the growth and survival of the bacterium in its nutrient-poor ecological niche. This toxin also shows some pro-inflammatory and immunosuppressive activities which may be functional to the establishment of a chronic type of inflammation.
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Affiliation(s)
- Marina de Bernard
- Dipartimento di Scienze Biomediche, Università di Padova, Istituto Veneto di Medicina Molecolare, Padova, Italy
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41
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Boncristiano M, Paccani SR, Barone S, Ulivieri C, Patrussi L, Ilver D, Amedei A, D'Elios MM, Telford JL, Baldari CT. The Helicobacter pylori vacuolating toxin inhibits T cell activation by two independent mechanisms. ACTA ACUST UNITED AC 2004; 198:1887-97. [PMID: 14676300 PMCID: PMC2194151 DOI: 10.1084/jem.20030621] [Citation(s) in RCA: 209] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Helicobacter pylori toxin, VacA, damages the gastric epithelium by erosion and loosening of tight junctions. Here we report that VacA also interferes with T cell activation by two different mechanisms. Formation of anion-specific channels by VacA prevents calcium influx from the extracellular milieu. The transcription factor NF-AT thus fails to translocate to the nucleus and activate key cytokine genes. A second, channel-independent mechanism involves activation of intracellular signaling through the mitogen-activated protein kinases MKK3/6 and p38 and the Rac-specific nucleotide exchange factor, Vav. As a consequence of aberrant Rac activation, disordered actin polymerization is stimulated. The resulting defects in T cell activation may help H. pylori to prevent an effective immune response leading to chronic colonization of its gastric niche.
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42
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Abstract
PURPOSE OF REVIEW Helicobacter pylori remains one of the world's most prevalent bacterial pathogens, often causing gastritis, peptic ulcer disease, gastric mucosa-associated lymphatic tissue lymphoma, or gastric adenocarcinoma. Elucidation of H. pylori virulence mechanisms and characteristics of the host that contribute to pathogenesis will facilitate the development of both pharmacologic and immunologic therapies. RECENT FINDINGS The functional status of the outer inflammatory protein A may have predictive value for duodenal ulcer, and host alleles for interleukin-1beta, interleukin-1R, tumor necrosis factor-alpha, and interleukin-10 correlate with increased risk for gastric cancer. H. pylori vacuolating cytotoxin A and cytotoxin-associated gene A protein interact with multiple host proteins, although downstream signaling events need further characterization. It does appear however, that CagA may participate in a negative feedback loop on Src family kinases to prevent further phosphorylation of CagA. Several models, including delayed type hypersensitivity in immune mice, and spontaneous clearance of H. pylori from interleukin-10 and phagocyte oxidase mice, provide evidence that severe inflammation may be sufficient to eradicate H. pylori. The strategies used by H. pylori to avoid the inflammatory response are also becoming clearer. H. pylori remains viable when internalized by epithelial cells, and it remains viable in macrophage phagosomes by inhibiting phagosome maturation. Additionally, H. pylori may regulate the host immune response through activation of dendritic cells and CD25 regulatory T cells, and it may direct immunosuppression of T cells. SUMMARY Helicobacter pylori virulence is accomplished through many mechanisms, including vacuolating cytotoxin A and CagA activities, and may be predicted based on bacterial and host genotypes. Ultimately, H. pylori persistence may depend on its success in downregulating the inflammatory response.
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Affiliation(s)
- Thomas G Blanchard
- Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA.
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43
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Montecucco C, de Bernard M. Molecular and cellular mechanisms of action of the vacuolating cytotoxin (VacA) and neutrophil-activating protein (HP-NAP) virulence factors of Helicobacter pylori. Microbes Infect 2003; 5:715-21. [PMID: 12814772 DOI: 10.1016/s1286-4579(03)00124-2] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Helicobacter pylori has elaborated a unique set of virulence factors that allow it to colonise the stomach wall. These factors include urease, helicoidal shape, flagella and adhesion molecules. Here we discuss the molecular characteristics and mechanisms of action of the vacuolating cytotoxin, VacA, and the neutrophil-activating protein, HP-NAP. Their activities are discussed in terms of tissue alterations, which promote the release of nutrients necessary for the growth and survival of the bacterium in its nutrient-poor ecological niche.
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Affiliation(s)
- Cesare Montecucco
- Dipartimento di Scienze Biomediche, Università di Padova, Via G. Colombo 3, 35121 Padua, Italy.
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44
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Kimura T, Wada A, Nakayama M, Ogushi KI, Nishi Y, De Guzman BB, Moss J, Hirayama T. High molecular weight factor in FCS inhibits Helicobacter pylori VacA-binding to its receptor, RPTPbeta, on AZ-521. Microbiol Immunol 2003; 47:105-7. [PMID: 12636260 DOI: 10.1111/j.1348-0421.2003.tb02792.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
VacA, a secretory product of Helicobacter pylori, binds to its cell surface receptor, receptor tyrosine phosphatase (RPTP) beta, leading to cytoplasmic vacuolization of gastric epithelial AZ-521 cells. VacA binding to the cell surface and VacA-dependent vacuolization were inhibited by cell culture media containing fetal calf serum (FCS). The high molecular weight fraction of FCS isolated by Superose 12 gel filtration chromatography inhibited VacA binding, whereas only weak effects were observed with other fractions. These data show that the high molecular weight fraction of FCS inhibits VacA action though its ability to block toxin binding to its receptor, RPTPbeta, on AZ-521 cells.
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Affiliation(s)
- Takahiro Kimura
- Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Nagasaki 852-8523, Japan
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45
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Yahiro K, Wada A, Nakayama M, Kimura T, Ogushi KI, Niidome T, Aoyagi H, Yoshino KI, Yonezawa K, Moss J, Hirayama T. Protein-tyrosine phosphatase alpha, RPTP alpha, is a Helicobacter pylori VacA receptor. J Biol Chem 2003; 278:19183-9. [PMID: 12626515 DOI: 10.1074/jbc.m300117200] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Helicobacter pylori vacuolating cytotoxin, VacA, induces vacuolation, mitochondrial damage, cytochrome c release, and apoptosis of gastric epithelial cells. To detect gastric proteins that serve as VacA receptors, we used VacA co-immunoprecipitation techniques following biotinylation of the cell surface and identified p250, a receptor-like protein-tyrosine phosphatase beta (RPTP beta) as a VacA-binding protein (Yahiro, K., Niidome, T., Kimura, M., Hatakeyama, T., Aoyagi, H., Kurazono, H., Imagawa, K., Wada, A., Moss, J., and Hirayama, T. (1999) J. Biol. Chem. 274, 36693-36699). VacA causes vacuolation of G401 cells, a human kidney tumor cell line, although they do not express RPTP beta. By co-immunoprecipitation with VacA, we identified p140 as a potential receptor in those cells. p140 purified by chromatography on a peanut agglutinin affinity matrix contained internal amino acid sequences of RGEENTDYVNASFIDGYRQK and AEGILDVFQTVK, which are identical to those in RPTP alpha. The peptide mass fingerprinting of p140 by time of flight-MS analysis also supported this identification. Treatment of G401 cells with RPTP alpha-morpholino antisense oligonucleotide before exposure to toxin inhibited vacuolation. These data suggest that RPTP alpha acts as a receptor for VacA in G401 cells. Thus, two receptor tyrosine phosphatases, RPTP alpha and RPTP beta, serve as VacA receptors.
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Affiliation(s)
- Kinnosuke Yahiro
- Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki 8528523, Japan
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46
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Fujikawa A, Shirasaka D, Yamamoto S, Ota H, Yahiro K, Fukada M, Shintani T, Wada A, Aoyama N, Hirayama T, Fukamachi H, Noda M. Mice deficient in protein tyrosine phosphatase receptor type Z are resistant to gastric ulcer induction by VacA of Helicobacter pylori. Nat Genet 2003; 33:375-81. [PMID: 12598897 DOI: 10.1038/ng1112] [Citation(s) in RCA: 185] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2002] [Accepted: 01/22/2003] [Indexed: 12/14/2022]
Abstract
The vacuolating cytotoxin VacA produced by Helicobacter pylori causes massive cellular vacuolation in vitro and gastric tissue damage in vivo, leading to gastric ulcers, when administered intragastrically. Here we report that mice deficient in protein tyrosine phosphatase receptor type Z (Ptprz, also called PTP-zeta or RPTP-beta, encoded by Ptprz) do not show mucosal damage by VacA, although VacA is incorporated into the gastric epithelial cells to the same extent as in wild-type mice. Primary cultures of gastric epithelial cells from Ptprz+/+ and Ptprz-/- mice also showed similar incorporation of VacA, cellular vacuolation and reduction in cellular proliferation, but only Ptprz+/+ cells showed marked detachment from a reconstituted basement membrane 24 h after treatment with VacA. VacA bound to Ptprz, and the levels of tyrosine phosphorylation of the G protein-coupled receptor kinase-interactor 1 (Git1), a Ptprz substrate, were higher after treatment with VacA, indicating that VacA behaves as a ligand for Ptprz. Furthermore, pleiotrophin (PTN), an endogenous ligand of Ptprz, also induced gastritis specifically in Ptprz+/+ mice when administered orally. Taken together, these data indicate that erroneous Ptprz signaling induces gastric ulcers.
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Affiliation(s)
- Akihiro Fujikawa
- Division of Molecular Neurobiology, National Institute for Basic Biology, 38 Nishigonaka, Myodaiji-cho, Okazaki 444-8585, Japan
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Shirasaka D, Aoyama N, Sakashita M, Kuroda K, Maekawa S, Wambura CM, Miyamoto M, Tamura T, Yahiro K, Wada A, Kurazono H, Hirayama T, Kasuga M. Relationship between gastric ulcer and Helicobacter pylori VacA detected in gastric juice using bead-ELISA method. Helicobacter 2002; 7:281-6. [PMID: 12390207 DOI: 10.1046/j.1523-5378.2002.00097.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND VacA is an important pathogenetic factor produced by Helicobacter pylori. VacA has often been detected in supernatants of liquid cultures or lysates of whole bacterial cells. However, no studies have ever tried to assay VacA produced in the human stomach. We applied a very sensitive and simple method, bead-ELISA, to detect VacA in gastric juice. MATERIALS AND METHODS Forty-eight H. pylori-positive patients (16 nonulcer dyspepsia, 16 gastric ulcer, and 16 duodenal ulcer) and four H. pylori-negative nonulcer dyspepsia patients had endoscopy performed and gastric juice were aspirated. Polystyrene beads coated with the antibody to VacA, were used in this bead-ELISA method. The nucleotide sequences of vacA in the signal and middle regions were investigated. RESULTS Of the 48 samples that were positive for H. pylori, 21 [43.8%] were found to be VacA positive in gastric juice. The average and maximum concentrations of detected VacA in gastric juice were 143.2 +/- 216.5 and 840 pg/ml, respectively. The average density of VacA from gastric ulcer patients (227.5 +/- 276.7 pg/ml) was higher than that found in nonulcer dyspepsia (51.8 +/- 39.8 pg/ml) and duodenal ulcer (49.2 +/- 21.5 pg/ml) patients. There was no relationship between VacA in gastric juice and vacA genotype. CONCLUSIONS VacA in gastric juice could be directly detected by bead-ELISA. In this study, the diversity of disease outcome was associated with not the quality but the quantity of VacA. Therefore, not only the quality but also the quantity of VacA is important etiological factors in the pathogenesis of mucosal damage.
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Affiliation(s)
- Daisuke Shirasaka
- Division of Diabetes, Digestive, and Kidney Disease, Department of Clinical Molecular Medicine, Kobe University School of Medicine, Kobe, Hyogo, Japan
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Patel HK, Willhite DC, Patel RM, Ye D, Williams CL, Torres EM, Marty KB, MacDonald RA, Blanke SR. Plasma membrane cholesterol modulates cellular vacuolation induced by the Helicobacter pylori vacuolating cytotoxin. Infect Immun 2002; 70:4112-23. [PMID: 12117919 PMCID: PMC128184 DOI: 10.1128/iai.70.8.4112-4123.2002] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The Helicobacter pylori vacuolating cytotoxin (VacA) induces the degenerative vacuolation of mammalian cells both in vitro and in vivo. Here, we demonstrate that plasma membrane cholesterol is essential for vacuolation of mammalian cells by VacA. Vacuole biogenesis in multiple cell lines was completely blocked when cholesterol was extracted selectively from the plasma membrane by using beta-cyclodextrins. Moreover, increasing plasma membrane cholesterol levels strongly potentiated VacA-induced vacuolation. In contrast, inhibiting de novo biosynthesis of cholesterol with lovastatin or compactin had no detectable effect on vacuolation. While depletion of plasma membrane cholesterol has been shown to interfere with both clathrin-mediated endocytosis and caveola-dependent endocytosis, neither of these two internalization pathways was found to be essential for vacuolation of cells by VacA. Depleting plasma membrane cholesterol attenuated the entry of VacA into HeLa cells. In addition, beta-cyclodextrin reagents blocked vacuolation of cells that were either preloaded with VacA or had VacA directly expressed within the cytosol. Collectively, our results suggest that plasma membrane cholesterol is important for both the intoxication mechanism of VacA and subsequent vacuole biogenesis.
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Affiliation(s)
- Hetal K Patel
- Department of Biology and Biochemistry, University of Houston, Texas 77204-5001, USA
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Tombola F, Pagliaccia C, Campello S, Telford JL, Montecucco C, Papini E, Zoratti M. How the loop and middle regions influence the properties of Helicobacter pylori VacA channels. Biophys J 2001; 81:3204-15. [PMID: 11720986 PMCID: PMC1301780 DOI: 10.1016/s0006-3495(01)75956-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
VacA is a pore-forming cytotoxin produced by Helicobacter pylori in several strain-specific isoforms, which have been classified in two main families, m1 and m2, according to the sequence of a variable "midregion." Both forms are associated with gastric pathologies and can induce vacuolation of cultured cells. The comparison of two representative toxins, m1 17874 and m2 9554, has indicated that the m2 form is less powerful in vacuolation assays and that its effects are more strongly cell type dependent. To rationalize these differences and to investigate structure-function relationships in this toxin, we have compared the properties of the channels formed by these two variants and by a construct derived from 17874 by deleting a loop that connects the two toxin domains, which is shorter in 9554 than in 17874. Although the channels formed by all three proteins are similar, m2 9554 channels have, on average, a lower conductance and are less anion-selective and more voltage-dependent than the m1 pores. Furthermore, the rate of incorporation of 9554 VacA into planar bilayers depends on lipid composition much more strongly than that of 17874. The comparison with the behavior of the loop deletion mutant indicates that this latter property, as well as a portion of the conductance decrease, may be attributed to the reduction in loop length. The differences in pore properties are proposed to account in part for the different cytotoxicity exhibited by the two toxin isoforms. We furthermore present evidence suggesting that the conformation of the membrane-embedded toxin may be influenced by the lipid composition of the membrane itself.
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Affiliation(s)
- F Tombola
- Centro Biomembrane del Consiglia Nazionale delle Ricerche and Dipartimento di Scienze Biomediche, Università di Padova, Italy
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