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Wang S, Ballard TE, Christopher LJ, Foti RS, Gu C, Khojasteh SC, Liu J, Ma S, Ma B, Obach RS, Schadt S, Zhang Z, Zhang D. The Importance of Tracking "Missing" Metabolites: How and Why? J Med Chem 2023; 66:15586-15612. [PMID: 37769129 DOI: 10.1021/acs.jmedchem.3c01293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2023]
Abstract
Technologies currently employed to find and identify drug metabolites in complex biological matrices generally yield results that offer a comprehensive picture of the drug metabolite profile. However, drug metabolites can be missed or are captured only late in the drug development process. This could be due to a variety of factors, such as metabolism that results in partial loss of the molecule, covalent bonding to macromolecules, the drug being metabolized in specific human tissues, or poor ionization in a mass spectrometer. These scenarios often draw a great deal of attention from chemistry, safety assessment, and pharmacology. This review will summarize scenarios of missing metabolites, why they are missing, and associated uncovering strategies from deeper investigations. Uncovering previously missed metabolites can have ramifications in drug development with toxicological and pharmacological consequences, and knowledge of these can help in the design of new drugs.
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Affiliation(s)
- Shuai Wang
- Department of Drug Metabolism and Pharmacokinetics, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - T Eric Ballard
- Takeda Development Center Americas, Inc., 35 Landsdowne St, Cambridge, Massachusetts 02139, United States
| | - Lisa J Christopher
- Department of Clinical Pharmacology, Pharmacometrics, Disposition & Bioanalysis, Bristol-Myers Squibb, Route 206 & Province Line Road, Princeton, New Jersey 08543, United States
| | - Robert S Foti
- Preclinical Development, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115, United States
| | - Chungang Gu
- Drug Metabolism and Pharmacokinetics, Biogen Inc., 225 Binney Street, Cambridge, Massachusetts 02142, United States
| | - S Cyrus Khojasteh
- Department of Drug Metabolism and Pharmacokinetics, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Joyce Liu
- Department of Drug Metabolism and Pharmacokinetics, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Shuguang Ma
- Drug Metabolism and Pharmacokinetics, Pliant Therapeutics, 260 Littlefield Avenue, South San Francisco, California 94080, United States
| | - Bin Ma
- Department of Drug Metabolism and Pharmacokinetics, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - R Scott Obach
- Pharmacokinetics, Dynamics, and Metabolism, Pfizer, Inc., Eastern Point Road, Groton, Connecticut 06340, United States
| | - Simone Schadt
- Roche Pharma Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacher Strasse 124, 4070 Basel, Switzerland
| | - Zhoupeng Zhang
- DMPK Oncology R&D, AstraZeneca, 35 Gatehouse Drive, Waltham, Massachusetts 02451, United States
| | - Donglu Zhang
- Department of Drug Metabolism and Pharmacokinetics, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
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Koyyada A. Long-term use of proton pump inhibitors as a risk factor for various adverse manifestations. Therapie 2020; 76:13-21. [PMID: 32718584 DOI: 10.1016/j.therap.2020.06.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 06/16/2020] [Accepted: 06/16/2020] [Indexed: 02/07/2023]
Abstract
The long-term use of proton pump inhibitors (PPIs) can lead to increased gastric pH, hypochlorhydria and in some cases to achlorhydria when compared to other acid-suppressing agents like histamine-2 (H2) receptor blockers and antacids. These consequences by the use of long-term PPIs may lead to significant vitamin (B12 and C) and mineral (iron, calcium and magnesium) deficiencies which needs gastric acid for their absorption and bioavailability. Long-term use of PPIs by the pregnant patients may impose a potential risk of congenital malformations. Various studies have recommended the life style modifications and antacid use as first choice among pregnant womens by preserving PPIs (omeprazole as a safe choice of PPI) for severe conditions of gastroesophageal reflux disease. The long-term acid suppression by PPIs can also lead to enteric, respiratory and urinary tract infections. The hypochlorhydria by chronic PPIs use may induce hypergastrinemia, which ultimately mediates the gastric polyps, gastric carcinoids and gastric cancer. The concomitant use of PPIs with antiplatelet drugs like clopidogrel can impose the patients to major adverse cardiac events. This review has enlisted the comprehensive information regarding the adverse effects induced by long-term use of PPIs and their possible relations. Considerable studies like case-control, randomized trials, cohort studies and meta-analysis were reported in supporting these adverse effects. The clinicians and patients should be cautious about these effects so that they can avoid the serious outcomes. PPIs should be avoided for long-term use mainly in older adults unless there is a proper indication.
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Affiliation(s)
- Arun Koyyada
- GITAM Institute of Pharmacy, GITAM University, Rushikonda, Visakhapatnam, 530045 Andhra Pradesh, India.
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3
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Engevik AC, Kaji I, Goldenring JR. The Physiology of the Gastric Parietal Cell. Physiol Rev 2020; 100:573-602. [PMID: 31670611 PMCID: PMC7327232 DOI: 10.1152/physrev.00016.2019] [Citation(s) in RCA: 101] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 10/10/2019] [Accepted: 10/13/2019] [Indexed: 12/11/2022] Open
Abstract
Parietal cells are responsible for gastric acid secretion, which aids in the digestion of food, absorption of minerals, and control of harmful bacteria. However, a fine balance of activators and inhibitors of parietal cell-mediated acid secretion is required to ensure proper digestion of food, while preventing damage to the gastric and duodenal mucosa. As a result, parietal cell secretion is highly regulated through numerous mechanisms including the vagus nerve, gastrin, histamine, ghrelin, somatostatin, glucagon-like peptide 1, and other agonists and antagonists. The tight regulation of parietal cells ensures the proper secretion of HCl. The H+-K+-ATPase enzyme expressed in parietal cells regulates the exchange of cytoplasmic H+ for extracellular K+. The H+ secreted into the gastric lumen by the H+-K+-ATPase combines with luminal Cl- to form gastric acid, HCl. Inhibition of the H+-K+-ATPase is the most efficacious method of preventing harmful gastric acid secretion. Proton pump inhibitors and potassium competitive acid blockers are widely used therapeutically to inhibit acid secretion. Stimulated delivery of the H+-K+-ATPase to the parietal cell apical surface requires the fusion of intracellular tubulovesicles with the overlying secretory canaliculus, a process that represents the most prominent example of apical membrane recycling. In addition to their unique ability to secrete gastric acid, parietal cells also play an important role in gastric mucosal homeostasis through the secretion of multiple growth factor molecules. The gastric parietal cell therefore plays multiple roles in gastric secretion and protection as well as coordination of physiological repair.
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Affiliation(s)
- Amy C Engevik
- Departments of Surgery and of Cell and Developmental Biology and the Epithelial Biology Center, Vanderbilt University School of Medicine, Vanderbilt University Medical Center and the Nashville VA Medical Center, Nashville, Tennessee
| | - Izumi Kaji
- Departments of Surgery and of Cell and Developmental Biology and the Epithelial Biology Center, Vanderbilt University School of Medicine, Vanderbilt University Medical Center and the Nashville VA Medical Center, Nashville, Tennessee
| | - James R Goldenring
- Departments of Surgery and of Cell and Developmental Biology and the Epithelial Biology Center, Vanderbilt University School of Medicine, Vanderbilt University Medical Center and the Nashville VA Medical Center, Nashville, Tennessee
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4
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Chen WL, Li DD, Chen X, Wang YZ, Xu JJ, Jiang ZY, You QD, Guo XK. Proton pump inhibitors selectively suppress MLL rearranged leukemia cells via disrupting MLL1-WDR5 protein-protein interaction. Eur J Med Chem 2019; 188:112027. [PMID: 31923859 DOI: 10.1016/j.ejmech.2019.112027] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 12/07/2019] [Accepted: 12/29/2019] [Indexed: 12/12/2022]
Abstract
Genetic rearrangements of the mixed lineage leukemia (MLL) leading to oncogenic MLL-fusion proteins (MLL-FPs). MLL-FPs occur in about 10% of acute leukemias and are associated with dismal prognosis and treatment outcomes which emphasized the need for new therapeutic strategies. In present study, by a cell-based screening in-house compound collection, we disclosed that Rabeprazole specially inhibited the proliferation of leukemia cells harboring MLL-FPs with little toxicity to non-MLL cells. Mechanism study showed Rabeprazole down-regulated the transcription of MLL-FPs related Hox and Meis1 genes and effectively inhibited MLL1 H3K4 methyltransferase (HMT) activity in MV4-11 cells bearing MLL-AF4 fusion protein. Displacement of MLL1 probe from WDR5 protein suggested that Rabeprazole may inhibit MLL1 HMT activity through disturbing MLL1-WDR5 protein-protein interaction. Moreover, other proton pump inhibitors (PPIs) also indicated the inhibition activity of MLL1-WDR5. Preliminary SARs showed the structural characteristics of PPIs were also essential for the activities of MLL1-WDR5 inhibition. Our results indicated the drug reposition of PPIs for MLL-rearranged leukemias and provided new insight for further optimization of targeting MLL1 methyltransferase activity, the MLL1-WDR5 interaction or WDR5.
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Affiliation(s)
- Wei-Lin Chen
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China; Department of Medicinal Chemistry, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Dong-Dong Li
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China
| | - Xin Chen
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China
| | - Ying-Zhe Wang
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China
| | - Jun-Jie Xu
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China
| | - Zheng-Yu Jiang
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China; Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, 210009, China.
| | - Qi-Dong You
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China; Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, 210009, China.
| | - Xiao-Ke Guo
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, 210009, China; Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, 210009, China.
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5
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Chaikuad A, Koch P, Laufer SA, Knapp S. The Cysteinome of Protein Kinases as a Target in Drug Development. Angew Chem Int Ed Engl 2018; 57:4372-4385. [DOI: 10.1002/anie.201707875] [Citation(s) in RCA: 136] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/20/2017] [Indexed: 01/04/2023]
Affiliation(s)
- Apirat Chaikuad
- Nuffield Department of Clinical Medicine; Structural Genomics Consortium and Target Discovery Institute; University of Oxford, Old Road Campus Research Building; Roosevelt Drive Oxford OX3 7DQ UK
- Institute for Pharmaceutical Chemistry; Goethe-University; Max-von-Laue-Strasse 9 60438 Frankfurt am Main Germany
| | - Pierre Koch
- Department of Pharmaceutical/Medicinal Chemistry; Eberhard-Karls-University Tübingen; Auf der Morgenstelle 8 72076 Tübingen Germany
| | - Stefan A. Laufer
- Department of Pharmaceutical/Medicinal Chemistry; Eberhard-Karls-University Tübingen; Auf der Morgenstelle 8 72076 Tübingen Germany
- German Cancer Consortium DKTK, Standort Tübingen; Germany
| | - Stefan Knapp
- Nuffield Department of Clinical Medicine; Structural Genomics Consortium and Target Discovery Institute; University of Oxford, Old Road Campus Research Building; Roosevelt Drive Oxford OX3 7DQ UK
- German Cancer Consortium DKTK, Standort Frankfurt/Mainz; Germany
- Institute for Pharmaceutical Chemistry; Goethe-University; Max-von-Laue-Strasse 9 60438 Frankfurt am Main Germany
- Structural Genomics Consortium and Buchmann Institute for Molecular Life Sciences; Johann Wolfgang Goethe-University; Max-von-Laue-Strasse 15 60438 Frankfurt am Main Germany
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6
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Chaikuad A, Koch P, Laufer SA, Knapp S. Das Cysteinom der Proteinkinasen als Zielstruktur in der Arzneistoffentwicklung. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201707875] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Apirat Chaikuad
- Nuffield Department of Clinical Medicine; Structural Genomics Consortium and Target Discovery Institute; Universität Oxford, Old Road Campus Research Building; Roosevelt Drive Oxford OX3 7DQ Großbritannien
- Institut für pharmazeutische Chemie; Johann Wolfgang Goethe-Universität; Max-von-Laue-Straße 9 60438 Frankfurt am Main Deutschland
| | - Pierre Koch
- Institut für pharmazeutische und medizinische Chemie; Eberhard-Karls-Universität Tübingen; Auf der Morgenstelle 8 72076 Tübingen Deutschland
| | - Stefan A. Laufer
- Institut für pharmazeutische und medizinische Chemie; Eberhard-Karls-Universität Tübingen; Auf der Morgenstelle 8 72076 Tübingen Deutschland
- Deutsches Zentrum für translationale Krebsforschung, Standort; Tübingen Deutschland
| | - Stefan Knapp
- Nuffield Department of Clinical Medicine; Structural Genomics Consortium and Target Discovery Institute; Universität Oxford, Old Road Campus Research Building; Roosevelt Drive Oxford OX3 7DQ Großbritannien
- Deutsches Zentrum für translationale Krebsforschung, Standort Frankfurt/Mainz; Deutschland
- Institut für pharmazeutische Chemie; Johann Wolfgang Goethe-Universität; Max-von-Laue-Straße 9 60438 Frankfurt am Main Deutschland
- Structural Genomics Consortium and Buchmann Institute for Molecular Life Sciences; Johann Wolfgang Goethe-Universität; Max-von-Laue-Straße 15 60438 Frankfurt am Main Deutschland
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7
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Paresi CJ, Liu Q, Li YM. Benzimidazole covalent probes and the gastric H(+)/K(+)-ATPase as a model system for protein labeling in a copper-free setting. MOLECULAR BIOSYSTEMS 2017; 12:1772-80. [PMID: 26952080 DOI: 10.1039/c6mb00024j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Affinity probes are useful tools for determining molecular targets and elucidating mechanism of action for novel, bioactive compounds. In the case of covalent inhibitors, activity based probes are particularly valuable for ensuring acceptable selectivity margins. However, there is a variety of bioorthogonal chemistry reactions available for modifying compounds of interest with clickable tags. Here, we describe a direct comparison of tetrazine ligation and strain promoted azide-alkyne cycloaddition using benzimidazole based probes to bind their known target, the gastric proton pump, ATP4A. This study validates the use of chemical probes for target identification and illustrates the superior efficiency of tetrazine ligation for copper-free click systems. In addition, we have identified several novel binding partners of benzimidazole probes: Isoform 2 of deleted in malignant brain tumors 1 protein (DMBT1) and three uncharacterized proteins.
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Affiliation(s)
- Chelsea J Paresi
- Chemical Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA. and Program of Pharmacology, Weill Graduate School of Medical Sciences of Cornell University, New York, NY 10021, USA
| | - Qi Liu
- Chemical Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA.
| | - Yue-Ming Li
- Chemical Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA. and Program of Pharmacology, Weill Graduate School of Medical Sciences of Cornell University, New York, NY 10021, USA
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8
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Kitay AM, Geibel JP. Stomach and Bone. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1033:97-131. [DOI: 10.1007/978-3-319-66653-2_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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9
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Inatomi N, Matsukawa J, Sakurai Y, Otake K. Potassium-competitive acid blockers: Advanced therapeutic option for acid-related diseases. Pharmacol Ther 2016; 168:12-22. [PMID: 27514776 DOI: 10.1016/j.pharmthera.2016.08.001] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 07/29/2016] [Indexed: 02/07/2023]
Abstract
Acid-related diseases (ARDs), such as peptic ulcers and gastroesophageal reflux disease, represent a major health-care concern. Some major milestones in our understanding of gastric acid secretion and ARD treatment reached during the last 50years include 1) discovery of histamine H2-receptors and development of H2-receptor antagonists, 2) identification of H+,K+-ATPase as the parietal cell proton pump and development of proton pump inhibitors (PPIs), and 3) identification of Helicobacter pylori (H. pylori) as the major cause of peptic ulcers and development of effective eradication regimens. Although PPI treatments have been effective and successful, there are limitations to their efficacy and usage, i.e. short half-life, insufficient acid suppression, slow onset of action, and large variation in efficacy among patients due to CYP2C19 metabolism. Potassium-competitive acid blockers (P-CABs) inhibit H+,K+-ATPase in a reversible and K+-competitive manner, and exhibit almost complete inhibition of gastric acid secretion from the first dose. Many pharmaceutical companies have tried to develop P-CABs, but most of their clinical development has been discontinued due to safety concerns or a similar efficacy to PPIs. Revaprazan was developed in Korea and was the first P-CAB approved for sale. Vonoprazan, approved in 2014 in Japan, has a completely different chemical structure and higher pKa value compared to other P-CABs, and exhibits rapid onset of action and prolonged control of intragastric acidity. Vonoprazan is an effective treatment for ARDs that is especially effective in healing reflux esophagitis and for H. pylori eradication. P-CABs, such as vonoprazan, promise to further improve the management of ARDs.
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Affiliation(s)
- Nobuhiro Inatomi
- Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Kanagawa 251-8555, Japan
| | - Jun Matsukawa
- Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Fujisawa, Kanagawa 251-8555, Japan.
| | - Yuuichi Sakurai
- Japan Development Center, Takeda Pharmaceutical Company Limited, Chuo-ku, Osaka 540-8645, Japan
| | - Kazuyoshi Otake
- Global Medical Affairs Japan Department, Takeda Pharmaceutical Company Limited, Chuo-ku, Tokyo 103-8668, Japan
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Thabet R, Rouault JD, Ayadi H, Leignel V. Structural analysis of the α subunit of Na(+)/K(+) ATPase genes in invertebrates. Comp Biochem Physiol B Biochem Mol Biol 2016; 196-197:11-18. [PMID: 26812300 DOI: 10.1016/j.cbpb.2016.01.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Revised: 01/20/2016] [Accepted: 01/21/2016] [Indexed: 01/18/2023]
Abstract
The Na(+)/K(+) ATPase is a ubiquitous pump coordinating the transport of Na(+) and K(+) across the membrane of cells and its role is fundamental to cellular functions. It is heteromer in eukaryotes including two or three subunits (α, β and γ which is specific to the vertebrates). The catalytic functions of the enzyme have been attributed to the α subunit. Several complete α protein sequences are available, but only few gene structures were characterized. We identified the genomic sequences coding the α-subunit of the Na(+)/K(+) ATPase, from the whole-genome shotgun contigs (WGS), NCBI Genomes (chromosome), Genomic Survey Sequences (GSS) and High Throughput Genomic Sequences (HTGS) databases across distinct phyla. One copy of the α subunit gene was found in Annelida, Arthropoda, Cnidaria, Echinodermata, Hemichordata, Mollusca, Placozoa, Porifera, Platyhelminthes, Urochordata, but the nematodes seem to possess 2 to 4 copies. The number of introns varied from 0 (Platyhelminthes) to 26 (Porifera); and their localization and length are also highly variable. Molecular phylogenies (Maximum Likelihood and Maximum Parsimony methods) showed some clusters constituted by (Chordata/(Echinodermata/Hemichordata)) or (Plathelminthes/(Annelida/Mollusca)) and a basal position for Porifera. These structural analyses increase our knowledge about the evolutionary events of the α subunit genes in the invertebrates.
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Affiliation(s)
- Rahma Thabet
- University of Sfax, Laboratory of Biodiversity and Aquatic Ecosystems UR/11ES72, Ecology and Planktonology, Department of Life Sciences, Road Soukra Km 3.5, BP1171, 3000, Sfax, Tunisia
| | - J-D Rouault
- Laboratoire Evolution, Genomes et Speciation, UPR9034, CNRS, 91198 Gif-sur-Yvette, France
| | - Habib Ayadi
- University of Sfax, Laboratory of Biodiversity and Aquatic Ecosystems UR/11ES72, Ecology and Planktonology, Department of Life Sciences, Road Soukra Km 3.5, BP1171, 3000, Sfax, Tunisia
| | - Vincent Leignel
- Université du Maine, Laboratoire Mer Molecule Sante EA 2160 FR-CNRS 3473 IUML, 72085 Le Mans, France.
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11
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González-Bello C. Designing Irreversible Inhibitors-Worth the Effort? ChemMedChem 2015; 11:22-30. [DOI: 10.1002/cmdc.201500469] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Indexed: 12/29/2022]
Affiliation(s)
- Concepción González-Bello
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS); Universidade de Santiago de Compostela; calle Jenaro de la Fuente s/n Santiago de Compostela 15782 Spain
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12
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Proton pump inhibitors drastically modify triosephosphate isomerase from Giardia lamblia at functional and structural levels, providing molecular leads in the design of new antigiardiasic drugs. Biochim Biophys Acta Gen Subj 2015; 1860:97-107. [PMID: 26518348 DOI: 10.1016/j.bbagen.2015.10.021] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 10/09/2015] [Accepted: 10/23/2015] [Indexed: 01/23/2023]
Abstract
BACKGROUND Proton pump inhibitors (PPIs) are extensively used in clinical practice because of their effectiveness and safety. Omeprazole is one of the best-selling drugs worldwide and, with other PPIs, has been proposed to be potential drugs for the treatment of several diseases. We demonstrated that omeprazole shows cytotoxic effects in Giardia and concomitantly inactivates giardial triosephosphate isomerase (GlTIM). Therefore, we evaluated the efficiency of commercially available PPIs to inactivate this enzyme. METHODS We assayed the effect of PPIs on the GlTIM WT, single Cys mutants, and the human counterpart, following enzyme activity, thermal stability, exposure of hydrophobic regions, and susceptibility to limited proteolysis. RESULTS PPIs efficiently inactivated GlTIM; however, rabeprazole was the best inactivating drug and was nearly ten times more effective. The mechanism of inactivation by PPIs was through the modification of the Cys 222 residue. Moreover, there are important changes at the structural level, the thermal stability of inactivated-GlTIM was drastically diminished and the structural rigidity was lost, as observed by the exposure of hydrophobic regions and their susceptibility to limited proteolysis. CONCLUSIONS Our results demonstrate that rabeprazole is the most potent PPI for GlTIM inactivation and that all PPIs tested have substantial abilities to alter GITIM at the structural level, causing serious damage. GENERAL SIGNIFICANCE This is the first report demonstrating the effectiveness of commercial PPIs on a glycolytic parasitic enzyme, with structural features well known. This study is a step forward in the use and understanding the implicated mechanisms of new antigiardiasic drugs safe in humans.
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Ross EM, Bourges D, Hogan TV, Gleeson PA, van Driel IR. Helios defines T cells being driven to tolerance in the periphery and thymus. Eur J Immunol 2014; 44:2048-58. [PMID: 24740292 DOI: 10.1002/eji.201343999] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 03/04/2014] [Accepted: 04/11/2014] [Indexed: 01/04/2023]
Abstract
The expression of the Ikaros transcription factor family member, Helios, has been shown to be associated with T-cell tolerance in both the thymus and the periphery. To better understand the importance of Helios in tolerance pathways, we have examined the expression of Helios in TCR-transgenic T cells specific for the gastric H(+) /K(+) ATPase, the autoantigen target in autoimmune gastritis. Analysis of H(+) /K(+) ATPase-specific T cells in mice with different patterns of H(+) /K(+) ATPase expression revealed that, in addition to the expression of Helios in CD4(+) Foxp3(+) regulatory T (Treg) cells, Helios is expressed by a large proportion of CD4(+) Foxp3(-) T cells in both the thymus and the paragastric lymph node (PgLN), which drains the stomach. In the thymus, Helios was expressed by H(+) /K(+) ATPase-specific thymocytes that were undergoing negative selection. In the periphery, Helios was expressed in H(+) /K(+) ATPase-specific CD4(+) T cells following H(+) /K(+) ATPase presentation and was more highly expressed when T-cell activation occurred in the absence of inflammation. Analysis of purified H(+) /K(+) ATPase-specific CD4(+) Foxp3(-) Helios(+) T cells demonstrated that they were functionally anergic. These results demonstrate that Helios is expressed by thymic and peripheral T cells that are being driven to tolerance in response to a genuine autoantigen.
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Affiliation(s)
- Ellen M Ross
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, Australia
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14
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Zhang S, Wang Y, Li SJ. Lansoprazole induces apoptosis of breast cancer cells through inhibition of intracellular proton extrusion. Biochem Biophys Res Commun 2014; 448:424-9. [PMID: 24802401 DOI: 10.1016/j.bbrc.2014.04.127] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Accepted: 04/24/2014] [Indexed: 11/29/2022]
Abstract
The increased glycolysis and proton secretion in tumors is proposed to contribute to the proliferation and invasion of cancer cells during the process of tumorigenesis and metastasis. Here, treatment of human breast cancer cells with proton pump inhibitor (PPI) lansoprazole (LPZ) induces cell apoptosis in a dose-dependent manner. In the implantation of the MDA-MB-231 xenografts in nude mice, administration of LPZ significantly inhibits tumorigenesis and induces large-scale apopotosis of tumor cells. LPZ markedly inhibits intracellular proton extrusion, induces an increase in intracellular ATP level, lysosomal alkalinization and accumulation of reactive oxygen species (ROS) in breast cancer cells. The ROS scavenger N-acetyl-l-cysteine (NAC) and diphenyleneiodonium (DPI), a specific pharmacological inhibitor of NADPH oxidases (NOX), significantly abolish LPZ-induced ROS accumulation in breast cancer cells. Our results suggested that LPZ may be used as a new therapeutic drug for breast tumor.
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Affiliation(s)
- Shangrong Zhang
- Department of Biophysics, School of Physics Science, The Key Laboratory of Bioactive Materials, Ministry of Education, Nankai University, Tianjin 300071, PR China
| | - Yifan Wang
- Department of Biophysics, School of Physics Science, The Key Laboratory of Bioactive Materials, Ministry of Education, Nankai University, Tianjin 300071, PR China
| | - Shu Jie Li
- Department of Biophysics, School of Physics Science, The Key Laboratory of Bioactive Materials, Ministry of Education, Nankai University, Tianjin 300071, PR China.
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Abstract
The gastric H(+),K(+)-ATPase is responsible for gastric acid secretion. This ATPase is composed of two subunits, the catalytic α subunit and the structural β subunit. The α subunit with molecular mass of about 100 kDa has 10 transmembrane domains and is strongly associated with the β subunit with a single transmembrane segment and a peptide mass of 35 kDa. Its three-dimensional structure is based on homology modeling and site-directed mutagenesis resulting in a proton extrusion and K(+) reabsorption model. There are three conserved H3O(+)-binding sites in the middle of the membrane domain and H3O(+) secretion depends on a conformational change involving Lys(791) insertion into the second H3O(+) site enclosed by E795, E820, and D824 that allows export of protons at a concentration of 160 mM. K(+) countertransport involves binding to this site after the release of protons with retrograde displacement of Lys(791) and then K(+) transfer to E343 and exit to the cytoplasm. This ATPase is the major therapeutic target in treatment of acid-related diseases and there are several known luminal inhibitors allowing analysis of the luminal vestibule. One class contains the acid-activated covalent, thiophilic proton pump inhibitors, the most effective of current acid-suppressive drugs. Their binding sites and trypsinolysis allowed identification of all ten transmembrane segments of the ATPase. In addition, various K(+)-competitive inhibitors of the ATPase are being developed, with the advantage of complete and rapid inhibition of acid secretion independent of pump activity and allowing further refinement of the structure of the luminal vestibule of the E2 form of this ATPase.
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Affiliation(s)
- Jai Moo Shin
- Department of Physiology and Medicine, University of California at Los Angeles, and VA Greater Los Angeles Healthcare System, Los Angeles, California, USA.
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Kopic S, Geibel JP. Gastric acid, calcium absorption, and their impact on bone health. Physiol Rev 2013; 93:189-268. [PMID: 23303909 DOI: 10.1152/physrev.00015.2012] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Calcium balance is essential for a multitude of physiological processes, ranging from cell signaling to maintenance of bone health. Adequate intestinal absorption of calcium is a major factor for maintaining systemic calcium homeostasis. Recent observations indicate that a reduction of gastric acidity may impair effective calcium uptake through the intestine. This article reviews the physiology of gastric acid secretion, intestinal calcium absorption, and their respective neuroendocrine regulation and explores the physiological basis of a potential link between these individual systems.
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Affiliation(s)
- Sascha Kopic
- Department of Surgery and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut, USA
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Shin JM, Kim N. Pharmacokinetics and pharmacodynamics of the proton pump inhibitors. J Neurogastroenterol Motil 2013; 19:25-35. [PMID: 23350044 PMCID: PMC3548122 DOI: 10.5056/jnm.2013.19.1.25] [Citation(s) in RCA: 251] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 12/20/2012] [Accepted: 12/21/2012] [Indexed: 12/13/2022] Open
Abstract
Proton pump inhibitor (PPI) is a prodrug which is activated by acid. Activated PPI binds covalently to the gastric H+, K+-ATPase via disulfide bond. Cys813 is the primary site responsible for the inhibition of acid pump enzyme, where PPIs bind. Omeprazole was the first PPI introduced in market, followed by pantoprazole, lansoprazole and rabeprazole. Though these PPIs share the core structures benzimidazole and pyridine, their pharmacokinetics and pharmacodynamics are a little different. Several factors must be considered in understanding the pharmacodynamics of PPIs, including: accumulation of PPI in the parietal cell, the proportion of the pump enzyme located at the canaliculus, de novo synthesis of new pump enzyme, metabolism of PPI, amounts of covalent binding of PPI in the parietal cell, and the stability of PPI binding. PPIs have about 1hour of elimination half-life. Area under the plasmic concentration curve and the intragastric pH profile are very good indicators for evaluating PPI efficacy. Though CYP2C19 and CYP3A4 polymorphism are major components of PPI metabolism, the pharmacokinetics and pharmacodynamics of racemic mixture of PPIs depend on the CYP2C19 genotype status. S-omeprazole is relatively insensitive to CYP2C19, so better control of the intragastric pH is achieved. Similarly, R-lansoprazole was developed in order to increase the drug activity. Delayed-release formulation resulted in a longer duration of effective concentration of R-lansoprazole in blood, in addition to metabolic advantage. Thus, dexlansoprazole showed best control of the intragastric pH among the present PPIs. Overall, PPIs made significant progress in the management of acid-related diseases and improved health-related quality of life.
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1-Arylsulfonyl-2-(pyridylmethylsulfinyl) benzimidazoles as new proton pump inhibitor prodrugs. Molecules 2009; 14:5247-80. [PMID: 20032890 PMCID: PMC2855619 DOI: 10.3390/molecules14125247] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Revised: 12/08/2009] [Accepted: 12/14/2009] [Indexed: 11/17/2022] Open
Abstract
New arylsulfonyl proton pump inhibitor (PPI) prodrug forms were synthesized. These prodrugs provided longer residence time of an effective PPI plasma concentration, resulting in better gastric acid inhibition.
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Abstract
The gastric H,K-ATPase is the primary target for the treatment of acid-related diseases. Proton pump inhibitors (PPIs) are weak bases composed of two moieties, a substituted pyridine with a primary pK(a) of about 4.0, which allows selective accumulation in the secretory canaliculus of the parietal cell, and a benzimidazole with a second pK(a) of about 1.0. PPIs are acid-activated prodrugs that convert to sulfenic acids or sulfenamides that react covalently with one or more cysteines accessible from the luminal surface of the ATPase. Because of covalent binding, their inhibitory effects last much longer than their plasma half-life. However, the short half-life of the drug in the blood and the requirement for acid activation impair their efficacy in acid suppression, particularly at night. PPIs with longer half-life promise to improve acid suppression. All PPIs give excellent healing of peptic ulcers and produce good results in reflux esophagitis. PPIs combined with antibiotics eradicate Helicobacter pylori.
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Affiliation(s)
- Jai Moo Shin
- Membrane Biology, David Geffen School of Medicine, University of California at Los Angeles, Room 324, Building 113, 11301 Wilshire Boulevard, Los Angeles, CA 90073, USA
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Shin JM, Munson K, Vagin O, Sachs G. The gastric HK-ATPase: structure, function, and inhibition. Pflugers Arch 2008; 457:609-22. [PMID: 18536934 DOI: 10.1007/s00424-008-0495-4] [Citation(s) in RCA: 167] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2008] [Revised: 03/07/2008] [Accepted: 03/11/2008] [Indexed: 02/06/2023]
Abstract
The gastric H,K-ATPase, a member of the P(2)-type ATPase family, is the integral membrane protein responsible for gastric acid secretion. It is an alpha,beta-heterodimeric enzyme that exchanges cytoplasmic hydronium with extracellular potassium. The catalytic alpha subunit has ten transmembrane segments with a cluster of intramembranal carboxylic amino acids located in the middle of the transmembrane segments TM4, TM5,TM6, and TM8. Comparison to the known structure of the SERCA pump, mutagenesis, and molecular modeling has identified these as constituents of the ion binding domain. The beta subunit has one transmembrane segment with N terminus in cytoplasmic region. The extracellular domain of the beta subunit contains six or seven N-linked glycosylation sites. N-glycosylation is important for the enzyme assembly, maturation, and sorting. The enzyme pumps acid by a series of conformational changes from an E(1) (ion site in) to an E(2) (ion site out) configuration following binding of MgATP and phosphorylation. Several experimental observations support the hypothesis that expulsion of the proton at 160 mM (pH 0.8) results from movement of lysine 791 into the ion binding site in the E(2)P configuration. Potassium access from the lumen depends on activation of a K and Cl conductance via a KCNQ1/KCNE2 complex and Clic6. K movement through the luminal channel in E(2)P is proposed to displace the lysine along with dephosphorylation to return the enzyme to the E(1) configuration. This enzyme is inhibited by the unique proton pump inhibitor class of drug, allowing therapy of acid-related diseases.
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Affiliation(s)
- Jai Moo Shin
- Department of Physiology, David Geffen School of Medicine, University of California at Los Angeles and VA Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA
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Shin JM, Vagin O, Munson K, Kidd M, Modlin IM, Sachs G. Molecular mechanisms in therapy of acid-related diseases. Cell Mol Life Sci 2008; 65:264-81. [PMID: 17928953 PMCID: PMC3081136 DOI: 10.1007/s00018-007-7249-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Inhibition of gastric acid secretion is the mainstay of the treatment of gastroesophageal reflux disease and peptic ulceration; therapies to inhibit acid are among the best-selling drugs worldwide. Highly effective agents targeting the histamine H2 receptor were first identified in the 1970s. These were followed by the development of irreversible inhibitors of the parietal cell hydrogen-potassium ATPase (the proton pump inhibitors) that inhibit acid secretion much more effectively. Reviewed here are the chemistry, biological targets and pharmacology of these drugs, with reference to their current and evolving clinical utilities. Future directions in the development of acid inhibitory drugs include modifications of current agents and the emergence of a novel class of agents, the acid pump antagonists.
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Affiliation(s)
- J. M. Shin
- Department of Physiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California USA
- VA Greater Los Angeles Healthcare System, West LA Medical Center, 11301 Wilshire Boulevard, Building 113, Los Angeles, California 90073 USA
| | - O. Vagin
- Department of Physiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California USA
- VA Greater Los Angeles Healthcare System, West LA Medical Center, 11301 Wilshire Boulevard, Building 113, Los Angeles, California 90073 USA
| | - K. Munson
- Department of Physiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California USA
- VA Greater Los Angeles Healthcare System, West LA Medical Center, 11301 Wilshire Boulevard, Building 113, Los Angeles, California 90073 USA
| | - M. Kidd
- Department of Surgery, Yale University School of Medicine, TMP202, 333 Cedar Street, New Haven Connecticut, 06520-8062 USA
| | - I. M. Modlin
- Department of Surgery, Yale University School of Medicine, TMP202, 333 Cedar Street, New Haven Connecticut, 06520-8062 USA
| | - G. Sachs
- Department of Physiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California USA
- VA Greater Los Angeles Healthcare System, West LA Medical Center, 11301 Wilshire Boulevard, Building 113, Los Angeles, California 90073 USA
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Structural analysis of 2D crystals of gastric H+,K+-ATPase in different states of the transport cycle. J Struct Biol 2007; 162:219-28. [PMID: 18276159 DOI: 10.1016/j.jsb.2007.12.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2007] [Revised: 12/18/2007] [Accepted: 12/19/2007] [Indexed: 11/22/2022]
Abstract
The H+,K+-ATPase uses ATP to pump protons across the gastric membrane. We used electron crystallography and limited trypsin proteolysis to study conformational changes in the H+,K+-ATPase. Well-ordered 2D crystals were obtained with detergent-solubilized H+,K+-ATPase at low pH in the absence of nucleotides, E1 state, and in the presence of fluoroaluminate and ADP, mimicking the E1PADP state. Projection maps obtained with frozen-hydrated two-dimensional crystals of the H+,K+-ATPase in these two states looked very similar, suggesting only small conformational changes during the transition from the E1 to the E1P x ADP state. This result differs from the X-ray crystal structures of the related ATPase SERCA, which revealed substantially different conformations in the E1 and E1P x ADP states. To further characterize the conformational changes in the H+,K+-ATPase during its transport cycle, we performed limited proteolysis with trypsin. All examined states of the H+,K+-ATPase, including the E1 and E1P x ADP states present in the 2D crystals,showed characteristic differences in the digestion patterns. While the results from the limited proteolysis experiments thus show that the H+,K+-ATPase adopts distinct conformations during different stages of the transport cycle, the projection maps indicate that the structural rearrangements in the H+,K+-ATPase are much smaller than those observed in the related SERCA ATPase.
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24
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Influence of gastric acid on susceptibility to infection with ingested bacterial pathogens. Infect Immun 2007; 76:639-45. [PMID: 18025100 DOI: 10.1128/iai.01138-07] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Despite the widely held belief that gastric acid serves as a barrier to bacterial pathogens, there are almost no experimental data to support this hypothesis. We have developed a mouse model to quantify the effectiveness of gastric acid in mediating resistance to infection with ingested bacteria. Mice that were constitutively hypochlorhydric due to a mutation in a gastric H(+)/K(+)-ATPase (proton pump) gene were infected with Yersinia enterocolitica, Salmonella enterica serovar Typhimurium, Citrobacter rodentium, or Clostridium perfringens cells or spores. Significantly greater numbers of Yersinia, Salmonella, and Citrobacter cells (P < OR = 0.006) and Clostridium spores (P = 0.02) survived in hypochlorhydric mice, resulting in reduced median infectious doses. Experiments involving intraperitoneal infection or infection of mice treated with antacids indicated that the increased sensitivity of hypochlorhydric mice to infection was entirely due to the absence of stomach acid. Apart from establishing the role of gastric acid in nonspecific immunity to ingested bacterial pathogens, our model provides an excellent system with which to investigate the effects of hypochlorhydria on susceptibility to infection and to evaluate the in vivo susceptibility to gastric acid of orally administered therapies, such as vaccines and probiotics.
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Abstract
Proton pump inhibitors inhibit the gastric H+/K+-ATPase via covalent binding to cysteine residues of the proton pump. All proton pump inhibitors must undergo acid accumulation in the parietal cell through protonation, followed by activation mediated by a second protonation at the active secretory canaliculus of the parietal cell. The relative ease with which these steps occur with different proton pump inhibitors underlies differences in their rates of activation, which in turn influence the location of covalent binding and the stability of inhibition. Slow activation is associated with binding to a cysteine residue involved in proton transport that is located deep in the membrane. However, this is inaccessible to the endogenous reducing agents responsible for restoring H+/K+-ATPase activity, favouring a longer duration of gastric acid inhibition. Pantoprazole and tenatoprazole, a novel proton pump inhibitor which has an imidazopyridine ring in place of the benzimidazole moiety found in other proton pump inhibitors, are activated more slowly than other proton pump inhibitors but their inhibition is resistant to reversal. In addition, tenatoprazole has a greatly extended plasma half-life in comparison with all other proton pump inhibitors. The chemical and pharmacological characteristics of tenatoprazole give it theoretical advantages over benzimidazole-based proton pump inhibitors that should translate into improved acid control, particularly during the night.
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Affiliation(s)
- G Sachs
- Department of Physiology and Medicine, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, USA.
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Affiliation(s)
- Jai Moo Shin
- Department of Physiology and Medicine, University of California at Los Angeles, and VA Greater Los Angeles Healthcare System, Los Angeles, California 90073, USA
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27
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Shin JM, Homerin M, Domagala F, Ficheux H, Sachs G. Characterization of the inhibitory activity of tenatoprazole on the gastric H+,K+ -ATPase in vitro and in vivo. Biochem Pharmacol 2006; 71:837-49. [PMID: 16405921 DOI: 10.1016/j.bcp.2005.11.030] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2005] [Revised: 11/24/2005] [Accepted: 11/28/2005] [Indexed: 01/12/2023]
Abstract
Tenatoprazole is a prodrug of the proton pump inhibitor (PPI) class, which is converted to the active sulfenamide or sulfenic acid by acid in the secretory canaliculus of the stimulated parietal cell of the stomach. This active species binds to luminally accessible cysteines of the gastric H+,K+ -ATPase resulting in disulfide formation and acid secretion inhibition. Tenatoprazole binds at the catalytic subunit of the gastric acid pump with a stoichiometry of 2.6 nmol mg(-1) of the enzyme in vitro. In vivo, maximum binding of tenatoprazole was 2.9 nmol mg(-1) of the enzyme at 2 h after IV administration. The binding sites of tenatoprazole were in the TM5/6 region at Cys813 and Cys822 as shown by tryptic and thermolysin digestion of the ATPase labeled by tenatoprazole. Decay of tenatoprazole binding on the gastric H+,K+ -ATPase consisted of two components. One was relatively fast, with a half-life 3.9 h due to reversal of binding at cysteine 813, and the other was a plateau phase corresponding to ATPase turnover reflecting binding at cysteine 822 that also results in sustained inhibition in the presence of reducing agents in vitro. The stability of inhibition and the long plasma half-life of tenatoprazole should result in prolonged inhibition of acid secretion as compared to omeprazole. Further, the bioavailability of tenatoprazole was two-fold greater in the (S)-tenatoprazole sodium salt hydrate form as compared to the free form in dogs which is due to differences in the crystal structure and hydrophobic nature of the two forms.
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Affiliation(s)
- Jai Moo Shin
- Department of Physiology and Medicine, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, USA.
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Yeo M, Kim DK, Kim YB, Oh TY, Lee JE, Cho SW, Kim HC, Hahm KB. Selective induction of apoptosis with proton pump inhibitor in gastric cancer cells. Clin Cancer Res 2005; 10:8687-96. [PMID: 15623654 DOI: 10.1158/1078-0432.ccr-04-1065] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
PURPOSE To survive in an ischemic microenvironment with a lower extracellular pH, ability to up-regulate proton extrusion is critical for cancer cell survival. Gastric H+/K(+)-ATPase exchanges luminal K+ for cytoplasmic H+ and is the enzyme primarily responsible for gastric acidification. On the basis of the fact that blocking the clearance of acidic metabolites are known to induce the cell death, we hypothesized that pantoprazole (PPZ), one of gastric H+/K(+)-ATPase inhibitors used frequently to treat acid-related diseases, could inhibit growth of tumor cells. EXPERIMENTAL DESIGN Genomic DNA fragmentation, terminal deoxynucleotidyl transferase (Tdt)-mediated nick end labeling assay, and annexin V staining were performed to detect PPZ-induced apoptosis. Mitogen-activated protein kinase activation and heat shock proteins expression were determined by immunoblot with specific antibodies. The antitumor effect of PPZ was evaluated in vivo by a xenograft model of nude mice. RESULTS After PPZ treatment, apoptotic cell death was seen selectively in cancer cells and was accompanied with extracellular signal-regulated kinase deactivation. By contrast, normal gastric mucosal cells showed the resistance to PPZ-induced apoptosis through the overexpression of antiapoptotic regulators including HSP70 and HSP27. In a xenograft model of nude mice, administration of PPZ significantly inhibited tumorigenesis and induced large-scale apoptosis of tumor cells. CONCLUSIONS PPZ selectively induced in vivo and in vitro apoptotic cell death in gastric cancer, suggesting that proton pump inhibitors could be used for selective anticancer effects.
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Affiliation(s)
- Marie Yeo
- Genomic Research Center for Gastroenterology, Ajou University School of Medicine, Suwon, Korea
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Andersson K, Carlsson E. Potassium-competitive acid blockade: a new therapeutic strategy in acid-related diseases. Pharmacol Ther 2005; 108:294-307. [PMID: 16000224 DOI: 10.1016/j.pharmthera.2005.05.005] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Accepted: 05/04/2005] [Indexed: 02/06/2023]
Abstract
Current therapies to treat gastroesophageal reflux disease (GERD), peptic ulcer disease (PUD), and other acid-related diseases either prevent stimulation of the parietal cell (H2 receptor antagonists, H2RAs) or inhibit gastric H+,K+-ATPase (e.g., proton pump inhibitors, PPIs). Of the 2 approaches, the inhibition of the final step in acid production by PPIs provides more effective relief of symptoms and healing. Despite the documented efficacy of the PPIs, therapeutic doses have a gradual onset of effect and do not provide complete symptom relief in all patients. There is scope for further improvements in acid suppressive therapy to maximize healing and offer more complete symptom relief. It is unlikely that cholecystokinin2 (CCK2, gastrin) receptor antagonists, a class in clinical trials, will be superior to H2RAs or PPIs. However, a new class of acid suppressant, the potassium-competitive acid blockers (P-CABs), is undergoing clinical trials in GERD and other acid-related diseases. These drugs block gastric H+,K+-ATPase by reversible and K+-competitive ionic binding. After oral doses, P-CABs rapidly achieve high plasma concentrations and have linear, dose-dependent pharmacokinetics. The pharmacodynamic properties reflect the pharmacokinetics of this group (i.e., the effect on acid secretion is correlated with plasma concentrations). These agents dose dependently inhibit gastric acid secretion with a fast onset of action and have similar effects after single and repeated doses (i.e., full effect from the first dose). Animal studies comparing P-CABs with PPIs suggest some important pharmacodynamic differences (e.g., faster and better control of 24-hr intragastric acidity). Studies in humans comparing PPIs with P-CABs will help to define the place of this new class in the management of acid-related diseases.
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Shin JM, Sachs G. Differences in binding properties of two proton pump inhibitors on the gastric H+,K+-ATPase in vivo. Biochem Pharmacol 2005; 68:2117-27. [PMID: 15498502 DOI: 10.1016/j.bcp.2004.07.035] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2004] [Accepted: 07/27/2004] [Indexed: 11/24/2022]
Abstract
Restoration of acid secretion after treatment with covalently-bound proton pump inhibitors may depend on protein turnover and on reversal of inhibition by reducing agents such as glutathione. Glutathione incubation of the H(+),K(+)-ATPase isolated from omeprazole or pantoprazole-treated rats reversed 88% of the omeprazole inhibition but none of the pantoprazole inhibition. The present study was designed to measure binding properties of omeprazole or pantoprazole in vivo. Rats were injected with (14)C-omeprazole or (14)C-pantoprazole after acid stimulation. The specific binding to the gastric H(+),K(+)-ATPase was measured at timed intervals as well as reversal of binding by glutathione reduction. The stoichiometry of omeprazole and pantoprazole binding to the catalytic subunit of the H(+),K(+)-ATPase was 2 moles of inhibitor per mole of the H(+),K(+)-ATPase phosphoenzyme. Omeprazole bound to one cysteine between transmembrane segments 5/6 and one between 7/8, pantoprazole only to the two cysteines in the TM5/6 domain. Loss of drug from the pump was biphasic, the fast component accounted for 84% of omeprazole binding and 51% of pantoprazole binding. Similarly, only 16% of omeprazole binding but 40% of pantoprazole binding was not reversed by glutathione. The residence time of omeprazole and pantoprazole on the ATPase in vivo depends on the reversibility of binding. Binding of pantoprazole at cysteine 822 is irreversible whereas that of omeprazole at cysteine 813 and 892 is reversible both in vivo and in vitro. This is consistent with the luminal exposure of cysteine 813 and 892 and the intra-membranal location of cysteine 822 in the 3D structure of the H(+),K(+)-ATPase.
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Affiliation(s)
- Jai Moo Shin
- Department of Physiology and Medicine, University of California, Los Angeles, CA 90073, USA
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Shin JM, Cho YM, Sachs G. Chemistry of covalent inhibition of the gastric (H+, K+)-ATPase by proton pump inhibitors. J Am Chem Soc 2004; 126:7800-11. [PMID: 15212527 DOI: 10.1021/ja049607w] [Citation(s) in RCA: 194] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Proton pump inhibitors (PPIs), drugs that are widely used for treatment of acid related diseases, are either substituted pyridylmethylsulfinyl benzimidazole or imidazopyridine derivatives. They are all prodrugs that inhibit the acid-secreting gastric (H(+), K(+))-ATPase by acid activation to reactive thiophiles that form disulfide bonds with one or more cysteines accessible from the exoplasmic surface of the enzyme. This unique acid-catalysis mechanism had been ascribed to the nucleophilicity of the pyridine ring. However, the data obtained here show that their conversion to the reactive cationic thiophilic sulfenic acid or sulfenamide depends mainly not on pyridine protonation but on a second protonation of the imidazole component that increases the electrophilicity of the C-2 position on the imidazole. This protonation results in reaction of the C-2 with the unprotonated fraction of the pyridine ring to form the reactive derivatives. The relevant PPI pK(a)'s were determined by UV spectroscopy of the benzimidazole or imidazopyridine sulfinylmethyl moieties at different medium pH. Synthesis of a relatively acid stable analogue, N(1)-methyl lansoprazole, (6b), allowed direct determination of both pK(a) values of this intact PPI allowing calculation of the two pK(a) values for all the PPIs. These values predict their relative acid stability and thus the rate of reaction with cysteines of the active proton pump at the pH of the secreting parietal cell. The PPI accumulates in the secretory canaliculus of the parietal cell due to pyridine protonation then binds to the pump and is activated by the second protonation on the surface of the protein to allow disulfide formation.
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Affiliation(s)
- Jai Moo Shin
- Department of Physiology and Medicine, University of California at Los Angeles, and VA Greater Los Angeles Healthcare System, Los Angeles, California 90073, USA.
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Olbe L, Carlsson E, Lindberg P. A proton-pump inhibitor expedition: the case histories of omeprazole and esomeprazole. Nat Rev Drug Discov 2003; 2:132-9. [PMID: 12563304 DOI: 10.1038/nrd1010] [Citation(s) in RCA: 246] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Lars Olbe
- AstraZeneca R&D, 431 83 Mölndal, Sweden.
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Abstract
BACKGROUND & AIMS Proton pump inhibitors (PPIs) are covalent inhibitors of the gastric H+,K+-adenosine triphosphatase (ATPase) forming disulfide bonds. Recovery of acid secretion after PPI inhibition may be due to de novo synthesis of pump protein and/or disulfide reduction and reactivation of inhibited pump. The half-time of recovery of acid secretion in rats following omeprazole treatment is approximately 15 hours, whereas pump protein half-life is 54 hours. In humans, the half-life of the inhibitory effect on acid secretion is approximately 28 hours for omeprazole and approximately 46 hours for pantoprazole. Whereas all PPIs bind to cysteine 813, pantoprazole additionally binds to cysteine 822, deeper in the membrane domain of TM6. Their different durations of action may reflect different rates of pump reactivation due to differing accessibility of the disulfides to glutathione. METHODS Rats were stimulated and treated with 30 mg/kg of each PPI. Gastric ATPase was prepared and reversal of inhibition of the H+,K+-ATPase was measured as the time-dependent restoration of activity by incubation with dithiothreitol or glutathione. RESULTS One hundred percent reactivation of ATPase following inhibition in vivo by omeprazole or its enantiomers was seen with dithiothreitol and 89% with glutathione. Similar data were found for lansoprazole or rabeprazole. No reactivation by either reducing agent was seen following inhibition by pantoprazole. CONCLUSIONS Recovery of acid secretion following inhibition by all PPIs, other than pantoprazole, may depend on both protein turnover and reversal of the inhibitory disulfide bond. In contrast, recovery of acid secretion after pantoprazole may depend entirely on new protein synthesis.
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Affiliation(s)
- Jai Moo Shin
- Department of Physiology and Medicine, University of California at Los Angeles, and VA Greater Los Angeles Healthcare System, Los Angeles, California, USA
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36
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Shin JM, Goldshleger R, Munson KB, Sachs G, Karlish SJ. Selective Fe2+-catalyzed oxidative cleavage of gastric H+,K+-ATPase: implications for the energy transduction mechanism of P-type cation pumps. J Biol Chem 2001; 276:48440-50. [PMID: 11585827 DOI: 10.1074/jbc.m106864200] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the presence of ascorbate/H(2)O(2), Fe(2+) ions or the ATP-Fe(2+) complex catalyze selective cleavage of the alpha subunit of gastric H(+),K(+)-ATPase. The electrophoretic mobilities of the fragments and dependence of the cleavage patterns on E(1) and E(2) conformational states are essentially identical to those described previously for renal Na(+),K(+)-ATPase. The cleavage pattern of H(+),K(+)-ATPase by Fe(2+) ions is consistent with the existence of two Fe(2+) sites: site 1 within highly conserved sequences in the P and A domains, and site 2 at the cytoplasmic entrance to trans-membrane segments M3 and M1. The change in the pattern of cleavage catalyzed by Fe(2+) or the ATP-Fe(2+) complex induced by different ligands provides evidence for large conformational movements of the N, P, and A cytoplasmic domains of the enzyme. The results are consistent with the Ca(2+)-ATPase crystal structure (Protein Data Bank identification code; Toyoshima, C., Nakasako, M., Nomura, H., and Ogawa, H. (2000) Nature 405, 647-655), an E(1)Ca(2+) conformation, and a theoretical model of Ca(2+)-ATPase in an E(2) conformation (Protein Data Bank identification code ). Thus, it can be presumed that the movements of N, P, and A cytoplasmic domains, associated with the E(1) <--> E(2) transitions, are similar in all P-type ATPases. Fe(2+)-catalyzed cleavage patterns also reveal sequences involved in phosphate, Mg(2+), and ATP binding, which have not yet been shown in crystal structures, as well as changes which occur in E(1) <--> E(2) transitions, and subconformations induced by H(+),K(+)-ATPase-specific ligands such as SCH28080.
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Affiliation(s)
- J M Shin
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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37
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Franic TV, Judd LM, Robinson D, Barrett SP, Scarff KL, Gleeson PA, Samuelson LC, Van Driel IR. Regulation of gastric epithelial cell development revealed in H(+)/K(+)-ATPase beta-subunit- and gastrin-deficient mice. Am J Physiol Gastrointest Liver Physiol 2001; 281:G1502-11. [PMID: 11705756 DOI: 10.1152/ajpgi.2001.281.6.g1502] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The gastric H(+)/K(+)-ATPase is essential for normal development of parietal cells. Here we have directly assessed the role of the H(+)/K(+)-ATPase beta-subunit (H/K-beta) on epithelial cell development by detailed quantitation of the epithelial cell types of the gastric mucosa of H/K-beta-deficient mice. H/K-beta-deficient mice had a 3.1-fold increase in the number of immature cells per gastric unit; however, the numbers of surface mucous and parietal cells were similar to those in the gastric units of wild-type mice. The effect of elevated gastrin levels in the H/K-beta-deficient mice was determined by producing mice that are also deficient in gastrin. We demonstrated that the increased production of immature cells and resulting hypertrophy is caused by the overproduction of gastrin. However, the depletion of zymogenic cells, which is another feature of H/K-beta-deficient mice, is independent of hypergastrinemia. Significantly, parietal cells of H/K-beta- and gastrin-deficient mice had abnormal secretory membranes and were devoid of resting tubulovesicular membranes. Together these data suggest a homeostatic mechanism limiting the number of immature cells that can develop into end-stage epithelial cells and indicate a direct role for H/K-beta in the development of mature parietal cells.
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Affiliation(s)
- T V Franic
- Department of Pathology and Immunology, Monash University Medical School, Alfred Hospital, Melbourne, Victoria, Australia 3181
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38
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Baeyens N, Wattiez R, Raussens V, Ruysschaert JM, Goormaghtigh E. Structural modifications in the membrane-bound regions of the gastric H+/K+-ATPase upon ligand binding. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:5135-41. [PMID: 11589705 DOI: 10.1046/j.0014-2956.2001.02443.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Extensive trypsin proteolysis was used to examine the accessibility of membrane bound segments of the gastric H+/K+-ATPase under different experimental conditions known to induce either the E1 or the E2 conformation. Membrane-anchored peptides were isolated after trypsinolysis and identified by sequencing. We show that several membrane bound segments are involved in the conformational change. In the N-terminal region, a M1-M2 peptide (12 kDa) was found to be associated with the membrane fraction after digestion in the presence of K+ or in the presence of vanadate (12 kDa and 15 kDa). In the M3 and M4 region, no difference was observed for the peptide obtained in E1 or E2-K conformations, but the peptide generated in the presence of vanadate begins 12 amino-acid residues earlier in the sequence. Cytoplasmic loop region: we show here that a peptide beginning at Asp574 and predicted to end at Arg693 is associated with the membrane for a vanadate-induced conformation. In the M5-M6 region, the membrane-anchored peptide obtained on E1 is 39 amino acids shorter than the E2 peptide. In the M7-M8 region, the same peptide encompassing the M7 and M8 transmembrane segments was produced for E1 and E2 conformations.
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Affiliation(s)
- N Baeyens
- Structure and Function of Biological Membranes, Free University of Brussels, Boulevard du Triomphe, B1050 Brussels, Belgium
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39
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Asano S, Io T, Kimura T, Sakamoto S, Takeguchi N. Alanine-scanning mutagenesis of the sixth transmembrane segment of gastric H+,K+-ATPase alpha-subunit. J Biol Chem 2001; 276:31265-73. [PMID: 11397805 DOI: 10.1074/jbc.m103698200] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The sixth transmembrane (M6) segment of the catalytic subunit plays an important role in the ion recognition and transport in the type II P-type ATPase families. In this study, we singly mutated all amino acid residues in the M6 segment of gastric H(+),K(+)-ATPase alpha-subunit with alanine, expressed the mutants in HEK-293 cells, and studied the effects of the mutation on the functions of H(+),K(+)-ATPase; overall K(+)-stimulated ATPase, phosphorylation, and dephosphorylation. Four mutants, L819A, D826A, I827A, and L833A, completely lost the K(+)-ATPase activity. Mutant L819A was phosphorylated but hardly dephosphorylated in the presence of K(+), whereas mutants D826A, I827A, and L833A were not phosphorylated from ATP. We found that almost all of these amino acid residues, which are important for the function, are located on the same side of the alpha-helix of the M6 segment. In addition, we found that amino acids involved in the phosphorylation are located exclusively in the cytoplasmic half of the M6 segment and those involved in the K(+)-dependent dephosphorylation are in the luminal half. Several mutants such as I821A, L823A, T825A, and P829A partly retained the K(+)-ATPase activity accompanying the decrease in the rate of phosphorylation.
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Affiliation(s)
- S Asano
- Molecular Genetics Research Center and the Faculty of Pharmaceutical Sciences of Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan.
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Sweadner KJ, Donnet C. Structural similarities of Na,K-ATPase and SERCA, the Ca(2+)-ATPase of the sarcoplasmic reticulum. Biochem J 2001; 356:685-704. [PMID: 11389677 PMCID: PMC1221896 DOI: 10.1042/0264-6021:3560685] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The crystal structure of SERCA1a (skeletal-muscle sarcoplasmic-reticulum/endoplasmic-reticulum Ca(2+)-ATPase) has recently been determined at 2.6 A (note 1 A = 0.1 nm) resolution [Toyoshima, Nakasako, Nomura and Ogawa (2000) Nature (London) 405, 647-655]. Other P-type ATPases are thought to share key features of the ATP hydrolysis site and a central core of transmembrane helices. Outside of these most-conserved segments, structural similarities are less certain, and predicted transmembrane topology differs between subclasses. In the present review the homologous regions of several representative P-type ATPases are aligned with the SERCA sequence and mapped on to the SERCA structure for comparison. Homology between SERCA and the Na,K-ATPase is more extensive than with any other ATPase, even PMCA, the Ca(2+)-ATPase of plasma membrane. Structural features of the Na,K-ATPase are projected on to the Ca(2+)-ATPase crystal structure to assess the likelihood that they share the same fold. Homology extends through all ten transmembrane spans, and most insertions and deletions are predicted to be at the surface. The locations of specific residues are examined, such as proteolytic cleavage sites, intramolecular cross-linking sites, and the binding sites of certain other proteins. On the whole, the similarity supports a shared fold, with some particular exceptions.
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Affiliation(s)
- K J Sweadner
- Neuroscience Center, Massachusetts General Hospital, 149-6118, 149 13th Street, Charlestown, MA 02129, USA.
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41
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Donnet C, Arystarkhova E, Sweadner KJ. Thermal denaturation of the Na,K-ATPase provides evidence for alpha-alpha oligomeric interaction and gamma subunit association with the C-terminal domain. J Biol Chem 2001; 276:7357-65. [PMID: 11099502 DOI: 10.1074/jbc.m009131200] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thermal denaturation can help elucidate protein domain substructure. We previously showed that the Na,K-ATPase partially unfolded when heated to 55 degrees C (Arystarkhova, E., Gibbons, D. L., and Sweadner, K. J. (1995) J. Biol. Chem. 270, 8785-8796). The beta subunit unfolded without leaving the membrane, but three transmembrane spans (M8-M10) and the C terminus of the alpha subunit were extruded, while the rest of alpha retained its normal topology with respect to the lipid bilayer. Here we investigated thermal denaturation further, with several salient results. First, trypsin sensitivity at both surfaces of alpha was increased, but not sensitivity to V8 protease, suggesting that the cytoplasmic domains and extruded domain were less tightly packed but still retained secondary structure. Second, thermal denaturation was accompanied by SDS-resistant aggregation of alpha subunits as dimers, trimers, and tetramers without beta or gamma subunits. This implies specific alpha-alpha contact. Third, the gamma subunit, like the C-terminal spans of alpha, was selectively lost from the membrane. This suggests its association with M8-M10 rather than the more firmly anchored transmembrane spans. The picture that emerges is of a Na,K-ATPase complex of alpha, beta, and gamma subunits in which alpha can associate in assemblies as large as tetramers via its cytoplasmic domain, while beta and gamma subunits associate with alpha primarily in its C-terminal portion, which has a unique structure and thermal instability.
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Affiliation(s)
- C Donnet
- Laboratory of Membrane Biology, Neuroscience Center, Massachusetts General Hospital, Charlestown 02129, USA
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42
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Farley RA, Schreiber S, Wang SG, Scheiner-Bobis G. A hybrid between Na+,K+-ATPase and H+,K+-ATPase is sensitive to palytoxin, ouabain, and SCH 28080. J Biol Chem 2001; 276:2608-15. [PMID: 11054424 DOI: 10.1074/jbc.m008784200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Na(+),K(+)-ATPase is inhibited by cardiac glycosides such as ouabain, and palytoxin, which do not inhibit gastric H(+),K(+)-ATPase. Gastric H(+),K(+)-ATPase is inhibited by SCH28080, which has no effect on Na(+),K(+)-ATPase. The goal of the current study was to identify amino acid sequences of the gastric proton-potassium pump that are involved in recognition of the pump-specific inhibitor SCH 28080. A chimeric polypeptide consisting of the rat sodium pump alpha3 subunit with the peptide Gln(905)-Val(930) of the gastric proton pump alpha subunit substituted in place of the original Asn(886)-Ala(911) sequence was expressed together with the gastric beta subunit in the yeast Saccharomyces cerevisiae. Yeast cells that express this subunit combination are sensitive to palytoxin, which interacts specifically with the sodium pump, and lose intracellular K(+) ions. The palytoxin-induced K(+) efflux is inhibited by the sodium pump-specific inhibitor ouabain and also by the gastric proton pump-specific inhibitor SCH 28080. The IC(50) for SCH 28080 inhibition of palytoxin-induced K(+) efflux is 14.3 +/- 2.4 microm, which is similar to the K(i) for SCH 28080 inhibition of ATP hydrolysis by the gastric H(+),K(+)-ATPase. In contrast, palytoxin-induced K(+) efflux from cells expressing either the native alpha3 and beta1 subunits of the sodium pump or the alpha3 subunit of the sodium pump together with the beta subunit of the gastric proton pump is inhibited by ouabain but not by SCH 28080. The acquisition of SCH 28080 sensitivity by the chimera indicates that the Gln(905)-Val(930) peptide of the gastric proton pump is likely to be involved in the interactions of the gastric proton-potassium pump with SCH 28080.
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Affiliation(s)
- R A Farley
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles 90033, USA.
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43
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Lambrecht N, Munson K, Vagin O, Sachs G. Comparison of covalent with reversible inhibitor binding sites of the gastric H,K-ATPase by site-directed mutagenesis. J Biol Chem 2000; 275:4041-8. [PMID: 10660561 DOI: 10.1074/jbc.275.6.4041] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The gastric H,K-ATPase is covalently inhibited by substituted pyridyl-methylsulfinyl-benzimidazoles, such as omeprazole, that convert to thiophilic probes of luminally accessible cysteines in the acid space. The K(+) competitive inhibitor, SCH28080, prevented inhibition of acid transport by omeprazole. In stably expressing HEK293 cells, the benzimidazole-reactive cysteines, Cys-321 (transmembrane helix (TM) 3), Cys-813 and Cys-822 (TM5/6), and Cys-892 (TM7/8) were mutated to the amino acids found in the SCH28080-resistant Na,K-ATPase and kinetic parameters of H,K-ATPase activity analyzed. Mutations of Cys-822 and Cys-892 had insignificant effects on the K(i(app)), K(m(app)) or V(max), but mutations of Cys-813 to threonine and Cys-321 to alanine decreased the affinity for SCH28080. Mutation of Cys-321 to alanine produced mixed kinetics of inhibition, still with higher affinity for the cation-free form of phosphoenzyme. Since the phenylmethoxy ring of the imidazo-pyridine inhibitors binds to TM1/2, as shown by earlier photoaffinity studies, and the mutations in TM6 (Cys-813 --> Thr) as well as the end of TM3 (Cys-321 --> Ala) decrease the affinity for SCH28080, the TM1/2, TM3, and TM6 helices lie within approximately 16 A of each other based on the size of the active, extended conformation of SCH28080.
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Affiliation(s)
- N Lambrecht
- Department of Physiology, School of Medicine, UCLA and Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California 90073, USA
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Tsukimi Y, Ushiro T, Yamazaki T, Ishikawa H, Hirase J, Narita M, Nishigaito T, Banno K, Ichihara T, Tanaka H. Studies on the mechanism of action of the gastric H+,K(+)-ATPase inhibitor SPI-447. JAPANESE JOURNAL OF PHARMACOLOGY 2000; 82:21-8. [PMID: 10874584 DOI: 10.1254/jjp.82.21] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
3-Amino-5-methyl-2(2-methyl-3-thienyl)- imidazo[1,2-a]thieno[3,2-c]pyridine, SPI-447, is a potent gastric H+,K(+)-ATPase inhibitor, but a detailed mechanism of the inhibition is unknown. This study was designed to investigate the mechanism by which SPI-447 inhibits gastric H+,K(+)-ATPase. For this purpose, the inhibitory action of SPI-447 on gastric H+,K(+)-ATPase from porcine gastric mucosa was compared with that of omeprazole (an irreversible inhibitor) and SCH28080 (a reversible inhibitor). All compounds produced dose-dependent inhibition of gastric H+,K(+)-ATPase, and the inhibitory intensities were increased under acidic conditions. The anti-H+,K(+)-ATPase actions of SPI-447 and SCH28080 were attenuated by dilution, but not influenced by glutathione pretreatment. In contrast, that of omeprazole was not influenced by dilution, but was suppressed by glutathione pretreatment. KCl addition reversed the inhibition of H+,K(+)-ATPase-mediated H(+)-transport by SPI-447 and SCH28080, but had no effect on that by omeprazole. The anti-gastric H+,K(+)-ATPase action of SPI-447 was additive with that of SCH28080. SPI-447 and SCH28080 had no effect on Na+,K(+)-ATPase activity. These findings indicated that the inhibitory mechanism of SPI-447 on gastric H+,K(+)-ATPase was similar to that of SCH28080, but different from that of omeprazole; i.e., 1) reversible, 2) SH-group independent, 3) K(+)-competitive, and 4) highly specific against gastric H+,K(+)-ATPase.
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Affiliation(s)
- Y Tsukimi
- Department of New Drug Research Laboratories, Shinnippon Pharmaceutical, Inc., Kishiwada, Japan
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45
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Scarff KL, Judd LM, Toh BH, Gleeson PA, Van Driel IR. Gastric H(+),K(+)-adenosine triphosphatase beta subunit is required for normal function, development, and membrane structure of mouse parietal cells. Gastroenterology 1999; 117:605-18. [PMID: 10464136 DOI: 10.1016/s0016-5085(99)70453-1] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Parietal cells of the gastric mucosa contain a complex and extensive secretory membrane system that harbors gastric H(+),K(+)-adenosine triphosphatase (ATPase), the enzyme primarily responsible for acidification of the gastric lumen. We have produced mice deficient in the H(+),K(+)-ATPase beta subunit to determine the role of the protein in the biosynthesis of this membrane system and the biology of gastric mucosa. METHODS Mice deficient in the H(+), K(+)-ATPase beta subunit were produced by gene targeting. RESULTS The stomachs of H(+),K(+)-ATPase beta subunit-deficient mice were achlorhydric. Histological and immunocytochemical analyses with antibodies to the H(+),K(+)-ATPase alpha subunit revealed that parietal cell development during ontogeny was retarded in H(+), K(+)-ATPase beta subunit-deficient mice. In 15-day-old mice, cells with secretory canaliculi were observed in wild-type but not in H(+), K(+)-ATPase beta subunit-deficient mice. Parietal cells of H(+), K(+)-ATPase beta subunit-deficient mice 17 days and older contained an abnormal canaliculus that was dilated and contained fewer and shorter microvilli than normal. In older parietal cells, the abnormal canaliculus was massive (25 micrometer in diameter) and contained few microvilli. We did not observe typical tubulovesicular membranes in any parietal cell from H(+),K(+)-ATPase beta subunit-deficient mice. Histopathologic alterations were only observed in the stomach. CONCLUSIONS The H(+),K(+)-ATPase beta subunit is required for acid-secretory activity of parietal cells in vivo, normal development and cellular homeostasis of the gastric mucosa, and attainment of the normal structure of the secretory membranes.
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Affiliation(s)
- K L Scarff
- Department of Pathology and Immunology, Monash University Medical School, Alfred Hospital, Melbourne, Victoria, Australia
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46
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Rulli SJ, Horiba MN, Skripnikova E, Rabon EC. Glu-857 moderates K+-dependent stimulation and SCH 28080-dependent inhibition of the gastric H,K-ATPase. J Biol Chem 1999; 274:15245-50. [PMID: 10329734 DOI: 10.1074/jbc.274.21.15245] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The rabbit H,K-ATPase alpha- and beta-subunits were transiently expressed in HEK293 T cells. The co-expression of the H,K-ATPase alpha- and beta-subunits was essential for the functional H,K-ATPase. The K+-stimulated H,K-ATPase activity of 0.82 +/- 0.2 micromol/mg/h saturated with a K0.5 (KCl) of 0.6 +/- 0.1 mM, whereas the 2-methyl-8-(phenylmethoxy)imidazo[1,2a]pyridine-3-acetonitrile (SCH 28080)-inhibited ATPase of 0.62 +/- 0.07 micromol/mg/h saturated with a Ki (SCH 28080) of 1.0 +/- 0.3 microM. Site mutations were introduced at the N,N-dicyclohexylcarbodiimide-reactive residue, Glu-857, to evaluate the role of this residue in ATPase function. Variations in the side chain size and charge of this residue did not inhibit the specific activity of the H,K-ATPase, but reversal of the side chain charge by substitution of Lys or Arg for Glu produced a reciprocal change in the sensitivity of the H,K-ATPase to K+ and SCH 28080. The K0.5 for K+stimulated ATPase was decreased to 0.2 +/-.05 and 0.2 +/-.03 mM, respectively, in Lys-857 and Arg-857 site mutants, whereas the Ki for SCH 28080-dependent inhibition was increased to 6.5 +/- 1.4 and 5.9 +/- 1.5 microM, respectively. The H,K-ATPase kinetics were unaffected by the introduction of Ala at this site, but Leu produced a modest reciprocal effect. These data indicate that Glu-857 is not an essential residue for cation-dependent activity but that the residue influences the kinetics of both K+ and SCH 28080-mediated functions. This finding suggests a possible role of this residue in the conformational equilibrium of the H,K-ATPase.
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Affiliation(s)
- S J Rulli
- Department of Physiology, Tulane University Medical Center and the Department of Veterans Affairs, New Orleans, Louisiana 70112, USA
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47
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Gatto C, Lutsenko S, Shin JM, Sachs G, Kaplan JH. Stabilization of the H,K-ATPase M5M6 membrane hairpin by K+ ions. Mechanistic significance for p2-type atpases. J Biol Chem 1999; 274:13737-40. [PMID: 10318774 DOI: 10.1074/jbc.274.20.13737] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The integral membrane protein, the gastric H,K-ATPase, is an alpha-beta heterodimer, with 10 putative transmembrane segments in the alpha-subunit and one such segment in the beta-subunit. All transmembrane segments remain within the membrane domain following trypsinization of the intact gastric H,K-ATPase in the presence of K+ ions, identified as M1M2, M3M4, M5M6, and M7, M8, M9, and M10. Removal of K+ ions from this digested preparation results in the selective loss of the M5M6 hairpin from the membrane. The release of the M5M6 fragment is directed to the extracellular phase as evidenced by the accumulation of the released M5M6 hairpin inside the sealed inside out vesicles. The stabilization of the M5M6 hairpin in the membrane phase by the transported cation as well as loss to the aqueous phase in the absence of the transported cation has been previously observed for another P2-type ATPase, the Na, K-ATPase (Lutsenko, S., Anderko, R., and Kaplan, J. H. (1995) Proc. Natl. Acad. Sci. U. S. A. 92, 7936-7940). Thus, the effects of the counter-transported cation on retention of the M5M6 segment in the membrane as compared with the other membrane pairs may be a general feature of P2-ATPase ion pumps, reflecting a flexibility of this region that relates to the mechanism of transport.
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Affiliation(s)
- C Gatto
- Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland Oregon 97201-3098, USA
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48
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Raussens V, Pézolet M, Ruysschaert JM, Goormaghtigh E. Structural difference in the H+,K+-ATPase between the E1 and E2 conformations. An attenuated total reflection infrared spectroscopy, UV circular dichroism and raman spectroscopy study. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 262:176-83. [PMID: 10231379 DOI: 10.1046/j.1432-1327.1999.00365.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Conformational changes taking place in the gastric H+,K+-ATPase when shifting from the K+-induced E2 form to the E1 form upon replacing K+ ions by Na+ were investigated by different spectroscopic approaches. No significant secondary-structure change or secondary-structure reorientation with respect to the membrane plane could be measured by attenuated total reflection Fourier transform infrared spectroscopy of oriented films. Circular dichroism and Raman spectra obtained on tubulovesicle suspensions indicated no significant secondary structure or tyrosine and tryptophan side-chain environment changes in tubulovesicle suspensions. The smallest observable structural changes are discussed in term of the number of amino-acid residues involved for each technique.
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Affiliation(s)
- V Raussens
- Laboratoire de Chimie-Physique des Macromolécules aux Interfaces, CP 206/2, Université Libre de Bruxelles, Campus Plaine, Belgium
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Gupta SS, DeWitt ND, Allen KE, Slayman CW. Evidence for a salt bridge between transmembrane segments 5 and 6 of the yeast plasma-membrane H+-ATPase. J Biol Chem 1998; 273:34328-34. [PMID: 9852098 DOI: 10.1074/jbc.273.51.34328] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The plasma-membrane H+-ATPase of Saccharomyces cerevisiae, which belongs to the P2 subgroup of cation-transporting ATPases, is encoded by the PMA1 gene and functions physiologically to pump protons out of the cell. This study has focused on hydrophobic transmembrane segments M5 and M6 of the H+-ATPase. In particular, a conserved aspartate residue near the middle of M6 has been found to play a critical role in the structure and biogenesis of the ATPase. Site-directed mutants in which Asp-730 was replaced by an uncharged residue (Asn or Val) were abnormally sensitive to trypsin, consistent with the idea that the proteins were poorly folded, and immunofluorescence confocal microscopy showed them to be arrested in the endoplasmic reticulum. Similar defects are known to occur when either Arg-695 or His-701 in M5 is replaced by a neutral residue (Dutra, M. B., Ambesi, A., and Slayman, C. W. (1998) J. Biol. Chem. 273, 17411-17417). To search for possible charge-charge interactions between Asp-730 and Arg-695 or His-701, double mutants were constructed in which positively and negatively charged residues were swapped or eliminated. Strikingly, two of the double mutants (R695D/D730R and R695A/D730A) regained the capacity for normal biogenesis and displayed near-normal rates of ATP hydrolysis and ATP-dependent H+ pumping. These results demonstrate that neither Arg-695 nor Asp-730 is required for enzymatic activity or proton transport, but suggest that there is a salt bridge between the two residues, linking M5 and M6 of the 100-kDa polypeptide.
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Affiliation(s)
- S S Gupta
- Departments of Genetics and Cellular & Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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50
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Bhattacharjee M, Chakraborty T, Ganguly C, Banerjee RK. Inhibition of gastric mucosal prostaglandin synthetase activity by mercaptomethylimidazole, an inducer of gastric acid secretion--plausible involvement of endogenous H2O2. Biochem Pharmacol 1998; 56:905-13. [PMID: 9774152 DOI: 10.1016/s0006-2952(98)00063-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have reported earlier that mercaptomethylimidazole (MMI), an antithyroid drug of thionamide group, induces gastric acid secretion at least partially through the liberation of histamine, sensitive to cimetidine. Now, we show that the drug has a significant inhibitory effect on the cyclooxygenase and peroxidase activity of the prostaglandin (PG) synthetase of the gastric mucosal microsomal preparation. The effect can also be mimicked by low concentrations of H2O2. While studying the possible intracellular effect of MMI on acid secretion, a cell fraction (F3) enriched in parietal cell was isolated by controlled digestion of the mucosa with protease. This cell fraction is activated by MMI as measured by increased O2 consumption. The activation is sensitive to omeprazole, a proton-pump inhibitor, indicating that the activation is due to increased acid secretion by MMI. MMI was also found to directly inhibit the peroxidase activity of the F3 cell fraction and may thus increase the intracellular level of H2O2. The cyclooxygenase activity of the PG synthetase of the F3 cell fraction is also inhibited by MMI and the effect can be reproduced by low concentrations of H2O2. Both MMI and H2O2 can also inhibit the peroxidase activity of the PG synthetase. We suggest that in addition to the activation of the parietal cell by MMI possibly through endogenous H2O2, MMI induces acid secretion in vivo by inactivating the PG synthetase thereby inhibiting the biosynthesis of PG and removing its inhibitory influence on acid secretion so that the histamine released by MMI can stimulate acid secretion with maximum efficiency.
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Affiliation(s)
- M Bhattacharjee
- Department of Physiology, Indian Institute of Chemical Biology, Calcutta
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