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Wang C, Zhang B, Cong Y, Du X, Chen S, Visser L, Ruiz-Moreno AJ, Zhang L, Reggiori F, Dömling ASS, Groves MR. Small-Molecule Allosteric Inhibitors of Human Aspartate Transcarbamoylase Suppress Proliferation of Bone Osteosarcoma Epithelial Cells. ChemMedChem 2024; 19:e202300688. [PMID: 38602859 DOI: 10.1002/cmdc.202300688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 04/11/2024] [Accepted: 04/11/2024] [Indexed: 04/13/2024]
Abstract
Aspartate transcarbamoylase (ATC) is the first committed step in de novo pyrimidine biosynthesis in eukaryotes and plants. A potent transition state analog of human ATCase (PALA) has previously been assessed in clinical trials for the treatment of cancer, but was ultimately unsuccessful. Additionally, inhibition of this pathway has been proposed to be a target to suppress cell proliferation in E. coli, the malarial parasite and tuberculosis. In this manuscript we screened a 70-member library of ATC inhibitors developed against the malarial and tubercular ATCases for inhibitors of the human ATC. Four compounds showed low nanomolar inhibition (IC50 30-120 nM) in an in vitro activity assay. These compounds significantly outperform PALA, which has a triphasic inhibition response under identical conditions, in which significant activity remains at PALA concentrations above 10 μM. Evidence for a druggable allosteric pocket in human ATC is provided by both in vitro enzyme kinetic, homology modeling and in silico docking. These compounds also suppress the proliferation of U2OS osteoblastoma cells by promoting cell cycle arrest in G0/G1 phase. This report provides the first evidence for an allosteric pocket in human ATC, which greatly enhances its druggability and demonstrates the potential of this series in cancer therapy.
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Affiliation(s)
- Chao Wang
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV, The, Netherlands
| | - Bidong Zhang
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV, The, Netherlands
| | - Yingying Cong
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV, The, Netherlands
- Department of Biomedicine, Aarhus University, Ole Worms Alle' 4, 8000, Aarhus C, Denmark
| | - Xiaochen Du
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV, The, Netherlands
| | - Siyao Chen
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV, The, Netherlands
| | - Lidia Visser
- Department of Pathology and Medical Biology, University of Groningen, University Medical Center Groningen, 9700 RB, Groningen, The, Netherlands
| | - Angel J Ruiz-Moreno
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV, The, Netherlands
| | - Lili Zhang
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV, The, Netherlands
| | - Fulvio Reggiori
- Department of Biomedicine, Aarhus University, Ole Worms Alle' 4, 8000, Aarhus C, Denmark
| | - Alexander S S Dömling
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV, The, Netherlands
- CATRIN, Department of Innovative Chemistry, Palack University, 779 00, Olomouc - Holice, Czech Republic
| | - Matthew R Groves
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV, The, Netherlands
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2
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Du X, Sonawane V, Zhang B, Wang C, de Ruijter B, Dömling ASS, Reiling N, Groves MR. Inhibitors of Aspartate Transcarbamoylase Inhibit Mycobacterium tuberculosis Growth. ChemMedChem 2023; 18:e202300279. [PMID: 37294060 DOI: 10.1002/cmdc.202300279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 06/07/2023] [Accepted: 06/07/2023] [Indexed: 06/10/2023]
Abstract
Aspartate transcarbamoylase (ATCase) plays a key role in the second step of de novo pyrimidine biosynthesis in eukaryotes and has been proposed to be a target to suppress cell proliferation in E. coli, human cells and the malarial parasite. We hypothesized that a library of ATCase inhibitors developed for malarial ATCase (PfATCase) may also contain inhibitors of the tubercular ATCase and provide a similar inhibition of cellular proliferation. Of the 70 compounds screened, 10 showed single-digit micromolar inhibition in an in vitro activity assay and were tested for their effect on M. tuberculosis cell growth in culture. The most promising compound demonstrated a MIC90 of 4 μM. A model of MtbATCase was generated using the experimental coordinates of PfATCase. In silico docking experiments showed this compound can occupy a similar allosteric pocket on MtbATCase to that seen on PfATCase, explaining the observed species selectivity seen for this compound series.
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Affiliation(s)
- Xiaochen Du
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV (The, Netherlands
| | - Vidhisha Sonawane
- CATRIN, Department of Innovative Chemistry, PalackȳUniversity, 779 00, Olomouc - Holice, Czech Republic
| | - Bidong Zhang
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV (The, Netherlands
| | - Chao Wang
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV (The, Netherlands
| | - Bram de Ruijter
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV (The, Netherlands
| | - Alexander S S Dömling
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV (The, Netherlands
- CATRIN, Department of Innovative Chemistry, PalackȳUniversity, 779 00, Olomouc - Holice, Czech Republic
| | - Norbert Reiling
- RG Microbial Interface Biology, Research Center Borstel Leibniz Lung Center, Parkallee 1-40, Borstel, 23845, Sülfeld, Germany
- German Center for Infection Research (DZIF), Partner Site Hamburg-Lübeck-Borstel-Riems Borstel, 23845, Greifswald, Germany
| | - Matthew R Groves
- XB20 Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, A. Deusinglaan 1, Groningen, 9700AV (The, Netherlands
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3
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Shin J, Mir H, Khurram MA, Fujihara KM, Dynlacht BD, Cardozo TJ, Possemato R. Allosteric regulation of CAD modulates de novo pyrimidine synthesis during the cell cycle. Nat Metab 2023; 5:277-293. [PMID: 36747088 PMCID: PMC10064490 DOI: 10.1038/s42255-023-00735-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 01/03/2023] [Indexed: 02/08/2023]
Abstract
Metabolism is a fundamental cellular process that is coordinated with cell cycle progression. Despite this association, a mechanistic understanding of cell cycle phase-dependent metabolic pathway regulation remains elusive. Here we report the mechanism by which human de novo pyrimidine biosynthesis is allosterically regulated during the cell cycle. Combining traditional synchronization methods and metabolomics, we characterize metabolites by their accumulation pattern during cell cycle phases and identify cell cycle phase-dependent regulation of carbamoyl-phosphate synthetase 2, aspartate transcarbamylase and dihydroorotase (CAD), the first, rate-limiting enzyme in de novo pyrimidine biosynthesis. Through systematic mutational scanning and structural modelling, we find allostery as a major regulatory mechanism that controls the activity change of CAD during the cell cycle. Specifically, we report evidence of two Animalia-specific loops in the CAD allosteric domain that involve sensing and binding of uridine 5'-triphosphate, a CAD allosteric inhibitor. Based on homology with a mitochondrial carbamoyl-phosphate synthetase homologue, we identify a critical role for a signal transmission loop in regulating the formation of a substrate channel, thereby controlling CAD activity.
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Affiliation(s)
- Jong Shin
- Department of Pathology, New York University Grossman School of Medicine, New York, NY, USA
- Laura & Isaac Perlmutter Cancer Center, New York, NY, USA
| | - Hannan Mir
- Department of Pathology, New York University Grossman School of Medicine, New York, NY, USA
- Laura & Isaac Perlmutter Cancer Center, New York, NY, USA
| | - Maaz A Khurram
- Department of Pathology, New York University Grossman School of Medicine, New York, NY, USA
- Laura & Isaac Perlmutter Cancer Center, New York, NY, USA
| | - Kenji M Fujihara
- Department of Pathology, New York University Grossman School of Medicine, New York, NY, USA
- Laura & Isaac Perlmutter Cancer Center, New York, NY, USA
| | - Brian D Dynlacht
- Department of Pathology, New York University Grossman School of Medicine, New York, NY, USA
- Laura & Isaac Perlmutter Cancer Center, New York, NY, USA
| | - Timothy J Cardozo
- Laura & Isaac Perlmutter Cancer Center, New York, NY, USA
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Richard Possemato
- Department of Pathology, New York University Grossman School of Medicine, New York, NY, USA.
- Laura & Isaac Perlmutter Cancer Center, New York, NY, USA.
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4
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del Caño-Ochoa F, Rubio-del-Campo A, Ramón-Maiques S. A Tailored Strategy to Crosslink the Aspartate Transcarbamoylase Domain of the Multienzymatic Protein CAD. MOLECULES (BASEL, SWITZERLAND) 2023; 28:molecules28020660. [PMID: 36677714 PMCID: PMC9863657 DOI: 10.3390/molecules28020660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 01/03/2023] [Accepted: 01/05/2023] [Indexed: 01/11/2023]
Abstract
CAD is a 1.5 MDa hexameric protein with four enzymatic domains responsible for initiating de novo biosynthesis of pyrimidines nucleotides: glutaminase, carbamoyl phosphate synthetase, aspartate transcarbamoylase (ATC), and dihydroorotase. Despite its central metabolic role and implication in cancer and other diseases, our understanding of CAD is poor, and structural characterization has been frustrated by its large size and sensitivity to proteolytic cleavage. Recently, we succeeded in isolating intact CAD-like particles from the fungus Chaetomium thermophilum with high yield and purity, but their study by cryo-electron microscopy is hampered by the dissociation of the complex during sample grid preparation. Here we devised a specific crosslinking strategy to enhance the stability of this mega-enzyme. Based on the structure of the isolated C. thermophilum ATC domain, we inserted by site-directed mutagenesis two cysteines at specific locations that favored the formation of disulfide bridges and covalent oligomers. We further proved that this covalent linkage increases the stability of the ATC domain without damaging the structure or enzymatic activity. Thus, we propose that this cysteine crosslinking is a suitable strategy to strengthen the contacts between subunits in the CAD particle and facilitate its structural characterization.
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Affiliation(s)
| | | | - Santiago Ramón-Maiques
- Instituto de Biomedicina de Valencia (IBV), CSIC, Jaime Roig 11, 46010 Valencia, Spain
- Group CB06/07/0077 at the Instituto de Biomedicina de Valencia (IBV-CSIC) of CIBERER-ISCIII, Centro de Investigación Biomédica en Red de Enfermedades Raras, Melchor Fernández Almagro 3, 28029 Madrid, Spain
- Correspondence:
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5
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Ciesla J, Moreno I, Munger J. TNFα-induced metabolic reprogramming drives an intrinsic anti-viral state. PLoS Pathog 2022; 18:e1010722. [PMID: 35834576 PMCID: PMC9321404 DOI: 10.1371/journal.ppat.1010722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 07/26/2022] [Accepted: 07/01/2022] [Indexed: 11/22/2022] Open
Abstract
Cytokines induce an anti-viral state, yet many of the functional determinants responsible for limiting viral infection are poorly understood. Here, we find that TNFα induces significant metabolic remodeling that is critical for its anti-viral activity. Our data demonstrate that TNFα activates glycolysis through the induction of hexokinase 2 (HK2), the isoform predominantly expressed in muscle. Further, we show that glycolysis is broadly important for TNFα-mediated anti-viral defense, as its inhibition attenuates TNFα’s ability to limit the replication of evolutionarily divergent viruses. TNFα was also found to modulate the metabolism of UDP-sugars, which are essential precursor substrates for glycosylation. Our data indicate that TNFα increases the concentration of UDP-glucose, as well as the glucose-derived labeling of UDP-glucose and UDP-N-acetyl-glucosamine in a glycolytically-dependent manner. Glycolysis was also necessary for the TNFα-mediated accumulation of several glycosylated anti-viral proteins. Consistent with the importance of glucose-driven glycosylation, glycosyl-transferase inhibition attenuated TNFα’s ability to promote the anti-viral cell state. Collectively, our data indicate that cytokine-mediated metabolic remodeling is an essential component of the anti-viral response. Viral infection often activates a host cell’s intrinsic immune response resulting in the cellular secretion of cytokines, important host-defense molecules. These cytokines act on neighboring cells to make them less permissive to viral infection. Many of the mechanisms through which cytokines promote a less permissive cell state remain unclear. Our data indicate that treatment with the anti-viral cytokine TNFα induces substantial changes to cellular metabolic activity, including activating glucose metabolism. We find that these TNFα-induced metabolic changes are critical for TNFα to limit the replication of diverse viruses including Human Cytomegalovirus and two Coronaviruses, OC43 and SARS-CoV-2. Inhibition of glucose metabolism during TNFα treatment prevented the expression of a variety of known cellular anti-viral proteins. Collectively, our data indicate that cytokine-induced metabolic remodeling is an important component of TNFα’s ability to promote a less permissive cell state and raises further questions about the mechanisms through which specific cytokine-induced metabolic activities contribute to various aspects of anti-viral defense.
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Affiliation(s)
- Jessica Ciesla
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York, United States of America
| | - Isreal Moreno
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York, United States of America
| | - Joshua Munger
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York, United States of America
- * E-mail:
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6
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Wang C, Krüger A, Du X, Wrenger C, Groves MR. Novel Highlight in Malarial Drug Discovery: Aspartate Transcarbamoylase. Front Cell Infect Microbiol 2022; 12:841833. [PMID: 35310840 PMCID: PMC8931299 DOI: 10.3389/fcimb.2022.841833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 02/15/2022] [Indexed: 11/16/2022] Open
Abstract
Malaria remains one of the most prominent and dangerous tropical diseases. While artemisinin and analogs have been used as first-line drugs for the past decades, due to the high mutational rate and rapid adaptation to the environment of the parasite, it remains urgent to develop new antimalarials. The pyrimidine biosynthesis pathway plays an important role in cell growth and proliferation. Unlike human host cells, the malarial parasite lacks a functional pyrimidine salvage pathway, meaning that RNA and DNA synthesis is highly dependent on the de novo synthesis pathway. Thus, direct or indirect blockage of the pyrimidine biosynthesis pathway can be lethal to the parasite. Aspartate transcarbamoylase (ATCase), catalyzes the second step of the pyrimidine biosynthesis pathway, the condensation of L-aspartate and carbamoyl phosphate to form N-carbamoyl aspartate and inorganic phosphate, and has been demonstrated to be a promising target both for anti-malaria and anti-cancer drug development. This is highlighted by the discovery that at least one of the targets of Torin2 – a potent, yet unselective, antimalarial – is the activity of the parasite transcarbamoylase. Additionally, the recent discovery of an allosteric pocket of the human homology raises the intriguing possibility of species selective ATCase inhibitors. We recently exploited the available crystal structures of the malarial aspartate transcarbamoylase to perform a fragment-based screening to identify hits. In this review, we summarize studies on the structure of Plasmodium falciparum ATCase by focusing on an allosteric pocket that supports the catalytic mechanisms.
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Affiliation(s)
- Chao Wang
- Department of Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, Netherlands
| | - Arne Krüger
- Unit for Drug Discovery, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Xiaochen Du
- Department of Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, Netherlands
| | - Carsten Wrenger
- Unit for Drug Discovery, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
- *Correspondence: Matthew R. Groves, ; Carsten Wrenger,
| | - Matthew R. Groves
- Department of Drug Design, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, Netherlands
- *Correspondence: Matthew R. Groves, ; Carsten Wrenger,
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7
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Del Caño-Ochoa F, Ramón-Maiques S. Deciphering CAD: Structure and function of a mega-enzymatic pyrimidine factory in health and disease. Protein Sci 2021; 30:1995-2008. [PMID: 34288185 PMCID: PMC8442968 DOI: 10.1002/pro.4158] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 07/12/2021] [Accepted: 07/13/2021] [Indexed: 11/17/2022]
Abstract
CAD is a 1.5 MDa particle formed by hexameric association of a 250 kDa protein divided into different enzymatic domains, each catalyzing one of the initial reactions for de novo biosynthesis of pyrimidine nucleotides: glutaminase‐dependent Carbamoyl phosphate synthetase, Aspartate transcarbamoylase, and Dihydroorotase. The pathway for de novo pyrimidine synthesis is essential for cell proliferation and is conserved in all living organisms, but the covalent linkage of the first enzymatic activities into a multienzymatic CAD particle is unique to animals. In other organisms, these enzymatic activities are encoded as monofunctional proteins for which there is abundant structural and biochemical information. However, the knowledge about CAD is scarce and fragmented. Understanding CAD requires not only to determine the three‐dimensional structures and define the catalytic and regulatory mechanisms of the different enzymatic domains, but also to comprehend how these domains entangle and work in a coordinated and regulated manner. This review summarizes significant progress over the past 10 years toward the characterization of CAD's architecture, function, regulatory mechanisms, and cellular compartmentalization, as well as the recent finding of a new and rare neurometabolic disorder caused by defects in CAD activities.
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Affiliation(s)
- Francisco Del Caño-Ochoa
- Instituto de Biomedicina de Valencia (IBV-CSIC), Valencia, Spain.,Group 739, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) - Instituto de Salud Carlos III, Valencia, Spain
| | - Santiago Ramón-Maiques
- Instituto de Biomedicina de Valencia (IBV-CSIC), Valencia, Spain.,Group 739, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) - Instituto de Salud Carlos III, Valencia, Spain
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8
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Braun LM, Lagies S, Guenzle J, Fichtner-Feigl S, Wittel UA, Kammerer B. Metabolic Adaptation during nab-Paclitaxel Resistance in Pancreatic Cancer Cell Lines. Cells 2020; 9:cells9051251. [PMID: 32438599 PMCID: PMC7290296 DOI: 10.3390/cells9051251] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 05/05/2020] [Accepted: 05/15/2020] [Indexed: 12/13/2022] Open
Abstract
Pancreatic ductal adenocarcinoma (PDAC) correlates with high mortality and is about to become one of the major reasons for cancer-related mortality in the next decades. One reason for that high mortality is the limited availability of effective chemotherapy as well as the intrinsic or acquired resistance against it. Here, we report the impact of nab-paclitaxel on the cellular metabolome of PDAC cell lines. After establishment of nab-paclitaxel resistant cell lines, comparison of parental and resistant PDAC cell lines by metabolomics and biochemical assessments revealed altered metabolism, enhanced viability and reduced apoptosis. The results unveiled that acute nab-paclitaxel treatment affected primary metabolism to a minor extent. However, acquisition of resistance led to altered metabolites in both cell lines tested. Specifically, aspartic acid and carbamoyl-aspartic acid were differentially abundant, which might indicate an increased de novo pyrimidine synthesis. This pathway has already shown a similar behavior in other cancerous entities and thus might serve in the future as vulnerable target fighting resistance acquisition occurring in common malignancies.
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Affiliation(s)
- Lukas M. Braun
- Center for Biological Systems Analysis ZBSA, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany; (L.M.B.); (S.L.)
- Department of General- and Visceral Surgery, University of Freiburg Medical Center Faculty of Medicine, 79106 Freiburg, Germany; (J.G.); (S.F.-F.)
| | - Simon Lagies
- Center for Biological Systems Analysis ZBSA, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany; (L.M.B.); (S.L.)
- Spemann Graduate School of Biology and Medicine, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
- Institute of Biology II, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
| | - Jessica Guenzle
- Department of General- and Visceral Surgery, University of Freiburg Medical Center Faculty of Medicine, 79106 Freiburg, Germany; (J.G.); (S.F.-F.)
| | - Stefan Fichtner-Feigl
- Department of General- and Visceral Surgery, University of Freiburg Medical Center Faculty of Medicine, 79106 Freiburg, Germany; (J.G.); (S.F.-F.)
| | - Uwe A. Wittel
- Department of General- and Visceral Surgery, University of Freiburg Medical Center Faculty of Medicine, 79106 Freiburg, Germany; (J.G.); (S.F.-F.)
- Correspondence: (U.A.W.); (B.K.); Tel.: +49-761-270-25090 (U.A.W.); +49-761-203-97137 (B.K.)
| | - Bernd Kammerer
- Center for Biological Systems Analysis ZBSA, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany; (L.M.B.); (S.L.)
- Spemann Graduate School of Biology and Medicine, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
- Correspondence: (U.A.W.); (B.K.); Tel.: +49-761-270-25090 (U.A.W.); +49-761-203-97137 (B.K.)
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9
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Bosch SS, Lunev S, Batista FA, Linzke M, Kronenberger T, Dömling ASS, Groves MR, Wrenger C. Molecular Target Validation of Aspartate Transcarbamoylase from Plasmodium falciparum by Torin 2. ACS Infect Dis 2020; 6:986-999. [PMID: 32129597 DOI: 10.1021/acsinfecdis.9b00411] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Malaria is a tropical disease that kills about half a million people around the world annually. Enzymatic reactions within pyrimidine biosynthesis have been proven to be essential for Plasmodium proliferation. Here we report on the essentiality of the second enzymatic step of the pyrimidine biosynthesis pathway, catalyzed by aspartate transcarbamoylase (ATC). Crystallization experiments using a double mutant ofPlasmodium falciparum ATC (PfATC) revealed the importance of the mutated residues for enzyme catalysis. Subsequently, this mutant was employed in protein interference assays (PIAs), which resulted in inhibition of parasite proliferation when parasites transfected with the double mutant were cultivated in medium lacking an excess of nutrients, including aspartate. Addition of 5 or 10 mg/L of aspartate to the minimal medium restored the parasites' normal growth rate. In vitro and whole-cell assays in the presence of the compound Torin 2 showed inhibition of specific activity and parasite growth, respectively. In silico analyses revealed the potential binding mode of Torin 2 to PfATC. Furthermore, a transgenic ATC-overexpressing cell line exhibited a 10-fold increased tolerance to Torin 2 compared with control cultures. Taken together, our results confirm the antimalarial activity of Torin 2, suggesting PfATC as a target of this drug and a promising target for the development of novel antimalarials.
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Affiliation(s)
- Soraya S. Bosch
- Unit for Drug Discovery, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes 1374, 05508-000 São Paulo-SP, Brazil
- Structural Biology Unit, XB20 Drug Design, Department of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9700 AD Groningen, The Netherlands
| | - Sergey Lunev
- Structural Biology Unit, XB20 Drug Design, Department of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9700 AD Groningen, The Netherlands
| | - Fernando A. Batista
- Structural Biology Unit, XB20 Drug Design, Department of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9700 AD Groningen, The Netherlands
| | - Marleen Linzke
- Unit for Drug Discovery, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes 1374, 05508-000 São Paulo-SP, Brazil
| | - Thales Kronenberger
- Department of Internal Medicine VIII, University Hospital Tübingen, Otfried-Müller-Strasse 14, 72076 Tübingen, Germany
| | - Alexander S. S. Dömling
- Structural Biology Unit, XB20 Drug Design, Department of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9700 AD Groningen, The Netherlands
| | - Matthew R. Groves
- Structural Biology Unit, XB20 Drug Design, Department of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9700 AD Groningen, The Netherlands
| | - Carsten Wrenger
- Unit for Drug Discovery, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes 1374, 05508-000 São Paulo-SP, Brazil
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10
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Del Caño-Ochoa F, Moreno-Morcillo M, Ramón-Maiques S. CAD, A Multienzymatic Protein at the Head of de Novo Pyrimidine Biosynthesis. Subcell Biochem 2020; 93:505-538. [PMID: 31939163 DOI: 10.1007/978-3-030-28151-9_17] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
CAD is a 1.5 MDa particle formed by hexameric association of a 250 kDa protein that carries the enzymatic activities for the first three steps in the de novo biosynthesis of pyrimidine nucleotides: glutamine-dependent Carbamoyl phosphate synthetase, Aspartate transcarbamoylase and Dihydroorotase. This metabolic pathway is essential for cell growth and proliferation and is conserved in all living organisms. However, the fusion of the first three enzymatic activities of the pathway into a single multienzymatic protein only occurs in animals. In prokaryotes, by contrast, these activities are encoded as distinct monofunctional enzymes that function independently or by forming more or less transient complexes. Whereas the structural information about these enzymes in bacteria is abundant, the large size and instability of CAD has only allowed a fragmented characterization of its structure. Here we retrace some of the most significant efforts to decipher the architecture of CAD and to understand its catalytic and regulatory mechanisms.
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Affiliation(s)
- Francisco Del Caño-Ochoa
- Department of Genome Dynamics and Function, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolas Cabrera 1, 28049, Madrid, Spain
| | - María Moreno-Morcillo
- Department of Genome Dynamics and Function, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolas Cabrera 1, 28049, Madrid, Spain
| | - Santiago Ramón-Maiques
- Department of Genome Dynamics and Function, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolas Cabrera 1, 28049, Madrid, Spain.
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11
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Del Caño-Ochoa F, Ramón-Maiques S. The multienzymatic protein CAD leading the de novo biosynthesis of pyrimidines localizes exclusively in the cytoplasm and does not translocate to the nucleus. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2020; 39:1320-1334. [PMID: 31997698 DOI: 10.1080/15257770.2019.1706743] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
CAD, the multienzymatic protein that initiates and controls the de novo biosynthesis of pyrimidines, plays a major role in nucleotide homeostasis, cell growth and proliferation. Despite its interest as a potential antitumoral target, there is a lack of understanding on CAD's structure and functioning mechanisms. Although mainly identified as a cytosolic complex, different studies support the translocation of CAD into the nucleus, where it could have a yet undefined function. Here, we track the subcellular localization of CAD by using fluorescent chimeras, cell fractionation and immunoblotting with specific antibodies. Contradicting previous studies, we demonstrate that CAD is exclusively localized at the cytosol and discard a possible translocation to the nucleus.
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Affiliation(s)
- Francisco Del Caño-Ochoa
- Genome Dynamics and Function Program, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain
| | - Santiago Ramón-Maiques
- Genome Dynamics and Function Program, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain
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12
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Lei Z, Wang B, Lu Z, Wang N, Tan H, Zheng J, Jia Z. New regulatory mechanism-based inhibitors of aspartate transcarbamoylase for potential anticancer drug development. FEBS J 2020; 287:3579-3599. [PMID: 31967710 DOI: 10.1111/febs.15220] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 01/06/2020] [Accepted: 01/17/2020] [Indexed: 11/27/2022]
Abstract
Aspartate transcarbamoylase (ATCase) is a key enzyme which regulates and catalyzes the second step of de novo pyrimidine synthesis in all organisms. Escherichia coli ATCase is a prototypic enzyme regulated by both product feedback and substrate cooperativity, whereas human ATCase is a potential anticancer target. Through structural and biochemical analyses, we revealed that R167/130's loop region in ATCase serves as a gatekeeper for the active site, playing a new and unappreciated regulatory role in the catalytic cycle of ATCase. Based on virtual compound screening simultaneously targeting the new regulatory region and active site of human ATCase, two compounds were identified to exhibit strong inhibition of ATCase activity, proliferation of multiple cancer cell lines, and growth of xenograft tumors. Our work has not only revealed a previously unknown regulatory region of ATCase that helps uncover the catalytic and regulatory mechanism of ATCase, but also successfully guided the identification of new ATCase inhibitors for anticancer drug development using a dual-targeting strategy. DATABASE: Structure data are available in Protein Data Bank under the accession numbers: 6KJ7 (G166P ecATCase), 6KJ8 (G166P ecATCase-holo), 6KJ9 (G128/130A ecATCase), and 6KJA (G128/130A ecATCase-holo).
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Affiliation(s)
- Zhen Lei
- College of Chemistry, Beijing Normal University, China
| | - Biying Wang
- College of Chemistry, Beijing Normal University, China
| | - Zhifang Lu
- College of Chemistry, Beijing Normal University, China
| | - Nan Wang
- College of Chemistry, Beijing Normal University, China.,Jiangsu Key Laboratory of Brain Disease Bioinformation, Research Center for Biochemistry and Molecular Biology, Xuzhou Medical University, China
| | - Hongwei Tan
- College of Chemistry, Beijing Normal University, China
| | - Jimin Zheng
- College of Chemistry, Beijing Normal University, China
| | - Zongchao Jia
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada
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13
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Okesli-Armlovich A, Gupta A, Jimenez M, Auld D, Liu Q, Bassik MC, Khosla C. Discovery of small molecule inhibitors of human uridine-cytidine kinase 2 by high-throughput screening. Bioorg Med Chem Lett 2019; 29:2559-2564. [PMID: 31420268 DOI: 10.1016/j.bmcl.2019.08.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Revised: 08/03/2019] [Accepted: 08/05/2019] [Indexed: 12/11/2022]
Abstract
Clinically relevant inhibitors of dihydroorotate dehydrogenase (DHODH), a rate-limiting enzyme in mammalian de novo pyrimidine synthesis, have strong antiviral and anticancer activity in vitro. However, they are ineffective in vivo due to efficient uridine salvage by infected or rapidly dividing cells. The pyrimidine salvage enzyme uridine-cytidine kinase 2 (UCK2), a ∼29 kDa protein that forms a tetramer in its active state, is necessary for uridine salvage. Notwithstanding the pharmacological potential of this target, no medicinally tractable inhibitors of the human enzyme have been reported to date. We therefore established and miniaturized an in vitro assay for UCK2 activity and undertook a high-throughput screen against a ∼40,000-compound library to generate drug-like leads. The structures, activities, and modes of inhibition of the most promising hits are described. Notably, our screen yielded non-competitive UCK2 inhibitors which were able to suppress nucleoside salvage in cells both in the presence and absence of DHODH inhibitors.
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Affiliation(s)
- Ayse Okesli-Armlovich
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA; Stanford ChEM-H, Stanford, CA 94305, USA
| | - Amita Gupta
- Stanford ChEM-H, Stanford, CA 94305, USA; Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Marta Jimenez
- Facilitated Access to Screening Technologies (FAST) Laboratory, Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Douglas Auld
- Facilitated Access to Screening Technologies (FAST) Laboratory, Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Qi Liu
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA; Stanford ChEM-H, Stanford, CA 94305, USA
| | - Michael C Bassik
- Stanford ChEM-H, Stanford, CA 94305, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Chaitan Khosla
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA; Stanford ChEM-H, Stanford, CA 94305, USA; Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA.
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14
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Ruiz-Ramos A, Velázquez-Campoy A, Grande-García A, Moreno-Morcillo M, Ramón-Maiques S. Structure and Functional Characterization of Human Aspartate Transcarbamoylase, the Target of the Anti-tumoral Drug PALA. Structure 2016; 24:1081-94. [PMID: 27265852 DOI: 10.1016/j.str.2016.05.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/03/2016] [Accepted: 05/03/2016] [Indexed: 01/30/2023]
Abstract
CAD, the multienzymatic protein that initiates and controls de novo synthesis of pyrimidines in animals, associates through its aspartate transcarbamoylase (ATCase) domain into particles of 1.5 MDa. Despite numerous structures of prokaryotic ATCases, we lack structural information on the ATCase domain of CAD. Here, we report the structure and functional characterization of human ATCase, confirming the overall similarity with bacterial homologs. Unexpectedly, human ATCase exhibits cooperativity effects that reduce the affinity for the anti-tumoral drug PALA. Combining structural, mutagenic, and biochemical analysis, we identified key elements for the necessary regulation and transmission of conformational changes leading to cooperativity between subunits. Mutation of one of these elements, R2024, was recently found to cause the first non-lethal CAD deficit. We reproduced this mutation in human ATCase and measured its effect, demonstrating that this arginine is part of a molecular switch that regulates the equilibrium between low- and high-affinity states for the ligands.
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Affiliation(s)
- Alba Ruiz-Ramos
- Structural Bases of Genome Integrity Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fdez. Almagro, 3, Madrid 28029, Spain
| | - Adrián Velázquez-Campoy
- Institute of Biocomputation and Physics of Complex Systems (BIFI), Joint Unit IQFR-CSIC-BIFI, Universidad de Zaragoza, 50018 Zaragoza, Spain; Department of Biochemistry and Molecular and Cell Biology, Universidad de Zaragoza, 50009 Zaragoza, Spain; Aragon Institute for Health Research (IIS Aragon), 50009 Zaragoza, Spain; Fundacion ARAID, Government of Aragon, 50018 Zaragoza, Spain
| | - Araceli Grande-García
- Structural Bases of Genome Integrity Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fdez. Almagro, 3, Madrid 28029, Spain
| | - María Moreno-Morcillo
- Structural Bases of Genome Integrity Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fdez. Almagro, 3, Madrid 28029, Spain
| | - Santiago Ramón-Maiques
- Structural Bases of Genome Integrity Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fdez. Almagro, 3, Madrid 28029, Spain.
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Scherer PE. The Multifaceted Roles of Adipose Tissue-Therapeutic Targets for Diabetes and Beyond: The 2015 Banting Lecture. Diabetes 2016; 65:1452-61. [PMID: 27222389 PMCID: PMC4878420 DOI: 10.2337/db16-0339] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 03/28/2016] [Indexed: 12/29/2022]
Abstract
The Banting Medal for Scientific Achievement is the highest scientific award of the American Diabetes Association (ADA). Given in memory of Sir Frederick Banting, one of the key investigators in the discovery of insulin, the Banting Medal is awarded annually for scientific excellence, recognizing significant long-term contributions to the understanding, treatment, or prevention of diabetes. Philipp E. Scherer, PhD, of the Touchstone Diabetes Center, The University of Texas Southwestern Medical Center, Dallas, TX, received the prestigious award at the ADA's 75th Scientific Sessions, 5-9 June 2015, in Boston, MA. He presented the Banting Lecture, "The Multifaceted Roles of Adipose Tissue-Therapeutic Targets for Diabetes and Beyond," on Sunday, 7 June 2015.A number of different cell types contribute to the cellular architecture of adipose tissue. Although the adipocyte is functionally making important contributions to systemic metabolic homeostatis, several additional cell types contribute a supportive role to bestow maximal flexibility on the tissue with respect to many biosynthetic and catabolic processes, depending on the metabolic state. These cells include vascular endothelial cells, a host of immune cells, and adipocyte precursor cells and fibroblasts. Combined, these cell types give rise to a tissue with remarkable flexibility with respect to expansion and contraction, while optimizing the ability of the tissue to act as an endocrine organ through the release of many protein factors, critically influencing systemic lipid homeostasis and biochemically contributing many metabolites. Using an example from each of these categories-adiponectin as a key adipokine, sphingolipids as critical mediators of insulin sensitivity, and uridine as an important metabolite contributed by the adipocyte to the systemic pool-I will discuss the emerging genesis of the adipocyte over the past 20 years from metabolic bystander to key driver of metabolic flexibility.
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Affiliation(s)
- Philipp E Scherer
- Touchstone Diabetes Center, The University of Texas Southwestern Medical Center, Dallas, TX
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16
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Ruiz-Ramos A, Lallous N, Grande-García A, Ramón-Maiques S. Expression, purification, crystallization and preliminary X-ray diffraction analysis of the aspartate transcarbamoylase domain of human CAD. Acta Crystallogr Sect F Struct Biol Cryst Commun 2013; 69:1425-30. [PMID: 24316846 PMCID: PMC3855736 DOI: 10.1107/s1744309113031114] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 11/12/2013] [Indexed: 11/10/2022]
Abstract
Aspartate transcarbamoylase (ATCase) catalyzes the synthesis of N-carbamoyl-L-aspartate from carbamoyl phosphate and aspartate in the second step of the de novo biosynthesis of pyrimidines. In prokaryotes, the first three activities of the pathway, namely carbamoyl phosphate synthetase (CPSase), ATCase and dihydroorotase (DHOase), are encoded as distinct proteins that function independently or in noncovalent association. In animals, CPSase, ATCase and DHOase are part of a 243 kDa multifunctional polypeptide named CAD. Up-regulation of CAD is essential for normal and tumour cell proliferation. Although the structures of numerous prokaryotic ATCases have been determined, there is no structural information about any eukaryotic ATCase. In fact, the only detailed structural information about CAD is that it self-assembles into hexamers and trimers through interactions of the ATCase domains. Here, the expression, purification and crystallization of the ATCase domain of human CAD is reported. The recombinant protein, which was expressed in bacteria and purified with good yield, formed homotrimers in solution. Crystallization experiments both in the absence and in the presence of the inhibitor PALA yielded small crystals that diffracted X-rays to 2.1 Å resolution using synchrotron radiation. The crystals appeared to belong to the hexagonal space group P6(3)22, and Matthews coefficient calculation indicated the presence of one ATCase subunit per asymmetric unit, with a solvent content of 48%. However, analysis of the intensity statistics suggests a special case of the P21 lattice with pseudo-symmetry and possibly twinning.
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Affiliation(s)
- Alba Ruiz-Ramos
- Structural Bases of Genome Integrity Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Nada Lallous
- Structural Bases of Genome Integrity Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Araceli Grande-García
- Structural Bases of Genome Integrity Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Santiago Ramón-Maiques
- Structural Bases of Genome Integrity Group, Structural Biology and Biocomputing Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029 Madrid, Spain
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Shen L, Nishioka T, Guo J, Chen C. Geminin functions downstream of p53 in K-ras-induced gene amplification of dihydrofolate reductase. Cancer Res 2012; 72:6153-62. [PMID: 23026135 DOI: 10.1158/0008-5472.can-12-1862] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
DNA strand breakage and perturbation of cell-cycle progression contribute to gene amplification events that can drive cancer. In cells lacking p53, DNA damage does not trigger an effective cell-cycle arrest and in this setting promotes gene amplification. This is also increased in cells harboring oncogenic Ras, in which cell-cycle arrest is perturbed and ROS levels that cause DNA single strand breaks are elevated. This study focused on the effects of v-K-ras and p53 on Methotrexate (MTX)-mediated DHFR amplification. Rat lung epithelial cells expressing v-K-ras or murine lung cancer LKR cells harboring active K-ras continued cell-cycle progression when treated with MTX. However, upon loss of p53, amplification of DHFR and formation of MTX-resistant colonies occurred. Expression levels of cyclin A, Geminin, and Cdt1 were increased in v-K-ras transfectants. Geminin was sufficient to prevent the occurrence of multiple replications via interaction with Cdt1 after MTX treatment, and DHFR amplification proceeded in v-K-ras transfectants that possess a functional p53 in the absence of geminin. Taken together, our findings indicate that p53 not only regulates cell-cycle progression, but also functions through geminin to prevent DHFR amplification and protect genomic integrity.
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Affiliation(s)
- Ling Shen
- Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
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18
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Banerjee AK, Arora N, Murty USN. Aspartate carbamoyltransferase of Plasmodium falciparum as a potential drug target for designing anti-malarial chemotherapeutic agents. Med Chem Res 2012. [DOI: 10.1007/s00044-011-9757-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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N-(phosphonacetyl)-L-aspartate induces TAp73-dependent apoptosis by modulating multiple Bcl-2 proteins: potential for cancer therapy. Oncogene 2012; 32:920-9. [PMID: 22430213 PMCID: PMC3382011 DOI: 10.1038/onc.2012.96] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
p53 is essential for the cellular responses to DNA damage that help to maintain genomic stability. However, the great majority of human cancers undergo disruption of the p53-network. Identification and characterization of molecular components important in both p53-dependent and -independent apoptosis might be useful in developing novel therapies for cancers. In the complete absence of p53, cells treated with N-(phosphonacetyl)-L-aspartate (PALA) continue to synthesize DNA slowly and eventually progress through S phase, suffering severe DNA damage that in turn triggers apoptosis, whereas cells with functional p53 undergo growth arrest. In the present study, we investigated apoptotic signaling in response to PALA and the role of p53 expression in this pathway. We found that treatment of cells lacking p53 with PALA induced TAp73, Noxa, and Bim and inactivation of these proteins with dominant negative plasmids or siRNAs significantly inhibited apoptosis, suggesting that PALA-induced apoptosis was mediated via TAp73-dependent expression of Noxa and Bim. However, PALA treatment inhibited the expression of ΔNp73 only in cells lacking p53 but not in cells expressing p53. In addition, PALA treatment inhibited Bcl-2, and overexpression of Bcl-2 significantly inhibited PALA-induced apoptosis. Moreover, expression of p53 in these cells protected them from PALA-induced apoptosis by activating p21, sustaining the expression of ΔNp73 and inhibiting the induction of Noxa and Bim. Taken together, our study identifies novel but opposing roles for the p53 and TAp73 in the induction of Noxa and Bim and regulation of apoptosis. Our data will help to develop strategies to eliminate cancer cells lacking p53 while protecting normal cells with wild-type p53.
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Le Calvez PB, Scott CJ, Migaud ME. Multisubstrate adduct inhibitors: drug design and biological tools. J Enzyme Inhib Med Chem 2010; 24:1291-318. [PMID: 19912064 DOI: 10.3109/14756360902843809] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In drug discovery, different methods exist to create new inhibitors possessing satisfactory biological activity. The multisubstrate adduct inhibitor (MAI) approach is one of these methods, which consists of a covalent combination between analogs of the substrate and the cofactor or of the multiple substrates used by the target enzyme. Adopted as the first line of investigation for many enzymes, this method has brought insights into the enzymatic mechanism, structure, and inhibitory requirements. In this review, the MAI approach, applied to different classes of enzyme, is reported from the point of view of biological activity.
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Heath TD, Brown CS. Liposome Dependent Delivery of N-(Phosphonacetyl)-L-Aspartic Acid to Cellsin Vitro. J Liposome Res 2008. [DOI: 10.3109/08982108909035999] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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22
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DNA synthesis from unbalanced nucleotide pools causes limited DNA damage that triggers ATR-CHK1-dependent p53 activation. Proc Natl Acad Sci U S A 2008; 105:6314-9. [PMID: 18434539 DOI: 10.1073/pnas.0802080105] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
p53-dependent G(1) and G(2) cell cycle checkpoints are activated in response DNA damage that help to maintain genomic stability. p53 also helps to protect cells from damage that occurs during S phase, for example, when the cells are starved for DNA precursors or irradiated with a low dose of UV. p53 is activated in normal cells starved for pyrimidine nucleotides by treatment with N-(phosphonacetyl)-l-aspartate (PALA). The treated cells progress through a first S phase with kinetics similar to those of untreated cells. However, the DNA of the treated cells begins to become damaged rapidly, within 12 h, as revealed by a comet assay, which detects broken DNA, and by staining for phosphorylated histone H2AX, which accumulates at sites of DNA damage. Because the cells survive, the damage must be reversible, suggesting single-strand breaks or gaps as the most likely possibility. The transiently damaged DNA stimulates activation of ATR and CHK1, which in turn catalyze the phosphorylation and accumulation of p53. Although PALA-induced DNA damage occurs only in dividing cells, the p53 that is activated is only competent to transcribe genes such as p21 and macrophage inhibitory cytokine 1 (whose products regulate G(2) and G(1) or S phase checkpoints, respectively) after the cells have exited the S phase during which damage occurs. We propose that p53 is activated by stimulation of mismatch repair in response to the misincorporation of deoxynucleotides into newly synthesized DNA, long before the lack of pyrimidine nucleoside triphosphates causes the rate of DNA synthesis to slow appreciably.
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Eldo J, Heng S, Kantrowitz ER. Design, synthesis, and bioactivity of novel inhibitors of E. coli aspartate transcarbamoylase. Bioorg Med Chem Lett 2006; 17:2086-90. [PMID: 17336518 PMCID: PMC1930159 DOI: 10.1016/j.bmcl.2006.12.050] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Revised: 12/12/2006] [Accepted: 12/13/2006] [Indexed: 10/23/2022]
Abstract
A series of inhibitors of the aspartate transcarbamoylase, an enzyme involved in pyrimidine nucleotide biosynthesis, has been synthesized. These inhibitors are analogues of a highly potent inhibitor of this enzyme, N-phosphonacetyl-L-aspartate (PALA). Analogues have been synthesized with modifications at the alpha- and beta-carboxylates as well as at the aspartate moiety. The ability of these compounds to inhibit the enzyme was evaluated. These studies, with functional group modified PALA derivatives, showed that amide groups can be a useful substitute of the carboxylate in order to reduce the charge on the molecule, and indicate that the relative position of the functional group in the beta-position is more critical than the nature of the functional group. Some of the molecules synthesized here are potent inhibitors of the enzyme.
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Agarwal MK, Hastak K, Jackson MW, Breit SN, Stark GR, Agarwal ML. Macrophage inhibitory cytokine 1 mediates a p53-dependent protective arrest in S phase in response to starvation for DNA precursors. Proc Natl Acad Sci U S A 2006; 103:16278-83. [PMID: 17050687 PMCID: PMC1637573 DOI: 10.1073/pnas.0607210103] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
p53 is essential for the cellular responses to DNA damage that help to maintain genomic stability. Protective p53-dependent cell-cycle checkpoints are activated in response to a wide variety of stresses, including not only DNA damage but also arrest of DNA synthesis and of mitosis. In addition to its role in activating the G(1) and G(2) checkpoints, p53 also helps to protect cells in S phase when they are starved for DNA precursors by treatment with the specific aspartate transcarbamylase inhibitor N-phosphonacetyl-l-aspartate (PALA), which blocks the synthesis of pyrimidine nucleotides. Even though p53 is activated, PALA-treated cells expressing low levels of p53 or lacking expression of p21 do not arrest in G(1) or G(2) but are blocked in S phase instead. In the complete absence of p53, PALA-treated cells continue to synthesize DNA slowly and eventually progress through S phase, suffering severe DNA damage that in turn triggers apoptosis. Expression of the secreted protein macrophage inhibitory cytokine 1 (MIC-1), a member of the TGF-beta superfamily, increases substantially after PALA treatment, and application of exogenous MIC-1 or its constitutive expression from a cDNA provides remarkable protection of p53-null cells from PALA-mediated apoptosis, arguing that the p53-dependent secretion of MIC-1 provides a major part of such protection. Stimulation of MIC-1-dependent S phase arrest in normal gut epithelial cells might help to revitalize the clinical use of PALA, which has been limited by gut toxicity.
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Affiliation(s)
- Mukesh K Agarwal
- Department of Genetics, Case Western Reserve University, Cleveland, OH 44106, USA.
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25
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Heng S, Stieglitz KA, Eldo J, Xia J, Cardia JP, Kantrowitz ER. T-state Inhibitors of E. coli Aspartate Transcarbamoylase that Prevent the Allosteric Transition,. Biochemistry 2006; 45:10062-71. [PMID: 16906764 DOI: 10.1021/bi0601095] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Escherichia coli aspartate transcarbamoylase (ATCase) catalyzes the committed step in pyrimidine nucleotide biosynthesis, the reaction between carbamoyl phosphate (CP) and l-aspartate to form N-carbamoyl-l-aspartate and inorganic phosphate. The enzyme exhibits homotropic cooperativity and is allosterically regulated. Upon binding l-aspartate in the presence of a saturating concentration of CP, the enzyme is converted from the low-activity low-affinity T state to the high-activity high-affinity R state. The potent inhibitor N-phosphonacetyl-l-aspartate (PALA), which combines the binding features of Asp and CP into one molecule, has been shown to induce the allosteric transition to the R state. In the presence of only CP, the enzyme is the T structure with the active site primed for the binding of aspartate. In a structure of the enzyme-CP complex (T(CP)), two CP molecules were observed in the active site approximately 7A apart, one with high occupancy and one with low occupancy. The high occupancy site corresponds to the position for CP observed in the structure of the enzyme with CP and the aspartate analogue succinate bound. The position of the second CP is in a unique site and does not overlap with the aspartate binding site. As a means to generate a new class of inhibitors for ATCase, the domain-open T state of the enzyme was targeted. We designed, synthesized, and characterized three inhibitors that were composed of two phosphonacetamide groups linked together. These two phosphonacetamide groups mimic the positions of the two CP molecules in the T(CP) structure. X-ray crystal structures of ATCase-inhibitor complexes revealed that each of these inhibitors bind to the T state of the enzyme and occupy the active site area. As opposed to the binding of Asp in the presence of CP or PALA, these inhibitors are unable to initiate the global T to R conformational change. Although the best of these T-state inhibitors only has a K(i) value in the micromolar range, the structural information with respect to their mode of binding provides important information for the design of second generation inhibitors that will have even higher affinity for the active site of the T state of the enzyme.
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Affiliation(s)
- Sabrina Heng
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA
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26
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Pfund E, Lequeux T, Masson S, Vazeux M, Cordi A, Pierre A, Serre V, Hervé G. Efficient synthesis of fluorothiosparfosic acid analogues with potential antitumoral activity. Bioorg Med Chem 2005; 13:4921-8. [PMID: 15975800 DOI: 10.1016/j.bmc.2005.05.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Revised: 05/17/2005] [Accepted: 05/20/2005] [Indexed: 11/26/2022]
Abstract
In this paper, we describe a short synthesis of N-(phosphonoacetyl)-L-aspartate (PALA) analogues. The mono- and difluorinated thioacetamide precursors were prepared in one step from methyl (diethoxyphosphono)di- and monofluoromethyldithioacetates 8 and 11 as starting materials. Antiproliferating properties on a L1210 strain and ATCase inhibition of these new compounds are disclosed. ThioPALA(FF) 5c showed a remarkable cytotoxic activity towards murine leukemia L1210, when used as tetraester.
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Affiliation(s)
- Emmanuel Pfund
- Laboratoire de Chimie Moléculaire et Thio-organique (UMR CNRS 6507), ENSICAEN-Université de Caen, 6 Boulevard Maréchal Juin, F-14050 Caen, France
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Wang J, Stieglitz KA, Cardia JP, Kantrowitz ER. Structural basis for ordered substrate binding and cooperativity in aspartate transcarbamoylase. Proc Natl Acad Sci U S A 2005; 102:8881-6. [PMID: 15951418 PMCID: PMC1157055 DOI: 10.1073/pnas.0503742102] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
X-ray structures of aspartate transcarbamoylase in the absence and presence of the first substrate carbamoyl phosphate are reported. These two structures in conjunction with in silico docking experiments provide snapshots of critical events in the function of the enzyme. The ordered substrate binding, observed experimentally, can now be structurally explained by a conformational change induced upon the binding of carbamoyl phosphate. This induced fit dramatically alters the electrostatics of the active site, creating a binding pocket for aspartate. Upon aspartate binding, a further change in electrostatics causes a second induced fit, the domain closure. This domain closure acts as a clamp that both facilitates catalysis by approximation and also initiates the global conformational change that manifests homotropic cooperativity.
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Affiliation(s)
- Jie Wang
- Department of Chemistry, Boston College, Merkert Chemistry Center, Chestnut Hill, MA 02467, USA
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Grison C, Coutrot P, Comoy C, Balas L, Joliez S, Lavecchia G, Oliger P, Penverne B, Serre V, Hervé G. Design, synthesis and activity of bisubstrate, transition-state analogues and competitive inhibitors of aspartate transcarbamylase. Eur J Med Chem 2004; 39:333-44. [PMID: 15072842 DOI: 10.1016/j.ejmech.2004.01.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2003] [Revised: 01/13/2004] [Accepted: 01/15/2004] [Indexed: 10/26/2022]
Abstract
Aspartate transcarbamylase initiates the de novo biosynthetic pathway for the production of the pyrimidine nucleotides, precursors of nucleic acids. This pathway is particularly active in rapidly growing cells and tissues. Thus, this enzyme has been tested as a potential target for antiproliferative drugs. In the present work, on the basis of its structural and mechanistic properties, a series of substrate analogues, including potential suicide-pseudosubstrates was synthesized and their putative inhibitory effects were tested using E. coli aspartate transcarbamylase as a model. Two of these compounds appear to be very efficient inhibitors of this enzyme.
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Affiliation(s)
- Claude Grison
- INCM FR CNRS 1742, UMR CNRS-UHP Nancy I 7565, Université Henri Poincaré, institut nanceien de chimie moléculaire, laboratoire de chimie organique biomoléculaire, Vandoeuvre-lès-Nancy, France.
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Huang J, Lipscomb WN. Aspartate transcarbamylase (ATCase) of Escherichia coli: a new crystalline R-state bound to PALA, or to product analogues citrate and phosphate. Biochemistry 2004; 43:6415-21. [PMID: 15157075 DOI: 10.1021/bi030213b] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Structures of the R-state of Escherichia coli ATCase maintained with carbamyl phosphate and succinate, phosphonoacetamide and malonate, or N-phosphonacetyl-l-aspartate (PALA) have previously been made in the space group P321, in which the two independent r (regulatory) and two independent c (catalytic) chains are repeated by crystallographic symmetry to yield the holoenzyme c(6)r(6), ((c(3))(2)(r(2))(3)). The exploration of a new crystalline R-state P2(1)2(1)2(1) was undertaken to examine the c(3).c(3) expansion of 11 A in the T-to-R transition, and to further test whether intermolecular contacts influence the binding of PALA. The results show that the expansion along the 3-fold axis is 10 A, and that the binding modes of the six crystallographic independent PALA molecules are virtually identical to one another, and to modes described previously. As further test, the PALA, a bisubstrate analogue, was displaced by citrate and phosphate, where citrate is an analogue of product carbamylaspartate. The results support the conclusions about the binding of the three previously studied analogues, and further support, within about 0.5 A, the structure proposed for the transition state [Gouaux, J. E., Krause, K. L., and Lipscomb, W. N. (1987) Biochem. Biophys. Res. Commun. 142, 893-897; Jin, L., Stec, B., Lipscomb, W. N., and Kantrowitz, E. R. (1999) Proteins: Struct., Funct., Genet. 37, 729-742].
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Affiliation(s)
- Jingwei Huang
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA
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Lemoine FJ, Marriott SJ. Genomic instability driven by the human T-cell leukemia virus type I (HTLV-I) oncoprotein, Tax. Oncogene 2002; 21:7230-4. [PMID: 12370813 DOI: 10.1038/sj.onc.1205898] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2002] [Revised: 07/11/2002] [Accepted: 08/06/2002] [Indexed: 11/08/2022]
Abstract
The importance of maintaining genomic stability is evidenced by the fact that transformed cells often contain a variety of chromosomal abnormalities such as euploidy, translocations, and inversions. Gene amplification is a well-characterized hallmark of genomic instability thought to result from recombination events following the formation of double-strand, chromosomal breaks. Therefore, gene amplification frequency serves as an indicator of genomic stability. The PALA assay is designed to measure directly the frequency with which a specific gene, CAD, is amplified within a cell's genome. We have used the PALA assay to analyse the effects of the human T-cell leukemia virus type I (HTLV-I) oncoprotein, Tax, on genomic amplification. We demonstrate that Tax-expressing cells are five-times more likely to undergo gene amplification than control cells. Additionally, we show that Tax alters the ability of cells to undergo the typical PALA-mediated G(1) phase cell cycle arrest, thereby allowing cells to replicate DNA in the absence of appropriate nucleotide pools. This effect is likely the mechanism by which Tax induces gene amplification. These data suggest that HTLV-I Tax alters the genomic stability of cells, an effect that may play an important role in Tax-mediated, HTLV-I associated cellular transformation.
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Affiliation(s)
- Francene J Lemoine
- Interdepartmental Program in Cell and Molecular Biology, Baylor College of Medicine, Houston, Texas, TX 77030, USA
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Sigoillot FD, Evans DR, Guy HI. Growth-dependent regulation of mammalian pyrimidine biosynthesis by the protein kinase A and MAPK signaling cascades. J Biol Chem 2002; 277:15745-51. [PMID: 11872754 DOI: 10.1074/jbc.m201112200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The carbamoyl phosphate synthetase domain of the multifunctional protein CAD catalyzes the initial, rate-limiting step in mammalian de novo pyrimidine biosynthesis. In addition to allosteric regulation by the inhibitor UTP and the activator PRPP, the carbamoyl phosphate synthetase activity is controlled by mitogen-activated protein kinase (MAPK)- and protein kinase A (PKA)-mediated phosphorylation. MAPK phosphorylation, both in vivo and in vitro, increases sensitivity to PRPP and decreases sensitivity to the inhibitor UTP, whereas PKA phosphorylation reduces the response to both allosteric effectors. To elucidate the factors responsible for growth state-dependent regulation of pyrimidine biosynthesis, the activity of the de novo pyrimidine pathway, the MAPK and PKA activities, the phosphorylation state, and the allosteric regulation of CAD were measured as a function of growth state. As cells entered the exponential growth phase, there was an 8-fold increase in pyrimidine biosynthesis that was accompanied by a 40-fold increase in MAPK activity and a 4-fold increase in CAD threonine phosphorylation. PRPP activation increased to 21-fold, and UTP became a modest activator. These changes were reversed when the cultures approach confluence and growth ceases. Moreover, CAD phosphoserine, a measure of PKA phosphorylation, increased 2-fold in confluent cells. These results are consistent with the activation of CAD by MAPK during periods of rapid growth and its down-regulation in confluent cells associated with decreased MAPK phosphorylation and a concomitant increase in PKA phosphorylation. A scheme is proposed that could account for growth-dependent regulation of pyrimidine biosynthesis based on the sequential action of MAPK and PKA on the carbamoyl phosphate synthetase activity of CAD.
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Affiliation(s)
- Frederic D Sigoillot
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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Mucciolo E, Bertoni L, Mondello C, Giulotto E. Late onset of CAD gene amplification in unamplified PALA resistant Chinese hamster mutants. Cancer Lett 2000; 150:119-27. [PMID: 10704733 DOI: 10.1016/s0304-3835(99)00289-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In rodent cells, resistance to PALA (N-phosphonacetyl-L-aspartate) has always been found associated with amplification of the CAD gene (carbamyl-P synthetase, aspartate transcarbamylase, dihydro-orotase). We describe two PALA resistant Chinese hamster mutant cell lines in which amplification of the CAD gene was not present. The PALA resistant phenotype was stable when the cells were grown in non-selective medium. However, after prolonged growth in the presence of the same drug concentration used for selection, cells with increased CAD gene copy number and higher levels of resistance overrode the original population. In these cell populations, a heterogeneous organization of the CAD genes was revealed by fluorescence in situ hybridization on mitotic chromosomes indicating that the additional copies of the gene were generated in several ways, such as non-disjunction and breakage-fusion-bridge cycles. The clastogenic effect of PALA, evidenced as chromosomal aberrations in the cells grown in the presence of the drug, could have favored the late onset of the amplified mutants. It is tempting to speculate that, during the expansion of tumor populations, different drug resistance mechanisms, including gene amplification, could occur in succession and lead to the generation of cells highly resistant to chemotherapeutic agents.
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Affiliation(s)
- E Mucciolo
- Dipartimento di Genetica e Microbiologia 'Adriano Buzzati Traverso' Via Abbiategrasso 207, 27100, Pavia, Italy
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Qiu Y, Davidson JN. Substitutions in the aspartate transcarbamoylase domain of hamster CAD disrupt oligomeric structure. Proc Natl Acad Sci U S A 2000; 97:97-102. [PMID: 10618377 PMCID: PMC26622 DOI: 10.1073/pnas.97.1.97] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Aspartate transcarbamoylase (ATCase; EC 2.1.3.2) is one of three enzymatic domains of CAD, a protein whose native structure is usually a hexamer of identical subunits. Alanine substitutions for the ATCase residues Asp-90 and Arg-269 were generated in a bicistronic vector that encodes a 6-histidine-tagged hamster CAD. Stably transfected mammalian cells expressing high levels of CAD were easily isolated and CAD purification was simplified over previous procedures. The substitutions reduce the ATCase V(max) of the altered CADs by 11-fold and 46-fold, respectively, as well as affect the enzyme's affinity for aspartate. At 25 mM Mg(2+), these substitutions cause the oligomeric CAD to dissociate into monomers. Under the same dissociating conditions, incubating the altered CAD with the ATCase substrate carbamoyl phosphate or the bisubstrate analogue N-phosphonacetyl-L-aspartate unexpectedly leads to the reformation of hexamers. Incubation with the other ATCase substrate, aspartate, has no effect. These results demonstrate that the ATCase domain is central to hexamer formation in CAD and suggest that the ATCase reaction mechanism is ordered in the same manner as the Escherichia coli ATCase. Finally, the data indicate that the binding of carbamoyl phosphate induces conformational changes that enhance the interaction of CAD subunits.
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Affiliation(s)
- Y Qiu
- Department of Microbiology, Albert B. Chandler Medical Center, University of Kentucky, Lexington, KY 40536-0084, USA
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Jin L, Stec B, Lipscomb WN, Kantrowitz ER. Insights into the mechanisms of catalysis and heterotropic regulation ofEscherichia coli aspartate transcarbamoylase based upon a structure of the enzyme complexed with the bisubstrate analogueN-phosphonacetyl-L-aspartate at 2.1 ? Proteins 1999. [DOI: 10.1002/(sici)1097-0134(19991201)37:4<729::aid-prot21>3.0.co;2-f] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Harte RJ, Matthews JC, O'Reilly SM, Tilsley DW, Osman S, Brown G, Luthra SJ, Brady F, Jones T, Price PM. Tumor, normal tissue, and plasma pharmacokinetic studies of fluorouracil biomodulation with N-phosphonacetyl-L-aspartate, folinic acid, and interferon alfa. J Clin Oncol 1999; 17:1580-8. [PMID: 10334547 DOI: 10.1200/jco.1999.17.5.1580] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PURPOSE To evaluate the effect of N-phosphonacetyl-L-aspartate (PALA), folinic acid (FA), and interferon alfa (IFN-alpha) biomodulation on plasma fluorouracil (5FU) pharmacokinetics and tumor and liver radioactivity uptake and retention after [18F]-fluorouracil (5-[18F]-FU) administration. PATIENTS AND METHODS Twenty-one paired pharmacokinetic studies were completed on patients with colorectal, gastric, and hepatocellular cancer, utilizing positron emission tomography (PET), which allowed the acquisition of tumor, normal tissue, and plasma pharmacokinetic data and tumor blood flow (TBF) measurements. The first PET study was completed when the patient was biomodulator-naive and was repeated on day 8 after the patient had been treated with either PALA, FA, or IFN-alpha in recognized schedules. RESULTS TBF was an important determinant of tumor radioactivity uptake (r = .90; P < .001) and retention (r = .96; P < .001), for which radioactivity represents a composite signal of 5-[18F]-FU and [18F]-labeled metabolites and catabolites. After treatment with PALA, TBF decreased (four of four patients; P = .043), as did tumor radioactivity exposure (five of five patients; P = .0437), with no change in plasma 5FU clearance. With FA treatment, there were no differences observed in whole-body metabolism, plasma 5FU clearance, or tumor and liver pharmacokinetics. IFN-alpha had measurable effects on TBF and 5-[18F]-FU metabolism but had no apparent affect on liver blood flow. CONCLUSION The administration of PALA and IFN-alpha produced measurable changes in plasma, tumor, and liver pharmacokinetics after 5-[18F]-FU administration. No changes were observed after FA administration. In vivo effects may negate the anticipated therapeutic advantage of 5FU biomodulation with some agents.
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Affiliation(s)
- R J Harte
- Medical Research Council, Cancer Research Campaign Positron Emission Tomography Research Group, Imperial College School of Medicine, London, United Kingdom
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36
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Burns BP, Mendz GL, Hazell SL. A novel mechanism for resistance to the antimetabolite N-phosphonoacetyl-L-aspartate by Helicobacter pylori. J Bacteriol 1998; 180:5574-9. [PMID: 9791105 PMCID: PMC107614 DOI: 10.1128/jb.180.21.5574-5579.1998] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/1998] [Accepted: 08/26/1998] [Indexed: 11/20/2022] Open
Abstract
The mechanism of resistance to N-phosphonoacetyl-L-aspartate (PALA), a potent inhibitor of aspartate carbamoyltransferase (which catalyzes the first committed step of de novo pyrimidine biosynthesis), in Helicobacter pylori was investigated. At a 1 mM concentration, PALA had no effects on the growth and viability of H. pylori. The inhibitor was taken up by H. pylori cells and the transport was saturable, with a Km of 14.8 mM and a Vmax of 19.1 nmol min-1 microliters of cell water-1. By 31P nuclear magnetic resonance (NMR) spectroscopy, both PALA and phosphonoacetate were shown to have been metabolized in all isolates of H. pylori studied. A main metabolic end product was identified as inorganic phosphate, suggesting the presence of an enzyme activity which cleaved the carbon-phosphorus (C-P) bonds. The kinetics of phosphonate group cleavage was saturable, and there was no evidence for substrate inhibition at higher concentrations of either compound. C-P bond cleavage activity was temperature dependent, and the activity was lost in the presence of the metal chelator EDTA. Other cleavages of PALA were observed by 1H NMR spectroscopy, with succinate and malate released as main products. These metabolic products were also formed when N-acetyl-L-aspartate was incubated with H. pylori lysates, suggesting the action of an aspartase. Studies of the cellular location of these enzymes revealed that the C-P bond cleavage activity was localized in the soluble fraction and that the aspartase activity appeared in the membrane-associated fraction. The results suggested that the two H. pylori enzymes transformed the inhibitor into noncytotoxic products, thus providing the bacterium with a mechanism of resistance to PALA toxicity which appears to be unique.
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Affiliation(s)
- B P Burns
- School of Microbiology and Immunology, University of New South Wales, Sydney 2052, Australia
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Paulson TG, Almasan A, Brody LL, Wahl GM. Gene amplification in a p53-deficient cell line requires cell cycle progression under conditions that generate DNA breakage. Mol Cell Biol 1998; 18:3089-100. [PMID: 9566927 PMCID: PMC110691 DOI: 10.1128/mcb.18.5.3089] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Amplification of genes involved in signal transduction and cell cycle control occurs in a significant fraction of human cancers. Loss of p53 function has been proposed to enable cells with gene amplification to arise spontaneously during growth in vitro. However, this conclusion derives from studies employing the UMP synthesis inhibitor N-phosphonacetyl-L-aspartate (PALA), which, in addition to selecting for cells containing extra copies of the CAD locus, enables p53-deficient cells to enter S phase and acquire the DNA breaks that initiate the amplification process. Thus, it has not been possible to determine if gene amplification occurs spontaneously or results from the inductive effects of the selective agent. The studies reported here assess whether p53 deficiency leads to spontaneous genetic instability by comparing cell cycle responses and amplification frequencies of the human fibrosarcoma cell line HT1080 when treated with PALA or with methotrexate, an antifolate that, under the conditions used, should not generate DNA breaks. p53-deficient HT1080 cells generated PALA-resistant variants containing amplified CAD genes at a frequency of >10(-5). By contrast, methotrexate selection did not result in resistant cells at a detectable frequency (<10(-9)). However, growth of HT1080 cells under conditions that induced DNA breakage prior to selection generated methotrexate-resistant clones containing amplified dihydrofolate reductase sequences at a high frequency. These data demonstrate that, under standard growth conditions, p53 loss is not sufficient to enable cells to produce the DNA breaks that initiate amplification. We propose that p53-deficient cells must proceed through S phase under conditions that induce DNA breakage for genetic instability to occur.
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Affiliation(s)
- T G Paulson
- Department of Biology, University of California, San Diego, La Jolla 92093, USA
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Burns BP, Mendz GL, Hazell SL. In situ properties of Helicobacter pylori aspartate carbamoyltransferase. Arch Biochem Biophys 1997; 347:119-25. [PMID: 9344472 DOI: 10.1006/abbi.1997.0328] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The kinetic and regulatory properties of aspartate carbamoyltransferase (ACTase) of the human pathogen Helicobacter pylori were studied in situ in cell-free extracts. The presence of enzyme activity was established by identifying the end product as carbamoylaspartate using nuclear magnetic resonance spectroscopy. Activity was measured in all strains studied, including recent clinical isolates. Substrate saturation curves determined employing radioactive tracer analysis or a microtiter colorimetric assay were hyperbolic for both carbamoyl phosphate and aspartate, and there was no evidence for substrate inhibition at higher concentrations of either substrate. The apparent Km were 0.6 and 11.6 mm for carbamoyl phosphate and aspartate, respectively. Optimal pH and temperature were determined as 8.0 and 45 degrees C. Activity was observed with the l- but not the d-isomer of aspartate. Succinate and maleate inhibited enzyme activity competitively with respect to aspartate. The carbamoyl phosphate analogues acetyl phosphate and phosphonoacetic acid inhibited activity in a competitive manner with respect to carbamoyl phosphate. With limiting carbamoyl phosphate purine and pyrimidine nucleotides, tripolyphosphate, pyrophosphate, and orthophosphate inhibited competitively at millimolar concentrations. Ribose and ribose 5-phosphate at 10 mm concentration showed 20 and 35% inhibition of enzyme activity, respectively. N-Phosphonoacetyl-l-aspartate (PALA) was the most potent inhibitor studied, with 50% inhibition of enzyme activity observed at 0.1 microM concentration. Inhibition by PALA was competitive with carbamoyl phosphate (Ki = 0.245 microM) and noncompetitive with aspartate. The kinetic and regulatory data on the activity of the H. pylori enzyme suggest it is a Class A ACTase, but with some interesting characteristics distinct from this class.
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Affiliation(s)
- B P Burns
- School of Microbiology and Immunology, University of New South Wales, Sydney, 2052, Australia
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Katsafanas GC, Grem JL, Blough HA, Moss B. Inhibition of vaccinia virus replication by N-(phosphonoacetyl)-L-aspartate: differential effects on viral gene expression result from a reduced pyrimidine nucleotide pool. Virology 1997; 236:177-87. [PMID: 9299630 DOI: 10.1006/viro.1997.8735] [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: 02/05/2023]
Abstract
The replication of vaccinia virus was reduced by 3 logs in cells that had been treated before and during infection with a concentration of N-(phosphonoacetyl)-L-aspartate (PALA) which lowered the UTP and CTP to 5 and 20% of controls, respectively, without affecting cell viability. The antiviral activity of PALA was reversed with uridine, indicating that it was entirely due to the diminution in pyrimidine nucleotides. Analysis of viral proteins revealed prolonged synthesis of some early stage species but a drastic reduction in late stage species, even though the nucleotide concentrations remained relatively constant throughout the infection. Although the gene expression pattern resembled that caused by a potent inhibitor of DNA synthesis, viral DNA accumulation was reduced by only 60%. Very little of the DNA made in the presence of PALA was converted to genome length molecules. The effect of PALA on transcription of early genes was complex: there was a twofold increase in the amount of a relatively short mRNA of 500 nucleotides but a two- to threefold decrease in the amount of a 4300-nucleotide mRNA encoding the largest subunit of RNA polymerase. In contrast, PALA severely inhibited the accumulation of viral intermediate and late stage mRNAs. The extreme sensitivity of vaccinia virus to PALA and the differential effects of the drug on viral gene expression result from the cascade mechanism of viral gene regulation.
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Affiliation(s)
- G C Katsafanas
- Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892-0445, USA
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Morris AD, Cordi AA. A New, Efficient, Two Step Procedure for the Preparation of the Antineoplastic Agent Sparfosic Acid. SYNTHETIC COMMUN 1997. [DOI: 10.1080/00397919708003363] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Affiliation(s)
- T D Tlsty
- Department of Pathology, University of California at San Francisco 94143-0506, USA
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Nakayama K, Ishida N, Shirane M, Inomata A, Inoue T, Shishido N, Horii I, Loh DY, Nakayama K. Mice lacking p27(Kip1) display increased body size, multiple organ hyperplasia, retinal dysplasia, and pituitary tumors. Cell 1996; 85:707-20. [PMID: 8646779 DOI: 10.1016/s0092-8674(00)81237-4] [Citation(s) in RCA: 1176] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
SUMMARY Mice lacking p27(Kip1) have been created by gene targeting in embryonic stem cells. These mice are larger than the control animals, with thymus, pituitary, and adrenal glands and gonadal organs exhibiting striking enlargement. CDK2 activity is elevated about 10-fold in p27(-/-) thymocytes. Development of ovarian follicles seems to be impaired, resulting in female sterility. Similar to mice with the Rb mutation, the p27(-/-) mice often develop pituitary tumors spontaneously. The retinas of the mutant mice show a disturbed organization of the normal cellular layer pattern. These findings indicate that p27(Kip1) acts to regulate the growth of a variety of cells. Unexpectedly, the cell cycle arrest mediated by TGFbeta, rapamycin, or contact inhibition remained intact in p27(-/-) cells, suggesting that p27(Kip1) is not required in these pathways.
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Affiliation(s)
- K Nakayama
- Department of Biology, Nippon Roche Research Center, Kamakura, Kanagawa, Japan
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Yang JL, Fernandes DJ, Wheeler KT, Capizzi RL. PALA enhancement of bromodeoxyuridine incorporation into DNA increases radiation cytotoxicity to human ovarian adenocarcinoma cells. Int J Radiat Oncol Biol Phys 1996; 34:1073-9. [PMID: 8600090 DOI: 10.1016/0360-3016(95)02165-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
PURPOSE N-(phosphonacetyl)-L-aspartic acid (PALA) is a transition- state inhibitor of L-aspartate transcarbamylase, which catalyses the biosynthesis of carbamyl-L-aspartate in the de novo pyrimidine biosynthetic pathway. 5-Bromodeoxyuridine (BrdUrd) is known to be a potent radiosensitizer of proliferating cells when it is incorporated into DNA. The experiments described herein were performed to test the hypothesis that depletion of cellular pyrimidine precursors by PALA may increase both the incorporation of BrdUrd into DNA and the sensitivity of these cells to the cytotoxic effect of radiation. METHODS AND MATERIALS The effect of PALA concentration and exposure time on the incorporation of BrdUrd into the DNA of exponentially growing BG-1 human ovarian carcinoma cells was determined. BG-1 cells exposed to the most effective PALA + BrdUrd treatment schedule were then irradiated to determine if PALA could enhance the radiosensitization already achieved by pretreatment with BrdUrd alone. RESULTS A 72-h exposure to PALA (> or = 25 microM) delayed the growth of human ovarian adenocarcinoma BG-1 cells by 40% compared to that of the untreated control cells. Using a clonogenic assay, the IC50 for a 72-h PALA exposure was approximately 25 microM and the cell killing efficiency was dependent on both the concentration and duration of the exposure. A 72-h exposure to 25 microM PALA produced approximately a 90% decrease in the intracellular uridine-5'-triphosphate (UTP) and cytidine-5'-triphosphate (CTP) levels, but had no effect on the intracellular adenosine-5'-triphosphate (ATP) level. This decrease in the UTP and CTP pools promoted a fivefold increase in the incorporation of [3H]BrdUrd into the DNA of BG-1 cells. The most effective treatment schedule involved a 72-h time course, consisting of a 48-h pretreatment with PALA alone, followed by an additional 24-h treatment with both PALA and BrdUrd. The two agent treatments, PALA (25 microM) + BrdUrd (16 microM), PALA (25 microM) + radiation (6 Gy), and BrdUrd (16 microM) + radiation (6 Gy) produced a 2.1-, 7.4-, and 13.2-fold increase in cytotoxicity, respectively, over that expected if the interaction between the two agents was independent and additive. The most effective three-agent treatment schedule consisting of PALA, BrdUrd, and radiation resulted in a greater than 30-fold increase in cytotoxicity over that expected if the interactions and the three agents were additive (p < 0.05). CONCLUSIONS These data indicate that PALA alone enhances radiation cytotoxicity and further enhances the radiosensitization already achieved with the halogenated pyrimidines. These effects could be clinically beneficial.
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Affiliation(s)
- J L Yang
- Hollings Cancer Center, Medical University of South Carolina, Charleston, USA
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Purcarea C, Simon V, Prieur D, Hervé G. Purification and characterization of carbamoyl-phosphate synthetase from the deep-sea hyperthermophilic archaebacterium Pyrococcus abyssi. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 236:189-99. [PMID: 8617264 DOI: 10.1111/j.1432-1033.1996.00189.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Carbamoyl-phosphate synthetase was purified from the deep-sea hyperthermophilic archaebacterium Pyrococcus abyssi. This enzyme appears to be monomeric and uses ammonium salts as nitrogen donor. Its activity is inhibited by some nucleotides that compete with ATP. In contrast with the carbamoyl-phosphate synthetases investigated so far, this enzyme is very resistant to high temperature. Its low molecular mass (46.6 kDa) and its catalytic properties suggest that the gene coding for this enzyme is a previously postulated ancestor, whose duplication gave the genes coding for carbamoyl-phosphate synthetases and carbamate kinases.
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Affiliation(s)
- C Purcarea
- Laboratoire de Biochimie des Signaux Régulateurs Cellulaires et Moléculaires, Université Pierre et Marie Curie, Paris, France
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Deng C, Zhang P, Harper JW, Elledge SJ, Leder P. Mice lacking p21CIP1/WAF1 undergo normal development, but are defective in G1 checkpoint control. Cell 1995; 82:675-84. [PMID: 7664346 DOI: 10.1016/0092-8674(95)90039-x] [Citation(s) in RCA: 1583] [Impact Index Per Article: 54.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
p21CIP1/WAF1 is a CDK inhibitor regulated by the tumor suppressor p53 and is hypothesized to mediate G1 arrest. p53 has been suggested to derive anti-oncogenic properties from this relationship. To test these notions, we created mice lacking p21CIP1/WAF1. They develop normally and (unlike p53-/- mice) have not developed spontaneous malignancies during 7 months of observation. Nonetheless, p21-/- embryonic fibroblasts are significantly deficient in their ability to arrest in G1 in response to DNA damage and nucleotide pool perturbation. p21-/- cells also exhibit a significant growth alteration in vitro, achieving a saturation density as high as that observed in p53-/- cells. In contrast, other aspects of p53 function, such as thymocytic apoptosis and the mitotic spindle checkpoint, appear normal. These results establish the role of p21CIP1/WAF1 in the G1 checkpoint, but suggest that the anti-apoptotic and the anti-oncogenic effects of p53 are more complex.
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Affiliation(s)
- C Deng
- Howard Hughes Medical Institute, Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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Wyde PR, Moore DK, Pimentel DM, Blough HA. Evaluation of the antiviral activity of N-(phosphonoacetyl)-L-aspartate against paramyxoviruses in tissue culture and against respiratory syncytial virus in cotton rats. Antiviral Res 1995; 27:59-69. [PMID: 7486959 DOI: 10.1016/0166-3542(94)00080-r] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
N-(phosphonoacetyl)-L-aspartate (PALA), a potent inhibitor of L-aspartic acid transcarbamoylase, was evaluated for cytotoxicity and antiviral activity against three different paramyxoviruses in tissue culture, and for antiviral efficacy and toxicity in vivo using a cotton rat-respiratory syncytial virus (RSV) model. Significant in vitro cytotoxicity was observed in proliferating cultures of HEp-2 (IC50 = 250 micrograms/ml) and Vero cells (IC50 = 32 micrograms/ml), but was less evident in cultures containing confluent monolayers (i.e., stationary cells) of these cells, or in cultures of Madin Darby canine kidney (MDCK) cells (these IC50 values were all > or = 750 micrograms/ml, with 1000 micrograms/ml being the maximum concentration tested). Mean selective indices (ratio of the median cytotoxic dose: median efficacious dose) of 1, 72 and 146 were obtained against parainfluenza virus type 3, RSV and measles virus, respectively, when PALA was tested against these viruses using confluent HEp-2 and Vero cell monolayers. In cotton rats, significant reductions in pulmonary titers (0.8-1.4 log10/g lung) compared to pulmonary viral titers in placebo-treated control animals, were consistently seen in cotton rats given > or = 10 mg of PALA/kg/day (b.i.d.) intraperitoneally on days 1-3 postinfection with either subtype A or B RSV. No toxic effects were noted even in animals given 100 mg of PALA/kg/day for 7 consecutive days.
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Affiliation(s)
- P R Wyde
- Department of Microbiology and Immunology, Baylor College of Medicine, Houston, TX 77030, USA
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Almasan A, Linke SP, Paulson TG, Huang LC, Wahl GM. Genetic instability as a consequence of inappropriate entry into and progression through S-phase. Cancer Metastasis Rev 1995; 14:59-73. [PMID: 7606822 DOI: 10.1007/bf00690212] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The stability of the mammalian genome depends on the proper function of G1 and G2 cell cycle control mechanisms. Two tumor suppressors, p53 and retinoblastoma (Rb), play key roles in progression from G1 into S-phase. We address the mechanisms by which these proteins mediate a G1 arrest in response to DNA damage and limiting metabolic conditions. Gamma-irradiation induced a prolonged, p53-dependent G1 arrest associated with a long-term increase in the levels of the cdk-inhibitor p21WAFl/Cipl (p21). Microinjection of linear plasmid DNA also caused a G1 arrest. The p53-dependent arrest induced by inhibitors of UMP biosynthesis was reversible and occurred in the absence of detectable DNA damage. Both arrest mechanisms contribute to limiting the formation and propagation of damaged genomes. Cells containing mutant p53 but wild-type Rb do not generate methotrexate (Mtx) resistant variants. However, pre-treatment with DNA damaging agents prior to drug selection resulted in resistant clones containing amplified dihydrofolate reductase (DHFR) genes, suggesting that DNA breakage is a rate limiting step for gene amplification. The Mtx-induced arrest did not occur in cells with non-functional Rb. Rb acts as a negative regulator of the E2F transcription factors, and Rb-deficient primary mouse embryo fibroblasts (MEFs) produced elevated levels of mRNA and protein for key E2F target genes. Failure to prevent entry into S-phase in Rb-/- MEFs exposed to DNA-damaging or nutrient limiting conditions caused apoptosis and correlated with p53 induction. Taken together, these findings indicate a link between p53 and Rb function and suggest that their coordination insures correct entry into S-phase, minimizing the emergence of genetic variants.
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Affiliation(s)
- A Almasan
- Gene Expression Lab, Salk Institute, La Jolla, California, USA
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Rustum YM, Cao S, Yin MB. Modulation of target enzyme associated with the action of antifolates. ADVANCES IN ENZYME REGULATION 1994; 34:57-70. [PMID: 7942285 DOI: 10.1016/0065-2571(94)90008-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The cytotoxicity and molecular effects of antifolate thymidylate synthase inhibitor, ICI-D1694, against human ileocecal carcinoma, were evaluated. The drug concentration for 50% inhibition of cell growth by ICI-D1694 is 73 nM and 3 nM following 2 hr and 72 hr exposure, respectively. The drug induces high level of DNA single strand breaks in a time dependent manner, but subsequent to maximum inhibition of thymidylate synthase. Drug effects can be reversed by thymidine and leucovorin at > 1 microM concentrations. Leucovorin action is primarily at the cell membrane level, competing with the transport and activation of ICI-D1694. Thymidine, however, exerts its competitive effect primarily at the level of thymidylate synthase.
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Affiliation(s)
- Y M Rustum
- Grace Cancer Drug Center and Experimental Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263
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Jodrell DI, Oster W, Kerr DJ, Canney PA, Yosef H, Steward WP, Kaye SB, Cassidy J. A phase I-II study of N-(phosphonacetyl)-L-aspartic acid (PALA) added to 5-fluorouracil and folinic acid in advanced colorectal cancer. Eur J Cancer 1994; 30A:950-5. [PMID: 7946590 DOI: 10.1016/0959-8049(94)90121-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
N-(phosphonacetyl)-L-aspartic acid (PALA) inhibits the enzyme L-aspartic acid transcarbamoylase (ATCase) which is important in de novo pyrimidine synthesis. Low dosages of PALA modulate the in vitro activity of 5-fluorouracil (5-FU) and PALA (250 mg/m2) inhibits pyrimidine synthesis in patients. PALA (250 mg/m2 day 1) was combined with an established 5-FU/folinic acid (FA) regimen [FA (200 mg/m2 over 2 h days 2 + 3) and bolus and 22 h infusional 5-FU (300-500 mg/m2 days 2 + 3)] without the need for dose reduction of 5-FU or FA. 35 patients were entered. Treatment was well tolerated; 4/27 patients experienced > or = ECOG grade 3 toxicity at full 5-FU dosage (500 mg/m2 bolus/infusion). However, the response rate in 33 evaluable patients was only 6.1% [95% confidence intervals (C.I.) 0.2-21.8%]. Median response duration was short (4 months, 95% C.I. 3-6 months) and overall median survival was 10 months (95% C.I. 7-16 months). Although PALA (250 mg/m2) can be combined with full dosage 5-FU/FA, the combination has poor activity in colorectal cancer.
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Affiliation(s)
- D I Jodrell
- Beatson Oncology Centre, Western Infirmary, Glasgow, U.K
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