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Matencio A, García-Carmona F, López-Nicolás JM. Characterization of Resveratrol, Oxyresveratrol, Piceatannol and Roflumilast as Modulators of Phosphodiesterase Activity. Study of Yeast Lifespan. Pharmaceuticals (Basel) 2020; 13:E225. [PMID: 32872677 PMCID: PMC7559934 DOI: 10.3390/ph13090225] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 08/14/2020] [Accepted: 08/28/2020] [Indexed: 11/19/2022] Open
Abstract
Our desire to live longer has led to an ever-increasing number of novel antiaging products. However, few molecules have any real effect and new ones need to be studied before they can be used commercially. In this contribution, activation of the caloric restriction (CR) pathway was studied using different three (resveratrol, oxyresveratrol and piceatannol)-a family with demonstrated bioactivity on phosphodiesterase activity. The high-affinity phosphodiesterase type 2 (PDE2) of Saccharomyces cerevisiae was expressed in Escherichia coli, purified and characterized. The activity and the inhibitory activity of each stilbene was studied, and the findings were compared in vitro and in silico with those obtained with roflumilast-a human PDE4 inhibitor widely used in chronic obstructive pulmonary diseases. Finally, an in vivo chronological lifespan assay using WT S. cerevisiae and ΔPDE2 S. cerevisiae strains was carried out. It was demonstrated that stilbenes can modulate yPDE2 activity, increasing the lifespan of the yeast by 18% over a control (in combination with other pathways). In addition, roflumilast increased the lifespan in the WT strain. The findings as a whole would increase the range of lifespan products available and suggest novel uses for approved drugs.
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Affiliation(s)
| | | | - José Manuel López-Nicolás
- Departamento de Bioquímica y Biología Molecular A, Unidad Docente de Biología, Facultad de Veterinaria, Regional Campus of International Excellence “Campus Mare Nostrum”, Universidad de Murcia, 30003 Murcia, Spain; (A.M.); (F.G.-C.)
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2
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Munday JC, Kunz S, Kalejaiye TD, Siderius M, Schroeder S, Paape D, Alghamdi AH, Abbasi Z, Huang SX, Donachie AM, William S, Sabra AN, Sterk GJ, Botros SS, Brown DG, Hoffman CS, Leurs R, de Koning HP. Cloning and functional complementation of ten Schistosoma mansoni phosphodiesterases expressed in the mammalian host stages. PLoS Negl Trop Dis 2020; 14:e0008447. [PMID: 32730343 PMCID: PMC7430754 DOI: 10.1371/journal.pntd.0008447] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 08/17/2020] [Accepted: 06/02/2020] [Indexed: 01/29/2023] Open
Abstract
Only a single drug against schistosomiasis is currently available and new drug development is urgently required but very few drug targets have been validated and characterised. However, regulatory systems including cyclic nucleotide metabolism are emerging as primary candidates for drug discovery. Here, we report the cloning of ten cyclic nucleotide phosphodiesterase (PDE) genes of S. mansoni, out of a total of 11 identified in its genome. We classify these PDEs by homology to human PDEs. Male worms displayed higher expression levels for all PDEs, in mature and juvenile worms, and schistosomula. Several functional complementation approaches were used to characterise these genes. We constructed a Trypanosoma brucei cell line in which expression of a cAMP-degrading PDE complements the deletion of TbrPDEB1/B2. Inhibitor screens of these cells expressing only either SmPDE4A, TbrPDEB1 or TbrPDEB2, identified highly potent inhibitors of the S. mansoni enzyme that elevated the cellular cAMP concentration. We further expressed most of the cloned SmPDEs in two pde1Δ/pde2Δ strains of Saccharomyces cerevisiae and some also in a specialised strain of Schizosacharomyces pombe. Five PDEs, SmPDE1, SmPDE4A, SmPDE8, SmPDE9A and SmPDE11 successfully complemented the S. cerevisiae strains, and SmPDE7var also complemented to a lesser degree, in liquid culture. SmPDE4A, SmPDE8 and SmPDE11 were further assessed in S. pombe for hydrolysis of cAMP and cGMP; SmPDE11 displayed considerable preferrence for cGMP over cAMP. These results and tools enable the pursuit of a rigorous drug discovery program based on inhibitors of S. mansoni PDEs.
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Affiliation(s)
- Jane C. Munday
- Institute of Infection, Immunity and inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom
| | - Stefan Kunz
- Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit Amsterdam, The Netherlands
| | - Titilola D. Kalejaiye
- Institute of Infection, Immunity and inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom
| | - Marco Siderius
- Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit Amsterdam, The Netherlands
| | | | - Daniel Paape
- Institute of Infection, Immunity and inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom
| | - Ali H. Alghamdi
- Institute of Infection, Immunity and inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom
| | - Zainab Abbasi
- Biology Department, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Sheng Xiang Huang
- Biology Department, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Anne-Marie Donachie
- Institute of Infection, Immunity and inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom
| | - Samia William
- Department of Pharmacology, Theodor Bilharz Research Institute, Warrak El-Hadar, Imbaba, Egypt
| | - Abdel Nasser Sabra
- Department of Pharmacology, Theodor Bilharz Research Institute, Warrak El-Hadar, Imbaba, Egypt
| | - Geert Jan Sterk
- Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit Amsterdam, The Netherlands
| | - Sanaa S. Botros
- Department of Pharmacology, Theodor Bilharz Research Institute, Warrak El-Hadar, Imbaba, Egypt
| | - David G. Brown
- School of Biosciences, University of Kent, United Kingdom
| | - Charles S. Hoffman
- Biology Department, Boston College, Chestnut Hill, Massachusetts, United States of America
| | - Rob Leurs
- Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit Amsterdam, The Netherlands
| | - Harry P. de Koning
- Institute of Infection, Immunity and inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, United Kingdom
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3
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Getz RA, Kwak G, Cornell S, Mbugua S, Eberhard J, Huang SX, Abbasi Z, de Medeiros AS, Thomas R, Bukowski B, Dranchak PK, Inglese J, Hoffman CS. A fission yeast platform for heterologous expression of mammalian adenylyl cyclases and high throughput screening. Cell Signal 2019; 60:114-121. [PMID: 31026495 DOI: 10.1016/j.cellsig.2019.04.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 04/12/2019] [Accepted: 04/22/2019] [Indexed: 01/18/2023]
Abstract
The fission yeast Schizosaccharomyces pombe uses a cAMP signaling pathway to link glucose-sensing to Protein Kinase A activity in order to regulate cell growth, sexual development, gluconeogenesis, and exit from stationary phase. We previously used a PKA-repressed fbp1-ura4 reporter to conduct high throughput screens (HTSs) for inhibitors of heterologously-expressed mammalian cyclic nucleotide phosphodiesterases (PDEs). Here, we describe the successful expression of all ten mammalian adenylyl cyclase (AC) genes, along with the human GNAS Gαs gene. By measuring expression of an fbp1-GFP reporter together with direct measurements of intracellular cAMP levels, we can detect both basal AC activity from all ten AC genes as well as GNAS-stimulated activity from eight of the nine transmembrane ACs (tmACs; AC2-AC9). The ability to use this platform to conduct HTS for novel chemical probes that reduce PKA activity was demonstrated by a pilot screen of the LOPAC®1280 library, leading to the identification of diphenyleneiodonium chloride (DPI) as an inhibitor of basal AC activity. This screening technology could open the door to the development of therapeutic compounds that target GNAS or the ACs, an area in which there is significant unmet need.
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Affiliation(s)
- Rachel A Getz
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA
| | - Grace Kwak
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA
| | - Stacie Cornell
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA
| | - Samuel Mbugua
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA.
| | - Jeremy Eberhard
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA.
| | - Sheng Xiang Huang
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA.
| | - Zainab Abbasi
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA.
| | | | - Rony Thomas
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA.
| | - Brett Bukowski
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA.
| | - Patricia K Dranchak
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD 20850, USA.
| | - James Inglese
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD 20850, USA.
| | - Charles S Hoffman
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA.
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4
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de Medeiros AS, Wyman AR, Alaamery MA, Allain C, Ivey FD, Wang L, Le H, Morken JP, Habara A, Le C, Cui S, Lerner A, Hoffman CS. Identification and characterization of a potent and biologically-active PDE4/7 inhibitor via fission yeast-based assays. Cell Signal 2017; 40:73-80. [PMID: 28867658 PMCID: PMC5651194 DOI: 10.1016/j.cellsig.2017.08.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 08/25/2017] [Accepted: 08/28/2017] [Indexed: 01/21/2023]
Abstract
We previously constructed a collection of fission yeast strains that express various mammalian cyclic nucleotide phosphodiesterases (PDEs) and developed a cell-based high throughput screen (HTS) for small molecule PDE inhibitors. Here we describe a compound, BC54, that is a selective inhibitor of enzymes from the cAMP-specific PDE4 and PDE7 families. Consistent with the biological effect of other PDE4 and PDE7 inhibitors, BC54 displays potent anti-inflammatory properties and is superior to a combination of rolipram (a PDE4 inhibitor) and BRL50481 (a PDE7A inhibitor) for inducing apoptosis in chronic lymphocytic leukemia (CLL) cells. We further exploited PKA-regulated growth phenotypes in fission yeast to isolate two mutant alleles of the human PDE4B2 gene that encode enzymes possessing single amino acid changes that confer partial resistance to BC54. We confirm this resistance to both BC54 and rolipram via yeast-based assays and, for PDE4B2T407A, in vitro enzyme assays. Thus, we are able to use this system for both chemical screens to identify biologically-active PDE inhibitors and molecular genetic studies to characterize the interaction of these molecules with their target enzymes. Based on its potency, selectivity, and effectiveness in cell culture, BC54 should be a useful tool to study biological processes regulated by PDE4 and PDE7 enzymes.
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MESH Headings
- Anti-Inflammatory Agents, Non-Steroidal/pharmacology
- Apoptosis/drug effects
- Cyclic AMP/metabolism
- Cyclic Nucleotide Phosphodiesterases, Type 4/metabolism
- Cyclic Nucleotide Phosphodiesterases, Type 7/antagonists & inhibitors
- Cyclohexanes/pharmacology
- Drug Evaluation, Preclinical
- Humans
- Leukemia, Lymphocytic, Chronic, B-Cell/genetics
- Leukemia, Lymphocytic, Chronic, B-Cell/pathology
- Pyridines/pharmacology
- Pyrimidines/pharmacology
- Rolipram/administration & dosage
- Schizosaccharomyces/drug effects
- Schizosaccharomyces/genetics
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Affiliation(s)
| | - Arlene R Wyman
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA.
| | - Manal A Alaamery
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA
| | - Christina Allain
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA
| | - F Douglas Ivey
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA
| | - Lili Wang
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA
| | - Hai Le
- Chemistry Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA
| | - James P Morken
- Chemistry Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA.
| | - Alawi Habara
- Section of Hematology/Oncology, Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA.
| | - Cuong Le
- Section of Hematology/Oncology, Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA.
| | - Shuaiying Cui
- Section of Hematology/Oncology, Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA.
| | - Adam Lerner
- Section of Hematology/Oncology, Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA.
| | - Charles S Hoffman
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA.
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5
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The single cyclic nucleotide-specific phosphodiesterase of the intestinal parasite Giardia lamblia represents a potential drug target. PLoS Negl Trop Dis 2017; 11:e0005891. [PMID: 28915270 PMCID: PMC5617230 DOI: 10.1371/journal.pntd.0005891] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 09/27/2017] [Accepted: 08/21/2017] [Indexed: 01/08/2023] Open
Abstract
Background Giardiasis is an intestinal infection correlated with poverty and poor drinking water quality, and treatment options are limited. According to the Center for Disease Control and Prevention, Giardia infections afflict nearly 33% of people in developing countries, and 2% of the adult population in the developed world. This study describes the single cyclic nucleotide-specific phosphodiesterase (PDE) of G. lamblia and assesses PDE inhibitors as a new generation of anti-giardial drugs. Methods An extensive search of the Giardia genome database identified a single gene coding for a class I PDE, GlPDE. The predicted protein sequence was analyzed in-silico to characterize its domain structure and catalytic domain. Enzymatic activity of GlPDE was established by complementation of a PDE-deficient Saccharomyces cerevisiae strain, and enzyme kinetics were characterized in soluble yeast lysates. The potency of known PDE inhibitors was tested against the activity of recombinant GlPDE expressed in yeast and against proliferating Giardia trophozoites. Finally, the localization of epitope-tagged and ectopically expressed GlPDE in Giardia cells was investigated. Results Giardia encodes a class I PDE. Catalytically important residues are fully conserved between GlPDE and human PDEs, but sequence differences between their catalytic domains suggest that designing Giardia-specific inhibitors is feasible. Recombinant GlPDE hydrolyzes cAMP with a Km of 408 μM, and cGMP is not accepted as a substrate. A number of drugs exhibit a high degree of correlation between their potency against the recombinant enzyme and their inhibition of trophozoite proliferation in culture. Epitope-tagged GlPDE localizes as dots in a pattern reminiscent of mitosomes and to the perinuclear region in Giardia. Conclusions Our data strongly suggest that inhibition of G. lamblia PDE activity leads to a profound inhibition of parasite proliferation and that GlPDE is a promising target for developing novel anti-giardial drugs. Cellular signaling by the cyclic nucleotides cAMP and cGMP is ubiquitously found in organisms from human to unicellular parasites. Cyclic nucleotide-specific phosphodiesterases (PDEs) are pivotal regulators of these signaling processes and these enzymes represent important drug targets for a variety of diseases. Eleven PDE families are distinguished in humans and selective inhibition of a single human PDE family without targeting others is feasible. In parasites, interference in the signaling mechanism by PDE inhibition may be fatal. The diarrhea-causing parasite Giardia lamblia contains only one single PDE, named GlPDE. GlPDE activity is highly impaired by a range of PDE inhibitors, which also suppress parasite proliferation in vitro. Thus, there is a good agreement between PDE inhibition and parasite drug susceptibility. We demonstrate molecular differences between human PDEs and GlPDE that can be exploited for the development of GlPDE-selective inhibitors. Finally, our data may suggest localization of GlPDE to mitosome organelles, which are absent in human cells and thus are in the focus as possible targets for the treatment of giardiasis. This may add to the notion that GlPDE represents a potential target for the development of novel anti-giardial drugs.
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6
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Luginbuehl E, Kunz S, Wentzinger L, Freimoser F, Seebeck T. The exopolyphosphatase TbrPPX1 of Trypanosoma brucei. BMC Microbiol 2011; 11:4. [PMID: 21208463 PMCID: PMC3022644 DOI: 10.1186/1471-2180-11-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Accepted: 01/06/2011] [Indexed: 01/14/2023] Open
Abstract
Background Exopolyphosphatases and pyrophosphatases play important but still incompletely understood roles in energy metabolism, and also in other aspects of cell biology such as osmoregulation or signal transduction. Earlier work has suggested that a human exopolyphosphatase, Prune, might exhibit cyclic nucleotide phosphodiesterase activity. Results The kinetoplastida, a large order of unicellular eukaryotes that contains many important pathogens such as Trypanosoma brucei (human sleeping sickness), Trypanosoma cruzi (Chagas disease) or Leishmania ssp (several clinically dinstinct leishmaniases) all contain several exo- and pyrophosphatases. The current study provides a systematic classification of these enzymes, which now allows to situate the information that is already available on some of these enzymes. It then analyses the exopolyphosphatase TbrPPX1 of T. brucei in detail, using RNA interference and genetic knockouts in an attempt to define its function, and immunofluorescence microscopy to study its subcellular localization. TbrPPX1 is an exopolyphosphatase that does hydrolyze pentasodium triphosphate, but not organic triphosphates such as ATP, pyrophosphate or long-chain polyphosphates. Finally, the study investigates the potential cyclic nucleotide phosphodiesterase activity of TbrPPX1. Conclusions All kinetoplastid genomes that are currently available contain genes for an exopolyphosphatase and two classes of pyrophosphatases, one associated with the acidocalcisomes and one cytoplasmic. TbrPPX1 represents the T. brucei exopolyphosphatase. It is located throughout the cytoplasm, and its genetic ablation does not produce a dramatic phenotype. Importantly, TbrPPX1 does not exhibit any cyclic nucleotide specific phosphodiesterase activity, which definitively eliminates it as an additional player in cAMP signalling of the kinetoplastida.
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Affiliation(s)
- Edith Luginbuehl
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
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7
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Demirbas D, Ceyhan O, Wyman AR, Hoffman CS. A fission yeast-based platform for phosphodiesterase inhibitor HTSs and analyses of phosphodiesterase activity. Handb Exp Pharmacol 2011:135-49. [PMID: 21695638 DOI: 10.1007/978-3-642-17969-3_5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Fission yeast strains have been engineered so that their growth behavior reflects the activity of heterologous cyclic nucleotide phosphodiesterases (PDEs). These strains can be used in High-Throughput Screens (HTSs) for PDE inhibitors that possess "drug-like" characteristics, displaying activity in a growth stimulation assay over a 48-h period. Through three generations of development, a collection of strains expressing 10 of the 11 mammalian PDE families that is appropriate for small molecule inhibitor screening has been generated in our laboratory. Strains unable to synthesize cyclic nucleotides allow characterization of PDE activity in that the enzyme's potency is reflected in the amount of either cAMP or cGMP that must be added to the growth medium to stimulate cell growth. In the future, this system could be used to screen cDNA libraries for biological regulators of target PDEs and for the construction of strains that co-express PDEs and associated regulatory proteins to facilitate molecular and genetic studies of their functions and, in particular, to identify whether different PDE-partner protein complexes show distinct patterns of inhibitor sensitivity.
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Affiliation(s)
- Didem Demirbas
- Biology Department, Boston College, Higgins Hall 401B, Chestnut Hill, Boston, MA 02467, USA
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8
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Demirbas D, Ceyhan O, Wyman AR, Ivey FD, Allain C, Wang L, Sharuk MN, Francis SH, Hoffman CS. Use of a Schizosaccharomyces pombe PKA-repressible reporter to study cGMP metabolising phosphodiesterases. Cell Signal 2010; 23:594-601. [PMID: 21118717 DOI: 10.1016/j.cellsig.2010.11.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 11/13/2010] [Accepted: 11/22/2010] [Indexed: 10/18/2022]
Abstract
The Schizosaccharomyces pombe fbp1 gene is transcriptionally repressed by protein kinase A (PKA) that is activated by extracellular glucose via a cAMP-signaling pathway. We previously used an fbp1-ura4 reporter that places uracil biosynthesis under the control of the glucose-sensing pathway to identify mutations in genes of the cAMP pathway. More recently, this reporter has been used in high throughput screens for small molecule inhibitors of heterologously-expressed cyclic nucleotide phosphodiesterases (PDEs) that hydrolyse cAMP to 5' AMP. Here we show that strains lacking the adenylyl cyclase gene respond to either exogenous cAMP or cGMP to activate PKA, thus regulating fbp1-ura4 expression and other PKA-regulated processes such as conjugation and the nuclear export of an Rst2-GFP fusion protein. Expression of cGMP-specific PDEs or ones that hydrolyse both cAMP and cGMP increases the amount of exogenous cGMP required to activate PKA in order to repress fbp1-ura4 expression, creating conditions that allow detection of inhibitors of these PDEs. As proof of this concept, we screened a collection of compounds previously identified as inhibitors of cAMP-specific PDE4 or PDE7 enzymes for their ability to inhibit the mammalian cGMP-specific PDE5A enzyme. We identified compound BC76, which inhibits PDE5A in an in vitro enzyme assay with an IC(50) of 232nM. Further yeast-based assays show that BC76 inhibits PDE1, PDE4, PDE5, PDE8, PDE10 and PDE11, thus demonstrating the utility of this system for detecting and characterising inhibitors of either cAMP- or cGMP-metabolising PDEs.
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Affiliation(s)
- Didem Demirbas
- Biology Department, Boston College, 140 Commonwealth Ave., Chestnut Hill, MA 02467, USA.
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9
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Mazin PV, Gelfand MS, Mironov AA, Rakhmaninova AB, Rubinov AR, Russell RB, Kalinina OV. An automated stochastic approach to the identification of the protein specificity determinants and functional subfamilies. Algorithms Mol Biol 2010; 5:29. [PMID: 20633297 PMCID: PMC2914642 DOI: 10.1186/1748-7188-5-29] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Accepted: 07/15/2010] [Indexed: 11/30/2022] Open
Abstract
Background Recent progress in sequencing and 3 D structure determination techniques stimulated development of approaches aimed at more precise annotation of proteins, that is, prediction of exact specificity to a ligand or, more broadly, to a binding partner of any kind. Results We present a method, SDPclust, for identification of protein functional subfamilies coupled with prediction of specificity-determining positions (SDPs). SDPclust predicts specificity in a phylogeny-independent stochastic manner, which allows for the correct identification of the specificity for proteins that are separated on a phylogenetic tree, but still bind the same ligand. SDPclust is implemented as a Web-server http://bioinf.fbb.msu.ru/SDPfoxWeb/ and a stand-alone Java application available from the website. Conclusions SDPclust performs a simultaneous identification of specificity determinants and specificity groups in a statistically robust and phylogeny-independent manner.
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10
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Sadeghian H, Seyedi SM, Saberi MR, Nick RS, Hosseini A, Bakavoli M, Mansouri SMT, Parsaee H. Design, synthesis and pharmacological evaluation of 6-hydroxy-4-methylquinolin-2(1H)-one derivatives as inotropic agents. J Enzyme Inhib Med Chem 2010; 24:918-29. [PMID: 19555170 DOI: 10.1080/14756360802448063] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Selective PDE3 inhibitors improve cardiac contractility and may be used in congestive heart failure. However, their proarrhythmic potential is the most important side effect. In this research we designed, synthesized and evaluated the potential cardiotonic activity of thirteen PDE3 inhibitors (4-[(4-methyl-2-oxo-1,2-dihydro-6-quinolinyl)oxy]butanamide analogs) using the spontaneously beating atria model. The design strategy was based on the structure of cilostamide, a selective PDE3 inhibitor. In each experiment, atrium of reserpine-treated rat was isolated and the contractile and chronotropic effects of a synthetic compounds were assessed. All experiments were carried out in comparison with IBMX, amrinone and cilostamide as standard compounds. The results showed that, among the new compounds, the best pharmacological profile was obtained with the compound 6-[4-(4-methylpiperazine-1-yl)-4-oxobutoxy]-4-methylquinolin-2(1H)-one, 4j, which displayed selectivity for increasing the force of contraction (165 +/- 4% change over the control) rather than the frequency rate (115 +/- 7% change over the control) at 100 microM and potent inhibitory activity of PDE3 with IC(50) = 0.20 microM.
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Affiliation(s)
- Hamid Sadeghian
- Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, IR Iran
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Arya R, Aslam S, Gupta S, Bora RS, Vijayakrishnan L, Gulati P, Naithani S, Mukherjee S, Dastidar S, Bhattacharya A, Saini KS. Production and characterization of pharmacologically active recombinant human phosphodiesterase 4B in Dictyostelium discoideum. Biotechnol J 2008; 3:938-47. [PMID: 18348140 DOI: 10.1002/biot.200700256] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Phosphodiesterase 4B (PDE4B) is an important therapeutic target for asthma and chronic obstructive pulmonary disease. To identify PDE4 subtype-specific compounds using high-throughput assays, full-length recombinant PDE4 proteins are needed in bulk quantity. In the present study, full-length human PDE4B2 was expressed in the cellular slime mould Dictyostelium discoideum (Dd). A cell density of 2 x 10(7) cells/mL was obtained and up to 1 mg/L recombinant PDE4B2 was purified through Ni-NTA affinity chromatography. The expressed protein was soluble and its activity was comparable to PDE4B2 protein expressed in mammalian cells (K(m)=1.7 microM). The functional significance of the Dd expression system is supported by the demonstration that, in concert with proteins expressed in mammalian systems, there are no major changes in the affinity for PDE4B2 inhibitors and substrates. These findings thus provide the first evidence that Dd can be utilized for the expression and purification of functionally active full-length human PDE4B2 in large amounts required for high-throughput screening of pharmacologically active compounds against this therapeutic target.
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Affiliation(s)
- Ranjana Arya
- Department of Biotechnology and Bioinformatics, Ranbaxy Research laboratories, Gurgaon, Haryana, India.
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12
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Ivey FD, Wang L, Demirbas D, Allain C, Hoffman CS. Development of a fission yeast-based high-throughput screen to identify chemical regulators of cAMP phosphodiesterases. ACTA ACUST UNITED AC 2008; 13:62-71. [PMID: 18227226 DOI: 10.1177/1087057107312127] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cyclic nucleotide phosphodiesterases (PDEs) comprise a superfamily of enzymes that serve as drug targets in many human diseases. There is a continuing need to identify high-specificity inhibitors that affect individual PDE families or even subtypes within a single family. The authors describe a fission yeast-based high-throughput screen to detect inhibitors of heterologously expressed adenosine 3',5'-cyclic monophosphate (cAMP) PDEs. The utility of this system is demonstrated by the construction and characterization of strains that express mammalian PDE2A, PDE4A, PDE4B, and PDE8A and respond appropriately to known PDE2A and PDE4 inhibitors. High-throughput screens of 2 bioactive compound libraries for PDE inhibitors using strains expressing PDE2A, PDE4A, PDE4B, and the yeast PDE Cgs2 identified known PDE inhibitors and members of compound classes associated with PDE inhibition. The authors verified that the furanocoumarin imperatorin is a PDE4 inhibitor based on its ability to produce a PDE4-specific elevation of cAMP levels. This platform can be used to identify PDE activators, as well as genes encoding PDE regulators, which could serve as targets for future drug screens.
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Affiliation(s)
- F Douglas Ivey
- Biology Department, Boston College, Chestnut Hill, Massachusetts 02467, USA
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13
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Porat Z, Landau G, Bercovich Z, Krutauz D, Glickman M, Kahana C. Yeast antizyme mediates degradation of yeast ornithine decarboxylase by yeast but not by mammalian proteasome: new insights on yeast antizyme. J Biol Chem 2007; 283:4528-34. [PMID: 18089576 DOI: 10.1074/jbc.m708088200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mammalian antizyme (mAz) is a central element of a feedback circuit regulating cellular polyamines by accelerating ornithine decarboxylase (ODC) degradation and inhibiting polyamine uptake. Although yeast antizyme (yAz) stimulates the degradation of yeast ODC (yODC), we show here that it has only a minor effect on polyamine uptake by yeast cells. A segment of yODC that parallels the Az binding segment of mammalian ODC (mODC) is required for its binding to yAz. Although demonstrating minimal homology to mAz, our results suggest that yAz stimulates yODC degradation via a similar mechanism of action. We demonstrate that interaction with yAz provokes degradation of yODC by yeast but not by mammalian proteasomes. This differential recognition may serve as a tool for investigating proteasome functions.
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Affiliation(s)
- Ziv Porat
- Department of Molecular Genetics, The Weizmann Institute of Science, 1 Hertzel St., Rehovot 76100, Israel
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14
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Johner A, Kunz S, Linder M, Shakur Y, Seebeck T. Cyclic nucleotide specific phosphodiesterases of Leishmania major. BMC Microbiol 2006; 6:25. [PMID: 16522215 PMCID: PMC1431542 DOI: 10.1186/1471-2180-6-25] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Accepted: 03/08/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Leishmania represent a complex of important human pathogens that belong to the systematic order of the kinetoplastida. They are transmitted between their human and mammalian hosts by different bloodsucking sandfly vectors. In their hosts, the Leishmania undergo several differentiation steps, and their coordination and optimization crucially depend on numerous interactions between the parasites and the physiological environment presented by the fly and human hosts. Little is still known about the signalling networks involved in these functions. In an attempt to better understand the role of cyclic nucleotide signalling in Leishmania differentiation and host-parasite interaction, we here present an initial study on the cyclic nucleotide-specific phosphodiesterases of Leishmania major. RESULTS This paper presents the identification of three class I cyclic-nucleotide-specific phosphodiesterases (PDEs) from L. major, PDEs whose catalytic domains exhibit considerable sequence conservation with, among other, all eleven human PDE families. In contrast to other protozoa such as Dictyostelium, or fungi such as Saccharomyces cerevisiae, Candida ssp or Neurospora, no genes for class II PDEs were found in the Leishmania genomes. LmjPDEA contains a class I catalytic domain at the C-terminus of the polypeptide, with no other discernible functional domains elsewhere. LmjPDEB1 and LmjPDEB2 are coded for by closely related, tandemly linked genes on chromosome 15. Both PDEs contain two GAF domains in their N-terminal region, and their almost identical catalytic domains are located at the C-terminus of the polypeptide. LmjPDEA, LmjPDEB1 and LmjPDEB2 were further characterized by functional complementation in a PDE-deficient S. cerevisiae strain. All three enzymes conferred complementation, demonstrating that all three can hydrolyze cAMP. Recombinant LmjPDEB1 and LmjPDEB2 were shown to be cAMP-specific, with Km values in the low micromolar range. Several PDE inhibitors were found to be active against these PDEs in vitro, and to inhibit cell proliferation. CONCLUSION The genome of L. major contains only PDE genes that are predicted to code for class I PDEs, and none for class II PDEs. This is more similar to what is found in higher eukaryotes than it is to the situation in Dictyostelium or the fungi that concomitantly express class I and class II PDEs. Functional complementation demonstrated that LmjPDEA, LmjPDEB1 and LmjPDEB2 are capable of hydrolyzing cAMP. In vitro studies with recombinant LmjPDEB1 and LmjPDEB2 confirmed this, and they demonstrated that both are completely cAMP-specific. Both enzymes are inhibited by several commercially available PDE inhibitors. The observation that these inhibitors also interfere with cell growth in culture indicates that inhibition of the PDEs is fatal for the cell, suggesting an important role of cAMP signalling for the maintenance of cellular integrity and proliferation.
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Affiliation(s)
- Andrea Johner
- Institute for Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
- current address: Immunology and Infection Unit, Dept. of Biology, University of York; York YO10 5YW, UK
| | - Stefan Kunz
- Institute for Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
| | - Markus Linder
- Institute for Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
- current address: Swissmedic, Erlachstrasse 8, CH-3012 Bern, Switzerland
| | - Yasmin Shakur
- Otsuka Maryland Medicinal Laboratories, 9900 Medical Center Drive, Rockville, MD 20850, USA
| | - Thomas Seebeck
- Institute for Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
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15
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Porat Z, Erez O, Kahana C. Cellular localization and phosphorylation of Hrb1p is independent of Sky1p. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:207-13. [PMID: 16530282 DOI: 10.1016/j.bbamcr.2006.01.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Revised: 01/02/2006] [Accepted: 01/03/2006] [Indexed: 11/30/2022]
Abstract
Protein phosphorylation plays a major role in regulating cellular functions. We have previously demonstrated that Sky1p, the SR protein kinase of the budding yeast Saccharomyces cerevisiae, is a regulator of polyamine transport and ion homeostasis. Since its kinase activity was demonstrated essential for fulfilling these roles, we assumed that Sky1p function via substrates phosphorylation. Using an in vitro phosphorylation assay, we have identified Hrb1p as a putative Sky1p substrate. However, phosphorylation analysis in WT and sky1Delta cells and localization studies disproved Hrb1p as a true Sky1p substrate, although a segment of the RS domain is required for determining its subcellular localization. Furthermore, we demonstrate that Hrb1p and additional putative Sky1p substrates, identified by computational approach, are not involved in mediating the spermine tolerant phenotype of sky1Delta cells.
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Affiliation(s)
- Ziv Porat
- Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, ISRAEL
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16
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Montalibet J, Skorey K, McKay D, Scapin G, Asante-Appiah E, Kennedy BP. Residues distant from the active site influence protein-tyrosine phosphatase 1B inhibitor binding. J Biol Chem 2005; 281:5258-66. [PMID: 16332678 DOI: 10.1074/jbc.m511546200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Regions of protein-tyrosine phosphatase (PTP) 1B that are distant from the active site yet affect inhibitor binding were identified by a novel library screen. This screen was based on the observation that expression of v-Src in yeast leads to lethality, which can be rescued by the coexpression of PTP1B. However, this rescue is lost when yeast are grown in the presence of PTP1B inhibitors. To identify regions of PTP1B (amino acids 1-400, catalytic domain plus 80-amino acid C-terminal tail) that can affect the binding of the difluoromethyl phosphonate (DFMP) inhibitor 7-bromo-6-difluoromethylphosphonate 3-naphthalenenitrile, a library coexpressing PTP1B mutants and v-Src was generated, and the ability of yeast to grow in the presence of the inhibitor was evaluated. PTP1B inhibitor-resistant mutations were found to concentrate on helix alpha7 and its surrounding region, but not in the active site. No resistant amino acid substitutions were found to occur in the C-terminal tail, suggesting that this region has little effect on active-site inhibitor binding. An in-depth characterization of a resistant substitution localizing to region alpha7 (S295F) revealed that this change minimally affected enzyme catalytic activity, but significantly reduced the potency of a panel of structurally diverse DFMP PTP1B inhibitors. This loss of inhibitor potency was found to be due to the difluoro moiety of these inhibitors because only the difluoro inhibitors were shifted. For example, the inhibitor potency of a monofluorinated or non-fluorinated analog of one of these DFMP inhibitors was only minimally affected. Using this type of library screen, which can scan the nearly full-length PTP1B sequence (catalytic domain and C-terminal tail) for effects on inhibitor binding, we have been able to identify novel regions of PTP1B that specifically affect the binding of DFMP inhibitors.
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Affiliation(s)
- Jacqueline Montalibet
- Department of Biochemistry and Molecular Biology, Merck Frosst Center for Therapeutic Research, Pointe-Claire, Quebec H9R 4P8, Canada
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17
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Xu RX, Rocque WJ, Lambert MH, Vanderwall DE, Luther MA, Nolte RT. Crystal structures of the catalytic domain of phosphodiesterase 4B complexed with AMP, 8-Br-AMP, and rolipram. J Mol Biol 2004; 337:355-65. [PMID: 15003452 DOI: 10.1016/j.jmb.2004.01.040] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2003] [Revised: 12/23/2003] [Accepted: 01/09/2004] [Indexed: 10/26/2022]
Abstract
Phosphodiesterase catalyzes the hydrolysis of the intracellular second messenger 3',5'-cyclic AMP (cAMP) into the corresponding 5'-nucleotide. Phosphodiesterase 4 (PDE4), the major cAMP-specific PDE in inflammatory and immune cells, is an attractive target for the treatment of asthma and COPD. We have determined crystal structures of the catalytic domain of PDE4B complexed with AMP (2.0 A), 8-Br-AMP (2.13 A) and the potent inhibitor rolipram (2.0 A). All the ligands bind in the same hydrophobic pocket and can interact directly with the active site metal ions. The identity of these metal ions was examined using X-ray anomalous difference data. The structure of the AMP complex confirms the location of the catalytic site and allowed us to speculate about the detailed mechanism of catalysis. The high-resolution structures provided the experimental insight into the nucleotide selectivity of phosphodiesterase. 8-Br-AMP binds in the syn conformation to the enzyme and demonstrates an alternative nucleotide-binding mode. Rolipram occupies much of the AMP-binding site and forms two hydrogen bonds with Gln443 similar to the nucleotides.
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Affiliation(s)
- Robert X Xu
- Department of Computational, Analytical and Structural Sciences, GlaxoSmithKline, 5 Moore Drive, V-180, Research Triangle Park, NC 27709, USA.
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18
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Kunz S, Kloeckner T, Essen LO, Seebeck T, Boshart M. TbPDE1, a novel class I phosphodiesterase of Trypanosoma brucei. ACTA ACUST UNITED AC 2004; 271:637-47. [PMID: 14728691 DOI: 10.1111/j.1432-1033.2003.03967.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cyclic nucleotide specific phosphodiesterases (PDEs) are important components of all cAMP signalling networks. In humans, 11 different PDE families have been identified to date, all of which belong to the class I PDEs. Pharmacologically, they have become of great interest as targets for the development of drugs for a large variety of clinical conditions. PDEs in parasitic protozoa have not yet been extensively investigated, despite their potential as antiparasitic drug targets. The current study presents the identification and characterization of a novel class I PDE from the parasitic protozoon Trypanosoma brucei, the causative agent of human sleeping sickness. This enzyme, TbPDE1, is encoded by a single-copy gene located on chromosome 10, and it functionally complements PDE-deficient strains of Saccharomyces cerevisiae. Its C-terminal catalytic domain shares about 30% amino acid identity, including all functionally important residues, with the catalytic domains of human PDEs. A fragment of TbPDE1 containing the catalytic domain could be expressed in active form in Escherichia coli. The recombinant enzyme is specific for cAMP, but exhibits a remarkably high Km of > 600 microm for this substrate.
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Affiliation(s)
- Stefan Kunz
- Institute of Cell Biology, University of Bern, Switzerland
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19
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Chung C, Varnerin JP, Morin NR, MacNeil DJ, Singh SB, Patel S, Scapin G, Van der Ploeg LHT, Tota MR. The role of tryptophan 1072 in human PDE3B inhibitor binding. Biochem Biophys Res Commun 2003; 307:1045-50. [PMID: 12878217 DOI: 10.1016/s0006-291x(03)01299-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The catalytic domain of recombinant human PDE3B was expressed in Escherichia coli as inclusion bodies and refolded to form active enzyme. A mutation at tryptophan 1072 in PDE3B disrupts inhibitor binding, but has minimal effect on cAMP hydrolysis. The W1072A mutation caused a 158-fold decrease in affinity for cilostamide, a 740-fold decrease for cGMP, and a 15-fold decrease in affinity for IBMX. The corresponding tyrosine mutation had a smaller effect. However, the K(m) of cAMP for the W1072A mutation was only increased by about 7-fold. The data indicate that the inhibitor binding region is not completely coincident with the substrate binding region. The homologous residue in PDE4B is located on helix 16 within 7A of the predicted bound substrate. A model of PDE3B was constructed based on the X-ray crystal structure of PDE4B.
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Affiliation(s)
- Christine Chung
- Department of Metabolic Disorders, Merck Research Laboratories, P.O. Box 2000, Mailstop: RY80M-213, Rahway, NJ 07065, USA
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20
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Rascón A, Soderling SH, Schaefer JB, Beavo JA. Cloning and characterization of a cAMP-specific phosphodiesterase (TbPDE2B) from Trypanosoma brucei. Proc Natl Acad Sci U S A 2002; 99:4714-9. [PMID: 11930017 PMCID: PMC123713 DOI: 10.1073/pnas.002031599] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Here we report the cloning, expression, and characterization of a cAMP-specific phosphodiesterase (PDE) from Trypanosoma brucei (TbPDE2B). Using a bioinformatic approach, two different expressed sequence tag clones were identified and used to isolate the complete sequence of two identical PDE genes arranged in tandem. Each gene consists of 2,793 bases that predict a protein of 930 aa with a molecular mass of 103.2 kDa. Two GAF (for cGMP binding and stimulated PDEs, Anabaena adenylyl cyclases, and Escherichia coli FhlA) domains, similar to those contained in many signaling molecules including mammalian PDE2, PDE5, PDE6, PDE10, and PDE11, were located N-terminal to a consensus PDE catalytic domain. The catalytic domain is homologous to the catalytic domain of all 11 mammalian PDEs, the Dictyostelium discoideum RegA, and a probable PDE from Caenorhabditis elegans. It is most similar to the T. brucei PDE2A (89% identity). TbPDE2B has substrate specificity for cAMP with a K(m) of 2.4 microM. cGMP is not hydrolyzed by TbPDE2B nor does this cyclic nucleotide modulate cAMP PDE activity. The nonselective PDE inhibitors 3-isobutyl-1-methylxanthine, papaverine and pentoxifyline are poor inhibitors of TbPDE2B. Similarly, PDE inhibitors selective for the mammalian PDE families 2, 3, 5, and 6 (erythro-9-[3-(2-hydroxynonyl)]-adenine, enoximone, zaprinast, and sildenafil) were also unable to inhibit this enzyme. However, dipyridamole was a reasonably good inhibitor of this enzyme with an IC50 of 27 microM. cAMP plays key roles in cell growth and differentiation in this parasite, and PDEs are responsible for the hydrolysis of this important second messenger. Therefore, parasite PDEs, including this one, have the potential to be attractive targets for selective drug design.
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Affiliation(s)
- Ana Rascón
- Instituto de Biología Experimental, Universidad Central de Venezuela, Apartado 47.069, Caracas 1041-A, Venezuela.
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21
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Zoraghi R, Seebeck T. The cAMP-specific phosphodiesterase TbPDE2C is an essential enzyme in bloodstream form Trypanosoma brucei. Proc Natl Acad Sci U S A 2002; 99:4343-8. [PMID: 11930001 PMCID: PMC123650 DOI: 10.1073/pnas.062716599] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2001] [Accepted: 12/31/2001] [Indexed: 11/18/2022] Open
Abstract
Chemotherapy of human sleeping sickness, a fatal disease caused by the protozoan parasite Trypanosoma brucei, is in a dismal state, and the identification and characterization of new drug targets is an urgent prerequisite for an improvement of the dramatic situation in the field. Over the last several years, inhibitors of cyclic nucleotide-specific phosphodiesterases have proven to be highly successful drug candidates for an assortment of clinical conditions. Their potential as antiparasitic drugs has not been explored so far. This study reports the characterization of a cAMP-specific phosphodiesterase from T. brucei, TbPDE2C. This enzyme is a class I phosphodiesterase, and it is a member of a small enzyme family in T. brucei, TbPDE2. Inhibitors of this enzyme block the proliferation of bloodstream form trypanosomes in culture. RNA interference experiments demonstrated that the TbPDE2 family, and in particular TbPDE2C, are essential for maintaining intracellular cAMP concentrations within a physiological range. Bloodstream form trypanosomes are exquisitely sensitive to elevated concentrations of intracellular cAMP, and a disruption of TbPDE2C function quickly leads to the disruption of nuclear and cellular cell division, and to cell death. TbPDE2C might represent a novel drug target for the development of new and effective trypanocidal drugs.
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Affiliation(s)
- Roya Zoraghi
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
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22
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Dym O, Xenarios I, Ke H, Colicelli J. Molecular docking of competitive phosphodiesterase inhibitors. Mol Pharmacol 2002; 61:20-5. [PMID: 11752202 DOI: 10.1124/mol.61.1.20] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mammalian phosphodiesterases types 3 and 4 (PDE3 and PDE4) hydrolyze cAMP and are essential for the regulation of this intracellular second messenger. These enzymes share structural and biochemical similarities, but each can be distinguished by its sensitivity to isoenzyme-specific, substrate-competitive inhibitors. We present a model configuration for the PDE4 substrate (cAMP) and a PDE4-specific inhibitor (rolipram) within the active site of the enzyme. The docked models were also used to examine the structural consequences of mutations that confer resistance to rolipram and other PDE4-specific inhibitors. The proposed rolipram-binding configuration is consistent with the substrate-competitive nature of inhibition and also provides a structural basis for the observed specificity of binding to the R- versus S-enantiomer. For mutations that render the enzyme rolipram-insensitive, there was generally an inverse relationship between the magnitude of the drug resistance and the distance of the altered residue from the predicted binding site. We observed a direct correlation between the net loss of protein residue interactions (van der Waals contacts and hydrogen bond interactions) and the degree of rolipram resistance. The positions of several drug sensitivity-determinant residues define a surface leading to the substrate- and drug-binding sites, suggesting a possible approach channel leading to the enzyme active site. The binding of other PDE4 inhibitors (high- and low-affinity) was also modeled and used to predict the involvement of residues that were not previously implicated in pharmacological interactions.
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Affiliation(s)
- Orly Dym
- University of California Los Angeles-Department of Energy Laboratory of Structural Biology and Molecular Medicine, University of California Los Angeles, Los Angeles, California, USA
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23
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Fidock M, Miller M, Lanfear J. Isolation and differential tissue distribution of two human cDNAs encoding PDE1 splice variants. Cell Signal 2002; 14:53-60. [PMID: 11747989 DOI: 10.1016/s0898-6568(01)00207-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A cDNA selection technique has been used to isolate full-length human cDNAs of the phosphodiesterase 1 (PDE1) calcium calmodulin (CaM)-regulated phosphodiesterase gene family. We isolated cDNAs representing multiple splice variants of PDE1A, 1B and 1C from a variety of tissues. Included among these were two novel splice variants for PDE1A and 1B. The first, PDE1A5, encodes a 519-residue protein, which is different from PDE1A1 by the insertion of 14 residues, a divergent carboxy terminus and also differs from PDE1A3 through a divergent amino terminus. Our second novel splice variant represents the first occurrence of a splice variant of the PDE1B gene. PDE1B2 encodes a 516-residue protein and diverges from PDE1B1 by the replacement of the first 38 residues by an alternative 18, which is predicted to be functionally significant. Using the splice variant sequence differences to perform comparative Northern analysis, we have demonstrated that each variant has a differential tissue distribution.
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Affiliation(s)
- Mark Fidock
- Discovery Biology, Pfizer Global Research and Development, Sandwich, Kent CT13 9NJ, UK.
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24
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Zoraghi R, Kunz S, Gong K, Seebeck T. Characterization of TbPDE2A, a novel cyclic nucleotide-specific phosphodiesterase from the protozoan parasite Trypanosoma brucei. J Biol Chem 2001; 276:11559-66. [PMID: 11134002 DOI: 10.1074/jbc.m005419200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
This study reports the identification and characterization of a cAMP-specific phosphodiesterase from the parasitic hemoflagellate Trypanosoma brucei. TbPDE2A is a class I phosphodiesterase. Its catalytic domain exhibits 30-40% sequence identity with those of all 11 mammalian phosphodiesterase (PDE) families, as well as with PDE2 from Saccharomyces cerevisiae, dunce from Drosophila melanogaster, and regA from Dictyostelium discoideum. The overall structure of TbPDE2A resembles that of human PDE11A in that its N-terminal region contains a single GAF domain. This domain is very similar to those of the mammalian PDE2, -5, -6, -10, and -11, where it constitutes a potential cGMP binding site. TbPDE2A can be expressed in S. cerevisiae, and it complements an S. cerevisiae PDE deletion strain. Recombinant TbPDE2A is specific for cAMP, with a K(m) of approximately 2 micrometer. It is entirely resistant to the nonselective PDE inhibitor 3-isobutyl-1-methylxanthine, but it is sensitive to trequinsin, dipyridamole, sildenafil, and ethaverine with IC(50) values of 5.4, 5.9, 9.4, and 14.2 micrometer, respectively. All four compounds inhibit proliferation of bloodstream form trypanosomes in culture, indicating that TbPDE2A is an essential enzyme.
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Affiliation(s)
- R Zoraghi
- Institute for Cell Biology, University of Bern, Baltzerstrasse 4, Berne CH-3012, Switzerland
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25
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Richter W, Unciuleac L, Hermsdorf T, Kronbach T, Dettmer D. Identification of substrate specificity determinants in human cAMP-specific phosphodiesterase 4A by single-point mutagenesis. Cell Signal 2001; 13:159-67. [PMID: 11282454 DOI: 10.1016/s0898-6568(01)00142-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
To identify amino acids that might be involved in discriminating guanosine-3',5'-cyclic phosphate (cGMP) towards adenosine-3',5'-cyclic phosphate (cAMP) binding in the cAMP-specific phosphodiesterases, alignments of different human cyclic nucleotide phosphodiesterases (PDEs) were performed. Eight amino acid residues that are highly conserved in the cAMP-hydrolysing phosphodiesterases (PDE1, PDE3, PDE4, PDE7, PDE8) and that did not show any homologies to the cGMP-specific phosphodiesterases (PDE5, PDE6, PDE9) were selected from these alignments. Using the technique of site-directed mutagenesis, derivatives of PDE4A carrying single mutations at these conserved residues (amino acid positions are given according to the human PDE4A isoform HSPDE4A4B; accession number L20965) were generated and expressed in COS1 cells. The expression products were characterised with regard to cAMP and cGMP hydrolysis and sensitivity towards type-specific inhibitors. The mutation of Phe484 toward Tyr, Ala590 toward Cys, Leu391 and Val501 towards Ala had no significant influence on substrate affinity or specificity. However, the exchange of Trp375 and Trp605 for aliphatic residues abolished catalytic activity and the exchange of Pro595 for Ile led to sevenfold decrease of substrate affinity and an 14-fold decrease of the affinity towards the PDE4-specific inhibitor 4-[3-(cyclopentoxyl)-4-methoxyphenyl]-2-pyrrolidone (rolipram). Both effects may provide evidence for a structural importance of Trp375, Trp605 and Pro595 for PDE function. By exchanging the aspartate residue for asparagine or alanine at position 440 of the human PDE4A4B isoform, the substrate specificity was altered from the highly specific cAMP hydrolysis to an equally efficient cAMP and cGMP binding and hydrolysis. In addition, the IC(50) values for common PDE4-specific inhibitors like rolipram, N-(3,5-dichlorpyrid-4-yl)-3-cyclopentyl-oxy-4-methoxy-benzamide (RPR-73401) and 8-methoxy-5-N-propyl-3-methyl-1-ethyl-imidazo[1,5-a]-pyrido[3,2-e]-pyrazinone (D-22888) were dramatically increased. These results demonstrate an important role of the aspartate at position 440 in determining substrate specificity and inhibitor susceptibility of PDE4A. The strong conservation of this residue suggests that Asp440 may play a similar role in other cAMP-PDEs.
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MESH Headings
- 3',5'-Cyclic-AMP Phosphodiesterases/antagonists & inhibitors
- 3',5'-Cyclic-AMP Phosphodiesterases/genetics
- 3',5'-Cyclic-AMP Phosphodiesterases/metabolism
- Amino Acid Sequence
- Amino Acid Substitution
- Aspartic Acid/genetics
- Binding, Competitive
- Blotting, Western
- Cells, Cultured
- Cyclic AMP/metabolism
- Cyclic GMP/metabolism
- Cyclic Nucleotide Phosphodiesterases, Type 1
- Cyclic Nucleotide Phosphodiesterases, Type 4
- DNA, Complementary/genetics
- Electrophoresis, Polyacrylamide Gel
- Gene Expression Regulation, Enzymologic/drug effects
- Humans
- Isoenzymes/chemistry
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Phosphodiesterase Inhibitors/pharmacology
- Polymerase Chain Reaction
- RNA, Messenger/metabolism
- Rolipram/pharmacology
- Sequence Alignment
- Substrate Specificity/genetics
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Affiliation(s)
- W Richter
- Institute of Biochemistry, Medical Faculty, University of Leipzig, Liebigstrasse 16, D-04103, Leipzig, Germany
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26
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Thompson BE, Freking F, Pho V, Schlinger BA, Cherry JA. Cyclic AMP phosphodiesterases in the zebra finch: distribution, cloning and characterization of a PDE4B homolog. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2000; 83:94-106. [PMID: 11072099 DOI: 10.1016/s0169-328x(00)00201-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Songbirds are important animal models for studying neural mechanisms underlying learning and memory. While evidence has emerged that cAMP plays a significant role in invertebrate and mammalian learning, little is known about the role of cAMP pathways in regulating neuronal function in birds. With the goal of identifying important components of this pathway, we report the first cloning of a cAMP-specific, Type IV phosphodiesterase (PDE4) in a non-mammalian vertebrate. A combination of PCR analysis and cDNA library screening was used to show that homologs of the four known mammalian PDE4 genes also exist in zebra finch. A full-length cDNA representing the zebra finch homolog of PDE4B1 was isolated from a telencephalic library. Expression of this cDNA in human embryonic kidney 293 (HEK) cells yielded an enzyme that hydrolyzed cAMP with a low K(m) and was inhibited by micromolar concentrations of rolipram; these properties are typical of all known mammalian PDE4s. In brain, northern blots revealed transcripts of 3.6 and 4.4 kb in adults, but only the 3.6 kb transcript in juveniles, suggesting that PDE4 expression is developmentally regulated. In situ hybridization of tissue sections demonstrated that PDE4 message was distributed widely throughout the adult zebra finch brain, including regions controlling the learning of songs and the acquisition of spatial memories. These data suggest that PDE4 enzymes may influence a variety of brain functions in these birds and play a role in learning.
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MESH Headings
- 3',5'-Cyclic-AMP Phosphodiesterases/analysis
- 3',5'-Cyclic-AMP Phosphodiesterases/genetics
- 3',5'-Cyclic-AMP Phosphodiesterases/metabolism
- Animals
- Blotting, Northern
- Blotting, Southern
- Brain/enzymology
- Cell Line
- Cloning, Molecular
- Cyclic AMP/metabolism
- Cyclic Nucleotide Phosphodiesterases, Type 4
- DNA, Complementary
- Female
- Gene Expression Regulation, Enzymologic
- Gene Library
- Humans
- In Situ Hybridization
- Kidney/cytology
- Male
- Molecular Sequence Data
- Polymerase Chain Reaction
- Protein Biosynthesis
- RNA, Messenger/analysis
- Sequence Homology, Amino Acid
- Songbirds
- Transcription, Genetic
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Affiliation(s)
- B E Thompson
- Department of Psychology and Laboratory of Molecular Neurobiology and Behavior, Boston University, 64 Cummington Street, Boston, MA 02215, USA
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27
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Affiliation(s)
- M Conti
- Department of Gynecology and Obstetrics, Stanford University School of Medicine, California 94305-5317, USA
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28
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Conti M, Jin SL. The molecular biology of cyclic nucleotide phosphodiesterases. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1999; 63:1-38. [PMID: 10506827 DOI: 10.1016/s0079-6603(08)60718-7] [Citation(s) in RCA: 352] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Recent progress in the field of cyclic nucleotides has shown that a large array of closely related proteins is involved in each step of the signal transduction cascade. Nine families of adenylyl cyclases catalyze the synthesis of the second messenger cAMP, and protein kinases A, the intracellular effectors of cAMP, are composed of four regulatory and three catalytic subunits. A comparable heterogeneity has been discovered for the enzymes involved in the inactivation of cyclic nucleotide signaling. In mammals, 19 different genes encode the cyclic nucleotide phosphodiesterases (PDEs), the enzymes that hydrolyze and inactivate cAMP and cGMP. This is only an initial level of complexity, because each PDE gene contains several distinct transcriptional units that give rise to proteins with subtle structural differences, bringing the number of the PDE proteins close to 50. The molecular biology of PDEs in Drosophila and Dictyostelium has shed some light on the role of PDE diversity in signaling and development. However, much needs to be done to understand the exact function of these enzymes, particularly during mammalian development and cell differentiation. With the identification and mapping of regulatory and targeting domains of the PDEs, modularity of the PDE structure is becoming an established tenet in the PDE field. The use of different transcriptional units and exon splicing of a single PDE gene generates proteins with different regulatory domains joined to a common catalytic domain, therefore expanding the array of isoforms with subtle differences in properties and sensitivities to different signals. The physiological context in which these different isoforms function is still largely unknown and undoubtedly will be a major area of expansion in the years to come.
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Affiliation(s)
- M Conti
- Department of Gynecology and Obstetrics, Stanford University School of Medicine, California 94305, USA
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29
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Snyder PB, Florio VA, Ferguson K, Loughney K. Isolation, expression and analysis of splice variants of a human Ca2+/calmodulin-stimulated phosphodiesterase (PDE1A). Cell Signal 1999; 11:535-44. [PMID: 10405764 DOI: 10.1016/s0898-6568(99)00027-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The PDE1A gene encodes a Ca2+/calmodulin-stimulated 3',5'-cyclic nucleotide phosphodiesterase (PDE). We have performed 5' and 3' RACE and identified two additional 5'-splice variants and one additional 3'-splice variant of the human PDE1A gene. The three known 5'-splice variants and the two known 3'-splice variants combine to generate six different PDE1A mRNAs. However, one of the 5'-splice variants exhibits alternate splicing in the 5' untranslated region. Thus the six mRNAs encode four different PDE1A proteins. Recombinant forms of the different human PDE1A isoforms were expressed in Sf9 cells. The kinetic properties and inhibitor sensitivities of the four PDE1A isoforms are very similar to one another.
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Affiliation(s)
- P B Snyder
- ICOS Corporation, Bothell, WA 98021, USA.
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30
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McPhee I, Yarwood SJ, Scotland G, Huston E, Beard MB, Ross AH, Houslay ES, Houslay MD. Association with the SRC family tyrosyl kinase LYN triggers a conformational change in the catalytic region of human cAMP-specific phosphodiesterase HSPDE4A4B. Consequences for rolipram inhibition. J Biol Chem 1999; 274:11796-810. [PMID: 10206997 DOI: 10.1074/jbc.274.17.11796] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cAMP-specific phosphodiesterase (PDE) HSPDE 4A4B(pde46) selectively bound SH3 domains of SRC family tyrosyl kinases. Such an interaction profoundly changed the inhibition of PDE4 activity caused by the PDE4-selective inhibitor rolipram and mimicked the enhanced rolipram inhibition seen for particulate, compared with cytosolic pde46 expressed in COS7 cells. Particulate pde46 co-localized with LYN kinase in COS7 cells. The unique N-terminal and LR2 regions of pde46 contained the sites for SH3 binding. Altered rolipram inhibition was triggered by SH3 domain interaction with the LR2 region. Purified LYN SH3 and human PDE4A LR2 could be co-immunoprecipitated, indicating a direct interaction. Protein kinase A-phosphorylated pde46 remained able to bind LYN SH3. pde46 was found to be associated with SRC kinase in the cytosol of COS1 cells, leading to aberrant kinetics of rolipram inhibition. It is suggested that pde46 may be associated with SRC family tyrosyl kinases in intact cells and that the ensuing SH3 domain interaction with the LR2 region of pde46 alters the conformation of the PDE catalytic unit, as detected by altered rolipram inhibition. Interaction between pde46 and SRC family tyrosyl kinases highlights a potentially novel regulatory system and point of signaling system cross-talk.
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Affiliation(s)
- I McPhee
- Division of Biochemistry & Molecular Biology, IBLS, Davidson Building, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
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31
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Atienza JM, Susanto D, Huang C, McCarty AS, Colicelli J. Identification of inhibitor specificity determinants in a mammalian phosphodiesterase. J Biol Chem 1999; 274:4839-47. [PMID: 9988724 DOI: 10.1074/jbc.274.8.4839] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mammalian phosphodiesterase types 3 and 4 (PDE3 and PDE4) hydrolyze cAMP and are essential for the regulation of this intracellular second messenger in many cell types. Whereas these enzymes share structural and biochemical similarities, each can be distinguished by its sensitivity to isozyme-specific inhibitors. By using a series of chimeric enzymes, we have localized the region of PDE4 that confers sensitivity to selective inhibitors. This inhibitor specificity domain lies within a short sequence at the carboxyl terminus of the catalytic domain of the protein, consistent with the competitive nature of inhibition by these compounds. Surprisingly, the identified region also includes some of the most highly conserved residues among PDE isoforms. A yeast-based expression system was used for the isolation and characterization of mutations within this area that confer resistance to the PDE4-specific inhibitor rolipram. Analysis of these mutants indicated that both conserved and unique residues are required for isoform-specific inhibitor sensitivity. In some cases, combined point mutations contribute synergistically to the reduction of sensitivity (suppression of IC50). We also report that several mutations display differential sensitivity changes with respect to distinct structural classes of inhibitors.
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Affiliation(s)
- J M Atienza
- Department of Biological Chemistry and the Molecular Biology Institute, UCLA School of Medicine, Los Angeles, California 90095, USA
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32
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Hoffmann R, Wilkinson IR, McCallum JF, Engels P, Houslay MD. cAMP-specific phosphodiesterase HSPDE4D3 mutants which mimic activation and changes in rolipram inhibition triggered by protein kinase A phosphorylation of Ser-54: generation of a molecular model. Biochem J 1998; 333 ( Pt 1):139-49. [PMID: 9639573 PMCID: PMC1219566 DOI: 10.1042/bj3330139] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Ser-13 and Ser-54 were shown to provide the sole sites for the protein kinase A (PKA)-mediated phosphorylation of the human cAMP-specific phosphodiesterase isoform HSPDE4D3. The ability of PKA to phosphorylate and activate HSPDE4D3 was mimicked by replacing Ser-54 with either of the negatively charged amino acids, aspartate or glutamate, within the consensus motif of RRES54. The PDE4 selective inhibitor rolipram ¿4-[3-(cyclopentoxy)-4-methoxyphenyl]-2-pyrrolidone¿ inhibited both PKA-phosphorylated HSPDE4D3 and the Ser-54-->Asp mutant, with an IC50 value that was approximately 8-fold lower than that seen for the non-PKA-phosphorylated enzyme. Lower IC50 values for inhibition by rolipram were seen for a wide range of non-activated residue 54 mutants, except for those which had side-chains able to serve as hydrogen-bond donors, namely the Ser-54-->Thr, Ser-54-->Tyr and Ser-54-->Cys mutants. The Glu-53-->Ala mutant exhibited an activity comparable with that of the PKA phosphorylated native enzyme and the Ser-54-->Asp mutant but, in contrast to the native enzyme, was insensitive to activation by PKA, despite being more rapidly phosphorylated by this protein kinase. The activated Glu-53-->Ala mutant exhibited a sensitivity to inhibition by rolipram which was unchanged from that of the native enzyme. The double mutant, Arg-51-->Ala/Arg-52-->Ala, showed no change in either enzyme activity or rolipram inhibition from the native enzyme and was incapable of providing a substrate for PKA phosphorylation at Ser-54. No difference in inhibition by dipyridamole was seen for the native enzyme and the Ser-54-->Asp and Ser-54-->Ala mutants. A model is proposed which envisages that phosphorylation by PKA triggers at least two distinct conformational changes in HSPDE4D3; one of these gives rise to enzyme activation and another enhances sensitivity to inhibition by rolipram. Activation of HSPDE4D3 by PKA-mediated phosphorylation is suggested to involve disruption of an ion-pair interaction involving the negatively charged Glu-53. The increase in susceptibility to inhibition by rolipram upon PKA-mediated phosphorylation is suggested to involve the disruption of a hydrogen-bond involving the side-chain hydroxy group of Ser-54.
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Affiliation(s)
- R Hoffmann
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Davidson and Wolfson Buildings, IBLS, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K
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33
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Saldou N, Obernolte R, Huber A, Baecker PA, Wilhelm R, Alvarez R, Li B, Xia L, Callan O, Su C, Jarnagin K, Shelton ER. Comparison of recombinant human PDE4 isoforms: interaction with substrate and inhibitors. Cell Signal 1998; 10:427-40. [PMID: 9720765 DOI: 10.1016/s0898-6568(97)00169-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Four cyclic-nucleotide phosphodiesterase (PDE) genes belonging to the PDE4 family (PDE4A, 4B, 4C and 4D) have been identified. All four isogenes, including several deletions and alterations of the amino, carboxyl and central catalytic domains, were expressed in insect cells. Lysates were characterised for enzyme activity by using the Km for substrate and the EC50 for activation by the cofactor Mg2+. The catalytic domain alone appears to be sufficient for the normal enzymatic function of PDE4 proteins. Substrate affinity varied by less than 2-fold between catalytic-domain forms of the PDE4A, 4B and 4D isogenes and the long forms (PDE4A5, PDE4B1 and PDE4D3). The affinity for Mg2+ varied by less than 4-fold between long and catalytic-domain forms of PDE4A and 4B. The catalytic-domain form of PDE4D, however, had a 12-fold lower affinity for Mg2+ that was restored by including a portion of the amino-terminal domain, upstream conserved region-2 (UCR2). This result suggests that the Mg2+-binding site of PDE4D involves the UCR2 region. Inhibition of the PDE4 proteins by synthetic compounds is apparently affected differently by the domains. For PDE4B, the catalytic domain is sufficient for interactions with the inhibitors studied: IBMX, trequinsin, rolipram, TVX 2706, RP 73401 and RS-25344. For PDE4D the catalytic-domain form is less sensitive than the long form to inhibition by RS-25344, rolipram and TVX 2706, by 1463-, 11-and 12-fold, respectively. Addition of UCR2 to the catalytic-domain form of PDE4D restored all the lost sensitivities. The catalytic-domain form of PDE4A showed a reduced inhibitor affinity with RS-25344 and TVX 2706 by 77- and 90-fold, respectively. Both catalytic-domain and long forms of PDE4 isogenes interacted with equal affinity with the non-specific inhibitors IBMX and trequinsin, as well as the very potent PDE4-specific inhibitor RP 73401. Other potent and specific PDE4 inhibitors, such as rolipram, RS-25344 or TVX 2706, appear to utilize non-catalytic domain interactions with PDE4D and 4A to supplement those within the catalytic domains. These observations suggest a different relation between amino and catalytic domains in PDE4D relative to PDE4B. We therefore propose a model to illustrate these isogene-specific PDE4 domain interactions with substrate, inhibitors and the co-factor Mg2+. The model for PDE4D is also discussed in relation to changes in the activation curve for Mg2+ and sensitivity to RS-25344 that accompany phosphorylation of the long form by protein kinase A.
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Affiliation(s)
- N Saldou
- Roche Bioscience, Palo Alto, California 94304, USA
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34
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Houslay MD, Sullivan M, Bolger GB. The multienzyme PDE4 cyclic adenosine monophosphate-specific phosphodiesterase family: intracellular targeting, regulation, and selective inhibition by compounds exerting anti-inflammatory and antidepressant actions. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1998; 44:225-342. [PMID: 9547887 DOI: 10.1016/s1054-3589(08)60128-3] [Citation(s) in RCA: 229] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- M D Houslay
- Division of Biochemistry and Molecular Biology, University of Glasgow, Scotland, UK
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35
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Saldou N, Baecker PA, Li B, Yuan Z, Obernolte R, Ratzliff J, Osen E, Jarnagin K, Shelton ER. Purification and physical characterization of cloned human cAMP phosphodiesterases PDE-4D and -4C. Cell Biochem Biophys 1998; 28:187-217. [PMID: 9515166 DOI: 10.1007/bf02737811] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Individual isozymes of family four cyclic-nucleotide phosphodiesterases (PDE-4s) were characterized and compared in order to advance our understanding of how PDE-4s regulate cAMP levels in cells. Full-length and shorter clones containing various functional domains were constructed and overexpressed using a recombinant baculovirus-infected Sf9 insect cell system. One form each of PDE-4C and 4D was purified 125- and 534-fold, respectively, using anion-exchange and affi-gel blue chromatography. The purified material was unaltered in size on SDS-polyacrylamide gels during purification and nearly homogeneous (> 95%) as estimated by both staining and immunoblotting. Approximately 1 mg of PDE-4D (74.7 kDa) and 3.7 mg of PDE-4C (61.4 kDa) could be isolated from a 6-L culture of cells. The physical characteristics of Stokes' radius and sedimentation coefficient for PDE-4 enzymes cloned from each of the four isogenes were determined using size-exclusion chromatography and sedimentation in glycerol gradients. Calculations indicate that both long and short forms can form dimers, although evidence for monomers and higher-order subunit association was seen. Furthermore, the results clearly show that all long and short forms of PDE-4 are highly asymmetric molecules. This work has shown that large amounts of PDE-4 proteins can be purified and characterized physically and enzymatically to yield information that will enable a greater understanding of how PDE-4 enzymes function in cells.
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Affiliation(s)
- N Saldou
- Roche Bioscience, Palo Alto, CA 94304, USA
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36
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Abstract
Facile manipulation and rapid regeneration have helped to establish the yeast Saccharomyces cerevisiae as a genetic workhorse. More recently, these simple eukaryotes have been used for the biochemical analysis of mammalian proteins. This article describes the use of a yeast expression system for both in vitro and in vivo assays of mammalian phosphodiesterase (PDE) activity using yeast cells devoid of endogenous PDEs. It also presents simple methodologies for the analysis of the pharmacological properties of mammalian PDEs and describes the use of a powerful genetic selection for mutant forms of PDEs with altered biochemical and pharmacological characteristics.
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Affiliation(s)
- J M Atienza
- University of California, Los Angeles, School of Medicine, 33-257 CHS, Los Angeles, California 90095-1737, USA
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37
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Bolger GB, Erdogan S, Jones RE, Loughney K, Scotland G, Hoffmann R, Wilkinson I, Farrell C, Houslay MD. Characterization of five different proteins produced by alternatively spliced mRNAs from the human cAMP-specific phosphodiesterase PDE4D gene. Biochem J 1997; 328 ( Pt 2):539-48. [PMID: 9371713 PMCID: PMC1218953 DOI: 10.1042/bj3280539] [Citation(s) in RCA: 165] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have isolated and characterized complete cDNAs for two isoforms (HSPDE4D4 and HSPDE4A5) encoded by the human PDE4D gene, one of four genes that encode cAMP-specific rolipram-inhibited 3',5'-cyclic nucleotide phosphodiesterases (type IVPDEs; PDE4 family). The HSPDE4D4 and HSPDE4D5 cDNAs encode proteins of 810 and 746 amino acids respectively. A comparison of the nucleotide sequences of these two cDNAs with those encoding the three other human PDE4D proteins (HSPDE4D1, HSPDE4D2 and HSPDE4D3) demonstrates that each corresponding mRNA transcript has a unique region of sequence at or near its 5'-end, consistent with alternative mRNA splicing. Transient expression of the five cDNAs in monkey COS-7 cells produced proteins of apparent molecular mass under denaturing conditions of 68, 68, 95, 119 and 105 kDa for isoforms HSPDE4D1-5 respectively. Immunoblotting of human cell lines and rat brain demonstrated the presence of species that co-migrated with the proteins produced in COS-7 cells. COS-cell-expressed and native HSPDE4D1 and HSPDE4D2 were found to exist only in the cytosol, whereas HSPDE4D3, HSPDE4D4 and HSPDE4D5 were found in both cytosolic and particulate fractions. The IC50 values for the selective PDE4 inhibitor rolipram for the cytosolic forms of the five enzymes were similar (0.05-0.14 microM), whereas they were 2-7-fold higher for the particulate forms of HSPDE4D3 and HSPDE4D5 (0.32 and 0.59 microM respectively), than for the corresponding cytosolic forms. Our data indicate that the N-terminal regions of the HSPDE4D3, HSPDE4D4 and HSPDE4D5 proteins, which are derived from alternatively spliced regions of their mRNAs, are important in determining their subcellular localization, activity and differential sensitivity to inhibitors.
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Affiliation(s)
- G B Bolger
- Department of Veterans Affairs Medical Center, 151M, and Huntsman Cancer Institute, Department of Oncologic Sciences and Department of Medicine (Hematology/Oncology) University of Utah Health Sciences Center, Salt Lake City, UT 84148, USA
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38
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Sibley CH, Brophy VH, Cheesman S, Hamilton KL, Hankins EG, Wooden JM, Kilbey B. Yeast as a model system to study drugs effective against apicomplexan proteins. Methods 1997; 13:190-207. [PMID: 9405202 DOI: 10.1006/meth.1997.0511] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Biochemical and genetic analyses are required to identify potential drug targets in apicomplexan parasites, but these studies have proved difficult in most parasite systems. We have developed methods based on expression of parasite proteins in the budding yeast, Saccharomyces cerevisiae, to rapidly screen drugs directed against particular parasite targets, to study the structure and function of these target molecules, and to identify mutations in the parasite genes that alter enzyme specificity or drug sensitivity. In this paper we outline the parameters that need to be considered to design yeast strains that function efficiently to assay function of parasite proteins. Basic protocols and methods are included. We detail some problems that might be encountered in the engineering of these yeast strains and suggest possible solutions.
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Affiliation(s)
- C H Sibley
- Department of Genetics, University of Washington, Seattle, Washington, 98195-7360, USA.
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39
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Obernolte R, Ratzliff J, Baecker PA, Daniels DV, Zuppan P, Jarnagin K, Shelton ER. Multiple splice variants of phosphodiesterase PDE4C cloned from human lung and testis. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1353:287-97. [PMID: 9349724 DOI: 10.1016/s0167-4781(97)00080-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Four closely related cyclic-nucleotide specific phosphodiesterase (PDE4) genes have been identified in both humans and rats: PDE4A, 4B, 4C and 4D. We have now cloned cDNAs for multiple splice variants of human PDE4C. Two splice variants, PDE4C-791 and PDE4C-426, were isolated from a fetal lung library. The longest open reading frame (ORF) of 791 amino acids (aa) is encoded by PDE4C-791, which is similar to a recently described cDNA [Engels, P., Sullivan, M., Muller, T. and Lubbert, H. FEBS Lett. 358 (1995) 305-10], except that an alternative 5'-end sequence upstream of the first methionine extends the PDE4C-791 ORF by 79 aa. The PDE4C-426 variant contains 3 insertions that are located 5' to the catalytic domain and encode several in-frame stop codons. The predicted 426 aa protein initiates at a methionine 365 aa within PDE4C-791. A baculovirus clone starting at this methionine expressed an enzymatically active protein. Two additional splice variants, PDE4C-delta54 and PDE4C-delta109, were found in testis mRNA. PDE4C-delta54 contained a novel 5'-end region and a deletion of 162 nt; the predicted protein deletes 54 aa from the amino-terminal region. The PDE4C-delta54 protein produced in baculovirus-infected cells was enzymatically active and sensitive to PDE4-specific inhibitors. The PDE4C-delta109 protein is similar to PDE4C-delta54 but has an additional 55 aa deleted in the catalytic domain; it lacked enzymatic activity. Analysis of uncloned total mRNA from 4 tissue sources by polymerase chain reaction (PCR) confirmed the presence of mRNAs with the two deletions and three insertions that we observed in cDNA clones. The PDE4C-delta54 variant was found only in testis and the 5'-extended region of PDE4C-791 was seen only in lung and the melanoma cell line G361. Hence, tissue-specific expression of various PDE4C isoforms should be considered in understanding how these gene products modulate cellular responses to cAMP.
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MESH Headings
- 3',5'-Cyclic-AMP Phosphodiesterases/chemistry
- 3',5'-Cyclic-AMP Phosphodiesterases/genetics
- Amino Acid Sequence
- Base Sequence
- Cloning, Molecular
- Cyclic Nucleotide Phosphodiesterases, Type 4
- DNA, Complementary/genetics
- Fetus
- Gene Expression Regulation, Enzymologic/drug effects
- Humans
- Lung/enzymology
- Male
- Melanoma
- Molecular Sequence Data
- Molecular Weight
- Organ Specificity
- Phosphodiesterase Inhibitors/pharmacology
- Pyrrolidinones/pharmacology
- RNA Splicing/genetics
- RNA, Messenger/analysis
- RNA, Messenger/genetics
- Recombinant Proteins
- Rolipram
- Sequence Analysis, DNA
- Sequence Deletion/genetics
- Testis/enzymology
- Tumor Cells, Cultured
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40
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Jacobitz S, Ryan MD, McLaughlin MM, Livi GP, DeWolf WE, Torphy TJ. Role of conserved histidines in catalytic activity and inhibitor binding of human recombinant phosphodiesterase 4A. Mol Pharmacol 1997; 51:999-1006. [PMID: 9187266 DOI: 10.1124/mol.51.6.999] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
To identify critical amino acids within the central conserved region of recombinant human cAMP-specific phosphodiesterase 4 subtype A (rhPDE4A), we engineered the expression of point mutants in a fully active rhPDE4A/Met201-886. When histidine residues at positions 433, 437, 473, and 477, which are highly conserved among all PDE families, were changed independently to serine residues, cAMP hydrolyzing activities were substantially reduced or abolished. The ability of these mutants to bind prototypical PDE4 inhibitors [3H]-(R)-rolipram or [3H]RP 73401 was also decreased in parallel with the loss of catalytic activity. The parallel loss of catalytic activity and inhibitor binding suggests that these changes resulted from non-localized perturbations in the structure of the enzyme. More interesting results were obtained when histidine residues at positions 505 and 506 were changed independently to aspar agines. The K(m) value for cAMP increased 3-fold in H505N (K(m) = 11 +/- 3 microM) and 11-fold in H506N (K(m) = 44 +/- 6 microM) compared with the wild-type protein (K(m) = 4 +/- 1 microM). These mutant proteins bound [3H]-(R)-rolipram and [3H]RP 73401 with K(d) values of 1.8 +/- 0.4 and 0.3 +/- 0.1 nM, respectively, for H505N, and 3.9 +/- 0.9 and 0.5 +/- 0.1 nM, respectively, for H506N. These values are nearly identical to those obtained with the wild-type rhPDE4A/Met201-886. In contrast, the IC50 values for cAMP competition with either [3H]-(R)-rolipram or [3H]RP 73401 binding increased approximately 2-fold in H505N and approximately 13-fold in H506N compared with the wild type protein. These increases are virtually identical to the changes in the K(m) value for cAMP in these mutants. We conclude that His506 and, perhaps, His505 are involved in binding of cAMP to PDE4A/Met201-886 but not in binding of PDE4-selective inhibitors.
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Affiliation(s)
- S Jacobitz
- Department of Pulmonary Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406, USA
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41
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Wooden JM, Hartwell LH, Vasquez B, Sibley CH. Analysis in yeast of antimalaria drugs that target the dihydrofolate reductase of Plasmodium falciparum. Mol Biochem Parasitol 1997; 85:25-40. [PMID: 9108546 DOI: 10.1016/s0166-6851(96)02808-3] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Pyrimethamine and cycloguanil are competitive inhibitors of the Plasmodium enzyme dihydrofolate reductase (DHFR). They have been effective treatments for malaria, but rapid selection of populations of the parasite resistant to these drugs has compromised their effectiveness. Parasites resistant to either drug usually have point mutations in the dhfr gene, but the frequency of these mutations is unknown. To study drug resistance more effectively, we transferred the DHFR domain of the dhfr-thymidylate synthase gene from a drug-sensitive line of P. falciparum to a strain of the budding yeast, Saccharomyces cerevisiae, that lacks endogenous DHFR activity. Expression of the P. falciparum dhfr is controlled by the yeast dhfr 5' and 3' regulatory regions and the heterologous enzyme provided all of the functions of the yeast dhfr gene. These yeast were susceptible to pyrimethamine and cycloguanil at low concentrations that inhibit P. falciparum (IC50 about 10(-8) and 10(-7) M, respectively). Yeast expressing constructs with dhfr alleles from pyrimethamine-resistant strains were resistant to both pyrimethamine and cycloguanil (IC50 > 10(-6) M); resistance of the yeast depended on the dhfr allele they expressed. The experimental drug WR99210 efficiently killed all three yeast strains (IC50 about 10(-8) M) but the pyrR strains showed collateral hypersensitivity to drug. The yeast transformants carrying the drug-sensitive allele can now be screened quickly and quantitatively to identify new drugs or combinations of drugs and determine which drugs select resistant parasites least efficiently. Such compounds would be excellent candidates for development of treatments with a longer life in clinical practice.
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Affiliation(s)
- J M Wooden
- Department of Genetics, University of Washington, Seattle 98195-7360, USA
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Rocque WJ, Holmes WD, Patel IR, Dougherty RW, Ittoop O, Overton L, Hoffman CR, Wisely GB, Willard DH, Luther MA. Detailed characterization of a purified type 4 phosphodiesterase, HSPDE4B2B: differentiation of high- and low-affinity (R)-rolipram binding. Protein Expr Purif 1997; 9:191-202. [PMID: 9056484 DOI: 10.1006/prep.1996.0683] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We have overexpressed in a baculovirus expression system, and purified to > 95% homogeneity, milligram quantities of a human recombinant rolipram-sensitive cAMP phosphodiesterase, HSPDE4B2B (amino acid residues 81-564). The protein expression levels were approximately 8 mg of HSPDE4B2B (81-564) per liter of Sf9 cells. The Km of the purified enzyme for cAMP was 4 microM and the Ki for the Type 4 phosphodiesterase-specific inhibitor (R)-rolipram was 0.6 microM. The specific activity of the purified protein was 40 mumol/min/mg protein. A nonequilibrium filter binding assay revealed a high-affinity (R)-rolipram binding site on the purified enzyme with a Kd of 1.5 nM and a stoichiometry of 0.05-0.3 mol of (R)-rolipram per mol of HSPDE4B2B (81-564). Equilibrium dialysis experiments revealed a single binding constant of 140 nM with a stoichiometry of 0.75 mol of (R)-rolipram per mol of HSPDE4B2B (81-564). Size exclusion chromatography and analytical ultracentrifugation experiments suggest that the protein exists in multiple association states larger than a monomer. Proteolysis experiments revealed a 43-kDa fragment that contained catalytic and rolipram-inhibitable activities, but the fragment showed no high-affinity (R)-rolipram binding. Based on the proteolytic cleavage studies a 43-kDa protein was constructed, expressed, and purified. This protein, HSPDE4B2B (152-528), had Km and Vmax similar to those of the HSPDE4B2B (81-564) protein, but did not exhibit high-affinity (R)-rolipram binding. The protein did show low-affinity (R)-rolipram binding using the equilibrium binding assay. These results show that a low-affinity binding site for (R)-rolipram is solely contained within the catalytic domain of HSPDE4B2B, whereas high-affinity (R)-rolipram binding requires residues within the catalytic domain and residues flanking N- and/or C-terminal to the catalytic region.
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Affiliation(s)
- W J Rocque
- Department of Molecular Sciences, Glaxo Wellcome, Inc., Research Triangle Park, North Carolina 27709, USA
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Spain BH, Bowdish KS, Pacal AR, Staub SF, Koo D, Chang CY, Xie W, Colicelli J. Two human cDNAs, including a homolog of Arabidopsis FUS6 (COP11), suppress G-protein- and mitogen-activated protein kinase-mediated signal transduction in yeast and mammalian cells. Mol Cell Biol 1996; 16:6698-706. [PMID: 8943324 PMCID: PMC231672 DOI: 10.1128/mcb.16.12.6698] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We have isolated two novel human cDNAs, gps1-1 and gps2, that suppress lethal G-protein subunit-activating mutations in the pheromone response pathway of the yeast Saccharomyces cerevisiae. Suppression of other pathway-activating events was examined. In wild-type cells, expression of either gps1-1 or gps2 led to enhanced recovery from cell cycle arrest induced by pheromone. Sequence analysis indicated that gps1-1 contains only the carboxy-terminal half of the gps1 coding sequence. The predicted gene product of gps1 has striking similarity to the protein encoded by the Arabidopsis FUS6 (COP11) gene, a negative regulator of light-mediated signal transduction that is known to be essential for normal development. A chimeric construct containing gps1 and FUS6 sequences also suppressed the yeast pheromone pathway, indicating functional conservation between these human and plant genes. In addition, when overexpressed in mammalian cells, gps1 or gps2 potently suppressed a RAS- and mitogen-activated protein kinase-mediated signal and interfered with JNK activity, suggesting that signal repression is part of their normal function. For gps1, these results are consistent with the proposed function of FUS6 (COP11) as a signal transduction repressor in plants.
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Affiliation(s)
- B H Spain
- Department of Biological Chemistry and Molecular Biology Institute, UCLA School of Medicine, Los Angeles, California 90095, USA
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Yu C, Kennedy NJ, Chang CC, Rothblatt JA. Molecular cloning and characterization of two isoforms of Saccharomyces cerevisiae acyl-CoA:sterol acyltransferase. J Biol Chem 1996; 271:24157-63. [PMID: 8798656 DOI: 10.1074/jbc.271.39.24157] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Esterification of cholesterol by acyl-CoA:cholesterol acyltransferase (ACAT) is a key element in maintaining cholesterol homeostasis in cells of higher animals. In the budding yeast, Saccharomyces cerevisiae, accumulation of ergosteryl esters accompanies entry into stationary phase and sporulation. We have determined that two genes in yeast, SAT1 and SAT2, encode isozymes of acyl-CoA:sterol acyltransferase (ASAT) which are functionally related to ACAT. The SAT1 isozyme is the major catalytic isoform, accounting for at least 65-75% of total ASAT activity. Targeted deletions of one or both genes do not compromise mitotic cell growth or spore germination. However, diploids that are homozygous for a SAT1 null mutation exhibit significantly reduced sporulation efficiency. Furthermore, a larger fraction of the sporulating diploids arrest after the first meiotic division. Human ACAT expressed in sat1 sat2 mutant cells can catalyze esterification of cholesterol and, to a lesser extent, ergosterol in vitro, but restores ergosteryl oleate formation in vivo to only approximately 8% of that catalyzed by yeast ASAT in wild-type cells.
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Affiliation(s)
- C Yu
- Department of Biological Sciences, Dartmouth College, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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Müller T, Engels P, Fozard JR. Subtypes of the type 4 cAMP phosphodiesterases: structure, regulation and selective inhibition. Trends Pharmacol Sci 1996; 17:294-8. [PMID: 8810876 DOI: 10.1016/0165-6147(96)10035-3] [Citation(s) in RCA: 128] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The 'famille nombreuse' of cyclic nucleotide phosphodiesterases, responsible for degrading the ubiquitous second messenger molecules, cAMP and cGMP, maintains its place as a major focus of interest for many research laboratories in both academia and industry. The increase in knowledge of the primary sequences, plus the availability of selective inhibitors, are rapidly improving our insight into the structure, regulation and function of these pivotal enzymes of cellular homeostasis. Here, Thomas Müller, Peter Engels and John Fozard focus on family 4 of the phosphodiesterases, which is of particular interest owing to both the number of genes (and splice variants) and the emergence of selective inhibitors, which are enabling the functional significance of these enzymes to be defined.
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Affiliation(s)
- T Müller
- Asthma Research Department, Sandoz Pharma Ltd, Basel, Switzerland
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Spain BH, Koo D, Ramakrishnan M, Dzudzor B, Colicelli J. Truncated forms of a novel yeast protein suppress the lethality of a G protein alpha subunit deficiency by interacting with the beta subunit. J Biol Chem 1995; 270:25435-44. [PMID: 7592711 DOI: 10.1074/jbc.270.43.25435] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
In Saccharomyces cerevisiae, the mating pheromone-initiated signal is transduced by a heterotrimeric G protein and normally results in transient cell cycle arrest and differentiation. A null allele of the G alpha (GPA1/SCG1) subunit results in cell death due to unchecked signaling from the G beta gamma (STE4, STE18, respectively) heterodimer. We have identified three high copy suppressors of gpa1 lethality. Two of these genes encode known transcription factors. Mat alpha 2p and Mcm1p. The third is a truncated form of a novel gene, SYG1. Overexpressed wild type SYG1 is a weak suppressor of gpa1. In contrast, the isolated mutant allele SYG1-1 is a strong suppressor that completely blocks the cell cycle arrest and differentiation phenotypes of gpa1 cells of both mating types. One deletion mutant (SYG1 delta 340) can suppress the cell cycle arrest associated with gpa1, but the cells retain a differentiated morphology. SYG1-1 can suppress the effects of overexpressed wild type G beta but is not able to suppress the lethality of an activated G beta mutant (STE4Hpl). Consistent with these genetic observations, the suppressing form of Syg1p can interact with the STE4 gene product, as determined by a two-hybrid assay. SYG1-1 is also capable of promoting pheromone recovery in wild type cells, as judged by halo assay. The sequence of SYG1 predicts eight membrane-spanning domains. Deletion mutants of SYG1 indicate that complete gpa1 suppression requires removal of all of these hydrophobic regions. Interestingly, this truncated protein localizes to the same plasma membrane-enriched subcellular fraction as does full-length Syg1p. Three hypothetical yeast proteins, identified by their similarity to the SYG1 primary sequence within the gpa1 suppression domain, also appear to have related structures. The properties of Syg1p are consistent with those of a transmembrane signaling component that can respond to, or transduce signals through, G beta or G beta gamma.
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Affiliation(s)
- B H Spain
- Department of Biological Chemistry, UCLA School of Medicine 90024, USA
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Pillai R, Staub SF, Colicelli J. Mutational mapping of kinetic and pharmacological properties of a human cardiac cAMP phosphodiesterase. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)43866-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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