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Jomova K, Makova M, Alomar SY, Alwasel SH, Nepovimova E, Kuca K, Rhodes CJ, Valko M. Essential metals in health and disease. Chem Biol Interact 2022; 367:110173. [PMID: 36152810 DOI: 10.1016/j.cbi.2022.110173] [Citation(s) in RCA: 195] [Impact Index Per Article: 97.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 08/10/2022] [Accepted: 09/05/2022] [Indexed: 11/03/2022]
Abstract
In total, twenty elements appear to be essential for the correct functioning of the human body, half of which are metals and half are non-metals. Among those metals that are currently considered to be essential for normal biological functioning are four main group elements, sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca), and six d-block transition metal elements, manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn) and molybdenum (Mo). Cells have developed various metallo-regulatory mechanisms for maintaining a necessary homeostasis of metal-ions for diverse cellular processes, most importantly in the central nervous system. Since redox active transition metals (for example Fe and Cu) may participate in electron transfer reactions, their homeostasis must be carefully controlled. The catalytic behaviour of redox metals which have escaped control, e.g. via the Fenton reaction, results in the formation of reactive hydroxyl radicals, which may cause damage to DNA, proteins and membranes. Transition metals are integral parts of the active centers of numerous enzymes (e.g. Cu,Zn-SOD, Mn-SOD, Catalase) which catalyze chemical reactions at physiologically compatible rates. Either a deficiency, or an excess of essential metals may result in various disease states arising in an organism. Some typical ailments that are characterized by a disturbed homeostasis of redox active metals include neurological disorders (Alzheimer's, Parkinson's and Huntington's disorders), mental health problems, cardiovascular diseases, cancer, and diabetes. To comprehend more deeply the mechanisms by which essential metals, acting either alone or in combination, and/or through their interaction with non-essential metals (e.g. chromium) function in biological systems will require the application of a broader, more interdisciplinary approach than has mainly been used so far. It is clear that a stronger cooperation between bioinorganic chemists and biophysicists - who have already achieved great success in understanding the structure and role of metalloenzymes in living systems - with biologists, will access new avenues of research in the systems biology of metal ions. With this in mind, the present paper reviews selected chemical and biological aspects of metal ions and their possible interactions in living systems under normal and pathological conditions.
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Affiliation(s)
- Klaudia Jomova
- Department of Chemistry, Faculty of Natural Sciences and Informatics, Constantine The Philosopher University in Nitra, 949 01, Nitra, Slovakia
| | - Marianna Makova
- Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, 812 37, Bratislava, Slovakia
| | - Suliman Y Alomar
- King Saud University, Zoology Department, College of Science, Riyadh, 11451, Saudi Arabia
| | - Saleh H Alwasel
- King Saud University, Zoology Department, College of Science, Riyadh, 11451, Saudi Arabia
| | - Eugenie Nepovimova
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, 50003 Hradec Kralove, Czech Republic
| | - Kamil Kuca
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, 50003 Hradec Kralove, Czech Republic; Biomedical Research Center, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | | | - Marian Valko
- Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, 812 37, Bratislava, Slovakia; King Saud University, Zoology Department, College of Science, Riyadh, 11451, Saudi Arabia.
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Zinc Modulation of Neuronal Calcium Sensor Proteins: Three Modes of Interaction with Different Structural Outcomes. Biomolecules 2022; 12:biom12070956. [PMID: 35883512 PMCID: PMC9312857 DOI: 10.3390/biom12070956] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 07/01/2022] [Accepted: 07/04/2022] [Indexed: 02/06/2023] Open
Abstract
Neuronal calcium sensors (NCSs) are the family of EF-hand proteins mediating Ca2+-dependent signaling pathways in healthy neurons and neurodegenerative diseases. It was hypothesized that the calcium sensor activity of NCSs can be complemented by sensing fluctuation of intracellular zinc, which could further diversify their function. Here, using a set of biophysical techniques, we analyzed the Zn2+-binding properties of five proteins belonging to three different subgroups of the NCS family, namely, VILIP1 and neurocalcin-δ/NCLD (subgroup B), recoverin (subgroup C), as well as GCAP1 and GCAP2 (subgroup D). We demonstrate that each of these proteins is capable of coordinating Zn2+ with a different affinity, stoichiometry, and structural outcome. In the absence of calcium, recoverin and VILIP1 bind two zinc ions with submicromolar affinity, and the binding induces pronounced conformational changes and regulates the dimeric state of these proteins without significant destabilization of their structure. In the presence of calcium, recoverin binds zinc with slightly decreased affinity and moderate conformational outcome, whereas VILIP1 becomes insensitive to Zn2+. NCALD binds Zn2+ with micromolar affinity, but the binding induces dramatic destabilization and aggregation of the protein. In contrast, both GCAPs demonstrate low-affinity binding of zinc independent of calcium, remaining relatively stable even at submillimolar Zn2+ concentrations. Based on these data, and the results of structural bioinformatics analysis, NCSs can be divided into three categories: (1) physiological Ca2+/Zn2+ sensor proteins capable of binding exchangeable (signaling) zinc (recoverin and VILIP1), (2) pathological Ca2+/Zn2+ sensors responding only to aberrantly high free zinc concentrations by denaturation and aggregation (NCALD), and (3) Zn2+-resistant, Ca2+ sensor proteins (GCAP1, GCAP2). We suggest that NCS proteins may therefore govern the interconnection between Ca2+-dependent and Zn2+-dependent signaling pathways in healthy neurons and zinc cytotoxicity-related neurodegenerative diseases, such as Alzheimer’s disease and glaucoma.
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Smith CA, Ebrahimpour A, Novikova L, Farina D, Bailey AO, Russell WK, Jain A, Saltzman AB, Malovannaya A, Prasad BV, Hu L, Ghebre YT. Esomeprazole covalently interacts with the cardiovascular enzyme dimethylarginine dimethylaminohydrolase: Insights into the cardiovascular risk of proton pump inhibitors. Biochim Biophys Acta Gen Subj 2022; 1866:130149. [DOI: 10.1016/j.bbagen.2022.130149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 03/31/2022] [Accepted: 04/07/2022] [Indexed: 11/28/2022]
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Zinc Signals and Immunity. Int J Mol Sci 2017; 18:ijms18102222. [PMID: 29064429 PMCID: PMC5666901 DOI: 10.3390/ijms18102222] [Citation(s) in RCA: 156] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 10/13/2017] [Accepted: 10/19/2017] [Indexed: 01/11/2023] Open
Abstract
Zinc homeostasis is crucial for an adequate function of the immune system. Zinc deficiency as well as zinc excess result in severe disturbances in immune cell numbers and activities, which can result in increased susceptibility to infections and development of especially inflammatory diseases. This review focuses on the role of zinc in regulating intracellular signaling pathways in innate as well as adaptive immune cells. Main underlying molecular mechanisms and targets affected by altered zinc homeostasis, including kinases, caspases, phosphatases, and phosphodiesterases, will be highlighted in this article. In addition, the interplay of zinc homeostasis and the redox metabolism in affecting intracellular signaling will be emphasized. Key signaling pathways will be described in detail for the different cell types of the immune system. In this, effects of fast zinc flux, taking place within a few seconds to minutes will be distinguish from slower types of zinc signals, also designated as “zinc waves”, and late homeostatic zinc signals regarding prolonged changes in intracellular zinc.
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Petrukhin OV, Orlova TG, Nezvetsky AR, Orlov NY. Transducin-activated cGMP-specific phosphodiesterase of external segments of bovine retinal rods: The influence of magnesium ions. Biophysics (Nagoya-shi) 2016. [DOI: 10.1134/s0006350916050237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Sothilingam V, Garcia Garrido M, Jiao K, Buena-Atienza E, Sahaboglu A, Trifunović D, Balendran S, Koepfli T, Mühlfriedel R, Schön C, Biel M, Heckmann A, Beck SC, Michalakis S, Wissinger B, Seeliger MW, Paquet-Durand F. Retinitis pigmentosa: impact of different Pde6a point mutations on the disease phenotype. Hum Mol Genet 2015; 24:5486-99. [PMID: 26188004 DOI: 10.1093/hmg/ddv275] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 07/09/2015] [Indexed: 11/13/2022] Open
Abstract
Mutations in the PDE6A gene can cause rod photoreceptors degeneration and the blinding disease retinitis pigmentosa (RP). While a number of pathogenic PDE6A mutations have been described, little is known about their impact on compound heterozygous situations and potential interactions of different disease-causing alleles. Here, we used a novel mouse model for the Pde6a R562W mutation in combination with an existing line carrying the V685M mutation to generate compound heterozygous Pde6a V685M/R562W animals, exactly homologous to a case of human RP. We compared the progression of photoreceptor degeneration in these compound heterozygous mice with the homozygous V685M and R562W mutants, and additionally with the D670G line that is known for a relatively mild phenotype. We investigated PDE6A expression, cyclic guanosine mono-phosphate accumulation, calpain and caspase activity, in vivo retinal function and morphology, as well as photoreceptor cell death and survival. This analysis confirms the severity of different Pde6a mutations and indicates that compound heterozygous mutants behave like intermediates of the respective homozygous situations. Specifically, the severity of the four different Pde6a situations may be categorized by the pace of photoreceptor degeneration: V685M (fastest) > V685M/R562W > R562W > D670G (slowest). While calpain activity was strongly increased in all four mutants, caspase activity was not. This points to the execution of non-apoptotic cell death and may lead to the identification of new targets for therapeutic interventions. For individual RP patients, our study may help to predict time-courses for Pde6a-related retinal degeneration and thereby facilitate the definition of a window-of-opportunity for clinical interventions.
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Affiliation(s)
- Vithiyanjali Sothilingam
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Schleichstr.4/3, Tuebingen 72076, Germany
| | - Marina Garcia Garrido
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Schleichstr.4/3, Tuebingen 72076, Germany
| | - Kangwei Jiao
- Cell Death Mechanisms Group, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany, Second People's Hospital of Yunnan Province and Fourth Affiliated Hospital of Kunming Medical University, 176 Qingnian Road, Wuhua, Kunming, Yunnan 650021, China
| | - Elena Buena-Atienza
- Molecular Genetics Laboratory, Centre for Ophthalmology, University Clinics Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany
| | - Ayse Sahaboglu
- Cell Death Mechanisms Group, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany
| | - Dragana Trifunović
- Cell Death Mechanisms Group, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany
| | - Sukirthini Balendran
- Molecular Genetics Laboratory, Centre for Ophthalmology, University Clinics Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany
| | - Tanja Koepfli
- Molecular Genetics Laboratory, Centre for Ophthalmology, University Clinics Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany
| | - Regine Mühlfriedel
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Schleichstr.4/3, Tuebingen 72076, Germany
| | - Christian Schön
- Center for Integrated Protein Science Munich (CIPSM) at the Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich 81377, Germany and
| | - Martin Biel
- Center for Integrated Protein Science Munich (CIPSM) at the Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich 81377, Germany and
| | | | - Susanne C Beck
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Schleichstr.4/3, Tuebingen 72076, Germany
| | - Stylianos Michalakis
- Center for Integrated Protein Science Munich (CIPSM) at the Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich 81377, Germany and
| | - Bernd Wissinger
- Molecular Genetics Laboratory, Centre for Ophthalmology, University Clinics Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany
| | - Mathias W Seeliger
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Schleichstr.4/3, Tuebingen 72076, Germany
| | - François Paquet-Durand
- Cell Death Mechanisms Group, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, Roentgenweg 11, Tuebingen 72076, Germany,
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Adolfsson PI, Bloth B, Hägg S, Svensson SP. Zinc Induces a Bell-shaped Proliferative Dose-response Effect in Cultured Smooth Muscle Cells From Benign Prostatic Hyperplasia. Urology 2015; 85:704.e15-9. [DOI: 10.1016/j.urology.2014.11.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 11/05/2014] [Accepted: 11/25/2014] [Indexed: 11/28/2022]
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Ugarte M, Osborne NN. Recent advances in the understanding of the role of zinc in ocular tissues. Metallomics 2014; 6:189-200. [DOI: 10.1039/c3mt00291h] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Huang YY, Li Z, Cai YH, Feng LJ, Wu Y, Li X, Luo HB. The Molecular Basis for the Selectivity of Tadalafil toward Phosphodiesterase 5 and 6: A Modeling Study. J Chem Inf Model 2013; 53:3044-53. [DOI: 10.1021/ci400458z] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Yi-You Huang
- School of Pharmaceutical
Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Zhe Li
- School of Pharmaceutical
Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Ying-Hong Cai
- School of Pharmaceutical
Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Ling-Jun Feng
- School of Pharmaceutical
Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Yinuo Wu
- School of Pharmaceutical
Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Xingshu Li
- School of Pharmaceutical
Sciences, Sun Yat-Sen University, Guangzhou 510006, China
| | - Hai-Bin Luo
- School of Pharmaceutical
Sciences, Sun Yat-Sen University, Guangzhou 510006, China
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Ugarte M, Osborne NN, Brown LA, Bishop PN. Iron, zinc, and copper in retinal physiology and disease. Surv Ophthalmol 2013; 58:585-609. [DOI: 10.1016/j.survophthal.2012.12.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 12/09/2012] [Accepted: 12/11/2012] [Indexed: 12/26/2022]
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Shukolyukov SA. Rhodopsin, Zn2+, and retinitis pigmentosa: a Short tale requiring continuation. BIOCHEMISTRY (MOSCOW) 2013; 78:660-6. [DOI: 10.1134/s0006297913060114] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Combined ligand based pharmacophore modeling, virtual screening methods to identify critical chemical features of novel potential inhibitors for phosphodiesterase-5. J Taiwan Inst Chem Eng 2011. [DOI: 10.1016/j.jtice.2011.02.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Yamazaki A, Hayashi F, Matsuura I, Bondarenko VA. Binding of cGMP to the transducin-activated cGMP phosphodiesterase, PDE6, initiates a large conformational change involved in its deactivation. FEBS J 2011; 278:1854-72. [PMID: 21439020 DOI: 10.1111/j.1742-4658.2011.08104.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Retinal photoreceptor phosphodiesterase (PDE6), a key enzyme for phototransduction, consists of a catalytic subunit complex (Pαβ) and two inhibitory subunits (Pγs). Pαβ has two noncatalytic cGMP-binding sites. Here, using bovine PDE preparations, we show the role of these cGMP-binding sites in PDE regulation. Pαβγγ and its transducin-activated form, Pαβγ, contain two and one cGMP, respectively. Only Pαβγ shows [(3)H]cGMP binding with a K(d) ∼ 50 nM and Pγ inhibits the [(3)H]cGMP binding. Binding of cGMP to Pαβγ is suppressed during its formation, implying that cGMP binding is not involved in Pαβγγ activation. Once bound to Pαβγ, [(3)H]cGMP is not dissociated even in the presence of a 1000-fold excess of unlabeled cGMP, binding of cGMP changes the apparent Stokes' radius of Pαβγ, and the amount of [(3)H]cGMP-bound Pαβγ trapped by a filter is spontaneously increased during its incubation. These results suggest that Pαβγ slowly changes its conformation after cGMP binding, i.e. after formation of Pαβγ containing two cGMPs. Binding of Pγ greatly shortens the time to detect the increase in the filter-trapped level of [(3)H]cGMP-bound Pαβγ, but alters neither the level nor its Stokes' radius. These results suggest that Pγ accelerates the conformational change, but does not add another change. These observations are consistent with the view that Pαβγ changes its conformation during its deactivation and that the binding of cGMP and Pγ is crucial for this change. These observations also imply that Pαβγγ changes its conformation during its activation and that release of Pγ and cGMP is essential for this change.
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Affiliation(s)
- Akio Yamazaki
- Kresge Eye Institute, Wayne State University, Detroit, MI, USA
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Francis SH, Blount MA, Corbin JD. Mammalian Cyclic Nucleotide Phosphodiesterases: Molecular Mechanisms and Physiological Functions. Physiol Rev 2011; 91:651-90. [DOI: 10.1152/physrev.00030.2010] [Citation(s) in RCA: 451] [Impact Index Per Article: 34.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The superfamily of cyclic nucleotide (cN) phosphodiesterases (PDEs) is comprised of 11 families of enzymes. PDEs break down cAMP and/or cGMP and are major determinants of cellular cN levels and, consequently, the actions of cN-signaling pathways. PDEs exhibit a range of catalytic efficiencies for breakdown of cAMP and/or cGMP and are regulated by myriad processes including phosphorylation, cN binding to allosteric GAF domains, changes in expression levels, interaction with regulatory or anchoring proteins, and reversible translocation among subcellular compartments. Selective PDE inhibitors are currently in clinical use for treatment of erectile dysfunction, pulmonary hypertension, intermittent claudication, and chronic pulmonary obstructive disease; many new inhibitors are being developed for treatment of these and other maladies. Recently reported x-ray crystallographic structures have defined features that provide for specificity for cAMP or cGMP in PDE catalytic sites or their GAF domains, as well as mechanisms involved in catalysis, oligomerization, autoinhibition, and interactions with inhibitors. In addition, major advances have been made in understanding the physiological impact and the biochemical basis for selective localization and/or recruitment of specific PDE isoenzymes to particular subcellular compartments. The many recent advances in understanding PDE structures, functions, and physiological actions are discussed in this review.
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Affiliation(s)
- Sharron H. Francis
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee; and Department of Medicine-Renal Division, Emory University School of Medicine, Atlanta, Georgia
| | - Mitsi A. Blount
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee; and Department of Medicine-Renal Division, Emory University School of Medicine, Atlanta, Georgia
| | - Jackie D. Corbin
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee; and Department of Medicine-Renal Division, Emory University School of Medicine, Atlanta, Georgia
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Abstract
Network Map States Transitions Functions Protein Classes Sequence Interactions Pathways Domains & Motifs Protein Structure Orthologs Sequence Interactions Pathways Domains & Motifs Protein Structure Orthologs Blast Data.
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Abstract
Cyclic nucleotide phosphodiesterases (PDEs) are promising targets for pharmacological intervention. The presence of multiple PDE genes, diversity of the isoforms produced from each gene, selective tissue and cellular expression of the isoforms, compartmentation within cells, and an array of conformations of PDE proteins are some of the properties that challenge the development of drugs that target these enzymes. Nevertheless, many of the characteristics of PDEs are also viewed as unique opportunities to increase specificity and selectivity when designing novel compounds for certain therapeutic indications. This chapter provides a summary of the major concepts related to the design and use of PDE inhibitors. The overall structure and properties of the catalytic domain and conformations of PDEs are summarized in light of the most recent X-ray crystal structures. The distinctive properties of catalytic domains of different families as well as the technical challenges associated with probing PDE properties and their interactions with small molecules are discussed. The effect of posttranslational modifications and protein-protein interactions are additional factors to be considered when designing PDE inhibitors. PDE inhibitor interaction with other proteins needs to be taken into account and is also discussed.
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Grau T, Artemyev NO, Rosenberg T, Dollfus H, Haugen OH, Cumhur Sener E, Jurklies B, Andreasson S, Kernstock C, Larsen M, Zrenner E, Wissinger B, Kohl S. Decreased catalytic activity and altered activation properties of PDE6C mutants associated with autosomal recessive achromatopsia. Hum Mol Genet 2010; 20:719-30. [PMID: 21127010 DOI: 10.1093/hmg/ddq517] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mutations in the gene encoding the catalytic subunit of the cone photoreceptor phosphodiesterase (PDE6C) have been recently reported in patients with autosomal recessive inherited achromatopsia (ACHM) and early-onset cone photoreceptor dysfunction. Here we present the results of a comprehensive study on PDE6C mutations including the mutation spectrum, its prevalence in a large cohort of ACHM/cone dysfunction patients, the clinical phenotype and the functional characterization of mutant PDE6C proteins. Twelve affected patients from seven independent families segregating PDE6C mutations were identified in our total patient cohort of 492 independent families. Eleven different PDE6C mutations were found including two nonsense mutations, three mutations affecting transcript splicing as shown by minigene assays, one 1 bp-insertion and five missense mutations. We also performed a detailed functional characterization of six missense mutations applying the baculovirus system to express recombinant mutant and wildtype chimeric PDE6C/PDE5 proteins in Sf9 insect cells. Purified proteins were analyzed using Western blotting, phosphodiesterase (PDE) activity measurements as well as inhibition assays by zaprinast and Pγ. Four of the six PDE6C missense mutations led to baseline PDE activities and most likely represent functional null alleles. For two mutations, p.E790K and p.Y323N, we observed reduction in PDE activity of approximately 60% and 80%, respectively. We also observed differences for Pγ inhibition. The p.E790K mutant, with an IC₅₀ value of 2.7 nm is 20.7-fold more sensitive for Pγ inhibition, whereas the p.Y323N mutant with an IC₅₀ of 158 nm is 3-fold less sensitive when compared with the wildtype control.
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Affiliation(s)
- Tanja Grau
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, Centre for Ophthalmology, University Clinics Tuebingen, Roentgenweg 11, D-72076 Tuebingen, Germany
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Mechanism for the regulation of mammalian cGMP phosphodiesterase6. 2: isolation and characterization of the transducin-activated form. Mol Cell Biochem 2010; 339:235-51. [PMID: 20177739 DOI: 10.1007/s11010-010-0404-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Accepted: 01/25/2010] [Indexed: 10/19/2022]
Abstract
Rod photoreceptor cGMP phosphodiesterase (PDE6) consists of a catalytic subunit complex (Palphabeta) and two inhibitory subunits (Pgamma). In the accompanying article, using bovine photoreceptor outer segment homogenates, we show that Pgamma as a complex with the GTP-bound transducin alpha subunit (GTP-Talpha) dissociates from Palphabetagammagamma on membranes, and the Palphabetagammagamma becomes Pgamma-depleted. Here, we identify and characterize the Pgamma-depleted PDE. After incubation with or without guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS), Palphabeta complexes are extracted. When a hypotonic buffer is used, Palphabetagammagamma, Palphabetagamma, and a negligible amount of a Palphabeta complex containing Pgamma are isolated with GTPgammaS, and only Palphabetagammagamma is obtained without GTPgammaS. When an isotonic buffer containing Pdelta, a prenyl-binding protein, is used, Palphabetagammagammadelta, Palphabetagammadeltadelta, and a negligible amount of a Palphabeta complex containing Pgamma and Pdelta are isolated with GTPgammaS, and Palphabetagammagammadelta is obtained without GTPgammaS. Neither Palphabeta nor Palphabetagammagamma complexed with GTPgammaS-Talpha is found under any condition we examined. Palphabetagamma has approximately 12 times higher PDE activity and approximately 30 times higher Pgamma sensitivity than those of Palphabetagammagamma. These results indicate that the Pgamma-depleted PDE is Palphabetagamma. Isolation of Palphabetagammagammadelta and Palphabetagammadeltadelta suggests that one C-terminus of Palphabeta is involved in the Palphabetagammagamma interaction with membranes, and that Pgamma dissociation opens another C-terminus for Pdelta binding, which may lead to the expression of high PDE activity. Cone PDE behaves similarly to rod PDE in the anion exchange column chromatography. We conclude that the mechanisms for PDE activation are similar in mammalian and amphibian photoreceptors as well as in rods and cones.
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Guo LW, Ruoho AE. The retinal cGMP phosphodiesterase gamma-subunit - a chameleon. Curr Protein Pept Sci 2009; 9:611-25. [PMID: 19075750 DOI: 10.2174/138920308786733930] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Intrinsically disordered proteins (IDPs) represent an emerging class of proteins (or domains) that are characterized by a lack of ordered secondary and tertiary structure. This group of proteins has recently attracted tremendous interest primarily because of a unique feature: they can bind to different targets due to their structural plasticity, and thus fulfill diverse functions. The inhibitory gamma-subunit (PDEgamma) of retinal PDE6 is an intriguing IDP, of which unique protein properties are being uncovered. PDEgamma critically regulates the turn on as well as the turn off of visual signaling through alternate interactions with the PDE6 catalytic core, transducin, and the regulator of G protein signaling RGS9-1. The intrinsic disorder of PDEgamma does not compromise, but rather, optimizes its functionality. PDEgamma "curls up" when free in solution but "stretches out" when binding with the PDE6 catalytic core. Conformational changes of PDEgamma also likely occur in its C-terminal PDE6-binding region upon interacting with transducin during PDE6 activation. Growing evidence shows that PDEgamma is also a player in non-phototransduction pathways, suggesting additional protein targets. Thus, PDEgamma is highly likely to be adaptive in its structure and function, hence a "chameleon".
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Affiliation(s)
- Lian-Wang Guo
- Department of Pharmacology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA.
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20
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Zhang XJ, Cahill KB, Elfenbein A, Arshavsky VY, Cote RH. Direct allosteric regulation between the GAF domain and catalytic domain of photoreceptor phosphodiesterase PDE6. J Biol Chem 2008; 283:29699-705. [PMID: 18779324 DOI: 10.1074/jbc.m803948200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Photoreceptor cGMP phosphodiesterase (PDE6) is the central enzyme in the visual transduction cascade. The PDE6 catalytic subunit contains a catalytic domain and regulatory GAF domains. Unlike most GAF domain-containing cyclic nucleotide phosphodiesterases, little is known about direct allosteric communication of PDE6. In this study, we demonstrate for the first time direct, inter-domain allosteric communication between the GAF and catalytic domains in PDE6. The binding affinity of PDE6 for pharmacological inhibitors or for the C-terminal region of the inhibitory gamma subunit (Pgamma), known to directly inhibit PDE6 catalysis, was increased approximately 2-fold by ligands binding to the GAF domain. Binding of the N-terminal half of Pgamma to the GAF domains suffices to induce this allosteric effect. Allosteric communication between GAF and catalytic domains is reciprocal, in that drug binding to the catalytic domain slowed cGMP dissociation from the GAF domain. Although cGMP hydrolysis was not affected by binding of Pgamma1-60, Pgamma lacking its last seven amino acids decreased the Michaelis constant of PDE6 by 2.5-fold. Pgamma1-60 binding to the GAF domain increased vardenafil but not cGMP affinity, indicating that substrate- and inhibitor-binding sites do not totally overlap. In addition, prolonged incubation of PDE6 with vardenafil or sildenafil (but not 3-isobutyl-1-methylxanthine and zaprinast) induced a distinct conformational change in the catalytic domain without affecting the binding properties of the GAF domains. We conclude that although Pgamma-mediated regulation plays the dominant role in visual excitation, the direct, inter-domain allosteric regulation described in this study may play a feedback role in light adaptational processes during phototransduction.
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Affiliation(s)
- Xiu-Jun Zhang
- Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 03824, USA
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21
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Puzzo D, Sapienza S, Arancio O, Palmeri A. Role of phosphodiesterase 5 in synaptic plasticity and memory. Neuropsychiatr Dis Treat 2008; 4:371-87. [PMID: 18728748 PMCID: PMC2518390 DOI: 10.2147/ndt.s2447] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Phosphodiesterases (PDEs) are enzymes that break down the phosphodiesteric bond of the cyclic nucleotides, cAMP and cGMP, second messengers that regulate many biological processes. PDEs participate in the regulation of signal transduction by means of a fine regulation of cyclic nucleotides so that the response to cell stimuli is both specific and activates the correct third messengers. Several PDE inhibitors have been developed and used as therapeutic agents because they increase cyclic nucleotide levels by blocking the PDE function. In particular, sildenafil, an inhibitor of PDE5, has been mainly used in the treatment of erectile dysfunction but is now also utilized against pulmonary hypertension. This review examines the physiological role of PDE5 in synaptic plasticity and memory and the use of PDE5 inhibitors as possible therapeutic agents against disorders of the central nervous system (CNS).
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Affiliation(s)
- Daniela Puzzo
- Dept of Physiological Sciences, University of Catania Catania, Italy.
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22
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Srivani P, Srinivas E, Raghu R, Sastry GN. Molecular modeling studies of pyridopurinone derivatives—Potential phosphodiesterase 5 inhibitors. J Mol Graph Model 2007; 26:378-90. [PMID: 17307372 DOI: 10.1016/j.jmgm.2007.01.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2006] [Revised: 01/11/2007] [Accepted: 01/12/2007] [Indexed: 12/01/2022]
Abstract
Two- and three-dimensional quantitative structure-activity relationship (QSAR) and docking studies were carried out on a series of pyridopurinones, to model their phosphodiesterase 5 (PDE5) inhibitory activities. 2D-QSAR was performed using the heuristic and best multi linear regression (BMLR) methods in CODESSA (comprehensive descriptors for structural and statistical analysis), which had given linear models between the inhibitory activity and five descriptors of PDE5 inhibitors, with r(2)=0.987, 0.987, q(2)=0.970, 0.970, F=166.71, 166.71 and s(2)=0.0004, 0.0176, respectively. Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) have provided statistically significant models with q(2) values of 0.784, 0.742 and r(2) values of 0.975, 0.972 respectively. The predictive ability of the models was validated using a set of 6 compounds that were not included in the training set and the predictive r(2) obtained for the test set was 0.901 and 0.888 respectively. Docking studies were employed to determine the probable binding conformation of these analogues in the PDE5 active site using the programs GOLD and AutoDock whose results were found complementary with 3D-QSAR maps. Since the potency towards PDE5 and the selectivity over PDE6 is important for the successful development of new PDE5 inhibitors, a PDE6 homology model was built using Insight II and Modeller with Phi-Psi BLAST alignment. The molecules were docked in the active site of PDE6 and analyzed the probable reasons for selectivity of these molecules towards PDE5 over PDE6. Mapping the 3D-QSAR models to the active site of PDE5 provides a new insight into the protein-inhibitor interactions and helpful in designing potent and selective PDE5 inhibitors for the treatment of erectile dysfunction.
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Affiliation(s)
- P Srivani
- Molecular Modeling Group, Organic Chemical Sciences, Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500007, India
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23
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Cote RH. Characteristics of photoreceptor PDE (PDE6): similarities and differences to PDE5. Int J Impot Res 2004; 16 Suppl 1:S28-33. [PMID: 15224133 DOI: 10.1038/sj.ijir.3901212] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Phosphodiesterase 6 (PDE6) is highly concentrated in the retina. It is most abundant in the internal membranes of retinal photoreceptors, where it reduces cytoplasmic levels of cyclic guanosine monophosphate (cGMP) in rod and cone outer segments in response to light. The rod PDE6 holoenzyme comprises alpha and beta catalytic subunits and two identical inhibitory gamma subunits. Each catalytic subunit contains three distinct globular domains corresponding to the catalytic domain and two GAF domains (responsible for allosteric cGMP binding). The PDE6 catalytic subunits resemble PDE5 in amino-acid sequence as well as in three-dimensional structure of the catalytic dimer; preference for cGMP over cyclic adenosine monophosphate (cAMP) as a substrate; and the ability to bind cGMP at the regulatory GAF domains. Most PDE5 inhibitors inhibit PDE6 with similar potency, and electroretinogram studies show modest effects of PDE5 inhibitors on visual function-an observation potentially important in designing PDE5-specific therapeutic agents.
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Affiliation(s)
- R H Cote
- 1Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, NH 03824-2617, USA.
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24
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He F, Mao M, Wensel TG. Enhancement of phototransduction g protein-effector interactions by phosphoinositides. J Biol Chem 2003; 279:8986-90. [PMID: 14699118 DOI: 10.1074/jbc.m311488200] [Citation(s) in RCA: 25] [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
Light responses in photoreceptor cells are mediated by the action of the G protein transducin (G(t)) on the effector enzyme cGMP phosphodiesterase (PDE6) at the surface of disk membranes. The enzymatic components needed for phosphoinositide-based signaling are known to be present in rod cells, but it has remained uncertain what role phosphoinositides play in vertebrate phototransduction. Reconstitution of PDE6 and activated G(alphat), on the surface of large unilamellar vesicles containing d-myo-phosphatidylinositol-4,5-bisphosphate (PI(4,5)P(2)), stimulated PDE activity nearly 4-fold above the level observed with membranes containing no phosphoinositides, whereas G protein-independent activation by trypsin was unaffected by the presence of phosphoinositides. PDE activity was similarly stimulated by d-myo-phosphatidylinositol-3,4-bisphosphate and d-myo-phosphatidylinositol-4-phosphate (PI(4)P), but much less by d-myo-phosphatidylinositol-5-phosphate (PI(5)P) or d-myo-phosphatidylinositol-3,5-bisphosphate. Incubation of rod outer segment membranes with phosphoinositide-specific phospholipase C decreased G protein-stimulated activation of endogenous PDE6, but not trypsin-stimulated PDE activity. Binding experiments using phosphoinositide-containing vesicles revealed patterns of PDE6 binding and PDE6-enhanced G(alphat)-GTPgammaS binding, consistent with the activation profile PI(4,5)P(2) > PI(4)P > PI(5)P approximately control vesicles. These results suggest that enhancement of effector-G protein interactions represents a possible mechanism for modulation of phototransduction gain by changes in phosphoinositide levels, perhaps occurring in response to longterm changes in illumination or other environmental cues.
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Affiliation(s)
- Feng He
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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25
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del Valle LJ, Ramon E, Cañavate X, Dias P, Garriga P. Zinc-induced decrease of the thermal stability and regeneration of rhodopsin. J Biol Chem 2003; 278:4719-24. [PMID: 12482872 DOI: 10.1074/jbc.m210760200] [Citation(s) in RCA: 28] [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
Zinc is present at high concentrations in the photoreceptor cells of the retina where it has been proposed to play a role in the visual phototransduction process. In order to obtain more information about this role, the study of the effect of zinc on several properties of the visual photoreceptor rhodopsin has been investigated. A specific effect of Zn(2+) on the thermal stability of rhodopsin, obtained from bovine retinas and solubilized in dodecyl maltoside detergent, in the dark is reported. The thermal stability of rhodopsin in its ground state (dark state) is clearly reduced with increasing Zn(2+) concentrations (0-50 microm Zn(2+)). The thermal bleaching process is accelerated in the presence of Zn(2+) with k rate constants, at 55 degrees C, of 0.028 +/- 0.002 min(-1) (0 microm Zn(2+)) and 0.056 +/- 0.003 min(-1) (50 microm Zn(2+)), corresponding to t(12) values of 24.4 +/- 1.6 min and 11.8 +/- 0.1 min, respectively. Thermodynamic parameters derived from Arrhenius plots show a significant E(a) increase at 50 microm Zn(2+) for the process, with deltaG++ decrease and increase in deltaH++ and deltaS++ possibly reflecting conformational rearrangements and reordering of water molecules. The stability of the metarhodopsin II intermediate is also decreased and changes in the metarhodopsin II decay pathway are also detected. The extent of rhodopsin regeneration in vitro is also reduced by zinc. These effects, specific for zinc, are also seen for rhodopsin in native disc membranes, and may be relevant to the suggested role of Zn(2+) in normal and pathological retinal function.
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Affiliation(s)
- Luis J del Valle
- Centre de Biotecnologia Molecular (CEBIM), Universitat Politècnica de Catalunya, Colom 1, 08222 Terrassa, Catalonia, Spain
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26
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Matthews HR, Fain GL. Time course and magnitude of the calcium release induced by bright light in salamander rods. J Physiol 2002; 542:829-41. [PMID: 12154182 PMCID: PMC2290437 DOI: 10.1113/jphysiol.2001.013218] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Changes in fluorescence were measured with an argon ion laser from the outer segments of isolated salamander rods containing the Ca(2+)-sensitive fluorescent dye fluo-5F. When the outer segments were exposed to a 0Ca(2+)/0Na(+) solution designed to minimise surface membrane Ca(2+) fluxes, exposure to intense light from the laser evoked a slow increase in fluorescence, reflecting a light-induced rise in outer segment [Ca(2+)](i). The time course of this slow fluorescence rise could be fitted with the sum of two asymptotic exponential functions of approximately equal amplitude, having time constants of approximately 200 ms and 5.7 s. When rods were exposed to saturating background light to reduce outer segment [Ca(2+)](i) before laser illumination, the relative amplitude of the two exponentials was altered so as to reduce the contribution from the one with the shorter time constant. Examination of the initial time course of fluorescence when recording at high temporal resolution revealed a further rapid rise with a time constant of 1-2 ms, which could be observed even from rods in Ringer solution. This initial rapid rise could be abolished by pre-exposing the rod to bleaching illumination, whether the bleach was given in Ringer solution or in 0Ca(2+)/0Na(+) solution. It would therefore appear that the rapid rise in fluorescence is generated in some way by the bleaching of the photopigment. Unlike the slower components of fluorescence increase, the rapid initial rise was virtually unaffected in waveform or amplitude when rods were pre-exposed in Ringer solution to light which was bright enough to suppress completely the circulating current but which bleached a negligible fraction of the photopigment. Furthermore, pre-incubation with the AM ester of the Ca(2+) chelator BAPTA, although completely abolishing the slower components of fluorescence increase, had virtually no effect on the rapid rise. These results indicate that the rapid component, though triggered by rhodopsin bleaching, does not reflect an increase in outer segment [Ca(2+)](i). Neither the rapid nor the slower components of fluorescence increase were affected by exposure of the outer segment to 10 microM of the membrane-permeant compound N,N,N',N'-tetrakis(2-pyridyl-methyl)ethylenediamine (TPEN), which chelates heavy metals such as Zn(2+), or 100 microM 2-aminoethoxydiphenylborate (2-APB), a membrane-permeant blocker of IP(3) receptors. These results appear to exclude a role for changes in heavy metal concentration or Ca(2+) release via IP(3) receptors in the light-induced increases in dye fluorescence. Estimates of absolute Ca(2+) concentration and of rod buffering capacity suggest that the slower components of fluorescence increase represent the release of around 10-50 micromoles Ca(2+) per litre cytoplasmic volume from bound or sequestered stores after bleaching.
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Affiliation(s)
- Hugh R Matthews
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
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27
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Kajimura N, Yamazaki M, Morikawa K, Yamazaki A, Mayanagi K. Three-dimensional structure of non-activated cGMP phosphodiesterase 6 and comparison of its image with those of activated forms. J Struct Biol 2002; 139:27-38. [PMID: 12372317 DOI: 10.1016/s1047-8477(02)00502-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Cyclic GMP phosphodiesterase (PDE6) in rod photoreceptors, a key enzyme in vertebrate phototransduction, consists of two homologous catalytic subunits (Palpha and Pbeta) and two identical regulatory subunits (Pgammas). Pgamma regulates the PDE activity through its direct interaction with transducin. Here, using electron microscopy and image analysis of single particles, we show the three-dimensional organization of the basic form of bovine PDE, Palphabetagammagamma, and compare its average image with those of Pgamma-released PDE. The structure of Palphabetagammagamma appears to be a flattened bell-shape, with dimensions of 150 x 108 x 60A, and with a handle-like protrusion attached to the top of the structure. Except for the protrusion, the organization consists of two homologous structures arranged side by side, with each structure having three distinct regions, showing pseudo twofold symmetry. These characteristics are consistent with a model in which the overall structure of Palphabetagammagamma is determined by hetero-dimerization of Palpha and Pbeta, with each subunit consisting of one catalytic and two GAF regions. A comparison of the average image of Palphabetagammagamma with those of Pgamma-released PDE suggests that Pgamma release does not affect the overall structure of Palphabeta, and that the Palphabeta C-terminus, but not Pgamma, is a determinant for the Palphabeta orientation on carbon-coated grids. These observations suggest that the basic structure of PDE does not change during its regulation, which implies that Palphabeta is regulated by its regional interaction with Pgamma.
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Affiliation(s)
- Naoko Kajimura
- Biomolecular Engineering Research Institute, 6-2-3, Furuedai, Suita, Osaka 565-0874, Japan
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28
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Richter W, Hermsdorf T, Kronbach T, Dettmer D. Refolding and purification of recombinant human PDE7A expressed in Escherichia coli as inclusion bodies. Protein Expr Purif 2002; 25:138-48. [PMID: 12071709 DOI: 10.1006/prep.2002.1620] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have investigated the refolding and purification of the catalytic domain of human 3',5'-cyclic nucleotide phosphodiesterase 7A1 (PDE7A1) expressed in Escherichia coli. A cDNA encoding an N-terminal-truncated PDE7A1(147-482-His) was amplified by RT-PCR from human peripheral blood cells and inserted into the vector pET21-C for bacterial expression of the enzyme fused to a C-terminal His-tag. The PDE was found to be expressed in the form of inclusion bodies which could be refolded to an active enzyme in buffer containing high concentrations of arginine hydrochloride, ethylene glycol, and magnesium chloride at pH 8.5. The PDE7A1(147-482-His) construct could be purified after dialysis and concentration steps by either Zn2+-IDA-Sepharose chromatography or ResourceQ ion-exchange chromatography to homogeneity. In comparison to the metal-chelate column, the ResourceQ purification resulted in a distinctly better yield and enrichment of the protein. Both the Vmax (0.46 micromol. min(-1). mg(-1) ) and the K(m) (0.1 microM) of the purified enzyme were found to be comparable with published data for native or recombinant catalytically active expressed PDE7A1. Using SDS/PAGE, a molecular mass of 39 kDa was determined (theoretical value 38.783 kDa). As known from several other mammalian PDEs, size-exclusion chromatography using refolded PDE7A1(147-482-His) indicated the formation of dimers. The purified enzyme was soluble at concentrations up to 100 microg/ml. A further increase of protein concentration resulted, however, in precipitation of the enzyme.
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MESH Headings
- 3',5'-Cyclic-AMP Phosphodiesterases/chemistry
- 3',5'-Cyclic-AMP Phosphodiesterases/isolation & purification
- Alternative Splicing
- Blotting, Western
- Catalytic Domain
- Chromatography, Ion Exchange
- Cloning, Molecular
- Cyclic Nucleotide Phosphodiesterases, Type 7
- DNA, Complementary/metabolism
- Dose-Response Relationship, Drug
- Electrophoresis, Polyacrylamide Gel
- Escherichia coli/metabolism
- Heparin/pharmacology
- Humans
- Hydrogen-Ion Concentration
- Inclusion Bodies/metabolism
- Ions
- Isoenzymes/chemistry
- Isoenzymes/isolation & purification
- Kinetics
- Leukocytes/metabolism
- Models, Genetic
- Protein Binding
- Protein Folding
- Protein Renaturation
- Protein Structure, Tertiary
- Recombinant Proteins/chemistry
- Recombinant Proteins/isolation & purification
- Reducing Agents/pharmacology
- Sepharose/pharmacology
- Time Factors
- Up-Regulation
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Affiliation(s)
- Wito Richter
- Institute of Biochemistry, Medical Faculty, Institute of Biochemistry, University of Leipzig, Liebigstrasse 16, Leipzig, Germany
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29
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Kramer RH, Molokanova E. Modulation of cyclic-nucleotide-gated channels and regulation of vertebrate phototransduction. J Exp Biol 2001; 204:2921-31. [PMID: 11551982 DOI: 10.1242/jeb.204.17.2921] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Cyclic-nucleotide-gated (CNG) channels are crucial for sensory transduction in the photoreceptors (rods and cones) of the vertebrate retina. Light triggers a decrease in the cytoplasmic concentration of cyclic GMP in the outer segments of these cells, leading to closure of CNG channels and hyperpolarization of the membrane potential. Hence, CNG channels translate a chemical change in cyclic nucleotide concentration into an electrical signal that can spread through the photoreceptor cell and be transmitted to the rest of the visual system. The sensitivity of phototransduction can be altered by exposing the cells to light, through adaptation processes intrinsic to photoreceptors. Intracellular Ca2+ is a major signal in light adaptation and, in conjunction with Ca2+-binding proteins, one of its targets for modulation is the CNG channel itself. However, other intracellular signals may be involved in the fine-tuning of light sensitivity in response to cues internal to organisms. Several intracellular signals are candidates for mediating changes in cyclic GMP sensitivity including transition metals, such as Ni2+ and Zn2+, and lipid metabolites, such as diacylglycerol. Moreover, CNG channels are associated with protein kinases and phosphatases that catalyze changes in phosphorylation state and allosterically modulate channel activity. Recent studies suggest that the effects of circadian rhythms and retinal transmitters on CNG channels may be mediated by such changes in phosphorylation. The goal of this paper is to review the molecular mechanisms underlying modulation of CNG channels and to relate these forms of modulation to the regulation of light sensitivity.
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Affiliation(s)
- R H Kramer
- Department of Molecular and Cell Biology, University of California, Berkeley, 94720, USA.
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30
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Granovsky AE, Artemyev NO. Partial reconstitution of photoreceptor cGMP phosphodiesterase characteristics in cGMP phosphodiesterase-5. J Biol Chem 2001; 276:21698-703. [PMID: 11285263 DOI: 10.1074/jbc.m100626200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Photoreceptor cGMP phosphodiesterases (PDE6) are uniquely qualified to serve as effector enzymes in the vertebrate visual transduction cascade. In the dark-adapted photoreceptors, the activity of PDE6 is blocked via tight association with the inhibitory gamma-subunits (Pgamma). The Pgamma block is removed in the light-activated PDE6 by the visual G protein, transducin. Transducin-activated PDE6 exhibits an exceptionally high catalytic rate of cGMP hydrolysis ensuring high signal amplification. To identify the structural determinants for the inhibitory interaction with Pgamma and the remarkable cGMP hydrolytic ability, we sought to reproduce the PDE6 characteristics by mutagenesis of PDE5, a related cyclic GMP-specific, cGMP-binding PDE. PDE5 is insensitive to Pgamma and has a more than 100-fold lower k(cat) for cGMP hydrolysis. Our mutational analysis of chimeric PDE5/PDE6alpha' enzymes revealed that the inhibitory interaction of cone PDE6 catalytic subunits (PDE6alpha') with Pgamma is mediated primarily by three hydrophobic residues at the entry to the catalytic pocket, Met(758), Phe(777), and Phe(781). The maximal catalytic rate of PDE5 was enhanced by at least 10-fold with substitutions of PDE6alpha'-specific glycine residues for the corresponding PDE5 alanine residues, Ala(608) and Ala(612). The Gly residues are adjacent to the highly conserved metal binding motif His-Asn-X-X-His, which is essential for cGMP hydrolysis. Our results suggest that the unique Gly residues allow the PDE6 metal binding site to adopt a more favorable conformation for cGMP hydrolysis.
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MESH Headings
- 3',5'-Cyclic-GMP Phosphodiesterases/chemistry
- 3',5'-Cyclic-GMP Phosphodiesterases/genetics
- 3',5'-Cyclic-GMP Phosphodiesterases/metabolism
- Alanine
- Amino Acid Sequence
- Amino Acid Substitution
- Animals
- Binding Sites
- Catalytic Domain
- Cloning, Molecular
- Computer Simulation
- Conserved Sequence
- Cyclic Nucleotide Phosphodiesterases, Type 5
- Cyclic Nucleotide Phosphodiesterases, Type 6
- Kinetics
- Models, Molecular
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Phosphoric Diester Hydrolases/chemistry
- Phosphoric Diester Hydrolases/genetics
- Phosphoric Diester Hydrolases/metabolism
- Photoreceptor Cells, Vertebrate/enzymology
- Protein Conformation
- Protein Structure, Secondary
- Protein Subunits
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/metabolism
- Software
- Vertebrates
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Affiliation(s)
- A E Granovsky
- Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA
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31
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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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32
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Granovsky AE, Artemyev NO. Identification of the gamma subunit-interacting residues on photoreceptor cGMP phosphodiesterase, PDE6alpha '. J Biol Chem 2000; 275:41258-62. [PMID: 11024033 DOI: 10.1074/jbc.m008094200] [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
Photoreceptor cGMP phosphodiesterase (PDE6) is the effector enzyme in the G protein-mediated visual transduction cascade. In the dark, the activity of PDE6 is shut off by the inhibitory gamma subunit (Pgamma). Chimeric proteins between cone PDE6alpha' and cGMP-binding and cGMP-specific PDE (PDE5) have been constructed and expressed in Sf9 cells to study the mechanism of inhibition of PDE6 catalytic activity by Pgamma. Substitution of the segment PDE5-(773-820) by the corresponding PDE6alpha'-(737-784) sequence in the wild-type PDE5 or in a PDE5/PDE6alpha' chimera containing the catalytic domain of PDE5 results in chimeric enzymes capable of inhibitory interaction with Pgamma. The catalytic properties of the chimeric PDEs remained similar to those of PDE5. Ala-scanning mutational analysis of the Pgamma-binding region, PDE6alpha'-(750-760), revealed PDE6alpha' residues essential for the interaction. The M758A mutation markedly impaired and the Q752A mutation moderately impaired the inhibition of chimeric PDE by Pgamma. The analysis of the catalytic properties of mutant PDEs and a model of the PDE6 catalytic domain suggest that residues Met(758) and Gln(752) directly bind Pgamma. A model of the PDE6 catalytic site shows that PDE6alpha'-(750-760) forms a loop at the entrance to the cGMP-binding pocket. Binding of Pgamma to Met(758) would effectively block access of cGMP to the catalytic cavity, providing a structural basis for the mechanism of PDE6 inhibition.
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Affiliation(s)
- A E Granovsky
- Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA
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