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Specker E, Wesolowski R, Schütz A, Matthes S, Mallow K, Wasinska-Kalwa M, Winkler L, Oder A, Alenina N, Pleimes D, von Kries JP, Heinemann U, Bader M, Nazaré M. Structure-Based Design of Xanthine-Imidazopyridines and -Imidazothiazoles as Highly Potent and In Vivo Efficacious Tryptophan Hydroxylase Inhibitors. J Med Chem 2023; 66:14866-14896. [PMID: 37905925 DOI: 10.1021/acs.jmedchem.3c01454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Tryptophan hydroxylases catalyze the first and rate-limiting step in the biosynthesis of serotonin, a well-known neurotransmitter that plays an important role in multiple physiological functions. A reduction of serotonin levels, especially in the brain, can cause dysregulation leading to depression or insomnia. In contrast, overproduction of peripheral serotonin is associated with symptoms like carcinoid syndrome and pulmonary arterial hypertension. Recently, we developed a class of TPH inhibitors based on xanthine-benzimidazoles, characterized by a tripartite-binding mode spanning the binding sites of the cosubstrate pterin and the substrate tryptophan and by chelation of the catalytic iron ion. Herein, we describe the structure-based development of a second generation of xanthine-imidiazopyridines and -imidazothiazoles designed to inhibit TPH1 in the periphery while preventing the interaction with TPH2 in the brain. Lead compound 32 (TPT-004) shows superior pharmacokinetic and pharmacodynamic properties as well as efficacy in preclinical models of peripheral serotonin attenuation and colorectal tumor growth.
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Affiliation(s)
- Edgar Specker
- Chemical Biology Platform, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
- Trypto Therapeutics GmbH, Robert-Rössle Straße 10, 13125 Berlin, Germany
| | - Radoslaw Wesolowski
- Trypto Therapeutics GmbH, Robert-Rössle Straße 10, 13125 Berlin, Germany
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
| | - Anja Schütz
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
| | - Susann Matthes
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
| | - Keven Mallow
- Chemical Biology Platform, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
| | - Malgorzata Wasinska-Kalwa
- Chemical Biology Platform, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
| | - Lars Winkler
- Experimental Pharmacology and Oncology GmbH, Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
| | - Andreas Oder
- Chemical Biology Platform, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
| | - Natalia Alenina
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Berlin, Potsdamer Straße 58, 10785 Berlin, Germany
| | - Dirk Pleimes
- Trypto Therapeutics GmbH, Robert-Rössle Straße 10, 13125 Berlin, Germany
| | - Jens Peter von Kries
- Chemical Biology Platform, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
| | - Udo Heinemann
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
| | - Michael Bader
- Trypto Therapeutics GmbH, Robert-Rössle Straße 10, 13125 Berlin, Germany
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Berlin, Potsdamer Straße 58, 10785 Berlin, Germany
- Charité─Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
- University of Lübeck, Institute for Biology, Ratzeburger Allee 160, 23562 Lübeck, Germany
| | - Marc Nazaré
- Chemical Biology Platform, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Straße 10, 13125 Berlin-Buch, Germany
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Mammoli A, Riccio A, Bianconi E, Coletti A, Camaioni E, Macchiarulo A. One Key and Multiple Locks: Substrate Binding in Structures of Tryptophan Dioxygenases and Hydroxylases. ChemMedChem 2021; 16:2732-2743. [PMID: 34137184 PMCID: PMC8518741 DOI: 10.1002/cmdc.202100312] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 06/14/2021] [Indexed: 12/18/2022]
Abstract
Since its discovery at the beginning of the past century, the essential nutrient l-Tryptophan (l-Trp) and its catabolic pathways have acquired an increasing interest in an ever wider scientific community for their pivotal roles in underlying many important physiological functions and associated pathological conditions. As a consequence, enzymes catalyzing rate limiting steps along l-Trp catabolic pathways - including IDO1, TDO, TPH1 and TPH2 - have turned to be interesting drug targets for the design and development of novel therapeutic agents for different disorders such as carcinoid syndrome, cancer and autoimmune diseases. This article provides a fresh comparative overview on the most recent advancements that crystallographic studies, biophysical and computational works have brought on structural aspects and molecular recognition patterns of these enzymes toward l-Trp. Finally, a conformational analysis of l-Trp is also discussed as part of the molecular recognition process governing the binding of a substrate to its cognate enzymes.
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Affiliation(s)
- Andrea Mammoli
- Department of Pharmaceutical SciencesUniversity of PerugiaVia del Liceo N. 106123PerugiaItaly
| | - Alessandra Riccio
- Department of Pharmaceutical SciencesUniversity of PerugiaVia del Liceo N. 106123PerugiaItaly
| | - Elisa Bianconi
- Department of Pharmaceutical SciencesUniversity of PerugiaVia del Liceo N. 106123PerugiaItaly
| | - Alice Coletti
- Department of Medicine and SurgeryUniversity of PerugiaP. le Gambuli06132PerugiaItaly
| | - Emidio Camaioni
- Department of Pharmaceutical SciencesUniversity of PerugiaVia del Liceo N. 106123PerugiaItaly
| | - Antonio Macchiarulo
- Department of Pharmaceutical SciencesUniversity of PerugiaVia del Liceo N. 106123PerugiaItaly
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Moroz LL, Romanova DY, Kohn AB. Neural versus alternative integrative systems: molecular insights into origins of neurotransmitters. Philos Trans R Soc Lond B Biol Sci 2021; 376:20190762. [PMID: 33550949 PMCID: PMC7935107 DOI: 10.1098/rstb.2019.0762] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2020] [Indexed: 12/18/2022] Open
Abstract
Transmitter signalling is the universal chemical language of any nervous system, but little is known about its early evolution. Here, we summarize data about the distribution and functions of neurotransmitter systems in basal metazoans as well as outline hypotheses of their origins. We explore the scenario that neurons arose from genetically different populations of secretory cells capable of volume chemical transmission and integration of behaviours without canonical synapses. The closest representation of this primordial organization is currently found in Placozoa, disk-like animals with the simplest known cell composition but complex behaviours. We propose that injury-related signalling was the evolutionary predecessor for integrative functions of early transmitters such as nitric oxide, ATP, protons, glutamate and small peptides. By contrast, acetylcholine, dopamine, noradrenaline, octopamine, serotonin and histamine were recruited as canonical neurotransmitters relatively later in animal evolution, only in bilaterians. Ligand-gated ion channels often preceded the establishment of novel neurotransmitter systems. Moreover, lineage-specific diversification of neurotransmitter receptors occurred in parallel within Cnidaria and several bilaterian lineages, including acoels. In summary, ancestral diversification of secretory signal molecules provides unique chemical microenvironments for behaviour-driven innovations that pave the way to complex brain functions and elementary cognition. This article is part of the theme issue 'Basal cognition: multicellularity, neurons and the cognitive lens'.
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Affiliation(s)
- Leonid L. Moroz
- Department of Neuroscience, McKnight Brain Institute and Whitney laboratory, University of Florida, 9505 Ocean shore Blvd, St Augustine, FL 32080, USA
| | - Daria Y. Romanova
- Laboratory of Cellular Neurobiology of Learning, Institute of Higher Nervous Activity and Neurophysiology of RAS, 5A Butlerova Street, Moscow 117485, Russia
| | - Andrea B. Kohn
- Department of Neuroscience, McKnight Brain Institute and Whitney laboratory, University of Florida, 9505 Ocean shore Blvd, St Augustine, FL 32080, USA
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Huang W, Zhu L, Cao G, Xie P, Song Y, Huang J, Chen X, Cai Z. Integrated Proteomics and Metabolomics Assessment Indicated Metabolic Alterations in Hypothalamus of Mice Exposed to Triclosan. Chem Res Toxicol 2021; 34:1319-1328. [PMID: 33611912 DOI: 10.1021/acs.chemrestox.0c00514] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Triclosan (TCS) is a ubiquitous antimicrobial used in many daily consumer products. It has been reported to induce endocrine disrupting effects at low doses in mammals, disturbing sex hormone function and thyroid function. The hypothalamus plays a crucial role in the maintenance of neuroendocrine function and energy homeostasis. We speculated that the adverse effects of TCS might be related to the disturbance of metabolic processes in hypothalamus. The present study aimed at investigating the effects of TCS exposure on the protein and metabolite profiles in hypothalamus of mice. Male C57BL/6 mice were orally exposed to TCS at the dosage of 10 mg/kg/d for 13 weeks. The hypothalamus was isolated and processed for mass spectrometry (MS)-based proteomics and metabolomics analyses. The results showed that a 10.6% decrease (P = 0.066) in body weight gain was observed in the TCS exposure group compared with vehicle control group. Differential analysis defined 52 proteins and 57 metabolites that delineated TCS exposed mice from vehicle controls. Among the differential features, multiple proteins and metabolites were found to play vital roles in neuronal signaling and function. Bioinformatics analysis revealed that these differentially expressed proteins and metabolites were involved in four major biological processes, including glucose metabolism, purine metabolism, neurotransmitter release, and neural plasticity, suggesting the disturbance of homeostasis in energy metabolism, mitochondria function, neurotransmitter system, and neuronal function. Our results may provide insights into the neurotoxicity of TCS and extend our understanding of the biological effects induced by TCS exposure.
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Affiliation(s)
- Wei Huang
- State Key Laboratory of Environmental and Biological Analysis, Hong Kong Baptist University, Hong Kong SAR, China.,School of Environment, Jinan University, Guangzhou 510632, China
| | - Lin Zhu
- State Key Laboratory of Environmental and Biological Analysis, Hong Kong Baptist University, Hong Kong SAR, China
| | - Guodong Cao
- State Key Laboratory of Environmental and Biological Analysis, Hong Kong Baptist University, Hong Kong SAR, China
| | - Peisi Xie
- State Key Laboratory of Environmental and Biological Analysis, Hong Kong Baptist University, Hong Kong SAR, China
| | - Yuanyuan Song
- State Key Laboratory of Environmental and Biological Analysis, Hong Kong Baptist University, Hong Kong SAR, China
| | - Jialing Huang
- School of Environment, Jinan University, Guangzhou 510632, China
| | - Xiangfeng Chen
- Shandong Analysis and Test Center, Qilu University of Technology, Jinan, Shandong, China
| | - Zongwei Cai
- State Key Laboratory of Environmental and Biological Analysis, Hong Kong Baptist University, Hong Kong SAR, China
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Tidemand KD, Peters GH, Harris P, Stensgaard E, Christensen HEM. Isoform-Specific Substrate Inhibition Mechanism of Human Tryptophan Hydroxylase. Biochemistry 2017; 56:6155-6164. [PMID: 29035515 DOI: 10.1021/acs.biochem.7b00763] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Tryptophan hydroxylase (TPH) catalyzes the initial and rate-limiting step in the biosynthesis of serotonin, which is associated with a variety of disorders such as depression and irritable bowel syndrome. TPH exists in two isoforms: TPH1 and TPH2. TPH1 catalyzes the initial step in the synthesis of serotonin in the peripheral tissues, while TPH2 catalyzes this step in the brain. In this study, the steady-state kinetic mechanism for the catalytic domain of human TPH1 has been determined. Varying substrate tryptophan (Trp) and tetrahydrobiopterin (BH4) results in a hybrid Ping Pong-ordered mechanism in which the reaction can either occur through a Ping Pong or a sequential mechanism depending on the concentration of tryptophan. The catalytic domain of TPH1 shares a sequence identity of 81% with TPH2. Despite the high sequence identity, differences in the kinetic parameters of the isoforms have been identified; i.e., only TPH1 displays substrate tryptophan inhibition. This study demonstrates that the difference can be traced to an active site loop which displays different properties in the TPH isoforms. Steady-state kinetic results of the isoforms, and variants with point mutations in a loop lining the active site, show that the kinetic parameters of only TPH1 are significantly changed upon mutations. Mutations in the active site loop of TPH1 result in an increase in the substrate inhibition constant, Ki, and therefore turnover rate. Molecular dynamics simulations reveal that this substrate inhibition mechanism occurs through a closure of the cosubstrate, BH4, binding pocket, which is induced by Trp binding.
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Affiliation(s)
- Kasper D Tidemand
- Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
| | - Günther H Peters
- Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
| | - Pernille Harris
- Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
| | - Eva Stensgaard
- Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
| | - Hans E M Christensen
- Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
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Tidemand KD, Christensen HEM, Hoeck N, Harris P, Boesen J, Peters GH. Stabilization of tryptophan hydroxylase 2 by l-phenylalanine-induced dimerization. FEBS Open Bio 2016; 6:987-999. [PMID: 27761358 PMCID: PMC5055035 DOI: 10.1002/2211-5463.12100] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 06/20/2016] [Accepted: 06/29/2016] [Indexed: 12/12/2022] Open
Abstract
Tryptophan hydroxylase 2 (TPH2) catalyses the initial and rate‐limiting step in the biosynthesis of serotonin, which is associated with a variety of disorders such as depression, obsessive compulsive disorder, and schizophrenia. Full‐length TPH2 is poorly characterized due to low purification quantities caused by its inherent instability. Three truncated variants of human TPH2 (rchTPH2; regulatory and catalytic domain, NΔ47‐rchTPH2; truncation of 47 residues in the N terminus of rchTPH2, and chTPH2; catalytic domain) were expressed, purified, and examined for changes in transition temperature, inactivation rate, and oligomeric state. chTPH2 displayed 14‐ and 11‐fold higher half‐lives compared to rchTPH2 and NΔ47‐rchTPH2, respectively. Differential scanning calorimetry experiments demonstrated that this is caused by premature unfolding of the less stable regulatory domain. By differential scanning fluorimetry, the unfolding transitions of rchTPH2 and NΔ47‐rchTPH2 are found to shift from polyphasic to apparent two‐state by the addition of l‐Trp or l‐Phe. Analytical gel filtration revealed that rchTPH2 and NΔ47‐rchTPH2 reside in a monomer–dimer equilibrium which is significantly shifted toward dimer in the presence of l‐Phe. The dimerizing effect induced by l‐Phe is accompanied by a stabilizing effect, which resulted in a threefold increase in half‐lives of rchTPH2 and NΔ47‐rchTPH2. Addition of l‐Phe to the purification buffer significantly increases the purification yields, which will facilitate characterization of hTPH2.
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Affiliation(s)
- Kasper D Tidemand
- Department of Chemistry Technical University of Denmark Kongens Lyngby Denmark
| | | | - Niclas Hoeck
- Department of Chemistry Technical University of Denmark Kongens Lyngby Denmark
| | - Pernille Harris
- Department of Chemistry Technical University of Denmark Kongens Lyngby Denmark
| | - Jane Boesen
- Department of Chemistry Technical University of Denmark Kongens Lyngby Denmark
| | - Günther H Peters
- Department of Chemistry Technical University of Denmark Kongens Lyngby Denmark
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Rajathei DM, Preethi J, Singh HK, Rajan KE. Molecular docking of bacosides with tryptophan hydroxylase: a model to understand the bacosides mechanism. NATURAL PRODUCTS AND BIOPROSPECTING 2014; 4:251-255. [PMID: 25089244 PMCID: PMC4111882 DOI: 10.1007/s13659-014-0031-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 06/30/2014] [Indexed: 06/03/2023]
Abstract
Tryptophan hydroxylase (TPH) catalyses l-tryptophan into 5-hydroxy-l-tryptophan, which is the first and rate-limiting step of serotonin (5-HT) biosynthesis. Earlier, we found that TPH2 up-regulated in the hippocampus of postnatal rats after the oral treatment of Bacopa monniera leaf extract containing the active compound bacosides. However, the knowledge about the interactions between bacosides with TPH is limited. In this study, we take advantage of in silico approach to understand the interaction of bacoside-TPH complex using three different docking algorithms such as HexDock, PatchDock and AutoDock. All these three algorithms showed that bacoside A and A3 well fit into the cavity consists of active sites. Further, our analysis revealed that major active compounds bacoside A3 and A interact with different residues of TPH through hydrogen bond. Interestingly, Tyr235, Thr265 and Glu317 are the key residues among them, but none of them are either at tryptophan or BH4 binding region. However, its note worthy to mention that Tyr 235 is a catalytic sensitive residue, Thr265 is present in the flexible loop region and Glu317 is known to interacts with Fe. Interactions with these residues may critically regulate TPH function and thus serotonin synthesis. Our study suggested that the interaction of bacosides (A3/A) with TPH might up-regulate its activity to elevate the biosynthesis of 5-HT, thereby enhances learning and memory formation.
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Affiliation(s)
- David Mary Rajathei
- Department of Bioinformtics, Bharathidasan University, Tiruchirappalli, 620024 India
| | - Jayakumar Preethi
- Department of Animal Science, School of Life Sciences, Bharathidasan University, Tiruchirappalli, 620024 India
| | - Hemant K. Singh
- Laboratories of CNS Disorder, Learning & Memory, Division of Pharmacology, Central Drug Research Institute, Lucknow, 226031 India
| | - Koilmani Emmanuvel Rajan
- Department of Animal Science, School of Life Sciences, Bharathidasan University, Tiruchirappalli, 620024 India
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The tyrosine hydroxylase 2 (TH2) system in zebrafish brain and stress activation of hypothalamic cells. Histochem Cell Biol 2014; 142:619-33. [PMID: 25028341 DOI: 10.1007/s00418-014-1240-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2014] [Indexed: 01/13/2023]
Abstract
Two tyrosine hydroxylases (TH1 and TH2) are found in teleost fish, but no antibodies are available for TH2 protein to analyze the detailed structure of the system. We generated antibodies targeting TH2 and used them to characterize the TH2-producing cells in larval and adult zebrafish brain. The rabbit antisera reliably detected two bands corresponding to TH1 and TH2 close to 55 kDa in brain homogenates. The antisera detected neurons in brain nuclei which express th1 and th2 mRNA; knockdown of th2 expression by morpholino oligonucleotide injection abolished both the th2 mRNA signal and immunoreactivity with the rabbit antisera in TH2 cells. Double staining of samples with the rabbit antiserum made against TH2 and a monoclonal antibody which detects only TH1 allowed identification of cell groups expressing either one of the proteins. Cell groups in preoptic area, anterior, intermediate, and posterior part of the paraventricular organ contained neurons stained with the new TH2 antisera but not with the characterized monoclonal TH1 antibody. Neurons immunoreactive for TH2 and 5-HT were distinct. In situ hybridization for the mRNA of the immediate early gene c-fos combined with TH1/TH2 immunohistochemistry was used to characterize the cells of the zebrafish brain reacting to handling stress and a noxious chemical stimulus. Strong upregulation of c-fos expression was detected in hypothalamic nuclei containing TH2 cells, but few of the c-fos-expressing cells were positive for TH2, suggesting that these stressors do not directly activate a large proportion of TH2 cells.
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Carkaci-Salli N, Salli U, Tekin I, Hengst JA, Zhao MK, Gilman TL, Andrews AM, Vrana KE. Functional characterization of the S41Y (C2755A) polymorphism of tryptophan hydroxylase 2. J Neurochem 2014; 130:748-58. [PMID: 24899127 DOI: 10.1111/jnc.12779] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 05/23/2014] [Indexed: 01/11/2023]
Abstract
Human TPH2 (hTPH2) catalyzes the rate-limiting step in CNS serotonin biosynthesis. We characterized a single-nucleotide polymorphism (C2755A) in the hTPH2 gene that substitutes tyrosine for serine at position 41 in the regulatory domain of the enzyme. This polymorphism is associated with bipolar disorder and peripartum depression in a Chinese population. Recombinant h TPH2 human proteins were expressed in bacteria and also stably expressed in PC12 cells. Following bacterial expression and purification, the tyrosine for serine substitution at position 41 (S41Y) polymorphic enzyme displayed increased Vmax with unchanged Km values. By contrast, enzyme stability was decreased in vitro from 32 min to 4 min (37 °C) for the S41Y enzyme (as compared to the wild-type enzyme). The S41Y polymorphism decreased cyclic AMP-dependent protein kinase A-mediated phosphorylation ~ 50% relative to wild-type hTPH2, suggesting that the S41Y mutation may disrupt the post-translational regulation of this enzyme. Transfected PC12 cells expressed hTPH2 mRNA, active protein, and synthesized and released serotonin. Paradoxically, while S41Y-transfected PC12 cells expressed higher levels of hTPH2 than wild type, they synthesized less serotonin. These findings suggest a modified regulation of the S41Y gene variant leading to altered regulation and reduced neurotransmitter synthesis that may contribute to association of the polymorphism with bipolar disorder and depression. We report the functional implications of a polymorphic human tryptophan hydroxylase-2 gene associated with depression and bipolar disorder. The polymorphic enzyme (serine-41 converted to tyrosine) has increased activity, but decreased enzyme stability and serotonin production. Moreover, cyclic AMP-dependent protein kinase (PKA)-mediated phosphorylation of the mutant enzyme is decreased suggesting modified regulation of the S41Y variant leading to altered serotonin.
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Affiliation(s)
- Nurgul Carkaci-Salli
- Department of Pharmacology, Penn State College of Medicine, Hershey, Pennsylvania, USA
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Distribution of CaMKIIα expression in the brain in vivo, studied by CaMKIIα-GFP mice. Brain Res 2013; 1518:9-25. [PMID: 23632380 DOI: 10.1016/j.brainres.2013.04.042] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Revised: 04/17/2013] [Accepted: 04/18/2013] [Indexed: 01/08/2023]
Abstract
To facilitate the study of the CaMKIIα function in vivo, a CaMKIIα-GFP transgenic mouse line was generated. Here, our goal is to provide the first neuroanatomical characterization of GFP expression in the CNS of this line of mouse. Overall, CaMKIIα-GFP expression is strong and highly heterogeneous, with the dentate gyrus of the hippocampus as the most abundantly expressed region. In the hippocampus, around 70% of granule and pyramidal neurons expressed strong GFP. In the neocortex, presumed pyramidal neurons were GFP positive: around 32% of layer II/III and 35% of layer VI neurons expressed GFP, and a lower expression rate was found in other layers. In the thalamus and hypothalamus, strong GFP signals were detected in the neuropil. GFP-positive cells were also found in many other regions such as the spinal trigeminal nucleus, cerebellum and basal ganglia. We further compared the GFP expression with specific antibody staining for CaMKIIα and GABA. We found that GFP+ neurons were mostly positive for CaMKIIα-IR throughout the brain, with some exceptions throughout the brain, especially in the deeper layers of neocortex. GFP and GABA-IR marked distinct neuronal populations in most brain regions with the exception of granule cells in the olfactory bulb, purkinje cells in the cerebellar, and some layer I cells in neocortex. In conclusion, GFP expression in the CaMKIIα-GFP mice is similar to the endogenous expression of CaMKIIα protein, thus these mice can be used in in vivo and in vitro physiological studies in which visualization of CaMKIIα- neuronal populations is required.
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Phenylalanine hydroxylase (PAH) from the lower eukaryote Leishmania major. Mol Biochem Parasitol 2010; 175:58-67. [PMID: 20887755 DOI: 10.1016/j.molbiopara.2010.09.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2010] [Revised: 09/10/2010] [Accepted: 09/19/2010] [Indexed: 11/20/2022]
Abstract
Aromatic amino acid hydroxylases (AAAH) typically use tetrahydrobiopterin (H(4)B) as the cofactor. The protozoan parasite Leishmania major requires biopterin for growth and expresses strong salvage and regeneration systems to maintain H(4)B levels. Here we explored the consequences of genetic manipulation of the sole L. major phenylalanine hydroxylase (PAH) to explore whether it could account for the Leishmania H(4)B requirement. L. major PAH resembles AAAHs of other organisms, bearing eukaryotic-type domain organization, and conservation of key catalytic residues including those implicated in pteridine binding. A pah(-) null mutant and an episomal complemented overexpressing derivative (pah-/+PAH) were readily obtained, and metabolic labeling studies established that PAH was required to hydroxylate Phe to Tyr. Neither WT nor overexpressing lines were able to hydroxylate radiolabeled tyrosine or tryptophan, nor to synthesize catecholamines. WT but not pah(-) parasites showed reactivity with an antibody to melanin when grown with l-3,4-dihydroxyphenylalanine (L-DOPA), although the reactive product is unlikely to be melanin sensu strictu. WT was auxotrophic for Phe, Trp and Tyr, suggesting that PAH activity was insufficient to meet normal Tyr requirements. However, pah(-) showed an increased sensitivity to Tyr deprivation, while the pah(-)/+PAH overexpressor showed increased survival and could be adapted to grow well without added Tyr. pah(-) showed no alterations in H(4)B-dependent differentiation, as established by in vitro metacyclogenesis, or survival in mouse or macrophage infections. Thus Leishmania PAH may mitigate but not alleviate Tyr auxotrophy, but plays no essential role in the steps of the parasite infectious cycle. These findings suggest PAH is unlikely to explain the Leishmania requirement for biopterin.
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Cianchetta G, Stouch T, Yu W, Shi ZC, Tari LW, Swanson RV, Hunter MJ, Hoffman ID, Liu Q. Mechanism of Inhibition of Novel Tryptophan Hydroxylase Inhibitors Revealed by Co-crystal Structures and Kinetic Analysis. CURRENT CHEMICAL GENOMICS 2010; 4:19-26. [PMID: 20556201 PMCID: PMC2885594 DOI: 10.2174/1875397301004010019] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2010] [Revised: 02/26/2010] [Accepted: 02/26/2010] [Indexed: 11/22/2022]
Abstract
Trytophan Hydroxylase Type I (TPH1), most abundantly expressed in the gastrointestinal tract, initiates the synthesis of serotonin by catalyzing hydroxylation of tryptophan in the presence of biopterin and oxygen. We have previously described three series of novel, periphery-specific TPH1 inhibitors that selectively deplete serotonin in the gastrointestinal tract. We have now determined co-crystal structures of TPH1 with three of these inhibitors at high resolution. Analysis of the structural data showed that each of the three inhibitors fills the tryptophan binding pocket of TPH1 without reaching into the binding site of the cofactor pterin, and induces major conformational changes of the enzyme. The enzyme-inhibitor complexes assume a compact conformation that is similar to the one in tryptophan complex. Kinetic analysis showed that all three inhibitors are competitive versus the substrate tryptophan, consistent with the structural data that the compounds occupy the tryptophan binding site. On the other hand, all three inhibitors appear to be uncompetitive versus the cofactor 6-methyltetrahydropterin, which is not only consistent with the structural data but also indicate that the hydroxylation reaction follows an ordered binding mechanism in which a productive complex is formed only if tryptophan binds only after pterin, similar to the kinetic mechanisms of tyrosine and phenylalanine hydroxylase.
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Affiliation(s)
- Giovanni Cianchetta
- Department of Medicinal Chemistry, Lexicon Pharmaceuticals, Inc., 350 Carter Rd., Princeton, New Jersey, USA
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13
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Kino K, Hara R, Nozawa A. Enhancement of L-tryptophan 5-hydroxylation activity by structure-based modification of L-phenylalanine 4-hydroxylase from Chromobacterium violaceum. J Biosci Bioeng 2010; 108:184-9. [PMID: 19664549 DOI: 10.1016/j.jbiosc.2009.04.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2008] [Revised: 04/02/2009] [Accepted: 04/03/2009] [Indexed: 10/20/2022]
Abstract
The objective of this study was to enhance l-tryptophan hydroxylation activity of l-phenylalanine 4-hydroxylase. It had been known that l-phenylalanine 4-hydroxylase from Chromobacterium violaceum could convert l-tryptophan to 5-hydroxy-l-tryptophan and l-phenylalanine to l-tyrosine; however, the activity for l-tryptophan was extremely low compared to l-phenylalanine activity levels. We used the information on the crystal structures of aromatic amino acid hydroxylases to generate C. violaceuml-phenylalanine 4-hydroxylase with high l-tryptophan hydroxylating activity. In silico structural modeling analysis suggested that hydrophobic and/or stacking interactions with the substrate and cofactor at L101 and W180 in C. violaceuml-phenylalanine 4-hydroxylase would increase hydroxylation activity. Based on this hypothesis, we introduced a saturation mutagenesis towards these sites followed by the evaluation of 5-hydroxy-l-tryptophan productivity using a modified Gibbs assay. Three and nine positive mutants were obtained from the L101 and W180 mutant libraries, respectively. Among the mutants, L101Y and W180F showed the highest l-tryptophan hydroxylation activity at the respective residues. Steady-state kinetic analysis revealed that k(cat) values for l-tryptophan hydroxylation were increased from 0.40 (wild-type) to 1.02 (L101Y) and 0.51 s(-1) (W180F). In addition, the double mutant (L101Y-W180F) displayed higher l-tryptophan hydroxylation activity than the wild-type and the W180F and L101Y mutants. The k(cat) value of L101Y-W180F increased to 2.08 s(-1), showing a 5.2-fold increase compared to wild-type enzyme levels.
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Affiliation(s)
- Kuniki Kino
- Department of Applied Chemistry, Faculty of Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan.
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14
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McKinney JA, Turel B, Winge I, Knappskog PM, Haavik J. Functional properties of missense variants of human tryptophan hydroxylase 2. Hum Mutat 2009; 30:787-94. [PMID: 19319927 DOI: 10.1002/humu.20956] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Tryptophan hydroxylase 2 (TPH2) catalyzes the rate-limiting step in serotonin biosynthesis in the nervous system. Several variants of human TPH2 have been reported to be associated with a spectrum of neuropsychiatric disorders such as unipolar major depression, bipolar disorder, suicidality, and attention-deficit/hyperactivity disorder (ADHD). We used three different expression systems: rabbit reticulocyte lysate, Escherichia coli, and human embryonic kidney cells, to identify functional effects of all human TPH2 missense variants reported to date. The properties of mutants affecting the regulatory domain, that is, p.Leu36Val, p.Leu36Pro, p.Ser41Tyr, and p.Arg55Cys, were indistinguishable from the wild-type (WT). Moderate loss-of-function effects were observed for mutants in the catalytic and oligomerization domains, that is, p.Pro206Ser, p.Ala328Val, p.Arg441His, and p.Asp479Glu, which were manifested via stability and solubility effects, whereas p.Arg303Trp had severely reduced solubility and was completely inactive. All variants were tested as substrates for protein kinase A and were found to have similar phosphorylation stoichiometries. A standardized assay protocol as described here for activity and solubility screening should also be useful for determining properties of other TPH2 variants that will be discovered in the future.
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15
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Windahl MS, Petersen CR, Christensen HEM, Harris P. Crystal structure of tryptophan hydroxylase with bound amino acid substrate. Biochemistry 2008; 47:12087-94. [PMID: 18937498 DOI: 10.1021/bi8015263] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Tryptophan hydroxylase (TPH) is a mononuclear non-heme iron enzyme, which catalyzes the reaction between tryptophan, O 2, and tetrahydrobiopterin (BH 4) to produce 5-hydroxytryptophan and 4a-hydroxytetrahydrobiopterin. This is the first and rate-limiting step in the biosynthesis of the neurotransmitter and hormone serotonin (5-hydroxytryptamine). We have determined the 1.9 A resolution crystal structure of the catalytic domain (Delta1-100/Delta415-445) of chicken TPH isoform 1 (TPH1) in complex with the tryptophan substrate and an iron-bound imidazole. This is the first structure of any aromatic amino acid hydroxylase with bound natural amino acid substrate. The iron coordination can be described as distorted trigonal bipyramidal coordination with His273, His278, and Glu318 (partially bidentate) and one imidazole as ligands. The tryptophan stacks against Pro269 with a distance of 3.9 A between the iron and the tryptophan Czeta3 atom that is hydroxylated. The binding of tryptophan and maybe the imidazole has caused the structural changes in the catalytic domain compared to the structure of the human TPH1 without tryptophan. The structure of chicken TPH1 is more compact, and the loops of residues Leu124-Asp139 and Ile367-Thr369 close around the active site. Similar structural changes are seen in the catalytic domain of phenylalanine hydroxylase (PAH) upon binding of substrate analogues norleucine and thienylalanine to the PAH.BH 4 complex. In fact, the chicken TPH1.Trp.imidazole structure resembles the PAH.BH 4.thienylalanine structure more (root-mean-square deviation for Calpha atoms of 0.90 A) than the human TPH1 structure (root-mean-square deviation of 1.47 A).
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Affiliation(s)
- Michael S Windahl
- Department of Basic Sciences and Environment, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark
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16
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Murphy KL, Zhang X, Gainetdinov RR, Beaulieu JM, Caron MG. A regulatory domain in the N terminus of tryptophan hydroxylase 2 controls enzyme expression. J Biol Chem 2008; 283:13216-24. [PMID: 18339632 PMCID: PMC2442358 DOI: 10.1074/jbc.m706749200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2007] [Revised: 03/12/2008] [Indexed: 01/10/2023] Open
Abstract
Serotonin is involved in a variety of physiological processes in the central nervous system and the periphery. As the rate-limiting enzyme in serotonin synthesis, tryptophan hydroxylase plays an important role in modulating these processes. Of the two variants of tryptophan hydroxylase, tryptophan hydroxylase 2 (TPH2) is expressed predominantly in the central nervous system, whereas tryptophan hydroxylase 1 (TPH1) is expressed mostly in peripheral tissues. Although the two enzymes share considerable sequence homology, the regulatory domain of TPH2 contains an additional 41 amino acids at the N terminus that TPH1 lacks. Here we show that the extended TPH2 N-terminal domain contains a unique sequence involved in the regulation of enzyme expression. When expressed in cultured mammalian cells, TPH2 is synthesized less efficiently and is also less stable than TPH1. Removal of the unique portion of the N terminus of TPH2 results in expression of the enzyme at a level similar to that of TPH1, whereas protein chimeras containing this fragment are expressed at lower levels than their wild-type counterparts. We identify a region centered on amino acids 10-20 that mediates the bulk of this effect. We also demonstrate that phosphorylation of serine 19, a protein kinase A consensus site located in this N-terminal domain, results in increased TPH2 stability and consequent increases in enzyme output in cell culture systems. Because this domain is unique to TPH2, these data provide evidence for selective regulation of brain serotonin synthesis.
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Affiliation(s)
- Karen L Murphy
- Department of Neurobiology and Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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17
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Activation and stabilization of human tryptophan hydroxylase 2 by phosphorylation and 14-3-3 binding. Biochem J 2008; 410:195-204. [PMID: 17973628 DOI: 10.1042/bj20071033] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
TPH (tryptophan hydroxylase) catalyses the rate-limiting step in the synthesis of serotonin, and exists in two isoforms: TPH1, mainly found in peripheral tissues and the pineal body, and TPH2, a neuronal form. In the present study human TPH2 was expressed in Escherichia coli and in HEK (human embryonic kidney)-293 cells and phosphorylated using several different mammalian protein kinases. TPH2 was rapidly phosphorylated to a stoichiometry of 2 mol of phosphate/mol of subunit by PKA (protein kinase A), but only to a stoichiometry of 0.2 by Ca(2+)/calmodulin dependent protein kinase II. Both kinases phosphorylated Ser(19), but PKA also phosphorylated Ser(104), as determined by MS, phosphospecific antibodies and site-directed mutagenesis of several possible phosphorylation sites, i.e. Ser(19), Ser(99), Ser(104) and Ser(306). On average, purified TPH2 WT (wild-type) was activated by 30% after PKA phosphorylation and studies of the mutant enzymes showed that enzyme activation was mainly due to phosphorylation at Ser(19). This site was phosphorylated to a stoichiometry of up to 50% in HEK-293 cells expressing TPH2, and the enzyme activity and phosphorylation stoichiometry was further increased upon treatment with forskolin. Purified PKA-phosphorylated TPH2 bound to the 14-3-3 proteins gamma, epsilon and BMH1 with high affinity, causing a further increase in enzyme stability and activity. This indicates that 14-3-3 proteins could play a role in consolidating and strengthening the effects of phosphorylation on TPH2 and that they may be important for the regulation of serotonin function in the nervous system.
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Kuhn DM, Sakowski SA, Geddes TJ, Wilkerson C, Haycock JW. Phosphorylation and activation of tryptophan hydroxylase 2: identification of serine-19 as the substrate site for calcium, calmodulin-dependent protein kinase II. J Neurochem 2007; 103:1567-73. [PMID: 17727633 DOI: 10.1111/j.1471-4159.2007.04855.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Tryptophan hydroxylase (TPH) is the initial and rate-limiting enzyme in the biosynthesis of serotonin. TPH was once thought to be a single-gene product but it is now known to exist in two isoforms. TPH1 is found in the periphery and pineal gland whereas TPH2 is expressed specifically in the CNS. Both TPH isoforms are known to be regulated by protein kinase-dependent phosphorylation and the sites of modification of TPH1 by protein kinase A have been identified. While TPH2 is activated by calcium, calmodulin-dependent protein kinase II (CaMKII), the sites at which this isoform is modified are not known. Treatment of wild-type TPH2 with CaMKII followed by mass spectrometry analysis revealed that the enzyme was activated and phosphorylated at a single site, serine-19. Mutagenesis of serine-19 to alanine did not alter the catalytic function of TPH2 but this mutant enzyme was neither activated nor phosphorylated by CaMKII. A phosphopeptide bracketing phosphoserine-19 in TPH2 was used as an antigen to generate polyclonal antibodies against phosphoserine-19. The antibodies are highly specific for phosphoserine-19 in TPH2. The antibodies do not react with wild-type TPH2 or TPH1 and they do not recognize phophoserine-58 or phosphoserine-260 in TPH1. These results establish that activation of TPH2 by CaMKII is mediated by phosphorylation of serine-19 within the regulatory domain of the enzyme. Production of a specific antibody against the CaMKII phosphorylation site in TPH2 represents a valuable tool to advance the study of the mechanisms regulating the function of this important enzyme.
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Affiliation(s)
- Donald M Kuhn
- Department of Psychiatry & Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan, USA.
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19
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Tenner K, Walther D, Bader M. Influence of human tryptophan hydroxylase 2 N- and C-terminus on enzymatic activity and oligomerization. J Neurochem 2007; 102:1887-1894. [PMID: 17539919 DOI: 10.1111/j.1471-4159.2007.04664.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Tryptophan hydroxylase (TPH) catalyses the first and rate limiting step in the biosynthesis of the neurotransmitter serotonin. There are two TPH isoenzymes in humans, encoded by two different genes: TPH1 and the recently described TPH2. We have expressed both human enzymes and various deletion mutants of TPH2 (DeltaN44, DeltaC17, DeltaC19, DeltaC51) in COS7 cells. TPH1 and 2 displayed different kinetic properties with a lower K(m) value of TPH1. Removal of 44 amino acids from the N-terminus of TPH2 resulted in a 3-4-fold increased V(max), which indicates a strong inhibitory function of this part on the enzymes activity. TPH1 and 2 were able to form homooligomers and also heterooligomers with each other. The different deletion mutants (DeltaC17, DeltaC19 and DeltaC51), which lack the putative C-terminal leucine zipper tetramerization domain, existed as monomeric enzymes. While short deletions (DeltaC17 and DeltaC19) hardly changed V(max) values, the DeltaC51 mutant lost 99% of TPH activity. These data identify a region between the C-terminal oligomerization domain and the catalytic domain, which is indispensable for TPH2 activity.
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Affiliation(s)
- K Tenner
- Max Delbrück Center for Molecular Medicine, Berlin, GermanyMax Planck Institute for Molecular Genetics, Department for Human Genetics, Berlin, Germany
| | - D Walther
- Max Delbrück Center for Molecular Medicine, Berlin, GermanyMax Planck Institute for Molecular Genetics, Department for Human Genetics, Berlin, Germany
| | - M Bader
- Max Delbrück Center for Molecular Medicine, Berlin, GermanyMax Planck Institute for Molecular Genetics, Department for Human Genetics, Berlin, Germany
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20
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Carkaci-Salli N, Flanagan JM, Martz MK, Salli U, Walther DJ, Bader M, Vrana KE. Functional Domains of Human Tryptophan Hydroxylase 2 (hTPH2). J Biol Chem 2006; 281:28105-12. [PMID: 16864580 DOI: 10.1074/jbc.m602817200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in serotonin biosynthesis. A novel gene, termed TPH2, has recently been described. This gene is preferentially expressed in the central nervous system, while the original TPH1 is the peripheral gene. We have expressed human tryptophan hydroxylase 2 (hTPH2) and two deletion mutants (NDelta150 and NDelta150/CDelta24) using isopropyl beta-D-thiogalactopyranoside-free autoinduction in Escherichia coli. This expression system produced active wild type TPH2 with relatively low solubility. The solubility was increased for mutants lacking the NH(2)-terminal regulatory domain. The solubility of hTPH2, NDelta150, and NDelta150/CDelta24 are 6.9, 62, and 97.5%, respectively. Removal of the regulatory domain also produced a more than 6-fold increase in enzyme stability (t((1/2)) at 37 degrees C). The wild type hTPH2, like other members of the aromatic amino acid hydroxylase superfamily, exists as a homotetramer (236 kDa on size exclusion chromatography). Similarly, NDelta150 also migrates as a tetramer (168 kDa). In contrast, removal of the NH(2)-terminal domain and the COOH-terminal, putative leucine zipper tetramerization domain produces monomeric enzyme (39 kDa). Interestingly, removal of the NH(2)-terminal regulatory domain did not affect the Michaelis constants for either substrate but did increase V(max) values. These data identify the NH(2)-terminal regulatory domain as the source of hTPH2 instability and reduced solubility.
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Affiliation(s)
- Nurgul Carkaci-Salli
- Department of Pharmacology, Penn State College of Medicine, Hershey, Pennsylvania 17033-2360, USA
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21
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Yamauchi T. Neuronal Ca2+/calmodulin-dependent protein kinase II--discovery, progress in a quarter of a century, and perspective: implication for learning and memory. Biol Pharm Bull 2005; 28:1342-54. [PMID: 16079472 DOI: 10.1248/bpb.28.1342] [Citation(s) in RCA: 155] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Much has been learned about the activity-dependent synaptic modifications that are thought to underlie memory storage, but the mechanism by which these modifications are stored remains unclear. A good candidate for the storage mechanism is Ca2+/calmodulin-dependent protein kinase II (CaM kinase II). CaM kinase II is one of the most prominent protein kinases, present in essentially every tissue but most concentrated in brain. Although it has been about a quarter of a century since the finding, CaM kinase II has been of the major interest in the region of brain science. It plays a multifunctional role in many intracellular events, and the expression of the enzyme is carefully regulated in brain regions and during brain development. Neuronal CaM kinase II regulates important neuronal functions, including neurotransmitter synthesis, neurotransmitter release, modulation of ion channel activity, cellular transport, cell morphology and neurite extension, synaptic plasticity, learning and memory, and gene expression. Studies concerning this kinase have provided insight into the molecular basis of nerve functions, especially learning and memory, and indicate one direction for studies in the field of neuroscience. This review presents the molecular structure, properties and functions of CaM kinase II, as a major component of neurons, based mainly developed on findings made in our laboratory.
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Affiliation(s)
- Takashi Yamauchi
- Department of Biochemistry, Graduate School of Pharmaceutical Sciences, University of Tokushima, Shomachi 1, Tokushima 770-8585, Japan.
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22
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Abu-Omar MM, Loaiza A, Hontzeas N. Reaction mechanisms of mononuclear non-heme iron oxygenases. Chem Rev 2005; 105:2227-52. [PMID: 15941213 DOI: 10.1021/cr040653o] [Citation(s) in RCA: 447] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mahdi M Abu-Omar
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
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23
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McKinney J, Knappskog PM, Haavik J. Different properties of the central and peripheral forms of human tryptophan hydroxylase. J Neurochem 2005; 92:311-20. [PMID: 15663479 DOI: 10.1111/j.1471-4159.2004.02850.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Tryptophan hydroxylase (TPH) catalyses the rate-limiting reaction in the biosynthesis of serotonin. In humans, two different TPH genes exist, located on chromosomes 11 and 12, respectively, and encoding two enzymes (TPH1 and TPH2) with an overall sequence identity of 71%. We have expressed both enzymes as various fusion proteins in Escherichia coli and using an in vitro transcription/translation system, and compared their solubility and kinetic properties. TPH2 is more soluble than TPH1, has a higher molecular weight and different kinetic properties, including a lower catalytic efficiency towards phenylalanine than TPH1. Both enzymes are phosphorylated by cAMP-dependent protein kinase A. TPH2 was phosphorylated at Ser19, a phosphorylation site not present in TPH1. The differences between TPH1 and TPH2 have important implications for the regulation of serotonin production in the brain and the periphery and may provide an explanation for some of the diverging results reported for TPH from different sources in the past.
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Affiliation(s)
- Jeffrey McKinney
- Department of Biomedicine, Section of Biochemistry and Molecular Biology, University of Bergen, Bergen, Norway
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24
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Zhang X, Gainetdinov RR, Beaulieu JM, Sotnikova TD, Burch LH, Williams RB, Schwartz DA, Krishnan KRR, Caron MG. Loss-of-function mutation in tryptophan hydroxylase-2 identified in unipolar major depression. Neuron 2005; 45:11-6. [PMID: 15629698 DOI: 10.1016/j.neuron.2004.12.014] [Citation(s) in RCA: 362] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2004] [Revised: 11/29/2004] [Accepted: 12/07/2004] [Indexed: 11/15/2022]
Abstract
Dysregulation of central serotonin neurotransmission has been widely suspected as an important contributor to major depression. Here, we identify a (G1463A) single nucleotide polymorphism (SNP) in the rate-limiting enzyme of neuronal serotonin synthesis, human tryptophan hydroxylase-2 (hTPH2). The functional SNP in hTPH2 replaces the highly conserved Arg441 with His, which results in approximately 80% loss of function in serotonin production when hTPH2 is expressed in PC12 cells. Strikingly, SNP analysis in a cohort of 87 patients with unipolar major depression revealed that nine patients carried the mutant (1463A) allele, while among 219 controls, three subjects carried this mutation. In addition, this functional SNP was not found in a cohort of 60 bipolar disorder patients. Identification of a loss-of-function mutation in hTPH2 suggests that defect in brain serotonin synthesis may represent an important risk factor for unipolar major depression.
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Affiliation(s)
- Xiaodong Zhang
- Department of Cell Biology, Center for Models of Human Disease, Institute for Genome Sciences and Policy, Duke University Medical Center, Durham, NC 27710, USA
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Meurisse R, Brasseur R, Thomas A. Aromatic side-chain interactions in proteins: Near- and far-sequence Tyr-X pairs. Proteins 2003; 54:478-90. [PMID: 14747996 DOI: 10.1002/prot.10582] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In the present study, an extensive analysis of the aromatic Tyr-X interactions is performed on a data set of 593 PDB structures, X being Phe, His, Tyr, and Trp. The nonredundant Tyr-X pairs (2645) were retained and separated by both the residue distance in the sequence and the secondary structures they bridge. Similar to the Phe-X and His-X pairs, the far-sequence Tyr-X pairs (X partner > five apart in the sequence: 74%) show comparable secondary structures and conformers for either type of X partner, in contrast with the near-sequence Tyr-X pairs (26%). As the Phe-X pairs, the near-sequence Tyr-X pairs stabilize secondary structures, mainly the alpha- helices (positions 1, 3, and 4) and the beta-strands (position 2). Like the Phe-X and His-X pairs, most far-sequence Tyr-X pairs (34%) bridge beta-strands and only 11% bridge helices. As for the Phe-X and the His-X pairs, the X partners of the far-sequence Tyr-X pairs are frequently "above" the tyrosine ring with tilted and normal rings, whereas the X partner of the near-sequence Tyr-X pairs gradually moves from the "aside" to the "above" location, together with a progressive decrease of normal and increase of parallel rings, respectively. Unlike the His-X pairs, the interactions of the hetroatom in Tyr-X pairs are only favored with a sequence position +4 and over, owing to the spatial accessibility of the heteroatom.
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Affiliation(s)
- Rita Meurisse
- Centre de Biophysique Moléculaire Numérique, Faculté Scientifique Agronomique de Gembloux, Gembloux, Belgium.
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26
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Abstract
Serotonin (5-hydroxytryptophan, 5-HT) is a neurotransmitter synthesized in the raphe nuclei of the brain stem and involved in the central control of food intake, sleep, and mood. Accordingly, dysfunction of the serotonin system has been implicated in the pathogenesis of psychiatric diseases. At the same time, serotonin is a peripheral hormone produced mainly by enterochromaffin cells in the intestine and stored in platelets, where it is involved in vasoconstriction, haemostasis, and the control of immune responses. Moreover, serotonin is a precursor for melatonin and is therefore synthesized in high amounts in the pineal gland. Tryptophan hydroxylase (TPH) catalyzes the rate limiting step in 5-HT synthesis. Until recently, only one gene encoding TPH was described for vertebrates. By gene targeting, we functionally ablated this gene in mice. To our surprise, the resulting animals, although being deficient for serotonin in the periphery and in the pineal gland, exhibited close to normal levels of 5-HT in the brain stem. This led us to the detection of a second TPH gene in the genome of humans, mice, and rats, called TPH2. This gene is predominantly expressed in the brain stem, while the classical TPH gene, now called TPH1, is expressed in the gut, pineal gland, spleen, and thymus. These findings clarify puzzling data, which have been collected over the last decades about partially purified TPH proteins with different characteristics and justify a new concept of the serotonin system. In fact, there are two serotonin systems in vertebrates, independently regulated and with distinct functions.
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Affiliation(s)
- Diego J Walther
- Max Delbrück Center for Molecular Medicine (MDC), Robert-Rossle-Strasse 10, D-13092 Berlin-Buch, Germany
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27
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Maass A, Scholz J, Moser A. Modeled ligand-protein complexes elucidate the origin of substrate specificity and provide insight into catalytic mechanisms of phenylalanine hydroxylase and tyrosine hydroxylase. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:1065-75. [PMID: 12631267 DOI: 10.1046/j.1432-1033.2003.03429.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
NMR spectroscopy and X-ray crystallography have provided important insight into structural features of phenylalanine hydroxylase (PAH) and tyrosine hydroxylase (TH). Nevertheless, significant problems such as the substrate specificity of PAH and the different susceptibility of TH to feedback inhibition by l-3,4-dihydroxyphenylalanine (l-DOPA) compared with dopamine (DA) remain unresolved. Based on the crystal structures 5pah for PAH and 2toh for TH (Protein Data Bank), we have used molecular docking to model the binding of 6(R)-l-erythro-5,6,7,8-tetrahydrobiopterin (BH4) and the substrates phenylalanine and tyrosine to the catalytic domains of PAH and TH. The amino acid substrates were placed in positions common to both enzymes. The productive position of tyrosine in TH.BH4 was stabilized by a hydrogen bond with BH4. Despite favorable energy scores, tyrosine in a position trans to PAH residue His290 or TH residue His336 interferes with the access of the essential cofactor dioxygen to the catalytic center, thereby blocking the enzymatic reaction. DA and l-DOPA were directly coordinated to the active site iron via the hydroxyl residues of their catechol groups. Two alternative conformations, rotated 180 degrees around an imaginary iron-catecholamine axis, were found for DA and l-DOPA in PAH and for DA in TH. Electrostatic forces play a key role in hindering the bidentate binding of the immediate reaction product l-DOPA to TH, thereby saving the enzyme from direct feedback inhibition.
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Affiliation(s)
- Astrid Maass
- Fraunhofer-Institute for Algorithms and Scientific Computing (SCAI), Schloss Birlinghoven, Sankt Augustin, Germany.
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28
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Stultz CM, Levin AD, Edelman ER. Phosphorylation-induced conformational changes in a mitogen-activated protein kinase substrate. Implications for tyrosine hydroxylase activation. J Biol Chem 2002; 277:47653-61. [PMID: 12361946 DOI: 10.1074/jbc.m208755200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitogen-activated protein (MAP) kinase-mediated phosphorylation of specific residues in tyrosine hydroxylase leads to an increase in enzyme activity. However, the mechanism whereby phosphorylation affects enzyme turnover is not well understood. We used a combination of fluorescence resonance energy transfer (FRET) measurements and molecular dynamics simulations to explore the conformational free energy landscape of a 10-residue MAP kinase substrate found near the N terminus of the enzyme. This region is believed to be part of an autoregulatory sequence that overlies the active site of the enzyme. FRET was used to measure the effect of phosphorylation on the ensemble of peptide conformations, and molecular dynamics simulations generated free energy profiles for both the unphosphorylated and phosphorylated peptides. We demonstrate how FRET transfer efficiencies can be calculated from molecular dynamics simulations. For both the unphosphorylated and phosphorylated peptides, the calculated FRET efficiencies are in excellent agreement with the experimentally determined values. Moreover, the FRET measurements and molecular simulations suggest that phosphorylation causes the peptide backbone to change direction and fold into a compact structure relative to the unphosphorylated state. These results are consistent with a model of enzyme activation where phosphorylation of the MAP kinase substrate causes the N-terminal region to adopt a compact structure away from the active site. The methods we employ provide a general framework for analyzing the accessible conformational states of peptides and small molecules. Therefore, they are expected to be applicable to a variety of different systems.
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Affiliation(s)
- Collin M Stultz
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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Lee TH, Jang MH, Shin MC, Lim BV, Choi HH, Kim H, Kim EH, Kim CJ. Nicotine administration increases serotonin synthesis and tryptophan hydroxylase expression in dorsal raphe of food-deprived rats. Nutr Res 2002. [DOI: 10.1016/s0271-5317(02)00461-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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30
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Stokes AH, Freeman WM, Mitchell SG, Burnette TA, Hellmann GM, Vrana KE. Induction of GADD45 and GADD153 in neuroblastoma cells by dopamine-induced toxicity. Neurotoxicology 2002; 23:675-84. [PMID: 12520757 DOI: 10.1016/s0161-813x(02)00093-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Dopamine (DA) metabolism and oxidation produce both reactive oxygen species (ROS) and reactive quinones. These chemical species are implicated in dopamine neurotoxicity and neurodegeneration. In the present studies, human neuroblastoma (SK-N-SH) cells were exposed to toxic concentrations of dopamine (333 microM) in order to investigate molecular pathways involved in dopamine toxicity. cDNA hybridization array (microarray) technology demonstrated that GADD45 and GADD153 (growth arrest and DNA-damage inducible) gene expression was increased in dopamine-treated cells (333 microM for 18 h). Subsequent Northern and Western blot analysis confirmed these changes in GADD45 and GADD153 gene expression. The antioxidant, ascorbic acid, significantly reduced the increase in GADD45 gene expression but did not significantly reduce GADD153 gene expression. Currently, the precise function of the GADD gene products is not known. It is known, however, that these genes are upregulated in response to stress to allow cells time to repair macromolecular damage. In the present case, GADD gene expression (manifested as increased mRNA and protein levels) preceded dopamine-induced cytotoxicity. It appears that dopamine, through the formation of reactive oxygen species and quinones, may damage cellular macromolecules to the point of inducing GADD gene expression. Other genes that displayed changes, but that have not been subjected to post-hoc confirmation, include clusterin (increased), ubiquitin (increased), CD27 ligand (increased), CD27BP (increased), and rac-PK-beta (decreased).
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Affiliation(s)
- Alan H Stokes
- Department of Physiology and Pharmacology, Center for Neurobiological Investigation of Drug Abuse, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1083, USA
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Erlandsen H, Kim JY, Patch MG, Han A, Volner A, Abu-Omar MM, Stevens RC. Structural comparison of bacterial and human iron-dependent phenylalanine hydroxylases: similar fold, different stability and reaction rates. J Mol Biol 2002; 320:645-61. [PMID: 12096915 DOI: 10.1016/s0022-2836(02)00496-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Structure determination of bacterial homologues of human disease-related proteins provides an efficient path to understanding the three-dimensional fold of proteins that are associated with human diseases. However, the precise locations of active-site residues are often quite different between bacterial and human versions of an enzyme, creating significant differences in the biological understanding of enzyme homologs. To study this hypothesis, phenylalanine hydroxylase from a bacterial source has been structurally characterized at high resolution and comparison is made to the human analog. The enzyme phenylalanine hydroxylase (PheOH) catalyzes the hydroxylation of l-phenylalanine into l-tyrosine utilizing the cofactors (6R)-l-erythro-5,6,7,8 tetrahydrobiopterin (BH(4)) and molecular oxygen. Previously determined X-ray structures of human and rat PheOH, with a sequence identity of more than 93%, show that these two structures are practically identical. It is thus of interest to compare the structure of the divergent Chromobacterium violaceum phenylalanine hydroxylase (CvPheOH) ( approximately 24% sequence identity overall) to the related human and rat PheOH structures. We have determined crystal structures of CvPheOH to high resolution in the apo-form (no Fe-added), Fe(III)-bound form, and 7,8-dihydro-l-biopterin (7,8-BH(2)) plus Fe(III)-bound form. The bacterial enzyme displays higher activity and thermal melting temperature, and structurally, differences are observed in the N and C termini, and in a loop close to the active-site iron atom.
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Affiliation(s)
- Heidi Erlandsen
- The Scripps Research Institute, Department of Molecular Biology, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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McKinney J, Teigen K, Frøystein NA, Salaün C, Knappskog PM, Haavik J, Martínez A. Conformation of the substrate and pterin cofactor bound to human tryptophan hydroxylase. Important role of Phe313 in substrate specificity. Biochemistry 2001; 40:15591-601. [PMID: 11747434 DOI: 10.1021/bi015722x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tryptophan hydroxylase (TPH) carries out the 5-hydroxylation of L-Trp, which is the rate-limiting step in the synthesis of serotonin. We have prepared and characterized a stable N-terminally truncated form of human TPH that includes the catalytic domain (Delta90TPH). We have also determined the conformation and distances to the catalytic non-heme iron of both L-Trp and the tetrahydrobiopterin cofactor analogue L-erythro-7,8-dihydrobiopterin (BH2) bound to Delta90TPH by using 1H NMR spectroscopy. The bound conformers of the substrate and the pterin were then docked into the modeled three-dimensional structure of TPH. The resulting ternary TPH-BH2-L-Trp structure is very similar to that previously determined by the same methods for the complex of phenylalanine hydroxylase (PAH) with BH2 and L-Phe [Teigen, K., et al. (1999) J. Mol. Biol. 294, 807-823]. In the model, L-Trp binds to the enzyme through interactions with Arg257, Ser336, His272, Phe318, and Phe313, and the ring of BH2 interacts mainly with Phe241 and Glu273. The distances between the hydroxylation sites at C5 in L-Trp and C4a in the pterin, i.e., 6.1 +/- 0.4 A, and from each of these sites to the iron, i.e., 4.1 +/- 0.3 and 4.4 +/- 0.3 A, respectively, are also in agreement with the formation of a transient iron-4a-peroxytetrahydropterin in the reaction, as proposed for the other hydroxylases. The different conformation of the dihydroxypropyl chain of BH2 in PAH and TPH seems to be related to the presence of nonconserved residues, i.e., Tyr235 and Pro238 in TPH, at the cofactor binding site. Moreover, Phe313, which seems to interact with the substrate through ring stacking, corresponds to a Trp residue in both tyrosine hydroxylase and PAH (Trp326) and appears to be an important residue for influencing the substrate specificity in this family of enzymes. We show that the W326F mutation in PAH increases the relative preference for L-Trp as the substrate, while the F313W mutation in TPH increases the preference for L-Phe, possibly by a conserved active site volume effect.
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Affiliation(s)
- J McKinney
- Department of Biochemistry and Molecular Biology, University of Bergen, Arstadveien 19, N-5009 Bergen, Norway
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Jennings IG, Teh T, Kobe B. Essential role of the N-terminal autoregulatory sequence in the regulation of phenylalanine hydroxylase. FEBS Lett 2001; 488:196-200. [PMID: 11163771 DOI: 10.1016/s0014-5793(00)02426-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Phenylalanine hydroxylase (PAH) is activated by its substrate phenylalanine and inhibited by its cofactor tetrahydrobiopterin (BH(4)). The crystal structure of PAH revealed that the N-terminal sequence of the enzyme (residues 19-29) partially covered the enzyme active site, and suggested its involvement in regulation. We show that the protein lacking this N-terminal sequence does not require activation by phenylalanine, shows an altered structural response to phenylalanine, and is not inhibited by BH(4). Our data support the model where the N-terminal sequence of PAH acts as an intrasteric autoregulatory sequence, responsible for transmitting the effect of phenylalanine activation to the active site.
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Affiliation(s)
- I G Jennings
- Structural Biology Laboratory, St. Vincent's Institute of Medical Research, Fitzroy, Vic., Australia
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