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Blackwell AM, Jami-Alahmadi Y, Nasamu AS, Kudo S, Senoo A, Slam C, Tsumoto K, Wohlschlegel JA, Caaveiro JMM, Goldberg DE, Sigala PA. Malaria parasites require a divergent heme oxygenase for apicoplast gene expression and biogenesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.30.596652. [PMID: 38853871 PMCID: PMC11160694 DOI: 10.1101/2024.05.30.596652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Malaria parasites have evolved unusual metabolic adaptations that specialize them for growth within heme-rich human erythrocytes. During blood-stage infection, Plasmodium falciparum parasites internalize and digest abundant host hemoglobin within the digestive vacuole. This massive catabolic process generates copious free heme, most of which is biomineralized into inert hemozoin. Parasites also express a divergent heme oxygenase (HO)-like protein (PfHO) that lacks key active-site residues and has lost canonical HO activity. The cellular role of this unusual protein that underpins its retention by parasites has been unknown. To unravel PfHO function, we first determined a 2.8 Å-resolution X-ray structure that revealed a highly α-helical fold indicative of distant HO homology. Localization studies unveiled PfHO targeting to the apicoplast organelle, where it is imported and undergoes N-terminal processing but retains most of the electropositive transit peptide. We observed that conditional knockdown of PfHO was lethal to parasites, which died from defective apicoplast biogenesis and impaired isoprenoid-precursor synthesis. Complementation and molecular-interaction studies revealed an essential role for the electropositive N-terminus of PfHO, which selectively associates with the apicoplast genome and enzymes involved in nucleic acid metabolism and gene expression. PfHO knockdown resulted in a specific deficiency in levels of apicoplast-encoded RNA but not DNA. These studies reveal an essential function for PfHO in apicoplast maintenance and suggest that Plasmodium repurposed the conserved HO scaffold from its canonical heme-degrading function in the ancestral chloroplast to fulfill a critical adaptive role in organelle gene expression.
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Affiliation(s)
| | | | - Armiyaw S. Nasamu
- Departments of Medicine and Molecular Microbiology, Washington University School of Medicine, St. Louis, MO
| | - Shota Kudo
- Department of Chemistry & Biotechnology, The University of Tokyo, Tokyo, Japan
| | - Akinobu Senoo
- Department of Protein Drug Discovery, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Celine Slam
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT
| | - Kouhei Tsumoto
- Department of Chemistry & Biotechnology, The University of Tokyo, Tokyo, Japan
- Department of Bioengineering, University of Tokyo, Tokyo, Japan
| | | | - Jose M. M. Caaveiro
- Department of Chemistry & Biotechnology, The University of Tokyo, Tokyo, Japan
| | - Daniel E. Goldberg
- Departments of Medicine and Molecular Microbiology, Washington University School of Medicine, St. Louis, MO
| | - Paul A. Sigala
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT
- Departments of Medicine and Molecular Microbiology, Washington University School of Medicine, St. Louis, MO
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2
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Chiura T, Mak PJ. Investigation of Cyanide Ligand as an Active Site Probe of Human Heme Oxygenase. Inorg Chem 2021; 60:4633-4645. [PMID: 33754715 DOI: 10.1021/acs.inorgchem.0c03611] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Human heme oxygenase (hHO-1) is a physiologically important enzyme responsible for free heme catabolism. The enzyme's high regiospecificity is controlled by the distal site hydrogen bond network that involves water molecules and the D140 amino acid residue. In this work, we probe the active site environment of the wild-type (WT) hHO-1 and its D140 mutants using resonance Raman (rR) spectroscopy. Cyanide ligands are more stable than dioxygen adducts and are an effective probe of active site environment of heme proteins. The inherently linear geometry of the Fe-C-N fragment can be altered by the steric, electrostatic, and H-bonding interactions imposed by the amino acid residues present in the heme distal site, resulting in a tilted or bent configuration. The WT hHO-1 and its D140A, D140N, and D140E mutants were studied in the presence of natural abundance CN- and its isotopic analogues (13CN-, C15N-, and 13C15N-). Deconvolution of spectral data revealed that the ν(Fe-CN) stretching and δ(Fe-CN) bending modes are present at 454 and 376 cm-1, respectively. The rR spectral patterns of the CN- adducts of WT revealed that the Fe-C-N fragment adopts a tilted conformation, with a larger bending contribution for the D140A, D140N, and D140E mutants. These studies suggest that the FeCN fragment in hHO-1 is tilted more strongly toward the porphyrin macrocycle compared to other histidine-ligated proteins, reflecting the propensity of the exogenous hHO-l ligands to position toward the α-meso-carbon, which is crucial for the HO reactivity and essential for regioselectivity.
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Affiliation(s)
- Tapiwa Chiura
- Chemistry Department, Saint Louis University, Saint Louis, Missouri 63103, United States
| | - Piotr J Mak
- Chemistry Department, Saint Louis University, Saint Louis, Missouri 63103, United States
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3
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Fleischhacker AS, Gunawan AL, Kochert BA, Liu L, Wales TE, Borowy MC, Engen JR, Ragsdale SW. The heme-regulatory motifs of heme oxygenase-2 contribute to the transfer of heme to the catalytic site for degradation. J Biol Chem 2020; 295:5177-5191. [PMID: 32152224 PMCID: PMC7170523 DOI: 10.1074/jbc.ra120.012803] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 03/03/2020] [Indexed: 11/06/2022] Open
Abstract
Heme-regulatory motifs (HRMs) are present in many proteins that are involved in diverse biological functions. The C-terminal tail region of human heme oxygenase-2 (HO2) contains two HRMs whose cysteine residues form a disulfide bond; when reduced, these cysteines are available to bind Fe3+-heme. Heme binding to the HRMs occurs independently of the HO2 catalytic active site in the core of the protein, where heme binds with high affinity and is degraded to biliverdin. Here, we describe the reversible, protein-mediated transfer of heme between the HRMs and the HO2 core. Using hydrogen-deuterium exchange (HDX)-MS to monitor the dynamics of HO2 with and without Fe3+-heme bound to the HRMs and to the core, we detected conformational changes in the catalytic core only in one state of the catalytic cycle-when Fe3+-heme is bound to the HRMs and the core is in the apo state. These conformational changes were consistent with transfer of heme between binding sites. Indeed, we observed that HRM-bound Fe3+-heme is transferred to the apo-core either upon independent expression of the core and of a construct spanning the HRM-containing tail or after a single turnover of heme at the core. Moreover, we observed transfer of heme from the core to the HRMs and equilibration of heme between the core and HRMs. We therefore propose an Fe3+-heme transfer model in which HRM-bound heme is readily transferred to the catalytic site for degradation to facilitate turnover but can also equilibrate between the sites to maintain heme homeostasis.
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Affiliation(s)
- Angela S Fleischhacker
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109-0606
| | - Amanda L Gunawan
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109-0606
| | - Brent A Kochert
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115
| | - Liu Liu
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109-0606
| | - Thomas E Wales
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115
| | - Maelyn C Borowy
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109-0606
| | - John R Engen
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115
| | - Stephen W Ragsdale
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109-0606.
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4
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Irvin J, Ropelewski AJ, Perozich J. In silico analysis of heme oxygenase structural homologues identifies group-specific conservations. FEBS Open Bio 2017; 7:1480-1498. [PMID: 28979838 PMCID: PMC5623701 DOI: 10.1002/2211-5463.12275] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 06/25/2017] [Accepted: 07/16/2017] [Indexed: 12/04/2022] Open
Abstract
Heme oxygenases (HO) catalyze the breakdown of heme, aiding the recycling of its components. Several other enzymes have homologous tertiary structures to HOs, while sharing little sequence homology. These homologues include thiaminases, the hydroxylase component of methane monooxygenases, and the R2 component of Class I ribonucleotide reductases (RNR). This study compared these structural homologues of HO, using a large number of protein sequences for each homologue. Alignment of a total of 472 sequences showed little sequence conservation, with no residues having conservation in more than 80% of aligned sequences and only five residues conserved in at least 60% of the sequences. Fourteen additional positions, most of which were critical for hydrophobic packing, displayed amino acid similarity of 60% or higher. Ten conserved sequence motifs were identified in HOs and RNRs. Phylogenetic analysis verified the existence of the four distinct groups of HO homologues, which were then analyzed by group entropy analysis to identify residues critical to the unique function of each enzyme. Other methods for determining functional residues were also performed. Several common index positions identified represent critical evolutionary changes that resulted in the unique function of each enzyme, suggesting potential targets for site‐directed mutagenesis. These positions included residues that coordinate ligands, form the active sites, and maintain enzyme structure. Enzymes Heme oxygenase (EC 1.14.14.18), methane monooxygenase (EC 1.14.13.25), ribonucleotide reductase (EC 1.17.4.1), thiaminase II (EC 3.5.99.2).
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Affiliation(s)
- Joseph Irvin
- Department of Biology Franciscan University of Steubenville OH USA
| | | | - John Perozich
- Department of Biology Franciscan University of Steubenville OH USA
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5
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Soldano A, Klinke S, Otero LH, Rivera M, Catalano-Dupuy DL, Ceccarelli EA. Structural and mutational analyses of the Leptospira interrogans virulence-related heme oxygenase provide insights into its catalytic mechanism. PLoS One 2017; 12:e0182535. [PMID: 28771589 PMCID: PMC5542595 DOI: 10.1371/journal.pone.0182535] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 07/19/2017] [Indexed: 11/25/2022] Open
Abstract
Heme oxygenase from Leptospira interrogans is an important virulence factor. During catalysis, redox equivalents are provided to this enzyme by the plastidic-type ferredoxin-NADP+ reductase also found in L. interrogans. This process may have evolved to aid this bacterial pathogen to obtain heme-iron from their host and enable successful colonization. Herein we report the crystal structure of the heme oxygenase-heme complex at 1.73 Å resolution. The structure reveals several distinctive features related to its function. A hydrogen bonded network of structural water molecules that extends from the catalytic site to the protein surface was cleared observed. A depression on the surface appears to be the H+ network entrance from the aqueous environment to the catalytic site for O2 activation, a key step in the heme oxygenase reaction. We have performed a mutational analysis of the F157, located at the above-mentioned depression. The mutant enzymes were unable to carry out the complete degradation of heme to biliverdin since the reaction was arrested at the verdoheme stage. We also observed that the stability of the oxyferrous complex, the efficiency of heme hydroxylation and the subsequent conversion to verdoheme was adversely affected. These findings underscore a long-range communication between the outer fringes of the hydrogen-bonded network of structural waters and the heme active site during catalysis. Finally, by analyzing the crystal structures of ferredoxin-NADP+ reductase and heme oxygenase, we propose a model for the productive association of these proteins.
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Affiliation(s)
- Anabel Soldano
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Sebastián Klinke
- Fundación Instituto Leloir, IIBBA-CONICET, and Plataforma Argentina de Biología Estructural y Metabolómica PLABEM, Buenos Aires, Argentina
| | - Lisandro H. Otero
- Fundación Instituto Leloir, IIBBA-CONICET, and Plataforma Argentina de Biología Estructural y Metabolómica PLABEM, Buenos Aires, Argentina
| | - Mario Rivera
- Department of Chemistry and Ralph N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Lawrence, Kansas, United States of America
| | - Daniela L. Catalano-Dupuy
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Eduardo A. Ceccarelli
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
- * E-mail:
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6
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Enhancement of DEN-induced liver tumorigenesis in heme oxygenase-1 G143H mutant transgenic mice. Biochem Biophys Res Commun 2016; 481:169-175. [PMID: 27810363 DOI: 10.1016/j.bbrc.2016.10.148] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 10/30/2016] [Indexed: 12/25/2022]
Abstract
Heme oxygenase (HO) is the rate-limiting enzyme in heme metabolism. HO-1 exhibits anti-oxidative and anti-inflammatory function via the actions of its metabolite, respectively. A growing body of evidence demonstrates that HO-1 is implicated in the pathogenesis and progression of several types of cancer. However, whether HO-1 takes part in healthy-premalignant-malignant transformation is still undefined. In this study, we took advantage of transgenic mice which over-expressed HO-1 dominant negative mutant (HO-1 G143H) and observed its susceptibility to DEN-induced hepatocarcinogenesis. Our results indicate that HO-1 G143H mutant accelerates the progression of tumorigenesis and tumor growth. The mechanism is closely related to enhancement of ROS production which induce more hepatocytes death and secretion of inflammatory cytokines, proliferation of surviving hepatocytes. Our result provides the direct evidence that HO-1 plays an important protective role in liver carcinogenesis. Alternatively, we suggest the possible explanation on effect of HO-1 promoter polymorphism which involved in tumorigenesis.
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7
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Greil J, Verga-Falzacappa MV, Echner NE, Behnisch W, Bandapalli OR, Pechanska P, Immenschuh S, Vijayan V, Balla J, Tsukahara H, Schneider M, Janka G, Claus M, Longerich T, Muckenthaler MU, Kulozik AE. Mutating heme oxygenase-1 into a peroxidase causes a defect in bilirubin synthesis associated with microcytic anemia and severe hyperinflammation. Haematologica 2016; 101:e436-e439. [PMID: 27662012 DOI: 10.3324/haematol.2016.147090] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Affiliation(s)
- Johann Greil
- Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg, Germany
| | | | - Nicole E Echner
- Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg, Germany
| | - Wolfgang Behnisch
- Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg, Germany
| | - Obul R Bandapalli
- Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg, Germany
| | - Paulina Pechanska
- Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg, Germany
| | | | - Vijith Vijayan
- Institute for Transfusion Medicine, Hannover Medical School, Germany
| | - Jozsef Balla
- Department. of Nephrology, Medical and Health Science Center, University of Debrecen, Hungary.,MTA-DE Vascular Biology, Thrombosis and Hemostasis Research Group, Hungarian Academy of Sciences Debrecen, Hungary
| | - Hirokatsu Tsukahara
- Department of Pediatrics, Okayama University Graduate School of Medicine, Japan
| | - Marion Schneider
- Section of Experimental Anesthesiology, University of Ulm, Germany
| | - Gritta Janka
- Department of Hematology and Oncology, Children's Hospital, University of Hamburg, Germany
| | - Maren Claus
- Institute for Immunology, University Heidelberg, Germany
| | | | - Martina U Muckenthaler
- Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg, Germany
| | - Andreas E Kulozik
- Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg, Germany
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8
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Liu Q, Wang B, Yin Y, Chen G, Wang W, Gao X, Wang P, Zhou H. Overexpressions of HO-1/HO-1G143H in C57/B6J mice affect melanoma B16F10 lung metastases rather than change the survival rate of mice-bearing tumours. Exp Biol Med (Maywood) 2013; 238:696-704. [PMID: 23918881 DOI: 10.1177/1535370213490628] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/29/2023] Open
Abstract
Heme oxygenase-1 (HO-1) is often upregulated in tumour tissues and endows tumour cells with cytoprotection and antiapoptosis. It is worthy of note that some people show higher activity of HO-1 and some anti-cancer therapies could induce HO-1 expression in normal tissues, but the effect of HO-1 of normal tissues on tumours among these people remains unknown. To assess the effect of HO-1 of normal tissues on tumour progressiveness, we investigated the growth, metastasis and angiogenic potential of murine melanoma B16F10 cells in transgenic mice overexpressing HO-1 and its negative dominant mutant HO-1G143H, respectively. The results demonstrated that neither overexpression of HO-1 nor overexpression of HO-1G143H in normal tissues could significantly change the survival rate of tumour-bearing mice, but HO-1 overexpression could inhibit lung metastases and HO-1G143H could significantly promote lung metastases. Meanwhile, the leukocytes infiltration was reduced and angiogenesis was promoted in tumours in mice overexpressing HO-1, but the opposite was true in mice overexpressing HO-1G143H. Our findings suggested that overexpression of HO-1 might be conducive to patients bearing melanoma metastasis.
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Affiliation(s)
- Qingjun Liu
- Institute of Transfusion Medicine, Academy of Military Medical Sciences, Beijing 100850, China
| | - Bo Wang
- Institute of Transfusion Medicine, Academy of Military Medical Sciences, Beijing 100850, China
| | - Yujing Yin
- Institute of Transfusion Medicine, Academy of Military Medical Sciences, Beijing 100850, China
| | - Gan Chen
- Institute of Transfusion Medicine, Academy of Military Medical Sciences, Beijing 100850, China
| | - Wei Wang
- Department of Biochemistry and Molecular Biology, Harbin Medical University, Harbin 150081, China
| | - Xu Gao
- Department of Biochemistry and Molecular Biology, Harbin Medical University, Harbin 150081, China
| | - Peng Wang
- Laboratory Animal Center, Academy of Military Medical Sciences, Beijing 100071, China
| | - Hong Zhou
- Institute of Transfusion Medicine, Academy of Military Medical Sciences, Beijing 100850, China
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9
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The Activity of SV40 Promoter Can Be Inhibited by Overexpression of Heme Oxygenase-1 in Tumor Cells. Cell Biochem Biophys 2012; 65:287-95. [DOI: 10.1007/s12013-012-9431-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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10
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Zou C, Zhang H, Li Q, Xiao H, Yu L, Ke S, Zhou L, Liu W, Wang W, Huang H, Ma N, Liu Q, Wang X, Zhao W, Zhou H, Gao X. Heme oxygenase-1: a molecular brake on hepatocellular carcinoma cell migration. Carcinogenesis 2011; 32:1840-8. [PMID: 22016469 DOI: 10.1093/carcin/bgr225] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Hepatocellular carcinoma (HCC) is a fatal disease with great public health impact worldwide. Heme oxygenase (HO)-1 has recently been reported as an important player in tumor angiogenesis and metastasis. However, the role of HO-1 in liver cancer metastasis is unclear. In this study, we explored genetic differences and downstream signal transduction pathways of HO-1 in liver cancer cell lines. HO-1 wild-type and mutant cell lines were generated from human liver cancer cell line HepG2. The overexpression of wild-type HO-1 decreased the migration of HepG2 cells. In contrast, the overexpression of mutant HO-1G143H increased the migration of the cancer cells. Interleukin (IL)-6 is one of the major downstream molecules that mediated this process because IL-6 expression and migration are suppressed by HO-1 and increased when HO-1 is knocked down by shRNA. In addition, we demonstrated carbon monoxide (CO) and p38MAPK are the cofactors in this signal pathway. In vivo animal model demonstrated HO-1 inhibited the tumor growth. In conclusion, in vitro and in vivo data show HO-1 inhibits the human HCC cells migration and tumor growth by suppressing the expression of IL-6. The heme degradation product CO is a cofactor in this process and inhibits p38MAPK phosphorylation.
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Affiliation(s)
- C Zou
- Department of Biochemistry and Molecular Biology, Harbin Medical University, Harbin 150081, China
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11
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Zhou L, Liu Y, Zou C, Ma N, Hui Y, Lv G, Zhang H, Zhou H, Gao X. The Effect of the Gly139His, Gly143His, and Ser142His Mouse Heme Oxygenase-1 Mutants on the HO Reaction In Vivo and In Vitro. Anat Rec (Hoboken) 2010; 294:112-8. [DOI: 10.1002/ar.21284] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Accepted: 09/06/2010] [Indexed: 11/08/2022]
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12
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Unno M, Matsui T, Ikeda-Saito M. Structure and catalytic mechanism of heme oxygenase. Nat Prod Rep 2007; 24:553-70. [PMID: 17534530 DOI: 10.1039/b604180a] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Masaki Unno
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan
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13
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Li H, Igarashi J, Jamal J, Yang W, Poulos TL. Structural studies of constitutive nitric oxide synthases with diatomic ligands bound. J Biol Inorg Chem 2006; 11:753-68. [PMID: 16804678 DOI: 10.1007/s00775-006-0123-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2006] [Accepted: 05/18/2006] [Indexed: 10/24/2022]
Abstract
Crystal structures are reported for the endothelial nitric oxide synthase (eNOS)-arginine-CO ternary complex as well as the neuronal nitric oxide synthase (nNOS) heme domain complexed with L: -arginine and diatomic ligands, CO or NO, in the presence of the native cofactor, tetrahydrobiopterin, or its oxidized analogs, dihydrobiopterin and 4-aminobiopterin. The nature of the biopterin has no influence on the diatomic ligand binding. The binding geometries of diatomic ligands to nitric oxide synthase (NOS) follow the {MXY}(n) formalism developed from the inorganic diatomic-metal complexes. The structures reveal some subtle structural differences between eNOS and nNOS when CO is bound to the heme which correlate well with the differences in CO stretching frequencies observed by resonance Raman techniques. The detailed hydrogen-bonding geometries depicted in the active site of nNOS structures indicate that it is the ordered active-site water molecule rather than the substrate itself that would most likely serve as a direct proton donor to the diatomic ligands (CO, NO, as well as O(2)) bound to the heme. This has important implications for the oxygen activation mechanism critical to NOS catalysis.
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Affiliation(s)
- Huiying Li
- Department of Molecular Biology and Biochemistry, Center in Chemical and Structural Biology, University of California, Irvine, CA 92697-3900, USA
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14
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Utas JE, Kritikos M, Sandström D, Akermark B. Water as a hydrogen bonding bridge between a phenol and imidazole. A simple model for water binding in enzymes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:1592-6. [PMID: 17045565 DOI: 10.1016/j.bbabio.2006.08.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Revised: 07/25/2006] [Accepted: 08/08/2006] [Indexed: 11/26/2022]
Abstract
The X-ray crystal structure of the mono-hydrate of 2,2-bis(imidazol-1-ylmethyl)-4-methylphenol has been determined. Three hydrogen bonds hold water very tightly in the crystal, as determined by deuterium solid-state NMR. The hydrogen bond between the phenolic hydroxyl and water appears to have about the same strength as the direct hydrogen bond to imidazole, suggesting that the structure can be a good model for hydrogen bonds that are mediated by a water molecule in enzymes.
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Affiliation(s)
- Josefin E Utas
- Department of Organic Chemistry, Inorganic and Structural Chemistry, Arrhenius Laboratory, Stockholm University, 106 91 Stockholm, Sweden
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