1
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Petzinna SM, Bauer CJ, Schäfer VS. Vascular-adhesion protein 1 in giant cell arteritis and polymyalgia rheumatica. Front Med (Lausanne) 2024; 11:1448157. [PMID: 39206172 PMCID: PMC11349539 DOI: 10.3389/fmed.2024.1448157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2024] [Accepted: 08/05/2024] [Indexed: 09/04/2024] Open
Abstract
Vascular adhesion protein-1 (VAP-1) is a type 2 transmembrane sialoglycoprotein with oxidative deamination functionality, encoded by the amine oxidase copper-containing 3 (AOC3) gene. VAP-1 is widely expressed across various tissues, particularly in highly vascularized tissues and organs essential for lymphocyte circulation. In the vascular system, VAP-1 is predominantly found in vascular smooth muscle cells and endothelial cells, with higher expression levels in vascular smooth muscle cells. Under inflammatory conditions, VAP-1 rapidly translocates to the endothelial cell surface, facilitating leukocyte adhesion and migration through interactions with specific ligands, such as sialic acid-binding immunoglobulin-type lectins (Siglec)-9 on neutrophils and monocytes, and Siglec-10 on B cells, monocytes, and eosinophils. This interaction is crucial for leukocyte transmigration into inflamed tissues. Furthermore, VAP-1's enzymatic activity generates hydrogen peroxide and advanced glycation end-products, contributing to cytotoxic damage and vascular inflammation. In this context, the soluble form of VAP-1 (sVAP-1), produced by matrix metalloproteinase cleavage from its membrane-bound counterpart, also significantly influences leukocyte migration. This review aims to elucidate the multifaceted pathophysiological roles of VAP-1 in vascular inflammation, particularly in giant cell arteritis (GCA) and associated polymyalgia rheumatica (PMR). By exploring its involvement in immune cell adhesion, migration, and its enzymatic contributions to oxidative stress and tissue damage, we investigate the importance of VAP-1 in GCA. Additionally, we discuss recent advancements in imaging techniques targeting VAP-1, such as [68Ga]Ga-DOTA-Siglec-9 PET/CT, which have provided new insights into VAP-1's role in GCA and PMR. Overall, understanding VAP-1's comprehensive roles could pave the way for improved strategies in managing these conditions.
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2
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Danielli M, Thomas RC, Quinn LM, Tan BK. Vascular adhesion protein-1 (VAP-1) in vascular inflammatory diseases. VASA 2022; 51:341-350. [DOI: 10.1024/0301-1526/a001031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Summary: Vascular adhesion protein-1 (VAP-1) also known as amino oxidase copper containing 3 (AOC3) is a pro-inflammatory and versatile molecule with adhesive and enzymatic properties. VAP-1 is a primary amine oxidase belonging to the semicarbazide-sensitive amine oxidase (SSAO) family, which catalyzes the oxidation of primary amines leading to the production of ammonium, formaldehyde, methylglyoxal, and hydrogen peroxide. VAP-1 is mainly expressed by endothelial cells, smooth muscle cells, adipocytes and pericytes. It is involved in a repertoire of biological functions, e.g., immune cell extravasation, angiogenesis, and vascularization. Research into VAP-1 has intensified within the last decade on its role as a novel clinical biomarker and as a potential therapeutic target of vascular inflammatory disorders such as atherosclerosis, stroke, diabetes, neurovascular disorders (e.g., Alzheimer’s Disease), hepatic disease (e.g., non-alcoholic steatohepatitis), and skin conditions (e.g., psoriasis). This is the most up-to-date and comprehensive review on VAP-1 focusing on the translational aspects of VAP-1. Compared to recent reviews, our review provides novel insights on VAP-1 and heart failure, stroke and frailty, diabetes, endometriosis, osteoarthritis, COVID-19, conjunctivitis associated systemic lupus erythematosus, hematopoietic stem cells, gliomas, treatment of colorectal cancer with a novel VAP-1 inhibitor (U-V269), promoting recovery of motor functions and habit learning with a novel VAP-1 inhibitor (PXS-4681A), and 68Ga-DOTA-Siglec-9, a labelled peptide of Siglec-9 (a VAP-1 ligand), which appears to be a safe PET tracer for inflammation in rheumatoid arthritis. Finally, we present the emerging role of VAP-1 in pregnancy as a gatekeeper of immune cells, which are critical for spiral arterial remodeling, the deficiency of which could lead to vascular disorders of pregnancy such as preeclampsia. Future research should prioritize clinical trials on VAP-1 small-molecule inhibitors and monoclonal antibodies, thus, maximizing the potential of VAP-1 targeted therapy as well as research into sVAP-1 as a clinical biomarker of diseases and its prognosis.
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Affiliation(s)
- Marianna Danielli
- Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
| | | | - Lauren Marie Quinn
- Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, United Kingdom
| | - Bee Kang Tan
- Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
- Diabetes Research Centre, Leicester General Hospital, Leicester, United Kingdom
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3
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Blum E, Zhang J, Zaluski J, Einstein DE, Korshin EE, Kubas A, Gruzman A, Tochtrop GP, Kiser PD, Palczewski K. Rational Alteration of Pharmacokinetics of Chiral Fluorinated and Deuterated Derivatives of Emixustat for Retinal Therapy. J Med Chem 2021; 64:8287-8302. [PMID: 34081480 DOI: 10.1021/acs.jmedchem.1c00279] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recycling of all-trans-retinal to 11-cis-retinal through the visual cycle is a fundamental metabolic pathway in the eye. A potent retinoid isomerase (RPE65) inhibitor, (R)-emixustat, has been developed and tested in several clinical trials; however, it has not received regulatory approval for use in any specific retinopathy. Rapid clearance of this drug presents challenges to maintaining concentrations in eyes within a therapeutic window. To address this pharmacokinetic inadequacy, we rationally designed and synthesized a series of emixustat derivatives with strategically placed fluorine and deuterium atoms to slow down the key metabolic transformations known for emixustat. Crystal structures and quantum chemical analysis of RPE65 in complex with the most potent emixustat derivatives revealed the structural and electronic bases for how fluoro substituents can be favorably accommodated within the active site pocket of RPE65. We found a close (∼3.0 Å) F-π interaction that is predicted to contribute ∼2.4 kcal/mol to the overall binding energy.
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Affiliation(s)
- Eliav Blum
- Department of Chemistry, Faculty of Exact Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Jianye Zhang
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, California 92697, United States
| | - Jordan Zaluski
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - David E Einstein
- Department of Physiology and Biophysics, University of California, Irvine, California 92697, United States.,Research Service, VA Long Beach Healthcare System, Long Beach, California 90822, United States
| | - Edward E Korshin
- Department of Chemistry, Faculty of Exact Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Adam Kubas
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw 01-224, Poland
| | - Arie Gruzman
- Department of Chemistry, Faculty of Exact Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Gregory P Tochtrop
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Philip D Kiser
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, California 92697, United States.,Department of Physiology and Biophysics, University of California, Irvine, California 92697, United States.,Research Service, VA Long Beach Healthcare System, Long Beach, California 90822, United States
| | - Krzysztof Palczewski
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, California 92697, United States.,Department of Physiology and Biophysics, University of California, Irvine, California 92697, United States.,Department of Chemistry, University of California, Irvine, California 92697, United States
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4
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Comparison of Inhibitor and Substrate Selectivity between Rodent and Human Vascular Adhesion Protein-1. Mediators Inflamm 2020; 2020:3270513. [PMID: 32410850 PMCID: PMC7201828 DOI: 10.1155/2020/3270513] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 11/27/2019] [Accepted: 12/20/2019] [Indexed: 11/18/2022] Open
Abstract
Vascular adhesion protein-1 (VAP-1) is an ectoenzyme that functions as a copper-containing amine oxidase and is involved in leukocyte adhesion at sites of inflammation. Inhibition of VAP-1 oxidative deamination has become an attractive target for anti-inflammatory therapy with demonstrated efficacy in rodent models of inflammation. A previous comparison of purified recombinant VAP-1 from mouse, rat, monkey, and human gene sequences predicted that rodent VAP-1 would have higher affinity for smaller hydrophilic substrates/inhibitors because of its narrower and more hydrophilic active site channel. An optimized in vitro oxidative deamination fluorescence assay with benzylamine (BA) was used to compare inhibition of five known inhibitors in recombinant mouse, rat, and human VAP-1. Human VAP-1 was more sensitive compared to rat or mouse VAP-1 (lowest IC50 concentration) to semicarbazide but was least sensitive to hydralazine and LJP-1207. Hydralazine had a lower IC50 in rats compared to humans, although not significant. However, the IC50 of hydralazine was significantly higher in the rat compared to mouse VAP-1. The larger hydrophobic compounds from Astellas (compound 35c) and Boehringer Ingelheim (PXS-4728A) were hypothesized to have higher binding affinity for human VAP-1 compared to rodent VAP-1 since the channel in human VAP-1 is larger and more hydrophobic than that in rodent VAP-1. Although the sensitivity of these two inhibitors was the lowest in the mouse enzyme, we found no significant differences between mouse, rat, and human VAP-1. Michaelis-Menten kinetics of the small primary amines phenylethylamine and tyramine were also compared to the common marker substrate BA demonstrating that BA had the highest affinity among the substrates. Rat VAP-1 had the highest affinity for all three substrates and mouse VAP-1 had intermediate affinity for BA and phenylethylamine, but tyramine was not a substrate for mouse VAP-1 under these assay conditions. These results suggest that comparing oxidative deamination in mouse and rat VAP-1 may be important if using these species for preclinical efficacy models.
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5
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Vakal S, Jalkanen S, Dahlström KM, Salminen TA. Human Copper-Containing Amine Oxidases in Drug Design and Development. Molecules 2020; 25:E1293. [PMID: 32178384 PMCID: PMC7144023 DOI: 10.3390/molecules25061293] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 03/06/2020] [Accepted: 03/10/2020] [Indexed: 12/28/2022] Open
Abstract
Two members of the copper-containing amine oxidase family are physiologically important proteins: (1) Diamine oxidase (hDAO; AOC1) with a preference for diamines is involved in degradation of histamine and (2) Vascular adhesion protein-1 (hVAP-1; AOC3) with a preference for monoamines is a multifunctional cell-surface receptor and an enzyme. hVAP-1-targeted inhibitors are designed to treat inflammatory diseases and cancer, whereas the off-target binding of the designed inhibitors to hDAO might result in adverse drug reactions. The X-ray structures for both human enzymes are solved and provide the basis for computer-aided inhibitor design, which has been reported by several research groups. Although the putative off-target effect of hDAO is less studied, computational methods could be easily utilized to avoid the binding of VAP-1-targeted inhibitors to hDAO. The choice of the model organism for preclinical testing of hVAP-1 inhibitors is not either trivial due to species-specific binding properties of designed inhibitors and different repertoire of copper-containing amine oxidase family members in mammalian species. Thus, the facts that should be considered in hVAP-1-targeted inhibitor design are discussed in light of the applied structural bioinformatics and structural biology approaches.
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Affiliation(s)
- Serhii Vakal
- Structural Bioinformatics Laboratory, Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Tykistökatu 6A, FI-20520 Turku, Finland; (S.V.); (K.M.D.)
| | - Sirpa Jalkanen
- MediCity Research Laboratory, University of Turku, Tykistökatu 6A, FI-20520 Turku, Finland;
| | - Käthe M. Dahlström
- Structural Bioinformatics Laboratory, Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Tykistökatu 6A, FI-20520 Turku, Finland; (S.V.); (K.M.D.)
| | - Tiina A. Salminen
- Structural Bioinformatics Laboratory, Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Tykistökatu 6A, FI-20520 Turku, Finland; (S.V.); (K.M.D.)
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6
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Reid MJ, Eyre R, Podoll T. Oxidative Deamination of Emixustat by Human Vascular Adhesion Protein-1/Semicarbazide-Sensitive Amine Oxidase. Drug Metab Dispos 2019; 47:504-515. [PMID: 30787099 DOI: 10.1124/dmd.118.085811] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Accepted: 01/28/2019] [Indexed: 12/25/2022] Open
Abstract
Emixustat potently inhibits the visual cycle isomerase retinal pigment epithelium protein 65 (RPE65) to reduce the accumulation of toxic bisretinoid by-products that lead to various retinopathies. Orally administered emixustat is cleared rapidly from the plasma, with little excreted unchanged. The hydroxypropylamine moiety that is critical in emixustat's inhibition of RPE65 is oxidatively deaminated to three major carboxylic acid metabolites that appear rapidly in plasma. These metabolites greatly exceed the plasma concentrations of emixustat and demonstrate formation-rate-limited metabolite kinetics. This study investigated in vitro deamination of emixustat in human vascular membrane fractions, plasma, and recombinant human vascular adhesion protein-1 (VAP-1), demonstrating single-enzyme kinetics for the formation of a stable aldehyde intermediate (ACU-5201) in all in vitro systems. The in vitro systems used herein established sequential formation of the major metabolites with addition of assay components for aldehyde dehydrogenase and cytochrome P450. Reaction phenotyping experiments using selective chemical inhibitors and recombinant enzymes of monoamine oxidase, VAP-1, and lysyl oxidase showed that only VAP-1 deaminated emixustat. In individually derived human vascular membranes from umbilical cord and aorta, rates of emixustat deamination were highly correlated to VAP-1 marker substrate activity (benzylamine) and VAP-1 levels measured by enzyme-linked immunosorbent assay. In donor-matched plasma samples, soluble VAP-1 activity and levels were lower than in aorta membranes. A variety of potential comedications did not strongly inhibit emixustat deamination in vitro.
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Affiliation(s)
- Michael J Reid
- Acucela Inc., Seattle, Washington (M.J.R.); MavuPharma, Kirkland, Washington (R.E.); and IV-PO, LLC, Seattle, Washington (T.P.)
| | - Russell Eyre
- Acucela Inc., Seattle, Washington (M.J.R.); MavuPharma, Kirkland, Washington (R.E.); and IV-PO, LLC, Seattle, Washington (T.P.)
| | - Terry Podoll
- Acucela Inc., Seattle, Washington (M.J.R.); MavuPharma, Kirkland, Washington (R.E.); and IV-PO, LLC, Seattle, Washington (T.P.)
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7
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Abstract
Significance: Vascular adhesion protein-1 (VAP-1) is an ectoenzyme that oxidates primary amines in a reaction producing also hydrogen peroxide. VAP-1 on the blood vessel endothelium regulates leukocyte extravasation from the blood into tissues under physiological and pathological conditions. Recent Advances: Inhibition of VAP-1 by neutralizing antibodies and by several novel small-molecule enzyme inhibitors interferes with leukocyte trafficking and alleviates inflammation in many experimental models. Targeting of VAP-1 also shows beneficial effects in several other diseases, such as ischemia/reperfusion, fibrosis, and cancer. Moreover, soluble VAP-1 levels may serve as a new prognostic biomarker in selected diseases. Critical Issues: Understanding the contribution of the enzyme activity-independent and enzyme activity-dependent functions, which often appear to be mediated by the hydrogen peroxide production, in the VAP-1 biology will be crucial. Similarly, there is a pressing need to understand which of the VAP-1 functions are regulated through the modulation of leukocyte trafficking, and what is the role of VAP-1 synthesized in adipose and smooth muscle cells. Future Directions: The specificity and selectivity of new VAP-1 inhibitors, and their value in animal models under therapeutic settings need to be addressed. Results from several programs studying the therapeutic potential of VAP-1 inhibition, which now are in clinical trials, will reveal the relevance of this amine oxidase in humans.
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Affiliation(s)
- Marko Salmi
- 1 MediCity , Turku, Finland .,2 Institute of Biomedicine, University of Turku, Turku, Finland
| | - Sirpa Jalkanen
- 1 MediCity , Turku, Finland .,2 Institute of Biomedicine, University of Turku, Turku, Finland
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8
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Moon HJ, Finney J, Ronnebaum T, Mure M. Human lysyl oxidase-like 2. Bioorg Chem 2014; 57:231-241. [PMID: 25146937 DOI: 10.1016/j.bioorg.2014.07.003] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 07/10/2014] [Accepted: 07/14/2014] [Indexed: 12/31/2022]
Abstract
Lysyl oxidase like-2 (LOXL2) belongs to the lysyl oxidase (LOX) family, which comprises Cu(2+)- and lysine tyrosylquinone (LTQ)-dependent amine oxidases. LOXL2 is proposed to function similarly to LOX in the extracellular matrix (ECM) by promoting crosslinking of collagen and elastin. LOXL2 has also been proposed to regulate extracellular and intracellular cell signaling pathways. Dysregulation of LOXL2 has been linked to many diseases, including cancer, pro-oncogenic angiogenesis, fibrosis and heart diseases. In this review, we will give an overview of the current understandings and hypotheses regarding the molecular functions of LOXL2.
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Affiliation(s)
- Hee-Jung Moon
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA
| | - Joel Finney
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA
| | - Trey Ronnebaum
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA
| | - Minae Mure
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA.
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9
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Finney J, Moon HJ, Ronnebaum T, Lantz M, Mure M. Human copper-dependent amine oxidases. Arch Biochem Biophys 2014; 546:19-32. [PMID: 24407025 DOI: 10.1016/j.abb.2013.12.022] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 12/24/2013] [Accepted: 12/26/2013] [Indexed: 12/11/2022]
Abstract
Copper amine oxidases (CAOs) are a class of enzymes that contain Cu(2+) and a tyrosine-derived quinone cofactor, catalyze the conversion of a primary amine functional group to an aldehyde, and generate hydrogen peroxide and ammonia as byproducts. These enzymes can be classified into two non-homologous families: 2,4,5-trihydroxyphenylalanine quinone (TPQ)-dependent CAOs and the lysine tyrosylquinone (LTQ)-dependent lysyl oxidase (LOX) family of proteins. In this review, we will focus on recent developments in the field of research concerning human CAOs and the LOX family of proteins. The aberrant expression of these enzymes is linked to inflammation, fibrosis, tumor metastasis/invasion and other diseases. Consequently, there is a critical need to understand the functions of these proteins at the molecular level, so that strategies targeting these enzymes can be developed to combat human diseases.
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Affiliation(s)
- Joel Finney
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA
| | - Hee-Jung Moon
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA
| | - Trey Ronnebaum
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA
| | - Mason Lantz
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA
| | - Minae Mure
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA.
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10
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Liu Y, Mukherjee A, Nahumi N, Ozbil M, Brown D, Angeles-Boza AM, Dooley DM, Prabhakar R, Roth JP. Experimental and Computational Evidence of Metal-O2 Activation and Rate-Limiting Proton-Coupled Electron Transfer in a Copper Amine Oxidase. J Phys Chem B 2012; 117:218-29. [DOI: 10.1021/jp3121484] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Yi Liu
- Department of Chemistry, Johns Hopkins University, 3400 North
Charles Street, Baltimore, Maryland 21218, United States
| | - Arnab Mukherjee
- Department of Chemistry, Johns Hopkins University, 3400 North
Charles Street, Baltimore, Maryland 21218, United States
| | - Nadav Nahumi
- Department of Chemistry, Johns Hopkins University, 3400 North
Charles Street, Baltimore, Maryland 21218, United States
| | - Mehmet Ozbil
- Department of Chemistry, University of Miami, 1301 Memorial Drive,
Coral Gables, Florida 33146, United States
| | - Doreen Brown
- Department of Chemistry
and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Alfredo M. Angeles-Boza
- Department of Chemistry, Johns Hopkins University, 3400 North
Charles Street, Baltimore, Maryland 21218, United States
| | - David M. Dooley
- Department of Chemistry
and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Rajeev Prabhakar
- Department of Chemistry, University of Miami, 1301 Memorial Drive,
Coral Gables, Florida 33146, United States
| | - Justine P. Roth
- Department of Chemistry, Johns Hopkins University, 3400 North
Charles Street, Baltimore, Maryland 21218, United States
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11
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Heuts DPHM, Weissenborn MJ, Olkhov RV, Shaw AM, Gummadova J, Levy C, Scrutton NS. Crystal structure of a soluble form of human CD73 with ecto-5'-nucleotidase activity. Chembiochem 2012; 13:2384-91. [PMID: 22997138 DOI: 10.1002/cbic.201200426] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Indexed: 01/14/2023]
Abstract
CD73 is a dimeric ecto-5'-nucleotidase that is expressed on the exterior side of the plasma membrane. CD73 has important regulatory functions in the extracellular metabolism of certain nucleoside monophosphates, in particular adenosine monophosphate, and has been linked to a number of pathological conditions such as cancer and myocardial ischaemia. Here, we present the crystal structure of a soluble form of human soluble CD73 (sCD73) at 2.2 Å resolution, a truncated form of CD73 that retains ecto-5'-nucleotidase activity. With this structure we obtained insight into the dimerisation of CD73, active site architecture, and a sense of secondary modifications of the protein. The crystal structure reveals a conserved loop that is directly involved in the dimer-dimer interaction showing that the two subunits of the dimer are not linked by disulfide bridges. Using biophotonic microarray imaging we were able to confirm glycosylation of the enzyme and show that the enzyme is decorated with a variety of oligosaccharide structures. The crystal structure of sCD73 will aid the design of inhibitors or activator molecules for the treatment of several diseases and prove useful in explaining the possible roles of single nucleotide polymorphisms in physiology and disease.
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Affiliation(s)
- Dominic P H M Heuts
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK
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12
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Shen SH, Wertz DL, Klinman JP. Implication for functions of the ectopic adipocyte copper amine oxidase (AOC3) from purified enzyme and cell-based kinetic studies. PLoS One 2012; 7:e29270. [PMID: 22238597 PMCID: PMC3251558 DOI: 10.1371/journal.pone.0029270] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Accepted: 11/23/2011] [Indexed: 12/23/2022] Open
Abstract
AOC3 is highly expressed in adipocytes and smooth muscle cells, but its function in these cells is currently unknown. The in vivo substrate(s) of AOC3 is/are also unknown, but could provide an invaluable clue to the enzyme's function. Expression of untagged, soluble human AOC3 in insect cells provides a relatively simple means of obtaining pure enzyme. Characterization of enzyme indicates a 6% titer for the active site 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor and corrected k(cat) values as high as 7 s(-1). Substrate kinetic profiling shows that the enzyme accepts a variety of primary amines with different chemical features, including nonphysiological branched-chain and aliphatic amines, with measured k(cat)/K(m) values between 10(2) and 10(4) M(-1) s(-1). K(m)(O(2)) approximates the partial pressure of oxygen found in the interstitial space. Comparison of the properties of purified murine to human enzyme indicates k(cat)/K(m) values that are within 3 to 4-fold, with the exception of methylamine and aminoacetone that are ca. 10-fold more active with human AOC3. With drug development efforts investigating AOC3 as an anti-inflammatory target, these studies suggest that caution is called for when screening the efficacy of inhibitors designed against human enzymes in non-transgenic mouse models. Differentiated murine 3T3-L1 adipocytes show a uniform distribution of AOC3 on the cell surface and whole cell K(m) values that are reasonably close to values measured using purified enzymes. The latter studies support a relevance of the kinetic parameters measured with isolated AOC3 variants to adipocyte function. From our studies, a number of possible substrates with relatively high k(cat)/K(m) have been discovered, including dopamine and cysteamine, which may implicate a role for adipocyte AOC3 in insulin-signaling and fatty acid metabolism, respectively. Finally, the demonstrated AOC3 turnover of primary amines that are non-native to human tissue suggests possible roles for the adipocyte enzyme in subcutaneous bacterial infiltration and obesity.
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Affiliation(s)
- Sam H. Shen
- Department of Chemistry, University of California, Berkeley, California, United States of America
| | - Diana L. Wertz
- Department of Chemistry, University of California, Berkeley, California, United States of America
| | - Judith P. Klinman
- Department of Chemistry, University of California, Berkeley, California, United States of America
- Department of Molecular and Cell Biology and the California Institute for Quantitative Biosciences, University of California, Berkeley, California, United States of America
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