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Desta IT, Kotelnikov S, Jones G, Ghani U, Abyzov M, Kholodov Y, Standley DM, Beglov D, Vajda S, Kozakov D. The ClusPro AbEMap web server for the prediction of antibody epitopes. Nat Protoc 2023; 18:1814-1840. [PMID: 37188806 PMCID: PMC10898366 DOI: 10.1038/s41596-023-00826-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Accepted: 01/19/2023] [Indexed: 05/17/2023]
Abstract
Antibodies play an important role in the immune system by binding to molecules called antigens at their respective epitopes. These interfaces or epitopes are structural entities determined by the interactions between an antibody and an antigen, making them ideal systems to analyze by using docking programs. Since the advent of high-throughput antibody sequencing, the ability to perform epitope mapping using only the sequence of the antibody has become a high priority. ClusPro, a leading protein-protein docking server, together with its template-based modeling version, ClusPro-TBM, have been re-purposed to map epitopes for specific antibody-antigen interactions by using the Antibody Epitope Mapping server (AbEMap). ClusPro-AbEMap offers three different modes for users depending on the information available on the antibody as follows: (i) X-ray structure, (ii) computational/predicted model of the structure or (iii) only the amino acid sequence. The AbEMap server presents a likelihood score for each antigen residue of being part of the epitope. We provide detailed information on the server's capabilities for the three options and discuss how to obtain the best results. In light of the recent introduction of AlphaFold2 (AF2), we also show how one of the modes allows users to use their AF2-generated antibody models as input. The protocol describes the relative advantages of the server compared to other epitope-mapping tools, its limitations and potential areas of improvement. The server may take 45-90 min depending on the size of the proteins.
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Affiliation(s)
- Israel T Desta
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Sergei Kotelnikov
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY, USA
| | - George Jones
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY, USA
| | - Usman Ghani
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | | | | | - Daron M Standley
- Department of Genome Informatics, Osaka University, Osaka, Japan
- Center for Infectious Disease Education and Research, Osaka University, Osaka, Japan
| | - Dmitri Beglov
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Sandor Vajda
- Department of Biomedical Engineering, Boston University, Boston, MA, USA.
| | - Dima Kozakov
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY, USA.
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Desta IT, Kotelnikov S, Jones G, Ghani U, Abyzov M, Kholodov Y, Standley DM, Sabitova M, Beglov D, Vajda S, Kozakov D. Mapping of antibody epitopes based on docking and homology modeling. Proteins 2023; 91:171-182. [PMID: 36088633 PMCID: PMC9822860 DOI: 10.1002/prot.26420] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 08/25/2022] [Accepted: 09/06/2022] [Indexed: 01/11/2023]
Abstract
Antibodies are key proteins produced by the immune system to target pathogen proteins termed antigens via specific binding to surface regions called epitopes. Given an antigen and the sequence of an antibody the knowledge of the epitope is critical for the discovery and development of antibody based therapeutics. In this work, we present a computational protocol that uses template-based modeling and docking to predict epitope residues. This protocol is implemented in three major steps. First, a template-based modeling approach is used to build the antibody structures. We tested several options, including generation of models using AlphaFold2. Second, each antibody model is docked to the antigen using the fast Fourier transform (FFT) based docking program PIPER. Attention is given to optimally selecting the docking energy parameters depending on the input data. In particular, the van der Waals energy terms are reduced for modeled antibodies relative to x-ray structures. Finally, ranking of antigen surface residues is produced. The ranking relies on the docking results, that is, how often the residue appears in the docking poses' interface, and also on the energy favorability of the docking pose in question. The method, called PIPER-Map, has been tested on a widely used antibody-antigen docking benchmark. The results show that PIPER-Map improves upon the existing epitope prediction methods. An interesting observation is that epitope prediction accuracy starting from antibody sequence alone does not significantly differ from that of starting from unbound (i.e., separately crystallized) antibody structure.
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Affiliation(s)
- Israel T. Desta
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
| | - Sergei Kotelnikov
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY 11794, USA
| | - George Jones
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY 11794, USA
| | - Usman Ghani
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
| | | | | | - Daron M. Standley
- Department of Genome Informatics, Osaka University, Osaka, 565-0871, Japan
- Center for Infectious Disease Education and Research, Osaka University, Osaka, 565-0871, Japan
| | - Maria Sabitova
- Department of Mathematics, CUNY Queens College, Flushing, NY 11367, USA
| | - Dmitri Beglov
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
| | - Sandor Vajda
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
| | - Dima Kozakov
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY 11794, USA
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Popova IA, Lubbe L, Petukhov PA, Kalantarov GF, Trakht IN, Chernykh ER, Leplina OY, Lyubimov AV, Garcia JGN, Dudek SM, Sturrock ED, Danilov SM. Epitope mapping of novel monoclonal antibodies to human angiotensin I-converting enzyme. Protein Sci 2021; 30:1577-1593. [PMID: 33931897 DOI: 10.1002/pro.4091] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Revised: 04/16/2021] [Accepted: 04/23/2021] [Indexed: 12/19/2022]
Abstract
Angiotensin I-converting enzyme (ACE, CD143) plays a crucial role in blood pressure regulation, vascular remodeling, and immunity. A wide spectrum of mAbs to different epitopes on the N and C domains of human ACE have been generated and used to study different aspects of ACE biology, including establishing a novel approach-conformational fingerprinting. Here we characterized a novel set of 14 mAbs, developed against human seminal fluid ACE. The epitopes for these novel mAbs were defined using recombinant ACE constructs with truncated N and C domains, species cross-reactivity, ACE mutagenesis, and competition with the previously mapped anti-ACE mAbs. Nine mAbs recognized regions on the N domain, and 5 mAbs-on the C domain of ACE. The epitopes for most of these novel mAbs partially overlap with epitopes mapped onto ACE by the previously generated mAbs, whereas mAb 8H1 recognized yet unmapped region on the C domain where three ACE mutations associated with Alzheimer's disease are localized and is a marker for ACE mutation T877M. mAb 2H4 could be considered as a specific marker for ACE in dendritic cells. This novel set of mAbs can identify even subtle changes in human ACE conformation caused by tissue-specific glycosylation of ACE or mutations, and can detect human somatic and testicular ACE in biological fluids and tissues. Furthermore, the high reactivity of these novel mAbs provides an opportunity to study changes in the pattern of ACE expression or glycosylation in different tissues, cells, and diseases, such as sarcoidosis and Alzheimer's disease.
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Affiliation(s)
- Isolda A Popova
- Recombinant Protein Production Core (rPPC), Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA
| | - Lizelle Lubbe
- Department of Integrative Biomedical Sciences, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Pavel A Petukhov
- School of Pharmacy, University of Illinois, Chicago, Illinois, USA
| | | | - Ilya N Trakht
- Department of Medicine, Columbia University, New York, New York, USA
| | - Elena R Chernykh
- Laboratory of Cellular Immunotherapy, Institute of Fundamental and Clinical Immunology, Novosibirsk, Russia
| | - Olga Y Leplina
- Laboratory of Cellular Immunotherapy, Institute of Fundamental and Clinical Immunology, Novosibirsk, Russia
| | - Alex V Lyubimov
- Toxicology Research Laboratory, University of Illinois, Chicago, Illinois, USA
| | - Joe G N Garcia
- Department of Medicine, University of Arizona, Tucson, Arizona, USA
| | - Steven M Dudek
- Division of Pulmonary, Critical Care, Sleep and Allergy, Department of Medicine, University of Illinois, Chicago, Illinois, USA
| | - Edward D Sturrock
- Department of Integrative Biomedical Sciences, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Sergei M Danilov
- Department of Medicine, University of Arizona, Tucson, Arizona, USA.,Division of Pulmonary, Critical Care, Sleep and Allergy, Department of Medicine, University of Illinois, Chicago, Illinois, USA.,Medical Center, Moscow University, Moscow, Russia
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Abstract
Background Pulmonary vascular endothelium is the main metabolic site for Angiotensin I-Converting Enzyme (ACE)-mediated degradation of several biologically-active peptides (angiotensin I, bradykinin, hemo-regulatory peptide Ac-SDKP). Primary lung cancer growth and lung cancer metastases decrease lung vascularity reflected by dramatic decreases in both lung and serum ACE activity. We performed precise ACE phenotyping in tissues from subjects with lung cancer. Methodology ACE phenotyping included: 1) ACE immunohistochemistry with specific and well-characterized monoclonal antibodies (mAbs) to ACE; 2) ACE activity measurement with two ACE substrates (HHL, ZPHL); 3) calculation of ACE substrates hydrolysis ratio (ZPHL/HHL ratio); 4) the pattern of mAbs binding to 17 different ACE epitopes to detect changes in ACE conformation induced by tumor growth (conformational ACE fingerprint). Results ACE immunostaining was dramatically decreased in lung cancer tissues confirmed by a 3-fold decrease in ACE activity. The conformational fingerprint of ACE from tumor lung tissues differed from normal lung (6/17 mAbs) and reflected primarily higher ACE sialylation. The increase in ZPHL/HHL ratio in lung cancer tissues was consistent with greater conformational changes of ACE. Limited analysis of the conformational ACE fingerprint in normal lung tissue and lung cancer tissue form the same patient suggested a remote effect of tumor tissue on ACE conformation and/or on “field cancerization” in a morphologically-normal lung tissues. Conclusions/Significance Local conformation of ACE is significantly altered in tumor lung tissues and may be detected by conformational fingerprinting of human ACE.
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Lubbe L, Sturrock ED. Interacting cogs in the machinery of the renin angiotensin system. Biophys Rev 2019; 11:583-589. [PMID: 31177382 PMCID: PMC6682192 DOI: 10.1007/s12551-019-00555-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 05/29/2019] [Indexed: 01/19/2023] Open
Abstract
Somatic angiotensin converting enzyme (sACE) is well-known for its role in blood pressure regulation and consequently, ACE inhibitors are widely prescribed for the treatment of hypertension. More than 60 years after the discovery of sACE, however, the molecular details of its substrate hydrolysis and inhibition are still poorly understood. Isothermal titration calorimetry, molecular dynamics simulations and fine epitope mapping suggest that substrate or inhibitor binding triggers a hinging motion between the two subdomains of each domain. Ligand binding to one domain further induces a conformational change in sACE to negatively affect the second domain's function and can also cause dimerization between sACE molecules. This has been linked to an increase in sACE expression via intracellular signalling. Inhibitor-induced dimerization could thus decrease the efficacy of hypertension treatment. At present, the only structural information available for sACE are crystal structures of the truncated domains in the closed conformation due to the presence of ligands. These structures do not provide any information regarding the open active site conformation prior to ligand binding, the relative orientation of the two domains in full-length sACE, or the dimerization interface. To guarantee effective therapeutic intervention, further research is required to investigate the hinging, negative cooperativity and dimerization of sACE. This review describes our current understanding of these interactions and proposes how recent advances in cryo-electron microscopy could enable structural elucidation of their mechanisms.
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Affiliation(s)
- Lizelle Lubbe
- Department of Integrative Biomedical Sciences, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, Cape Town, 7925, South Africa
| | - Edward D Sturrock
- Department of Integrative Biomedical Sciences, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, Cape Town, 7925, South Africa.
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Danilov SM, Tikhomirova VE, Metzger R, Naperova IA, Bukina TM, Goker-Alpan O, Tayebi N, Gayfullin NM, Schwartz DE, Samokhodskaya LM, Kost OA, Sidransky E. ACE phenotyping in Gaucher disease. Mol Genet Metab 2018; 123:501-510. [PMID: 29478818 PMCID: PMC5891352 DOI: 10.1016/j.ymgme.2018.02.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 02/13/2018] [Indexed: 11/24/2022]
Abstract
BACKGROUND Gaucher disease is characterized by the activation of splenic and hepatic macrophages, accompanied by dramatically increased levels of angiotensin-converting enzyme (ACE). To evaluate the source of the elevated blood ACE, we performed complete ACE phenotyping using blood, spleen and liver samples from patients with Gaucher disease and controls. METHODS ACE phenotyping included 1) immunohistochemical staining for ACE; 2) measuring ACE activity with two substrates (HHL and ZPHL); 3) calculating the ratio of the rates of substrate hydrolysis (ZPHL/HHL ratio); 4) assessing the conformational fingerprint of ACE by evaluating the pattern of binding of monoclonal antibodies to 16 different ACE epitopes. RESULTS We show that in patients with Gaucher disease, the dramatically increased levels of ACE originate from activated splenic and/or hepatic macrophages (Gaucher cells), and that both its conformational fingerprint and kinetic characteristics (ZPHL/HHL ratio) differ from controls and from patients with sarcoid granulomas. Furthermore, normal spleen was found to produce high levels of endogenous ACE inhibitors and a novel, tightly-bound 10-30 kDa ACE effector which is deficient in Gaucher spleen. CONCLUSIONS The conformation of ACE is tissue-specific. In Gaucher disease, ACE produced by activated splenic macrophages differs from that in hepatic macrophages, as well as from macrophages and dendritic cells in sarcoid granulomas. The observed differences are likely due to altered ACE glycosylation or sialylation in these diseased organs. The conformational differences in ACE may serve as a specific biomarker for Gaucher disease.
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Affiliation(s)
- Sergei M Danilov
- Department of Anesthesiology, University of Illinois at Chicago, IL, USA; Department of Medicine, University of Arizona, Tucson, AZ, USA.
| | | | - Roman Metzger
- Department of Pediatric and Adolescent Surgery, Paracelsus Medical University, Salzburg, Austria
| | - Irina A Naperova
- Department of Chemistry, Lomonosov Moscow State University, Russia
| | | | - Ozlem Goker-Alpan
- Section of Molecular Neurogenetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - Nahid Tayebi
- Section of Molecular Neurogenetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - Nurshat M Gayfullin
- Medical Center, Lomonosov Moscow State University, Russia; Department of Fundamental Medicine, Lomonosov Moscow State University, Russia
| | - David E Schwartz
- Department of Anesthesiology, University of Illinois at Chicago, IL, USA
| | | | - Olga A Kost
- Department of Chemistry, Lomonosov Moscow State University, Russia
| | - Ellen Sidransky
- Section of Molecular Neurogenetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
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Kost OA, Tikhomirova VE, Kryukova OV, Gusakov AV, Bulaeva NI, Evdokimov VV, Golukhova EZ, Danilov SM. Conformational “Fingerprint” of the Angiotensin-Converting Enzyme. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2018. [DOI: 10.1134/s1068162018010107] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Efimov GA, Raats JMH, Chirivi RGS, van Rosmalen JWG, Nedospasov SA. Humanization of Murine Monoclonal anti-hTNF Antibody: The F10 Story. Mol Biol 2017. [DOI: 10.1134/s0026893317060061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Danilov SM. Conformational Fingerprinting Using Monoclonal Antibodies (on the Example of Angiotensin I-Converting Enzyme-ACE). Mol Biol 2017; 51:906-920. [PMID: 32287393 PMCID: PMC7102274 DOI: 10.1134/s0026893317060048] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Accepted: 06/02/2017] [Indexed: 11/22/2022]
Abstract
During the past 30 years my laboratory has generated 40+ monoclonal antibodies (mAbs) directed to structural and conformational epitopes on human ACE as well as ACE from rats, mice and other species. These mAbs were successfully used for detection and quantification of ACE by ELISA, Western blotting, flow cytometry and immunohistochemistry. In all these applications mainly single mAbs were used. We hypothesized that we can obtain a completely new kind of information about ACE structure and function if we use the whole set of mAbs directed to different epitopes on the ACE molecule. When we finished epitope mapping of all mAbs to ACE (and especially, those recognizing conformational epitopes), we realized that we had obtained a new tool to study ACE. First, we demonstrated that binding of some mAbs is very sensitive to local conformational changes on the ACE surface-due to local denaturation, inactivation, ACE inhibitor or mAbs binding or due to diseases. Second, we were able to detect, localize and characterize several human ACE mutations. And, finally, we established a new concept-conformational fingerprinting of ACE using mAbs that in turn allowed us to obtain evidence for tissue specificity of ACE, which has promising scientific and diagnostic perspectives. The initial goal for the generation of mAbs to ACE 30 years ago was obtaining mAbs to organ-specific endothelial cells, which could be used for organ-specific drug delivery. Our systematic work on characterization of mAbs to numerous epitopes on ACE during these years has lead not only to the generation of the most effective mAbs for specific drug/gene delivery into the lung capillaries, but also to the establishment of the concept of conformational fingerprinting of ACE, which in turn gives a theoretical base for the generation of mAbs, specific for ACE from different organs. We believe that this concept could be applicable for any glycoprotein against which there is a set of mAbs to different epitopes.
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Affiliation(s)
- S. M. Danilov
- University of Illinois at Chicago, Chicago, USA
- Arizona University, Tucson, USA
- Medical Scientific and Educational Center of Moscow State University, Moscow, 119991 Russia
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Danilov SM, Lünsdorf H, Akinbi HT, Nesterovitch AB, Epshtein Y, Letsiou E, Kryukova OV, Piegeler T, Golukhova EZ, Schwartz DE, Dull RO, Minshall RD, Kost OA, Garcia JGN. Lysozyme and bilirubin bind to ACE and regulate its conformation and shedding. Sci Rep 2016; 6:34913. [PMID: 27734897 PMCID: PMC5062130 DOI: 10.1038/srep34913] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 09/21/2016] [Indexed: 11/08/2022] Open
Abstract
Angiotensin I-converting enzyme (ACE) hydrolyzes numerous peptides and is a critical participant in blood pressure regulation and vascular remodeling. Elevated tissue ACE levels are associated with increased risk for cardiovascular and respiratory disorders. Blood ACE concentrations are determined by proteolytic cleavage of ACE from the endothelial cell surface, a process that remains incompletely understood. In this study, we identified a novel ACE gene mutation (Arg532Trp substitution in the N domain of somatic ACE) that increases blood ACE activity 7-fold and interrogated the mechanism by which this mutation significantly increases blood ACE levels. We hypothesized that this ACE mutation disrupts the binding site for blood components which may stabilize ACE conformation and diminish ACE shedding. We identified the ACE-binding protein in the blood as lysozyme and also a Low Molecular Weight (LMW) ACE effector, bilirubin, which act in concert to regulate ACE conformation and thereby influence ACE shedding. These results provide mechanistic insight into the elevated blood level of ACE observed in patients on ACE inhibitor therapy and elevated blood lysozyme and ACE levels in sarcoidosis patients.
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Affiliation(s)
- Sergei M. Danilov
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, IL, USA
- Institute for Personalized Respiratory Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Heinrich Lünsdorf
- Central Facility of Microscopy, Helmholtz-Center of Infection Research, Braunschweig, Germany
| | - Henry T. Akinbi
- Divisions of Pulmonary Biology and Neonatology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USA
| | | | - Yuliya Epshtein
- Institute for Personalized Respiratory Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Eleftheria Letsiou
- Institute for Personalized Respiratory Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Olga V. Kryukova
- Faculty of Chemistry, Lomonosov Moscow State University, Moscow, Russia
| | - Tobias Piegeler
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, IL, USA
- Institute of Anesthesiology, University Hospital Zurich, Zurich, Switzerland
| | | | - David E. Schwartz
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, IL, USA
| | - Randal O. Dull
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, IL, USA
| | - Richard D. Minshall
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, IL, USA
- Department of Pharmacology, University of Illinois at Chicago, Chicago, IL, USA
| | - Olga A. Kost
- Faculty of Chemistry, Lomonosov Moscow State University, Moscow, Russia
| | - Joe G. N. Garcia
- Institute for Personalized Respiratory Medicine, University of Illinois at Chicago, Chicago, IL, USA
- University of Arizona Health Sciences, Tucson, AZ, USA
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Kryukova OV, Tikhomirova VE, Golukhova EZ, Evdokimov VV, Kalantarov GF, Trakht IN, Schwartz DE, Dull RO, Gusakov AV, Uporov IV, Kost OA, Danilov SM. Tissue Specificity of Human Angiotensin I-Converting Enzyme. PLoS One 2015; 10:e0143455. [PMID: 26600189 PMCID: PMC4658169 DOI: 10.1371/journal.pone.0143455] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 11/04/2015] [Indexed: 12/18/2022] Open
Abstract
Background Angiotensin-converting enzyme (ACE), which metabolizes many peptides and plays a key role in blood pressure regulation and vascular remodeling, as well as in reproductive functions, is expressed as a type-1 membrane glycoprotein on the surface of endothelial and epithelial cells. ACE also presents as a soluble form in biological fluids, among which seminal fluid being the richest in ACE content - 50-fold more than that in blood. Methods/Principal Findings We performed conformational fingerprinting of lung and seminal fluid ACEs using a set of monoclonal antibodies (mAbs) to 17 epitopes of human ACE and determined the effects of potential ACE-binding partners on mAbs binding to these two different ACEs. Patterns of mAbs binding to ACEs from lung and from seminal fluid dramatically differed, which reflects difference in the local conformations of these ACEs, likely due to different patterns of ACE glycosylation in the lung endothelial cells and epithelial cells of epididymis/prostate (source of seminal fluid ACE), confirmed by mass-spectrometry of ACEs tryptic digests. Conclusions Dramatic differences in the local conformations of seminal fluid and lung ACEs, as well as the effects of ACE-binding partners on mAbs binding to these ACEs, suggest different regulation of ACE functions and shedding from epithelial cells in epididymis and prostate and endothelial cells of lung capillaries. The differences in local conformation of ACE could be the base for the generation of mAbs distingushing tissue-specific ACEs.
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Affiliation(s)
- Olga V. Kryukova
- Chemical Faculty, M.V.Lomonosov Moscow State University, Moscow, Russia
| | | | | | | | | | - Ilya N. Trakht
- Department of Medicine, Columbia University, New York, NY, United States of America
| | - David E. Schwartz
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Randal O. Dull
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, IL, United States of America
| | | | - Igor V. Uporov
- Chemical Faculty, M.V.Lomonosov Moscow State University, Moscow, Russia
| | - Olga A. Kost
- Chemical Faculty, M.V.Lomonosov Moscow State University, Moscow, Russia
- * E-mail: (SMD); (OAK)
| | - Sergei M. Danilov
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, IL, United States of America
- * E-mail: (SMD); (OAK)
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Kugaevskaya EV, Timoshenko OS, Solovyeva NI. [Angiotensin converting enzyme: the antigenic properties of the domain, role in Alzheimer's disease and tumor progression]. BIOMEDIT︠S︡INSKAI︠A︡ KHIMII︠A︡ 2015. [PMID: 26215407 DOI: 10.18097/pbmc20156103301] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Angiotensin converting enzyme (ACE, EC 3.4.15.1) was discovered and characterized in the Laboratory of biochemistry and chemical pathology of proteins under the direction of academician V.N. Orekhovich, where its physiological function, associated with a key role in the regulation of the renin-angiotensin (RAS) and the kallikrein-kinin systems that control blood flow in the body and homeostasis was first deciphered. We carried out a search for structural differences between the two highly homologous domains (N- and C-domains) of somatic ACE (sACE); it was based on a comparative analysis of antigenic determinants (or B-epitopes) of both domains. The revealed epitopes were classified with variable and conserved regions and functionally important sites of the molecule ACE. Essential difference was demonstrated between locations of the epitopes in the N- and C-domains. These data indicate the existence of structural differences between the domains of sACE. We studied the role of the domains of ACE in the metabolism of human amyloid beta peptide (Ab) - the main component of senile plaques, found in the brains of patients with Alzheimer's disease (AD). Our results demonstrated that only N-domain ACE cleaved the Ab between residues R5-H6, while, the C-domain of ACE failed to hydrolyze this region. In addition, the effect of post-translational modifications of Ab on its hydrolysis by the ACE was investigated. We show that isomerization of residue D7, a common non-enzymatic age-related modification found in AD-associated species, does not reduce the affinity of the peptide to the N-domain of ACE, and conversely, it increases. According to our data, the role of ACE in the metabolism of Ab becomes more significant in the development of AD. RAS is involved in malignant transformation and tumor progression. RAS components, including ACE and angiotensin II receptors type 1 (AT1R) are expressed in various human tumors. We found a significant increase in the level of ACE activity in the tumor tissue of squamous cell carcinoma of the cervix. In our viewpoint, the increase in ACE activity may be a marker of poor clinical prognosis.
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13
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Petrov MN, Shilo VY, Tarasov AV, Schwartz DE, Garcia JGN, Kost OA, Danilov SM. Conformational changes of blood ACE in chronic uremia. PLoS One 2012; 7:e49290. [PMID: 23166630 PMCID: PMC3500299 DOI: 10.1371/journal.pone.0049290] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Accepted: 10/08/2012] [Indexed: 11/30/2022] Open
Abstract
Background The pattern of binding of monoclonal antibodies (mAbs) to 16 epitopes on human angiotensin I-converting enzyme (ACE) comprise a conformational ACE fingerprint and is a sensitive marker of subtle protein conformational changes. Hypothesis Toxic substances in the blood of patients with uremia due to End Stage Renal Disease (ESRD) can induce local conformational changes in the ACE protein globule and alter the efficacy of ACE inhibitors. Methodology/Principal Findings The recognition of ACE by 16 mAbs to the epitopes on the N and C domains of ACE was estimated using an immune-capture enzymatic plate precipitation assay. The precipitation pattern of blood ACE by a set of mAbs was substantially influenced by the presence of ACE inhibitors with the most dramatic local conformational change noted in the N-domain region recognized by mAb 1G12. The “short” ACE inhibitor enalaprilat (tripeptide analog) and “long” inhibitor teprotide (nonapeptide) produced strikingly different mAb 1G12 binding with enalaprilat strongly increasing mAb 1G12 binding and teprotide decreasing binding. Reduction in S-S bonds via glutathione and dithiothreitol treatment increased 1G12 binding to blood ACE in a manner comparable to enalaprilat. Some patients with uremia due to ESRD exhibited significantly increased mAb 1G12 binding to blood ACE and increased ACE activity towards angiotensin I accompanied by reduced ACE inhibition by inhibitory mAbs and ACE inhibitors. Conclusions/Significance The estimation of relative mAb 1G12 binding to blood ACE detects a subpopulation of ESRD patients with conformationally changed ACE, which activity is less suppressible by ACE inhibitors. This parameter may potentially serve as a biomarker for those patients who may need higher concentrations of ACE inhibitors upon anti-hypertensive therapy.
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Affiliation(s)
- Maxim N. Petrov
- Department of Chemistry, Lomonosov Moscow State University, Moscow, Russia
| | - Valery Y. Shilo
- Department of Nephrology, Moscow University for Medicine and Dentistry, Moscow, Russia
| | | | - David E. Schwartz
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Joe G. N. Garcia
- Institute for Personalized Respiratory Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Olga A. Kost
- Department of Chemistry, Lomonosov Moscow State University, Moscow, Russia
| | - Sergei M. Danilov
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, Illinois, United States of America
- Institute for Personalized Respiratory Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
- National Cardiology Research Center, Moscow, Russia
- * E-mail:
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An angiotensin I-converting enzyme mutation (Y465D) causes a dramatic increase in blood ACE via accelerated ACE shedding. PLoS One 2011; 6:e25952. [PMID: 21998728 PMCID: PMC3187827 DOI: 10.1371/journal.pone.0025952] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 09/14/2011] [Indexed: 11/23/2022] Open
Abstract
Background Angiotensin I-converting enzyme (ACE) metabolizes a range of peptidic substrates and plays a key role in blood pressure regulation and vascular remodeling. Thus, elevated ACE levels may be associated with an increased risk for different cardiovascular or respiratory diseases. Previously, a striking familial elevation in blood ACE was explained by mutations in the ACE juxtamembrane region that enhanced the cleavage-secretion process. Recently, we found a family whose affected members had a 6-fold increase in blood ACE and a Tyr465Asp (Y465D) substitution, distal to the stalk region, in the N domain of ACE. Methodology/Principal Findings HEK and CHO cells expressing mutant (Tyr465Asp) ACE demonstrate a 3- and 8-fold increase, respectively, in the rate of ACE shedding compared to wild-type ACE. Conformational fingerprinting of mutant ACE demonstrated dramatic changes in ACE conformation in several different epitopes of ACE. Cell ELISA carried out on CHO-ACE cells also demonstrated significant changes in local ACE conformation, particularly proximal to the stalk region. However, the cleavage site of the mutant ACE - between Arg1203 and Ser1204 - was the same as that of WT ACE. The Y465D substitution is localized in the interface of the N-domain dimer (from the crystal structure) and abolishes a hydrogen bond between Tyr465 in one monomer and Asp462 in another. Conclusions/Significance The Y465D substitution results in dramatic increase in the rate of ACE shedding and is associated with significant local conformational changes in ACE. These changes could result in increased ACE dimerization and accessibility of the stalk region or the entire sACE, thus increasing the rate of cleavage by the putative ACE secretase (sheddase).
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15
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Danilov SM, Balyasnikova IV, Danilova AS, Naperova IA, Arablinskaya NE, Borisov SE, Metzger R, Franke FE, Schwartz DE, Gachok IV, Trakht IN, Kost OA, Garcia JGN. Conformational fingerprinting of the angiotensin I-converting enzyme (ACE). 1. Application in sarcoidosis. J Proteome Res 2010; 9:5782-93. [PMID: 20873814 DOI: 10.1021/pr100564r] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Fine epitope mapping of monoclonal antibodies (mAbs) to 16 epitopes on human angiotensin I-converting enzyme (ACE) revealed that the epitopes of all mAbs contained putative glycosylation sites. ACE glycosylation is both cell- and tissue-specific and, therefore, the local conformation of ACE produced by different cells could be also unique. The pattern of ACE binding by a set of mAbs to 16 epitopes of human ACE - "conformational fingerprint of ACE" - is the most sensitive marker of ACE conformation and could be cell- and tissue-specific. The recognition of ACEs by mAbs to ACE was estimated using an immune-capture enzymatic plate precipitation assay. Precipitation patterns of soluble recombinant ACE released from Chinese hamster ovary (CHO)-ACE cells was influenced by conditions that alter ACE glycosylation. This pattern was also strongly cell type specific. Patients with sarcoidosis exhibited conformational fingerprints of tissue ACE (lungs and lymph nodes), as well as blood ACE, which were distinct from controls. Conformational fingerprinting of ACE may detect ACE originated from the cells other than endothelial cells in the blood and when combined with elevated blood ACE levels in patients with sarcoidosis may potentially reflect extrapulmonary sarcoidosis involvement (bone marrow, spleen, liver). If proven true, this would serve as a biomarker of enormous potential clinical significance.
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Affiliation(s)
- Sergei M Danilov
- Department of Anesthesiology, University of Illinois, Chicago, IL, USA.
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16
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Angiotensin I-converting enzyme Gln1069Arg mutation impairs trafficking to the cell surface resulting in selective denaturation of the C-domain. PLoS One 2010; 5:e10438. [PMID: 20454656 PMCID: PMC2862704 DOI: 10.1371/journal.pone.0010438] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Accepted: 03/20/2010] [Indexed: 11/29/2022] Open
Abstract
Background Angiotensin-converting enzyme (ACE; Kininase II; CD143) hydrolyzes small peptides such as angiotensin I, bradykinin, substance P, LH-RH and several others and thus plays a key role in blood pressure regulation and vascular remodeling. Complete absence of ACE in humans leads to renal tubular dysgenesis (RTD), a severe disorder of renal tubule development characterized by persistent fetal anuria and perinatal death. Methodology/Principal Findings Patient with RTD in Lisbon, Portugal, maintained by peritoneal dialysis since birth, was found to have a homozygous substitution of Arg for Glu at position 1069 in the C-terminal domain of ACE (Q1069R) resulting in absence of plasma ACE activity; both parents and a brother who are heterozygous carriers of this mutation had exactly half-normal plasma ACE activity compared to healthy individuals. We hypothesized that the Q1069R substitution impaired ACE trafficking to the cell surface and led to accumulation of catalytically inactive ACE in the cell cytoplasm. CHO cells expressing wild-type (WT) vs. Q1069R-ACE demonstrated the mutant accumulates intracellularly and also that it is significantly degraded by intracellular proteases. Q1069R-ACE retained catalytic and immunological characteristics of WT-ACE N domain whereas it had 10–20% of the nativity of the WT-ACE C domain. A combination of chemical (sodium butyrate) or pharmacological (ACE inhibitor) chaperones with proteasome inhibitors (MG 132 or bortezomib) significantly restored trafficking of Q1069R-ACE to the cell surface and increased ACE activity in the cell culture media 4-fold. Conclusions/Significance Homozygous Q1069R substitution results in an ACE trafficking and processing defect which can be rescued, at least in cell culture, by a combination of chaperones and proteasome inhibitors. Further studies are required to determine whether similar treatment of individuals with this ACE mutation would provide therapeutic benefits such as concentration of primary urine.
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17
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Chen HL, Lünsdorf H, Hecht HJ, Tsai H. Porcine pulmonary angiotensin I-converting enzyme--biochemical characterization and spatial arrangement of the N- and C-domains by three-dimensional electron microscopic reconstruction. Micron 2010; 41:674-85. [PMID: 20427191 DOI: 10.1016/j.micron.2010.01.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The somatic angiotensin I-converting enzyme (sACE; peptidyl-dipeptidase A; EC 3.4.15.1) was isolated from pig lung and purified to homogeneity. The purified enzyme has a molecular mass of about 180 kDa. Upon proteolytic cleavage, two approximately 90 kDa fragments were obtained and identified by amino-terminal sequence analysis as the N- and C-domains of sACE. Both purified domains were shown to be catalytically active. A 2.3 nm resolution model of sACE was obtained by three-dimensional electron microscopic reconstruction of negatively stained sACE particles, based on atomic X-ray data fitting. Our model shows for the first time the relative orientation of the sACE catalytically active domains and their spatial distance.
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Affiliation(s)
- Hui-Ling Chen
- Development Center for Biotechnology, Taipei County 221, Taiwan, ROC
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18
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Nesterovitch AB, Hogarth KD, Adarichev VA, Vinokour EI, Schwartz DE, Solway J, Danilov SM. Angiotensin I-converting enzyme mutation (Trp1197Stop) causes a dramatic increase in blood ACE. PLoS One 2009; 4:e8282. [PMID: 20011602 PMCID: PMC2788243 DOI: 10.1371/journal.pone.0008282] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2009] [Accepted: 11/18/2009] [Indexed: 11/29/2022] Open
Abstract
Background Angiotensin-converting enzyme (ACE) metabolizes many peptides and plays a key role in blood pressure regulation and vascular remodeling. Elevated ACE levels may be associated with an increased risk for different cardiovascular or respiratory diseases, including asthma. Previously, a molecular mechanism underlying a 5-fold familial increase of blood ACE was discovered: Pro1199Leu substitution enhanced the cleavage-secretion process. Carriers of this mutation were Caucasians from Europe (mostly Dutch) or had European roots. Methodology/Principal Findings We have found a family of African-American descent whose affected members' blood ACE level was increased 13-fold over normal. In affected family members, codon TGG coding for Trp1197 was substituted in one allele by TGA (stop codon). As a result, half of ACE expressed in these individuals had a length of 1196 amino acids and lacked a transmembrane anchor. This ACE mutant is not trafficked to the cell membrane and is directly secreted out of cells; this mechanism apparently accounts for the high serum ACE level seen in affected individuals. A haplotype of the mutant ACE allele was determined based on 12 polymorphisms, which may help to identify other carriers of this mutation. Some but not all carriers of this mutation demonstrated airflow obstruction, and some but not all have hypertension. Conclusions/Significance We have identified a novel Trp1197Stop mutation that results in dramatic elevation of serum ACE. Since blood ACE elevation is often taken as a marker of disease activity (sarcoidosis and Gaucher diseases), it is important for clinicians and medical scientists to be aware of alternative genetic causes of elevated blood ACE that are not apparently linked to disease.
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Affiliation(s)
- Andrew B. Nesterovitch
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Kyle D. Hogarth
- Department of Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Vyacheslav A. Adarichev
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Elena I. Vinokour
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - David E. Schwartz
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Julian Solway
- Department of Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Sergei M. Danilov
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, Illinois, United States of America
- National Cardiology Research Center, Moscow, Russia
- * E-mail:
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19
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Gordon K, Balyasnikova IV, Nesterovitch AB, Schwartz DE, Sturrock ED, Danilov SM. Fine epitope mapping of monoclonal antibodies 9B9 and 3G8 to the N domain of angiotensin-converting enzyme (CD143) defines a region involved in regulating angiotensin-converting enzyme dimerization and shedding. ACTA ACUST UNITED AC 2009; 75:136-50. [PMID: 20003136 DOI: 10.1111/j.1399-0039.2009.01416.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
A panel of monoclonal antibodies (mAbs) raised against both the N and C domains of angiotensin-I-converting enzyme (ACE, peptidyl dipeptidase, EC 3.4.15.2) have been extensively mapped and have facilitated the study of various aspects of ACE structure and biology. In this study, we characterize two mAbs, 9B9 and 3G8, that recognize the N domain of ACE and that influence shedding and dimerization. Fine epitope mapping was performed, which mapped the epitopes for these mAbs to the N terminal region of the N domain where they overlap to a large extent, despite having different effects on ACE processing. The mAb 3G8 epitope appears to be shielded by the C domain and to be carbohydrate dependent as binding increased significantly as a result of underglycosylation, whereas these factors did not influence mAb 9B9 recognition. Three mutations within the overlapping region of these two epitopes, Q18H, L19E, and Q22A, which decreased mAb 3G8 binding to the soluble N domain, were introduced into full-length somatic ACE (sACE) to determine their influence on ACE expression and processing. Increased ACE expression, cell surface expression, and basal shedding were observed with all three mutations. Furthermore, cross-linking and western blotting of Chinese hamster ovary (CHO) cell lysates detected two distinct ACE dimers, a native and cross-linked dimer. Increasing amounts of the cross-linked dimer were observed for the mutant sACEQ22A, further implicating the overlapping region of the mAb 9B9 and 3G8 epitopes in ACE processing.
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Affiliation(s)
- K Gordon
- Division of Medical Biochemistry, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
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20
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Balyasnikova IV, Metzger R, Franke FE, Conrad N, Towbin H, Schwartz DE, Sturrock ED, Danilov SM. Epitope mapping of mAbs to denatured human testicular ACE (CD143). ACTA ACUST UNITED AC 2008; 72:354-68. [PMID: 18700874 DOI: 10.1111/j.1399-0039.2008.01112.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Angiotensin I-converting enzyme (ACE; CD143) has two homologous enzymatically active domains (N and C) and plays a crucial role in blood pressure regulation and vascular remodeling. A wide spectrum of monoclonal antibodies (mAbs) to different epitopes on the N and C domains of human ACE have been used to study different aspects of ACE biology. In this study, we characterized a set of nine mAbs, developed against the C domain of human ACE, which recognize the denatured forms of ACE and thus are suitable for the detection and quantification of somatic ACE (sACE) and testicular ACE (tACE) using Western blotting and immunohistochemistry on paraffin-embedded human tissues. The epitopes for these mAbs were defined using species cross-reactivity, phage display library screening, Western blotting and ACE mutagenesis. Most of the mAbs recognized common/overlapping region(s) on both somatic and testicular forms of human ACE, whereas mAb 4E10 was relatively specific for the testicular isoform and mAb 5B9 mainly recognized the glycan attached to Asn 731. This set of mAbs is useful for identifying even subtle changes in human ACE conformation because of denaturation. These mAbs are also sensitive tools for the detection of human sACE and tACE in biological fluids and tissues using proteomic approaches. Their high reactivity in paraffin-embedded tissues provides opportunities to study changes in the pattern of ACE expression and glycosylation (particularly with mAb 5B9) in different tissues and cells.
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Affiliation(s)
- I V Balyasnikova
- Department of Anesthesiology, University of Illinois at Chicago, Chicago, IL, USA
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21
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Naperova IA, Balyasnikova IV, Schwartz DE, Watermeyer J, Sturrock ED, Kost OA, Danilov SM. Mapping of conformational mAb epitopes to the C domain of human angiotensin I-converting enzyme. J Proteome Res 2008; 7:3396-411. [PMID: 18576678 DOI: 10.1021/pr800142w] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Angiotensin I-converting enzyme (ACE, CD143) has two homologous domains, each having a functional active site. Fine epitope mapping of 8 mAbs to the C-terminal domain of human ACE was carried out using plate precipitation assays, mAbs' cross-reactivity with ACE from different species, site-directed mutagenesis, and antigen- and cell-based ELISAs. Almost all epitopes contained potential glycosylation sites. Therefore, these mAbs could be used to distinguish different glycoforms of ACE expressed in different tissues or cell lines. mAbs 1B8 and 3F10 were especially sensitive to the composition of the N-glycan attached to Asn 731; mAbs 2H9 and 3F11 detected the glycosylation status of the glycan attached to Asn 685 and perhaps Asn1162; and mAb 1E10 and 4E3 recognized the glycan on Asn 666. The epitope of mAb 1E10 is located at the N-terminal end of the C domain, close to the unique 36 amino acid residues of testicular ACE (tACE). Moreover, it binds preferentially to tACE on the surface of human spermatozoa and thus may find application as an immunocontraceptive drug. mAb 4E3 was the best mAb for quantification of ACE-expressing somatic cells by flow cytometry. In contrast to the other mAbs, binding of mAb 2B11 was not markedly influenced by ACE glycosylation or by the cell culture conditions or cell types, making this mAb a suitable reference antibody. Epitope mapping of these C-domain mAbs, particularly those that compete with N-domain mAbs, enabled us to propose a model of the two-domain somatic ACE that might explain the interdomain cooperativity. Our findings demonstrated that mAbs directed to conformational epitopes on the C-terminal domain of human ACE are very useful for the detection of testicular and somatic ACE, quantification using flow cytometry and ELISA assays, and for the study of different aspects of ACE biology.
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Affiliation(s)
- Irina A Naperova
- Chemistry Faculty, Moscow State University, Russia, Department of Anesthesiology, University of Illinois at Chicago, Chicago, IL 60612, USA
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