1
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Denardo A, Ben Khlifa E, Bignotti M, Giuliani R, D'Acunto E, Miranda E, Irving JA, Fra A. Probing of the reactive center loop region of alpha-1-antitrypsin by mutagenesis predicts new type-2 dysfunctional variants. Cell Mol Life Sci 2023; 81:6. [PMID: 38087060 PMCID: PMC11073084 DOI: 10.1007/s00018-023-05059-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 10/25/2023] [Accepted: 11/22/2023] [Indexed: 12/18/2023]
Abstract
Lung disease in alpha-1-antitrypsin deficiency (AATD) mainly results from insufficient control of the serine proteases neutrophil elastase (NE) and proteinase-3 due to reduced plasma levels of alpha-1-antitrypsin (AAT) variants. Mutations in the specificity-determining reactive center loop (RCL) of AAT would be predicted to minimally affect protein folding and secretion by hepatocytes but can impair anti-protease activity or alter the target protease. These properly secreted but dysfunctional 'type-2' variants would not be identified by common diagnostic protocols that are predicated on a reduction in circulating AAT. This has potential clinical relevance: in addition to the dysfunctional Pittsburgh and Iners variants reported previously, several uncharacterized RCL variants are present in genome variation databases. To prospectively evaluate the impact of RCL variations on secretion and anti-protease activity, here we performed a systematic screening of amino acid substitutions occurring at the AAT-NE interface. Twenty-three AAT variants that can result from single nucleotide polymorphisms in this region, including 11 present in sequence variation databases, were expressed in a mammalian cell model. All demonstrated unaltered protein folding and secretion. However, when their ability to form stable complexes with NE was evaluated by western blot, enzymatic assays, and a novel ELISA developed to quantify AAT-NE complexes, substrate-like and NE-binding deficient dysfunctional variants were identified. This emphasizes the ability of the RCL to accommodate inactivating substitutions without impacting the integrity of the native molecule and demonstrates that this class of molecule violates a generally accepted paradigm that equates circulating levels with functional protection of lung tissue.
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Affiliation(s)
- Andrea Denardo
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Emna Ben Khlifa
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Mattia Bignotti
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Roberta Giuliani
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Emanuela D'Acunto
- Department of Biology and Biotechnologies 'Charles Darwin', Sapienza University of Rome, Rome, Italy
| | - Elena Miranda
- Department of Biology and Biotechnologies 'Charles Darwin', Sapienza University of Rome, Rome, Italy
| | - James A Irving
- UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, UK
| | - Annamaria Fra
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
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2
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Ryø LB, Haslund D, Rovsing AB, Pihl R, Sanrattana W, de Maat S, Palarasah Y, Maas C, Thiel S, Mikkelsen JG. Restriction of C1-inhibitor activity in hereditary angioedema by dominant-negative effects of disease-associated SERPING1 gene variants. J Allergy Clin Immunol 2023; 152:1218-1236.e9. [PMID: 37301409 DOI: 10.1016/j.jaci.2023.04.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 04/17/2023] [Accepted: 04/25/2023] [Indexed: 06/12/2023]
Abstract
BACKGROUND Patients with hereditary angioedema experience recurrent, sometimes life-threatening, attacks of edema. It is a rare genetic disorder characterized by genetic and clinical heterogenicity. Most cases are caused by genetic variants in the SERPING1 gene leading to plasma deficiency of the encoded protein C1 inhibitor (C1INH). More than 500 different hereditary angioedema-causing variants have been identified in the SERPING1 gene, but the disease mechanisms by which they result in pathologically low C1INH plasma levels remain largely unknown. OBJECTIVES The aim was to describe trans-inhibitory effects of full-length or near full-length C1INH encoded by 28 disease-associated SERPING1 variants. METHODS HeLa cells were transfected with expression constructs encoding the studied SERPING1 variants. Extensive and comparative studies of C1INH expression, secretion, functionality, and intracellular localization were carried out. RESULTS Our findings characterized functional properties of a subset of SERPING1 variants allowing the examined variants to be subdivided into 5 different clusters, each containing variants sharing specific molecular characteristics. For all variants except 2, we found that coexpression of mutant and normal C1INH negatively affected the overall capacity to target proteases. Strikingly, for a subset of variants, intracellular formation of C1INH foci was detectable only in heterozygous configurations enabling simultaneous expression of normal and mutant C1INH. CONCLUSIONS We provide a functional classification of SERPING1 gene variants suggesting that different SERPING1 variants drive the pathogenicity through different and in some cases overlapping molecular disease mechanisms. For a subset of gene variants, our data define some types of hereditary angioedema with C1INH deficiency as serpinopathies driven by dominant-negative disease mechanisms.
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Affiliation(s)
| | - Didde Haslund
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | | | - Rasmus Pihl
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Wariya Sanrattana
- CDL Research, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Steven de Maat
- CDL Research, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Yaseelan Palarasah
- Department of Cancer and Inflammation Research, University of Southern Denmark, Odense, Denmark; Department of Clinical Biochemistry, Hospital of South West Jutland, Esbjerg, Denmark
| | - Coen Maas
- CDL Research, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands; Unit for Thrombosis Research, Department of Regional Health Research, University of Southern Denmark, Esbjerg, Denmark
| | - Steffen Thiel
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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3
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Wang F, Orioli S, Ianeselli A, Spagnolli G, A Beccara S, Gershenson A, Faccioli P, Wintrode PL. All-Atom Simulations Reveal How Single-Point Mutations Promote Serpin Misfolding. Biophys J 2019; 114:2083-2094. [PMID: 29742402 DOI: 10.1016/j.bpj.2018.03.027] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 03/09/2018] [Accepted: 03/13/2018] [Indexed: 10/17/2022] Open
Abstract
Protein misfolding is implicated in many diseases, including serpinopathies. For the canonical inhibitory serpin α1-antitrypsin, mutations can result in protein deficiencies leading to lung disease, and misfolded mutants can accumulate in hepatocytes, leading to liver disease. Using all-atom simulations based on the recently developed bias functional algorithm, we elucidate how wild-type α1-antitrypsin folds and how the disease-associated S (Glu264Val) and Z (Glu342Lys) mutations lead to misfolding. The deleterious Z mutation disrupts folding at an early stage, whereas the relatively benign S mutant shows late-stage minor misfolding. A number of suppressor mutations ameliorate the effects of the Z mutation, and simulations on these mutants help to elucidate the relative roles of steric clashes and electrostatic interactions in Z misfolding. These results demonstrate a striking correlation between atomistic events and disease severity and shine light on the mechanisms driving chains away from their correct folding routes.
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Affiliation(s)
- Fang Wang
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland
| | - Simone Orioli
- Dipartimento di Fisica, Università degli Studi di Trento, Povo (Trento), Italy; Trento Institute for Fundamental Physics and Applications, Povo (Trento), Italy
| | - Alan Ianeselli
- Dipartimento di Fisica, Università degli Studi di Trento, Povo (Trento), Italy; Trento Institute for Fundamental Physics and Applications, Povo (Trento), Italy
| | - Giovanni Spagnolli
- Dipartimento di Fisica, Università degli Studi di Trento, Povo (Trento), Italy; Trento Institute for Fundamental Physics and Applications, Povo (Trento), Italy
| | - Silvio A Beccara
- Dipartimento di Fisica, Università degli Studi di Trento, Povo (Trento), Italy; Trento Institute for Fundamental Physics and Applications, Povo (Trento), Italy
| | - Anne Gershenson
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts.
| | - Pietro Faccioli
- Dipartimento di Fisica, Università degli Studi di Trento, Povo (Trento), Italy; Trento Institute for Fundamental Physics and Applications, Povo (Trento), Italy.
| | - Patrick L Wintrode
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland.
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4
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Wei W, Chen Y, Xie D, Zhou Y. Molecular insight into chymotrypsin inhibitor 2 resisting proteolytic degradation. Phys Chem Chem Phys 2019; 21:5049-5058. [PMID: 30762035 DOI: 10.1039/c8cp07784c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Chymotrypsin inhibitor 2 (CI2) is a special serine protease inhibitor which can resist hydrolysis for several days with a rapid equilibrium between the Michaelis complex and acyl-enzyme intermediate. The energies and conformational changes for subtilisin-catalyzed proteolysis of CI2 were examined in this paper for the first time by employing pseudo bond ab initio QM/MM MD simulations. In the acylation reaction, a low-barrier hydrogen bond between His64 and Asp32 in the transition state together with the lack of covalent backbone constraints makes the peptide bonds of CI2 break more easily than in other serine protease inhibitors. After acyl-enzyme formation, molecular dynamics simulations showed that the access of hydrolytic water to the active site requires partial dissociation of the leaving group. However, retention of the leaving group mainly by the intra- and inter-molecular H-bonding networks hinders the access of water and retards the deacylation reaction. Instead of the dissociation constant of inhibitors, we suggest employing the free energy at the acyl-enzyme state to predict the relative hydrolysis rates of CI2 mutants, which are testified by the experimental relative hydrolysis rates.
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Affiliation(s)
- Wanqing Wei
- Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China.
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5
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Sanrattana W, Maas C, de Maat S. SERPINs-From Trap to Treatment. Front Med (Lausanne) 2019; 6:25. [PMID: 30809526 PMCID: PMC6379291 DOI: 10.3389/fmed.2019.00025] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 01/25/2019] [Indexed: 01/04/2023] Open
Abstract
Excessive enzyme activity often has pathological consequences. This for example is the case in thrombosis and hereditary angioedema, where serine proteases of the coagulation system and kallikrein-kinin system are excessively active. Serine proteases are controlled by SERPINs (serine protease inhibitors). We here describe the basic biochemical mechanisms behind SERPIN activity and identify key determinants that influence their function. We explore the clinical phenotypes of several SERPIN deficiencies and review studies where SERPINs are being used beyond replacement therapy. Excitingly, rare human SERPIN mutations have led us and others to believe that it is possible to refine SERPINs toward desired behavior for the treatment of enzyme-driven pathology.
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Affiliation(s)
| | | | - Steven de Maat
- Department of Clinical Chemistry and Haematology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
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6
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Laffranchi M, Elliston ELK, Gangemi F, Berardelli R, Lomas DA, Irving JA, Fra A. Characterisation of a type II functionally-deficient variant of alpha-1-antitrypsin discovered in the general population. PLoS One 2019; 14:e0206955. [PMID: 30633749 PMCID: PMC6329500 DOI: 10.1371/journal.pone.0206955] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 01/02/2019] [Indexed: 11/23/2022] Open
Abstract
Lung disease in alpha-1-antitrypsin deficiency (AATD) results from dysregulated proteolytic activity, mainly by neutrophil elastase (HNE), in the lung parenchyma. This is the result of a substantial reduction of circulating alpha-1-antitrypsin (AAT) and the presence in the plasma of inactive polymers of AAT. Moreover, some AAT mutants have reduced intrinsic activity toward HNE, as demonstrated for the common Z mutant, as well as for other rarer variants. Here we report the identification and characterisation of the novel AAT reactive centre loop variant Gly349Arg (p.G373R) present in the ExAC database. This AAT variant is secreted at normal levels in cellular models of AATD but shows a severe reduction in anti-HNE activity. Biochemical and molecular dynamics studies suggest it exhibits unfavourable RCL presentation to cognate proteases and compromised insertion of the RCL into β-sheet A. Identification of a fully dysfunctional AAT mutant that does not show a secretory defect underlines the importance of accurate genotyping of patients with pulmonary AATD manifestations regardless of the presence of normal levels of AAT in the circulation. This subtype of disease is reminiscent of dysfunctional phenotypes in anti-thrombin and C1-inibitor deficiencies so, accordingly, we classify this variant as the first pure functionally-deficient (type II) AATD mutant.
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Affiliation(s)
- Mattia Laffranchi
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Emma L K Elliston
- UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, United Kingdom
| | - Fabrizio Gangemi
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Romina Berardelli
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - David A Lomas
- UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, United Kingdom
| | - James A Irving
- UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, United Kingdom
| | - Annamaria Fra
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
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7
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Verhamme IM. A novel antithrombin domain dictates the journey's end of a proteinase. J Biol Chem 2017; 292:16521-16522. [PMID: 28986431 DOI: 10.1074/jbc.h117.787325] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Antithrombin (AT) is an anticoagulant serpin that irreversibly inactivates the clotting proteinases factor Xa and thrombin by forming covalent complexes with them. Mutations in its critical domains, such as those that impair the conformational rearrangement required for proteinase inactivation, increase the risk of venous thrombosis. Águila et al. characterize for the first time the destabilizing effects of mutations in the region of AT that makes contact with the proteinase in the final acyl-enzyme complex. Their work adds new insight into the unique structural intricacies of the inhibitory mechanism.
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Affiliation(s)
- Ingrid M Verhamme
- From the Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
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8
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Águila S, Izaguirre G, Martínez-Martínez I, Vicente V, Olson ST, Corral J. Disease-causing mutations in the serpin antithrombin reveal a key domain critical for inhibiting protease activities. J Biol Chem 2017; 292:16513-16520. [PMID: 28743742 DOI: 10.1074/jbc.m117.787325] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 07/24/2017] [Indexed: 01/05/2023] Open
Abstract
Antithrombin mainly inhibits factor Xa and thrombin. The reactive center loop (RCL) is crucial for its interactions with its protease targets and is fully inserted into the A-sheet after its cleavage, causing translocation of the covalently linked protease to the opposite end of the A-sheet. Antithrombin variants with altered RCL hinge residues behave as substrates rather than inhibitors, resulting in stoichiometries of inhibition greater than one. Other antithrombin residues have been suggested to interfere with RCL insertion or the stability of the antithrombin-protease complex, but available crystal structures or mutagenesis studies have failed to identify such residues. Here, we characterized two mutations, S365L and I207T, present in individuals with type II antithrombin deficiency and identified a new antithrombin functional domain. S365L did not form stable complexes with thrombin or factor Xa, and the I207T/I207A variants inhibited both proteases with elevated stoichiometries of inhibition. Close proximity of Ile-207 and Ser-365 to the inserted RCL suggested that the preferred reaction of these mutants as protease substrates reflects an effect on the rate of the RCL insertion and protease translocation. However, both residues lie within the final docking site for the protease in the antithrombin-protease complex, supporting the idea that the enhanced substrate reactions may result from an increased dissociation of the final complexes. Our findings demonstrate that the distal end of the antithrombin A-sheet is crucial for the last steps of protease inhibition either by affecting the rate of RCL insertion or through critical interactions with proteases at the end of the A-sheet.
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Affiliation(s)
- Sonia Águila
- From the Centro Regional de Hemodonación and Hospital Universitario Morales Meseguer, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB)-Virgen de la Arrixaca, 30003 Murcia, Spain
| | - Gonzalo Izaguirre
- the Department of Periodontics, Center for Molecular Biology of Oral Diseases, University of Illinois at Chicago, Chicago, Illinois 60612, and
| | - Irene Martínez-Martínez
- From the Centro Regional de Hemodonación and Hospital Universitario Morales Meseguer, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB)-Virgen de la Arrixaca, 30003 Murcia, Spain, .,the Centro de Investigación Biomédica en Red Enfermedades Raras (CIBERER), Instituto de Salud Carlos III (ISCIII), 28029 Madrid, Spain
| | - Vicente Vicente
- From the Centro Regional de Hemodonación and Hospital Universitario Morales Meseguer, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB)-Virgen de la Arrixaca, 30003 Murcia, Spain.,the Centro de Investigación Biomédica en Red Enfermedades Raras (CIBERER), Instituto de Salud Carlos III (ISCIII), 28029 Madrid, Spain
| | - Steven T Olson
- the Department of Periodontics, Center for Molecular Biology of Oral Diseases, University of Illinois at Chicago, Chicago, Illinois 60612, and
| | - Javier Corral
- From the Centro Regional de Hemodonación and Hospital Universitario Morales Meseguer, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria (IMIB)-Virgen de la Arrixaca, 30003 Murcia, Spain.,the Centro de Investigación Biomédica en Red Enfermedades Raras (CIBERER), Instituto de Salud Carlos III (ISCIII), 28029 Madrid, Spain
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9
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Inhibitory serpins. New insights into their folding, polymerization, regulation and clearance. Biochem J 2017; 473:2273-93. [PMID: 27470592 DOI: 10.1042/bcj20160014] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 03/31/2016] [Indexed: 12/20/2022]
Abstract
Serpins are a widely distributed family of high molecular mass protein proteinase inhibitors that can inhibit both serine and cysteine proteinases by a remarkable mechanism-based kinetic trapping of an acyl or thioacyl enzyme intermediate that involves massive conformational transformation. The trapping is based on distortion of the proteinase in the complex, with energy derived from the unique metastability of the active serpin. Serpins are the favoured inhibitors for regulation of proteinases in complex proteolytic cascades, such as are involved in blood coagulation, fibrinolysis and complement activation, by virtue of the ability to modulate their specificity and reactivity. Given their prominence as inhibitors, much work has been carried out to understand not only the mechanism of inhibition, but how it is fine-tuned, both spatially and temporally. The metastability of the active state raises the question of how serpins fold, whereas the misfolding of some serpin variants that leads to polymerization and pathologies of liver disease, emphysema and dementia makes it clinically important to understand how such polymerization might occur. Finally, since binding of serpins and their proteinase complexes, particularly plasminogen activator inhibitor-1 (PAI-1), to the clearance and signalling receptor LRP1 (low density lipoprotein receptor-related protein 1), may affect pathways linked to cell migration, angiogenesis, and tumour progression, it is important to understand the nature and specificity of binding. The current state of understanding of these areas is addressed here.
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10
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Ali MF, Kaushik A, Kapil C, Gupta D, Jairajpuri MA. A hydrophobic patch surrounding Trp154 in human neuroserpin controls the helix F dynamics with implications in inhibition and aggregation. Sci Rep 2017; 7:42987. [PMID: 28230174 PMCID: PMC5322333 DOI: 10.1038/srep42987] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 01/17/2017] [Indexed: 01/23/2023] Open
Abstract
Neuroserpin (NS) mediated inhibition of tissue-type plasminogen activator (tPA) is important for brain development, synapse formation and memory. Aberrations in helix F and β-sheet A movement during inhibition can directly lead to epilepsy or dementia. Conserved W154 residue in a hydrophobic patch between helix F and β-sheet A is ideally placed to control their movement during inhibition. Molecular Dynamics (MD) simulation on wild type (WT) NS and its two variants (W154A and W154P) demonstrated partial deformation in helix F and conformational differences in strands 1A and 2A only in W154P. A fluorescence and Circular Dichroism (CD) analysis with purified W154 variants revealed a significant red-shift and an increase in α-helical content in W154P as compared to W154A and WT NS. Kinetics of tPA inhibition showed a decline in association rates (ka) for W154A as compared to WT NS with indication of complex formation. Appearance of cleaved without complex formation in W154P indicates that the variant acts as substrate due to conformational misfolding around helix F. Both the variants however showed increased rate of aggregation as compared to WT NS. The hydrophobic patch identified in this study may have importance in helix F dynamics of NS.
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Affiliation(s)
- Mohammad Farhan Ali
- Protein Conformation and Enzymology Lab, Department of Biosciences, Jamia Millia Islamia (A Central University), New Delhi-110025, India
| | - Abhinav Kaushik
- Translational Bioinformatics Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Charu Kapil
- Protein Conformation and Enzymology Lab, Department of Biosciences, Jamia Millia Islamia (A Central University), New Delhi-110025, India
| | - Dinesh Gupta
- Translational Bioinformatics Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Mohamad Aman Jairajpuri
- Protein Conformation and Enzymology Lab, Department of Biosciences, Jamia Millia Islamia (A Central University), New Delhi-110025, India
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11
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Andersen OJ, Risør MW, Poulsen EC, Nielsen NC, Miao Y, Enghild JJ, Schiøtt B. Reactive Center Loop Insertion in α-1-Antitrypsin Captured by Accelerated Molecular Dynamics Simulation. Biochemistry 2017; 56:634-646. [PMID: 27995800 DOI: 10.1021/acs.biochem.6b00839] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Protease inhibition by metastable serine protease inhibitors (serpins) is mediated by one of the largest functional intradomain conformational changes known in biology. In this extensive structural rearrangement, protease-serpin complex formation triggers cleavage of the serpin reactive center loop (RCL), its subsequent insertion into central β-sheet A, and covalent trapping of the target protease. In this study, we present the first detailed accelerated molecular dynamics simulation of the insertion of the fully cleaved RCL in α-1-antitrypsin (α1AT), the archetypal member of the family of human serpins. Our results reveal internal water pathways that allow the initial incorporation of side chains of RCL residues into the protein interior. We observed structural plasticity of the helix F (hF) element that blocks the RCL path in the native state, which is in excellent agreement with previous experimental reports. Furthermore, the simulation suggested a novel role of hF and the connected turn (thFs3A) as chaperones that support the insertion process by reducing the conformational space available to the RCL. Transient electrostatic interactions of RCL residues potentially fine-tune the serpin inhibitory activity. On the basis of our simulation, we generated the α1AT mutants K168E, E346K, and K168E/E346K and analyzed their inhibitory activity along with their intrinsic stability and heat-induced polymerization. Remarkably, the E346K mutation exhibited enhanced inhibitory activity along with an increased rate of premature structural collapse (polymerization), suggesting a significant role of E346 in the gatekeeping of the strain in the metastable native state.
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Affiliation(s)
- Ole Juul Andersen
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Aarhus, Denmark.,Department of Chemistry, Aarhus University , Aarhus, Denmark
| | - Michael Wulff Risør
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Aarhus, Denmark.,Department of Molecular Biology and Genetics, Aarhus University , Aarhus, Denmark
| | - Emil Christian Poulsen
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Aarhus, Denmark.,Department of Molecular Biology and Genetics, Aarhus University , Aarhus, Denmark
| | - Niels Chr Nielsen
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Aarhus, Denmark.,Department of Chemistry, Aarhus University , Aarhus, Denmark
| | - Yinglong Miao
- Howard Hughes Medical Institute and Department of Pharmacology, University of California at San Diego , La Jolla, California 92093, United States
| | - Jan J Enghild
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Aarhus, Denmark.,Department of Molecular Biology and Genetics, Aarhus University , Aarhus, Denmark
| | - Birgit Schiøtt
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Aarhus, Denmark.,Department of Chemistry, Aarhus University , Aarhus, Denmark
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12
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Haq I, Irving JA, Saleh AD, Dron L, Regan-Mochrie GL, Motamedi-Shad N, Hurst JR, Gooptu B, Lomas DA. Deficiency Mutations of Alpha-1 Antitrypsin. Effects on Folding, Function, and Polymerization. Am J Respir Cell Mol Biol 2016; 54:71-80. [PMID: 26091018 DOI: 10.1165/rcmb.2015-0154oc] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Misfolding, polymerization, and defective secretion of functional alpha-1 antitrypsin underlies the predisposition to severe liver and lung disease in alpha-1 antitrypsin deficiency. We have identified a novel (Ala336Pro, Baghdad) deficiency variant and characterized it relative to the wild-type (M) and Glu342Lys (Z) alleles. The index case is a homozygous individual of consanguineous parentage, with levels of circulating alpha-1 antitrypsin in the moderate deficiency range, but is a biochemical phenotype that could not be classified by standard methods. The majority of the protein was present as functionally inactive polymer, and the remaining monomer was 37% active relative to the wild-type protein. These factors combined indicate an 85 to 95% functional deficiency, similar to that seen with ZZ homozygotes. Biochemical, biophysical, and computational studies further defined the molecular basis of this deficiency. These studies demonstrated that native Ala336Pro alpha-1 antitrypsin could populate the polymerogenic intermediate-and therefore polymerize-more readily than either wild-type alpha-1 antitrypsin or the Z variant. In contrast, folding was far less impaired in Ala336Pro alpha-1 antitrypsin than in the Z variant. The data are consistent with a disparate contribution by the "breach" region and "shutter" region of strand 5A to folding and polymerization mechanisms. Moreover, the findings demonstrate that, in these variants, folding efficiency does not correlate directly with the tendency to polymerize in vitro or in vivo. They therefore differentiate generalized misfolding from polymerization tendencies in missense variants of alpha-1 antitrypsin. Clinically, they further support the need to quantify loss-of-function in alpha-1 antitrypsin deficiency to individualize patient care.
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Affiliation(s)
- Imran Haq
- 1 Wolfson Institute for Biomedical Research, University College London, London, United Kingdom.,2 Institute of Structural and Molecular Biology/Birkbeck, University of London, London, United Kingdom
| | - James A Irving
- 1 Wolfson Institute for Biomedical Research, University College London, London, United Kingdom.,2 Institute of Structural and Molecular Biology/Birkbeck, University of London, London, United Kingdom
| | - Aarash D Saleh
- 3 London Alpha-1 Antitrypsin Deficiency Service, Royal Free Hospital, Pond Street, London, United Kingdom; and
| | - Louis Dron
- 3 London Alpha-1 Antitrypsin Deficiency Service, Royal Free Hospital, Pond Street, London, United Kingdom; and
| | - Gemma L Regan-Mochrie
- 1 Wolfson Institute for Biomedical Research, University College London, London, United Kingdom
| | - Neda Motamedi-Shad
- 1 Wolfson Institute for Biomedical Research, University College London, London, United Kingdom.,2 Institute of Structural and Molecular Biology/Birkbeck, University of London, London, United Kingdom
| | - John R Hurst
- 3 London Alpha-1 Antitrypsin Deficiency Service, Royal Free Hospital, Pond Street, London, United Kingdom; and
| | - Bibek Gooptu
- 2 Institute of Structural and Molecular Biology/Birkbeck, University of London, London, United Kingdom.,3 London Alpha-1 Antitrypsin Deficiency Service, Royal Free Hospital, Pond Street, London, United Kingdom; and.,4 Division of Asthma, Allergy and Lung Biology, King's College London, London, United Kingdom
| | - David A Lomas
- 1 Wolfson Institute for Biomedical Research, University College London, London, United Kingdom.,2 Institute of Structural and Molecular Biology/Birkbeck, University of London, London, United Kingdom.,3 London Alpha-1 Antitrypsin Deficiency Service, Royal Free Hospital, Pond Street, London, United Kingdom; and
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Abstract
Protease inhibition by serpins requires a large conformational transition from an active, metastable state to an inactive, stable state. Similar reactions can also occur in the absence of proteases, and these latency transitions take hours, making their time scales many orders of magnitude larger than are currently accessible using conventional molecular dynamics simulations. Using a variational path sampling algorithm, we simulated the entire serpin active-to-latent transition in all-atom detail with a physically realistic force field using a standard computing cluster. These simulations provide a unifying picture explaining existing experimental data for the latency transition of the serpin plasminogen activator inhibitor-1 (PAI-1). They predict a long-lived intermediate that resembles a previously proposed, partially loop-inserted, prelatent state; correctly predict the effects of PAI-1 mutations on the kinetics; and provide a potential means to identify ligands able to accelerate the latency transition. Interestingly, although all of the simulated PAI-1 variants readily access the prelatent intermediate, this conformation is not populated in the active-to-latent transition of another serpin, α1-antitrypsin, which does not readily go latent. Thus, these simulations also help elucidate why some inhibitory serpin families are more conformationally labile than others.
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