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Kamuda K, Ronzoni R, Majumdar A, Guan FHX, Irving JA, Lomas DA. A novel pathological mutant reveals the role of torsional flexibility in the serpin breach in adoption of an aggregation-prone intermediate. FEBS J 2024. [PMID: 38523412 DOI: 10.1111/febs.17121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 02/17/2024] [Accepted: 03/07/2024] [Indexed: 03/26/2024]
Abstract
Mutants of alpha-1-antitrypsin cause the protein to self-associate and form ordered aggregates ('polymers') that are retained within hepatocytes, resulting in a predisposition to the development of liver disease. The associated reduction in secretion, and for some mutants, impairment of function, leads to a failure to protect lung tissue against proteases released during the inflammatory response and an increased risk of emphysema. We report here a novel deficiency mutation (Gly192Cys), that we name the Sydney variant, identified in a patient in heterozygosity with the Z allele (Glu342Lys). Cellular analysis revealed that the novel variant was mostly retained as insoluble polymers within the endoplasmic reticulum. The basis for this behaviour was investigated using biophysical and structural techniques. The variant showed a 40% reduction in inhibitory activity and a reduced stability as assessed by thermal unfolding experiments. Polymerisation involves adoption of an aggregation-prone intermediate and paradoxically the energy barrier for transition to this state was increased by 16% for the Gly192Cys variant with respect to the wild-type protein. However, with activation to the intermediate state, polymerisation occurred at a 3.8-fold faster rate overall. X-ray crystallography provided two crystal structures of the Gly192Cys variant, revealing perturbation within the 'breach' region with Cys192 in two different orientations: in one structure it faces towards the hydrophobic core while in the second it is solvent-exposed. This orientational heterogeneity was confirmed by PEGylation. These data show the critical role of the torsional freedom imparted by Gly192 in inhibitory activity and stability against polymerisation.
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Affiliation(s)
- Kamila Kamuda
- Division of Medicine, UCL Respiratory, Rayne Institute, University College London, UK
- Institute of Structural and Molecular Biology, Birkbeck College, University College London, UK
| | - Riccardo Ronzoni
- Division of Medicine, UCL Respiratory, Rayne Institute, University College London, UK
- Institute of Structural and Molecular Biology, Birkbeck College, University College London, UK
| | - Avik Majumdar
- AW Morrow Gastroenterology and Liver Centre, Royal Prince Alfred Hospital, Sydney, Australia
- Victorian Liver Transplant Unit, Austin Health, Melbourne, Australia
- The University of Melbourne, Melbourne, Australia
| | - Fiona H X Guan
- AW Morrow Gastroenterology and Liver Centre, Royal Prince Alfred Hospital, Sydney, Australia
| | - James A Irving
- Division of Medicine, UCL Respiratory, Rayne Institute, University College London, UK
- Institute of Structural and Molecular Biology, Birkbeck College, University College London, UK
| | - David A Lomas
- Division of Medicine, UCL Respiratory, Rayne Institute, University College London, UK
- Institute of Structural and Molecular Biology, Birkbeck College, University College London, UK
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Balderacchi AM, Bignotti M, Ottaviani S, Denardo A, Barzon V, Ben Khlifa E, Vailati G, Piloni D, Benini F, Corda L, Corsico AG, Ferrarotti I, Fra A. Quantification of circulating alpha-1-antitrypsin polymers associated with different SERPINA1 genotypes. Clin Chem Lab Med 2024; 0:cclm-2023-1348. [PMID: 38407261 DOI: 10.1515/cclm-2023-1348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Accepted: 02/15/2024] [Indexed: 02/27/2024]
Abstract
OBJECTIVES Alpha-1-antitrypsin deficiency is a genetic disorder caused by mutations in the SERPINA1 gene encoding alpha-1-antitrypsin (AAT), the major serine protease inhibitor in plasma. Reduced AAT levels are associated with elevated risk of developing emphysema mainly due to uncontrolled activity of neutrophil elastase in the lungs. The prevalent Z-AAT mutant and many rare pathogenic AAT variants also predispose to liver disease due to their accumulation as polymeric chains in hepatocytes. Part of these polymers are secreted into the bloodstream and could represent biomarkers of intra-hepatic accumulation. Moreover, being inactive, they further lower lung protection against proteases. Aim of our study is to accurately quantify the percentage of circulating polymers (CP) in a cohort of subjects with different SERPINA1 genotypes. METHODS CP concentration was measured in plasma or Dried Blood Spot (DBS) by a sensitive sandwich ELISA based on capture by the polymer-specific 2C1 monoclonal antibody. RESULTS CP were significantly elevated in patients with the prevalent PI*SZ and PI*ZZ genotypes, with considerable intra-genotype variability. Notably, higher percentage of polymers was observed in association with elevated C-reactive protein. CP levels were also increased in carriers of the Mmalton variant, and of Mprocida, I, Plowell and Mherleen in heterozygosity with Z-AAT. CONCLUSIONS These findings highlight the importance of implementing CP quantification in a clinical laboratory. Indeed, the variable amount of CP in patients with the same genotype may correlate with the variable severity of the associated lung and liver diseases. Moreover, CP can reveal the polymerogenic potential of newly discovered ultrarare AAT variants.
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Affiliation(s)
- Alice M Balderacchi
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, UOC Pulmonology, 18631Fondazione IRCCS Policlinico San Matteo, Pavia, Italy
| | - Mattia Bignotti
- Experimental Oncology and Immunology, Department of Molecular and Translational Medicine, 9297University of Brescia, Brescia, Italy
| | - Stefania Ottaviani
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, UOC Pulmonology, 18631Fondazione IRCCS Policlinico San Matteo, Pavia, Italy
| | - Andrea Denardo
- Experimental Oncology and Immunology, Department of Molecular and Translational Medicine, 9297University of Brescia, Brescia, Italy
| | - Valentina Barzon
- Department of Internal Medicine and Therapeutics, Pulmonology Unit, 19001University of Pavia, Pavia, Italy
| | - Emna Ben Khlifa
- Experimental Oncology and Immunology, Department of Molecular and Translational Medicine, 9297University of Brescia, Brescia, Italy
| | - Guido Vailati
- Referral Centre for Alpha-1 Antitrypsin Deficiency, 18515 Spedali Civili , Brescia, Italy
| | - Davide Piloni
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, UOC Pulmonology, 18631Fondazione IRCCS Policlinico San Matteo, Pavia, Italy
| | - Federica Benini
- Referral Centre for Alpha-1 Antitrypsin Deficiency, 18515 Spedali Civili , Brescia, Italy
| | - Luciano Corda
- Referral Centre for Alpha-1 Antitrypsin Deficiency, 18515 Spedali Civili , Brescia, Italy
| | - Angelo G Corsico
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, UOC Pulmonology, 18631Fondazione IRCCS Policlinico San Matteo, Pavia, Italy
- Department of Internal Medicine and Therapeutics, Pulmonology Unit, 19001University of Pavia, Pavia, Italy
| | - Ilaria Ferrarotti
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, UOC Pulmonology, 18631Fondazione IRCCS Policlinico San Matteo, Pavia, Italy
- Department of Internal Medicine and Therapeutics, Pulmonology Unit, 19001University of Pavia, Pavia, Italy
| | - Annamaria Fra
- Experimental Oncology and Immunology, Department of Molecular and Translational Medicine, 9297University of Brescia, Brescia, Italy
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Barzon V, Ferrarotti I, Ottaviani S. Sanger and Next-Generation Sequencing of AAT. Methods Mol Biol 2024; 2750:57-67. [PMID: 38108967 DOI: 10.1007/978-1-0716-3605-3_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Sequencing of DNA is normally the final procedure carried out to determine the actual pathogenic variants when the techniques used for genotyping are unable to provide complete identification of both AAT alleles. Gene sequencing of complete SERPINA1 gene by using the Sanger method or next-generation sequencing (NGS) is crucial to enable correct diagnosis in patients with alpha1-antitrypsin deficiency caused by uncommon AAT variants.This protocol explains how to correctly sequence SERPINA1 gene both with Sanger method and NGS.
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Affiliation(s)
- Valentina Barzon
- Department of Internal Medicine and Therapeutics, Pulmonology Unit, University of Pavia, Pavia, Italy
| | - Ilaria Ferrarotti
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, UOC Pulmonology, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy.
| | - Stefania Ottaviani
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, UOC Pulmonology, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy
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Denardo A, Ben Khlifa E, Bignotti M, Fra A. Characterization of Novel Alpha-1-Antitrypsin Coding Variants in a Mammalian Cellular Model. Methods Mol Biol 2024; 2750:79-93. [PMID: 38108969 DOI: 10.1007/978-1-0716-3605-3_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Advances in genetic screening technologies have considerably accelerated the discovery of rare alpha-1-antitrypsin (AAT) variants. Expression in cellular models is an effective approach to evaluate the pathogenic potential of these new AAT variants, whose clinical significance would otherwise remain uncertain. Here we provide a detailed description of established methods for in vitro characterization of AAT coding variants expressed in HEK293T/17 cells. The protocols include determination of secretion efficiency, the tendency to form polymeric chains and the anti-elastase inhibitory activity.
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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
| | - Annamaria Fra
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
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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: 0] [Impact Index Per Article: 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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Ottaviani S, Bartoli G, Carroll TP, Gangemi F, Balderacchi AM, Barzon V, Corino A, Piloni D, McElvaney NG, Corsico AG, Irving JA, Fra A, Ferrarotti I. Comprehensive Clinical Diagnostic Pipelines Reveal New Variants in Alpha-1 Antitrypsin Deficiency. Am J Respir Cell Mol Biol 2023; 69:355-366. [PMID: 37071847 DOI: 10.1165/rcmb.2022-0470oc] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 04/18/2023] [Indexed: 04/20/2023] Open
Abstract
Alpha-1 antitrypsin deficiency (AATD) is an underdiagnosed disorder associated with mutations in the SERPINA1 gene encoding alpha-1 antitrypsin (AAT). Severe AATD can manifest as pulmonary emphysema and progressive liver disease. Besides the most common pathogenic variants S (E264V) and Z (E342K), many rarer genetic variants of AAT have been found in patients and in the general population. Here we report a panel of new SERPINA1 variants, including 4 null and 16 missense alleles, identified among a cohort of individuals with suspected AATD whose phenotypic follow-up showed inconclusive or atypical results. Because the pathogenic significance of the missense variants was unclear purely on the basis of clinical data, the integration of computational, biochemical, and cellular studies was used to define the associated risk of disease. Established pathogenicity predictors and structural analysis identified a panel of candidate damaging mutations that were characterized by expression in mammalian cell models. Polymer formation, intracellular accumulation, and secretory efficiency were evaluated experimentally. Our results identified two AAT mutants with a Z-like polymerogenic severe deficiency profile (Smilano and Mcampolongo) and three milder variants (Xsarezzo, Pdublin, and Ctiberias). Overall, the experimentally determined behavior of the variants was in agreement with the pathogenicity scores of the REVEL (an ensemble method for predicting the pathogenicity of rare missense variants) predictor, supporting the utility of this bioinformatic tool in the initial assessment of newly identified amino acid substitutions of AAT. Our study, in addition to describing 20 new SERPINA1 variants, provides a model for a multidisciplinary approach to classification of rare AAT variants and their clinical impact on individuals with rare AATD genotypes.
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Affiliation(s)
- Stefania Ottaviani
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, Unità Operativa Complessa Pneumologia, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, Pavia, Italy
| | - Giulia Bartoli
- Experimental Oncology and Immunology, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Tomás P Carroll
- α-1 Foundation Ireland, Irish Centre for Genetic Lung Disease, Royal College of Surgeons in Ireland Education and Research Centre, Beaumont Hospital, Dublin, Ireland
| | - Fabrizio Gangemi
- Experimental Oncology and Immunology, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Alice M Balderacchi
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, Unità Operativa Complessa Pneumologia, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, Pavia, Italy
| | - Valentina Barzon
- Department of Internal Medicine and Therapeutics, Pulmonology Unit, University of Pavia, Pavia, Italy
| | - Alessandra Corino
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, Unità Operativa Complessa Pneumologia, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, Pavia, Italy
| | - Davide Piloni
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, Unità Operativa Complessa Pneumologia, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, Pavia, Italy
| | - Noel G McElvaney
- α-1 Foundation Ireland, Irish Centre for Genetic Lung Disease, Royal College of Surgeons in Ireland Education and Research Centre, Beaumont Hospital, Dublin, Ireland
| | - Angelo G Corsico
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, Unità Operativa Complessa Pneumologia, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, Pavia, Italy
- Department of Internal Medicine and Therapeutics, Pulmonology Unit, University of Pavia, Pavia, Italy
- European Reference Network on Rare Respiratory Diseases (ERN-LUNG); and
| | - James A Irving
- University College London Respiratory, Rayne Institute and the Institute of Structural and Molecular Biology, University College London, London, United Kingdom
| | - Annamaria Fra
- Experimental Oncology and Immunology, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Ilaria Ferrarotti
- Centre for Diagnosis of Inherited Alpha-1 Antitrypsin Deficiency, Unità Operativa Complessa Pneumologia, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, Pavia, Italy
- Department of Internal Medicine and Therapeutics, Pulmonology Unit, University of Pavia, Pavia, Italy
- European Reference Network on Rare Respiratory Diseases (ERN-LUNG); and
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