1
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Guay KP, Ke H, Canniff NP, George GT, Eyles SJ, Mariappan M, Contessa JN, Gershenson A, Gierasch LM, Hebert DN. ER chaperones use a protein folding and quality control glyco-code. Mol Cell 2023; 83:4524-4537.e5. [PMID: 38052210 PMCID: PMC10790639 DOI: 10.1016/j.molcel.2023.11.006] [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: 08/18/2023] [Revised: 10/18/2023] [Accepted: 11/07/2023] [Indexed: 12/07/2023]
Abstract
N-glycans act as quality control tags by recruiting lectin chaperones to assist protein maturation in the endoplasmic reticulum. The location and composition of N-glycans (glyco-code) are key to the chaperone-selection process. Serpins, a class of serine protease inhibitors, fold non-sequentially to achieve metastable active states. Here, the role of the glyco-code in assuring successful maturation and quality control of two human serpins, alpha-1 antitrypsin (AAT) and antithrombin III (ATIII), is described. We find that AAT, which has glycans near its N terminus, is assisted by early lectin chaperone binding. In contrast, ATIII, which has more C-terminal glycans, is initially helped by BiP and then later by lectin chaperones mediated by UGGT reglucosylation. UGGT action is increased for misfolding-prone disease variants, and these clients are preferentially glucosylated on their most C-terminal glycan. Our study illustrates how serpins utilize N-glycan presence, position, and composition to direct their proper folding, quality control, and trafficking.
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Affiliation(s)
- Kevin P Guay
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Haiping Ke
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Nathan P Canniff
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Gracie T George
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Stephen J Eyles
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Institute for Applied Life Sciences, Mass Spectrometry Center, University of Massachusetts Amherst, Amherst, MA, USA
| | - Malaiyalam Mariappan
- Department of Cell Biology, Nanobiology Institute, Yale School of Medicine, West Haven, CT, USA
| | - Joseph N Contessa
- Departments of Therapeutic Radiology and Pharmacology, Yale School of Medicine, New Haven, CT, USA
| | - Anne Gershenson
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Lila M Gierasch
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Department of Chemistry, University of Massachusetts Amherst, Amherst, MA, USA
| | - Daniel N Hebert
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA.
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2
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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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3
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Kaur U, Kihn KC, Ke H, Kuo W, Gierasch LM, Hebert DN, Wintrode PL, Deredge D, Gershenson A. The conformational landscape of a serpin N-terminal subdomain facilitates folding and in-cell quality control. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.24.537978. [PMID: 37163105 PMCID: PMC10168285 DOI: 10.1101/2023.04.24.537978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Many multi-domain proteins including the serpin family of serine protease inhibitors contain non-sequential domains composed of regions that are far apart in sequence. Because proteins are translated vectorially from N- to C-terminus, such domains pose a particular challenge: how to balance the conformational lability necessary to form productive interactions between early and late translated regions while avoiding aggregation. This balance is mediated by the protein sequence properties and the interactions of the folding protein with the cellular quality control machinery. For serpins, particularly α 1 -antitrypsin (AAT), mutations often lead to polymer accumulation in cells and consequent disease suggesting that the lability/aggregation balance is especially precarious. Therefore, we investigated the properties of progressively longer AAT N-terminal fragments in solution and in cells. The N-terminal subdomain, residues 1-190 (AAT190), is monomeric in solution and efficiently degraded in cells. More β -rich fragments, 1-290 and 1-323, form small oligomers in solution, but are still efficiently degraded, and even the polymerization promoting Siiyama (S53F) mutation did not significantly affect fragment degradation. In vitro, the AAT190 region is among the last regions incorporated into the final structure. Hydrogen-deuterium exchange mass spectrometry and enhanced sampling molecular dynamics simulations show that AAT190 has a broad, dynamic conformational ensemble that helps protect one particularly aggregation prone β -strand from solvent. These AAT190 dynamics result in transient exposure of sequences that are buried in folded, full-length AAT, which may provide important recognition sites for the cellular quality control machinery and facilitate degradation and, under favorable conditions, reduce the likelihood of polymerization.
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Affiliation(s)
- Upneet Kaur
- Department of Biochemistry & Molecular Biology, University of Massachusetts, Amherst, MA 01003
| | - Kyle C. Kihn
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201
| | - Haiping Ke
- Department of Biochemistry & Molecular Biology, University of Massachusetts, Amherst, MA 01003
| | - Weiwei Kuo
- Department of Biochemistry & Molecular Biology, University of Massachusetts, Amherst, MA 01003
| | - Lila M. Gierasch
- Department of Biochemistry & Molecular Biology, University of Massachusetts, Amherst, MA 01003
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA 01003
- Department of Chemistry, University of Massachusetts, Amherst, MA 01003
| | - Daniel N. Hebert
- Department of Biochemistry & Molecular Biology, University of Massachusetts, Amherst, MA 01003
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA 01003
| | - Patrick L. Wintrode
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201
| | - Daniel Deredge
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201
| | - Anne Gershenson
- Department of Biochemistry & Molecular Biology, University of Massachusetts, Amherst, MA 01003
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA 01003
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4
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Bravo-Pérez C, Toderici M, Chambers JE, Martínez-Menárguez JA, Garrido-Rodriguez P, Pérez-Sanchez H, de la Morena-Barrio B, Padilla J, Miñano A, Cifuentes-Riquelme R, Vicente V, Lozano ML, Marciniak SJ, de la Morena-Barrio ME, Corral J. Full-length antithrombin frameshift variant with aberrant C-terminus causes endoplasmic reticulum retention with a dominant-negative effect. JCI Insight 2022; 7:161430. [PMID: 36214221 PMCID: PMC9675572 DOI: 10.1172/jci.insight.161430] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 08/24/2022] [Indexed: 02/02/2023] Open
Abstract
Antithrombin, a major endogenous anticoagulant, is a serine protease inhibitor (serpin). We characterized the biological and clinical impact of variants involving C-terminal antithrombin. We performed comprehensive molecular, cellular, and clinical characterization of patients with C-terminal antithrombin variants from a cohort of 444 unrelated individuals with confirmed antithrombin deficiency. We identified 17 patients carrying 12 C-terminal variants, 5 of whom had the p.Arg445Serfs*17 deletion. Five missense variants caused qualitative deficiency, and 7, including 4 insertion-deletion variants, induced severe quantitative deficiency, particularly p.Arg445Serfs*17 (antithrombin <40%). This +1 frameshift variant had a molecular size similar to that of WT antithrombin but possessed a different C-terminus. Morphologic and cotransfection experiments showed that recombinant p.Arg445Serfs*17 was retained at the endoplasmic reticulum and had a dominant-negative effect on WT antithrombin. Characterization of different 1+ frameshift, aberrant C-terminal variants revealed that protein secretion was determined by frameshift site. The introduction of Pro441 in the aberrant C-terminus, shared by 5 efficiently secreted variants, partially rescued p.Arg445Serfs*17 secretion. C-terminal antithrombin mutants have notable heterogeneity, related to variant type and localization. Aberrant C-terminal variants caused by 1+ frameshift, with similar size as WT antithrombin, may be secreted or not, depending on frameshift site. The severe clinical phenotypes of these genetic changes are consistent with their dominant-negative effects.
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Affiliation(s)
- Carlos Bravo-Pérez
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Mara Toderici
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Joseph E. Chambers
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - José A. Martínez-Menárguez
- Department of Cell Biology and Histology, Medical School, Biomedical Research Institute of Murcia, University of Murcia, Campus Mare Nostrum, Murcia, Spain
| | - Pedro Garrido-Rodriguez
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Horacio Pérez-Sanchez
- Structural Bioinformatics and High Performance Computing Research Group, Universidad Católica de Murcia, Murcia, Spain
| | - Belén de la Morena-Barrio
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - José Padilla
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Antonia Miñano
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Rosa Cifuentes-Riquelme
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Vicente Vicente
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Maria L. Lozano
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Stefan J. Marciniak
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Maria Eugenia de la Morena-Barrio
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
| | - Javier Corral
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, University of Murcia, Biomedical Research Institute of Murcia, CB15/00055-CIBERER, Murcia, Spain
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5
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Chambers JE, Zubkov N, Kubánková M, Nixon-Abell J, Mela I, Abreu S, Schwiening M, Lavarda G, López-Duarte I, Dickens JA, Torres T, Kaminski CF, Holt LJ, Avezov E, Huntington JA, George-Hyslop PS, Kuimova MK, Marciniak SJ. Z-α 1-antitrypsin polymers impose molecular filtration in the endoplasmic reticulum after undergoing phase transition to a solid state. SCIENCE ADVANCES 2022; 8:eabm2094. [PMID: 35394846 PMCID: PMC8993113 DOI: 10.1126/sciadv.abm2094] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 02/16/2022] [Indexed: 05/06/2023]
Abstract
Misfolding of secretory proteins in the endoplasmic reticulum (ER) features in many human diseases. In α1-antitrypsin deficiency, the pathogenic Z variant aberrantly assembles into polymers in the hepatocyte ER, leading to cirrhosis. We show that α1-antitrypsin polymers undergo a liquid:solid phase transition, forming a protein matrix that retards mobility of ER proteins by size-dependent molecular filtration. The Z-α1-antitrypsin phase transition is promoted during ER stress by an ATF6-mediated unfolded protein response. Furthermore, the ER chaperone calreticulin promotes Z-α1-antitrypsin solidification and increases protein matrix stiffness. Single-particle tracking reveals that solidification initiates in cells with normal ER morphology, previously assumed to represent a healthy pool. We show that Z-α1-antitrypsin-induced hypersensitivity to ER stress can be explained by immobilization of ER chaperones within the polymer matrix. This previously unidentified mechanism of ER dysfunction provides a template for understanding a diverse group of related proteinopathies and identifies ER chaperones as potential therapeutic targets.
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Affiliation(s)
- Joseph E. Chambers
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Nikita Zubkov
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Markéta Kubánková
- Department of Chemistry, Imperial College London, Wood Lane, London W12 0BZ, UK
| | - Jonathon Nixon-Abell
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Ioanna Mela
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, UK
| | - Susana Abreu
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Max Schwiening
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Giulia Lavarda
- Departamento de Química Orgánica and Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Madrid 28049, Spain
| | - Ismael López-Duarte
- Departamento de Química Orgánica and Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Madrid 28049, Spain
| | - Jennifer A. Dickens
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Tomás Torres
- Departamento de Química Orgánica and Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Madrid 28049, Spain
- IMDEA Nanociencia, Campus de Cantoblanco, Madrid 28049, Spain
| | - Clemens F. Kaminski
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, UK
| | - Liam J. Holt
- Institute for Systems Genetics, New York University Grossman School of Medicine, 435 E 30th St, New York, NY 10016, USA
| | - Edward Avezov
- Department of Clinical Neurosciences and UK Dementia Research Institute, University of Cambridge, Cambridge CB2 0AH, UK
| | - James A. Huntington
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Peter St George-Hyslop
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
- Department of Medicine (Neurology), Temerty Faculty of Medicine, University of Toronto, University Health Network, Toronto, ON M5T 0S8, Canada
- Taub Institute For Research on Alzheimer’s Disease and the Ageing Brain, Department of Neurology, Columbia University Irvine Medical Center, 630 West 1/68 Street, New York, NY 10032, USA
| | - Marina K. Kuimova
- Department of Chemistry, Imperial College London, Wood Lane, London W12 0BZ, UK
| | - Stefan J. Marciniak
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
- Royal Papworth Hospital, Cambridge CB2 0AY, UK
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6
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Maslakova AA, Didych DA, Golyshev SA, Katrukha IA, Viushkov VS, Zamalutdinov AV, Potashnikova DM, Rubtsov MA, Smirnova OV, Orlovsky IV. Towards unveiling the nature of short SERPINA1 transcripts: Avoiding the main ORF control to translate alpha1-antitrypsin C-terminal peptides. Int J Biol Macromol 2022; 203:703-717. [PMID: 35090941 DOI: 10.1016/j.ijbiomac.2022.01.131] [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: 10/31/2021] [Accepted: 01/19/2022] [Indexed: 11/27/2022]
Abstract
Alternative ORFs in-frame with the known genes are challenging to reveal. Yet they may contribute significantly to proteome diversity. Here we focused on the individual expression of the SERPINA1 gene exon 5 leading to direct translation of alpha1-antitrypsin (AAT) C-terminal peptides. The discovery of alternative ways for their production may expand the current understanding of the serpin gene's functioning. We detected short transcripts expressed primarily in hepatocytes. We identified four variants of hepatocyte-specific SERPINA1 short transcripts and individually probed their potential to be translated in living cells. The long mRNA gave the full-length AAT-eGFP fusion, while in case of short transcripts we deduced four active SERPINA1 in-frame alternative ORFs encoding 10, 21, 153 and 169 amino acids AAT C-terminal oligo- and polypeptides. Unlike secretory AAT-eGFP fusion exhibiting classical AAT behavior, truncated AAT-fusions differ by intracellular retention and nuclear enrichment. Immunofluorescence on the endogenous AAT C-terminal epitope showed its accumulation in the cell nucleoli, indicating that short transcripts may be translated in vivo. FANTOM5 CAGE data on SERPINA1 suggest that short transcripts originate from the post-transcriptional cleavage of the spliced mRNA, initiated mainly from the hepatocyte-specific promoter. CONCLUSION: Short SERPINA1 transcripts may represent a source for the direct synthesis of AAT C-terminal peptides with properties uncommon to AAT.
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Affiliation(s)
- A A Maslakova
- Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia.
| | - D A Didych
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Miklukho-Maklaya, Moscow 117997, Russia
| | - S A Golyshev
- A.N. Belozersky Research Institute of Physical and Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119992, Russia
| | - I A Katrukha
- Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia; HyTest Ltd., Joukahaisenkatu, Turku 20520, Finland
| | - V S Viushkov
- Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia
| | - A V Zamalutdinov
- Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia
| | - D M Potashnikova
- Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia
| | - M A Rubtsov
- Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia; I.M. Sechenov First Moscow State Medical University (Sechenov University), Trubetskaya, Moscow 119991, Russia
| | - O V Smirnova
- Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia
| | - I V Orlovsky
- A.N. Belozersky Research Institute of Physical and Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119992, Russia
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7
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Plessa E, Chu LP, Chan SHS, Thomas OL, Cassaignau AME, Waudby CA, Christodoulou J, Cabrita LD. Nascent chains can form co-translational folding intermediates that promote post-translational folding outcomes in a disease-causing protein. Nat Commun 2021; 12:6447. [PMID: 34750347 PMCID: PMC8576036 DOI: 10.1038/s41467-021-26531-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 10/01/2021] [Indexed: 01/16/2023] Open
Abstract
During biosynthesis, proteins can begin folding co-translationally to acquire their biologically-active structures. Folding, however, is an imperfect process and in many cases misfolding results in disease. Less is understood of how misfolding begins during biosynthesis. The human protein, alpha-1-antitrypsin (AAT) folds under kinetic control via a folding intermediate; its pathological variants readily form self-associated polymers at the site of synthesis, leading to alpha-1-antitrypsin deficiency. We observe that AAT nascent polypeptides stall during their biosynthesis, resulting in full-length nascent chains that remain bound to ribosome, forming a persistent ribosome-nascent chain complex (RNC) prior to release. We analyse the structure of these RNCs, which reveals compacted, partially-folded co-translational folding intermediates possessing molten-globule characteristics. We find that the highly-polymerogenic mutant, Z AAT, forms a distinct co-translational folding intermediate relative to wild-type. Its very modest structural differences suggests that the ribosome uniquely tempers the impact of deleterious mutations during nascent chain emergence. Following nascent chain release however, these co-translational folding intermediates guide post-translational folding outcomes thus suggesting that Z's misfolding is initiated from co-translational structure. Our findings demonstrate that co-translational folding intermediates drive how some proteins fold under kinetic control, and may thus also serve as tractable therapeutic targets for human disease.
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Affiliation(s)
- Elena Plessa
- Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Lien P Chu
- Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Sammy H S Chan
- Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Oliver L Thomas
- Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Anaïs M E Cassaignau
- Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Christopher A Waudby
- Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - John Christodoulou
- Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, UK. .,School of Crystallography, Birkbeck College, University of London, Malet Street, London, WC1E 7HX, UK.
| | - Lisa D Cabrita
- Institute of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, UK.
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8
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Faull SV, Elliston ELK, Gooptu B, Jagger AM, Aldobiyan I, Redzej A, Badaoui M, Heyer-Chauhan N, Rashid ST, Reynolds GM, Adams DH, Miranda E, Orlova EV, Irving JA, Lomas DA. The structural basis for Z α 1-antitrypsin polymerization in the liver. SCIENCE ADVANCES 2020; 6:6/43/eabc1370. [PMID: 33087346 PMCID: PMC7577719 DOI: 10.1126/sciadv.abc1370] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Accepted: 09/08/2020] [Indexed: 05/22/2023]
Abstract
The serpinopathies are among a diverse set of conformational diseases that involve the aberrant self-association of proteins into ordered aggregates. α1-Antitrypsin deficiency is the archetypal serpinopathy and results from the formation and deposition of mutant forms of α1-antitrypsin as "polymer" chains in liver tissue. No detailed structural analysis has been performed of this material. Moreover, there is little information on the relevance of well-studied artificially induced polymers to these disease-associated molecules. We have isolated polymers from the liver tissue of Z α1-antitrypsin homozygotes (E342K) who have undergone transplantation, labeled them using a Fab fragment, and performed single-particle analysis of negative-stain electron micrographs. The data show structural equivalence between heat-induced and ex vivo polymers and that the intersubunit linkage is best explained by a carboxyl-terminal domain swap between molecules of α1-antitrypsin.
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Affiliation(s)
- Sarah V Faull
- UCL Respiratory, University College London, 5 University Street, London WC1E 6JF, UK
| | - Emma L K Elliston
- UCL Respiratory, University College London, 5 University Street, London WC1E 6JF, UK
- Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BN, UK
| | - Bibek Gooptu
- Leicester Institute of Structural and Chemical Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7HB, UK
- National Institute for Health Research (NIHR) Leicester BRC-Respiratory, Leicester, UK
- Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, University of London, London WC1E 7HX, UK
| | - Alistair M Jagger
- UCL Respiratory, University College London, 5 University Street, London WC1E 6JF, UK
- Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BN, UK
| | - Ibrahim Aldobiyan
- UCL Respiratory, University College London, 5 University Street, London WC1E 6JF, UK
- Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BN, UK
| | - Adam Redzej
- Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, University of London, London WC1E 7HX, UK
| | - Magd Badaoui
- UCL Respiratory, University College London, 5 University Street, London WC1E 6JF, UK
| | - Nina Heyer-Chauhan
- UCL Respiratory, University College London, 5 University Street, London WC1E 6JF, UK
- Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BN, UK
| | - S Tamir Rashid
- Centre for Stem Cells and Regenerative Medicine and Institute for Liver Studies, King's College London, London WC2R 2LS, UK
| | - Gary M Reynolds
- Centre for Liver Research and NIHR Birmingham Liver Biomedical Research Unit, Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK
| | - David H Adams
- Centre for Liver Research and NIHR Birmingham Liver Biomedical Research Unit, Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK
| | - Elena Miranda
- Department of Biology and Biotechnologies "Charles Darwin" and Pasteur Institute-Cenci Bolognetti Foundation, Sapienza University of Rome, Rome, Italy
| | - Elena V Orlova
- Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, University of London, London WC1E 7HX, UK
| | - James A Irving
- UCL Respiratory, University College London, 5 University Street, London WC1E 6JF, UK.
- Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BN, UK
| | - David A Lomas
- UCL Respiratory, University College London, 5 University Street, London WC1E 6JF, UK.
- Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BN, UK
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9
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Alpha 1-Antitrypsin Deficiency: A Disorder of Proteostasis-Mediated Protein Folding and Trafficking Pathways. Int J Mol Sci 2020; 21:ijms21041493. [PMID: 32098273 PMCID: PMC7073043 DOI: 10.3390/ijms21041493] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 02/17/2020] [Accepted: 02/19/2020] [Indexed: 12/30/2022] Open
Abstract
Human cells express large amounts of different proteins continuously that must fold into well-defined structures that need to remain correctly folded and assemble in order to ensure their cellular and biological functions. The integrity of this protein balance/homeostasis, also named proteostasis, is maintained by the proteostasis network (PN). This integrated biological system, which comprises about 2000 proteins (chaperones, folding enzymes, degradation components), control and coordinate protein synthesis folding and localization, conformational maintenance, and degradation. This network is particularly challenged by mutations such as those found in genetic diseases, because of the inability of an altered peptide sequence to properly engage PN components that trigger misfolding and loss of function. Thus, deletions found in the ΔF508 variant of the Cystic Fibrosis (CF) transmembrane regulator (CFTR) triggering CF or missense mutations found in the Z variant of Alpha 1-Antitrypsin deficiency (AATD), leading to lung and liver diseases, can accelerate misfolding and/or generate aggregates. Conversely to CF variants, for which three correctors are already approved (ivacaftor, lumacaftor/ivacaftor, and most recently tezacaftor/ivacaftor), there are limited therapeutic options for AATD. Therefore, a more detailed understanding of the PN components governing AAT variant biogenesis and their manipulation by pharmacological intervention could delay, or even better, avoid the onset of AATD-related pathologies.
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10
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Gershenson A, Gosavi S, Faccioli P, Wintrode PL. Successes and challenges in simulating the folding of large proteins. J Biol Chem 2020; 295:15-33. [PMID: 31712314 PMCID: PMC6952611 DOI: 10.1074/jbc.rev119.006794] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Computational simulations of protein folding can be used to interpret experimental folding results, to design new folding experiments, and to test the effects of mutations and small molecules on folding. However, whereas major experimental and computational progress has been made in understanding how small proteins fold, research on larger, multidomain proteins, which comprise the majority of proteins, is less advanced. Specifically, large proteins often fold via long-lived partially folded intermediates, whose structures, potentially toxic oligomerization, and interactions with cellular chaperones remain poorly understood. Molecular dynamics based folding simulations that rely on knowledge of the native structure can provide critical, detailed information on folding free energy landscapes, intermediates, and pathways. Further, increases in computational power and methodological advances have made folding simulations of large proteins practical and valuable. Here, using serpins that inhibit proteases as an example, we review native-centric methods for simulating the folding of large proteins. These synergistic approaches range from Gō and related structure-based models that can predict the effects of the native structure on folding to all-atom-based methods that include side-chain chemistry and can predict how disease-associated mutations may impact folding. The application of these computational approaches to serpins and other large proteins highlights the successes and limitations of current computational methods and underscores how computational results can be used to inform experiments. These powerful simulation approaches in combination with experiments can provide unique insights into how large proteins fold and misfold, expanding our ability to predict and manipulate protein folding.
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Affiliation(s)
- Anne Gershenson
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003; Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, Massachusetts 01003.
| | - Shachi Gosavi
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore-560065, India.
| | - Pietro Faccioli
- Dipartimento di Fisica, Universitá degli Studi di Trento, 38122 Povo (Trento), Italy; Trento Institute for Fundamental Physics and Applications, 38123 Povo (Trento), Italy.
| | - Patrick L Wintrode
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201.
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11
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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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12
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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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13
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Krishnan B, Hedstrom L, Hebert DN, Gierasch LM, Gershenson A. Expression and Purification of Active Recombinant Human Alpha-1 Antitrypsin (AAT) from Escherichia coli. Methods Mol Biol 2017; 1639:195-209. [PMID: 28752459 DOI: 10.1007/978-1-4939-7163-3_19] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Well-established genetic manipulation procedures along with a fast doubling time, the ability to grow in inexpensive media, and easy scaleup make Escherichia coli (E. coli) a preferred recombinant protein expression platform. Human alpha-1 antitrypsin (AAT) and other serpins are easily expressed in E. coli despite their metastability and complicated topology. Serpins can be produced as soluble proteins or aggregates in inclusion bodies, and both forms can be purified to homogeneity. In this chapter, we describe an ion-exchange chromatography-based protocol that we have developed involving the use of two anion-exchange columns to purify untagged human AAT from E. coli. We also outline methods that can be used to determine the inhibitory activity of both AAT in cell lysates and purified AAT. Our protocol for the purification of bacterially expressed AAT yields pure and active protein at 6-7 mg/l culture.
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Affiliation(s)
- Beena Krishnan
- G.N. Ramachandran Protein Centre, CSIR-Institute of Microbial Technology, Sector 39-A, Chandigarh, 160 036, India.
| | - Lizbeth Hedstrom
- Department of Biology, Brandeis University Waltham, Waltham, MA, USA.,Department of Chemistry, Brandeis University Waltham, Waltham, MA, USA
| | - Daniel N Hebert
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Lila M Gierasch
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA.,Department of Chemistry, University of Massachusetts Amherst, Amherst, MA, USA
| | - Anne Gershenson
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
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14
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Trelle MB, Pedersen S, Østerlund EC, Madsen JB, Kristensen SR, Jørgensen TJD. An Asymmetric Runaway Domain Swap Antithrombin Dimer as a Key Intermediate for Polymerization Revealed by Hydrogen/Deuterium-Exchange Mass Spectrometry. Anal Chem 2016; 89:616-624. [PMID: 27783482 DOI: 10.1021/acs.analchem.6b02518] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Antithrombin deficiency is associated with increased risk of venous thrombosis. In certain families, this condition is caused by pathogenic polymerization of mutated antithrombin in the blood. To facilitate future development of pharmaceuticals against antithrombin polymerization, an improved understanding of the polymerogenic intermediates is crucial. However, X-ray crystallography of these intermediates is severely hampered by the difficulty in obtaining well-diffracting crystals of transient and heterogeneous noncovalent protein assemblies. Furthermore, their large size prohibits structural analysis by NMR spectroscopy. Here, we show how hydrogen/deuterium-exchange mass spectrometry (HDX-MS) provides detailed insight into the structural dynamics of each subunit in a polymerization-competent antithrombin dimer. Upon deuteration, this dimer surprisingly yields bimodal isotope distributions for the majority of peptides, demonstrating an asymmetric configuration of the two subunits. The data reveal that one subunit is very dynamic, potentially intrinsically disordered, whereas the other is considerably less dynamic. The local subunit-specific deuterium uptake of this polymerization-competent dimer strongly supports a β4A-β5A β-hairpin runaway domain swap mechanism for antithrombin polymerization. HDX-MS thus holds exceptional promise as an enabling analytical technique in the efforts toward future pharmacological intervention with protein polymerization and associated diseases.
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Affiliation(s)
- Morten Beck Trelle
- Department of Biochemistry and Molecular Biology, University of Southern Denmark , Campusvej 55, 5230 Odense M, Denmark
| | - Shona Pedersen
- Department of Clinical Biochemistry, Aalborg University Hospital , Hobrovej 18, 9000 Aalborg, Denmark.,Department of Clinical Medicine, Aalborg University , Sdr. Skovvej 15, 9000 Aalborg, Denmark
| | - Eva Christina Østerlund
- Department of Biochemistry and Molecular Biology, University of Southern Denmark , Campusvej 55, 5230 Odense M, Denmark
| | - Jeppe Buur Madsen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark , Campusvej 55, 5230 Odense M, Denmark
| | - Søren Risom Kristensen
- Department of Clinical Biochemistry, Aalborg University Hospital , Hobrovej 18, 9000 Aalborg, Denmark.,Department of Clinical Medicine, Aalborg University , Sdr. Skovvej 15, 9000 Aalborg, Denmark
| | - Thomas J D Jørgensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark , Campusvej 55, 5230 Odense M, Denmark
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15
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Huang X, Zheng Y, Zhang F, Wei Z, Wang Y, Carrell RW, Read RJ, Chen GQ, Zhou A. Molecular Mechanism of Z α1-Antitrypsin Deficiency. J Biol Chem 2016; 291:15674-86. [PMID: 27246852 PMCID: PMC4957051 DOI: 10.1074/jbc.m116.727826] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Indexed: 12/14/2022] Open
Abstract
The Z mutation (E342K) of α1-antitrypsin (α1-AT), carried by 4% of Northern Europeans, predisposes to early onset of emphysema due to decreased functional α1-AT in the lung and to liver cirrhosis due to accumulation of polymers in hepatocytes. However, it remains unclear why the Z mutation causes intracellular polymerization of nascent Z α1-AT and why 15% of the expressed Z α1-AT is secreted into circulation as functional, but polymerogenic, monomers. Here, we solve the crystal structure of the Z-monomer and have engineered replacements to assess the conformational role of residue Glu-342 in α1-AT. The results reveal that Z α1-AT has a labile strand 5 of the central β-sheet A (s5A) with a consequent equilibrium between a native inhibitory conformation, as in its crystal structure here, and an aberrant conformation with s5A only partially incorporated into the central β-sheet. This aberrant conformation, induced by the loss of interactions from the Glu-342 side chain, explains why Z α1-AT is prone to polymerization and readily binds to a 6-mer peptide, and it supports that annealing of s5A into the central β-sheet is a crucial step in the serpins' metastable conformational formation. The demonstration that the aberrant conformation can be rectified through stabilization of the labile s5A by binding of a small molecule opens a potential therapeutic approach for Z α1-AT deficiency.
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Affiliation(s)
- Xin Huang
- From the Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Shanghai Jiao Tong University School of Medicine and University of Chinese Academy of Sciences, Shanghai 200025, China
| | - Ying Zheng
- the Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Chemical Biology Division of Shanghai Universities E-Institutes, Key Laboratory of Cell Differentiation and Apoptosis of the Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China, and
| | - Fei Zhang
- the Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Chemical Biology Division of Shanghai Universities E-Institutes, Key Laboratory of Cell Differentiation and Apoptosis of the Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China, and
| | - Zhenquan Wei
- the Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Chemical Biology Division of Shanghai Universities E-Institutes, Key Laboratory of Cell Differentiation and Apoptosis of the Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China, and
| | - Yugang Wang
- the Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Chemical Biology Division of Shanghai Universities E-Institutes, Key Laboratory of Cell Differentiation and Apoptosis of the Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China, and
| | - Robin W Carrell
- the Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| | - Randy J Read
- the Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| | - Guo-Qiang Chen
- From the Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Shanghai Jiao Tong University School of Medicine and University of Chinese Academy of Sciences, Shanghai 200025, China, the Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Chemical Biology Division of Shanghai Universities E-Institutes, Key Laboratory of Cell Differentiation and Apoptosis of the Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China, and
| | - Aiwu Zhou
- the Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Chemical Biology Division of Shanghai Universities E-Institutes, Key Laboratory of Cell Differentiation and Apoptosis of the Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China, and
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16
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Abstract
Although proteins generally fold to their thermodynamically most stable state, some metastable proteins populate higher free energy states. Conformational changes from metastable higher free energy states to lower free energy states with greater stability can then generate the work required to perform physiologically important functions. However, how metastable proteins fold to these higher free energy states in the cell and avoid more stable but inactive conformations is poorly understood. The serpin family of metastable protease inhibitors uses large conformational changes that are downhill in free energy to inhibit target proteases by pulling apart the protease active site. The serpin antithrombin III (ATIII) targets thrombin and other proteases involved in blood coagulation, and ATIII misfolding can thus lead to thrombosis and other diseases. ATIII has three disulfide bonds, two near the N terminus and one near the C terminus. Our studies of ATIII in-cell folding reveal a surprising, biased order of disulfide bond formation, with early formation of the C-terminal disulfide, before formation of the N-terminal disulfides, critical for folding to the active, metastable state. Early folding of the predominantly β-sheet ATIII domain in this two-domain protein constrains the reactive center loop (RCL), which contains the protease-binding site, ensuring that the RCL remains accessible. N-linked glycans and carbohydrate-binding molecular chaperones contribute to the efficient folding and secretion of functional ATIII. The inability of a number of disease-associated ATIII variants to navigate the folding reaction helps to explain their disease phenotypes.
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17
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Gershenson A, Gierasch LM, Pastore A, Radford SE. Energy landscapes of functional proteins are inherently risky. Nat Chem Biol 2014; 10:884-91. [PMID: 25325699 PMCID: PMC4416114 DOI: 10.1038/nchembio.1670] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 09/19/2014] [Indexed: 01/08/2023]
Abstract
Evolutionary pressure for protein function leads to unavoidable sampling of conformational states that are at risk of misfolding and aggregation. The resulting tension between functional requirements and the risk of misfolding and/or aggregation in the evolution of proteins is becoming more and more apparent. One outcome of this tension is sensitivity to mutation, in which only subtle changes in sequence that may be functionally advantageous can tip the delicate balance toward protein aggregation. Similarly, increasing the concentration of aggregation-prone species by reducing the ability to control protein levels or compromising protein folding capacity engenders increased risk of aggregation and disease. In this Perspective, we describe examples that epitomize the tension between protein functional energy landscapes and aggregation risk. Each case illustrates how the energy landscapes for the at-risk proteins are sculpted to enable them to perform their functions and how the risks of aggregation are minimized under cellular conditions using a variety of compensatory mechanisms.
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Affiliation(s)
- Anne Gershenson
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Lila M Gierasch
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts, USA
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Annalisa Pastore
- Department of Clinical Neurosciences, King’s College London, Denmark Hill Campus, London, UK
| | - Sheena E Radford
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Leeds, UK
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18
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Behrens MA, Sendall TJ, Pedersen JS, Kjeldgaard M, Huntington JA, Jensen JK. The shapes of Z-α1-antitrypsin polymers in solution support the C-terminal domain-swap mechanism of polymerization. Biophys J 2014; 107:1905-1912. [PMID: 25418171 PMCID: PMC4213723 DOI: 10.1016/j.bpj.2014.08.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 08/22/2014] [Accepted: 08/26/2014] [Indexed: 11/20/2022] Open
Abstract
Emphysema and liver cirrhosis can be caused by the Z mutation (Glu342Lys) in the serine protease inhibitor α1-antitrypsin (α1AT), which is found in more than 4% of the Northern European population. Homozygotes experience deficiency in the lung concomitantly with a massive accumulation of polymers within hepatocytes, causing their destruction. Recently, it was proposed that Z-α1AT polymerizes by a C-terminal domain swap. In this study, small-angle x-ray scattering (SAXS) was used to characterize Z-α1AT polymers in solution. The data show that the Z-α1AT trimer, tetramer, and pentamer all form ring-like structures in strong support of a common domain-swap polymerization mechanism that can lead to self-terminating polymers.
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Affiliation(s)
- Manja A Behrens
- Department of Chemistry, Aarhus University, Aarhus, Denmark; iNANO Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, Denmark; Division of Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden
| | - Timothy J Sendall
- Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Jan S Pedersen
- Department of Chemistry, Aarhus University, Aarhus, Denmark; iNANO Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, Denmark
| | - Morten Kjeldgaard
- Department of Molecular Biology, and Genetics, Aarhus University, Aarhus, Denmark
| | - James A Huntington
- Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Jan K Jensen
- Department of Molecular Biology, and Genetics, Aarhus University, Aarhus, Denmark; Danish-Chinese Centre for Proteases and Cancer, Aarhus University, Aarhus, Denmark.
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19
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Trelle MB, Madsen JB, Andreasen PA, Jørgensen TJD. Local Transient Unfolding of Native State PAI-1 Associated with Serpin Metastability. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201402796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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20
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Trelle MB, Madsen JB, Andreasen PA, Jørgensen TJD. Local Transient Unfolding of Native State PAI-1 Associated with Serpin Metastability. Angew Chem Int Ed Engl 2014; 53:9751-4. [DOI: 10.1002/anie.201402796] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 05/26/2014] [Indexed: 11/08/2022]
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21
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Yang L, Dinarvand P, Qureshi SH, Rezaie AR. Engineering D-helix of antithrombin in alpha-1-proteinase inhibitor confers antiinflammatory properties on the chimeric serpin. Thromb Haemost 2014; 112:164-75. [PMID: 24522239 PMCID: PMC4087087 DOI: 10.1160/th13-12-1029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 01/29/2014] [Indexed: 01/20/2023]
Abstract
Antithrombin (AT) is a heparin-binding serpin in plasma which regulates the proteolytic activity of procoagulant proteases of the clotting cascade. In addition to being an anticoagulant, AT also exhibits antiinflammatory activities when it binds to cell surface heparan sulfate proteoglycans (HSPGs) on the endothelium via its basic residues of D-helix to elicit intracellular signalling responses. By contrast to AT, α1-proteinase inhibitor (α1-PI) is a non-heparin-binding serpin that exhibits very slow reactivity with coagulation proteases and possesses no HSPG-dependent antiinflammatory properties. To determine whether the antiinflammatory signaling specificity of AT can be transferred to α1-PI, we replaced the D-helix of human α1-PI with the corresponding sequence of human AT and expressed the chimeric serpin α1-PI/D-helix) in a bacterial expression system. High molecular weight heparin bound to α1-PI/D-helix and accelerated the inhibition of thrombin by the serpin mutant by a template mechanism reminiscent of the cofactor effect of heparin on inhibition of thrombin by AT. Like AT, α1-PI/D-helix exhibited antiinflammatory properties in both cellular and animal models. Thus, α1-PI/D-helix inhibited the barrier-disruptive effect of proinflammatory cytokines and inhibited the activation of nuclear factor-κB transcription factor in lipopolysaccharide-stimulated endothelial cells by a concentration-dependent manner. Furthermore, the chimeric serpin reduced lipopolysaccharide-mediated lethality, elicited a vascular protective effect and inhibited infiltration of activated leukocytes to the peritoneal cavity of mice in an HMGB1-mediated inflammatory model. These results suggest that grafting the D-helix of AT to α1-PI confers antiinflammatory properties on the serpin and that the chimeric serpin may have therapeutic utility for treating inflammatory disorders.
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Affiliation(s)
| | | | | | - A R Rezaie
- Alireza R. Rezaie, PhD, Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, 1100 S. Grand Blvd., St. Louis, MO 63104, USA, Tel.: +1 314 977 9240, Fax: +1 314 977 9205 , E-mail:
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22
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Liu L, Werner M, Gershenson A. Collapse of a long axis: single-molecule Förster resonance energy transfer and serpin equilibrium unfolding. Biochemistry 2014; 53:2903-14. [PMID: 24749911 PMCID: PMC4020580 DOI: 10.1021/bi401622n] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 03/17/2014] [Indexed: 01/25/2023]
Abstract
The energy required for mechanical inhibition of target proteases is stored in the native structure of inhibitory serpins and accessed by serpin structural remodeling. The overall serpin fold is ellipsoidal with one long and two short axes. Most of the structural remodeling required for function occurs along the long axis, while expansion of the short axes is associated with misfolded, inactive forms. This suggests that ellipticity, as typified by the long axis, may be important for both function and folding. Placement of donor and acceptor fluorophores approximately along the long axis or one of the short axes allows single-pair Förster resonance energy transfer (spFRET) to report on both unfolding transitions and the time-averaged shape of different conformations. Equilibrium unfolding and refolding studies of the well-characterized inhibitory serpin α1-antitrypsin reveal that the long axis collapses in the folding intermediates while the monitored short axis expands. These energetically distinct intermediates are thus more spherical than the native state. Our spFRET studies agree with other equilibrium unfolding studies that found that the region around one of the β strands, s5A, which helps define the long axis and must move for functionally required loop insertion, unfolds at low denaturant concentrations. This supports a connection between functionally important structural lability and unfolding in the inhibitory serpins.
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Affiliation(s)
- Lu Liu
- Department
of Chemistry, Brandeis University, Waltham, Massachusetts 02453, United States
| | - Michael Werner
- Department
of Chemistry, Brandeis University, Waltham, Massachusetts 02453, United States
| | - Anne Gershenson
- Department
of Biochemistry and Molecular Biology, University
of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
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23
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Isolation and molecular characterization of a major hemolymph serpin from the triatomine, Panstrongylus megistus. Parasit Vectors 2014; 7:23. [PMID: 24423259 PMCID: PMC3898217 DOI: 10.1186/1756-3305-7-23] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 12/21/2013] [Indexed: 11/10/2022] Open
Abstract
Background Chagas disease kills 2.5 thousand people per year of 15 million persons infected in Latin America. The disease is caused by the protozoan, Trypanosome cruzi, and vectored by triatomine insects, including Panstrongylus megistus, an important vector in Brazil. Medicines treating Chagas disease have unpleasant side effects and may be ineffective, therefore, alternative control techniques are required. Knowledge of the T. cruzi interactions with the triatomine host needs extending and new targets/strategies for control identified. Serine and cysteine peptidases play vital roles in protozoan life cycles including invasion and entry of T. cruzi into host cells. Peptidase inhibitors are, therefore, promising targets for disease control. Methods SDS PAGE and chromatograpy detected and isolated a P. megistus serpin which was peptide sequenced by mass spectrometry. A full amino acid sequence was obtained from the cDNA and compared with other insect serpins. Reverse transcription PCR analysis measured serpin transcripts of P. megistus tissues with and without T. cruzi infection. Serpin homology modeling used the Swiss Model and Swiss-PDB viewer programmes. Results The P. megistus serpin (PMSRP1) has a ca. 40 kDa molecular mass with 404 amino acid residues. A reactive site loop contains a highly conserved hinge region but, based on sequence alignment, the normal cleavage site for serine proteases at P1-P1′ was translocated to the putative position P4′-P5′. A small peptide obtained corresponded to the C-terminal 40 amino acid region. The secondary structure of PMSRP1 indicated nine α-helices and three β-sheets, similar to other serpins. PMSRP1 transcripts occurred in all tested tissues but were highest in the fat body and hemocytes. Levels of mRNA encoding PMSRP1 were significantly modulated in the hemocytes and stomach by T. cruzi infection indicating a role for PMSRP1 in the parasite interactions with P. megistus. Conclusions For the first time, a constitutively expressed serpin has been characterized from the hemolymph of a triatomine. This opens up new research avenues into the roles of serine peptidases in the T. cruzi/P. megistus association. Initial experiments indicate a role for PMSRP1 in T. cruzi interactions with P. megistus and will lead to further functional studies of this molecule.
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Stocks BB, Sarkar A, Wintrode PL, Konermann L. Early hydrophobic collapse of α₁-antitrypsin facilitates formation of a metastable state: insights from oxidative labeling and mass spectrometry. J Mol Biol 2012; 423:789-99. [PMID: 22940366 DOI: 10.1016/j.jmb.2012.08.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 08/16/2012] [Accepted: 08/22/2012] [Indexed: 02/08/2023]
Abstract
The biologically active conformation of α₁-antitrypsin (α₁AT) and other serine protease inhibitors represents a metastable state, characterized by an exposed reactive center loop (RCL) that acts as bait for the target enzyme. The protein can also adopt an inactive "latent" conformation that has the RCL inserted as a central strand in β-sheet A. This latent form is thermodynamically more stable than the active conformation. Nonetheless, folding of α₁AT consistently yields the active state. The reasons that the metastable form is kinetically preferred remain controversial. The current work demonstrates that a carefully orchestrated folding mechanism prevents RCL insertion into sheet A. Temporal changes in solvent accessibility during folding are monitored using pulsed oxidative labeling and mass spectrometry. The data obtained in this way complement recent hydrogen/deuterium exchange results. Those hydrogen/deuterium exchange measurements revealed that securing of the RCL by hydrogen bonding of the first β-strand in sheet C is one factor that favors formation of the active conformation. The oxidative labeling data presented here reveal that this anchoring is preceded by the formation of hydrophobic contacts in a confined region of the protein. This partial collapse sequesters the RCL insertion site early on and is therefore instrumental in steering α₁AT towards its active conformation. RCL anchoring by hydrogen bonding starts to contribute at a later stage. Together, these two factors ensure that formation of the active conformation is kinetically favored. This work demonstrates how the use of complementary labeling techniques can provide insights into the mechanisms of protracted folding reactions.
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Affiliation(s)
- Bradley B Stocks
- Departments of Biochemistry and Chemistry, Western University, London, Ontario, Canada N6A 5B7
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25
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Martínez-Martínez I, Navarro-Fernández J, Aguila S, Miñano A, Bohdan N, De La Morena-Barrio ME, Ordóñez A, Martínez C, Vicente V, Corral J. The infective polymerization of conformationally unstable antithrombin mutants may play a role in the clinical severity of antithrombin deficiency. Mol Med 2012; 18:762-70. [PMID: 22481271 DOI: 10.2119/molmed.2012.00017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 03/29/2012] [Indexed: 11/06/2022] Open
Abstract
Mutations affecting mobile domains of antithrombin induce conformational instability resulting in protein polymerization that associates with a severe clinical phenotype, probably by an unknown gain of function. By homology with other conformational diseases, we speculated that these variants might infect wild-type (WT) monomers reducing the anticoagulant capacity. Infective polymerization of WT polymers and different P1 mutants (p.R425del, p.R425C and p.R425H) were evaluated by using native gels and radiolabeled WT monomers and functional assays. Human embryonic kidney cells expressing the Epstein-Barr nuclear antigen 1 (HEK-EBNA) cells expressing inducible (p.R425del) or two novel constitutive (p.F271S and p.M370T) conformational variants were used to evaluate intracellular and secreted antithrombin under mild stress (pH 6.5 and 39°C for 5 h). We demonstrated the conformational sensitivity of antithrombin London (p.R425del) to form polymers under mild heating. Under these conditions purified antithrombin London recruited WT monomers into growing polymers, reducing the anticoagulant activity. This process was also observed in the plasma of patients with p.R425del, p.R425C and p.R425H mutations. Under moderate stress, coexpression of WT and conformational variants in HEK-EBNA cells increased the intracellular retention of antithrombin and the formation of disulfide-linked polymers, which correlated with impaired secretion and reduction of anticoagulant activity in the medium. Therefore, mutations inducing conformational instability in antithrombin allow its polymerization with the subsequent loss of function, which under stress could sequestrate WT monomers, resulting in a new prothrombotic gain of function, particularly relevant for intracellular antithrombin. The in vitro results suggest a temporal and severe plasma antithrombin deficiency that may contribute to the development of the thrombotic event and to the clinical severity of these mutations.
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Affiliation(s)
- Irene Martínez-Martínez
- Department of Internal Medicine, Centro Regional de Hemodonación, University of Murcia, Murcia, Spain
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Folding mechanism of the metastable serpin α1-antitrypsin. Proc Natl Acad Sci U S A 2012; 109:4467-72. [PMID: 22392975 DOI: 10.1073/pnas.1109125109] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The misfolding of serpins is linked to several genetic disorders including emphysema, thrombosis, and dementia. During folding, inhibitory serpins are kinetically trapped in a metastable state in which a stretch of residues near the C terminus of the molecule are exposed to solvent as a flexible loop (the reactive center loop). When they inhibit target proteases, serpins transition to a stable state in which the reactive center loop forms part of a six-stranded β-sheet. Here, we use hydrogen-deuterium exchange mass spectrometry to monitor region-specific folding of the canonical serpin human α(1)-antitrypsin (α(1)-AT). We find large differences in the folding kinetics of different regions. A key region in the metastable → stable transition, β-strand 5A, shows a lag phase of nearly 350 s. In contrast, the "B-C barrel" region shows no lag phase and the incorporation of the C-terminal residues into β-sheets B and C is largely complete before the center of β-sheet A begins to fold. We propose this as the mechanism for trapping α(1)-AT in a metastable form. Additionally, this separation of timescales in the folding of different regions suggests a mechanism by which α(1)-AT avoids polymerization during folding.
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