1
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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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2
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Jagger AM, Waudby CA, Irving JA, Christodoulou J, Lomas DA. High-resolution ex vivo NMR spectroscopy of human Z α 1-antitrypsin. Nat Commun 2020; 11:6371. [PMID: 33311470 PMCID: PMC7732992 DOI: 10.1038/s41467-020-20147-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 11/15/2020] [Indexed: 01/18/2023] Open
Abstract
Genetic mutations predispose the serine protease inhibitor α1-antitrypsin to misfolding and polymerisation within hepatocytes, causing liver disease and chronic obstructive pulmonary disease. This misfolding occurs via a transiently populated intermediate state, but our structural understanding of this process is limited by the instability of recombinant α1-antitrypsin variants in solution. Here we apply NMR spectroscopy to patient-derived samples of α1-antitrypsin at natural isotopic abundance to investigate the consequences of disease-causing mutations, and observe widespread chemical shift perturbations for methyl groups in Z AAT (E342K). By comparison with perturbations induced by binding of a small-molecule inhibitor of misfolding we conclude that they arise from rapid exchange between the native conformation and a well-populated intermediate state. The observation that this intermediate is stabilised by inhibitor binding suggests a paradoxical approach to the targeted treatment of protein misfolding disorders, wherein the stabilisation of disease-associated states provides selectivity while inhibiting further transitions along misfolding pathways.
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Affiliation(s)
- Alistair M Jagger
- UCL Respiratory, Rayne Institute, University College London, London, WC1E 6JF, UK
- Institute of Structural and Molecular Biology, University College London and School of Crystallography, Birkbeck College, University of London, Gower Street, London, WC1E 6BT, UK
| | - Christopher A Waudby
- Institute of Structural and Molecular Biology, University College London and School of Crystallography, Birkbeck College, University of London, Gower Street, London, WC1E 6BT, UK
| | - James A Irving
- UCL Respiratory, Rayne Institute, University College London, London, WC1E 6JF, UK.
- Institute of Structural and Molecular Biology, University College London and School of Crystallography, Birkbeck College, University of London, Gower Street, London, WC1E 6BT, UK.
| | - John Christodoulou
- Institute of Structural and Molecular Biology, University College London and School of Crystallography, Birkbeck College, University of London, Gower Street, London, WC1E 6BT, UK.
| | - David A Lomas
- UCL Respiratory, Rayne Institute, University College London, London, WC1E 6JF, UK.
- Institute of Structural and Molecular Biology, University College London and School of Crystallography, Birkbeck College, University of London, Gower Street, London, WC1E 6BT, UK.
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3
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Bashir A, Hazari Y, Pal D, Maity D, Bashir S, Singh LR, Shah NN, Fazili KM. Aggregation of M3 (E376D) variant of alpha1- antitrypsin. Sci Rep 2020; 10:8290. [PMID: 32427833 PMCID: PMC7237413 DOI: 10.1038/s41598-020-64860-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 04/09/2020] [Indexed: 11/22/2022] Open
Abstract
Alpha1-antitrypsin (α1AT) is an abundant serine-protease inhibitor in circulation. It has an important role in neutralizing the neutrophil elastase activity. Different pathogenic point mutations like Z(E342K)-α1AT have been implicated in the development of liver cirrhosis and Chronic Obstructive Pulmonary Disease (COPD), the latter being a cluster of progressive lung diseases including chronic bronchitis and emphysema. M3-α1AT (376Glu > Asp) is another variant of α1AT which so far is largely being considered as normal though increased frequency of the variant has been reported in many human diseases including COPD. We also observed increased frequency of M3-α1AT in COPD cases in Kashmiri population. The frequency of heterozygous (AC) genotype in cases and controls was 58.57% and 27.61% (odds-ratio 6.53 (2.27-15.21); p < 0.0001) respectively, while homozygous CC genotype was found to be 21.42% and 6.66% (odds-ratio 10.56 (3.63-18.64); p < 0.0001) respectively. Comparative in vitro investigations that include trypsin‒antitrypsin assay, Circular Dichroism spectroscopy and dynamic light scattering performed on wild-type (M-α1AT), M3-α1AT, and Z-α1AT proteins along with the molecular dynamics simulations revealed that M3-α1AT has properties similar to Z-α1AT capable of forming aggregates of varied size. Our maiden observations suggest that M3-α1AT may contribute to the pathogenesis of COPD and other disorders by mechanisms that warrant further investigations.
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Affiliation(s)
- Arif Bashir
- UPR Signalling Laboratory, Department of Biotechnology, University of Kashmir, Srinagar, 190006, Jammu and Kashmir, India.
| | - Younis Hazari
- UPR Signalling Laboratory, Department of Biotechnology, University of Kashmir, Srinagar, 190006, Jammu and Kashmir, India
- Laboratory of Proteostasis Control and Biomedicine, Faculty of Medicine, University of Chile, Av. Independencia, 1027, Santiago, Chile
| | - Debnath Pal
- Department of Computational and Data Sciences (CDS), Indian Institute of Sciences, Bengaluru, 560012, India
| | - Dibyajyoti Maity
- Department of Computational and Data Sciences (CDS), Indian Institute of Sciences, Bengaluru, 560012, India
| | - Samirul Bashir
- UPR Signalling Laboratory, Department of Biotechnology, University of Kashmir, Srinagar, 190006, Jammu and Kashmir, India
| | | | - Naveed Nazir Shah
- Department of Chest Medicine, Govt. Medical College, Srinagar, 190001, Jammu and Kashmir, India
| | - Khalid Majid Fazili
- UPR Signalling Laboratory, Department of Biotechnology, University of Kashmir, Srinagar, 190006, Jammu and Kashmir, India.
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4
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Abstract
Serine proteinase inhibitors (serpins), typically fold to a metastable native state and undergo a major conformational change in order to inhibit target proteases. However, conformational lability of the native serpin fold renders them susceptible to misfolding and aggregation, and underlies misfolding diseases such as α1-antitrypsin deficiency. Serpin specificity towards its protease target is dictated by its flexible and solvent exposed reactive centre loop (RCL), which forms the initial interaction with the target protease during inhibition. Previous studies have attempted to alter the specificity by mutating the RCL to that of a target serpin, but the rules governing specificity are not understood well enough yet to enable specificity to be engineered at will. In this paper, we use conserpin, a synthetic, thermostable serpin, as a model protein with which to investigate the determinants of serpin specificity by engineering its RCL. Replacing the RCL sequence with that from α1-antitrypsin fails to restore specificity against trypsin or human neutrophil elastase. Structural determination of the RCL-engineered conserpin and molecular dynamics simulations indicate that, although the RCL sequence may partially dictate specificity, local electrostatics and RCL dynamics may dictate the rate of insertion during protease inhibition, and thus whether it behaves as an inhibitor or a substrate. Engineering serpin specificity is therefore substantially more complex than solely manipulating the RCL sequence, and will require a more thorough understanding of how conformational dynamics achieves the delicate balance between stability, folding and function required by the exquisite serpin mechanism of action.
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5
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Morifuji Y, Xu J, Karasaki N, Iiyama K, Morokuma D, Hino M, Masuda A, Yano T, Mon H, Kusakabe T, Lee JM. Expression, Purification, and Characterization of Recombinant Human α 1-Antitrypsin Produced Using Silkworm-Baculovirus Expression System. Mol Biotechnol 2018; 60:924-934. [PMID: 30302632 DOI: 10.1007/s12033-018-0127-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Human α1-antitrypsin (AAT) is the most abundant serine proteinase inhibitor (serpin) in the human plasma. Commercially available AAT for the medications of deficiency of α1-antitrypsin is mainly purified from human plasma. There is a high demand for a stable and low-cost supply of recombinant AAT (rAAT). In this study, the baculovirus expression vector system using silkworm larvae as host was employed and a large amount of highly active AAT was recovered from the silkworm serum (~ 15 mg/10 ml) with high purity. Both the enzymatic activity and stability of purified rAAT were comparable with those of commercial product. Our results provide an alternative method for mass production of the active rAAT in pharmaceutical use.
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Affiliation(s)
- Yoshiki Morifuji
- Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Science, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan
| | - Jian Xu
- Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Science, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan.
| | - Noriko Karasaki
- Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Science, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan
| | - Kazuhiro Iiyama
- Laboratory of Plant Pathology, Kyushu University Graduate School of Bioresource and Bioenvironmental Science, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan
| | - Daisuke Morokuma
- Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Science, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan
| | - Masato Hino
- Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Science, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan
| | - Akitsu Masuda
- Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Science, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan
| | - Takumi Yano
- Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Science, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan
| | - Hiroaki Mon
- Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Science, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan
| | - Takahiro Kusakabe
- Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Science, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan
| | - Jae Man Lee
- Laboratory of Insect Genome Science, Kyushu University Graduate School of Bioresource and Bioenvironmental Science, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan.
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6
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Khatami M, Hosseini SN, Hasannia S. Co-expression of alpha-1 antitrypsin with cytoplasmic domain of v-SNARE inPichia pastoris: Preserving biological activity of alpha-1 antitrypsin. Biotechnol Appl Biochem 2017; 65:181-187. [DOI: 10.1002/bab.1578] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 07/24/2017] [Accepted: 07/28/2017] [Indexed: 01/13/2023]
Affiliation(s)
- Maryam Khatami
- Department of Biochemistry; Faculty of Basic Science; Tarbiat Modares University; Tehran Iran
| | - Seyed Nezamedin Hosseini
- Department of Recombinant Products, Research and Production Complex; Pasteur Institute of Iran; Tehran Iran
| | - Sadegh Hasannia
- Department of Biochemistry; Faculty of Basic Science; Tarbiat Modares University; Tehran Iran
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7
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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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8
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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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9
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Hughes VA, Meklemburg R, Bottomley SP, Wintrode PL. The Z mutation alters the global structural dynamics of α1-antitrypsin. PLoS One 2014; 9:e102617. [PMID: 25181470 PMCID: PMC4151987 DOI: 10.1371/journal.pone.0102617] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 06/12/2014] [Indexed: 11/25/2022] Open
Abstract
α1-Antitrypsin (α1AT) deficiency, the most common serpinopathy, results in both emphysema and liver disease. Over 90% of all clinical cases of α1AT deficiency are caused by the Z variant in which Glu342, located at the top of s5A, is replaced by a Lys which results in polymerization both in vivo and in vitro. The Glu342Lys mutation removes a salt bridge and a hydrogen bond but does not effect the thermodynamic stability of Z α1AT compared to the wild type protein, M α1AT, and so it is unclear why Z α1AT has an increased polymerization propensity. We speculated that the loss of these interactions would make the native state of Z α1AT more dynamic than M α1AT and that this change renders the protein more polymerization prone. We have used hydrogen/deuterium exchange combined with mass spectrometry (HXMS) to determine the structural and dynamic differences between native Z and M α1AT to reveal the molecular basis of Z α1AT polymerization. Our HXMS data shows that the Z mutation significantly perturbs the region around the site of mutation. Strikingly the Z mutation also alters the dynamics of regions distant to the mutation such as the B, D and I helices and specific regions of each β-sheet. These changes in global dynamics may lead to an increase in the likelihood of Z α1AT sampling a polymerogenic structure thereby causing disease.
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Affiliation(s)
- Victoria A. Hughes
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Robert Meklemburg
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, United States of America
| | - Stephen P. Bottomley
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Patrick L. Wintrode
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, United States of America
- * E-mail:
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10
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Functional analysis of novel alpha-1 antitrypsin variants G320R and V321F. Mol Biol Rep 2014; 41:6133-41. [PMID: 24969485 DOI: 10.1007/s11033-014-3492-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 06/17/2014] [Indexed: 12/12/2022]
Abstract
Alpha-1 antitrypsin (AAT) gene is highly polymorphic, with a large number of rare variants whose phenotypic consequences often remain inconclusive. Studies addressing functional characteristics of AAT variants are of significant biomedical importance since deficiency and dysfunctionality of AAT are associated with liver and lung diseases. We report the results of the functional analysis of two naturally occurring AAT variants, G320R and V321F, previously identified in patients with lung disease. Neither of variants has been fully functionally characterized. In order to perform their functional analysis both variants were expressed in prokaryotic and eukaryotic systems and their intracellular localization, activity, stability, and polymerization were determined. The results of this study demonstrated that variants G320R and V321F have neither impaired activity against porcine pancreatic elastase nor propensity to form polymers. However, both variants had altered electrophoretic mobility and reduced thermostability when compared to M variant of the protein, indicating a slightly impaired secondary or tertiary structure.
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11
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The roles of helix I and strand 5A in the folding, function and misfolding of α1-antitrypsin. PLoS One 2013; 8:e54766. [PMID: 23382962 PMCID: PMC3558512 DOI: 10.1371/journal.pone.0054766] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 12/14/2012] [Indexed: 11/19/2022] Open
Abstract
α1-Antitrypsin, the archetypal member of the serpin superfamily, is a metastable protein prone to polymerization when exposed to stressors such as elevated temperature, low denaturant concentrations or through the presence of deleterious mutations which, in a physiological context, are often associated with disease. Experimental evidence suggests that α1-Antitrypsin can polymerize via several alternative mechanisms in vitro. In these polymerization mechanisms different parts of the molecule are proposed to undergo conformational change. Both strand 5 and helix I are proposed to adopt different conformations when forming the various polymers, and possess a number of highly conserved residues however their role in the folding and misfolding of α1-Antitrypsin has never been examined. We have therefore created a range of α1Antitypsin variants in order to explore the role of these conserved residues in serpin folding, misfolding, stability and function. Our data suggest that key residues in helix I mediate efficient folding from the folding intermediate and residues in strand 5A ensure native state stability in order to prevent misfolding. Additionally, our data indicate that helix I is involved in the inhibitory process and that both structural elements undergo differing conformational rearrangements during unfolding and misfolding. These findings suggest that the ability of α1-Antitrypsin to adopt different types of polymers under different denaturing conditions may be due to subtle conformational differences in the transiently populated structures adopted prior to the I and M* states.
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12
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Headey SJ, Pearce MC, Scanlon MJ, Bottomley SP. Blind Man’s Bluff – Elaboration of Fragment Hits in the Absence of Structure for the Development
of Antitrypsin Deficiency Inhibitors. Aust J Chem 2013. [DOI: 10.1071/ch13290] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The three pillars of rational drug design from a fragment library are an efficient screen, a robust assay, and atomic-resolution structures of the protein–ligand complexes. However, not all targets are amenable to structure determination by X-ray crystallography or NMR spectroscopy. In particular, targets involved in diseases of protein misfolding are inherently intractable. In the absence of structures, we are blind. However, the lack of structural information need not preclude the use of fragment-based approaches. The use of appropriate NMR techniques can enable us to detect the effects of protein binding on ligand resonances. In our efforts to identify compounds that affect the kinetics of α1-antitrypsin misfolding, we have used saturation transfer difference NMR spectroscopy to detect hits from mixtures of compounds in a fragment library. In the absence of structures, the initial challenge is three-fold: to (1) distinguish between binding sites; (2) evaluate the relative affinities of hits; and (3) advance them to the stage where activity can be detected in biological assays. We largely achieved these aims by the use of Carr–Purcell–Meiboom–Gill NMR competition experiments that detect differential relaxation of the ligand on protein binding.
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13
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Kass I, Knaupp A, Bottomley S, Buckle A. Conformational properties of the disease-causing Z variant of α1-antitrypsin revealed by theory and experiment. Biophys J 2012; 102:2856-65. [PMID: 22735536 PMCID: PMC3379022 DOI: 10.1016/j.bpj.2012.05.023] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2011] [Revised: 05/09/2012] [Accepted: 05/16/2012] [Indexed: 11/24/2022] Open
Abstract
The human serine protease inhibitor (serpin) α-1 antitrypsin (α1-AT) protects tissues from proteases of inflammatory cells. The most common disease-causing mutation in α1-AT is the Z-mutation (E342K) that results in an increased propensity of α1-AT to polymerize in the ER of hepatocytes, leading to a lack of secretion into the circulation. The structural consequences of this mutation, however, remain elusive. We report a comparative molecular dynamics investigation of the native states of wild-type and Z α1-AT, revealing a striking contrast between their structures and dynamics in the breach region at the top of β-sheet A, which is closed in the wild-type simulations but open in the Z form. Our findings are consistent with experimental observations, notably the increased solvent exposure of buried residues in the breach region in Z, as well as polymerization via domain swapping, whereby the reactive center loop is rapidly inserted into an open A-sheet before proper folding of the C-terminal β-strands, allowing C-terminal domain swapping with a neighboring molecule. Taken together, our experimental and simulation data imply that mutations at residue 342 that either stabilize an open form of the top of β-sheet A or increase the local flexibility in this region, may favor polymerization and hence aggregation.
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Affiliation(s)
| | | | | | - Ashley M. Buckle
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
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Yamasaki M, Sendall TJ, Pearce MC, Whisstock JC, Huntington JA. Molecular basis of α1-antitrypsin deficiency revealed by the structure of a domain-swapped trimer. EMBO Rep 2011; 12:1011-7. [PMID: 21909074 DOI: 10.1038/embor.2011.171] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Revised: 07/20/2011] [Accepted: 07/22/2011] [Indexed: 11/09/2022] Open
Abstract
α(1)-Antitrypsin (α1AT) deficiency is a disease with multiple manifestations, including cirrhosis and emphysema, caused by the accumulation of stable polymers of mutant protein in the endoplasmic reticulum of hepatocytes. However, the molecular basis of misfolding and polymerization remain unknown. We produced and crystallized a trimeric form of α1AT that is recognized by an antibody specific for the pathological polymer. Unexpectedly, this structure reveals a polymeric linkage mediated by domain swapping the carboxy-terminal 34 residues. Disulphide-trapping and antibody-binding studies further demonstrate that runaway C-terminal domain swapping, rather than the s4A/s5A domain swap previously proposed, underlies polymerization of the common Z-mutant of α1AT in vivo.
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Affiliation(s)
- Masayuki Yamasaki
- Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
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Knaupp AS, Bottomley SP. Structural change in β-sheet A of Z α(1)-antitrypsin is responsible for accelerated polymerization and disease. J Mol Biol 2011; 413:888-98. [PMID: 21945526 DOI: 10.1016/j.jmb.2011.09.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Revised: 09/07/2011] [Accepted: 09/11/2011] [Indexed: 11/26/2022]
Abstract
The presence of the Z mutation (Glu342Lys) is responsible for more than 95% of α(1)-antitrypsin (α(1)AT) deficiency cases. It leads to increased polymerization of the serpin α(1)AT during its synthesis and in circulation. It has been proposed that the Z mutation results in a conformational change within the folded state of antitrypsin that enhances its polymerization. In order to localize the conformational change, we have created two single tryptophan mutants of Z α(1)AT and analyzed their fluorescence properties. α(1)AT contains two tryptophan residues that are located in distinct regions of the molecule: Trp194 at the top of β-sheet A and Trp238 on β-sheet B. We have replaced each tryptophan residue individually with a phenylalanine in order to study the local environment of the remaining tryptophan residue in both M and Z α(1)AT. A detailed fluorescence spectroscopic analysis of each mutant was carried out, and we detected differences in the emission spectrum, the Stern-Volmer constant for potassium iodide quenching and the anisotropy of only Trp194 in Z α(1)AT compared to M α(1)AT. Our data reveal that the Z mutation results in a conformational change at the top of β-sheet A but does not affect the structural integrity of β-sheet B.
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Affiliation(s)
- Anja S Knaupp
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Clayton, Victoria 3800, Australia
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Dynamic local unfolding in the serpin α-1 antitrypsin provides a mechanism for loop insertion and polymerization. Nat Struct Mol Biol 2011; 18:222-6. [PMID: 21258324 PMCID: PMC3074950 DOI: 10.1038/nsmb.1976] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Accepted: 11/12/2010] [Indexed: 01/22/2023]
Abstract
The conformational plasticity of serine protease inhibitors (serpins) underlies both their activities as protease inhibitors and their susceptibility to pathogenic misfolding and aggregation. Here, we structurally characterize a sheet-opened state of the serpin α-1 antitrypsin (α₁AT) and show how local unfolding allows functionally essential strand insertion. Mutations in α₁AT that cause polymerization-induced serpinopathies map to the labile region, suggesting that the evolution of serpin function required sampling of high risk conformations on a dynamic energy landscape.
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Abstract
Serpins represent a diverse family of proteins that are found in a wide range of organisms and cellular locations. In order to study them, most need to be produced recombinantly, as isolation from their source is not always possible. Due to their relatively uncomplicated structure (single domain, few posttranslational modifications), the serpins are usually amenable to expression in Escherichia coli, which offers a fast and cost-effective solution for the generation of large amounts of protein. This chapter outlines the general procedures used in the expression and subsequent purification of serpins in E. coli, with a particular focus on the methods used for antitrypsin, the archetypal member of the family.
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Affiliation(s)
- Mary C Pearce
- Department of Biochemistry, Monash University, Clayton, Australia
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18
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Kaiserman D, Hitchen C, Levina V, Bottomley SP, Bird PI. Intracellular production of recombinant serpins in yeast. Methods Enzymol 2011; 501:1-12. [PMID: 22078527 DOI: 10.1016/b978-0-12-385950-1.00001-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Yeast are a valuable system for recombinant serpin production due to their ability to synthesize large amounts of heterologous gene products as well as their expression of folding chaperones and lack of endogenous serpin genes. In this chapter, we describe a method for intracellular expression of cytoplasmic serpins in the yeast Pichia pastoris. We also give details on how this system can be exploited to produce polymer-forming mutants of secretory serpins.
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Affiliation(s)
- Dion Kaiserman
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia
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Knaupp AS, Levina V, Robertson AL, Pearce MC, Bottomley SP. Kinetic Instability of the Serpin Z α1-Antitrypsin Promotes Aggregation. J Mol Biol 2010; 396:375-83. [PMID: 19944704 DOI: 10.1016/j.jmb.2009.11.048] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Revised: 11/18/2009] [Accepted: 11/19/2009] [Indexed: 11/28/2022]
Affiliation(s)
- Anja S Knaupp
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
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