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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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The cytoplasmic tail of human mannosidase Man1b1 contributes to catalysis-independent quality control of misfolded alpha1-antitrypsin. Proc Natl Acad Sci U S A 2020; 117:24825-24836. [PMID: 32958677 DOI: 10.1073/pnas.1919013117] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The failure of polypeptides to achieve conformational maturation following biosynthesis can result in the formation of protein aggregates capable of disrupting essential cellular functions. In the secretory pathway, misfolded asparagine (N)-linked glycoproteins are selectively sorted for endoplasmic reticulum-associated degradation (ERAD) in response to the catalytic removal of terminal alpha-linked mannose units. Remarkably, ER mannosidase I/Man1b1, the first alpha-mannosidase implicated in this conventional N-glycan-mediated process, can also contribute to ERAD in an unconventional, catalysis-independent manner. To interrogate this functional dichotomy, the intracellular fates of two naturally occurring misfolded N-glycosylated variants of human alpha1-antitrypsin (AAT), Null Hong Kong (NHK), and Z (ATZ), in Man1b1 knockout HEK293T cells were monitored in response to mutated or truncated forms of transfected Man1b1. As expected, the conventional catalytic system requires an intact active site in the Man1b1 luminal domain. In contrast, the unconventional system is under the control of an evolutionarily extended N-terminal cytoplasmic tail. Also, N-glycans attached to misfolded AAT are not required for accelerated degradation mediated by the unconventional system, further demonstrating its catalysis-independent nature. We also established that both systems accelerate the proteasomal degradation of NHK in metabolic pulse-chase labeling studies. Taken together, these results have identified the previously unrecognized regulatory capacity of the Man1b1 cytoplasmic tail and provided insight into the functional dichotomy of Man1b1 as a component in the mammalian proteostasis network.
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A Novel Small Molecule Inhibits Intrahepatocellular Accumulation of Z-Variant Alpha 1-Antitrypsin In Vitro and In Vivo. Cells 2019; 8:cells8121586. [PMID: 31817705 PMCID: PMC6953066 DOI: 10.3390/cells8121586] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 12/01/2019] [Accepted: 12/03/2019] [Indexed: 11/30/2022] Open
Abstract
Alpha 1-antitrypsin deficiency (AATD) is the most common genetic cause of liver disease in children and is associated with early-onset chronic liver disease in adults. AATD associated liver injury is caused by hepatotoxic retention of polymerized mutant alpha 1-antitrypsin molecules within the endoplasmic reticulum. Currently, there is no curative therapy for AATD. In this study, we selected small molecules with the potential to bind mutant alpha 1-antitrypsin (Z-variant) to inhibit its accumulation in hepatocytes. We used molecular docking to select candidate compounds that were validated in cell and animal models of disease. A crystal structure of polymerized alpha 1-antitrypsin molecule was used as the basis for docking 139,735 compounds. Effects of the top scoring compounds were investigated in a cell model that stably expresses Z-variant alpha 1-antitrypsin and in PiZ mice expressing Z-variant human alpha 1-antitrypsin (Z-hAAT), encoded by SERPINA1*E342K. 4′,′5-(Methylenedioxy)-2-nitrocinnamic acid was predicted to bind cleaved alpha 1-antitrypsin at the polymerization interface, and observed to co-localize with Z-hAAT, increase Z-hAAT degradation, inhibit intracellular accumulation of Z-hAAT, and alleviate liver fibrosis.
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Yokota S, Ono Y, Nakao T, Zhang P, Michalopoulos GK, Khan Z. Partial Bile Duct Ligation in the Mouse: A Controlled Model of Localized Obstructive Cholestasis. J Vis Exp 2018. [PMID: 29658929 DOI: 10.3791/56930] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In rodents, complete bile duct ligation (cBDL) of the common bile duct is an established surgical technique for studying obstructive cholestasis and bile duct proliferation. However, long-term experiments can lead to increased morbidity and mortality. In select mouse strains with underlying liver disease, meaningful comparisons can be made even with ligation of a single lobe of the liver, which can reduce animal losses and expenses. Here, we describe partial bile duct ligation (pBDL) in the mouse, in which only the left hepatic bile duct is ligated, causing biliary obstruction in the left lobe but not the remaining lobes. With careful microsurgical technique, pBDL experiments can be cost-effective, since the unligated lobe serves as an internal control to the ligated lobes, when subjected to the same conditions in the same animal. Unlike cBDL, a separate sham-operated control group is not necessary. pBDL is highly useful to directly compare localized versus systemic effects of cholestasis and other retained bile components. pBDL can also be repurposed as a novel method to investigate mechanisms related to medications and cell migration.
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Affiliation(s)
- Shinichiro Yokota
- Department of Surgery, Jichi Medical University; Department of Surgery, University of Pittsburgh School of Medicine
| | - Yoshihiro Ono
- Department of Surgery, University of Pittsburgh School of Medicine
| | - Toshimasa Nakao
- Department of Surgery, University of Pittsburgh School of Medicine
| | - Peng Zhang
- Department of Pediatrics, University of Pittsburgh School of Medicine
| | - George K Michalopoulos
- Department of Pathology, University of Pittsburgh School of Medicine; Pittsburgh Liver Research Center, University of Pittsburgh
| | - Zahida Khan
- Department of Pediatrics, University of Pittsburgh School of Medicine; Department of Pathology, University of Pittsburgh School of Medicine; Pittsburgh Liver Research Center, University of Pittsburgh; McGowan Institute for Regenerative Medicine, University of Pittsburgh;
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Cummings EE, O’Reilly LP, King DE, Silverman RM, Miedel MT, Luke CJ, Perlmutter DH, Silverman GA, Pak SC. Deficient and Null Variants of SERPINA1 Are Proteotoxic in a Caenorhabditis elegans Model of α1-Antitrypsin Deficiency. PLoS One 2015; 10:e0141542. [PMID: 26512890 PMCID: PMC4626213 DOI: 10.1371/journal.pone.0141542] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 10/10/2015] [Indexed: 12/24/2022] Open
Abstract
α1-antitrypsin deficiency (ATD) predisposes patients to both loss-of-function (emphysema) and gain-of-function (liver cirrhosis) phenotypes depending on the type of mutation. Although the Z mutation (ATZ) is the most prevalent cause of ATD, >120 mutant alleles have been identified. In general, these mutations are classified as deficient (<20% normal plasma levels) or null (<1% normal levels) alleles. The deficient alleles, like ATZ, misfold in the ER where they accumulate as toxic monomers, oligomers and aggregates. Thus, deficient alleles may predispose to both gain- and loss-of-function phenotypes. Null variants, if translated, typically yield truncated proteins that are efficiently degraded after being transiently retained in the ER. Clinically, null alleles are only associated with the loss-of-function phenotype. We recently developed a C. elegans model of ATD in order to further elucidate the mechanisms of proteotoxicity (gain-of-function phenotype) induced by the aggregation-prone deficient allele, ATZ. The goal of this study was to use this C. elegans model to determine whether different types of deficient and null alleles, which differentially affect polymerization and secretion rates, correlated to any extent with proteotoxicity. Animals expressing the deficient alleles, Mmalton, Siiyama and S (ATS), showed overall toxicity comparable to that observed in patients. Interestingly, Siiyama expressing animals had smaller intracellular inclusions than ATZ yet appeared to have a greater negative effect on animal fitness. Surprisingly, the null mutants, although efficiently degraded, showed a relatively mild gain-of-function proteotoxic phenotype. However, since null variant proteins are degraded differently and do not appear to accumulate, their mechanism of proteotoxicity is likely to be different to that of polymerizing, deficient mutants. Taken together, these studies showed that C. elegans is an inexpensive tool to assess the proteotoxicity of different AT variants using a transgenic approach.
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Affiliation(s)
- Erin E. Cummings
- Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States of America
| | - Linda P. O’Reilly
- Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States of America
| | - Dale E. King
- Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States of America
| | - Richard M. Silverman
- Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States of America
| | - Mark T. Miedel
- Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States of America
| | - Cliff J. Luke
- Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States of America
| | - David H. Perlmutter
- Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States of America
- Department of Cell Biology and Molecular Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Gary A. Silverman
- Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States of America
- Department of Cell Biology and Molecular Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- * E-mail: (SCP); (GAS)
| | - Stephen C. Pak
- Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania, United States of America
- * E-mail: (SCP); (GAS)
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Rahman MA, Mitra S, Sarkar A, Wewers MD. Alpha 1-antitrypsin does not inhibit human monocyte caspase-1. PLoS One 2015; 10:e0117330. [PMID: 25658455 PMCID: PMC4319913 DOI: 10.1371/journal.pone.0117330] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 12/22/2014] [Indexed: 11/18/2022] Open
Abstract
Background Alpha 1-antitrypsin (A1AT) is a 52 kDa serine protease inhibitor produced largely by hepatocytes but also by mononuclear phagocytes. A1AT chiefly inhibits neutrophil elastase and proteinase-3 but has also been reported to have immune modulatory functions including the ability to inhibit caspases. Its clinical availability for infusion suggests that A1AT therapy might modulate caspase related inflammation. Here we tested the ability of A1AT to modulate caspase-1 function in human mononuclear phagocytes. Methods Purified plasma derived A1AT was added to active caspase-1 in a cell-free system (THP-1 lysates) as well as added exogenously to cell-culture models and human whole blood models of caspase-1 activation. Functional caspase-1 activity was quantified by the cleavage of the caspase-1 specific fluorogenic tetrapeptide substrate (WEHD-afc) and the release of processed IL-18 and IL-1β. Results THP-1 cell lysates generated spontaneous activation of caspase-1 both by WEHD-afc cleavage and the generation of p20 caspase-1. A1AT added to this cell free system was unable to inhibit caspase-1 activity. Release of processed IL-18 by THP-1 cells was also unaffected by the addition of exogenous A1AT prior to stimulation with LPS/ATP, a standard caspase-1 activating signal. Importantly, the A1AT exhibited potent neutrophil elastase inhibitory capacity. Furthermore, A1AT complexed to NE (and hence conformationally modified) also did not affect THP-1 cell caspase-1 activation. Finally, exogenous A1AT did not inhibit the ability of human whole blood samples to process and release IL-1β. Conclusions A1AT does not inhibit human monocyte caspase-1.
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Affiliation(s)
- Mohd. Akhlakur Rahman
- Dorothy M. Davis Heart and Lung Research Institute, Department of Internal Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Wexner Medical Center, Ohio State University, Columbus, OH, United States of America
| | - Srabani Mitra
- Dorothy M. Davis Heart and Lung Research Institute, Department of Internal Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Wexner Medical Center, Ohio State University, Columbus, OH, United States of America
| | - Anasuya Sarkar
- Dorothy M. Davis Heart and Lung Research Institute, Department of Internal Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Wexner Medical Center, Ohio State University, Columbus, OH, United States of America
| | - Mark D. Wewers
- Dorothy M. Davis Heart and Lung Research Institute, Department of Internal Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Wexner Medical Center, Ohio State University, Columbus, OH, United States of America
- * E-mail:
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Guo S, Booten SL, Aghajan M, Hung G, Zhao C, Blomenkamp K, Gattis D, Watt A, Freier SM, Teckman JH, McCaleb ML, Monia BP. Antisense oligonucleotide treatment ameliorates alpha-1 antitrypsin-related liver disease in mice. J Clin Invest 2013; 124:251-61. [PMID: 24355919 DOI: 10.1172/jci67968] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 10/15/2013] [Indexed: 02/04/2023] Open
Abstract
Alpha-1 antitrypsin deficiency (AATD) is a rare genetic disease that results from mutations in the alpha-1 antitrypsin (AAT) gene. The mutant AAT protein aggregates and accumulates in the liver leading to AATD liver disease, which is only treatable by liver transplant. The PiZ transgenic mouse strain expresses a human AAT (hAAT) transgene that contains the AATD-associated Glu342Lys mutation. PiZ mice exhibit many AATD symptoms, including AAT protein aggregates, increased hepatocyte death, and liver fibrosis. In the present study, we systemically treated PiZ mice with an antisense oligonucleotide targeted against hAAT (AAT-ASO) and found reductions in circulating levels of AAT and both soluble and aggregated AAT protein in the liver. Furthermore, AAT-ASO administration in these animals stopped liver disease progression after short-term treatment, reversed liver disease after long-term treatment, and prevented liver disease in young animals. Additionally, antisense oligonucleotide treatment markedly decreased liver fibrosis in this mouse model. Administration of AAT-ASO in nonhuman primates led to an approximately 80% reduction in levels of circulating normal AAT, demonstrating potential for this approach in higher species. Antisense oligonucleotides thus represent a promising therapy for AATD liver disease.
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Pan S, Cheng X, Sifers RN. Golgi-situated endoplasmic reticulum α-1, 2-mannosidase contributes to the retrieval of ERAD substrates through a direct interaction with γ-COP. Mol Biol Cell 2013; 24:1111-21. [PMID: 23427261 PMCID: PMC3623633 DOI: 10.1091/mbc.e12-12-0886] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Endoplasmic reticulum (ER) α-1, 2-mannosidase and γ-COP contribute to a Golgi-based quality control module that facilitates the retrieval of captured ER-associated protein degradation substrates back to the ER. Endoplasmic reticulum (ER) α-1, 2-mannosidase (ERManI) contributes to ER-associated protein degradation (ERAD) by initiating the formation of degradation signals on misfolded N-linked glycoproteins. Despite its inferred intracellular location, we recently discovered that the mammalian homologue is actually localized to the Golgi complex. In the present study, the functional role of Golgi-situated ERManI was investigated. Mass spectrometry analysis and coimmunoprecipitation (co-IP) identified a direct interaction between ERManI and γ-COP, the gamma subunit of coat protein complex I (COPI) that is responsible for Golgi-to-ER retrograde cargo transport. The functional relationship was validated by the requirement of both ERManI and γ-COP to support efficient intracellular clearance of the classical ERAD substrate, null Hong Kong (NHK). In addition, site-directed mutagenesis of suspected γ-COP–binding motifs in the cytoplasmic tail of ERManI was sufficient to disrupt the physical interaction and ablate NHK degradation. Moreover, a physical interaction between NHK, ERManI, and γ-COP was identified by co-IP and Western blotting. RNA interference–mediated knockdown of γ-COP enhanced the association between ERManI and NHK, while diminishing the efficiency of ERAD. Based on these findings, a model is proposed in which ERManI and γ-COP contribute to a Golgi-based quality control module that facilitates the retrieval of captured ERAD substrates back to the ER.
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Affiliation(s)
- Shujuan Pan
- Department of Pathology, Baylor College of Medicine, Houston, TX 77030, USA
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Pan S, Huang L, McPherson J, Muzny D, Rouhani F, Brantly M, Gibbs R, Sifers RN. Single nucleotide polymorphism-mediated translational suppression of endoplasmic reticulum mannosidase I modifies the onset of end-stage liver disease in alpha1-antitrypsin deficiency. Hepatology 2009; 50:275-81. [PMID: 19444872 PMCID: PMC2705478 DOI: 10.1002/hep.22974] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
UNLABELLED Inappropriate accumulation of the misfolded Z variant of alpha1-antitrypsin in the hepatocyte endoplasmic reticulum (ER) is a risk factor for the development of end-stage liver disease. However, the genetic and environmental factors that contribute to its etiology are poorly understood. ER mannosidase I (ERManI) is a quality control factor that plays a critical role in the sorting and targeting of misfolded glycoproteins for proteasome-mediated degradation. In this study, we tested whether genetic variations in the human ERManI gene influence the age at onset of end-stage liver disease in patients homozygous for the Z allele (ZZ). We sequenced all 13 exons in a group of unrelated Caucasian ZZ transplant recipients with different age at onset of the end-stage liver disease. Homozygosity for the minor A allele at 2484G/A (refSNP ID number rs4567) in the 3'-untranslated region was prevalent in the infant ZZ patients. Functional studies indicated that rs4567(A), but not rs4567(G), suppresses ERManI translation under ER stress conditions. CONCLUSION These findings suggest that the identified single-nucleotide polymorphism can accelerate the onset of the end-stage liver disease associated with alpha1-antitrypsin deficiency and underscore the contribution of biosynthetic quality control as a modifier of genetic disease.
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Affiliation(s)
- Shujuan Pan
- Department of Pathology, Baylor College of Medicine, Houston, TX
| | - Lu Huang
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX
| | - John McPherson
- Department of Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX
| | - Donna Muzny
- Department of Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX
| | | | | | - Richard Gibbs
- Department of Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX
| | - Richard N. Sifers
- Department of Pathology, Baylor College of Medicine, Houston, TX
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX
- Department of Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX
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Ray S, Mickleborough TD, Brown JL. Comparison of the properties of rare variants of alpha1-proteinase inhibitor expressed in COS-1 cells and assessment of their potential as risk factors in human disease. Biochim Biophys Acta Mol Basis Dis 2005; 1740:390-402. [PMID: 15949707 DOI: 10.1016/j.bbadis.2005.03.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2004] [Revised: 03/03/2005] [Accepted: 03/23/2005] [Indexed: 11/30/2022]
Abstract
Among the more than 75 known variants of alpha(1)-proteinase inhibitor, a sub-population of rare, point mutations causing single amino acid replacements have been identified and classified as "at risk" alleles for development of pulmonary disease. In most cases, it is not clear how the amino acid replacements typical of these variants change the properties of the inhibitor to increase risk of disease in the affected individuals. To begin to address this question, we mutagenized a wild type alpha(1)-proteinase inhibitor cDNA to encode a panel of eight different point mutants reported to be associated with increased risk for development of pulmonary disease. These variants were then expressed in COS-l cells transiently transfected with plasmids containing the altered cDNAs. The effects of the mutations on the rates of secretion, cellular location, intracellular degradation, activity, stability, and tendency to aggregate were determined. Results of these studies show that, in some cases, the mutations affect the rate of secretion, the activity or both of these properties of alpha(1)-proteinase inhibitor in a manner consistent with its designation as an "at-risk" allele. In other cases, the mutations do not significantly change the properties of the inhibitor, suggesting that these may be normal variants and that their expression may not increase the risk of disease.
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Affiliation(s)
- Shahla Ray
- Department of Applied Health Science, Indiana University, Bloomington, 47405-4401, USA.
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Oh YW, Kang EY, Lee NJ, Suh WH, Godwin JD. Thoracic manifestations associated with advanced liver disease. J Comput Assist Tomogr 2000; 24:699-705. [PMID: 11045688 DOI: 10.1097/00004728-200009000-00006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Advanced liver disease and portal hypertension may produce various intrathoracic complications that involve the pleural space, lung parenchyma, and pulmonary circulation. Dyspnea and arterial hypoxemia are the common clinical symptoms and signs in patients with such complications. In these patients, intrathoracic complications most often develop during the course of hepatic disease, but a few patients may be seen first with respiratory symptoms or radiographic abnormalities. Therefore, radiologists should be made aware of these disorders that occur in patients with chronic liver disease. In this article, the authors describe and illustrate the clinical and imaging spectrum of thoracic abnormalities associated with advanced liver disease and portal hypertension.
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Affiliation(s)
- Y W Oh
- Department of Diagnostic Radiology, Korea University College of Medicine, Seoul, South Korea.
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Liu Y, Choudhury P, Cabral CM, Sifers RN. Intracellular disposal of incompletely folded human alpha1-antitrypsin involves release from calnexin and post-translational trimming of asparagine-linked oligosaccharides. J Biol Chem 1997; 272:7946-51. [PMID: 9065464 DOI: 10.1074/jbc.272.12.7946] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Protection of lung elastin fibers from proteolytic destruction is compromised by inefficient secretion of incompletely folded allelic variants of human alpha1-antitrypsin from hepatocytes. Pulse-chase radiolabeling with [35S]methionine and sucrose gradient sedimentation and coimmunoprecipitation techniques were employed to investigate quality control of human alpha1-antitrypsin secretion from stably transfected mouse hepatoma cells. The secretion-incompetent variant null(Hong Kong) (Sifers, R. N., Brashears-Macatee, S., Kidd, V. J., Muensch, H., and Woo, S. L. C. (1988) J. Biol. Chem. 263, 7330-7335) cannot fold into a functional conformation and was quantitatively associated with the molecular chaperone calnexin following biosynthesis. Assembly with calnexin required cotranslational trimming of glucose from asparagine-linked oligosaccharides. Intracellular disposal of pulse-radiolabeled molecules coincided with their release from calnexin. Released monomers and intracellular disposal were nonexistent in cells chased with cycloheximide, an inhibitor of protein synthesis. Post-translational trimming of asparagine-linked oligosaccharides and intracellular disposal were abrogated by 1-deoxymannojirimycin, an inhibitor of alpha-mannosidase activity, without affecting the monomer population. The data are consistent with a recently proposed quality control model (Hammond, C., Braakman, I., and Helenius, A. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 913-917) in which intracellular disposal requires dissociation from calnexin and post-translational trimming of mannose from asparagine-linked oligosaccharides.
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Affiliation(s)
- Y Liu
- Department of Pathology, Section of Molecular Pathobiology, Baylor College of Medicine, Houston, Texas 77030, USA
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Krowka MJ. Recent pulmonary observations in alpha 1-antitrypsin deficiency, primary biliary cirrhosis, chronic hepatitis C, and other hepatic problems. Clin Chest Med 1996; 17:67-82. [PMID: 8665791 DOI: 10.1016/s0272-5231(05)70299-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Patients with metabolic, immunologic, viral, and other types of hepatic disorders can have a spectrum of complicating pulmonary abnormalities. The natural history of these associations is poorly understood. Significant reversibility in hepatic and pulmonary dysfunction, however, has been well documented in the era of organ transplantation. The continued relationship among pulmonologists, hepatologists, and transplant surgeons hopefully will provide enlightening data on these interesting clinical associations, their natural histories, and their response to evolving therapeutic approaches.
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Affiliation(s)
- M J Krowka
- Mayo Medical School, Mayo Clinic Jacksonville, Florida, USA
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14
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Khokha R, Martin DC, Fata JE. Utilization of transgenic mice in the study of matrix degrading proteinases and their inhibitors. Cancer Metastasis Rev 1995; 14:97-111. [PMID: 7554034 DOI: 10.1007/bf00665794] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The extracellular matrix (ECM) acts as both a structural scaffold and an informational medium. Its dynamic status is determined by cells that secrete its constituent molecules and, in most cases, also secrete enzymes that catalyze degradation of these molecules. A stasis between ECM degrading enzymes and their inhibitors maintains the integrity of the matrix. While controlled ECM remodelling is fundamental to several normal processes, uncontrolled disruption underlies diverse pathological conditions. Transgenic mice with specific modulations or a total lack of expression of certain metalloproteinases, serine proteinases or their inhibitors have been generated to elucidate endogenous expression patterns, identify regulatory elements of these genes, and study the physiological consequences of their deregulated expression. With these models we enhance our understanding of the role of proteinases and their inhibitors in diverse normal processes and pathologies including mammary gland development, hemostasis, emphysema and cancer.
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Affiliation(s)
- R Khokha
- Department of Oncology, University of Western Ontario, London Regional Cancer Centre, Canada
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15
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Sifers RN. Defective protein folding as a cause of disease. NATURE STRUCTURAL BIOLOGY 1995; 2:355-7. [PMID: 7664089 DOI: 10.1038/nsb0595-355] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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16
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17
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Association between calnexin and a secretion-incompetent variant of human alpha 1-antitrypsin. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37316-7] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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18
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Egea G, Francí C, Gambús G, Lesuffleur T, Zweibaum A, Real FX. cis-Golgi resident proteins and O-glycans are abnormally compartmentalized in the RER of colon cancer cells. J Cell Sci 1993; 105 ( Pt 3):819-30. [PMID: 7691849 DOI: 10.1242/jcs.105.3.819] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neoplastic transformation is commonly associated with altered glycosylation of proteins and lipids. To understand the basis for altered mucin glycosylation, we have examined the distribution of RER markers, a cis-Golgi resident protein, and the GalNAc alpha-O-Ser/Thr epitope (Tn) in human colon cancer cells and in normal colon. In cultured mucin-producing colon cancer cells, Gal-NAc alpha-O-Ser/Thr was found in mucin droplets and in RER cisternae. In addition, the Golgi apparatus was disorganized in a proportion of cells and a 130 kDa cis-Golgi resident protein was also abnormally redistributed to the RER. The distribution of the MUC2 intestinal apomucin, protein disulphide isomerase, Gal-NAc alpha-O-Ser/Thr, and the 130 kDa cis-Golgi resident protein was analysed in normal colon and in colon cancer tissues. In normal colon, MUC2 apomucin and protein disulphide isomerase were located in the RER, whereas the cis-Golgi resident protein and GalNAc alpha-O-Ser/Thr were detected only in the cis-Golgi compartment. In contrast, the two Golgi markers colocalized with the MUC2 apomucin and protein disulphide isomerase in the RER of colon cancer cells. On the basis of these results, we propose that in colon cancer cells a redistribution of molecules normally present in the Golgi apparatus takes place; this alteration may contribute to the abnormal glycosylation of proteins and lipids associated with neoplastic transformation.
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Affiliation(s)
- G Egea
- Departament d'Immunologia, Institut Municipal d'Investigació Mèdica, Barcelona, Spain
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19
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Ciliberto G, Colantuoni V, De Francesco R, De Simone V, Monaci P, Nicosia A, Ramji DP, Toniatti C, Cortese R. Transcriptional Control of Gene Expression in Hepatic Cells. Gene Expr 1993. [DOI: 10.1007/978-1-4684-6811-3_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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20
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In vitro expression of thyroxine-binding globulin (TBG) variants. Impaired secretion of TBGPRO-227 but not TBGPRO-113. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)49669-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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21
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22
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Janssen OE, Bertenshaw R, Takeda K, Weiss R, Refetoff S. Molecular basis of inherited thyroxine-binding globulin defects. Trends Endocrinol Metab 1992; 3:49-53. [PMID: 18407078 DOI: 10.1016/1043-2760(92)90043-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Thyroxine-binding globulin (TBG) is a liver glycoprotein that transports thyroid hormones in serum. Inherited TBG defects appear as partial or complete deficiency and TBG excess. Sequencing of the TBG gene located on the X-chromosome has revealed nucleotide substitutions in partial TBG deficiency, and substitutions or deletions in complete deficiency variants. Whereas the deduced changes of the primary structure of the protein have been sufficient to explain the observed alterations of properties in some of the TBG variants, this has not been the case in other inherited TBG defects studied at the gene level. Further analysis of these and other variants may provide helpful information on glycoprotein synthesis and processing and on protein-hormone interaction.
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Affiliation(s)
- O E Janssen
- Department of Medicine, University of Chicago, Chicago, IL 60637, USA
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23
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Hart D. Regulation of plasminogen activators in connective tissues: Potential for thrombolytic therapy in collagen-vascular diseases. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/0268-9499(92)90093-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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24
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Li P, Janssen OE, Takeda K, Bertenshaw RH, Refetoff S. Complete thyroxine-binding globulin (TBG) deficiency caused by a single nucleotide deletion in the TBG gene. Metabolism 1991; 40:1231-4. [PMID: 1943753 DOI: 10.1016/0026-0495(91)90221-h] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Thyroxine-binding globulin (TBG) is the major thyroid hormone transport protein. Several inherited TBG variants resulting in partial and complete TBG deficiency have been shown to be caused by one or two nucleotide replacements in the coding regions of the TBG gene. Each manifests as a different change in the physical properties and/or biological function of the mature TBG protein. We now report sequencing of the entire coding region and exon-intron junctions of a TBG allele of a subject with inherited complete TBG deficiency, previously classified as TBG-CD6. A single nucleotide deletion was found in the codon for amino acid 165 of the normal TBG molecule. The shift in the reading frame due to this nucleotide deletion results in downstream encoding of two different amino acids followed by an early stop codon. This results in a mature protein of only 167 residues, as compared with the normal 395. Nine members of the TBG-CD6 family were tested for the presence of this mutation by allele-specific amplification. Seven of them were found to be carriers of the defect, with five hemizygous subjects manifesting complete TBG deficiency. The mutant allele correlated with the results of TBG analysis in serum. This defect was not present in affected subjects of any of seven unrelated families with complete TBG deficiency tested.
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Affiliation(s)
- P Li
- Departments of Medicine and Pediatrics, University of Chicago, IL 60637
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25
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Birrer P, McElvaney NG, Chang-Stroman LM, Crystal RG. Alpha 1-antitrypsin deficiency and liver disease. J Inherit Metab Dis 1991; 14:512-25. [PMID: 1749216 DOI: 10.1007/bf01797921] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Alpha 1-antitrypsin (alpha 1AT) deficiency, one of the most common lethal hereditary disorders among Caucasians, is associated with emphysema in adults, while in children it is associated with liver disease. Produced in the liver and released into the plasma, alpha 1AT serves as the body's major inhibitor of neutrophil elastase, a powerful proteolytic enzyme capable of degrading extracellular structural proteins. The pathogenesis of the liver disease associated with alpha 1AT deficiency is not as well understood, but is clearly linked to specific mutations in coding exons of the alpha 1AT gene, and the resulting accumulation of alpha 1AT within hepatocytes. At present, therapy for the liver disease associated with alpha 1AT deficiency is symptomatic, with liver transplantation as a last resort. New strategies are being developed to suppress the accumulation of alpha 1AT by transferring the normal gene into the liver.
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Affiliation(s)
- P Birrer
- Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
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26
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Graham KS, Le A, Sifers RN. Accumulation of the insoluble PiZ variant of human alpha 1-antitrypsin within the hepatic endoplasmic reticulum does not elevate the steady-state level of grp78/BiP. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(17)30527-6] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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27
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Intracellular degradation of the transport-impaired human PiZ alpha 1-antitrypsin variant. Biochemical mapping of the degradative event among compartments of the secretory pathway. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(18)77448-6] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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