title: Deficiency Mutations of Alpha-1 Antitrypsin. Effects on Folding, Function, and Polymerization.
abstract: Misfolding, polymerization, and defective secretion of functional alpha-1 antitrypsin underlies the predisposition to severe liver and lung disease in alpha-1 antitrypsin deficiency. We have identified a novel (Ala336Pro, Baghdad) deficiency variant and characterized it relative to the wild-type (M) and Glu342Lys (Z) alleles. The index case is a homozygous individual of consanguineous parentage, with levels of circulating alpha-1 antitrypsin in the moderate deficiency range, but is a biochemical phenotype that could not be classified by standard methods. The majority of the protein was present as functionally inactive polymer, and the remaining monomer was 37% active relative to the wild-type protein. These factors combined indicate an 85 to 95% functional deficiency, similar to that seen with ZZ homozygotes. Biochemical, biophysical, and computational studies further defined the molecular basis of this deficiency. These studies demonstrated that native Ala336Pro alpha-1 antitrypsin could populate the polymerogenic intermediate-and therefore polymerize-more readily than either wild-type alpha-1 antitrypsin or the Z variant. In contrast, folding was far less impaired in Ala336Pro alpha-1 antitrypsin than in the Z variant. The data are consistent with a disparate contribution by the "breach" region and "shutter" region of strand 5A to folding and polymerization mechanisms. Moreover, the findings demonstrate that, in these variants, folding efficiency does not correlate directly with the tendency to polymerize in vitro or in vivo. They therefore differentiate generalized misfolding from polymerization tendencies in missense variants of alpha-1 antitrypsin. Clinically, they further support the need to quantify loss-of-function in alpha-1 antitrypsin deficiency to individualize patient care.
authors.affiliation: 1 Wolfson Institute for Biomedical Research, University College London, London, United Kingdom.|2 Institute of Structural and Molecular Biology/Birkbeck, University of London, London, United Kingdom.
authors.forename: Imran
authors.initials: I
authors.lastname: Haq
authors.affiliation: 1 Wolfson Institute for Biomedical Research, University College London, London, United Kingdom.|2 Institute of Structural and Molecular Biology/Birkbeck, University of London, London, United Kingdom.
authors.forename: James A
authors.identifier: http://orcid.org/0000-0003-3204-6356
authors.initials: JA
authors.lastname: Irving
authors.affiliation: 3 London Alpha-1 Antitrypsin Deficiency Service, Royal Free Hospital, Pond Street, London, United Kingdom; and.
authors.forename: Aarash D
authors.initials: AD
authors.lastname: Saleh
authors.affiliation: 3 London Alpha-1 Antitrypsin Deficiency Service, Royal Free Hospital, Pond Street, London, United Kingdom; and.
authors.forename: Louis
authors.initials: L
authors.lastname: Dron
authors.affiliation: 1 Wolfson Institute for Biomedical Research, University College London, London, United Kingdom.
authors.forename: Gemma L
authors.initials: GL
authors.lastname: Regan-Mochrie
authors.affiliation: 1 Wolfson Institute for Biomedical Research, University College London, London, United Kingdom.|2 Institute of Structural and Molecular Biology/Birkbeck, University of London, London, United Kingdom.
authors.forename: Neda
authors.initials: N
authors.lastname: Motamedi-Shad
authors.affiliation: 3 London Alpha-1 Antitrypsin Deficiency Service, Royal Free Hospital, Pond Street, London, United Kingdom; and.
authors.forename: John R
authors.initials: JR
authors.lastname: Hurst
authors.affiliation: 2 Institute of Structural and Molecular Biology/Birkbeck, University of London, London, United Kingdom.|3 London Alpha-1 Antitrypsin Deficiency Service, Royal Free Hospital, Pond Street, London, United Kingdom; and.|4 Division of Asthma, Allergy and Lung Biology, King's College London, London, United Kingdom.
authors.forename: Bibek
authors.initials: B
authors.lastname: Gooptu
authors.affiliation: 1 Wolfson Institute for Biomedical Research, University College London, London, United Kingdom.|2 Institute of Structural and Molecular Biology/Birkbeck, University of London, London, United Kingdom.|3 London Alpha-1 Antitrypsin Deficiency Service, Royal Free Hospital, Pond Street, London, United Kingdom; and.
authors.forename: David A
authors.initials: DA
authors.lastname: Lomas
mesh_terms: D000328:Adult; D004252:DNA Mutational Analysis; D004795:Enzyme Stability; D005260:Female; D020022:Genetic Predisposition to Disease; D006720:Homozygote; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D010641:Phenotype; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D055503:Protein Multimerization; D000515:alpha 1-Antitrypsin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D019896:alpha 1-Antitrypsin Deficiency / Q000201:enzymology / Q000235:genetics*
chemical_list: C043392:SERPINA1 protein, human; D000515:alpha 1-Antitrypsin
keywords: alpha-1 antitrypsin deficiency; mutation; polymerization; serpinopathies; unfolding