1. The molecular species responsible for α
- Author
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Riccardo, Ronzoni, Nina, Heyer-Chauhan, Annamaria, Fra, Andrew C, Pearce, Martin, Rüdiger, Elena, Miranda, James A, Irving, and David A, Lomas
- Subjects
congenital, hereditary, and neonatal diseases and abnormalities ,Polymers ,Protein Conformation ,polymer inhibitor ,food and beverages ,Antibodies, Monoclonal ,Original Articles ,digestive system diseases ,respiratory tract diseases ,Small Molecule Libraries ,secretion ,α1‐antitrypsin ,alpha 1-Antitrypsin ,alpha 1-Antitrypsin Deficiency ,Hepatocytes ,Humans ,Original Article ,folding intermediate ,polymerisation ,Molecular Chaperones - Abstract
The formation of ordered Z α1‐antitrypsin polymers is central to liver disease in α1‐antitrypsin deficiency. The nascent α1‐antitrypsin folds via the M* intermediate to native monomer or becomes incorporated into a soluble polymer that can be secreted, degraded or precipitate as insoluble inclusions. We describe the kinetics of the clearance of Z α1‐antitrypsin polymers and show that they can be abolished with a small molecule preventing the formation of M*., The formation of ordered Z (Glu342Lys) α1‐antitrypsin polymers in hepatocytes is central to liver disease in α1‐antitrypsin deficiency. In vitro experiments have identified an intermediate conformational state (M*) that precedes polymer formation, but this has yet to be identified in vivo. Moreover, the mechanism of polymer formation and their fate in cells have been incompletely characterised. We have used cell models of disease in conjunction with conformation‐selective monoclonal antibodies and a small molecule inhibitor of polymerisation to define the dynamics of polymer formation, accumulation and secretion. Pulse‐chase experiments demonstrate that Z α1‐antitrypsin accumulates as short‐chain polymers that partition with soluble cellular components and are partially secreted by cells. These precede the formation of larger, insoluble polymers with a longer half‐life (10.9 ± 1.7 h and 20.9 ± 7.4 h for soluble and insoluble polymers, respectively). The M* intermediate (or a by‐product thereof) was identified in the cells by a conformation‐specific monoclonal antibody. This was completely abrogated by treatment with the small molecule, which also blocked the formation of intracellular polymers. These data allow us to conclude that the M* conformation is central to polymerisation of Z α1‐antitrypsin in vivo; preventing its accumulation represents a tractable approach for pharmacological treatment of this condition; polymers are partially secreted; and polymers exist as two distinct populations in cells whose different dynamics have likely consequences for the aetiology of the disease.
- Published
- 2020