Mutations in the SERPINA1 gene can cause alpha-1 antitrypsin deficiency (AATD), where Z (Glu342Lys) represents the most common severe mutation. The formation of ordered Z alpha-1 antitrypsin (AAT) polymers in hepatocytes is associated with liver disease and a deficiency of circulating AAT, predisposing to early onset emphysema. Current evidence suggests that the Z mutation induces a mildly perturbed intermediate conformation (M*) which likely undergoes a substantial structural rearrangement, resulting in polymers mediated by inter-molecular domain swap. The polymers formed by Z AAT, found in the plasma and within liver tissue, expose a cryptic epitope recognised by a monoclonal antibody (2C1), and their formation can be inhibited in cellular and animal models by a small molecule (c716). This molecular chaperone acts by maintaining the molecule in a monomeric state stabilising the M* intermediate. Here, we present the biochemical characterisation of naturally occurring AATD-associated mutants that do not expose the 2C1 epitope, and additionally show resistance to the activity of the molecular chaperone c716, indicating differences in structure and/or kinetics of their formation. These observations have led us to hypothesize an alternative polymerisation mechanism for these variants. Moreover, to study the formation and accumulation of such polymers, we have also generated a new monoclonal antibody capable of selectively recognising a wider range of polymers. Taken together, our data could represent an important bridge to clarify how different AAT mutations may be linked to various pathologies associated with serpin aggregation.
Characterization of alpha-1 antitrypsin mutants with an alternative polymerisation mechanism
Fra, A;Irving, J;
2024-01-01
Abstract
Mutations in the SERPINA1 gene can cause alpha-1 antitrypsin deficiency (AATD), where Z (Glu342Lys) represents the most common severe mutation. The formation of ordered Z alpha-1 antitrypsin (AAT) polymers in hepatocytes is associated with liver disease and a deficiency of circulating AAT, predisposing to early onset emphysema. Current evidence suggests that the Z mutation induces a mildly perturbed intermediate conformation (M*) which likely undergoes a substantial structural rearrangement, resulting in polymers mediated by inter-molecular domain swap. The polymers formed by Z AAT, found in the plasma and within liver tissue, expose a cryptic epitope recognised by a monoclonal antibody (2C1), and their formation can be inhibited in cellular and animal models by a small molecule (c716). This molecular chaperone acts by maintaining the molecule in a monomeric state stabilising the M* intermediate. Here, we present the biochemical characterisation of naturally occurring AATD-associated mutants that do not expose the 2C1 epitope, and additionally show resistance to the activity of the molecular chaperone c716, indicating differences in structure and/or kinetics of their formation. These observations have led us to hypothesize an alternative polymerisation mechanism for these variants. Moreover, to study the formation and accumulation of such polymers, we have also generated a new monoclonal antibody capable of selectively recognising a wider range of polymers. Taken together, our data could represent an important bridge to clarify how different AAT mutations may be linked to various pathologies associated with serpin aggregation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
