Authentic hSAA related with AA amyloidosis: New method of purification, folding and amyloid polymorphism

• Published in: Biophysical chemistry 2024-10, Vol.313, p.107293, Article 107293
• Main Authors: Katina, Natalya, Marchenkov, Victor, Lapteva, Yulia, Balobanov, Vitalii, Ilyina, Nelly, Ryabova, Natalya, Evdokimov, Stanislav, Suvorina, Mariya, Surin, Alexey, Glukhov, Anatoly
• Format: Article
• Language: English
• Subjects: Aggregation kinetic; Amyloid; Amyloid - chemistry; Amyloid - metabolism; Amyloidosis - metabolism; Fibril morphology; Human SAA; Humans; Hydrogen-Ion Concentration; Limited proteolysis; Protein Folding; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Serum Amyloid A Protein - chemistry; Serum Amyloid A Protein - genetics; Serum Amyloid A Protein - isolation & purification; Serum Amyloid A Protein - metabolism
• ISSN: 0301-4622; 1873-4200; 1873-4200
• DOI: 10.1016/j.bpc.2024.107293

The secondary amyloidosis of humans is caused by the formation of hSAA fibrils in different organs and tissues. Until now hSAA was thought to have low amyloidogenicity in vitro and the majority of SAA aggregation experiments were done using murine protein or hSAA non-pathogenic isoforms. In this work a novel purification method for recombinant hSAA was introduced, enabling to obtain monomeric protein capable of amyloid aggregation under physiological conditions. The stability and amyloid aggregation of hSAA have been examined using a wide range of biophysical methods. It was shown that the unfolding of monomeric protein occurs through the formation of molten globule-like intermediate state. Polymorphism of hSAA amyloids was discovered to depend on the solution pH. At pH 8.5, rapid protein aggregation occurs, which leads to the formation of twisted short fibrils. Even a slight decrease of the pH to 7.8 results in delayed aggregation with the formation of long straight amyloids composed of laterally associated protofilaments. Limited proteolysis experiments have shown that full-length hSAA is involved in the formation of intermolecular interactions in both amyloid polymorphs. The results obtained, and the experimental approach used in this study can serve as a basis for further research on the mechanism of authentic hSAA amyloid formation. [Display omitted] •A new method for the purification of monomeric hSAA was developed.•The unfolding of hSAA occurs through the accumulation of the intermediate state.•hSAA forms two morphological types of amyloid fibrils under physiological conditions.•The full length hSAA forms intermolecular interactions in amyloid structure.