CONFORMATION OF HUMAN APOLIPOPROTEIN A-I AMYLOID VARIANTS: FOLDING AND THE ROLE OF INFLAMMATION IN THE PROTEIN AGGREGATION DISEASE

M. ALEJANDRA TRICERRI.; GISONNO RA; NAHUEL A RAMELLA; SILVANA A ROSU; JUAN P. GORGOJO; GADDI, GISELLA; EDUARDO D. PRIETO; M FERNANDA CORTEZ; GUILLERMO R.SCHINELLA,; LUCRECIA M CURTO; RODRIGUEZ, M. EUGENIA

Barcelona

Simposio; XVII International Symposium on Amyloidosis; 2020

ISA

Background: The reasons that determine the pathological deposition of human apolipoprotein A-I variants inducing organ failure have been under research since the early description of natural mutations in patients. Different protein conformations may be involved in the development of clinical manifestations associated with human amyloidosis.Although a fibrillar conformation is usually the signature of damage in the tissues, it is not clear whether this species is per se the cause or the consequence of the disease. From the more than 20 amyloidogenic variants of apoA-I described1, a mutation leading to a deletion at position 107 (Lys107-0) has a unique pattern, as patients carrying this variant show amyloidosis and severe atherosclerosis.Objectives: Here we set out to characterize protein aggregation structures, and to test the hypothesis that a proinflammatory microenvironment could favor protein misfolding.Methods: Soluble, freshly folded proteins were obtained and purified. Both, Wt and Lys107-0 were oxidized under controlled concentrations of hydrogen peroxide and incubated by 30-day. Structure of soluble and incubated species was analyzed by fluorescence, circular dichroism and microscopy approaches. In order to answer whether these structures may induce cellular events associated with the chronic inflammatory scenario, we incubated apoA-I variants (either soluble oraggregated) with human neutrophils and analyzed by confocal microcopy the release of Neutrophil elastase traps (NETs).Results: Lys107-0 was more unstable, contained less α helix secondary structure (14 % vs 63% for the Wt) and showed a more flexible spatial arrangement. In addition, it had a higher tendency to aggregate and fibrils in a high yield were obtained after oxidation of this variant (which were not present for the Wt). These fibrils bound ThT, lost α helix content and were able to induce the release of Neutrophils Extracellular Traps. This effect was lower or not significant for soluble species.Conclusions: We conclude that a pro-inflammatory microenvironment could result in the formation of aggregation-prone species, which, in addition may induce a positive feed-back in the activation of an inflammatory response.References: 1. Matsunaga et al. (2010). Apolipoprotein A-I Mutations. The HDL Handbook, Chap. 7Acknowledgments: Grants (ANPCyT) PICT-2016-0849 to MAT); Universidad Nacional de La Plata (UNLP) (M187 to MAT).Keywords: amylodosis, protein folding, apolipoprotein A-I, inflammation