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

RAMELLA, N. A; GADDI, G; SCHINELLA, G. R; FINARELLI, G; TRICERRI, M. A.; ROSU, S. A; PRIETO, E. D.; CURTO, LUCRECIA M.; GISONNO, ROMINA A.; GORGOJO, JUAN P.; CORTEZ, M. FERNANDA; RODRIGUEZ, M. EUGENIA

Tarragona

Simposio; XVII International Symposium on Amyloidosis; 2020

International Society of Amiloidosis

BackgroundThe reasons that determine the pathological deposition of human apolipoprotein A-Ivariants inducing organ failure have been under research since the early description ofnatural mutations in patients. Different protein conformations may be involved in thedevelopment of clinical manifestations associated with human amyloidosis. Although afibrillar conformation is usually the signature of damage in the tissues, it is not clearwhether this species is per se the cause or the consequence of the disease. From the morethan 20 amyloidogenic variants of apoA-I described 1 , a mutation leading to a deletion atposition 107 (Lys107-0) has a unique pattern, as patients carrying this variant showamyloidosis and severe atherosclerosis.ObjectivesHere we set out to characterize protein aggregation structures, and to test the hypothesisthat a pro-inflammatory microenvironment could favor protein misfolding.MethodsSoluble, freshly folded proteins were obtained and purified. Both, Wt and Lys107-0 wereoxidized under controlled concentrations of hydrogen peroxide and incubated by 30-day.Structure of soluble and incubated species was analyzed by fluorescence, circular dichroismand microscopy approaches. In order to answer whether these structures may inducecellular events associated with the chronic inflammatory scenario, we incubated apoA-Ivariants (either soluble or aggregated) with human neutrophils and analyzed by confocalmicrocopy the release of Neutrophil elastasa traps (NETs).ResultsLys107-0 was more unstable, contained less α helix secondary structure (14 % vs 63% forthe Wt) and showed a more flexible spatial arrangement. In addition it had a highertendency to aggregate and fibrils in a high yield were obtained after oxidation of thisvariant (which were not present for the Wt). These fibrils bound ThT, lost α helix contentand were able to induce the release of Neutrophils Extracellular Traps. This effect waslower or not significant for soluble species.ConclusionsWe conclude that a pro-inflammatory microenvironment could result in the formation ofaggregation-prone species, which, in addition may induce a positive feed-back in theactivation of an inflammatory response.References1Matsunaga et al. (2010). Apolipoprotein A-I Mutations. The HDL Handbook, Chap. 7AcknowledgmentsGrants (ANPCyT) PICT-2016-0849 to MAT); Universidad