Conformation and microenvironment interactions of human apolipoprotein A-I variants: amyloidosis and atherosclerosis

ROSU SILVANA A.; EDUARDO D. PRIETO; NAHUEL A. RAMELLA; GADDI, G; FINARELLI, GABRIELA S.; M ALEJANDRA TRICERRI; GISONNO, ROMINA; CORTEZ, M. FERNANDA

Rosario

Encuentro; L Reunión Anual Sociedad Argentina de Biofísica; 2022

SAB

The detection of amyloid-positive stains of human apolipoprotein A-I (apoA-I) in different tissues and the chronic manifestation of symptoms in patients strongly support that the amyloid must be the consequence of the protein processing induced either by the microenvironment or elicited by natural mutations, which result in severe organ damage.Even though a fibrillar conformation is usually the signature of this disease, it is not clear whether this species is per se the cause or the consequence of the organ damage. Here we study different apoA-I conformations (APO Conf) (peptides, single point variants and oxidized conformations) with the hypothesis that the cytotoxic conformation might be induced by an alteration in the function-misfunction equilibrium.Freshly folded proteins (Wt and apoA-I single point mutants that induce amyloidosis in patients) were obtained and purified. Peptides were designed and purchased. Both, Wt and Lys107-0 (a variant associated with severe atherosclerosis) were oxidized with H202 and incubated by 30-day. Protein conformation was analyzed by fluorescence, circular dichroism and microscopy approaches. APO Conf (either soluble or aggregated) was tested in order to determine whether they might elicit a pro-inflammatory stimulus from monocytes.All the variants were more sensitive than Wt to be proteolyzed by trypsin. While short oligopeptides (6-8 amino acids) did not form amyloid-like structures neither were active in inducing a pro-inflammatory reaction of cells, a longer central region significantly boundThT after 72 h at 50 C. The oxidized Lys107-0 formed fibrils after the incubation period and induced cellular activation. We conclude that there is a close association among the environmental processing of a protein in circulation and its long- time catabolism that may result either in its misfunction or in the loss of the normal functionReferences1Matsunaga et al. (2010). Apolipoprotein A-I Mutations. The HDL Handbook, Chap.7AcknowldegmentsGrants (CONICET) PIP 11220200102381CO to MAT); ANPCyT (PICT-2019-03592 to SAR). Universidad Nacional de La Plata (UNLP) (M234 to MAT), PPID 014 to NAR. 168