Molecular mechanisms that determine the pathogenicity of human Apolipoprotein A-I natural amyloidogenic Variants.

ROSU; SA; RAMELLA; NA; GADDI, GM; FINARELLI; GS; PRIETO; ED; SCHINELLA, G; TRICERRI, MA

SAN MIGUEL DE TUCUMAN

Congreso; XLV REUNION DE SAB; 2016

SAB

Protein aggregation is characterized by a remarkable polymorphism and different conformations have been identified as toxic intermediates in some neurodegenerative diseases1. Amyloidosis induced by natural mutants of apolipoprotein A-I (apoA-I) depends on the protein variant and affects different organs such as heart, liver and kidney among others. In previous studies we have demonstrated that different apoA-I mutants show increased tendency to aggregate giving rise to different conformations depending on the incubation conditions 2,3. Here we constructed four natural amyloidogenic variants (Arg173Pro, Gly26Arg, Leu60Arg and Lys107-0), and compared their behavior with the protein with the wild type sequence (Wt). All the mutants are less stable and with a more flexible structure than Wt at pH 7,4, which could in part explain their aggregation tendency. While Wt does not bind heparin (as a model of Glycosamine Glycane) at this pH, Arg173Pro forms protein-heparin complexes and binds negative lipids with higher efficiency. Mild acidic pH induces a loss of the native structure, which was characterized by Atomic Force Microscopy as oligomer-like conformations. Interestingly, Gly26Arg and Arg173Pro (but not Lys107-0), elicit pro-inflammatory responses from macrophages such as Interleukin 1- beta (IL1) release, and the presence of a pro-oxidant milieu favors the yield of fiber-like species. We strongly suggest that common and specific mechanisms of amyloid cascades determine apoA-I variants` pathogenesis and that a chronic pro-inflammatory environment is either cause or consequence of protein misfolding. The knowledge of the specific pathological pathways is clue in order to apply strategies to avoid organ damage