Evolutionary and Structural Constraints Influencing Apolipoprotein A-I Amyloid Behavior

MASSON, T; ROMANOWSKY V; GISONNO, R.; BARRERA E; TRICERRI, M. A.; RAMELLA, N.; RAMELLA, N.

buenos aires

Congreso; Encuentro conjunto de las sociedades S A I C, S A F E, S A B, SAP; 2020

Sociedad Argentina de Investigaciones clínicas

Apolipoprotein A-I has a key function in the reverse cholesterol transport mediated by the high density lipoprotein (HDL) particle. However, aggregation of apoA-I single point mutants can lead tohereditary amyloid pathology. In this work, we combined evolutionary studies, in silico saturation mutagenesis and molecular dynamics (MD) simulations to provide a comprehensive analysis of theconservation and pathogenic role of the aggregation prone regions (APRs) present in apoA-I.ApoA-I sequences analysis demonstrated the pervasive conservation of an APR, named APR1, within the N-terminal ɑ-helix bundle. Moreover, stability analysis carried out with the FoldX engineshowed that this region contributes to the marginal stability of apoA-I. When the thermodynamicand pathogenic impact of different groups of apoA-I point variants was compared, we found that mutations associated with amyloid pathologies showed a destabilizing effect when compared against HDL-deficiency or natural variants extracted from the gnomAD database (p-value 0.05, Mann-Whitney-Wilcoxon Test). MD simulations of the amyloid variant G26R evidenced an increasein the exposure of APR1 with respect to the wild type protein (p-value 0.1, Tukey?s Test) and the occurrence of β-strand secondary elements at the C-terminus of apoA-I. Our findings highlight APR1 as a relevant component for apoA-I structural integrity and emphasize a destabilizing effect of amyloid variants that leads to the exposure of this region. This information contributes to our understanding of how apoA-I, with its high degree of structural flexibility, maintains a delicate equilibrium between its lipid-binding function and its intrinsic tendency to form amyloid aggregates. In addition, our stability measurements could be used as a proxy to interpret the structural impact of new mutations affecting apoA-I.