title: Insights into the fate of the N-terminal amyloidogenic polypeptide of ApoA-I in cultured target cells.
abstract: Apolipoprotein A-I (ApoA-I) is an extracellular lipid acceptor, whose role in cholesterol efflux and high-density lipoprotein formation is mediated by ATP-binding cassette transporter A1 (ABCA1). Nevertheless, some ApoA-I variants are associated to systemic forms of amyloidosis, characterized by extracellular fibril deposition in peripheral organs. Heart amyloid fibrils were found to be mainly constituted by the 93-residue N-terminal fragment of ApoA-I, named [1-93]ApoA-I. In this paper, rat cardiomyoblasts were used as target cells to analyse binding, internalization and intracellular fate of the fibrillogenic polypeptide in comparison to full-length ApoA-I. We provide evidence that the polypeptide: (i) binds to specific sites on cell membrane (K(d) = 5.90 ± 0.70 × 10(-7) M), where it partially co-localizes with ABCA1, as also described for ApoA-I; (ii) is internalized mostly by chlatrin-mediated endocytosis and lipid rafts, whereas ApoA-I is internalized preferentially by chlatrin-coated pits and macropinocytosis and (iii) is rapidly degraded by proteasome and lysosomes, whereas ApoA-I partially co-localizes with recycling endosomes. Vice versa, amyloid fibrils, obtained by in vitro aggregation of [1-93]ApoA-I, were found to be unable to enter the cells. We propose that internalization and intracellular degradation of [1-93]ApoA-I may divert the polypeptide from amyloid fibril formation and contribute to the slow progression and late onset that characterize this pathology.
authors.affiliation: Department of Structural and Functional Biology, University of Naples Federico II, School of Biotechnological Sciences, Naples, Italy.
authors.forename: Angela
authors.initials: A
authors.lastname: Arciello
authors.forename: Nadia
authors.initials: N
authors.lastname: De Marco
authors.forename: Rita
authors.initials: R
authors.lastname: Del Giudice
authors.forename: Fulvio
authors.initials: F
authors.lastname: Guglielmi
authors.forename: Piero
authors.initials: P
authors.lastname: Pucci
authors.forename: Annalisa
authors.initials: A
authors.lastname: Relini
authors.forename: Daria Maria
authors.initials: DM
authors.lastname: Monti
authors.forename: Renata
authors.initials: R
authors.lastname: Piccoli
mesh_terms: D000682:Amyloid / Q000378:metabolism*; D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism*; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology; D005453:Fluorescence; D006801:Humans; D008055:Lipids; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology; D018625:Microscopy, Atomic Force; D032386:Myoblasts, Cardiac / Q000166:cytology / Q000378:metabolism*; D051381:Rats
chemical_list: D000682:Amyloid; D016632:Apolipoprotein A-I; D008055:Lipids