ATP-binding Cassette A1-mediated Lipidation of Apolipoprotein A-I Occurs at the Plasma Membrane and Not in the Endocytic Compartments

ATP-binding cassette transporter (ABC) A1 is required for the lipidation of apolipoprotein A-I to generate high density lipoprotein (HDL). This process is proposed to occur through a retro-endocytosis pathway in which apoA-I internalizes with ABCA1 and generates HDL from the endosomal compartments b...

Ausführliche Beschreibung

Gespeichert in:
Bibliographische Detailangaben
Veröffentlicht in:The Journal of biological chemistry 2008-06, Vol.283 (23), p.16178-16186
Hauptverfasser: Denis, Maxime, Landry, Yves D., Zha, Xiaohui
Format: Artikel
Sprache:eng
Schlagworte:
Online-Zugang:Volltext
Tags: Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
Beschreibung
Zusammenfassung:ATP-binding cassette transporter (ABC) A1 is required for the lipidation of apolipoprotein A-I to generate high density lipoprotein (HDL). This process is proposed to occur through a retro-endocytosis pathway in which apoA-I internalizes with ABCA1 and generates HDL from the endosomal compartments before resecretion. The aim of this study was to determine the route of apoA-I endocytosis and whether endocytosis contributes to HDL biogenesis. Using confocal microscopy, we found that internalized apoA-I only transiently colocalized with transferrin, a retro-endocytosis marker. Instead, apoA-I perfectly colocalized with a bulk phase uptake marker (fluorescein isothiocyanate-dextran) and, at later time points, with LysoTracker in several cell models including macrophages, fibroblasts, and baby hamster kidney cells. ABCA1 colocalized poorly with internalized apoA-I. To determine the contribution of internalized apoA-I to HDL biogenesis, we specifically removed apoA-I from the cell surface and analyzed the fate of internalized apoA-I. We found that 23% of cell-associated apoA-I was internalized at steady state. Of internalized apoA-I, only 20% was converted to HDL, and the rest was degraded, consistent with a lysosomal destination. We also found that apoA-I was released approximately five times faster from the plasma membrane than from the intracellular compartments. From these kinetic parameters, we estimated that ∼5.6% of apoA-I that interacts with cells is degraded and that internalized apoA-I contributes to ∼1.4% of total HDL production. We also found that blocking endocytosis with sucrose or cytochalasin D did not decrease cholesterol efflux or HDL biogenesis. We therefore conclude that the plasma membrane is the main platform where ABCA1-mediated lipidation of apoA-I occurs.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M709597200