ATP-Binding cassette transporter A1 modulates apolipoprotein A-I transcytosis through aortic endothelial cells.
High-density lipoproteins and their major protein constituent apolipoprotein A-I (apoA-I) possess diverse atheroprotective properties. Most of them must be exerted within the arterial wall. Actually, high-density lipoproteins are the most abundant lipoproteins within the arterial intima. We have recently reported that apoA-I is transcytosed through aortic endothelial cells. In the present study, we evaluate the role of ATP-binding cassette transporter A1 (ABCA1) and scavenger receptor BI (SR-BI) in this process. Using pharmacological interventions and RNA interference, we investigated whether ABCA1 and SR-BI modulate apoA-I binding, internalization and transcytosis in endothelial cells. Upregulation of ABCA1 with oxysterols increased apoA-I binding and internalization. Trapping ABCA1 on the cell surface with cyclosporin A enhanced apoA-I binding but decreased its internalization and transcytosis. In addition, apoA-I binding, internalization, and transcytosis were reduced by at least 50% after silencing ABCA1 but not after knocking down SR-BI. The integrity of the endothelial cell monolayer was affected neither by cyclosporin A treatment nor by ABCA1 silencing, as controlled by measuring inulin permeability. Finally, in ABCA1-GFP-expressing cells, fluorescently labeled apoA-I colocalized intracellularly with ABCA1-GFP. However, apoA-I-containing vesicles did not colocalize with the late endosome marker LAMP-1 (lysosome-associated membrane protein-1). In conclusion, ABCA1, but not SR-BI, modulates the transcytosis of apoA-I through endothelial cells.
Cavelier
Clara
C
Institute of Clinical Chemistry, University Hospital of Zurich and Center for Integrative Human Biology, University of Zurich, Raemistrasse 100, CH-8091 Zurich, Switzerland.
Rohrer
Lucia
L
von Eckardstein
Arnold
A
D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism*; D001692:Biological Transport; D018955:CD36 Antigens / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D002417:Cattle; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D016632:Apolipoprotein A-I; D018955:CD36 Antigens; D034741:RNA, Small Interfering