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Abstract: S3-16 ABCA1 AND ABCG1 TOGETHER WITH SR-BI MODULATE APOA-I AND HDL TRANSPORT THROUGH AORTIC ENDOTHELIAL CELLS
- Post-meeting symposia - High Density Lipoproteins Abstract: S3-16 Citation: Atherosclerosis Supplement 2009, Vol. 10, Issue 2
ABCA1 AND ABCG1 TOGETHER WITH SR-BI MODULATE APOA-I AND HDL TRANSPORT THROUGH AORTIC ENDOTHELIAL CELLS L Rohrer, P Ohnsorg, A von Eckardstein Institute of Clinical Chemistry, University Hospital Zurich, Zurich Cholesterol acceptors like high density lipoproteins (HDL) and apolipoprotein A-I (apoA-I), in the reverse cholesterol transport pathway must cross the endothelium to get access to the donor cells in the arterial initima. However, it is unknown how they get translocated from the blood stream into the vascular wall. Aortic endothelial cells (ECs) cultivated on inserts bind, internalize and translocate apoA-I and HDL from the apical to the basolateral compartment in a specific, and temperature dependent manner. Binding and cell association of HDL was only competed by excess HDL not by apoA-I, albumin and liposomes. In contrast binding and cell association of apoA-I is competed by excess apoA-I and HDL and not by albumin. Both cell surface biotinylation experiments and immunofluorescence microscopy of apoA-I and HDL recovered both intracellularly. Parallel to this transport the size of the transported HDL-particle was reduced but the protein moiety remained intact, in contrast apoA-I was lipidated during this process. Using pharmacological inhibitors and RNA interference to modulate ATP binding cassette A1 (ABCA1) resulted in reduced apoA-I and not HDL cell surface binding, internalisation and transport. Moreover substituting wildtype apoA-I with apoA-I mutants unable to trigger cholesterol efflux resulted in diminished transport through ECs. In contrast knock down of SR-BI and ABCG1 reduced HDL translocation but did not affect apoA-I transport or inulin permeability. In conclusion, ECs translocate HDL and lipid-free apoA-I by distinct mechanisms involving either SR-BI and ABCG1 (HDL) or ABCA1 (apoA-I). Funding: Swiss National Research Foundation (3100A0-100693/1 and 3100A0-116404/1), and European Union (LSHM-C-2006-037631).
ABCA1 AND ABCG1 TOGETHER WITH SR-BI MODULATE APOA-I AND HDL TRANSPORT THROUGH AORTIC ENDOTHELIAL CELLS L Rohrer, P Ohnsorg, A von Eckardstein Institute of Clinical Chemistry, University Hospital Zurich, Zurich Cholesterol acceptors like high density lipoproteins (HDL) and apolipoprotein A-I (apoA-I), in the reverse cholesterol transport pathway must cross the endothelium to get access to the donor cells in the arterial initima. However, it is unknown how they get translocated from the blood stream into the vascular wall. Aortic endothelial cells (ECs) cultivated on inserts bind, internalize and translocate apoA-I and HDL from the apical to the basolateral compartment in a specific, and temperature dependent manner. Binding and cell association of HDL was only competed by excess HDL not by apoA-I, albumin and liposomes. In contrast binding and cell association of apoA-I is competed by excess apoA-I and HDL and not by albumin. Both cell surface biotinylation experiments and immunofluorescence microscopy of apoA-I and HDL recovered both intracellularly. Parallel to this transport the size of the transported HDL-particle was reduced but the protein moiety remained intact, in contrast apoA-I was lipidated during this process. Using pharmacological inhibitors and RNA interference to modulate ATP binding cassette A1 (ABCA1) resulted in reduced apoA-I and not HDL cell surface binding, internalisation and transport. Moreover substituting wildtype apoA-I with apoA-I mutants unable to trigger cholesterol efflux resulted in diminished transport through ECs. In contrast knock down of SR-BI and ABCG1 reduced HDL translocation but did not affect apoA-I transport or inulin permeability. In conclusion, ECs translocate HDL and lipid-free apoA-I by distinct mechanisms involving either SR-BI and ABCG1 (HDL) or ABCA1 (apoA-I). Funding: Swiss National Research Foundation (3100A0-100693/1 and 3100A0-116404/1), and European Union (LSHM-C-2006-037631).