TY - JOUR
T1 - Scavenger receptor class B, type I, mediates selective uptake of low density lipoprotein cholesteryl ester
AU - Swarnakar, Snehasikta
AU - Temel, Ryan E.
AU - Connelly, Margery A.
AU - Azhar, Salman
AU - Williams, David L.
PY - 1999/10/15
Y1 - 1999/10/15
N2 - Scavenger receptor, class B, type I (SR-BI) is a cell-surface glycoprotein that mediates selective uptake of high density lipoprotein cholesteryl ester (CE) without the concomitant uptake and degradation of the particle. We have investigated the endocytic and selective uptake of low density lipoprotein (LDL)-CE by SR-BI using COS-7 cells transiently transfected with mouse SR-BI. Analysis of lipoprotein uptake data showed a concentration-dependent LDL-CE-selective uptake when doubly labeled LDL particles were incubated with SR-BI-expressing COS-7 cells. In contrast to vector-transfected cells, SR-BI-expressing COS-7 cells showed marked increases in LDL cell association and CE uptake by the selective uptake pathway, but only a modest increase in CE uptake by the endocytic pathway. SR-BI-mediated LDL-CE-selective uptake exceeded LDL endocytic uptake by 50- 100-fold. SR-BI-mediated LDL-CE-selective uptake was not inhibited by the proteoglycan synthesis inhibitor, p-nitrophenyl-β-D-xylopyranoside or by the sulfation inhibitor sodium chlorate, indicating that SRBI-mediated LDL-CE uptake occurs independently of LDL interaction with cell-surface proteoglycan. Analyses with subclones of Y1 adrenocortical cells showed that LDL-CE-selective uptake was proportional to the level of SR-BI expression. Furthermore, antibody directed to the extracellular domain of SR-BI blocked LDL-CE-selective uptake in adrenocortical cells. Thus, in cells that normally express SR-BI and in transfected COS-7 cells SR-BI mediates the efficient uptake of LDL-CE via the selective uptake mechanism. These results suggest that SR-BI may influence the metabolism of apoB-containing lipoproteins in vivo by mediating LDL-CE uptake into SR-BI-expressing cells.
AB - Scavenger receptor, class B, type I (SR-BI) is a cell-surface glycoprotein that mediates selective uptake of high density lipoprotein cholesteryl ester (CE) without the concomitant uptake and degradation of the particle. We have investigated the endocytic and selective uptake of low density lipoprotein (LDL)-CE by SR-BI using COS-7 cells transiently transfected with mouse SR-BI. Analysis of lipoprotein uptake data showed a concentration-dependent LDL-CE-selective uptake when doubly labeled LDL particles were incubated with SR-BI-expressing COS-7 cells. In contrast to vector-transfected cells, SR-BI-expressing COS-7 cells showed marked increases in LDL cell association and CE uptake by the selective uptake pathway, but only a modest increase in CE uptake by the endocytic pathway. SR-BI-mediated LDL-CE-selective uptake exceeded LDL endocytic uptake by 50- 100-fold. SR-BI-mediated LDL-CE-selective uptake was not inhibited by the proteoglycan synthesis inhibitor, p-nitrophenyl-β-D-xylopyranoside or by the sulfation inhibitor sodium chlorate, indicating that SRBI-mediated LDL-CE uptake occurs independently of LDL interaction with cell-surface proteoglycan. Analyses with subclones of Y1 adrenocortical cells showed that LDL-CE-selective uptake was proportional to the level of SR-BI expression. Furthermore, antibody directed to the extracellular domain of SR-BI blocked LDL-CE-selective uptake in adrenocortical cells. Thus, in cells that normally express SR-BI and in transfected COS-7 cells SR-BI mediates the efficient uptake of LDL-CE via the selective uptake mechanism. These results suggest that SR-BI may influence the metabolism of apoB-containing lipoproteins in vivo by mediating LDL-CE uptake into SR-BI-expressing cells.
UR - http://www.scopus.com/inward/record.url?scp=0033570088&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033570088&partnerID=8YFLogxK
U2 - 10.1074/jbc.274.42.29733
DO - 10.1074/jbc.274.42.29733
M3 - Article
C2 - 10514447
AN - SCOPUS:0033570088
SN - 0021-9258
VL - 274
SP - 29733
EP - 29739
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 42
ER -