Localization and regulation of SR-BI in membrane rafts of HepG2 cells

Rhainds, David; Bourgeois, P.; Bourret, Geneviève; Huard, Karine; Falstrault, Louise; Brissette, Louise

doi:10.1242/jcs.01182

Cited by 89 publications

(54 citation statements)

References 73 publications

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“…6), which is closely associated with lipid rafts on plasma membranes (51-53). SR-BI can mediate the selective uptake of cholesteryl esters from both LDL and HDL particles, but these processes are affected differently by the integrity of lipid rafts on hepatocyte membranes (51). This effect might explain why there is a reduction of HDL-cholesterol and an induction of non-HDL-cholesterol (Table 1, Fig.…”

Section: Discussionmentioning

confidence: 99%

Adenovirus-mediated overexpression of sphingomyelin synthases 1 and 2 increases the atherogenic potential in mice

Dong

Liu

Lou

et al. 2006

Journal of Lipid Research

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Sphingomyelin synthase 1 (SMS1) and SMS2 are two isoforms of SMS, the last enzyme for sphingomyelin (SM) biosynthesis. To evaluate the role of SMS in vivo in terms of plasma lipoprotein metabolism, we generated recombinant adenovirus vectors containing human SMS1 cDNA (AdV-SMS1), SMS2 cDNA (AdV-SMS2), or the reporter LacZ cDNA (AdV-LacZ) as a control. On day 7 after intravenous infusion of 2 3 10 11 particles of both AdV-SMS1 and AdV-SMS2 into mice, liver SMS1 and SMS2 mRNA levels as well as SMS activity were significantly increased (2.5-, 2.7-, 2.1-, and 2.3-fold, respectively; P , 0.001). Lipoprotein analysis indicated that AdV-SMS1 and AdV-SMS2 treatment caused no changes of total SM and cholesterol levels but significantly decreased HDL-SM and HDL-cholesterol (42% and 38%, and 27% and 25%, respectively; P , 0.05). It also significantly increased non-HDL-SM and non-HDLcholesterol levels (50% and 35%, and 64% and 61%, respectively; P , 0.05) compared with AdV-LacZ controls. SDS--PAGE showed a significant increase in apolipoprotein B (apoB; P , 0.01) but no changes in apoA-I levels. Moreover, we found that non-HDL from both AdV-SMS1-and AdV-SMS2-treated mice was significantly aggregated after treatment with a mammalian sphingomyelinase, whereas lipoproteins from control animals did not aggregate. To investigate the mechanism of HDL changes, we measured liver scavenger receptor class B type I (SR-BI) levels by Western blot. We found that AdV-SMS1 and AdV-SMS2 mouse liver homogenates contained 50% and 55% higher SR-BI levels than in controls, whereas no change was observed in hepatic ABCA1 levels. An HDL turnover study revealed an increase of plasma clearance rates for ]HDL in both AdV-SMS1 and AdV-SMS2 mice compared with controls. In conclusion, adenovirus-mediated SMS1 and SMS2 overexpression increased lipoprotein atherogenic potential. Such an effect may contribute to the increased plasma SM levels observed in animal models of atherosclerosis and in human patients with coronary artery disease.-Dong, J., J.

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Section: Discussionmentioning

confidence: 99%

Adenovirus-mediated overexpression of sphingomyelin synthases 1 and 2 increases the atherogenic potential in mice

Dong

Liu

Lou

et al. 2006

Journal of Lipid Research

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“…Several studies have shown that HDL is internalized by a number of different cell types in an SR-BI-dependent manner (29,(32)(33)(34)(35)(36). This has led to an alternative model for selective CE uptake, in which HDL particles undergo lipid transfer during SR-BI-dependent internalization, sorting, and resecretion (32,33).…”

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confidence: 99%

Quantitative analysis of SR-BI-dependent HDL retroendocytosis in hepatocytes and fibroblasts

Sun

Eckhardt

Shetty

et al. 2006

Journal of Lipid Research

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Previous studies have suggested that HDL retroendocytosis may play a role in scavenger receptor class B type I (SR-BI)-dependent selective lipid uptake in a cellspecific manner. To investigate this possibility, we developed methods to quantitatively measure HDL uptake and resecretion in fibroblast (COS-7) and hepatocyte (HepG2) cells expressing exogenous SR-BI. Approximately 17% and 24% of HDL associated in an SR-BI-dependent manner with COS-7 and HepG2 cells, respectively, accumulates intracellularly after a 10 min incubation. To determine whether this intracellular HDL undergoes retroendocytosis, we developed a pulse-chase assay whereby internalized biotinylated 125 I-HDL 3 secreted from cells is quantitatively precipitated from cell supernatants using immobilized streptavidin. Our results show a rapid secretion of a portion of intracellular HDL from both cell types (representing 4-7% of the total cell-associated HDL) that is almost complete within 30 min (half-life z 10 min). In COS-7 cells, the calculated rate of HDL secretion (z0.5 ng HDL/mg/min) was .30-fold slower than the rate of SR-BI-dependent selective cholesteryl ester (CE) uptake (z17 ng HDL/mg/min), whereas the rate of release of HDL from the cell surface (z19 ng HDL/ mg/min) was similar to the rate of selective CE uptake. Notably, the rate of SR-BI-dependent HDL resecretion in COS-7 and HepG2 cells was similar. BLT1, a compound that inhibits selective CE uptake, does not alter the amount of SR-BI-mediated HDL retroendocytosis in COS-7 cells. From these data, we conclude that HDL retroendocytosis in COS-7 and HepG2 cells is similar and that the vast majority of SR-BI-dependent selective uptake occurs at the cell surface in both cell types.-Sun, B., E. R. M. Eckhardt, S. Shetty, D. R. van der Westhuyzen, and N. R. Webb. Quantitative analysis of SR-BI-dependent HDL retroendocytosis in hepatocytes and fibroblasts. J. Lipid Res. 2006. 47: 1700-1713.Supplementary key words selective cholesteryl ester uptake . biotinylation . scavenger receptor class B type I Abundant evidence has established that scavenger receptor class B type I (SR-BI) plays a primary role in HDL metabolism by mediating selective cholesteryl ester (CE) uptake, a process in which HDL CE is taken up without intracellular apolipoprotein degradation (1). In addition to mediating the selective uptake of HDL CE, SR-BI also plays a role in facilitating the bidirectional flux of unesterified cholesterol between cells and extracellular acceptors (2-4). SR-BI has a large extracellular loop (z400 residues), two transmembrane domains, and two short cytoplasmic tails at its N and C termini (5). SR-BI is highly expressed in liver and steroidogenic tissues, which are known to be major sites for selective lipid uptake. SR-BI is also expressed in other cells such as macrophages (6, 7), intestinal cells (8-10), and endothelial cells (11-13). Although SR-BI is best known as a physiological HDL receptor, it also binds other lipoprotein ligands, such as LDL, oxidized LDL, and acetylated LDL (1, 1...

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“…[38][39][40] In addition, HepG2 cells have been shown to express high levels of HDL receptors that mediate selective uptake of cholesteryl esters (SR-BI) or holoparticle endocytosis (mitochondrial β chain of ATP synthase/P2Y13). 41,42 In the present study, the two Gd-labeled HDL nanoparticles were found to have different uptake properties. The uptake of Gd-chol-HDL was faster and more efficient.…”

Section: Discussionmentioning

confidence: 53%

Recombinant high-density lipoprotein nanoparticles containing gadolinium-labeled cholesterol for morphologic and functional magnetic resonance imaging of the liver

Rui

Guo²,

Ding³

et al. 2012

IJN

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Background: Natural high-density lipoproteins (HDL) possess important physiological functions to the transport of cholesterol from the peripheral tissues to the liver for metabolic degradation and excretion in the bile. Methods and results:In this work, we took advantage of this pathway and prepared two different gadolinium (Gd)-DTPA-labeled cholesterol-containing recombinant HDL nanoparticles (Gd-chol-HDL) and Gd-(chol) 2 -HDL as liver-specific magnetic resonance imaging (MRI) contrast agents. The reconstituted HDL nanoparticles had structural similarity to native HDL, and could be taken up by HepG2 cells via interaction with HDL receptors in vitro. In vivo MRI studies in rats after intravenous injections of 10 µmol gadolinium per kg of recombinant HDL nanoparticles indicated that both nanoparticles could provide signal enhancement in the liver and related organs. However, different T 1 -weighted image details suggested that they participated in different cholesterol metabolism and excretion pathways in the liver. Conclusion: Such information could be highly useful to differentiate functional changes as well as anatomic differences in the liver. These cholesterol-derived contrast agents and their recombinant HDL preparations may warrant further development as a new class of contrast agents for MRI of the liver and related organs.

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Localization and regulation of SR-BI in membrane rafts of HepG2 cells

Cited by 89 publications

References 73 publications

Adenovirus-mediated overexpression of sphingomyelin synthases 1 and 2 increases the atherogenic potential in mice

Adenovirus-mediated overexpression of sphingomyelin synthases 1 and 2 increases the atherogenic potential in mice

Quantitative analysis of SR-BI-dependent HDL retroendocytosis in hepatocytes and fibroblasts

Recombinant high-density lipoprotein nanoparticles containing gadolinium-labeled cholesterol for morphologic and functional magnetic resonance imaging of the liver

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