scholarly journals Selective uptake of cholesteryl esters of low-density lipoproteins is mediated by the lipoprotein-binding site in HepG2 cells and is followed by the hydrolysis of cholesteryl esters

1996 ◽  
Vol 318 (3) ◽  
pp. 841-847 ◽  
Author(s):  
Louise BRISSETTE ◽  
Marie-Claude CHAREST ◽  
Louise FALSTRAULT
Keyword(s):  
Binding Site ◽  
Hepg2 Cells ◽  
Ldl Receptor ◽  
Cholesteryl Oleate ◽  
Low Density Lipoproteins ◽  
Low Density ◽  
Cholesteryl Esters ◽  
Selective Uptake ◽  
Lipoprotein Binding ◽  
Hydrolysis Of

The study described in this paper shows that 125I-labelled low-density lipoproteins (LDL) interact with high- and low-affinity binding sites on human hepatoma (HepG2) cells. The former site is the LDL receptor and the latter is the lipoprotein-binding site (LBS). The association of 125I-labelled LDL and [3H]cholesteryl ethers–LDL with HepG2 cells revealed a 4-fold selective uptake of cholesteryl esters (CE) in a 4 h incubation period, which correlated with the depletion of CE mass in LDL. This selective uptake was not observed when the cells were incubated in the presence of a 100-fold excess of high-density lipoprotein 3, conditions where only the LDL receptor is being monitored. Also, no reduction in uptake was observed in the presence of IgG-C7, an anti-(LDL receptor) monoclonal antibody. Both findings indicate that the selective uptake occurs through the LBS and that the LBS contributes more to the entry of CE from LDL into the cell than does the LDL receptor. The fates of CE entering the cell via the LDL receptor and the LBS were also followed. To achieve this, LDL were labelled with [3H]cholesteryl oleate and the hydrolysis of [3H]cholesteryl oleate was monitored. The results indicated that 45% of the CE were hydrolysed after a 4 h incubation period, irrespective of the site of entry. Chloroquine (100 µM) was shown to inhibit hydrolysis, indicating that lysosomal enzymes were responsible for the hydrolysis of LDL–CE, whichever pathway was used. Thus our results reveal, for the first time, that the mass of CE entering the cell via the LBS is substantial and that hydrolysis of CE is by lysosomal enzyme activity. Overall, this suggests that the LBS has significant physiological importance.

Selective uptake of cholesteryl esters from various classes of lipoproteins by HepG2 cells

1999 ◽  
Vol 77 (2) ◽  
pp. 157-163 ◽  
Author(s):  
Louise Brissette ◽  
Marie-Claude Charest ◽  
Louise Falstrault ◽  
Julie Lafond ◽  
David Rhainds ◽  
...  
Keyword(s):  
Total Lipid ◽  
Hepg2 Cells ◽  
Ldl Receptor ◽  
Inverse Correlation ◽  
Low Density Lipoproteins ◽  
High Density Lipoproteins ◽  
Low Density ◽  
Cholesteryl Esters ◽  
Very Low Density Lipoproteins ◽  
Selective Uptake

Selective uptake of cholesteryl esters (CE) from lipoproteins by cells has been extensively studied with high density lipoproteins (HDL). It is only recently that such a mechanism has been attributed to intermediate and low density lipoproteins (IDL and LDL). Here, we compare the association of proteins and CE from very low density lipoproteins (VLDL), IDL, LDL and HDL3 to HepG2 cells. These lipoproteins were either labelled in proteins with 125I or in CE with 3H-cholesteryl oleate. We show that, at any lipoprotein concentration, protein association to the cells is significantly smaller for IDL, LDL, and HDL3 than CE association, but not for VLDL. At a concentration of 20 µg lipoprotein/mL, these associations reveal CE-selective uptake in the order of 2-, 4-, and 11-fold for IDL, LDL, and HDL3, respectively. These studies reveal that LDL and HDL3 are good selective donors of CE to HepG2 cells, while IDL is a poor donor and VLDL is not a donor. A significant inverse correlation (r2 = 0.973) was found between the total lipid/protein ratios of the four classes of lipoproteins and the extent of CE-selective uptake by HepG2 cells. The fate of 3H-CE of the two best CE donors (LDL and HDL3) was followed in HepG2 cells after 3 h of incubation. Cells were shown to hydrolyze approximately 25% of the 3H-CE of both lipoproteins. However, when the cells were treated with 100 µM of chloroquine, a lysosomotropic agent, 85 and 40% of 3H-CE hydrolysis was lost for LDL and HDL3, respectively. The fate of LDL and HDL3-CE in HepG2 cells deficient in LDL-receptor was found to be the same, indicating that the portion of CE hydrolysis sensitive to chloroquine is not significantly linked to LDL-receptor activity. Thus, in HepG2 cells, the magnitude of CE-selective uptake is inversely correlated with the total lipid/protein ratios of the lipoproteins and CE-selective uptake from the two best CE donors (LDL and HDL3) appears to follow different pathways.Key words: lipoprotein, receptor, HepG2 cell, selective uptake, lipid, cholesterol, binding.

scholarly journals Effect of Exposure of Human Monocyte-Derived Macrophages to High, versus Normal, Glucose on Subsequent Lipid Accumulation from Glycated and Acetylated Low-Density Lipoproteins

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Fatemeh Moheimani ◽  
Joanne T. M. Tan ◽  
Bronwyn E. Brown ◽  
Alison K. Heather ◽  
David M. van Reyk ◽  
...  
Keyword(s):  
High Glucose ◽  
Lipid Accumulation ◽  
Scavenger Receptor ◽  
Ldl Receptor ◽  
Human Monocyte ◽  
Low Density Lipoproteins ◽  
Receptor Expression ◽  
Low Density ◽  
Cholesteryl Esters ◽  
Protein Levels

During atherosclerosis monocyte-derived macrophages accumulate cholesteryl esters from low-density lipoproteins (LDLs) via lectin-like oxidised LDL receptor-1 (LOX-1) and class AI and AII (SR-AI, SR-AII) and class B (SR-BI, CD36) scavenger receptors. Here we examined the hypothesis that hyperglycaemia may modulate receptor expression and hence lipid accumulation in macrophages. Human monocytes were matured into macrophages in 30 versus 5 mM glucose and receptor expression and lipid accumulation quantified. High glucose elevated LOX1 mRNA, but decreased SR-AI, SR-BI, LDLR, and CD36 mRNA. SR-BI and CD36 protein levels were decreased. Normo- and hyperglycaemic cells accumulated cholesteryl esters from modified LDL to a greater extent than control LDL, but total and individual cholesteryl ester accumulation was not affected by glucose levels. It is concluded that, whilst macrophage scavenger receptor mRNA and protein levels can be modulated by high glucose, these are not key factors in lipid accumulation by human macrophages under the conditions examined.

Transporting mitochondrion-targeting photosensitizers into cancer cells by low-density lipoproteins for fluorescence-feedback photodynamic therapy

Nanoscale ◽  
2021 ◽  
Author(s):  
Chao Wang ◽  
Xianhao Zhao ◽  
Haoyu Jiang ◽  
Jiaxin Wang ◽  
Weixiu Zhong ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
Cancer Cells ◽  
Ldl Receptor ◽  
Low Density Lipoproteins ◽  
Low Density

Low-density lipoproteins (LDLs) reconstituted with a multifunctional mitochondrion-targeting photosensitizer are able to achieve fluorescence-feedback photodynamic therapy of LDL receptor-overexpressing cancer cells.

scholarly journals Ligand selectivity of 105 kDa and 130 kDa lipoprotein-binding proteins in vascular-smooth-muscle-cell membranes is unique

1996 ◽  
Vol 317 (1) ◽  
pp. 297-304 ◽  
Author(s):  
Valery N. BOCHKOV ◽  
Vsevolod A. TKACHUK ◽  
Maria P. PHILIPPOVA ◽  
Dimitri V. STAMBOLSKY ◽  
Fritz R. BÜHLER ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Binding Proteins ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Low Density ◽  
Dextran Sulphate ◽  
Apo B ◽  
Ligand Selectivity ◽  
Lipoprotein Binding

Using ligand blotting techniques, with low-density lipoprotein (LDL) as ligand, we have previously described the existence of atypical lipoprotein-binding proteins (105 kDa and 130 kDa) in membranes from human aortic medial tissue. The present study demonstrates that these proteins are also present in membranes from cultured human (aortic and mesenteric) and rat (aortic) vascular smooth-muscle cells (VSMCs). To assess the relationship of 105 and 130 kDa lipoprotein-binding proteins to known lipoprotein receptors, ligand binding specificity was studied. We tested effects of substances known to antagonize ligand binding to either the LDL [apolipoprotein B,E (apo B,E)] receptor (dextran sulphate, heparin, pentosan polysulphate, protamine, spermine, histone), the scavenger receptor (dextran sulphate, fucoidin), the very-low-density-lipoprotein (VLDL) receptor [receptor-associated protein (RAP)], or LDL receptor-related protein (RAP, α2-macroglobulin, lipoprotein lipase, exotoxin-A). None of these substances, with the exception of dextran sulphate, influenced binding of LDL to either 105 or 130 kDa proteins. Sodium oleate or oleic acid, known stimuli for the lipoprotein binding activity of the lipolysis-stimulated receptor, were also without effect. LDL binding to 105 and 130 kDa proteins was inhibited by anti-LDL (apo B) antibodies. LDL and VLDL bound to 105 and 130 kDa proteins with similar affinities (蝶50 μg/ml). The unique ligand selectivity of 105 and 130 kDa proteins supports the existence of a novel lipoprotein-binding protein that is distinct from all other currently identified LDL receptor family members. The similar ligand selectivity of 105 and 130 kDa proteins suggests that they may represent variant forms of an atypical lipoprotein-binding protein.

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