A high carbohydrate-fat free diet alters the proportion of heparin-bound VLDL in plasma and the expression of VLDL-apoB-100 epitopes

Keidar, Shlomo; Goldberg, Anne C.; Cook, K; Bateman, Joyce; Schonfeld, Gustav

doi:10.1016/0026-0495(90)90048-h

Cited by 19 publications

(6 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The cell layer was washed three times with PBS and extracted by a 1-h incubation at room temperature with 0.5 ml of 0.1 N NaOH for measurement of protein by the method of Lowry et al (23) and for determination of cell-associated I-labeled lipoproteins. The mAb B1B6, which binds to the LDL receptor-binding domains on LDL apo B-100, was used to assess binding of the lipoprotein to the LDL receptor (33).…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Phospholipase D-modified low density lipoprotein is taken up by macrophages at increased rate. A possible role for phosphatidic acid.

Aviram

Maor²

1993

J. Clin. Invest.

View full text Add to dashboard Cite

show abstract

Section: Methodsmentioning

confidence: 99%

“…Subfractionation of LDL and PLase D-LDL by heparin Sepharose was carried out as previously described (33). Sepharose complexed with heparin (Affi-gel Heparin; Bio-Rad Laboratories) was packed into a small column (10 X 2 cm).…”

Section: Methodsmentioning

confidence: 99%

Phospholipase D-modified low density lipoprotein is taken up by macrophages at increased rate. A possible role for phosphatidic acid.

Aviram

Maor²

1993

J. Clin. Invest.

View full text Add to dashboard Cite

show abstract

“…On the basis of our structure, LDL-R in the extended form could span about 270 Å (140 Å for R2 to R7, an estimated 25 Å if R1 plus linker is included, and 105 Å added for the EGF precursor homology domain). Inasmuch as the lipoprotein particle size and content is modulated by diet, disease, and pharmacopoeia, in turn affecting its plasma clearance (1,9,35,(39)(40)(41), and many others), recognition of lipoproteins by LDL-R is of great clinical relevance. The extracellular domain of LDL-R appears ideally suited to recognize, bind, and release varying particles through the combination of a flexible modular ligand-binding domain and a more-or-less rigid acid-release domain.…”

mentioning

confidence: 99%

Structure of the LDL Receptor Extracellular Domain at Endosomal pH

Rudenko¹,

Henry

Henderson

et al. 2002

Science

424

500

View full text Add to dashboard Cite

The low-density lipoprotein receptor mediates cholesterol homeostasis through endocytosis of lipoproteins. It discharges its ligand in the endosome at pH Ͻ 6. In the crystal structure at pH ϭ 5.3, the ligand-binding domain (modules R2 to R7) folds back as an arc over the epidermal growth factor precursor homology domain (the modules A, B, ␤ propeller, and C). The modules R4 and R5, which are critical for lipoprotein binding, associate with the ␤ propeller via their calcium-binding loop. We propose a mechanism for lipoprotein release in the endosome whereby the ␤ propeller functions as an alternate substrate for the ligand-binding domain, binding in a calcium-dependent way and promoting lipoprotein release.The low-density lipoprotein receptor (LDL-R) regulates cholesterol homeostasis in mammalian cells. LDL-R removes cholesterolcarrying lipoproteins from plasma circulation in a process known as receptor-mediated endocytosis (1). Ligands bound extracellularly by LDL-R at neutral pH are internalized and then released in the endosomes ( pH Ͻ 6), leading to their subsequent lysosomal degradation. The receptor then recycles to the cell surface. Mutations in the LDL-R gene cause familial hypercholesterolemia (FH), one of the most common simply inherited genetic diseases (2). FH heterozygotes exhibit a reduced rate of receptor-mediated removal of plasma LDL by the liver, ultimately leading to early onset coronary heart disease and atherosclerosis. More than 920 mutations in LDL-R are known, some of which have been functionally characterized (2, 3).The extracellular domain of LDL-R is composed of a "ligand-binding domain" (with cysteine-rich repeats R1 to R7) and an "epidermal growth factor (EGF) precursor homology domain" (with the EGF-like repeats A, B, and C, as well as a ␤ propeller between B and C) (4, 5). LDL-R binds LDL via the single protein in LDL, the 550-kD apolipoprotein B (apoB) (6); deleting R3, R4, R5, R6, or R7 reduces LDL binding to Ͻ20% of that of the wild-type LDL-R (7). LDL-R also binds to very low density lipoprotein (VLDL), ␤-VLDL, intermediate density lipoprotein (IDL), and chylomicron remnants via the 33-kD apolipoprotein E (apoE) (8, 9); disrupting R5 decreases ␤-VLDL binding to 30 to 50% of that of the wild-type receptor, whereas disrupting R4 or R6 reduces binding only slightly (7). At neutral pH, negative charges on repeats R1 to R7 are thought to interact with positive charges on apoB and apoE. Indeed, LDL binding to LDL-R can be disrupted competitively with polycations or permanently by selective chemical modification of positively charged residues on apoE or apoB (1,10,11). Further, the LDL-R cysteine-rich repeats contain clusters of acidic residues implicated not only in ligand binding but also in calcium binding, as shown at pH ϭ 5.0 crystallographically by Fass et al. (12) and at pH ϭ 6.7 with the use of nuclear magnetic resonance (NMR) imaging (13). The calcium ions enable the repeats to bind to the ligand (14,15).Dissociation of ligands is crucial for receptor recycling and hence prop...

show abstract

“…Solid phase competitive binding radioimmunoassay LDL, drug-associated LDLs and LDL incubated with the appropriate solvents (control LDLs) were assayed in competitive displacement assays on microtitre plates (15). The plates were coated with 140 μΐ of 10 mg/1 purified monoclonal antibody B1B6 (this antibody is directed towards the LDL receptor binding domains on apolipoprotein B-100 and mapped to amino acid residues 3114-3606; it was a generous gift from Drs.…”

Section: Lipoproteinsmentioning

confidence: 99%

Dual Effect of Lovastatin and Simvastatin on LDL-Macrophage Interaction

Aviram

Keidar²,

Brook³

1991

Clinical Chemistry and Laboratory Medicine

View full text Add to dashboard Cite

Lovastatin and simvastatin which are very potent cellular cholesterol biosynthesis Inhibitors, significantly affect the plasma lipoprotein concentration.After incubation of plasma with 14 C-labelled compounds, radioactivity was found in all lipoprotein fractions but mainly (40%) in high density lipoprotein (HOL), and in the lipoprotein-deficient plasma fraction (20-30%). Dr g-treated lipoproteins showed reduced electrophoretic mobility on cellulose acetate in comparison with control lipoproteins. The lovastatin-treated low density lipoprotein (LDL) displayed 28% increased fluidity in comparison with control LDL. The immunoreactivity of drug-treated LDL with monoclonal antibody directed towards the LDL receptor binding domains (B1B6) was significantly less than that of control LDL, suggesting reduced binding to the LDL receptor. When drug-treated LDL was incubated with J-774 A. l macrophage-like cell line, its binding (at 4 °C) was 28% less than that of control LDL, whereas a substantial increase in the cellular cholesterol esterification rate (by 83% with lovastatin and by 67% with simvastatin) was noted. Similarly, the degradation of lovastatin and simvastatin-treated LDL by macrophages was 87 -89% greater than that of control LDL. The "apparent V max " for the macrophage degradation of lovastatin-treated LDL was 70% greater than that for control LDL. Thus, both drugs may have a dual effect on the macrophage uptake of LDL; they may increase the number of LDL receptors on the cell surface, but they may also reduce the affinity of LDL for its receptor, the former being the major effect. If the in vitro changes caused by drug-treated LDL also occur in vivo, then the cellular uptake of LDL and plasma cholesterol concentration could be determined by the magnitude of each of the opposing effects of the drugs.

show abstract

A high carbohydrate-fat free diet alters the proportion of heparin-bound VLDL in plasma and the expression of VLDL-apoB-100 epitopes

Cited by 19 publications

References 34 publications

Phospholipase D-modified low density lipoprotein is taken up by macrophages at increased rate. A possible role for phosphatidic acid.

Phospholipase D-modified low density lipoprotein is taken up by macrophages at increased rate. A possible role for phosphatidic acid.

Structure of the LDL Receptor Extracellular Domain at Endosomal pH

Dual Effect of Lovastatin and Simvastatin on LDL-Macrophage Interaction

Contact Info

Product

Resources

About