scholarly journals Cholesterol esterification plays a major role in determining low-density-lipoprotein receptor activity in primary monolayer cultures of rat hepatocytes

1989 ◽  
Vol 263 (1) ◽  
pp. 255-260 ◽  
Author(s):  
A M Salter ◽  
N Ekins ◽  
M al-Seeni ◽  
D N Brindley ◽  
B Middleton
Keyword(s):  
Specific Binding ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Rat Hepatocytes ◽  
Receptor Activity ◽  
Cholesterol Esterification ◽  
Low Density ◽  
Density Lipoprotein Receptor ◽  
Ldl Binding

1. We have previously shown that the capacity for specific binding of human 125I-labelled low-density lipoprotein (LDL) to rat hepatocytes increases with time in culture [Salter, Bugaut, Saxton, Fisher & Brindley (1987) Biochem. J. 247, 79-84]. 2. In the present study we show that this up-regulation is accompanied by a rise in the cholesterol ester content of the cells. 3. Inhibition of cholesterol esterification with the drug 58-035 (Sandoz) significantly decreases the time-dependent ‘up-regulation’ of LDL receptors. 4. Incubation of hepatocytes with LDL itself has little effect on subsequent LDL binding. However, when cholesterol esterification is inhibited, incubation with LDL decreases binding below that attained with the drug alone. 5. Inhibition of cholesterol synthesis with Lovastatin significantly increases LDL binding and antagonizes the effect of 58-035. 6. We conclude that in hepatocytes the rate of cellular cholesterol esterification can become the major determinant of LDL-receptor activity.

Early Platelet Activation by Low Density Lipoprotein via p38MAP Kinase

1999 ◽  
Vol 82 (12) ◽  
pp. 1749-1756 ◽  
Author(s):  
Christian Hackeng ◽  
Ingrid Relou ◽  
Marc Pladet ◽  
Gertie Gorter ◽  
Herman van Rijn ◽  
...  
Keyword(s):  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Platelet Glycoprotein ◽  
Slight Reduction ◽  
Low Density ◽  
Density Lipoprotein Receptor ◽  
Arachidonate Metabolites ◽  
Ldl Binding ◽  
Dose Dependent

SummaryLow Density Lipoprotein (LDL) is known to sensitize platelets for physiological agonists. To clarify the basis of this sensitization, we investigated the involvement of p38MAP Kinase (p38MAPK). As dual phosphorylation on Thr180 and Tyr182 of p38MAPK is the trigger for activation of the kinase, p38MAPK-activity was measured with an antibody that recognizes the dual-phosphorylated sequence. LDL induced a rapid and dose dependent activation of p38MAPK. The activation was not inhibited by a wide variety of inhibitors of platelet signalling, including TxA2-formation, Phospholipase C-activation, Ca2+-mobilization and ERK 1/2-activation. Only a slight reduction in p38MAPK-activation was observed when protein kinase C was inhibited. Activation of p38MAPK was strongly inhibited by a rise in cAMP. Thus, p38MAPK-activation was upstream of most signalling pathways and close to the LDL-receptor. A number of platelet receptors was screened with the use of antibodies. Integrins αIIbβ3 and α2β1, as well as the FcγRII-receptor, CD36 (platelet glycoprotein IV), CD68 (gp110) and Low Density Lipoprotein-receptor related protein (LRP) were not implicated in LDL-induced p38MAPK-activation. Inhibition of LDL binding by modification of apo B100 lysines reduced p38MAPK-activation by 80 %. Activation of p38MAPK resulted in an increase in release of arachidonic acid, the precursor for thromboxane A2 synthesis. In conclusion, activation of p38MAPK might be the first step in platelet sensitization by LDL, leading to formation of arachidonate metabolites and increased aggregation and secretion responses to physiological agonists.

scholarly journals Detection of the low-density-lipoprotein receptor with biotin-low-density lipoprotein. A rapid new method for ligand blotting

1985 ◽  
Vol 229 (3) ◽  
pp. 785-790 ◽  
Author(s):  
D P Wade ◽  
B L Knight ◽  
A K Soutar
Keyword(s):  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
High Sensitivity ◽  
Receptor Protein ◽  
Low Density ◽  
Very Low Density Lipoproteins ◽  
Cell Extracts ◽  
Density Lipoprotein Receptor ◽  
A New Technique

A new technique has been developed to identify low-density-lipoprotein (LDL) receptors on nitrocellulose membranes, after transfer from SDS/polyacrylamide gels, by ligand blotting with biotin-modified LDL. Modification with biotin hydrazide of periodate-oxidized lipoprotein sugar residues does not affect the ability of the lipoprotein to bind to the LDL receptor. Bound lipoprotein is detected with high sensitivity by a streptavidin-biotin-peroxidase complex, and thus this method eliminates the need for specific antibodies directed against the ligand. The density of the bands obtained is proportional to the amount of pure LDL receptor protein applied to the SDS/polyacrylamide gel, so that it is possible to quantify LDL receptor protein in cell extracts. Biotin can be attached to other lipoproteins, for example very-low-density lipoproteins with beta-mobility, and thus the method will be useful in the identification and isolation of other lipoprotein receptors.

Low density lipoprotein-receptor activity is lost in vivo in malignantly transformed renal tissue

FEBS Letters ◽  
1986 ◽  
Vol 196 (1) ◽  
pp. 87-90 ◽  
Author(s):  
Ralph V. Clayman ◽  
Lyman E. Bilhartz ◽  
David K. Spady ◽  
L.Maximilian Buja ◽  
John M. Dietschy
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Renal Tissue ◽  
Receptor Activity ◽  
Low Density ◽  
Lipoprotein Receptor ◽  
Low Density Lipoprotein Receptor ◽  
Density Lipoprotein Receptor
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