Desialized Low‐Density Lipoprotein Regulates Cholesterol Metabolism in Receptor‐Deficient Fibroblasts

Filipović, Ivan; Buddecke, Eckhart

doi:10.1111/j.1432-1033.1979.tb04223.x

Cited by 16 publications

(8 citation statements)

References 20 publications

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“…Malmendier et al (50) had observed that the removal of sialic acid from human LDL in vivo increased the rate of metabolic clearance. Similarly, Filipovic and Buddeck (51) found that removal of sialic acid residues accelerate the rate of internalization of the lipoprotein and subsequently the regulation of the metabolism of cellular cholesterol. In contrast, however, Melajarvi et al (52) have shown that sialic acid poor LDL is catabolized more slowly than the sialic acid rich LDL.…”

Section: Serum Sialic Acidmentioning

confidence: 91%

Sialic acid in cardiovascular diseases

Nigam

Narain

Kumar

2006

Indian J Clin Biochem

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Sialic acid, the acylated derivatives of 9-carbon sugar neuraminic acid, present as terminal component of oligosaccharide chains of many glycoproteins and glycolipids, has been recognized to be involved in the regulation of a great variety of biological phenomena. Studies have shown that serum sialic acid predicts both coronary heart disease and stroke mortality and reflects the existence or activity of an atherosclerotic process. Most of the studies have shown an elevation in serum sialic acid concentration in coronary heart disease and a positive correlation between the raised serum sialic acid and the severity of the coronary lesions is observed. However, a few contradictory reports are also available. Racial differences in serum sialic acid have also been reported and correlated with international differences in the prevalence of atherosclerosis. Reduced sialic acid content of platelets, erythrocytes and lipoproteins may play important role in the pathogenesis of atherosclerosis. Elucidation of the mechanism of alternation in sialic acid concentration may throw more light on its potential clinical utility. Hence more studies are needed to designate sialic acid as a cardiovascular risk factor / marker.

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Section: Serum Sialic Acidmentioning

confidence: 91%

Sialic acid in cardiovascular diseases

Nigam

Narain

Kumar

2006

Indian J Clin Biochem

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“…The carbohydrate moieties may play a role for the function, the antigenicity, and the circulatory life time of a plasma glycoprotein. In the case of the carbohydrate moieties of LDL, several studies have also been done, but the results remain controversial (11,12,13,14,15,16).…”

Section: Discussionmentioning

confidence: 99%

“…As shown in Figure 3C and D, association and degradation in WHHL rabbit fibroblasts was much lower than those in normal rabbit fibroblasts and there was no significant difference between the types of 125 I-LDL. Figure 4A and B showed [ 14 (8,9). We speculate that the variable activity of one or more of these processing enzymes might cause the variation of carbohydrate moieties, resulting in the change of the molar ratio of acidic sugar chains of apo B-100.…”

Section: Association Degradation and Cholesteryl Ester Formation Ofmentioning

confidence: 99%

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Relation of N-glycosylation of apolipoprotein B-100 to cellular metabolism of low density lipoprotein

et al. 1994

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We studied the functional role of N-linked sugar chains of apolipoprotein (apo) B-100 of low density lipoprotein (LDL) in cholesterol metabolism. The N-linked sugar chains of apo B-100 of LDL obtained from four homozygous Watanabe heritable hyperlipidemic (WHHL) rabbits were liberated by hydrazinolysis, followed by NaB3H4 reduction and were fractionated by paper electrophoresis and column chromatography. They consisted of one neutral (N) and two acidic (A1, A2) fractions. The ratio of apo B-100 acidic fractions (A1+A2) varied among 4 WHHL rabbits. Serial measurements of serum cholesterol levels showed that they decreased with aging in each of 4 WHHL rabbits. We investigated the relation of the ratio of acidic sugar chains of apo B-100 to the serum cholesterol levels. Reciprocals of the serum cholesterol levels were significantly correlated with the ratio of acidic sugar chains of apo B-100 (r = 0.901, P < 0.001). To elucidate the role of N-linked sugar chains of apo B-100, we investigated cellular uptake of LDL in normal rabbit skin fibroblasts. The amounts of association, degradation and cholesteryl esterification of LDL with a lower ratio of acidic sugar chains at 37 degrees C were greater than those of LDL with a higher ratio of acidic sugar chains. These results suggest that N-glycosylation of apo B-100 may be related with serum cholesterol levels and N-linked sugar chains of apo B-100 may play an important role in cellular metabolism of LDL.

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“…Likewise, Kooistra et al [18] showed that positive charges play a dominant role in the uptake of ribonuclease (PI = 9.5) by sinusoidal rat liver cells. Also, arginine residues, as well as oligosaccharide moieties, contribute to the binding to endocytic receptors (on human fibroblasts) of the complex determinants present on low-density lipoproteins [19,20] and on a-L-iduronidase 1211. The second is compatible with the proposal of Chothia and Janin [22] that when insulin associates to form dimers the binding is dominated by hydrophobic interactions, and with the finding of Kahn et al [23] that the free-energy term in the binding of insulin to purified liver membranes is dominated by the entropy term.…”

Section: Discussionmentioning

confidence: 99%

Heterogeneity of Binding Sites for Adsorptive Pinocytosis of Simple Proteins by Rat Yolk Sacs

Livesey

Williams

1982

European Journal of Biochemistry

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1. When rat yolk sacs were incubated in serum-free medium 199, the '251-labelled forms of both formaldehyde-treated bovine serum albumin and ribonuclease were captured far more rapidly than 1251-labelled polyvinylpyrrolidone. Extensive adsorption of these proteins to the plasma membrane is the main cause of this effect.2. Quantitative analysis of the adsorptive-phase pinocytosis of these two proteins showed curved Hofstee plots, suggesting either the presence of multiple classes of binding site on the surface of pinocytically-active yolk-sac cells or a single class of binding site that exhibits negative cooperativity in the binding of these proteins. The values of K, were similar, ranging over 0.6-11.8 pM for '251-labelled ribonuclease and over 0.31 -4.7 pM for formaldehyde-treated '251-labelled albumin.3. Competitive uptake studies, in which tracer amounts of each of the '251-labelled proteins were ingested from serum-free medium containing a higher concentration of one of a series of unlabelled proteins, revealed marked differences between the two radiolabelled proteins. These findings suggest that formaldehyde-denatured albumin is captured by binding to hydrophobic binding sites on the plasma membrane whereas ribonuclease is captured by binding to negatively charged sites.Studies by Ashwell and co-workers [I] established unequivocally the importance of terminal galactosyl residues in determining the rate of clearance of modified serum glycoproteins from the circulation of the rat by hepatocytes. Other investigators have since extended these studies by ihowing that different oligosaccharide-based determinants are important in the endocytic capture of a variety of glycoproteins by other mammalian cells (see [2] for a review). Apart from formaldehyde-treated '251-labelled bovine serum albumin, whose clearance froin the circulation has been investigated [3,4] and whose uptake by isolated hepatocytes and nonparenchymal liver cells has been investigated in vitro [5], the endocytic capture of simple proteins has received relatively little attention. It has, however, been shown that in vitro the rat yolk sac rapidly ingests denatured preparations of bovine serum albumin by adsorptive pinocytosis [4,6], but a detailed quantitative analysis of the uptake of such protein preparations is hampered by the presence in the incubation medium of high concentrations of potentially competing proteins derived from the calf-serum component of the medium.The recent demonstration that yolk-sac tissue will actively pinocytose in serum-free medium 199 [7] has enabled the complications caused by the presence of calf serum [6] to be avoided, thus permitting a more detailed investigation of protein-binding to the plasma membrane [7]. Since the monomeric forms of several simple proteins have been shown to be captured by the rat yolk sac almost entirely by adsorptive pinocytosis [S], it was of interest to establish the affinities of some of these proteins for binding sites on the plasma mcmbrane. It was also of interest to investigate the ...

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Desialized Low‐Density Lipoprotein Regulates Cholesterol Metabolism in Receptor‐Deficient Fibroblasts

Cited by 16 publications

References 20 publications

Sialic acid in cardiovascular diseases

Sialic acid in cardiovascular diseases

Relation of N-glycosylation of apolipoprotein B-100 to cellular metabolism of low density lipoprotein

Heterogeneity of Binding Sites for Adsorptive Pinocytosis of Simple Proteins by Rat Yolk Sacs

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