Abstract

An ultracentrifugation assay has been developed to measure low density lipoprotein (LDL) receptor activity in membranes prepared from cultured human fibroblasts. The binding site for 125I-labeled LDL in isolated membranes reflected the properties of the LDL receptor previously demonstrated in intact fibroblasts. It exhibited high affinity (Kd approximately 4 microgram of LDL protein/ml), specificity (LDL approximately 400-fold more effective than high density lipoprotein in competing with 125I-LDL for the binding site), dependence on calcium, and susceptibility to destruction by pronase. The number of LDL receptors detected in the in vitro membrane binding assay was similar to the number detected in intact cells. The number of receptors was reduced in membranes from fibroblasts that were grown in the presence of 25-hydroxycholesterol plus cholesterol and in fibroblast membranes from a subject with homozygous familial hypercholesterolemia, two situations in which the number of LDL receptors in intact fibroblasts is known to be reduced. The availability of a membrane binding assay that faithfully reflects the properties of the physiologic LDL receptor of intact cells should permit the characterization of this receptor in organs from intact humans and animals.

Keywords

Characterization (materials science)MembraneChemistryReceptorLow-density lipoproteinCell biologyLDL receptorLipoproteinBiochemistryBiophysicsBiologyMaterials scienceCholesterolNanotechnology

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Publication Info

Year
1978
Type
article
Volume
253
Issue
11
Pages
3852-3856
Citations
210
Access
Closed

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S. Basu, J L Goldstein, M S Brown (1978). Characterization of the low density lipoprotein receptor in membranes prepared from human fibroblasts.. Journal of Biological Chemistry , 253 (11) , 3852-3856. https://doi.org/10.1016/s0021-9258(17)34768-3

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DOI
10.1016/s0021-9258(17)34768-3