Radiation inactivation of binding sites for high density lipoproteins in human fibroblast membranes

Radiation inactivation and target analysis were used to determine the molecular mass of the binding sites for high density lipoproteins (HDL) on membranes prepared from human fibroblasts. These membrane binding sites shared characteristics with the previously described HDL binding sites on whole fib...

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Bibliographic Details
Published in:The Journal of biological chemistry 1988-01, Vol.263 (3), p.1314-1319
Main Authors: Mendel, C M, Kunitake, S T, Kane, J P, Kempner, E S
Format: Article
Language:English
Subjects:
Analytical, structural and metabolic biochemistry
Binding Sites
Biological and medical sciences
Carrier Proteins
Cholesterol - metabolism
Cycloheximide - pharmacology
fibroblasts
Fibroblasts - metabolism
Fibroblasts - radiation effects
Fundamental and applied biological sciences. Psychology
Humans
ionizing radiation
Kinetics
lipoprotein (high density)
Lipoproteins, HDL - metabolism
man
Membranes - metabolism
Molecular Weight
Other biological molecules
Receptors, Cell Surface - metabolism
Receptors, Cell Surface - radiation effects
Receptors, Lipoprotein
RNA-Binding Proteins
Terpenes, steroids. Hormones
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Summary:Radiation inactivation and target analysis were used to determine the molecular mass of the binding sites for high density lipoproteins (HDL) on membranes prepared from human fibroblasts. These membrane binding sites shared characteristics with the previously described HDL binding sites on whole fibroblasts in tissue culture. They exhibited the same affinity for HDL, the same ligand specificity, and the same sensitivity to proteolytic agents. They were also up-regulated by cholesterol loading of the cells. Kinetics of HDL dissociation from membrane binding sites could not be described by a single exponential function, indicating that HDL probably bind to multiple classes of sites on fibroblast membranes. After exposure to ionizing radiation, these sites decreased in number as an apparent single exponential function of radiation dose, corresponding to an average molecular mass of 16,000 +/- 1,000 Da, which is smaller than any known cell-surface receptor protein. These data indicate that HDL binding sites on fibroblast membranes are not “classical” receptors in that they are kinetically heterogeneous and small in molecular mass.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(19)57302-1