Binding and internalization of 125I-LDL in normal and mutant human fibroblasts. A quantitative autoradiographic study

Jean Louis Carpentier, Phillip Gorden, Joseph L. Goldstein, Richard G W Anderson, Michael S. Brown, Lelio Orci

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Abstract

Using a quantitative EM autoradiographic technique, we have visualized the membrane binding and receptor-mediated uptake of low density lipoprotein (LDL) in human fibroblasts. The initial binding was restricted to the plasma membrane (2 h of incubation at 4 °C) and approx. 62% of the grains could be localized to coated pits in the plasma membrane. When the incubations were carried out at 37 °C, 125I radioactivity was found both on the membrane and within the cell and predominantly localized on or within lysosomes. In cells from the patient J. D., a familial hypercholesterolemic homozygote with an internalization defect, initial binding of 125I-LDL was restricted to the plasma membrane but not preferentially localized to coated segments of the plasma membrane. After incubation for 30 min at 37 °C, the membrane bound 125I-LDL in J. D. cells was not internalized. These data confirm results obtained with ferritin-labeled LDL and illustrate the complementary application of two different morphologic probes, each of which offers special advantages for special problems.

Original languageEnglish (US)
Pages (from-to)135-142
Number of pages8
JournalExperimental Cell Research
Volume121
Issue number1
DOIs
StatePublished - Jun 1979

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ASJC Scopus subject areas

  • Cell Biology

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