Immunoblot analysis of low density lipoprotein receptors in fibroblasts from subjects with familial hypercholesterolemia

U. Beisiegel, W. J. Schneider, M. S. Brown, J. L. Goldstein

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Abstract

This paper describes a sensitive method for study of the isoelectric point and molecular weight of immunoreactive low density lipoprotein (LDL) receptors of cultured human fibroblasts. The fibroblast receptors are solubilized with Triton X-100, partially purified by batch elution from DEAE-cellulose, and subjected to two-dimensional isoelectric focusing/sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The proteins are transferred electrophoretically to nitrocellulose paper which is then incubated with a mouse monocloned antibody (IgG-C7) directed against the LDL receptor, followed by an 125I-labeled antibody against mouse IgG. The receptor-bound monoclonal antibody is localized by autoradiography. By this technique, the immunodetectable LDL receptors from normal human fibroblasts migrate as a single spot with an isoelectric point of 4.3 and a M(r) of ~ 160,000. In one patient with homozygous familial hypercholesterolemia whose cells fail to bind 125I-labeled IgG-C7, no immunoreactive LDL receptor spot was detected after electrophoresis. We also studied LDL receptors from three homozygotes whose cells bind 125I-IgG-C7, i.e. cross-reacting material-positive mutants. Their immunodetectable receptors were indistinguishable from normal receptors in terms of isoelectric point and molecular weight. Similarly, the receptors from one patient with the internalization-defective form of familial hypercholesterolemia showed normal electrophoretic migration. The immunoblotting technique should prove useful in analyzing structural alterations, if they exist, in LDL receptors from other subjects with cross-reacting material-positive forms of familial hypercholesterolemia.

Original languageEnglish (US)
Pages (from-to)13150-13156
Number of pages7
JournalJournal of Biological Chemistry
Volume257
Issue number21
StatePublished - 1982

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Hyperlipoproteinemia Type II
LDL Receptors
Fibroblasts
Isoelectric Point
Immunoglobulin G
Electrophoresis
Molecular Weight
IgG Receptors
DEAE-Cellulose
Molecular weight
Collodion
Antibodies
Octoxynol
Homozygote
Isoelectric Focusing
Autoradiography
Immunoblotting
Sodium Dodecyl Sulfate
Polyacrylamide Gel Electrophoresis
Monoclonal Antibodies

ASJC Scopus subject areas

  • Biochemistry

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Immunoblot analysis of low density lipoprotein receptors in fibroblasts from subjects with familial hypercholesterolemia. / Beisiegel, U.; Schneider, W. J.; Brown, M. S.; Goldstein, J. L.

In: Journal of Biological Chemistry, Vol. 257, No. 21, 1982, p. 13150-13156.

Research output: Contribution to journalArticle

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