Self-association of the low density lipoprotein receptor mediated by the cytoplasmic domain.

I. R. van Driel, C. G. Davis, J. L. Goldstein, M. S. Brown

Research output: Contribution to journalArticle

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Abstract

When the low density lipoprotein (LDL) receptor was solubilized from bovine adrenal cortex membranes and subjected to electrophoresis in the absence of reducing agents, a disulfide-bonded dimeric species was demonstrated. Formation of these covalent bonds was blocked when the tissue was homogenized in the presence of sulfhydryl alkylating agents, indicating that the native receptor was self-associated noncovalently and that the disulfide bond formation occurred only after homogenization. The disulfide-linked dimers were disrupted and the receptor was restored to a monomeric form when inside-out adrenal vesicles were treated with trypsin, suggesting that the disulfide bond formation involved the 50-amino acid cytoplasmic domain of the receptor. When the receptor was solubilized from bovine adrenal cortex membranes and then purified by ion exchange and affinity chromatography, it could be covalently coupled into dimers and trimers in the presence of bivalent cross-linking agents. Receptor dimers could also be demonstrated by chemical cross-linking of intact cells that were transfected with an expressible cDNA encoding the normal human LDL receptor. Dimer formation was markedly reduced in transfected cells expressing mutated cDNAs that had premature termination codons at positions 792, 807, and 812, which produced shortened receptors that retained 2, 17, and 22 of the original 50 amino acids of the cytoplasmic domain, respectively. The first two mutant receptors, which did not form oligomers, did not enter coated pits and were not rapidly internalized by cells. However, the mutant receptor that terminates at position 812 was internalized normally even though oligomer formation was greatly reduced. Moreover, a mutant receptor with a cysteine substituted for a tyrosine at position 807, which internalized very slowly, showed a normal susceptibility to chemical cross-linking. Deletion of external domains of the LDL receptor, including the epidermal growth factor homology region and the O-linked sugar domain, did not alter susceptibility to chemical cross-linking. We conclude that the cytoplasmic domain of the LDL receptor is responsible both for self-association into oligomers and for clustering in coated pits, but the available data do not establish a causal connection between these two events.

Original languageEnglish (US)
Pages (from-to)16127-16134
Number of pages8
JournalJournal of Biological Chemistry
Volume262
Issue number33
StatePublished - Nov 25 1987

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LDL Receptors
Disulfides
Dimers
Oligomers
Association reactions
Adrenal Cortex
Complementary DNA
Membranes
Affinity chromatography
Amino Acids
Covalent bonds
Nonsense Codon
Alkylating Agents
Reducing Agents
Ion Exchange Chromatography
Cytoplasmic and Nuclear Receptors
Electrophoresis
Affinity Chromatography
Epidermal Growth Factor
Sugars

ASJC Scopus subject areas

  • Biochemistry

Cite this

Self-association of the low density lipoprotein receptor mediated by the cytoplasmic domain. / van Driel, I. R.; Davis, C. G.; Goldstein, J. L.; Brown, M. S.

In: Journal of Biological Chemistry, Vol. 262, No. 33, 25.11.1987, p. 16127-16134.

Research output: Contribution to journalArticle

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