Altered function and structure of low-density lipoprotein receptor in compactin (ML236B)-resistant mutants of Chinese hamster cells

Yoshida Takashi, Yoshimura Akihiko, Ono Mayumi, Hori Shigeaki, Waki Michinori, Kuwano Michihiko

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Abstract

Mutants resistant to compactin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, have been previously isolated from the Chinese hamster V79 cell line. Two compactin-resistant mutants, MF-1 and MF-2, show altered responses to human low-density lipoprotein (LDL). Accumulation of fluorescentlabeled LDL was much reduced. Ligand blotting showed LDL receptor activity in MF-1 and MF-2 cells of about one half to one third that of V79. Internalization and degradation of LDL in MF-1 or MF-2 cells were about one tenth those in V79 cells, suggesting that the LDL binding as well as the LDL internalization of the compactin-resistant clones was altered. Down-regulation of LDL receptor activity as well as hydroxymethylglutaryl CoA reductase was observed in V79 cells treated with LDL, while there appeared to be much less down-regulation in MF-1 and MF-2 cells. Using anti-LDL receptor antibody, MF-1 and MF-2 cells were found to produce smaller-sized mature forms of LDL receptor: the molecular mass of the mutant LDL receptor was 3-5 kDa smaller than that of the parental LDL receptor. Altered O-linked oligosaccharides or amino acid sequence might account for the decreased molecular mass and aberrant properties of the LDL receptor in MF-1 and MF-2.

Original languageEnglish
Pages (from-to)575-586
Number of pages12
JournalBiochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism
Volume921
Issue number3
DOIs
Publication statusPublished - 1987 Oct 17

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Keywords

  • Compactin-resistant mutant
  • Endocytosis
  • Hydroxymethylglutaryl-CoA reductase (Chinese hamster cells)
  • LDL receptor

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Endocrinology

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