Altered function and structure of low-density lipoprotein receptor in compactin (ML236B)-resistant mutants of Chinese hamster cells.
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 fluorescent-labeled 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.
Yoshida
T
T
Department of Biochemistry, Oita Medical School, Japan.
Yoshimura
A
A
Ono
M
M
Hori
S
S
Waki
M
M
Kuwano
M
M
D000818:Animals; D002478:Cells, Cultured; D006224:Cricetinae; D004351:Drug Resistance / Q000235:genetics*; D004705:Endocytosis / Q000187:drug effects; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007120:Immunochemistry; D008077:Lipoproteins, LDL / Q000494:pharmacology; D008148:Lovastatin / Q000031:analogs & derivatives* / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D009154:Mutation; D011973:Receptors, LDL / Q000096:biosynthesis / Q000502:physiology*; D013261:Sterols / Q000096:biosynthesis
D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008077:Lipoproteins, LDL; D011973:Receptors, LDL; D013261:Sterols; C012258:mevastatin; D008148:Lovastatin