Open AccessA point mutation of low‐density‐lipoprotein receptor causing rapid degradation of the receptor
Author(s) -
MIYAKE Yasuko,
TAJIMA Shoji,
FUNAHASHI Tohru,
YAMAMURA Taku,
YAMAMOTO Akira
Publication year - 1992
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1992.tb17383.x
Subject(s) - point mutation , ldl receptor , mutant , microbiology and biotechnology , exon , lrp1b , mutation , familial hypercholesterolemia , receptor , biology , gene , apolipoprotein b , lipoprotein , biochemistry , cholesterol
The exons of the low‐density‐lipoprotein‐(LDL)‐receptor gene from a Japanese patient with homozygous familial hypercholesterolemia were amplified by the polymerase chain reaction (PCR), and their nucleotide sequences were determined. A point mutation from G to C was found in exon 9, which was expected to change Asp at position 412 to His. This amino acid change occurred within the epidermal‐growth‐factor‐precursor homology domain of the LDL receptor, slightly impairing the processing from the precursor to the mature form and causing rapid degradation of the mature form in the fibroblasts of the patient. The mutant LDL‐receptor gene transfected into COS‐1 cells expressed a LDL‐receptor protein with the same properties as the protein expressed in the fibroblasts of the patient; impaired processing and rapid degradation of the synthesized receptor protein. The mutation was identified in family members of the patient by dot‐blot hybridization of PCR‐amplified DNA with the mutant oligonucleotide. The family members carrying the mutant gene showed higher serum cholesterol levels than the others. However, their cholesterol levels were also greatly influenced by the apolipoprotein‐E phenotype.