Immunoprecipitation of the low-density-lipoprotein (LDL) receptor and its precursor from human monocyte-derived macrophages.
Synthesis of the low-density-lipoprotein (LDL) receptor protein by cultured human monocyte-derived macrophages was demonstrated by immunoprecipitation of [35S]methionine-labelled cell extracts with a monoclonal antibody to the bovine adrenal LDL receptor. Although the antibody does not bind to or inhibit binding of 125I-LDL to the LDL receptor on intact fibroblasts, it specifically binds to a protein in extracts of human skin fibroblasts, of Mr approx. 130,000 under non-reducing conditions, that is able to bind LDL. In monocyte-derived macrophages, as in fibroblasts, the receptor is synthesized as a low-Mr precursor that is converted into the mature protein. The half-life of the precursor in human macrophages is approx. 44 min. In cells from two homozygous familial-hypercholesterolaemic subjects, only the precursor form of the receptor is synthesized. Detection of abnormalities of LDL-receptor synthesis in human mononuclear cells may be a useful aid in diagnosis of familial hypercholesterolaemia that is simpler and quicker than methods requiring growth of cultured skin fibroblasts.
A K
AK
Soutar
B L
BL
Knight
D000911:Antibodies, Monoclonal; D002478:Cells, Cultured; D011232:Chemical Precipitation; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D008264:Macrophages / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D011973:Receptors, LDL / Q000096:biosynthesis* / Q000276:immunology; D012867:Skin / Q000166:cytology
D000911:Antibodies, Monoclonal; D011973:Receptors, LDL; D008715:Methionine