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.
Immunoprecipitation of the low-density-lipoprotein (LDL) receptor and its precursor from human monocyte-derived macrophages
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A K Soutar, B L Knight; Immunoprecipitation of the low-density-lipoprotein (LDL) receptor and its precursor from human monocyte-derived macrophages. Biochem J 1 February 1986; 233 (3): 683–690. doi: https://doi.org/10.1042/bj2330683
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