Low-density lipoprotein receptor (LDL-R) was found to be expressed in human small intestine epithelial cells, enterocytes. The relative abundance of LDL-R mRNA and protein was compared with that of apolipoproteins A-I (apoA-I) and B (apoB) in enterocytes and two other cell types: CaCo-2 and HepG2. The LDL-R mRNA content was comparable in three cell types. Human enterocytes expressed 5.2- to 14-fold more apoA-I mRNA than the other cells. In contrast, HepG2 cells expressed 10-to 19-fold more apoB mRNA than CaCo-2 cells and human enterocytes. Immunoprecipitation of [(35)S]methionine pulse-labeled intracellular proteins from these cell types demonstrated that human enterocytes synthesize more apoA-I and apoB, while HepG2 cells synthesize a slightly higher amount of LDL-R.
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