Chinese hamster ovary cells expressing a novel type of acetylated low density lipoprotein receptor. Isolation and characterization.

Macrophage scavenger receptors mediate the recognition of a wide range of negatively charged macromolecules including acetylated low density lipoproteins (AcLDL). Chinese hamster ovary (CHO) cells were cultured in the presence of increasing concentrations of simvastatin, a cholesterol biosynthesis inhibitor, and AcLDL as the sole source of exogenous lipoproteins. The cells surviving under these conditions specifically bound 125I-labeled AcLDL with high affinity and degraded them via an endocytic pathway. Unexpectedly, the association and degradation of 125I-labeled AcLDL by these CHO cells were not inhibited by dextran sulfate, fucoidan, and polyinosinic acid, competitors of macrophage scavenger receptors, but were completely inhibited by maleylated bovine serum albumin. Furthermore, these cells effectively took up negatively charged liposomes containing acidic phospholipids such as phosphatidylserine and phosphatidic acid, whereas CHO cells expressing macrophage scavenger receptors did not. AcLDL and negatively charged liposomes were cross-competed with each other. Northern blot analysis using the cDNA for the macrophage scavenger receptor revealed that these CHO cells did not express this receptor. From these observations, we conclude that the isolated CHO cells express a novel type of AcLDL receptor, which is distinct from macrophage scavenger receptors with respect to ligand specificity and competitor sensitivity.