A Novel Oxidized Low Density Lipoprotein-binding Protein in Macrophage

Scavenger receptor A(SR-A)on the mouse peritoneal macrophages(MPM) mediates the endocytic uptake of oxidized low density lipoproteins(ox-LDL). However, using ligand blotting and immunoblotting, a novel macrophage membrane protein binding to ox-LDL with estimated molecular mass of 92 kD was found. This membrane protein could not bind to ac-LDL. Its binding to ligands was not affected by reducing reagents either. Preincubation with medium containing neuraminidase dramatically decreased binding of the 92 kD membrane protein to ox-LDL. Excess amounts of ox-LDL could completely block the binding of (125)I ox-LDL to 92 kD membrane protein, but polyI, dextran sulfate and fucoidin showed partial competitive inhibition effects to the binding. These results suggest that the novel 92 kD membrane protein plays important role in the MPM uptake of ox-LDL.