CHARACTERIZATION OF A RECEPTOR FOR OXIDIZED LOW-DENSITY LIPOPROTEINS ON RAT KUPFFER CELLS - SIMILARITY TO MACROSIALIN

Rat liver Kupffer cell membranes contain a protein that recognizes spe cifically oxidized low-density lipoproteins (oxLDL). Visualization aft er blotting under reducing conditions indicates that the receptor is a monomeric protein, with an estimated molecular mass of 115-120 kDa. N -Glycosidase F and endoglycosidase F treatment,resulted in a fall in e stimated molecular mass of 24 and 11 kDa respectively, whereas O-glyco sidase was ineffective. No effect on the extent of interaction with ox LDL was noticed, suggesting that glycans are not essential for ligand recognition. Using a polyclonal antibody to mouse macrosialin, we visu alized macrosialin on blot, and compared this glycoprotein with the ox LDL-binding protein. It appears that the two glycoproteins have a simi lar molecular mass and are comparably affected by treatment with the d ifferent glycosidases. Incubation with trypsin resulted in a reduction in the estimated molecular mass of about 25 kDa for both the oxLDL-bi nding protein and macrosialin. These results indicate that the oxLDL-b inding protein and macrosialin are identical, suggesting a role for ma crosialin in modified LDL catabolism.