Identification of a GPI-anchored type HDL-binding protein on human macrophages

To identify the HDL3-binding proteins on human macrophages, we examined the involvement of GPI-anchored protein in the binding of HDL3, and tried to p urify HDL3-binding protein. From membrane fractions of macrophages, we obta ined 80- and 130-kDa HDL3-binding proteins by ligand blotting. Treatment of macrophages with phosphatidylinositol-specific phospholipase C (PI-PLC) si gnificantly decreased the specific HDL3-binding in a dose-dependent manner. Furthermore, treatment with mannosamine, which blocks GPI-anchor formation , decreased specific HDL3-binding in a dose-dependent manner. PI-PLC treatm ent released from the cells the proteins with an M-r of 80 kDa, which could also bind HDL3. PI-PLC as well as mannosamine treatment markedly reduced c holesterol efflux from macrophages in association with the decreased HDL-bi nding. Using HDL3-affinity chromatography, we purified 80-kDa GPI-anchored type HDL3-binding protein. In summary, we demonstrate the implication of 80 -kDa GPI-anchored protein in the binding of HDL3 to human macrophages, whic h might have some role in reverse cholesterol transport. (C) 2000 Academic Press.