Purification of the human THP-1 monocyte-macrophage triglyceride-rich lipoprotein receptor

Previously we reported that human blood-borne and THP-1 monocyte-macrophages have an apolipoprotein E- and lipoprotein lipase-independent, high affinity, specific binding site for the uptake and degradation of hypertriglyceridemic VLDL and plasma chylomicrons distinct from the LDL receptor gene family and the acetyl LDL receptor (Gianturco et al., J. Lipid Res. 35:1674-1687, 1994). Ligand blot analyses identified two cell-surface, structurally related membrane binding proteins as receptor candidates of M(r) approximately 200 kDa and M(r) approximately 235 kDa which are converted into a single ligand binding species of intermediate mobility upon reduction. We now report a approximately 1200-fold purification of the reduced candidate receptor protein from cultured THP-1 monocytes.