Membrane-associated proteins with specific binding properties to modified LDL were investigated in J774 macrophages and Mono Mac 6 sr cells. Ligand blotting of membrane proteins revealed a 54-kDa protein which bound oxidized and acetylated but not native LDL. The 54-kDa protein, isolated by 2D-PAGE, was identified as vimentin. (125)I-AcLDL bound to purified vimentin and desmin in a saturable manner, with an approximate K(d) of 1.7 x 10(-7) M (89 microgram/ml) and 8.0 x 10(-8) M (41 microgram/ml), respectively. Blots of vimentin mutant proteins with deletions in the positively charged N-terminal head domain showed that amino acids 26-39 are essential for the binding of AcLDL by vimentin. Taken together, our data indicate that vimentin binds modified LDL, but not native LDL, in a specific and saturable manner. Vimentin filaments extend throughout the cytoplasm as far as the inner surfaces of plasma and vesicular membranes. Vimentin may thus play a role in membrane-associated steps involved in the intracellular processing of oxidized LDL, contributing to its unregulated uptake and intracellular retention by cells of the atherogenic plaque.
Copyright 2000 Academic Press.