The binding in vitro of modified LDL to the intermediate filament protein vimentin

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