Lipoprotein lipase (LPL) strongly links native and oxidized low density lipoprotein particles to decorin-coated collagen - Roles for both dimeric andmonomeric forms of LPL

Low density lipoprotein (LDL) and oxidized LDL are associated with collagen in the arterial intima, where the collagen is coated by the small proteogl ycan decorin. When incubated in physiological ionic conditions, decorin-coa ted collagen bound only small amounts of native and oxidized LDL, the inter action being weak. When decorin-coated collagen was first allowed to bind l ipoprotein lipase (LPL), binding of native and oxidized LDL increased drama tically (23- and 7-fold, respectively). This increase depended on strong in teractions between LPL that was bound to the glycosaminoglycan chains of th e collagen-bound decorin and native and oxidized LDL (kDa 12 and 5.9 nM res pectively). To distinguish between binding to monomeric (inactive) and dime ric (catalytically active) forms of LPL, affinity chromatography on heparin columns was conducted, which showed that native LDL bound to the monomeric LPL, whereas oxidized LDL, irrespective of the type of modification (Cu2+, 2,2'-azobis(2-amidinopropane)hydrochloride, hypochlorite, or soybean 15-li poxygenase), bound preferably to dimeric LPL, However, catalytic activity o f LPL was not required for binding to oxidized LDL. Finally, immunohistoche mistry of atherosclerotic lesions of human coronary arteries revealed speci fic areas in which LDL, LPL, decorin, and collagen type I were present. The results suggest that LPL can retain LDL in atherosclerotic lesions along d ecorin-coated collagen fibers.