Serum Amyloid A Protein Generates Preβ1 High-Density Lipoprotein from α-Migrating High-Density Lipoprotein

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Abstract
Serum amyloid A protein (SAA), an acute-phase reactant in reactive amyloidosis, has high affinity for high-density lipoprotein (HDL). When SAA is added to HDL, SAA displaces apolipoprotein A-I (apoA-I) and phospholipid from the HDL particles. These dissociated components may form preβ1-HDL because free apoA-I can associate with phospholipid to become a lipoprotein having preβ mobility. To determine whether SAA generates preβ1-HDL from α-migrating HDL, we investigated the effects of recombinant SAA on HDL subfraction concentration using nondenaturing two-dimensional gradient gel electrophoresis. When we added SAA (0.5 mg/mL) to plasma, the preβ1-HDL concentration increased by 164% (from 4.7% ± 1.3% to 12.4% ± 3.2% of apoA-I, p < 0.005). The increase in preβ1-HDL was proportional to the dose of SAA. When we added SAA to a column of Sepharose beads coupled to the isolated HDL (α-migrating HDL), preβ1-HDL was dissociated from the column together with the SAA-associated HDL. In summary, we demonstrate that SAA generates preβ1-HDL from α-migrating HDL. We speculate that SAA-mediated HDL remodeling may take place in inflammation.