A new recombinant human apolipoprotein E mimetic peptide with high-density lipoprotein binding and function enhancing activity

Abstract

We generated a novel human apolipoprotein E (apoE)-mimetic peptide, designated EpK. EpK contains an N-terminal cysteine residue, a low-density lipoprotein receptor-binding fragment, a 6 × lysine linker and a lipid-binding fragment. The recombinant peptide was expressed in Escherichia coli, and purified with a chitin bead column followed by a Heparin Sepharose CL-6B column to yield pure peptide. EpK displayed high solubility in aqueous solution at neutral pH and adopted a low content of α-helical structure which was significantly increased in 2,2,2-trifluoroethanol or upon lipid binding. EpK retained similar 1,2-dimyristoyl(d54)-sn-glycero-3-phosphocholine binding activity as human apoE3 albeit with slower kinetics. Cell culture studies showed that EpK mediated cholesterol efflux from cholesterol-loaded primary murine macrophages with higher mass-based efficiency than human apoAI and human apoE3, and that EpK inhibited lipopolysaccharide (LPS)-induced proinflammatory cytokine expression in murine macrophages. When injected into apoE(-/-)mice, EpK predominantly associated with high-density lipoprotein (HDL), which was also shown in in vitro incubation experiments. Moreover, association of EpK with HDL enhanced the ability of HDL in mediating cholesterol efflux and suppressing LPS-induced proinflammatory cytokine expression in cholesterol-loaded human acute monocytic leukemia cell line (THP-1) macrophages. These data suggest that this novel recombinant apoE mimetic peptide enhances HDL function and harbors antiatherogenic potential.