Influence of Apolipoprotein A-I Domain Structure on Macrophage Reverse Cholesterol Transport in Mice

Objective: The goal of this study was to determine the influence of apolipoprotein A-I (apoA-I) tertiary structure domain properties on the antiatherogenic properties of the protein. Two chimeric hybrids with the N-terminal domains swapped (human-mouse apoA-I and mouse-human apoA-I) were expressed in apoA-I-null mice with adeno-associated virus (AAV) and used to study macrophage reverse cholesterol transport (RCT) in vivo.

Methods And Results: The different apoA-I variants were expressed in apoA-I-null mice that were injected with [H(3)]cholesterol-labeled J774 mouse macrophages to measure RCT. Significantly more cholesterol was removed from the macrophages and deposited in the feces via the RCT pathway in mice expressing mouse-H apoA-I compared with all other groups. Analysis of the individual components of the RCT pathway demonstrated that mouse-H apoA-I promoted ATP-binding cassette transporter A1-mediated cholesterol efflux more efficiently than all other variants, as well as increasing the rate of cholesterol uptake into liver cells.

Conclusions: The structural domain properties of apoA-I affect the ability of the protein to mediate macrophage RCT. Replacement of the N-terminal helix bundle domain in the human apoA-I with the mouse apoA-I counterpart causes a gain of function with respect to macrophage RCT, suggesting that engineering some destabilization into the N-terminal helix bundle domain or increasing the hydrophobicity of the C-terminal domain of human apoA-I would enhance the antiatherogenic properties of the protein.