Evidence for the presence of lipid-free monomolecular apolipoprotein A-1 in plasma.

ABSTRACT: The first step in reverse cholesterol transport is a process by which lipid-free or lipid-poor apoA-1 removes cholesterol from cells through the action of ATP binding cassette transporter A1 at the plasma membrane. However the structure and composition of lipid-free or -poor apoA-1 in plasma remains obscure. We previously obtained a monoclonal antibody (MAb) that specifically recognizes apoA-1 in pre?1-HDL, the smallest apoA-1-containing particle in plasma, which we used to establish a pre?1-HDL ELISA. Here, we purified pre?1-HDL from fresh normal plasma using said antibody, and analyzed the composition and structure. ApoA-1 was detected, but neither phospholipid nor cholesterol were detected in the purified pre?1-HDL. Only globular, not discoidal, particles were observed by electron microscopy. In nondenaturing PAGE, no difference in the mobility was observed between the purified pre?1-HDL and original plasma pre?1-HDL, or between the pre?1-HDL and lipid-free apoA-1 prepared by delipidating HDL. In sandwich ELISA using two anti-pre?1-HDL MAbs, reactivity with intact plasma pre?1-HDL was observed in ELISA using two MAbs with distinct epitopes but no reactivity was observed in ELISA using a single MAb, and the same phenomenon was observed with monomolecular lipid-free apoA-1. These results suggest that plasma pre?1-HDL is lipid-free monomolecular apoA-1.

SUBMITTER: Miyazaki O 

PROVIDER: S-EPMC3886660 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature