Fig. 1.

Effect of the introduction of a Cys residue and attachment of an Alexa Fluor probe on the ability of apolipoprotein A-I (apoA-I) to promote apolipoprotein-mediated cholesterol efflux from cultured macrophages. RAW264.7 cells were labeled for 24 h with ³H-cholesterol as described in Methods. After removal of labeling media and three washes, medium containing 10 μg/ml of lipid-free acceptor with 0.3 mM cAMP, to upregulate ATP binding cassette transporter A-1 (ABCA1), was added to the cells for 24 h. All Cys mutants represented as acceptors in this figure have the Alexa Fluor 546 probe attached. The cholesterol efflux data are expressed as percentage of total cell ³H-cholesterol for cells whose lipids were extracted immediately after the washes that followed labeling (t₀). Error bars represent 1 SD of triplicate samples from one of three representative experiments. A one-way ANOVA was performed, and the asterisk indicates a significant difference from human plasma apoA-I (P < 0.001) by a Tukey-Kramer multiple comparison test.