Models for ABCA1-mediated lipid efflux. (a) ABCA1 promotes phospholipid (PL)and cholesterol (FC) efflux from a membrane domain in a single step. (b) ABCA1, located in a border region between liquid and cholesterol-rich liquid–ordered domains (rafts), promotes phospholipid and cholesterol efflux to apoA-I. (c) ABCA1 first promotes phospholipid efflux to apoA-I to form intermediate complexes, which then remove cholesterol from rafts.