ATP hydrolysis-dependent conformational changes in the extracellular domain of ABCA1 are associated with apoA-I binding.

ATP-binding cassette protein A1 (ABCA1) plays a major role in cholesterol homeostasis and high-density lipoprotein (HDL) metabolism. Although it is predicted that apolipoprotein A-I (apoA-I) directly binds to ABCA1, the physiological importance of this interaction is still controversial and the conformation required for apoA-I binding is unclear. In this study, the role of the two nucleotide-binding domains (NBD) of ABCA1 in apoA-I binding was determined by inserting a TEV protease recognition sequence in the linker region of ABCA1.

The COP9 signalosome controls ubiquitinylation of ABCA1.

ATP-binding cassette protein A1 (ABCA1) mediates the transfer of cellular free cholesterol and phospholipids to apolipoprotein A-I (apoA-I), an extracellular acceptor in plasma, to form high-density lipoprotein (HDL). ABCA1 has been suggested to be degraded by proteasome in cholesterol-loaded macrophages, however, the mechanism and regulation of proteasomal degradation of ABCA1 remain unclear. In this study, we analyzed the putative interaction between ABCA1 and COP9 signalosome (CSN), a key molecule in controlling protein ubiquitination and deubiquitination.

Retroendocytosis pathway of ABCA1/apoA-I contributes to HDL formation.

ATP-binding cassette protein A1 (ABCA1) mediates transfer of cellular free cholesterol and phospholipids to apolipoprotein A-I (apoA-I), an extracellular acceptor in plasma, to form high-density lipoprotein (HDL). It is currently unknown to what extent ABCA1 endocytosis and recycling contribute to the HDL formation. To address this issue, we expressed human ABCA1 constructs with either an extracellular HA tag or an intracellular GFP tag in cells, and used this system to characterize endocytosis and recycling of ABCA1 and apoA-I.