| Background |
ABCG1 (ATP-binding cassette sub-family G member 1), a transporter protein primarily involved in macrophage lipid homeostasis, localizes to intracellular compartments associated with ER /Golgi membranes, and its expression is highest in macrophage-rich tissue such as spleen, lung, and thymus as well as in brain. ABCG1 form heterodimers with heterologous ABCG partners and functional heterodimerization with ABCG4 has been of great interest because brain cells, mainly neurons and astrocytes, depict high expression of both transporters. ABCG1 is involved in the export of a variety of lipids (in conjunction with ABCA1) including cholesterol and phospholipids from macrophages to HDL. Macrophage lipid export is the first step in the reverse cholesterol transport pathway that exports cholesterol from peripheral cells to circulating lipoproteins for eventual excretion via liver. Cholesterol export to lipoprotein acceptors is compromised in macrophage foam cells, one of the early hallmarks of atherosclerosis. Moreover, ABCG1 plays role in T cells/inflammation, brain lipid homeostasis and its expression increases in macrophages of Tangier disease patients.
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