ABCG1 (ATP-Binding Cassette Subfamily G Member 1 Mature HDL Efflux Gene)
ABCG1 (ATP binding cassette subfamily G member 1; HGNC:73, NCBI Gene ID 9619) is a human locus mapped to chromosome band 21q22.3 that encodes half-transporter ATP-binding cassette sterol exporter ABCG1 (678 aa; homodimer). ABCG1 acts in cholesterol & 7-ketocholesterol efflux to mature spherical HDL particles & pulmonary surfactant homeostasis, together with ABCA1 (Nascent HDL Efflux Transporter Gene), APOA1 (Apolipoprotein A-I Gene), and SCARB1 (SR-B1 HDL Receptor Gene). Encodes the homodimeric ABCG1 sterol transporter that exports cholesterol and oxysterols from macrophages onto mature HDL particles.
Acts synergistically with ABCA1 to prevent macrophage foam-cell atherosclerosis & pulmonary alveolar proteinosis
Gene Structure & Expression
Genomic Organization & Cytogenetic Locus: 23-exon gene on chromosome 21q22.3 driven by LXR/RXR response elements and repressed by miR-33a/b, encoding a reverse-orientation ABC half-transporter (one N-terminal cytoplasmic nucleotide-binding domain followed by one 6-helix C-terminal transmembrane domain) that must homodimerize to form an active transporter.
Cellular & Tissue Expression Profile: Highly expressed in tissue macrophages (especially arterial intimal macrophages and pulmonary alveolar macrophages), vascular endothelial cells, pancreatic islet beta cells, lymphocytes, and brain neurons and glia.
Molecular Function & Pathways
Biochemical & Physiological Mechanism: Works in sequential tandem with ABCA1: whereas ABCA1 lipidates lipid-free ApoA-I to create nascent discoidal HDL, ABCG1 redistributes intracellular sterols (including cytotoxic dietary oxysterols such as 7-ketocholesterol) to the outer leaflet of the plasma membrane for desorption onto mature spherical alpha-HDL2 and HDL3 particles.
Clinical & Therapeutic Significance
Human Genetic Variants & Disease Phenotypes: Combined deficiency of ABCA1 and ABCG1 in macrophages or vascular endothelium causes massive cholesteryl ester and oxysterol accumulation, NLRP3 inflammasome activation, myeloproliferation, pulmonary lipidosis resembling alveolar proteinosis, and accelerated atherosclerosis, while inside pancreatic beta cells ABCG1 maintains insulin secretory granule cholesterol content.
Therapeutic & Clinical Pharmacology: Co-induced alongside ABCA1 by liver X receptor (LXR) modulators, PPAR-gamma-LXR cascades, and miR-33 antisense inhibitors in cardiometabolic and neuroinflammatory research.