APOA1 (Apolipoprotein A-I HDL Scaffold & Reverse Cholesterol Transport Gene)
APOA1 (apolipoprotein A1; HGNC:600, NCBI Gene ID 335) is a human locus mapped to chromosome band 11q23.3 that encodes apolipoprotein A-I amphipathic alpha-helical protein (243 mature aa; 28 kDa). APOA1 acts in high-density lipoprotein (HDL) biogenesis, ABCA1 cholesterol efflux & LCAT activation, together with ABCA1 (ATP-Binding Cassette Subfamily A Member 1), ABCG1 (ATP-Binding Cassette Subfamily G Member 1), and SCARB1 (Scavenger Receptor Class B Member 1 / SR-B1). Encodes apolipoprotein A-I, the primary structural protein of high-density lipoprotein (HDL) and cofactor for LCAT in reverse cholesterol transport.
Approved Symbol
APOA1
Chromosomal Locus
11q23.3
Encoded Product
Apolipoprotein A-I amphipathic alpha-helical protein (243 mature aa; 28 kDa)
Null variants cause HDL deficiency & Tangier-like neuropathy; missense variants cause hereditary APOA1 amyloidosis
Gene Structure & Expression
Genomic Organization & Cytogenetic Locus: 4-exon gene located at chromosome 11q23.3 at the 5-prime end of the APOA1-APOC3-APOA4-APOA5 gene cluster, encoding a 267-residue preproprotein cleaved to a 243-amino-acid mature protein composed of ten tandem 11- and 22-residue class A amphipathic alpha-helical repeats.
Cellular & Tissue Expression Profile: Synthesized and secreted abundantly by hepatic hepatocytes (~70%) and small intestinal enterocytes (~30%), constituting approximately 70% of the total protein mass of plasma high-density lipoproteins (HDL).
Molecular Function & Pathways
Biochemical & Physiological Mechanism: Lipid-poor pre-beta-1 ApoA-I interacts with the ATP-binding cassette transporter ABCA1 on peripheral macrophages and hepatocytes to accept unesterified cholesterol and phospholipids, forming discoidal nascent HDL, and subsequently activates lecithin-cholesterol acyltransferase (LCAT) to esterify cholesterol into spherical mature alpha-HDL for hepatic delivery via SR-B1 (SCARB1).
Clinical & Therapeutic Significance
Human Genetic Variants & Disease Phenotypes: Biallelic nonsense or deletion variants cause familial ApoA-I deficiency with virtually absent plasma HDL-cholesterol, corneal opacities, planar xanthomas, and premature coronary atherosclerosis, whereas specific amyloidogenic missense variants (such as p.Gly26Arg Iowa) cause autosomal dominant hereditary systemic ApoA-I amyloidosis affecting liver, kidney, and heart; conversely, the Italian variant ApoA-I Milano (p.Arg173Cys) forms disulfide-linked dimers with enhanced antioxidant capacity.
Therapeutic & Clinical Pharmacology: Transcriptional induction of APOA1 is mediated by PPAR-alpha agonists (fibrates) and BET bromodomain inhibitor apabetalone (RVX-208), while reconstituted human ApoA-I infusions (CSL112) have been evaluated following acute myocardial infarction.