Cloning, tissue distribution and function of ABCA transporters

We cloned the full-length cDNA of ABCA2. ABCA2 is expressed predominantly in the oligodendrocytes in the brain, and onset of ABCA2 expression in the oligodendrocytes coincides with the appearance of thick myelin basic protein (MBP)-immunolabeled myelin segments. Oligodendrocytes produce the lamellar structure myelin, which is composed of phospholipids and specific myelin proteins. We also cloned ABCA3 from human lung and found that ABCA3 is expressed predominantly at the limiting membrane of the lamellar bodies of alveolar type II cells in human lung. Pulmonary surfactant, composed mainly of phospholipids and specific surfactant proteins, is stored as lamellar bodies before exocytosis into the alveolar space. These data suggest that ABCA2 and ABCA3 are involved in membrane transport of substrates such as the lipids that are closely linked to myelin and surfactant formation processes.