Transports lipids such as glucosylceramides from the outer to the inner leaflet of lamellar granules (LGs) membrane, whereby the lipids are finally transported to the keratinocyte periphery via the trans-Golgi network and LGs and released to the apical surface of the granular keratinocytes to form lipid lamellae in the stratum corneum of the epidermis, which is essential for skin barrier function (PubMed:18957418, PubMed:27551807, PubMed:24293640, PubMed:20489143, PubMed:18802465). In the meantime, participates in the transport of the lamellar granules-associated proteolytic enzymes, in turn regulates desquamation and keratinocyte differentiation (PubMed:27551807, PubMed:20489143). Furthermore, is essential for the regulation of cellular cholesterol homeostasis by regulating ABCA1-dependent cholesterol efflux from macrophages through interaction with NR1H2 and ABCA1 (PubMed:18802465, PubMed:23931754). Plays pleiotropic roles in regulating glucose stimulated insulin secretion from beta cells, regulating the morphology and fusion of insulin granules, lipid raft abundance and the actin cytoskeleton (PubMed:32072744). Also involved in lung surfactant biogenesis (PubMed:18632686). ATP + H2O + phospholipidSide 1 = ADP + phosphate + phospholipidSide 2. ATP + beta-D-glucosylceramide(in) + H2O = ADP + beta-D-glucosylceramide(out) + H(+) + phosphate Interacts with NR1H2 and ABCA1; this interaction is required for ABCA1 localization to the cell surface and is necessary for its normal activity and stability. Localizes in the limiting membrane of the lamellar granules (LGs). Trafficks from the Golgi apparatus to the lamellar granules (LGs) at the cell periphery in the uppermost granular layer keratinocytes where ABCA12-positive LGs fuse with the keratinocyte-cell membrane to secrete their lipid content to the extracellular space of the stratum corneum. Co-localizes through the Golgi apparatus to the cell periphery with glucosylceramide. Expressed in a number of other tissues besides skin, including heart, intestine, stomach, and kidney (PubMed:24293640). Expressed mainly in the granular layer of the skin (PubMed:18632686). Expressed in lung (PubMed:18632686). Expressed in alpha and beta cells of pancreatic islets (PubMed:32072744). At 18.5 dpc highly expressed in the epidermis, and weakly in the stomach. Up-regulated during barrier recovery. Multifunctional polypeptide with two homologous halves, each containing a hydrophobic membrane-anchoring domain and an ATP binding cassette (ABC) domain. Homozygous knockout mice for Abca12 are born with a thickened epidermis and die shortly after birth, as water rapidly evaporates from their skin (PubMed:18957418). In a mouse model for harlequin ichthyosis (HI), homozygous knockout mice are smaller and die within a few hours and their entire body are covered of erythematous skin, making their skin less flexible. The entire skin surface is covered with thick scales and some mice develop skin fissures and eversions of the lips (eclabium). At 18.5 dpc, fetuses develop taut and shiny skin without normal skin folds and show contractures of the limbs. The lungs of the present model mice show signs of alveolar collapse (PubMed:18632686). Belongs to the ABC transporter superfamily. ABCA family.