ABCA1 (ATP-binding cassette subfamily A member 1, CERP) is a transporter protein that modulates phospholipid homeostasis, cellular cholesterol. ABCA1 is necessary for proper cholesterol metabolism and transport in the central nervous system. It has highest expression in the liver, adipose tissue and the small intestine, and is otherwise found throughout the body. Mutations in ABCA1 lead to the rare Tangier’s disease, described by a massive reduction in high density lipoprotein in the body and which can lead to neuropathy and cardiovascular disease. Downregulation of ABCA1 leads to atherogenesis through a disruption of cholesterol transport within cells and is a factor in the pathogenesis of atherosclerosis and macular degeneration. Upregulation of ABCA1 has been found to reduce amyloid deposition in mouse models of Alzheimer’s disease. In immunohistochemistry of normal tissue, ABCA1 has membranous and cytoplasmic positivity in tissues throughout the body. References: Cell Metabolism. 17 (4): 549–61, PMID: 23562078; J Clin Invest. 2008;118(2):671–682, DOI: doi.org/10.1172/JCI33622; J Neurosci. 2009 Mar 18; 29(11): 3579–3589, PMID: 19295162