This application represents a continuation of a Program Project whose overall theme is the metabolism of high density lipoprotein (HDL) as related to the development of atherosclerosis. The mechanisms by which HDL mediates reverse cholesterol transport (RCT), the process whereby cholesterol is removed from peripheral cells and transported to the liver for clearance from the body, will be investigated. Experiments will be conducted in a coordinated fashion at the molecular, cellular and whole animal levels. The goal is to delineate the contribution of HDL's function in RCT to the cardioprotective properties of this lipoprotein. This Program Project consists of three closely related projects: Dr. Rothblat's project involves an investigation of how the HDL receptors, scavenger receptor class B, type I and ATP-binding cassette transporter A1 (ABCA1), mediate cholesterol flux between cells and serum components. The contributions of different serum factors to the efflux of cholesterol from cells and the RCT pathway will be defined. Dr. Phillips' project proposes to elucidate the properties of the domains of apolipoprotein (apo) A-I responsible for phospholipid binding and interaction with ABCA1 and SR-BI. The molecular mechanisms by which apo A-I delivers and removes cholesterol to and from cell plasma membranes will be investigated. Dr. Rader's project focuses on the use of in vivo methods in mice to investigate the structure-function properties of apo A-I with respect to its ability to promote RCT and reduce atherosclerosis. Emphasis will be placed on acute overexpression models of apo A-I and the importance of expression of SR-BI and ABCA1 will be examined. The group of investigators comprising this Program Project share similar interests and goals in lipid and lipoprotein metabolism while providing broad scientific expertise. The scientific disciplines encompassed by these investigators include biochemistry, cell biology, molecular biology and animal physiology. The three specific projects are supported by three core laboratories: 1) Administrative/Central Service Core, 2) Tissue Culture Core and 3) Lipoprotein Core.