Atherosclerosis remains the number one killer in the United States. Lipoproteins, which carry lipid in the plasma, have been linked to the etiology of atherosclerosis. The liver is an important organ for the synthesis and secretion of lipoproteins. To date, a considerable amount of information has been gathered on the molecular biology of apolipoproteins and where the genes for apoprotein synthesis are located on chromosomes. The packaging of lipoproteins in the Golgi has also been studied. However, very little is known about the mode of synthesis of lipoproteins. Specifically, answers to the questions how apoproteins are transported through the cell and how lipids are transported to apoproteins to form lipoproteins are not known. The concentration of different apoproteins in very low density lipoproteins will be quantified intracellularly. After establishment of intracellular pool sizes, the kinetics of transport of different apoproteins from one intracellular organelle to another will be studied. The study will use labelled amino acids to trace the different newly synthesized apolipoproteins. When the kinetics of transport of different apolipoproteins are known, we could determine if very low density lipoprotein biogenesis required a full complement of apolipoproteins or required only a few apolipoproteins. Through the use of different lipid labels (phosphate, glycerol, fatty acids), the nature and site of protein lipid interaction will be explored. Specifically, the order of addition of different lipids to apolipoproteins will be addressed. The studies will be complemented through the use of monoclonal antibodies. Two sets of monoclonal antibodies are sought. One set will recognize epitopes on apolipoproteins that are constantly exposed and another set will recognize lipid protein-binding sites. Through the differential use of these two sets of monoclonal antibodies, the site and nature of lipid interaction could be determined. These studies will provide important information on the early events of biogenesis of lipoproteins in the liver. Such information may allow a better understanding of post-translational control of very low density lipoproteins synthesis. This control process may provide a clue to controlling production of lipoproteins and thereby lowering blood levels and their attendant risk in atherosclerosis.
