CONTROL OF LIPOGENIC ENZYMES BIOSYNTHESIS IN 3T3-L1 CELL

The overall goal of this research program is to determine the molecular
basis for the regulation of the biosynthesis of several lipogenic enzymes.
The amounts of these enzymes are markedly altered in liver and fat cells in
three fundamentally important states: (a) expression of cell
differentiation and developmental programs; (b) regulation of target-cell
metabolism and function by the hormones insulin, T3, epinephrine and
glucagon; and (c) in a dietary paradigm involving a period of starvation
followed by refeeding with a high carbohydrate/low fat diet. Three
enzymes, ATP-citrate lyase (ACL), malic enzyme (ME) and glycerol
3-phosphate dehydrogenase (GPD) have been chosen for study. They are
representative examples of enzymes in the direct saturated fatty acid
synthesis pathway, a set of essential NADPH producting enzymes and the
enzymic linkage between glycolytic and lipogenic pathways, respectively.
These enzymes are members of a limited group of functionally related
moderate to low abundance enzyme proteins that are often (but not always)
regulated in a coordinate manner in many variations of the physiologically
important states described above. Little is currently known about the
molecular mechanisms underlying this coordinate control. Therefore,
studies on the transcriptional and post-transcriptional regulation of these
genes, the determination of the structure of coding and non-coding regions
of ACL, ME and GPD genes and ultimately, the characterization of specific
regulatory sequences in regions flanking the genes will provide new
information and insights on processes involved in mammalian cell
differentiation and the phenomena which direct target cells to coordinately
reset their levels of a family of enzymes in response to hormones and
nutrients. Studies will be performed on murine 3T3-L1 preadipocytes and