Our goal is to understand the molecular basis of two control mechanisms that contribute to the onset of obesity and its complications, notably NIDDM. These mechanisms include: l. control of expression of the obese (leptin) gene in the adipocyte, and 2. transcriptional control of the stearoylCoA desaturase genes (SCD1 and SCD2) in the adipocyte and hepatocyte. Leptin, a secretory protein expressed only by adipose tissue, regulates appetite (via receptors in the hypothalamus) and energy metabolism. The 3T3-L1 adipocyte system, pioneered in this laboratory, will be used as a cell culture model that mimics adipocytes in vivo. Our studies show that leptin is expressed/secreted by 3T3-L1 adipocytes and its expression is dramatically regulated in vivo by changes in physiological state. We have cloned/sequenced the regulatory 5' flanking region of the gene for use in the studies proposed. We plan to: * characterize the factors that regulate expression of the leptin gene and its mRNA, and * identify critical cis-regulatory elements within the leptin gene promoter that control its expression. We will identify and characterize the cognate trans-acting nuclear factors that interact with the cis- elements and determine how these interactions regulate transcription. The SCD genes catalyze delta9 cis-desaturation of fatty acids, and thereby determine the degree of unsaturation and functional properties of membrane phospholipids and storage/secretory triacylglycerols). Expression of the SCD1 and SCD2 genes is induced during adipocyte differentiation and is feed-back inhibited by polyunsaturated fatty acids (notably arachidonate) in certain cell types. We have cloned, sequenced and characterized the mouse SCD1 and SCD2 genes. A preadipocyte -repressive element (or PRE) and its binding protein (PRE-BP1) was discovered that maintains the SCD2 gene in the repressed state prior to differentiation. A similar, but distinct, element and binding protein have been identified for the SCD1 gene. We plan to: * sequence, express and characterize PRE-BP1 (SCD2) and the PRE-BP for the SCD1 gene. * investigate their site-specific binding interactions and repression/derepression mechanisms and role in negative-feedback control by arachidonate, and * determine the physiological basis (preadipocyte differentiation, negative feedback, etc.) for derepression and repression of the SCD1 and SCD2 genes.
| Cooke, D W; Lane, M D (1999) The transcription factor nuclear factor I mediates repression of the GLUT4 promoter by insulin. J Biol Chem 274:12917-24 |
| Cornelius, P; MacDougald, O A; Lane, M D (1994) Regulation of adipocyte development. Annu Rev Nutr 14:99-129 |
| Swick, A G; Lane, M D (1992) Identification of a transcriptional repressor down-regulated during preadipocyte differentiation. Proc Natl Acad Sci U S A 89:7895-9 |
| Bamberger, M J; Lane, M D (1990) Possible role of the Golgi apparatus in the assembly of very low density lipoprotein. Proc Natl Acad Sci U S A 87:2390-4 |
| Bamberger, M J; Lane, M D (1988) Assembly of very low density lipoprotein in the hepatocyte. Differential transport of apoproteins through the secretory pathway. J Biol Chem 263:11868-78 |
