During the insulin-mediated adipocyte conversion of confluent 3T3-L1 cells, glutamine synthetase (GS) specific activity increases more than 100-fold. Incubation of the adipocytes for 24 h with dibutyryl cAMP (Bt2cAMP) plus theophylline decreases GS specific activity by greater then 70 percent. Incubation of 3T3 adiopocytes with hydrocortisone increases GS activity by 1.5-to 2-fold. Immunotitration of GS activity from 3T3 adipocytes indicates that observed changes are due to changes in the cellular content of GS molecules. The Bt2cAMP-mediated decrease in glutamine synthetase activity results from a decrease in the synthesis rate and an increase in the degradation rate of the enzyme. Our current effects are directed toward determining the effects of insulin, glucocorticoids and other effectors on the rate of GS synthesis and degradation. In addition, we will attempt to determine whether GS in 3T3-L1 adipocytes might be subject to regulation by covalent modification.
| Bhandari, B; Saini, K S; Miller, R E (1991) Glycerol 3-phosphate dehydrogenase gene expression in cultured 3T3-L1 adipocytes: regulation by insulin, dexamethasone and dibutyryl cAMP at the level of mRNA abundance, transcription and mRNA stability. Mol Cell Endocrinol 76:71-7 |
| Bhandari, B; Roesler, W J; DeLisio, K D et al. (1991) A functional promoter flanks an intronless glutamine synthetase gene. J Biol Chem 266:7784-92 |
| Bhandari, B; Beckwith, K D; Miller, R E (1988) Cloning, nucleotide sequence, and potential regulatory elements of the glutamine synthetase gene from murine 3T3-L1 adipocytes. Proc Natl Acad Sci U S A 85:5789-93 |
| Bhandari, B; Wilson, R H; Miller, R E (1987) Insulin and dexamethasone stimulate transcription of an amplified glutamine synthetase gene in Chinese hamster ovary cells. Mol Endocrinol 1:403-7 |
