The overall goal is to gain an understanding of insulin receptor metabolism (synthesis and degradation), and elucidate the mechanism(s) mediating insulin-induced cell-surface receptor regulation in physiological and hyperinsulinemic states. We plan to couple our recently developed technique for maintaining isolated adipocytes in primary culture with established methods for biosynthetically and externally labeling insulin receptors. In addition, we intend to use our technique for rapidly and accurately determining the cellular distribution of receptors. This methodology will subserve four specific aims; (1) To delineate the insulin receptor biosynthetic pathway. This will include studies on the structure and function of receptors during processing and maturation, the time-course of receptor transit, and post-translational modification of receptors. (2) To explore the receptor degradative pathway. Specifically, we plan to establish receptor turnover rates for both cell-surface and newly synthesized receptors, and examine how and where cell-surface receptors are degraded. (3) To elucidate the mechanism(s) by which insulin regulates the net number of cell-surface receptors. This will be accomplished by determining whether insulin-induced changes in surface receptors (up and down-regulation) are mediated by changes in the rate of receptor synthesis, receptor degradation, or by a redistribution of receptors (cell-surface vs. intracellular). Other studies will explore the lag-time preceding insulin-induced receptor loss, with special emphasis on the characteristics and mechanisms by which insulin """"""""triggers"""""""" cellular events so that receptor regulation can be manifested in the absence of ligand. Additional experiments will attempt to separate genetic control from environmental regulation of insulin receptors. And lastly, (4) to confirm that insulin regulates the rate at which insulin receptors are endocytosed, and explore the mechanism involved in this process. This will include studies on the specificity of this affect, and the site of regulation (receptor vs. post-receptor regulation). Hopefully, these combined studies will provide new insights into the mechanism of insulin action and advance our understanding of certain pathophysiological, insulin resistant states characterized by hyperinsulinemia and receptor down-regulation, such as in obesity and Type II diabetes mellitus.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK038754-04
Application #
3238225
Study Section
Metabolism Study Section (MET)
Project Start
1986-09-01
Project End
1991-06-30
Budget Start
1989-07-01
Budget End
1991-06-30
Support Year
4
Fiscal Year
1989
Total Cost
Indirect Cost
Name
University of Tennessee Health Science Center
Department
Type
Schools of Medicine
DUNS #
941884009
City
Memphis
State
TN
Country
United States
Zip Code
38163
Traxinger, R R; Marshall, S (1991) Coordinated regulation of glutamine:fructose-6-phosphate amidotransferase activity by insulin, glucose, and glutamine. Role of hexosamine biosynthesis in enzyme regulation. J Biol Chem 266:10148-54
Marshall, S; Bacote, V; Traxinger, R R (1991) Discovery of a metabolic pathway mediating glucose-induced desensitization of the glucose transport system. Role of hexosamine biosynthesis in the induction of insulin resistance. J Biol Chem 266:4706-12
Marshall, S; Bacote, V; Traxinger, R R (1991) Complete inhibition of glucose-induced desensitization of the glucose transport system by inhibitors of mRNA synthesis. Evidence for rapid turnover of glutamine:fructose-6-phosphate amidotransferase. J Biol Chem 266:10155-61
Traxinger, R R; Marshall, S (1990) Glucose regulation of insulin receptor affinity in primary cultured adipocytes. J Biol Chem 265:18879-83
Traxinger, R R; Marshall, S (1990) Suitability of 2-deoxyglucose for measuring initial rates of glucose uptake in isolated adipocytes. Biochem Int 22:607-15
Marshall, S; Monzon, R (1989) Amino acid regulation of insulin action in isolated adipocytes. Selective ability of amino acids to enhance both insulin sensitivity and maximal insulin responsiveness of the protein synthesis system. J Biol Chem 264:2037-42
Marshall, S (1989) Kinetics of insulin action on protein synthesis in isolated adipocytes. Ability of glucose to selectively desensitize the glucose transport system without altering insulin stimulation of protein synthesis. J Biol Chem 264:2029-36
Traxinger, R R; Marshall, S (1989) Recovery of maximal insulin responsiveness and insulin sensitivity after induction of insulin resistance in primary cultured adipocytes. J Biol Chem 264:8156-63
Garvey, W T; Huecksteadt, T P; Monzon, R et al. (1989) Dexamethasone regulates the glucose transport system in primary cultured adipocytes: different mechanisms of insulin resistance after acute and chronic exposure. Endocrinology 124:2063-73
Traxinger, R R; Marshall, S (1989) Role of amino acids in modulating glucose-induced desensitization of the glucose transport system. J Biol Chem 264:20910-6

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