The insulin receptor serves to focus the hormone on particular target tissues as well as to initiate the response of these cells to the hormone. However, it is not known how this signal is transmitted. An understanding of this process is important since many non-insulin dependent diabetics are defective in responding to insulin. Recently it has been demonstrated that the receptor is itself an enzyme, it phosphorylates other proteins on tyrosine residues. This enzymatic activity of the receptor may be important in mediating the responses of cells to the hormone. To further study this process, we have developed monoclonal antibodies that inhibit this enzymatic activity of the receptor. These antibodies will be used to study the role of this activity in insulin action. These antibodies will be microinjected into cells to see if they block various biological effects of insulin. In addition, these antibodies will be utilized to identify proteins in the vicinity of the receptor and thereby identify potential substrates of the receptor kinase. Finally, the antigenic sites recognized by these antibodies will be mapped. After responding to insulin, a cell must terminate its response. One mechanism for accomplishing this is to degrade the hormone. Two enzymes have the ability of degrading the hormone in vitro. One enzyme, called glutathione-insulin transhydrogenase, can be readily purified. Both polyclonal and monoclonal antibodies to this enzyme have been produced and its cDNA has been cloned. However, this enzyme appears to contribute little to the degradation of insulin in the intact cell. Another enzyme which has not been previously purified appears to contribute more to the intracellular degradation of insulin. Recently we have isolated several monoclonal antibodies to this enzyme. These antibodies will be used to examine the structure of this enzyme, its role in insulin degradation and possible interactions with the insulin receptor. In addition, these antibodies will be utilized to isolate the cDNA that encodes the insulin degrading enzyme. An understanding of the enzyme(s) involved in insulin degradation may allow the design of specific inhibitors of the enzyme(s). These inhibitors could be used to treat certain rare patients who have excessive insulin degradation or even to treat patients who have low levels of insulin to make this insulin more active by preventing its degradation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK034926-05
Application #
3233176
Study Section
Metabolism Study Section (MET)
Project Start
1984-07-01
Project End
1991-04-30
Budget Start
1988-05-01
Budget End
1989-04-30
Support Year
5
Fiscal Year
1988
Total Cost
Indirect Cost
Name
Stanford University
Department
Type
Schools of Medicine
DUNS #
800771545
City
Stanford
State
CA
Country
United States
Zip Code
94305
Kortylewski, Marcin; Feld, Florian; Kruger, Klaus-Dieter et al. (2003) Akt modulates STAT3-mediated gene expression through a FKHR (FOXO1a)-dependent mechanism. J Biol Chem 278:5242-9
Faridi, Jesika; Fawcett, Janet; Wang, Lihong et al. (2003) Akt promotes increased mammalian cell size by stimulating protein synthesis and inhibiting protein degradation. Am J Physiol Endocrinol Metab 285:E964-72
Wang, Lihong; Fraley, Cresson D; Faridi, Jesika et al. (2003) Inorganic polyphosphate stimulates mammalian TOR, a kinase involved in the proliferation of mammary cancer cells. Proc Natl Acad Sci U S A 100:11249-54
Barthel, Andreas; Kruger, Klaus-Dieter; Roth, Richard A et al. (2002) Concentration-dependent stimulatory and inhibitory effect of troglitazone on insulin-induced fatty acid synthase expression and protein kinase B activity in 3T3-L1 adipocytes. Naunyn Schmiedebergs Arch Pharmacol 365:290-5
Barthel, Andreas; Schmoll, Dieter; Kruger, Klaus-Dieter et al. (2002) Regulation of the forkhead transcription factor FKHR (FOXO1a) by glucose starvation and AICAR, an activator of AMP-activated protein kinase. Endocrinology 143:3183-6
Barthel, A; Schmoll, D; Kruger, K D et al. (2001) Differential regulation of endogenous glucose-6-phosphatase and phosphoenolpyruvate carboxykinase gene expression by the forkhead transcription factor FKHR in H4IIE-hepatoma cells. Biochem Biophys Res Commun 285:897-902
Vainshtein, I; Kovacina, K S; Roth, R A (2001) The insulin receptor substrate (IRS)-1 pleckstrin homology domain functions in downstream signaling. J Biol Chem 276:8073-8
Iynedjian, P B; Roth, R A; Fleischmann, M et al. (2000) Activation of protein kinase B/cAkt in hepatocytes is sufficient for the induction of expression of the gene encoding glucokinase. Biochem J 351 Pt 3:621-7
Mirza, A M; Kohn, A D; Roth, R A et al. (2000) Oncogenic transformation of cells by a conditionally active form of the protein kinase Akt/PKB. Cell Growth Differ 11:279-92
Nakatani, K; Sakaue, H; Thompson, D A et al. (1999) Identification of a human Akt3 (protein kinase B gamma) which contains the regulatory serine phosphorylation site. Biochem Biophys Res Commun 257:906-10

Showing the most recent 10 out of 77 publications