GLUT4 is the primary glucose transport protein responsible for insulin-mediated glucose uptake in mammalian tissues. It is the predominant facilitative glucose transporter isoform expressed in muscle and in adipose tissue. As little as a 2- to 3-fold increase in GLUT4 expression has been shown to markedly enhance glucose uptake in both normal and diabetic mouse models, correcting the diabetic phenotype in the latter. Modulation of GLUT4 levels is therefore an attractive molecular target for therapeutic intervention insulin-resistant states, including diabetes mellitus. A straightforward approach to enhance GLUT4 expression is to increase the transcription rate of the gene. Glut4 gene expression is transcriptionally regulated in physiologic states such insulin-deficiency and exercise, and it is likely that a pharmacological intervention can be developed to enhance glut4 gene transcription provided that a suitable system for rapid screening of these compounds is developed. To reach these goals, we must first understand the molecular basis for transcriptional regulation of the glut4 gene. Using transgenic mice, we have shown that cis-elements regulating the human glut4 promoter are located within 895 bp located immediately 5' of the transcription initiation site. This region contains two major regulatory domains, referred to as Domain I and the MEF2 domain. In transgenic mice, these elements function cooperatively to support regulated expression of a reporter gene in GLUT4-expressing tissues. The MEF2 domain binds isoforms of the Myocyte Enhancer Factor 2 (MEF2) family of transcription factors, while Domain I binds GEF (Glut4 Enhancer Factor), a novel activator of transcription recently cloned in our laboratory. We propose that both the tissue-specific and the hormonal and metabolic regulation of the GLUT4 gene are carried out through these 2 regulatory domains. The primary goal of this proposal to understand the mechanisms of regulation of tissue-specific, hormonal and metabolic regulation of glut4 gene transcription. To achieve these goals, the following aims are proposed: 1) to define the functional domains of GEF; 2) examine the interaction between GEF and MEF2 proteins in cultured cells; and 3) to determine the mechanisms by which GEF and MEF2 regulate GIut4 gene regulation in transgenic mouse models of insulin deficiency or insulin resistance.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK062341-04
Application #
6904565
Study Section
Metabolism Study Section (MET)
Program Officer
Blondel, Olivier
Project Start
2002-08-15
Project End
2007-07-31
Budget Start
2005-08-01
Budget End
2007-07-31
Support Year
4
Fiscal Year
2005
Total Cost
$264,732
Indirect Cost
Name
University of Oklahoma Health Sciences Center
Department
Biochemistry
Type
Schools of Medicine
DUNS #
878648294
City
Oklahoma City
State
OK
Country
United States
Zip Code
73117
Griesel, Beth A; Weems, Juston; Russell, Robert A et al. (2010) Acute inhibition of fatty acid import inhibits GLUT4 transcription in adipose tissue, but not skeletal or cardiac muscle tissue, partly through liver X receptor (LXR) signaling. Diabetes 59:800-7
Jensen, Ellis B; Zheng, Donghai; Russell, Robert A et al. (2009) Regulation of GLUT4 expression in denervated skeletal muscle. Am J Physiol Regul Integr Comp Physiol 296:R1820-8
Sparling, David P; Griesel, Beth A; Weems, Juston et al. (2008) GLUT4 enhancer factor (GEF) interacts with MEF2A and HDAC5 to regulate the GLUT4 promoter in adipocytes. J Biol Chem 283:7429-37
Sparling, David P; Griesel, Beth A; Olson, Ann Louise (2007) Hyperphosphorylation of MEF2A in primary adipocytes correlates with downregulation of human GLUT4 gene promoter activity. Am J Physiol Endocrinol Metab 292:E1149-56
McGee, Sean L; Sparling, David; Olson, Ann-Louise et al. (2006) Exercise increases MEF2- and GEF DNA-binding activity in human skeletal muscle. FASEB J 20:348-9
Eyster, Craig A; Duggins, Quwanza S; Gorbsky, Gary J et al. (2006) Microtubule network is required for insulin signaling through activation of Akt/protein kinase B: evidence that insulin stimulates vesicle docking/fusion but not intracellular mobility. J Biol Chem 281:39719-27
Eyster, Craig A; Duggins, Quwanza S; Olson, Ann Louise (2005) Expression of constitutively active Akt/protein kinase B signals GLUT4 translocation in the absence of an intact actin cytoskeleton. J Biol Chem 280:17978-85
Knight, John B; Eyster, Craig A; Griesel, Beth A et al. (2003) Regulation of the human GLUT4 gene promoter: interaction between a transcriptional activator and myocyte enhancer factor 2A. Proc Natl Acad Sci U S A 100:14725-30
Olson, Ann Louise; Knight, John B (2003) Regulation of GLUT4 expression in vivo and in vitro. Front Biosci 8:s401-9
Olson, Ann Louise; Eyster, Craig A; Duggins, Quwanza S et al. (2003) Insulin promotes formation of polymerized microtubules by a phosphatidylinositol 3-kinase-independent, actin-dependent pathway in 3T3-L1 adipocytes. Endocrinology 144:5030-9