Insulin stimulates glucose uptake in its target tissues (fat, heart, and skeletal muscle) mainly or entirely via translocation of glucose transporting activity from an intracellular pool to the cell surface. The protein responsible for the insulin-sensitive glucose transport, GLUT4, has been identified and cloned. The mechanism of the translocation process remains unknown. It is crucially important to find an answer to this question, because it will explain the fundamental principles of insulin action, and, in addition, will shed light on the molecular bases of insulin resistance in diabetes mellitus. To approach this problem, we started with characterization of the intracellular GLUT4-containing membrane compartment (vesicles) in basal and in insulin-treated rat adipocytes. We have shown that, besides GLUT4, this compartment incorporates the IGF-II/Man-6-P receptor, the transferrin receptor, the novel aminopeptidase gpl60 and a number of minor components. Thus, several proteins which (may) participate in cellular nutrition and metabolism are co-localized in the same intracellular membrane vesicles. All these proteins recycle between GLUT4-vesicles and their functional site, the plasma membrane, in an insulin dependent fashion. Their hormone-sensitive recruitment to the cell surface represents the major mechanism hat regulates intracellular uptake of glucose, iron, and other metabolites. The question arises of whether insulin stimulates translocation of the whole pre-existing compartment (""""""""GLUT4-vesicles""""""""), or different component proteins of GLUT4-vesicles recycle separately. In the last case, insulin is likely to cause formation of new transport vesicles which deliver their individual cargo to the cell surface via unidentified pathways. To discriminate between these two possibilities is the first major goal of the project. Besides the cell surface translocation of GLUT4 and co-localized proteins, insulin administration induces other major changes in adipocyte vesicular traffic. For example, it stimulates fluid-phase endocytosis, internalization of insulin receptors and, likely, lysosomal targeting of the endocytosed ligands. Thus, the second major goal is to provide a comparative study of different trafficking events in order to determine their common biochemical requirements as well as possible differences. Eventually, this work will provide us with a detailed picture of intracellular protein traffic in adipocytes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK052057-04
Application #
6138040
Study Section
Metabolism Study Section (MET)
Program Officer
Haft, Carol R
Project Start
1997-02-28
Project End
2001-12-31
Budget Start
2000-01-01
Budget End
2000-12-31
Support Year
4
Fiscal Year
2000
Total Cost
$146,867
Indirect Cost
Name
Boston University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
604483045
City
Boston
State
MA
Country
United States
Zip Code
02118
Zaarur, Nava; Pan, Xiang; Kandror, Konstantin V (2018) Detection of Detergent-sensitive Interactions Between Membrane Proteins. J Vis Exp :
Boesze-Battaglia, Kathleen; Walker, Lisa P; Dhingra, Anuradha et al. (2017) Internalization of the Active Subunit of the Aggregatibacter actinomycetemcomitans Cytolethal Distending Toxin Is Dependent upon Cellugyrin (Synaptogyrin 2), a Host Cell Non-Neuronal Paralog of the Synaptic Vesicle Protein, Synaptogyrin 1. Front Cell Infect Microbiol 7:469
Pan, Xiang; Zaarur, Nava; Singh, Maneet et al. (2017) Sortilin and retromer mediate retrograde transport of Glut4 in 3T3-L1 adipocytes. Mol Biol Cell 28:1667-1675
Singh, Maneet; Shin, Yu-Kyong; Yang, Xiaoqing et al. (2015) 4E-BPs Control Fat Storage by Regulating the Expression of Egr1 and ATGL. J Biol Chem 290:17331-8
Chakrabarti, Partha; Kandror, Konstantin V (2015) The role of mTOR in lipid homeostasis and diabetes progression. Curr Opin Endocrinol Diabetes Obes 22:340-6
Singh, Maneet; Kaur, Rajween; Lee, Mi-Jeong et al. (2014) Fat-specific protein 27 inhibits lipolysis by facilitating the inhibitory effect of transcription factor Egr1 on transcription of adipose triglyceride lipase. J Biol Chem 289:14481-7
Chakrabarti, Partha; Kim, Ju Youn; Singh, Maneet et al. (2013) Insulin inhibits lipolysis in adipocytes via the evolutionarily conserved mTORC1-Egr1-ATGL-mediated pathway. Mol Cell Biol 33:3659-66
Huang, Guanrong; Buckler-Pena, Dana; Nauta, Tessa et al. (2013) Insulin responsiveness of glucose transporter 4 in 3T3-L1 cells depends on the presence of sortilin. Mol Biol Cell 24:3115-22
Kim, Ju Youn; Kandror, Konstantin V (2012) The first luminal loop confers insulin responsiveness to glucose transporter 4. Mol Biol Cell 23:910-7
Karki, Shakun; Chakrabarti, Partha; Huang, Guanrong et al. (2011) The multi-level action of fatty acids on adiponectin production by fat cells. PLoS One 6:e28146

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