Biogenesis and regulation of insulin-responsive vesicles containing GLUT4

Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA.
Current opinion in cell biology (Impact Factor: 8.74). 04/2010; 22(4):506-12. DOI: 10.1016/
Source: PubMed

ABSTRACT Insulin regulates the trafficking of GLUT4 glucose transporters in fat and muscle cells. In unstimulated cells, GLUT4 is sequestered intracellularly in small, insulin-responsive vesicles. Insulin stimulates the translocation of these vesicles to the cell surface, inserting the transporters into the plasma membrane to enhance glucose uptake. Formation of the insulin-responsive vesicles requires multiple interactions among GLUT4, IRAP, LRP1, and sortilin, as well as recruitment of GGA and ACAP1 adaptors and clathrin. Once formed, the vesicles are retained within unstimulated cells by the action of TUG, Ubc9, and other proteins. In addition to acting at other steps in vesicle recycling, insulin releases this retention mechanism to promote the translocation and fusion of the vesicles at the cell surface.

  • [Show abstract] [Hide abstract]
    ABSTRACT: While insulin acutely stimulates glucose uptake by promotion of GLUT4 translocation from intracellular compartments to the plasma membrane in adipocytes and muscles, long-term insulin stimulation causes GLUT4 depletion particularly prominent in the insulin-responsive GLUT4-storage compartment (GSC). This effect is caused mainly by accelerated lysosomal degradation of GLUT4 although the mechanism is not fully defined. Here we show that insulin acutely induced dissociation of retromer components from the low-density microsomal (LDM) membranes of 3T3-L1 adipocytes, which was accompanied by disruption of the interaction of Vps35 with sortilin. This insulin effect was dependent on the activity of protein kinase CK2 but neither phosphatidylinositol 3-kinase nor extracellular signal-regulated kinase 1/2. Knockdown of Vps26 decreased GLUT4 to a level comparable to that with insulin stimulation for 4 hours. Vps35 with a mutation in the CK2 phosphorylation motif (Vps35-Ser7Ala) was resistant to insulin-induced dissociation from the LDM membrane and its overexpression attenuated GLUT4 downregulation with insulin. Furthermore, insulin-generated hydrogen peroxide was an upstream mediator of the insulin action on retromer and GLUT4. These results suggested that insulin-generated oxidative stress switches GLUT4 sorting direction to lysosomes through inhibition of the retromer function in a CK2-dependent manner.
    Journal of Biological Chemistry 11/2013; 289(35). DOI:10.1074/jbc.M113.533240 · 4.60 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Increases in insulin-mediated glucose uptake following endurance training (ET) and sprint interval training (SIT) have in part been attributed to concomitant increases in glucose transporter 4 (GLUT4) protein content in skeletal muscle. This study used an immunofluorescence microscopy method to investigate changes in subcellular GLUT4 distribution and content following ET and SIT. Percutaneous muscle biopsy samples were taken from the m. vastus lateralis of 16 sedentary males in the overnight fasted state before and after 6 weeks of ET and SIT. An antibody was fully validated and used to show large (> 1 μm) and smaller (<1 μm) GLUT4-containing clusters. The large clusters likely represent trans-Golgi network stores and the smaller clusters endosomal stores and GLUT4 storage vesicles (GSVs). Density of GLUT4 clusters was higher at the fibre periphery especially in perinuclear regions. A less dense punctate distribution was seen in the rest of the muscle fibre. Total GLUT4 fluorescence intensity increased in type I and type II fibres following both ET and SIT. Large GLUT4 clusters increased in number and size in both type I and type II fibres, while the smaller clusters increased in size. The greatest increases in GLUT4 fluorescence intensity occurred within the 1 μm layer immediately adjacent to the PM. The increase in peripheral localisation and protein content of GLUT4 following ET and SIT is likely to contribute to the improvements in glucose homeostasis observed after both training modes.
    07/2014; 2(7). DOI:10.14814/phy2.12085
  • [Show abstract] [Hide abstract]
    ABSTRACT: Insulin causes the exocytic translocation of GLUT4 glucose transporters to stimulate glucose uptake in fat and muscle. Previous results support a model in which TUG traps GLUT4 in intracellular, insulin-responsive vesicles termed GLUT4 storage vesicles (GSVs). Insulin triggers TUG cleavage to release the GSVs; GLUT4 then recycles through endosomes during ongoing insulin exposure. The TUG C-terminus binds a GSV anchoring site comprising Golgin-160 and possibly other proteins. Here, we report that the TUG C-terminus is acetylated. The TUG C-terminal peptide bound the Golgin-160-associated protein, ACBD3 (acyl-CoA binding domain containing 3), and acetylation reduced binding of TUG to ACBD3, but not to Golgin-160. Mutation of the acetylated residues impaired insulin-responsive GLUT4 trafficking in 3T3-L1 adipocytes. ACBD3 overexpression enhanced the translocation of GSV cargos, GLUT4 and IRAP, and ACBD3 was required for intracellular retention of these cargos in unstimulated cells. SIRT2, a NAD+-dependent deacetylase, bound TUG and deacetylated the TUG peptide. SIRT2 overexpression reduced TUG acetylation and redistributed GLUT4 and IRAP to the plasma membrane in 3T3-L1 adipocytes. Mutation of the acetylated residues in TUG abrogated these effects. In mice, SIRT2 deletion increased TUG acetylation and proteolytic processing. During glucose tolerance tests, glucose disposal was enhanced in SIRT2 knockout mice, compared to wildtype controls, without any effect on insulin concentrations. Together, these data support a model in which TUG acetylation modulates its interaction with Golgi matrix proteins and is regulated by SIRT2. Moreover, acetylation of TUG enhances its function to trap GSVs within unstimulated cells, and enhances insulin-stimulated glucose uptake. Copyright © 2015, The American Society for Biochemistry and Molecular Biology.
    Journal of Biological Chemistry 01/2015; DOI:10.1074/jbc.M114.603977 · 4.60 Impact Factor

Full-text (2 Sources)

Available from
May 19, 2014