title: Selective regulation of the perinuclear distribution of glucose transporter 4 (GLUT4) by insulin signals in muscle cells.
abstract: Insulin regulates glucose transporter 4 (GLUT4) availability at the surface of muscle and adipose cells. In L6 myoblasts, stably expressed GLUT4myc is detected mostly in a perinuclear region. In unstimulated cells, about half of perinuclear GLUT4myc colocalizes with the transferrin receptor (TfR). Insulin stimulation selectively decreased the perinuclear colocalization of GLUT4myc with TfR determined by 3D-reconstruction of fluorescence images. Perinuclear GLUT4myc adopted two main distributions defined morphometrically as 'conical' and 'concentric'. Insulin rapidly reduced the proportion of cells with conical in favor of concentric perinuclear GLUT4myc distributions in association with the gain in surface GLUT4myc. Upon removal of insulin, the GLUT4myc perinuclear distribution and surface levels reversed in parallel. In contrast, hypertonicity (which like insulin elevates surface GLUT4myc) did not elicit perinuclear GLUT4myc redistribution. Insulin also caused redistribution of perinuclear vesicle-associated membrane protein-2 (VAMP2), without alteration of perinuclear TfR and VAMP3. Inhibitory mutants of phosphatidylinositol-3 kinase (Deltap85) or Akt substrate AS160 (AS160-4P) prevented insulin-mediated perinuclear GLUT4myc redistribution. Tetanus toxin expression did not prevent the perinuclear GLUT4myc redistribution, suggesting that redistribution is independent of GLUT4myc fusion with the plasma membrane. We propose that insulin causes selective, dynamic relocalization of perinuclear GLUT4myc and VAMP2 and perinuclear GLUT4myc redistribution is a direct target of insulin-derived signals.
authors.affiliation: Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada.
authors.forename: Chandrasagar B
authors.initials: CB
authors.lastname: Dugani
authors.forename: Varinder K
authors.initials: VK
authors.lastname: Randhawa
authors.forename: Alex W P
authors.initials: AW
authors.lastname: Cheng
authors.forename: Nish
authors.initials: N
authors.lastname: Patel
authors.forename: Amira
authors.initials: A
authors.lastname: Klip
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism*; D021621:Imaging, Three-Dimensional; D007328:Insulin / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D032342:Muscle Cells / Q000378:metabolism*; D032446:Myoblasts / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D011990:Receptors, Transferrin / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013744:Tetanus Toxin / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D050988:Vesicle-Associated Membrane Protein 2 / Q000378:metabolism; D051040:Vesicle-Associated Membrane Protein 3 / Q000378:metabolism
chemical_list: D020690:GTPase-Activating Proteins; D051275:Glucose Transporter Type 4; D007328:Insulin; D011990:Receptors, Transferrin; D011993:Recombinant Fusion Proteins; D013744:Tetanus Toxin; C494706:Vamp2 protein, rat; D050988:Vesicle-Associated Membrane Protein 2; D051040:Vesicle-Associated Membrane Protein 3; C494951:vesicle-associated membrane protein 3, rat; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt