title: GLUT4 recycles via a trans-Golgi network (TGN) subdomain enriched in Syntaxins 6 and 16 but not TGN38: involvement of an acidic targeting motif.
abstract: Insulin stimulates glucose transport in fat and muscle cells by triggering exocytosis of the glucose transporter GLUT4. To define the intracellular trafficking of GLUT4, we have studied the internalization of an epitope-tagged version of GLUT4 from the cell surface. GLUT4 rapidly traversed the endosomal system en route to a perinuclear location. This perinuclear GLUT4 compartment did not colocalize with endosomal markers (endosomal antigen 1 protein, transferrin) or TGN38, but showed significant overlap with the TGN target (t)-soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) Syntaxins 6 and 16. These results were confirmed by vesicle immunoisolation. Consistent with a role for Syntaxins 6 and 16 in GLUT4 trafficking we found that their expression was up-regulated significantly during adipocyte differentiation and insulin stimulated their movement to the cell surface. GLUT4 trafficking between endosomes and trans-Golgi network was regulated via an acidic targeting motif in the carboxy terminus of GLUT4, because a mutant lacking this motif was retained in endosomes. We conclude that GLUT4 is rapidly transported from the cell surface to a subdomain of the trans-Golgi network that is enriched in the t-SNAREs Syntaxins 6 and 16 and that an acidic targeting motif in the C-terminal tail of GLUT4 plays an important role in this process.
authors.affiliation: Institute for Molecular Biosciences, University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia.
authors.forename: Annette M
authors.initials: AM
authors.lastname: Shewan
authors.forename: Ellen M
authors.initials: EM
authors.lastname: van Dam
authors.forename: Sally
authors.initials: S
authors.lastname: Martin
authors.forename: Tang Bor
authors.initials: TB
authors.lastname: Luen
authors.forename: Wanjin
authors.initials: W
authors.lastname: Hong
authors.forename: Nia J
authors.initials: NJ
authors.lastname: Bryant
authors.forename: David E
authors.initials: DE
authors.lastname: James
mesh_terms: D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism; D051275:Glucose Transporter Type 4; D006801:Humans; D007328:Insulin / Q000378:metabolism; D053590:Interleukin 1 Receptor Antagonist Protein; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins; D021382:Protein Sorting Signals; D021381:Protein Transport / Q000502:physiology; D050765:Qa-SNARE Proteins; D051381:Rats; D012795:Sialoglycoproteins / Q000378:metabolism; D051438:Syntaxin 16; D021601:trans-Golgi Network / Q000378:metabolism*
chemical_list: D051275:Glucose Transporter Type 4; C507763:IL1RN protein, human; C507764:Il1rn protein, mouse; D007328:Insulin; D053590:Interleukin 1 Receptor Antagonist Protein; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D021382:Protein Sorting Signals; D050765:Qa-SNARE Proteins; C495692:SLC2A4 protein, human; D012795:Sialoglycoproteins; C495693:Slc2a4 protein, mouse; C495694:Slc2a4 protein, rat; D051438:Syntaxin 16; C072237:TGOLN2 protein, human; C513047:Tgoln1 protein, mouse; C513046:Tgoln2 protein, mouse; C513045:Tgoln2 protein, rat