title: Sorting of GLUT4 into its insulin-sensitive store requires the Sec1/Munc18 protein mVps45.
abstract: Insulin stimulates glucose transport in fat and muscle cells by regulating delivery of the facilitative glucose transporter, glucose transporter isoform 4 (GLUT4), to the plasma membrane. In the absence of insulin, GLUT4 is sequestered away from the general recycling endosomal pathway into specialized vesicles, referred to as GLUT4-storage vesicles. Understanding the sorting of GLUT4 into this store is a major challenge. Here we examine the role of the Sec1/Munc18 protein mVps45 in GLUT4 trafficking. We show that mVps45 is up-regulated upon differentiation of 3T3-L1 fibroblasts into adipocytes and is expressed at stoichiometric levels with its cognate target-soluble N-ethylmaleimide-sensitive factor attachment protein receptor, syntaxin 16. Depletion of mVps45 in 3T3-L1 adipocytes results in decreased GLUT4 levels and impaired insulin-stimulated glucose transport. Using sub-cellular fractionation and an in vitro assay for GLUT4-storage vesicle formation, we show that mVps45 is required to correctly traffic GLUT4 into this compartment. Collectively our data reveal a crucial role for mVps45 in the delivery of GLUT4 into its specialized, insulin-regulated compartment.
authors.affiliation: Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Roccisana
authors.forename: Jessica B A
authors.initials: JB
authors.lastname: Sadler
authors.forename: Nia J
authors.initials: NJ
authors.lastname: Bryant
authors.forename: Gwyn W
authors.initials: GW
authors.lastname: Gould
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism; D000818:Animals; D022162:Cytoplasmic Vesicles / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D007328:Insulin / Q000502:physiology*; D051379:Mice; D051938:Munc18 Proteins / Q000378:metabolism; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000235:genetics; D011990:Receptors, Transferrin / Q000378:metabolism; D051438:Syntaxin 16 / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D051275:Glucose Transporter Type 4; D007328:Insulin; D051938:Munc18 Proteins; D034741:RNA, Small Interfering; D011990:Receptors, Transferrin; C495693:Slc2a4 protein, mouse; C497941:Stxbp2 protein, mouse; D051438:Syntaxin 16; D033921:Vesicular Transport Proteins; C498419:Vps45 protein, mouse; C496134:syntaxin 16, mouse