title: AS160 phosphotyrosine-binding domain constructs inhibit insulin-stimulated GLUT4 vesicle fusion with the plasma membrane.
abstract: AS160 (TBC1D4) is a known Akt substrate that is phosphorylated downstream of insulin action and that leads to regulated traffic of GLUT4. As GLUT4 vesicle fusion with the plasma membrane is a highly regulated step in GLUT4 traffic, we investigated whether AS160 and 14-3-3 interactions are involved in this process. Fusion was inhibited by a human truncated AS160 variant that encompasses the first N-terminal phosphotyrosine-binding (PTB) domain, by either of the two N-terminal PTB domains, and by a tandem construct of both PTB domains of rat AS160. We also found that in vitro GLUT4 vesicle fusion was strongly inhibited by the 14-3-3-quenching inhibitors R18 and fusicoccin. To investigate the mode of interaction of AS160 and 14-3-3, we examined insulin-dependent increases in the levels of these proteins on GLUT4 vesicles. 14-3-3γ was enriched on insulin-stimulated vesicles, and its binding to AS160 on GLUT4 vesicles was inhibited by the AS160 tandem PTB domain construct. These data suggest a model for PTB domain action on GLUT4 vesicle fusion in which these constructs inhibit insulin-stimulated 14-3-3γ interaction with AS160 rather than AS160 phosphorylation.
authors: Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom.
authors: Françoise
authors: F
authors: Koumanov
authors: Judith D
authors: JD
authors: Richardson
authors: Beverley A
authors: BA
authors: Murrow
authors: Geoffrey D
authors: GD
authors: Holman
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000737:chemistry* / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000737:chemistry*; D006801:Humans; D007328:Insulin / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000737:chemistry*; D011485:Protein Binding; D020033:Protein Isoforms; D051381:Rats
chemical_list: D020690:GTPase-Activating Proteins; D051275:Glucose Transporter Type 4; D007328:Insulin; D020033:Protein Isoforms; C495692:SLC2A4 protein, human; C495694:Slc2a4 protein, rat; C518767:TBC1D4 protein, human; C533101:TBC1D4 protein, rat; D019000:Phosphotyrosine; D005947:Glucose