title: Compartmentalization of the exocyst complex in lipid rafts controls Glut4 vesicle tethering.
abstract: Lipid raft microdomains act as organizing centers for signal transduction. We report here that the exocyst complex, consisting of Exo70, Sec6, and Sec8, regulates the compartmentalization of Glut4-containing vesicles at lipid raft domains in adipocytes. Exo70 is recruited by the G protein TC10 after activation by insulin and brings with it Sec6 and Sec8. Knockdowns of these proteins block insulin-stimulated glucose uptake. Moreover, their targeting to lipid rafts is required for glucose uptake and Glut4 docking at the plasma membrane. The assembly of this complex also requires the PDZ domain protein SAP97, a member of the MAGUKs family, which binds to Sec8 upon its translocation to the lipid raft. Exocyst assembly at lipid rafts sets up targeting sites for Glut4 vesicles, which transiently associate with these microdomains upon stimulation of cells with insulin. These results suggest that the TC10/exocyst complex/SAP97 axis plays an important role in the tethering of Glut4 vesicles to the plasma membrane in adipocytes.
authors.affiliation: Life Sciences Institute, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Inoue
authors.forename: Shian-Huey
authors.initials: SH
authors.lastname: Chiang
authors.forename: Louise
authors.initials: L
authors.lastname: Chang
authors.forename: Xiao-Wei
authors.initials: XW
authors.lastname: Chen
authors.forename: Alan R
authors.initials: AR
authors.lastname: Saltiel
mesh_terms: D041721:3T3-L1 Cells; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D002352:Carrier Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D000074288:Discs Large Homolog 1 Protein; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D051528:Guanylate Kinases; D007328:Insulin / Q000494:pharmacology; D008561:Membrane Fusion; D021962:Membrane Microdomains / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D034622:RNA Interference; D022161:Transport Vesicles / Q000378:metabolism*; D033921:Vesicular Transport Proteins; D020741:rho GTP-Binding Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D000074288:Discs Large Homolog 1 Protein; C000614189:Dlg1 protein, mouse; C502251:Exoc7 protein, mouse; D051275:Glucose Transporter Type 4; D007328:Insulin; D008565:Membrane Proteins; C490683:Sec6l1 protein, mouse; C489608:Sec8l1 protein, mouse; C495693:Slc2a4 protein, mouse; D033921:Vesicular Transport Proteins; D051528:Guanylate Kinases; C503260:Rhoq protein, mouse; D020741:rho GTP-Binding Proteins; D005947:Glucose