title: Involvement of vesicular H+-ATPase in insulin-stimulated glucose transport in 3T3-F442A adipocytes.
abstract: In secretory cells, osmotic swelling of secretory granules is proposed to be an intermediate step in exocytic fusion of the granules with the plasma membrane. For osmotic swelling of the granule, a H (+) gradient generated by vacuolar-type H (+) -ATPase (V-ATPase) may be a driving force for accumulation of K (+) via its exchange with H (+) , concurrent with accumulation of Cl (-) and H(2)O. Here, we investigated whether a similar chemiosmotic mechanism is involved in the insulin-stimulated recruitment of GLUT4 to the plasma membrane in 3T3-F442A adipocytes. Incubating cells in a hypo-osmotic medium significantly increased 2-deoxy glucose (2-DG) uptake and the plasma membrane GLUT4 content (possibly via induction of osmotic swelling of GLUT4-containing vesicles (G4V)) and also potentiated the insulin-stimulated 2-DG uptake. Promotion of the G4V membrane ionic permeability using nigericin, an electroneutral K (+) /H (+) exchange ionophore, increased 2-DG uptake and the plasma membrane GLUT4 content. However, co-treatment with nigericin and insulin did not show an additive effect. Bafilomycin A(1), a diagnostically specific inhibitor of V-ATPase, inhibited insulin- and nigericin-stimulated 2-DG uptake. Immunoadsorption plus immunoblotting demonstrated that GLUT4 and V-ATPase co-localize in the same intracellular membranes. Together, these results indicate that V-ATPases in the G4V membrane may play an important role in the insulin-stimulated exocytic fusion of G4V with the plasma membrane via its participation in osmotic swelling of the vesicle.
authors.affiliation: Department of Physiology, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Young Ok
authors.initials: YO
authors.lastname: Choi
authors.forename: Jong-Ha
authors.initials: JH
authors.lastname: Park
authors.forename: Young Sook
authors.initials: YS
authors.lastname: Song
authors.forename: Wan
authors.initials: W
authors.lastname: Lee
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Moriyama
authors.forename: Han
authors.initials: H
authors.lastname: Choe
authors.forename: Chae Hun
authors.initials: CH
authors.lastname: Leem
authors.forename: Yeon Jin
authors.initials: YJ
authors.lastname: Jang
mesh_terms: D016475:3T3 Cells; D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D003470:Culture Media / Q000494:pharmacology; D003847:Deoxyglucose / Q000493:pharmacokinetics; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology*; D007476:Ionophores / Q000494:pharmacology; D018942:Macrolides / Q000494:pharmacology; D051379:Mice; D009550:Nigericin / Q000494:pharmacology; D009994:Osmolar Concentration; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000502:physiology*