Involvement of Vesicular H+-ATPase in Insulin-Stimulated Glucose Transport in 3T3-F442A Adipocytes

[摘要] References(42)Cited-By(5)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 H2O. 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 A1, 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.

[学科分类] 内分泌与代谢学

[关键词] Vacuolar-type H+;-ATPase;Chemiosmotic mechanism;Exocytosis;GLUT4;Insulin