title: Nigericin inhibits insulin-stimulated glucose transport in 3T3-L1 adipocytes.
abstract: We used nigericin, a K+/H+ exchanger, to test whether glucose transport in 3T3-L1 adipocytes was modulated by changes in intracellular pH. Our results showed that nigericin increased basal but decreased insulin-stimulated glucose uptake in a time- and dose-dependent manner. Whereas the basal translocation of GLUT1 was enhanced, insulin-stimulated GLUT4 translocation was inhibited by nigericin. On the other hand, the total amount of neither transporter protein was altered. The finding that insulin-stimulated phosphoinositide 3-kinase (PI 3-kinase) activity was not affected by nigericin implies that nigericin exerted its inhibition at a step downstream of PI 3-kinase activation. At maximal dose, nigericin rapidly lowered cytosolic pH to 6.7; however, this effect was transient and cytosolic pH was back to normal in 20 min. Removal of nigericin from the incubation medium after 20 min abolished its enhancing effect on basal but had little influence on its inhibition of insulin-stimulated glucose transport. Moreover, lowering cytosolic pH to 6.7 with an exogenously added HCl solution had no effect on glucose transport. Taken together, it appears that nigericin may inhibit insulin-stimulated glucose transport mainly by interfering with GLUT4 translocation, probably by a mechanism not related to changes in cytosolic pH.
authors.affiliation: Institute of Biochemistry, School of Life Sciences, National Yang-Ming University, Taipei, Taiwan, Republic of China.
authors.forename: Chih-Ying
authors.initials: CY
authors.lastname: Chu
authors.forename: Ying-Shun
authors.initials: YS
authors.lastname: Kao
authors.forename: Jim C
authors.initials: JC
authors.lastname: Fong
mesh_terms: D016475:3T3 Cells / Q000378:metabolism; D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003847:Deoxyglucose / Q000378:metabolism; D004347:Drug Interactions; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000032:analysis / Q000378:metabolism; D009124:Muscle Proteins; D009550:Nigericin / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism
chemical_list: D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495693:Slc2a4 protein, mouse; D003847:Deoxyglucose; D019869:Phosphatidylinositol 3-Kinases; D005947:Glucose; D009550:Nigericin; D002118:Calcium