In this study we have used wortmannin, a highly specific inhibitor of phosphatidylinositol (PI) 3-kinase, to assess the role of this enzyme on GLUT1 glucose carrier distribution and glucose transport activity in myoblasts from two skeletal-muscle cell lines, L6E9 and Sol8. As detected in L6E9 cells, myoblasts exhibited basal and insulin-stimulated PI 3-kinase activities. Incubation of intact myoblasts with wortmannin resulted in a marked inhibition of both basal and insulin-stimulated PI 3-kinase activities. L6E9 and Sol8 myoblasts showed basal and insulin-stimulated glucose transport activities, both of them inhibited by wortmannin in a dose-dependent manner (IC50 approximately 10-20 nM). Concomitantly, immunofluorescence analysis revealed that 1 h treatment with wortmannin led to a dramatic intracellular accumulation of GLUT1 carriers (the main glucose transporter expressed in L6E9 and Sol8 myoblasts) in both cell systems. The effect of wortmannin on GLUT1 cellular redistribution was independent of the presence of insulin. The cellular distribution of two structural plasma-membrane components such as beta 1-integrin or the alpha 1 subunit of the Na(+)-K(+)-ATPase were unaffected by wortmannin in both the absence and the presence of insulin. As a whole, our results indicate that PI 3-kinase is necessary to basal and insulin-stimulated glucose transport in L6E9 and Sol8 myoblasts. Moreover, immunofluorescence assays suggest that in both cellular models there is a constitutive GLUT 1 trafficking pathway (independent of insulin) that involves PI 3-kinase and which, when blocked, locks GLUT1 in a perinuclear compartment.
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December 1995
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Research Article|
December 01 1995
Disruption of GLUT1 glucose carrier trafficking in L6E9 and Sol8 myoblasts by the phosphatidylinositol 3-kinase inhibitor wortmannin
P Kaliman;
P Kaliman
1Departament de Bioquímica i Fisiologia, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain
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F Viñals;
F Viñals
1Departament de Bioquímica i Fisiologia, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain
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X Testar;
X Testar
1Departament de Bioquímica i Fisiologia, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain
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M Palacín;
M Palacín
1Departament de Bioquímica i Fisiologia, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain
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A Zorzano
A Zorzano
1Departament de Bioquímica i Fisiologia, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1995 The Biochemical Society, London
1995
Biochem J (1995) 312 (2): 471–477.
Citation
P Kaliman, F Viñals, X Testar, M Palacín, A Zorzano; Disruption of GLUT1 glucose carrier trafficking in L6E9 and Sol8 myoblasts by the phosphatidylinositol 3-kinase inhibitor wortmannin. Biochem J 1 December 1995; 312 (2): 471–477. doi: https://doi.org/10.1042/bj3120471
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