Dissociation of GLUT4 Translocation and Insulin-stimulated Glucose Transport in Transgenic Mice Overexpressing GLUT1 in Skeletal Muscle*
- From the Departments of ‡Medicine, §Cell Biology and Physiology, and ‖Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110
Abstract
Overexpression of the human GLUT1 glucose transporter protein in skeletal muscle of transgenic mice results in large increases in basal glucose transport and metabolism, but impaired stimulation of glucose transport by insulin, contractions, or hypoxia (Gulve, E. A., Ren, J.-M., Marshall, B. A., Gao, J., Hansen, P. A., Holloszy, J. O., and Mueckler, M. (1994)J. Biol. Chem. 269, 18366–18370). This study examined the relationship between glucose transport and cell-surface glucose transporter content in isolated skeletal muscle from wild-type and GLUT1-overexpressing mice using 2-deoxyglucose, 3-O-methylglucose, and the 2-N-[4-(1-azi-2,2,2-trifluoroethyl)benzoyl]-1,3-bis(d-mannos-4-yloxy)-2-propylamine exofacial photolabeling technique. Insulin (2 milliunits/ml) stimulated a 3-fold increase in 2-deoxyglucose uptake in extensor digitorum longus muscles of control mice (0.47 ± 0.07 μmol/ml/20 min in basal muscle versus 1.44 μmol/ml/20 min in insulin-stimulated muscle; mean ± S.E.). Insulin failed to increase 2-deoxyglucose uptake above basal rates in muscles overexpressing GLUT1 (4.00 ± 0.40 μmol/ml/20 min in basal muscle versus 3.96 ± 0.37 μmol/ml/20 min in insulin-stimulated muscle). A similar lack of insulin stimulation in muscles overexpressing GLUT1 was observed using 3-O-methylglucose. However, the magnitude of the insulin-stimulated increase in cell-surface GLUT4 photolabeling was nearly identical (∼3-fold) in wild-type and GLUT1-overexpressing muscles. This apparently normal insulin-stimulated translocation of GLUT4 in GLUT1-overexpressing muscle was confirmed by immunoelectron microscopy. Our findings suggest that GLUT4 activity at the plasma membrane can be dissociated from the plasma membrane content of GLUT4 molecules and thus suggest that the intrinsic activity of GLUT4 is subject to regulation.
Footnotes
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↵* This work was supported in part by National Institutes of Health Grants DK38495 and DK50332 (to M. M.), Grant DK18986 (to J. O. H.), and Grant DK02339 (to B. A. M.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ Supported by a mentor-based postdoctoral fellowship from the American Diabetes Association.
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↵** Supported by the John Henry and Bernadine Foster Foundation and Scholar of the Child Health Research Center of Excellence in Developmental Biology at Washington University School of Medicine (National Institutes of Health Grant HD 33688).
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↵‡ To whom correspondence should be addressed: Dept. of Cell Biology and Physiology, 660 S. Euclid Ave., St. Louis, MO 63110. Tel.: 314-362-4160; Fax: 314-362-7463; E-mail: mike{at}cellbio.wustl.edu.
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↵1 P. A. Hansen, B. A. Marshall, M. Mueckler, and J. O. Holloszy, unpublished observations.
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↵2 The abbreviations used are: ATB-[2-3H]BMPA, 2-N-[4-(1-azi-2,2,2-trifluoroethyl)benzoyl]-1,3-bis(d-mannos-4-yloxy)-2-propylamine; EDL, extensor digitorum longus; KHB, Krebs-Henseleit bicarbonate buffer; 2-DG, 2-deoxy-d-glucose; 3-MG, 3-O-methyl-d-glucose; PBS, phosphate-buffered saline.
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- Received November 20, 1997.
- Revision received March 9, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
