L6 muscle cells survive long-term (18 h) disruption of oxidative phosphorylation by the mitochondrial uncoupler 2,4-dinitrophenol (DNP) because, in response to this metabolic stress, they increase their rate of glucose transport. This response is associated with an elevation of the protein content of glucose transporter isoforms GLUT3 and GLUT1, but not GLUT4. Previously we have reported that the rise in GLUT1 expression is likely to be a result of de novo biosynthesis of the transporter, since the uncoupler increases GLUT1 mRNA levels. Unlike GLUT1, very little is known about how interfering with mitochondrial ATP production regulates GLUT3 protein expression. Here we examine the mechanisms employed by DNP to increase GLUT3 protein content and glucose uptake in L6 muscle cells. We report that, in contrast with GLUT1, continuous exposure to DNP had no effect on GLUT3 mRNA levels. DNP-stimulated glucose transport was unaffected by the protein-synthesis inhibitor cycloheximide. The increase in GLUT3 protein mediated by DNP was also insensitive to cycloheximide, paralleling the response of glucose uptake, whereas the rise in GLUT1 protein levels was blocked by the inhibitor. The GLUT3 glucose transporter may therefore provide the majority of the glucose transport stimulation by DNP, despite elevated levels of GLUT1 protein. The half-lives of GLUT3 and GLUT1 proteins in L6 myotubes were determined to be about 15 h and 6 h respectively. DNP prolonged the half-life of both proteins. After 24 h of DNP treatment, 88% of GLUT3 protein and 57% of GLUT1 protein had not turned over, compared with 25% in untreated cells. We conclude that the long-term stimulation of glucose transport by DNP arises from an elevation of GLUT3 protein content associated with an increase in GLUT3 protein half-life. These findings suggest that disruption of the oxidative chain of L6 muscle cells leads to an adaptive response of glucose transport that is distinct from the insulin response, involving specific glucose transporter isoforms that are regulated by different mechanisms.
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August 1998
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Research Article|
August 01 1998
Unique mechanism of GLUT3 glucose transporter regulation by prolonged energy demand: increased protein half-life
Zayna A. KHAYAT;
Zayna A. KHAYAT
*Programme in Cell Biology, The Hospital for Sick Children, 555 University Ave., Toronto, Ontario, Canada, M5G 1X8, and Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada, M5S 1A8
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Anthony L. McCALL;
Anthony L. McCALL
†Departments of Medicine, Cell and Developmental Biology and Neurology, Oregon Health Sciences University, Veterans Affairs Medical Center, Portland, OR 07201, U.S.A.
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Amira KLIP
Amira KLIP
1
*Programme in Cell Biology, The Hospital for Sick Children, 555 University Ave., Toronto, Ontario, Canada, M5G 1X8, and Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada, M5S 1A8
1To whom correspondence should be addressed, at The Hospital for Sick Children (e-mail amira@sickkids.on.ca).
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Publisher: Portland Press Ltd
Received:
March 27 1998
Revision Received:
May 01 1998
Accepted:
May 12 1998
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1998
1998
Biochem J (1998) 333 (3): 713–718.
Article history
Received:
March 27 1998
Revision Received:
May 01 1998
Accepted:
May 12 1998
Citation
Zayna A. KHAYAT, Anthony L. McCALL, Amira KLIP; Unique mechanism of GLUT3 glucose transporter regulation by prolonged energy demand: increased protein half-life. Biochem J 1 August 1998; 333 (3): 713–718. doi: https://doi.org/10.1042/bj3330713
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