Uncoupling protein 3 (UCP3) stimulates glucose uptake in muscle cells through a phosphoinositide 3-kinase-dependent mechanism.
UCP3 is a mitochondrial membrane protein expressed in humans selectively in skeletal muscle. To determine the mechanisms by which UCP3 plays a role in regulating glucose metabolism, we expressed human UCP3 in L6 myotubes by adenovirus-mediated gene transfer and in H(9)C(2) cardiomyoblasts by stable transfection with a tetracycline-repressible UCP3 construct. Expression of UCP3 in L6 myotubes increased 2-deoxyglucose uptake 2-fold and cell surface GLUT4 2.3-fold, thereby reaching maximally insulin-stimulated levels in control myotubes. Wortmannin, LY 294002, or the tyrosine kinase inhibitor genistein abolished the effect of UCP3 on glucose uptake, and wortmannin inhibited UCP3-induced GLUT4 cell surface recruitment. UCP3 overexpression increased phosphotyrosine-associated phosphoinositide 3-kinase (PI3K) activity 2.2-fold compared with control cells (p < 0.05). UCP3 overexpression increased lactate release 1.5- to 2-fold above control cells, indicating increased glucose metabolism. In H(9)C(2) cardiomyoblasts stably transfected with UCP3 under control of a tetracycline-repressible promotor, removal of doxycycline resulted in detectable levels of UCP3 at 12 h and 2.2-fold induction at 7 days compared with 12 h. In parallel, glucose transport increased 1.3- and 2-fold at 12 h and 7 days, respectively, and the stimulation was inhibited by wortmannin or genistein. p85 association with membranes was increased 5.5-fold and phosphotyrosine-associated PI3K activity 3.8-fold. In contrast, overexpression of UCP3 in 3T3-L1 adipocytes did not alter glucose uptake, suggesting tissue-specific effects of human UCP3. Thus, UCP3 stimulates glucose transport and GLUT4 translocation to the cell surface in cardiac and skeletal muscle cells by activating a PI3K dependent pathway.
Diabetes Unit, Department of Medicine, Division of Endocrinology and Metabolism, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
C
C
Huppertz
B M
BM
Fischer
Y B
YB
Kim
K
K
Kotani
A
A
Vidal-Puig
L J
LJ
Slieker
K W
KW
Sloop
B B
BB
Lowell
B B
BB
Kahn
D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D003847:Deoxyglucose / Q000378:metabolism*; D004318:Doxycycline / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D007473:Ion Channels; D007773:Lactates / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D000071247:Uncoupling Protein 3; D000077191:Wortmannin
D000730:Androstadienes; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D007328:Insulin; D007473:Ion Channels; D007773:Lactates; D024101:Mitochondrial Proteins; D011994:Recombinant Proteins; C000604392:UCP3 protein, human; C000604393:Ucp3 protein, mouse; D000071247:Uncoupling Protein 3; D003847:Deoxyglucose; D019833:Genistein; D019869:Phosphatidylinositol 3-Kinases; D005947:Glucose; D004318:Doxycycline; D000077191:Wortmannin