Uncoupling Protein 3 (UCP3) Stimulates Glucose Uptake in Muscle Cells through a Phosphoinositide 3-Kinase-dependent Mechanism

• Published in: The Journal of biological chemistry 2001-04, Vol.276 (16), p.12520-12529
• Main Authors: Huppertz, C, Fischer, B M, Kim, Y B, Kotani, K, Vidal-Puig, A, Slieker, L J, Sloop, K W, Lowell, B B, Kahn, B B
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Adenovirus; Adipocytes - cytology; Adipocytes - metabolism; Androstadienes - pharmacology; Animals; Biological Transport; Carrier Proteins - metabolism; Cell Line; Cell Membrane - metabolism; Cell Survival - drug effects; Deoxyglucose - metabolism; doxycycline; Doxycycline - pharmacology; Enzyme Inhibitors - pharmacology; genistein; Genistein - pharmacology; Glucose - metabolism; glucose transporter GLUT4; Humans; Insulin - pharmacology; Ion Channels; Lactates - metabolism; Mice; Mitochondria - metabolism; Mitochondrial Proteins; Muscle, Skeletal - cytology; Muscle, Skeletal - metabolism; Myocardium - metabolism; Phosphatidylinositol 3-Kinases - metabolism; Phosphoinositide 3-kinase; Recombinant Proteins - metabolism; tetracycline; Transfection; UCP3 gene; Uncoupling Protein 3; Wortmannin
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M011708200

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.