Roles of insulin, guanosine 5'-[gamma-thio]triphosphate and phorbol 12-myristate 13-acetate in signalling pathways of GLUT4 translocation.
Insulin, guanosine 5'-[gamma-thio]triphosphate (GTP[S] and phorbol 12-myristate 13-acetate (PMA) trigger the translocation of Gl UT4 (type 4 glucose transporter; insulin-sensitive glucose transporter) from an intracellular pool to the cell surface. We have developed a highly sensitive and quantitative method to detect GLUT4 immunologically on the surface of intact 3T3-L1 adipocytes and Chinese hamster ovary (CHO) cells, using c-myc epitope-tagged GLUT4 (GLUT4myc). We examined the roles of insulin, GTP[S] and PMA in the signalling pathways of GLUT4 translocation in the CHO cell system. Among small molecular GTP-binding proteins, ras, rab3D, rad and rho seem to be candidates as signal transmitters of insulin-stimulated GLUT4 translocation. Overexpression of wild-type H-ras and the dominant negative mutant H-rass17N in our cell system respectively enhanced and blocked insulin-stimulated activation of mitogen-activated protein kinase, but did not affect insulin-stimulated GLUT4 translocation. Overexpression of rab3D or rad in the cells did not affect GLUT4 translocation triggered by insulin, GTP[S] or PMA. Treatment with Botulinum C3 exoenzyme, a specific inhibitor of rho, had no effect on GLUT4 translocation induced by insulin, GTP[S] or PMA. Therefore these small molecular GTP-binding proteins are not likely to be involved in GLUT4 translocation. In addition, insulin, GTP[S] and PMA apparently stimulate GLUT4 translocation through independent pathways.
Todaka
M
M
Department of Enzyme Genetics, University of Tokushima, Kuramoto-cho, Japan.
Hayashi
H
H
Imanaka
T
T
Mitani
Y
Y
Kamohara
S
S
Kishi
K
K
Tamaoka
K
K
Kanai
F
F
Shichiri
M
M
Morii
N
N
Narumiya
S
S
Ebina
Y
Y
D016475:3T3 Cells; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D016466:CHO Cells; D006224:Cricetinae; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D051275:Glucose Transporter Type 4; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D008954:Models, Biological; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495693:Slc2a4 protein, mouse; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate