Insulin regulation of the two glucose transporters in 3T3-L1 adipocytes.
The amounts of the brain type and muscle type glucose transporters (designated Glut 1 and 4, respectively) in 3T3-L1 adipocytes have been determined by quantitative immunoblotting with antibodies against their carboxyl-terminal peptides. There are about 950,000 and 280,000 copies of Glut 1 and 4, respectively, per cell. Insulin caused the translocation of both types of transporters from an intracellular location to the plasma membrane. The insulin-elicited increase in cell surface transporters was assessed by labeling the surface transporters with a newly developed, membrane-impermeant, photoaffinity labeling reagent for glucose transporters. The increases in Glut 1 and 4 averaged 6.5- and 17-fold, respectively, whereas there was a 21-fold in hexose transport. These results indicate that the translocation of Glut 4 could largely account for the insulin effect on transport rate, but only if the intrinsic activity of Glut 4 is much higher than that of Glut 1. The two transporters are colocalized intracellularly: vesicles (average diameter 72 nm) isolated from the intracellular membranes by immunoadsorption with antibodies against Glut 1 contained 95% of the Glut 4 and, conversely, vesicles isolated with antibodies against Glut 4 contained 85% of the Glut 1.
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03756.
D M
DM
Calderhead
K
K
Kitagawa
L I
LI
Tanner
G D
GD
Holman
G E
GE
Lienhard
D000273:Adipose Tissue / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000345:Affinity Labels / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000378:metabolism / Q000648:ultrastructure; D003837:Deoxy Sugars / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008854:Microscopy, Electron; D008970:Molecular Weight; D009004:Monosaccharide Transport Proteins / Q000302:isolation & purification / Q000378:metabolism*
D000345:Affinity Labels; D003837:Deoxy Sugars; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D003847:Deoxyglucose