Insulin-regulated sorting of glucose transporters in 3T3-L1 adipocytes.
Two glucose transporters (GLUT-4 and GLUT-1) move from within the cell to the plasma membrane (PM) when 3T3-L1 adipocytes are stimulated with insulin. To study the sorting of these two molecules, vesicles containing GLUT-4 and GLUT-1 were immunoadsorbed from basal and insulin-treated cells. Two different vesicle populations were isolated as follows: 1) a compartment that contained the majority of intracellular GLUT-4 and GLUT-1 and 2) a subpopulation of vesicles containing 43% of the intracellular GLUT-4 that was highly insulin regulatable and that contained relatively low levels of GLUT-1. After incubation at 19 degrees C, basal glucose transport was slightly increased, whereas insulin-dependent transport was blocked. Consistent with these observations, cell surface GLUT-1 levels were increased in the basal state, whereas insulin-dependent translocation of GLUT-4 to the PM was blocked at 19 degrees C. However, insulin-dependent sorting of GLUT-4 within the intracellular compartment was still evident at 19 degrees C. These data indicate that GLUT-1 and GLUT-4 are heterogeneously distributed throughout the same intracellular compartment in 3T3-L1 adipocytes. Furthermore, we have uncoupled two distinct steps in the insulin-dependent movement of GLUT-4 to the cell surface. These include movement of GLUT-4 out of its storage compartment and accumulation of GLUT-4 at the cell surface. Only the former step occurs in cells preincubated at 19 degrees C.
Robinson
L J
LJ
Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110.
James
D E
DE
D016475:3T3 Cells; D000273:Adipose Tissue / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D003847:Deoxyglucose / Q000493:pharmacokinetics; D004705:Endocytosis; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D007163:Immunosorbent Techniques; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000145:classification / Q000378:metabolism*; D009124:Muscle Proteins; D013347:Subcellular Fractions / Q000378:metabolism; D013696:Temperature; D014018:Tissue Distribution
D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495678:Slc2a1 protein, mouse; C495693:Slc2a4 protein, mouse; D003847:Deoxyglucose