ADP-ribosylation factor 6 delineates separate pathways used by endothelin 1 and insulin for stimulating glucose uptake in 3T3-L1 adipocytes.
In 3T3-L1 adipocytes, both insulin and endothelin 1 stimulate glucose transport via translocation of the GLUT4 glucose carrier from an intracellular compartment to the cell surface. Yet it remains uncertain as to whether both hormones utilize identical pathways and to what extent each depends on the heterotrimeric G protein Galphaq as an intermediary signaling molecule. In this study, we used a novel inducible system to rapidly and synchronously activate expression of a dominant inhibitory form of ADP-ribosylation factor 6, ARF6(T27N), in 3T3-L1 adipocytes and assessed its effects on insulin- and endothelin-stimulated hexose uptake. Expression of ARF6(T27N) in 3T3-L1 adipocytes was without effect on the ability of insulin to stimulate either 2-deoxyglucose uptake or the translocation of GLUT4 or GLUT1 to the plasma membrane. However, the same ARF6 inhibitory mutant blocked the stimulation of hexose uptake and GLUT4 translocation in response to either endothelin 1 or an activated form of Galphaq, Galphaq(Q209L). These results suggest that endothelin stimulates glucose transport through a pathway that is distinct from that utilized by insulin but is likely to depend on both a heterotrimeric G protein from the Gq family and the small G protein ARF6. These data are consistent with the interpretation that endothelin and insulin stimulate functionally different pools of glucose transporters to be redistributed to the plasma membrane.
Lawrence
J T
JT
Department of Medicine, Howard Hughes Medical Institute, The Cox Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
Birnbaum
M J
MJ
D016475:3T3 Cells; D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D000256:Adenoviridae / Q000235:genetics; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D015152:Blotting, Northern; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D019332:Endothelin-1 / Q000378:metabolism*; D016232:Endothelins / Q000378:metabolism; D004789:Enzyme Activation; D005799:Genes, Dominant; D005947:Glucose / Q000493:pharmacokinetics*; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000378:metabolism*; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D009124:Muscle Proteins; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D021381:Protein Transport; D012190:Retroviridae / Q000378:metabolism
D000089982:ADP-Ribosylation Factor 6; D019332:Endothelin-1; D016232:Endothelins; 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; D020727:ADP-Ribosylation Factors; C000715727:Arf6 protein, mouse; D005947:Glucose