Targeting of GLUT6 (formerly GLUT9) and GLUT8 in rat adipose cells.
The subcellular targeting of the two recently cloned novel mammalian glucose transporters, GLUT6 [previously referred to as GLUT9 [Doege, Bocianski, Joost and Schürmann (2000) Biochem. J. 350, 771-776] and GLUT8, was analysed by expression of haemagglutinin (HA)-epitope-tagged GLUTs in transiently transfected primary rat adipose cells. Similar to HA-GLUT4, both transporters, HA-GLUT6 and HA-GLUT8, were retained in intracellular compartments in non-stimulated cells. In contrast, mutation of the N-terminal dileucine motifs in both constructs led to constitutive expression of the proteins on the plasma membrane. Likewise, when endocytosis was blocked by co-expression of a dominant-negative mutant of the dynamin GTPase, wild-type HA-GLUT6 and HA-GLUT8 accumulated on the cell surface. However, in contrast with HA-GLUT4, no translocation of HA-GLUT6 and HA-GLUT8 to the plasma membrane was observed when the cells were stimulated with insulin, phorbol ester or hyperosmolarity. Thus GLUT6 and GLUT8 appear to recycle in a dynamin-dependent manner between internal membranes and the plasma membrane in rat adipose cells, but are unresponsive to stimuli that induce translocation of GLUT4.
Lisinski
I
I
Center for Molecular Medicine, Institute of Biochemistry, University of Cologne, Otto-Fischer-Str. 12-14, 50674 Cologne, Germany.
Schürmann
A
A
Joost
H G
HG
Cushman
S W
SW
Al-Hasani
H
H
D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D034281:Dynamins; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism; D051246:Glucose Transport Proteins, Facilitative; D051275:Glucose Transporter Type 4; D006388:Hemagglutinins / Q000235:genetics; D007328:Insulin / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins; D009154:Mutation; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection
C498776:GLUT6 protein, rat; D051246:Glucose Transport Proteins, Facilitative; D051275:Glucose Transporter Type 4; D006388:Hemagglutinins; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D011993:Recombinant Fusion Proteins; C495694:Slc2a4 protein, rat; C498629:Slc2a8 protein, rat; D020558:GTP Phosphohydrolases; D034281:Dynamins