Glut4 is targeted to specific vesicles in adipocytes of transgenic mice overexpressing Glut4 selectively in adipose tissue.
Adipocytes of transgenic mice overexpressing Glut4 selectively in adipose tissue (Shepherd, P.R., Gnudi, L., Tozzo, E., Yang, H., Leach, F., and Kahn, B.B. (1993) J. Biol. Chem. 268, 22243-22246) have 15-20-fold more Glut4 than normal adipocytes. To study compartmentalization of intracellular Glut4 in these cells, we fractionated light microsomes prepared from transgenic and normal adipocytes in velocity and density sucrose gradients. Glut4-containing intracellular membranes from both cell types have a specific and narrow distribution in these gradients, i.e. behave as homogeneous vesicles with identical sedimentation coefficients and different buoyant densities. Immunoadsorption of Glut4-containing vesicles with covalently immobilized monoclonal anti-transporter antibody demonstrated that the total polypeptide composition of these vesicles from transgenic and normal cells was identical, with the exception of Glut4 itself, which was much more abundant in the transgenic cells. Both preparations also had comparable levels of secretory carrier membrane proteins and of aminopeptidase activity (gp160). Glut4-containing vesicles from both normal and transgenic adipocytes excluded Glut1, which in both cell types formed a different vesicle population. Thus, even under conditions of high level overexpression, Glut4 is still specifically targeted to the same unique type of structurally defined insulin-sensitive vesicles as in normal cells.
Tozzo
E
E
Department of Medicine, Beth Israel Hospital, Harvard Medical School, Boston, Massachusetts 02215, USA.
Kahn
B B
BB
Pilch
P F
PF
Kandror
K V
KV
D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D051275:Glucose Transporter Type 4; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins
D017931:DNA Primers; D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495693:Slc2a4 protein, mouse