The amino terminus of insulin-responsive aminopeptidase causes Glut4 translocation in 3T3-L1 adipocytes.
The insulin-responsive aminopeptidase (IRAP) is a constituent of the vesicles that contain the insulin-regulated glucose transporter (Glut4). Like Glut4, IRAP translocates to the cell surface in response to insulin. Microinjection into 3T3-L1 adipocytes of a glutathione S-transferase (GST) fusion protein containing the cytosolic portion of IRAP (GST-IRAP-(1-109)), resulted in translocation of Glut4 to the cell surface. Immunostaining of 3T3-L1 adipocytes for Glut4 showed that the percentage of cells with substantial cell surface Glut4 was 10% in unstimulated cells, 8% following injection of GST, and 27% following injection of GST-IRAP-(1-109). Increased cell surface Glut4 occurred within 5-10 min following injection and was maintained for at least 4 h. A fusion protein containing only 28 amino acids from IRAP (GST-IRAP-(55-82)) was as effective in increasing cell surface Glut4 as stimulation with 100 nM insulin (44% versus 43%, respectively). In contrast to insulin-stimulated Glut4 translocation, the redistribution of Glut4 following injection of GST-IRAP-(55-82) was not blocked by wortmannin or co-injection with a SH2 domain from the regulatory subunit of phosphatidylinositol 3-kinase. These data suggest that the amino terminus of IRAP interacts with a retention/sorting protein that also regulates the distribution of Glut4 in insulin-responsive cells.
Waters
S B
SB
Metabolex, Inc., Hayward, California 94545, USA.
D'Auria
M
M
Martin
S S
SS
Nguyen
C
C
Kozma
L M
LM
Luskey
K L
KL
D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000626:Aminopeptidases / Q000235:genetics / Q000494:pharmacology*; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D010446:Peptide Fragments / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D000077191:Wortmannin
D000730:Androstadienes; D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C495693:Slc2a4 protein, mouse; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D000626:Aminopeptidases; D000077191:Wortmannin