Dissection of GLUT4 recycling pathway into exocytosis and endocytosis in rat adipocytes. Evidence that GTP-binding proteins are involved in both processes.
The effects of guanine nucleotides on either exocytosis or endocytosis of GLUT4 were examined in electrically permeabilized rat adipocytes by using Dk-(62-85), a major histocompatibility complex class I-derived peptide. Reversal of glucose transport activity that had been stimulated with insulin was completely blocked by Dk-(62-85). Likewise, endocytosis of the trypsin-cleaved 35-kDa fragment of GLUT4 was almost completely inhibited by the peptide. Insulin-stimulated glucose transport activity was enhanced about 50% by Dk-(62-85), whereas the basal transport activity was stimulated only slightly. Although guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) augmented glucose transport to the same extent as insulin in the absence of the peptide, glucose transport stimulated by GTP gamma S was only 60% of the insulin effect in the presence of the peptide; the effect of insulin was markedly enhanced by Dk-(62-85), whereas GTP gamma S-induced glucose transport was not affected, suggesting that GTP gamma S has an effect similar to that of the peptide. In fact, endocytosis of the 35-kDa fragment of GLUT4 was markedly inhibited by GTP gamma S. Additionally, GLUT4 endocytosis was accelerated by GTP but was inhibited by guanosine 5'-O-(2-thiodiphosphate). These results indicate that GTP gamma S induces translocation of GLUT4 by both stimulating exocytosis and inhibiting endocytosis. With respect to the dependence on GTP hydrolysis, distinct types of GTP-binding proteins are involved in exocytosis and endocytosis of GLUT4.
Shibata
H
H
Department of Cell Biology, Gunma University, Maebashi, Japan.
Suzuki
Y
Y
Omata
W
W
Tanaka
S
S
Kojima
I
I
D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D004705:Endocytosis / Q000187:drug effects; D005089:Exocytosis / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000378:metabolism*; D051275:Glucose Transporter Type 4; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006183:H-2 Antigens; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D013873:Thionucleotides / Q000494:pharmacology
D051275:Glucose Transporter Type 4; D006183:H-2 Antigens; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D010446:Peptide Fragments; C495694:Slc2a4 protein, rat; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C023427:guanosine 5'-O-(2-thiodiphosphate); D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins