Synip phosphorylation is required for insulin-stimulated Glut4 translocation.
Previously we identified an unusual potential dual Akt/protein kinase B consensus phosphorylation motif in the protein Synip (RxKxRS(97)xS(99)) with serine 99 as a unique Akt2, but not Akt1 or for Akt3, substrate phosphorylation site. Although we have previously reported that serine 99 to phenylalanine (S99F-Synip) resulted in a constitutive inhibition of insulin-stimulated Glut4 translocation, a recent report indicated that Synip serine 99 to alanine mutant (S99A-Synip) failed to inhibit insulin-stimulated Glut4 translocation [H. Sano, S. Kane, E. Sano, G.E. Lienhard, Synip phosphorylation does not regulate insulin-stimulated GLUT4 translocation, Biochem. Biophys. Res. Commun. 332 (2005) 880-884]. To address this apparent discrepancy, we have now examined the S99A-Synip mutant and find that this mutant behaves essentially identical to S99F-Synip in that overexpression inhibits insulin-stimulated Glut4 translocation and is incapable of undergoing insulin-stimulated Syntaxin4 dissociation. These data are consistent with Synip serine 99 phosphorylation required for insulin-stimulated Glut4 translocation.
Okada
Shuichi
S
Department of Medicine and Molecular Science, Gunma University Graduate School of Medicine, 3-39-15, Showa-machi, Maebashi, Gunma 371-8511, Japan. okadash@showa.gunma-u.ac.jp
Ohshima
Kihachi
K
Uehara
Yutaka
Y
Shimizu
Hiroyuki
H
Hashimoto
Koshi
K
Yamada
Masanobu
M
Mori
Masatomo
M
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D015153:Blotting, Western; D004586:Electrophoresis; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D050765:Qa-SNARE Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*; D001616:beta-Galactosidase / Q000378:metabolism
D051275:Glucose Transporter Type 4; D007328:Insulin; D050765:Qa-SNARE Proteins; C495693:Slc2a4 protein, mouse; C120000:Stxbp4 protein, mouse; D033921:Vesicular Transport Proteins; D001616:beta-Galactosidase