Synip phosphorylation is required for insulin-stimulated Glut4 translocation.

Shuichi Okada, Kihachi Ohshima, Yutaka Uehara, Hiroyuki Shimizu, Koshi Hashimoto, Masanobu Yamada, Masatomo Mori

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

Biochemical and biophysical research communications 2007 Apr 27

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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.

Citation

Shuichi Okada, Kihachi Ohshima, Yutaka Uehara, Hiroyuki Shimizu, Koshi Hashimoto, Masanobu Yamada, Masatomo Mori. Synip phosphorylation is required for insulin-stimulated Glut4 translocation. Biochemical and biophysical research communications. 2007 Apr 27;356(1):102-6