TY - JOUR
T1 - Tomosyn is a novel Akt substrate mediating insulin-dependent GLUT4 exocytosis
AU - Nagano, Koki
AU - Takeuchi, Hiroshi
AU - Gao, Jing
AU - Mori, Yoshihide
AU - Otani, Takahito
AU - Wang, Daguang
AU - Hirata, Masato
N1 - Funding Information:
This work was supported by JSPS KAKENHI (Grant Nos. 24592805 to HT, 25861758 to JG and 24229009 to MH), The Ichiro Kanehara Foundation for the Promotion of Medical Sciences and Medical Care and Takeda Science Foundation to HT. DW is a foreign graduate student supported by the Hirose International Scholarship. We appreciate the Research Support Center, Graduate School of Medical Sciences, Kyushu University for technical support. We thank Profs. Tom Martin (University of Wisconsin at Madison) and Sun Sik Bae (Pusan National University, Korea) for providing us with SNARE constructs and human GLUT4 cDNA containing a HA epitope tag in the first exofacial loop, respectively.
Publisher Copyright:
© 2015 Elsevier Ltd.
PY - 2015/5/1
Y1 - 2015/5/1
N2 - Insulin triggers glucose uptake into skeletal muscle and adipose tissues by gaining the available number of glucose transporter 4 (GLUT4) on the cell surface. GLUT4-loaded vesicles are targeted to plasma membrane from the intracellular reservoir through multiple trafficking and fusion processes that are mainly regulated by Akt. However, it is still largely unknown how GLUT4 expression in the cell surface is promoted by insulin. In the present study, we identified tomosyn at Ser-783 as a possible Akt-substrate motif and examined whether the phosphorylation at Ser-783 is involved in the regulation of GLUT4 expression. Both Akt1 and Akt2 phosphorylated the wild-type tomosyn, but not the mutant tomosyn in which Ser-783 was replaced with Ala. Phosphorylation of tomosyn at Ser-783 was also observed in the intact cells by insulin stimulation, which was blocked by PI3K inhibitor, LY294002. In vitro pull-down assay showed that phosphorylation of tomosyn at Ser-783 by Akt inhibited the interaction with syntaxin 4. Insulin stimulation increased GLUT4 in the cell surface of CHO-K1 cells to promote glucose uptake, however exogenous expression of the mutant tomosyn attenuated the increase by insulin. These results suggest that Ser-783 of tomosyn is a target of Akt and is implicated in the interaction with syntaxin 4.
AB - Insulin triggers glucose uptake into skeletal muscle and adipose tissues by gaining the available number of glucose transporter 4 (GLUT4) on the cell surface. GLUT4-loaded vesicles are targeted to plasma membrane from the intracellular reservoir through multiple trafficking and fusion processes that are mainly regulated by Akt. However, it is still largely unknown how GLUT4 expression in the cell surface is promoted by insulin. In the present study, we identified tomosyn at Ser-783 as a possible Akt-substrate motif and examined whether the phosphorylation at Ser-783 is involved in the regulation of GLUT4 expression. Both Akt1 and Akt2 phosphorylated the wild-type tomosyn, but not the mutant tomosyn in which Ser-783 was replaced with Ala. Phosphorylation of tomosyn at Ser-783 was also observed in the intact cells by insulin stimulation, which was blocked by PI3K inhibitor, LY294002. In vitro pull-down assay showed that phosphorylation of tomosyn at Ser-783 by Akt inhibited the interaction with syntaxin 4. Insulin stimulation increased GLUT4 in the cell surface of CHO-K1 cells to promote glucose uptake, however exogenous expression of the mutant tomosyn attenuated the increase by insulin. These results suggest that Ser-783 of tomosyn is a target of Akt and is implicated in the interaction with syntaxin 4.
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U2 - 10.1016/j.biocel.2015.02.013
DO - 10.1016/j.biocel.2015.02.013
M3 - Article
C2 - 25725259
AN - SCOPUS:84926489903
VL - 62
SP - 62
EP - 71
JO - International Journal of Biochemistry
JF - International Journal of Biochemistry
SN - 1357-2725
ER -