Improved insulin sensitivity by rapamycin is associated with reduction of mTOR and S6K1 activities in L6 myotubes

Title
Improved insulin sensitivity by rapamycin is associated with reduction of mTOR and S6K1 activities in L6 myotubes
Author(s)
장현욱황승락이선[이선]이재열[이재열]
Keywords
UNFOLDED PROTEIN RESPONSE; ENDOPLASMIC-RETICULUM; TRANSLATIONAL CONTROL; SIGNALING PATHWAYS; SKELETAL-MUSCLE; ER STRESS; RESISTANCE; KINASE; ACTIVATION; OBESITY
Issue Date
201202
Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
Citation
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, v.418, no.2, pp.402 - 407
Abstract
This study was designed to evaluate the role of mammalian target of rapamycin (mTOR)/p70S61 kinase (S6K1) pathways in ER stress-induced insulin resistance in L6 myotubes. Pretreatment with 5 mu g/ml of tunicamycin or 600 nM thapsigargin for 3 h decreased insulin-mediated tyrosine phosphorylation of IRS-1 and glucose uptake, and increased the level of mTOR/S6K1 phosphorylation in L6 myotubes. However, the inhibition of mTOR activity by rapamycin (inhibitor of several intracellular pathways including S6K1 pathways) reversed the ER stress-reduced tyrosine phosphorylation of IRS-1 and glucose uptake. Furthermore, pretreatment of cells with rapamycin decreased ER stress-induced phosphorylation of mTOR and S6K1. Interestingly, inhibition of mTOR by rapamycin did not affect ER stress markers such as PERK and JNK activity under the ER stress condition. Similar results were obtained with or without pretreatment with tunicamycin in the absence or presence of S6K1 RNAi. Moreover, S6K1 RNAi-mediated knockdown preserved insulin-stimulated Akt phosphorylation and glucose uptake in ER-stressed L6 myotubes, which was blocked by the phosphatidylinositol 3-kinase inhibitor wortmannin. Taken together, these results suggest that rapamycin improved ER stress-induced insulin resistance via inhibition of mTOR/S6K1 hyperphosphorylation in L6 myotubes. Crown Copyright (C) 2012 Published by Elsevier Inc. All rights reserved.
URI
http://hdl.handle.net/YU.REPOSITORY/29935http://dx.doi.org/10.1016/j.bbrc.2012.01.038
ISSN
0006-291X
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약학대학 > 약학부 > Articles
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