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Insulin down-regulates the expression of ubiquitin E3 ligases partially by inhibiting the activity and expression of AMP-activated protein kinase in L6 myotubes

While insulin is an anabolic hormone, AMP-activated protein kinase (AMPK) is not only a key energy regulator, but it can also control substrate metabolism directly by inducing skeletal muscle protein degradation. The hypothesis of the present study was that insulin inhibits AMPK and thus down-regula...

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Autores principales: Deng, Hu-Ping, Chai, Jia-Ke, Shen, Chuan-An, Zhang, Xi-Bo, Ma, Li, Sun, Tian-Jun, Hu, Qing-Gang, Chi, Yun-Fei, Dong, Ning
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Portland Press Ltd. 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4613693/
https://www.ncbi.nlm.nih.gov/pubmed/26193886
http://dx.doi.org/10.1042/BSR20150017
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author Deng, Hu-Ping
Chai, Jia-Ke
Shen, Chuan-An
Zhang, Xi-Bo
Ma, Li
Sun, Tian-Jun
Hu, Qing-Gang
Chi, Yun-Fei
Dong, Ning
author_facet Deng, Hu-Ping
Chai, Jia-Ke
Shen, Chuan-An
Zhang, Xi-Bo
Ma, Li
Sun, Tian-Jun
Hu, Qing-Gang
Chi, Yun-Fei
Dong, Ning
author_sort Deng, Hu-Ping
collection PubMed
description While insulin is an anabolic hormone, AMP-activated protein kinase (AMPK) is not only a key energy regulator, but it can also control substrate metabolism directly by inducing skeletal muscle protein degradation. The hypothesis of the present study was that insulin inhibits AMPK and thus down-regulates the expression of the ubiquitin E3 ligases, muscle atrophy F-box (MAFbx) and muscle RING finger 1 (MuRF1) in skeletal muscle cells. Differentiated L6 myotubes were treated with 5-aminoimidazole-4-carboxamide-1-β-4-ribofuranoside (AICAR) and/or compound C to stimulate and/or block AMPK respectively. These treatments were also conducted in the presence or absence of insulin and the cells were analysed by western blot and quantitative real-time PCR. In addition, nuleotide levels were determined using HPLC. The activation of AMPK with AICAR enhanced the mRNA levels of MAFbx and MuRF1. Insulin reduced the phosphorylation and activity AMPK, which was accompanied by reduced MAFbx and MuRF1 mRNA levels. Using a protein kinase B (PKB/Akt) inhibitor, we found that insulin regulates AMPK through the activation of Akt. Furthermore, insulin down-regulated AMPK α2 mRNA. We conclude that insulin inhibits AMPK through Akt phosphorylation in L6 myotubes, which may serve as a possible signalling pathway for the down-regulation of protein degradation. In addition, decreased expression of AMPK α2 may partially participate in inhibiting the activity of AMPK.
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spelling pubmed-46136932015-11-02 Insulin down-regulates the expression of ubiquitin E3 ligases partially by inhibiting the activity and expression of AMP-activated protein kinase in L6 myotubes Deng, Hu-Ping Chai, Jia-Ke Shen, Chuan-An Zhang, Xi-Bo Ma, Li Sun, Tian-Jun Hu, Qing-Gang Chi, Yun-Fei Dong, Ning Biosci Rep Original Papers While insulin is an anabolic hormone, AMP-activated protein kinase (AMPK) is not only a key energy regulator, but it can also control substrate metabolism directly by inducing skeletal muscle protein degradation. The hypothesis of the present study was that insulin inhibits AMPK and thus down-regulates the expression of the ubiquitin E3 ligases, muscle atrophy F-box (MAFbx) and muscle RING finger 1 (MuRF1) in skeletal muscle cells. Differentiated L6 myotubes were treated with 5-aminoimidazole-4-carboxamide-1-β-4-ribofuranoside (AICAR) and/or compound C to stimulate and/or block AMPK respectively. These treatments were also conducted in the presence or absence of insulin and the cells were analysed by western blot and quantitative real-time PCR. In addition, nuleotide levels were determined using HPLC. The activation of AMPK with AICAR enhanced the mRNA levels of MAFbx and MuRF1. Insulin reduced the phosphorylation and activity AMPK, which was accompanied by reduced MAFbx and MuRF1 mRNA levels. Using a protein kinase B (PKB/Akt) inhibitor, we found that insulin regulates AMPK through the activation of Akt. Furthermore, insulin down-regulated AMPK α2 mRNA. We conclude that insulin inhibits AMPK through Akt phosphorylation in L6 myotubes, which may serve as a possible signalling pathway for the down-regulation of protein degradation. In addition, decreased expression of AMPK α2 may partially participate in inhibiting the activity of AMPK. Portland Press Ltd. 2015-08-20 /pmc/articles/PMC4613693/ /pubmed/26193886 http://dx.doi.org/10.1042/BSR20150017 Text en © 2015 Authors http://creativecommons.org/licenses/by/3.0/ This is an open access article published by Portland Press Limited and distributed under the Creative Commons Attribution Licence 3.0 (http://creativecommons.org/licenses/by/3.0/) .
spellingShingle Original Papers
Deng, Hu-Ping
Chai, Jia-Ke
Shen, Chuan-An
Zhang, Xi-Bo
Ma, Li
Sun, Tian-Jun
Hu, Qing-Gang
Chi, Yun-Fei
Dong, Ning
Insulin down-regulates the expression of ubiquitin E3 ligases partially by inhibiting the activity and expression of AMP-activated protein kinase in L6 myotubes
title Insulin down-regulates the expression of ubiquitin E3 ligases partially by inhibiting the activity and expression of AMP-activated protein kinase in L6 myotubes
title_full Insulin down-regulates the expression of ubiquitin E3 ligases partially by inhibiting the activity and expression of AMP-activated protein kinase in L6 myotubes
title_fullStr Insulin down-regulates the expression of ubiquitin E3 ligases partially by inhibiting the activity and expression of AMP-activated protein kinase in L6 myotubes
title_full_unstemmed Insulin down-regulates the expression of ubiquitin E3 ligases partially by inhibiting the activity and expression of AMP-activated protein kinase in L6 myotubes
title_short Insulin down-regulates the expression of ubiquitin E3 ligases partially by inhibiting the activity and expression of AMP-activated protein kinase in L6 myotubes
title_sort insulin down-regulates the expression of ubiquitin e3 ligases partially by inhibiting the activity and expression of amp-activated protein kinase in l6 myotubes
topic Original Papers
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4613693/
https://www.ncbi.nlm.nih.gov/pubmed/26193886
http://dx.doi.org/10.1042/BSR20150017
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