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Rag GTPases and AMPK/TSC2/Rheb mediate the differential regulation of mTORC1 signaling in response to alcohol and leucine

Rag GTPases and AMPK/TSC2/Rheb mediate the differential regulation of mTORC1 signaling in... Leucine (Leu) and insulin both stimulate muscle protein synthesis, albeit at least in part via separate signaling pathways. While alcohol (EtOH) suppresses insulin-stimulated protein synthesis in cultured myocytes, its ability to disrupt Leu signaling and Rag GTPase activity has not been determined. Likewise, little is known regarding the interaction of EtOH and Leu on the AMPK/TSC2/Rheb pathway. Treatment of myocytes with EtOH (100 mM) decreased protein synthesis, whereas Leu (2 mM) increased synthesis. In combination, EtOH suppressed the anabolic effect of Leu. The effects of EtOH and Leu were associated with coordinate changes in the phosphorylation state of mTOR, raptor, and their downstream targets 4EBP1 and S6K1. As such, EtOH suppressed the ability of Leu to activate these signaling components. The Rag signaling pathway was activated by Leu but suppressed by EtOH, as evidenced by changes in the interaction of Rag proteins with mTOR and raptor. Overexpression of constitutively active (ca)RagA and caRagC increased mTORC1 activity, as determined by increased S6K1 phosphorylation. Furthermore, the caRagA-caRagC heterodimer blocked the inhibitory effect of EtOH. EtOH and Leu produced differential effects on AMPK signaling. EtOH enhanced AMPK activity, resulting in increased TSC2 (S1387) and eEF2 phosphorylation, whereas Leu had the opposite effect. EtOH also decreased the interaction of Rheb with mTOR, and this was prevented by Leu. Collectively, our results indicate that EtOH inhibits the anabolic effects that Leu has on protein synthesis and mTORC1 activity by modulating both Rag GTPase function and AMPK/TSC2/Rheb signaling. AMP-activated protein kinase tuberous sclerosis protein complex 2 mammalian target of rapamycin complex 1 protein synthesis Rag proteins Ras homolog enriched in brain Copyright © 2012 the American Physiological Society « Previous | Next Article » Table of Contents This Article Published online before print March 21, 2012 , doi: 10.​1152/​ajpcell.​00407.​2011 Am J Physiol Cell Physiol May 15, 2012 vol. 302 no. 10 C1557-C1565 » Abstract Free Full Text Free to you Full Text (PDF) Free to you All Versions of this Article: ajpcell.00407.2011v1 302/10/C1557 most recent Classifications Article Services Email this article to a friend Alert me when this article is cited Alert me if a correction is posted Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Download to citation manager Citing Articles Load citing article information Citing articles via Web of Science Google Scholar Articles by Hong-Brown, L. Q. Articles by Lang, C. H. PubMed PubMed citation Articles by Hong-Brown, L. Q. Articles by Lang, C. H. Related Content Load related web page information Current Content Alert me to new issues of Am J Physiol Cell Physiol About the Journal Information for Authors Submit a Manuscript Ethical Policies AuthorChoice PubMed Central Policy Reprints and Permissions Advertising Press Copyright © 2012 the American Physiological Society Print ISSN: 0363-6143 Online ISSN: 1522-1563 var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); try { var pageTracker = _gat._getTracker("UA-2924550-1"); pageTracker._trackPageview(); } catch(err) {} var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); try { var pageTracker = _gat._getTracker("UA-189672-30"); pageTracker._setDomainName(".physiology.org"); pageTracker._trackPageview(); } catch(err) {} http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Cell Physiology The American Physiological Society

Rag GTPases and AMPK/TSC2/Rheb mediate the differential regulation of mTORC1 signaling in response to alcohol and leucine

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References (60)

Publisher
The American Physiological Society
Copyright
Copyright © 2012 the American Physiological Society
ISSN
0363-6143
eISSN
1522-1563
DOI
10.1152/ajpcell.00407.2011
pmid
22442136
Publisher site
See Article on Publisher Site

Abstract

Leucine (Leu) and insulin both stimulate muscle protein synthesis, albeit at least in part via separate signaling pathways. While alcohol (EtOH) suppresses insulin-stimulated protein synthesis in cultured myocytes, its ability to disrupt Leu signaling and Rag GTPase activity has not been determined. Likewise, little is known regarding the interaction of EtOH and Leu on the AMPK/TSC2/Rheb pathway. Treatment of myocytes with EtOH (100 mM) decreased protein synthesis, whereas Leu (2 mM) increased synthesis. In combination, EtOH suppressed the anabolic effect of Leu. The effects of EtOH and Leu were associated with coordinate changes in the phosphorylation state of mTOR, raptor, and their downstream targets 4EBP1 and S6K1. As such, EtOH suppressed the ability of Leu to activate these signaling components. The Rag signaling pathway was activated by Leu but suppressed by EtOH, as evidenced by changes in the interaction of Rag proteins with mTOR and raptor. Overexpression of constitutively active (ca)RagA and caRagC increased mTORC1 activity, as determined by increased S6K1 phosphorylation. Furthermore, the caRagA-caRagC heterodimer blocked the inhibitory effect of EtOH. EtOH and Leu produced differential effects on AMPK signaling. EtOH enhanced AMPK activity, resulting in increased TSC2 (S1387) and eEF2 phosphorylation, whereas Leu had the opposite effect. EtOH also decreased the interaction of Rheb with mTOR, and this was prevented by Leu. Collectively, our results indicate that EtOH inhibits the anabolic effects that Leu has on protein synthesis and mTORC1 activity by modulating both Rag GTPase function and AMPK/TSC2/Rheb signaling. AMP-activated protein kinase tuberous sclerosis protein complex 2 mammalian target of rapamycin complex 1 protein synthesis Rag proteins Ras homolog enriched in brain Copyright © 2012 the American Physiological Society « Previous | Next Article » Table of Contents This Article Published online before print March 21, 2012 , doi: 10.​1152/​ajpcell.​00407.​2011 Am J Physiol Cell Physiol May 15, 2012 vol. 302 no. 10 C1557-C1565 » Abstract Free Full Text Free to you Full Text (PDF) Free to you All Versions of this Article: ajpcell.00407.2011v1 302/10/C1557 most recent Classifications Article Services Email this article to a friend Alert me when this article is cited Alert me if a correction is posted Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Download to citation manager Citing Articles Load citing article information Citing articles via Web of Science Google Scholar Articles by Hong-Brown, L. Q. Articles by Lang, C. H. PubMed PubMed citation Articles by Hong-Brown, L. Q. Articles by Lang, C. H. Related Content Load related web page information Current Content Alert me to new issues of Am J Physiol Cell Physiol About the Journal Information for Authors Submit a Manuscript Ethical Policies AuthorChoice PubMed Central Policy Reprints and Permissions Advertising Press Copyright © 2012 the American Physiological Society Print ISSN: 0363-6143 Online ISSN: 1522-1563 var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); try { var pageTracker = _gat._getTracker("UA-2924550-1"); pageTracker._trackPageview(); } catch(err) {} var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); try { var pageTracker = _gat._getTracker("UA-189672-30"); pageTracker._setDomainName(".physiology.org"); pageTracker._trackPageview(); } catch(err) {}

Journal

AJP - Cell PhysiologyThe American Physiological Society

Published: May 15, 2012

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