PMID- 26669439 OWN - NLM STAT- MEDLINE DCOM- 20160811 LR - 20220318 IS - 1091-6490 (Electronic) IS - 0027-8424 (Print) IS - 0027-8424 (Linking) VI - 112 IP - 52 DP - 2015 Dec 29 TI - mTOR inhibition activates overall protein degradation by the ubiquitin proteasome system as well as by autophagy. PG - 15790-7 LID - 10.1073/pnas.1521919112 [doi] AB - Growth factors and nutrients enhance protein synthesis and suppress overall protein degradation by activating the protein kinase mammalian target of rapamycin (mTOR). Conversely, nutrient or serum deprivation inhibits mTOR and stimulates protein breakdown by inducing autophagy, which provides the starved cells with amino acids for protein synthesis and energy production. However, it is unclear whether proteolysis by the ubiquitin proteasome system (UPS), which catalyzes most protein degradation in mammalian cells, also increases when mTOR activity decreases. Here we show that inhibiting mTOR with rapamycin or Torin1 rapidly increases the degradation of long-lived cell proteins, but not short-lived ones, by stimulating proteolysis by proteasomes, in addition to autophagy. This enhanced proteasomal degradation required protein ubiquitination, and within 30 min after mTOR inhibition, the cellular content of K48-linked ubiquitinated proteins increased without any change in proteasome content or activity. This rapid increase in UPS-mediated proteolysis continued for many hours and resulted primarily from inhibition of mTORC1 (not mTORC2), but did not require new protein synthesis or key mTOR targets: S6Ks, 4E-BPs, or Ulks. These findings do not support the recent report that mTORC1 inhibition reduces proteolysis by suppressing proteasome expression [Zhang Y, et al. (2014) Nature 513(7518):440-443]. Several growth-related proteins were identified that were ubiquitinated and degraded more rapidly after mTOR inhibition, including HMG-CoA synthase, whose enhanced degradation probably limits cholesterol biosynthesis upon insulin deficiency. Thus, mTOR inhibition coordinately activates the UPS and autophagy, which provide essential amino acids and, together with the enhanced ubiquitination of anabolic proteins, help slow growth. FAU - Zhao, Jinghui AU - Zhao J AD - Department of Cell Biology, Harvard Medical School, Boston, MA 02115. FAU - Zhai, Bo AU - Zhai B AD - Department of Cell Biology, Harvard Medical School, Boston, MA 02115. FAU - Gygi, Steven P AU - Gygi SP AD - Department of Cell Biology, Harvard Medical School, Boston, MA 02115. FAU - Goldberg, Alfred Lewis AU - Goldberg AL AD - Department of Cell Biology, Harvard Medical School, Boston, MA 02115 Alfred_Goldberg@hms.harvard.edu. LA - eng GR - R01 AR055255/AR/NIAMS NIH HHS/United States GR - R01 GM051923/GM/NIGMS NIH HHS/United States GR - 5R01AR055255/AR/NIAMS NIH HHS/United States GR - R01 GM067945/GM/NIGMS NIH HHS/United States GR - 5R01GM051923/GM/NIGMS NIH HHS/United States PT - Journal Article PT - Research Support, N.I.H., Extramural PT - Research Support, Non-U.S. Gov't DEP - 20151215 PL - United States TA - Proc Natl Acad Sci U S A JT - Proceedings of the National Academy of Sciences of the United States of America JID - 7505876 RN - 0 (1-(4-(4-propionylpiperazin-1-yl)-3-(trifluoromethyl)phenyl)-9-(quinolin-3-yl)benzo(h)(1,6)naphthyridin-2(1H)-one) RN - 0 (Immunosuppressive Agents) RN - 0 (Naphthyridines) RN - 0 (Ubiquitin) RN - EC 2.3.3.10 (Hydroxymethylglutaryl-CoA Synthase) RN - EC 2.7.1.1 (MTOR protein, human) RN - EC 2.7.11.1 (TOR Serine-Threonine Kinases) RN - EC 3.4.25.1 (Proteasome Endopeptidase Complex) RN - W36ZG6FT64 (Sirolimus) SB - IM CIN - doi: 10.1073/pnas.1522332112 MH - Animals MH - *Autophagy MH - Blotting, Western MH - Cells, Cultured MH - HEK293 Cells MH - Humans MH - Hydroxymethylglutaryl-CoA Synthase/metabolism MH - Immunosuppressive Agents/pharmacology MH - Naphthyridines/pharmacology MH - Proteasome Endopeptidase Complex/*metabolism MH - Proteolysis/drug effects MH - Sirolimus/pharmacology MH - TOR Serine-Threonine Kinases/*antagonists & inhibitors/metabolism MH - Time Factors MH - Ubiquitin/*metabolism MH - Ubiquitination/drug effects PMC - PMC4703015 OTO - NOTNLM OT - autophagy OT - mTOR OT - proteasome OT - ubiquitination COIS- The authors declare no conflict of interest. EDAT- 2015/12/17 06:00 MHDA- 2016/08/12 06:00 PMCR- 2016/06/29 CRDT- 2015/12/17 06:00 PHST- 2015/12/17 06:00 [entrez] PHST- 2015/12/17 06:00 [pubmed] PHST- 2016/08/12 06:00 [medline] PHST- 2016/06/29 00:00 [pmc-release] AID - 1521919112 [pii] AID - 201521919 [pii] AID - 10.1073/pnas.1521919112 [doi] PST - ppublish SO - Proc Natl Acad Sci U S A. 2015 Dec 29;112(52):15790-7. doi: 10.1073/pnas.1521919112. Epub 2015 Dec 15.