title: Stable isotope-labelling analysis of the impact of inhibition of the mammalian target of rapamycin on protein synthesis.
abstract: mTORC1 [mTOR (mammalian target of rapamycin) complex 1] regulates diverse cell functions. mTORC1 controls the phosphorylation of several proteins involved in mRNA translation and the translation of specific mRNAs, including those containing a 5'-TOP (5'-terminal oligopyrimidine). To date, most of the proteins encoded by known 5'-TOP mRNAs are proteins involved in mRNA translation, such as ribosomal proteins and elongation factors. Rapamycin inhibits some mTORC1 functions, whereas mTOR-KIs (mTOR kinase inhibitors) interfere with all of them. mTOR-KIs inhibit overall protein synthesis more strongly than rapamycin. To study the effects of rapamycin or mTOR-KIs on synthesis of specific proteins, we applied pSILAC [pulsed SILAC (stable isotope-labelling with amino acids in cell culture)]. Our results reveal, first, that mTOR-KIs and rapamycin differentially affect the synthesis of many proteins. Secondly, mTOR-KIs inhibit the synthesis of proteins encoded by 5'-TOP mRNAs much more strongly than rapamycin does, revealing that these mRNAs are controlled by rapamycin-insensitive outputs from mTOR. Thirdly, the synthesis of certain other proteins shows a similar pattern of inhibition. Some of them appear to be encoded by 'novel' 5'-TOP mRNAs; they include proteins which, like known 5'-TOP mRNA-encoded proteins, are involved in protein synthesis, whereas others are enzymes involved in intermediary or anabolic metabolism. These results indicate that mTOR signalling may promote diverse biosynthetic processes through the translational up-regulation of specific mRNAs. Lastly, a SILAC-based approach revealed that, although rapamycin and mTOR-KIs have little effect on general protein stability, they stabilize proteins encoded by 5'-TOP mRNAs.
authors.affiliation: Centre for Biological Sciences, University of Southampton, UK.
authors.forename: Yilin
authors.initials: Y
authors.lastname: Huo
authors.forename: Valentina
authors.initials: V
authors.lastname: Iadevaia
authors.forename: Zhong
authors.initials: Z
authors.lastname: Yao
authors.forename: Isabelle
authors.initials: I
authors.lastname: Kelly
authors.forename: Sabina
authors.initials: S
authors.lastname: Cosulich
authors.forename: Sylvie
authors.initials: S
authors.lastname: Guichard
authors.forename: Leonard J
authors.initials: LJ
authors.lastname: Foster
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Proud
mesh_terms: D002247:Carbon Isotopes; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007553:Isotope Labeling; D009025:Morpholines / Q000494:pharmacology; D009587:Nitrogen Isotopes; D014176:Protein Biosynthesis / Q000187:drug effects* / Q000235:genetics; D011687:Purines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors*
chemical_list: D002247:Carbon Isotopes; D039561:Eukaryotic Initiation Factor-4E; D007211:Indoles; D009025:Morpholines; D009587:Nitrogen Isotopes; D011687:Purines; D012333:RNA, Messenger; C546624:(5-(2,4-bis((3S)-3-methylmorpholin-4-yl)pyrido(2,3-d)pyrimidin-7-yl)-2-methoxyphenyl)methanol; D058570:TOR Serine-Threonine Kinases; C572919:PP242; D020123:Sirolimus