title: Tuberous sclerosis complex proteins 1 and 2 control serum-dependent translation in a TOP-dependent and -independent manner.
abstract: The tuberous sclerosis complex (TSC) proteins TSC1 and TSC2 regulate protein translation by inhibiting the serine/threonine kinase mTORC1 (for mammalian target of rapamycin complex 1). However, how TSC1 and TSC2 control overall protein synthesis and the translation of specific mRNAs in response to different mitogenic and nutritional stimuli is largely unknown. We show here that serum withdrawal inhibits mTORC1 signaling, causes disassembly of translation initiation complexes, and causes mRNA redistribution from polysomes to subpolysomes in wild-type mouse embryo fibroblasts (MEFs). In contrast, these responses are defective in Tsc1(-/-) or Tsc2(-/-) MEFs. Microarray analysis of polysome- and subpolysome-associated mRNAs uncovered specific mRNAs that are translationally regulated by serum, 90% of which are TSC1 and TSC2 dependent. Surprisingly, the mTORC1 inhibitor, rapamycin, abolished mTORC1 activity but only affected approximately 40% of the serum-regulated mRNAs. Serum-dependent signaling through mTORC1 and polysome redistribution of global and individual mRNAs were restored upon re-expression of TSC1 and TSC2. Serum-responsive mRNAs that are sensitive to inhibition by rapamycin are highly enriched for terminal oligopyrimidine and for very short 5' and 3' untranslated regions. These data demonstrate that the TSC1/TSC2 complex regulates protein translation through mainly mTORC1-dependent mechanisms and implicates a discrete profile of deregulated mRNA translation in tuberous sclerosis pathology.
authors.affiliation: Cancer Research Institute, University of California, San Francisco, California, USA.
authors.forename: Benoit
authors.initials: B
authors.lastname: Bilanges
authors.forename: Rhoda
authors.initials: R
authors.lastname: Argonza-Barrett
authors.forename: Marina
authors.initials: M
authors.lastname: Kolesnichenko
authors.forename: Christina
authors.initials: C
authors.lastname: Skinner
authors.forename: Manoj
authors.initials: M
authors.lastname: Nair
authors.forename: Michelle
authors.initials: M
authors.lastname: Chen
authors.forename: David
authors.initials: D
authors.lastname: Stokoe
mesh_terms: D020121:5' Untranslated Regions / Q000378:metabolism; D000818:Animals; D004622:Embryo, Mammalian / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005502:Food; D005786:Gene Expression Regulation / Q000187:drug effects; D006133:Growth Substances / Q000494:pharmacology; D006801:Humans; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D046912:Multiprotein Complexes; D011132:Polyribosomes / Q000187:drug effects; D014176:Protein Biosynthesis / Q000187:drug effects / Q000235:genetics*; D011506:Proteins; D038641:RNA 5' Terminal Oligopyrimidine Sequence / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D044967:Serum; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases; D014157:Transcription Factors / Q000378:metabolism; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000172:deficiency / Q000378:metabolism*
chemical_list: D020121:5' Untranslated Regions; D006133:Growth Substances; D046912:Multiprotein Complexes; D011506:Proteins; D012333:RNA, Messenger; C000624650:TSC1 protein, human; C000624653:TSC2 protein, human; D014157:Transcription Factors; C000624651:Tsc1 protein, mouse; C000624654:Tsc2 protein, mouse; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus