title: PRAS40 and PRR5-like protein are new mTOR interactors that regulate apoptosis.
abstract: TOR (Target of Rapamycin) is a highly conserved protein kinase and a central controller of cell growth. TOR is found in two functionally and structurally distinct multiprotein complexes termed TOR complex 1 (TORC1) and TOR complex 2 (TORC2). In the present study, we developed a two-dimensional liquid chromatography tandem mass spectrometry (2D LC-MS/MS) based proteomic strategy to identify new mammalian TOR (mTOR) binding proteins. We report the identification of Proline-rich Akt substrate (PRAS40) and the hypothetical protein Q6MZQ0/FLJ14213/CAE45978 as new mTOR binding proteins. PRAS40 binds mTORC1 via Raptor, and is an mTOR phosphorylation substrate. PRAS40 inhibits mTORC1 autophosphorylation and mTORC1 kinase activity toward eIF-4E binding protein (4E-BP) and PRAS40 itself. HeLa cells in which PRAS40 was knocked down were protected against induction of apoptosis by TNFalpha and cycloheximide. Rapamycin failed to mimic the pro-apoptotic effect of PRAS40, suggesting that PRAS40 mediates apoptosis independently of its inhibitory effect on mTORC1. Q6MZQ0 is structurally similar to proline rich protein 5 (PRR5) and was therefore named PRR5-Like (PRR5L). PRR5L binds specifically to mTORC2, via Rictor and/or SIN1. Unlike other mTORC2 members, PRR5L is not required for mTORC2 integrity or kinase activity, but dissociates from mTORC2 upon knock down of tuberous sclerosis complex 1 (TSC1) and TSC2. Hyperactivation of mTOR by TSC1/2 knock down enhanced apoptosis whereas PRR5L knock down reduced apoptosis. PRR5L knock down reduced apoptosis also in mTORC2 deficient cells. The above suggests that mTORC2-dissociated PRR5L may promote apoptosis when mTOR is hyperactive. Thus, PRAS40 and PRR5L are novel mTOR-associated proteins that control the balance between cell growth and cell death.
authors.affiliation: Biozentrum, University of Basel, Basel, Switzerland.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Thedieck
authors.forename: Pazit
authors.initials: P
authors.lastname: Polak
authors.forename: Man Lyang
authors.initials: ML
authors.lastname: Kim
authors.forename: Klaus D
authors.initials: KD
authors.lastname: Molle
authors.forename: Adiel
authors.initials: A
authors.lastname: Cohen
authors.forename: Paul
authors.initials: P
authors.lastname: Jenö
authors.forename: Cécile
authors.initials: C
authors.lastname: Arrieumerlou
authors.forename: Michael N
authors.initials: MN
authors.lastname: Hall
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002352:Carrier Proteins / Q000502:physiology*; D002460:Cell Line; D002853:Chromatography, Liquid / Q000379:methods; D003513:Cycloheximide / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes; D010750:Phosphoproteins / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D011485:Protein Binding; D011506:Proteins; D034622:RNA Interference; D058570:TOR Serine-Threonine Kinases; D053719:Tandem Mass Spectrometry; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: C484523:AKT1S1 protein, human; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; C523793:PRR5 protein, human; D010750:Phosphoproteins; D011506:Proteins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D003513:Cycloheximide; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases