PRAS40 and PRR5-like protein are new mTOR interactors that regulate apoptosis

PLoS One. 2007 Nov 21;2(11):e1217. doi: 10.1371/journal.pone.0001217.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Apoptosis / drug effects
  • Apoptosis / physiology*
  • Carrier Proteins / physiology*
  • Cell Line
  • Chromatography, Liquid / methods
  • Cycloheximide / pharmacology
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Mechanistic Target of Rapamycin Complex 1
  • Multiprotein Complexes
  • Phosphoproteins / metabolism
  • Phosphoproteins / physiology*
  • Phosphorylation
  • Protein Binding
  • Proteins
  • RNA Interference
  • TOR Serine-Threonine Kinases
  • Tandem Mass Spectrometry
  • Transcription Factors / antagonists & inhibitors
  • Transcription Factors / metabolism*
  • Tumor Necrosis Factor-alpha / pharmacology

Substances

  • AKT1S1 protein, human
  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • Intracellular Signaling Peptides and Proteins
  • Multiprotein Complexes
  • PRR5 protein, human
  • Phosphoproteins
  • Proteins
  • Transcription Factors
  • Tumor Necrosis Factor-alpha
  • Cycloheximide
  • TOR Serine-Threonine Kinases
  • Mechanistic Target of Rapamycin Complex 1