Identification of Protor as a novel Rictor-binding component of mTOR complex-2.
The mTOR (mammalian target of rapamycin) protein kinase is an important regulator of cell growth. Two complexes of mTOR have been identified: complex 1, consisting of mTOR-Raptor (regulatory associated protein of mTOR)-mLST8 (termed mTORC1), and complex 2, comprising mTOR-Rictor (rapamycininsensitive companion of mTOR)-mLST8-Sin1 (termed mTORC2). mTORC1 phosphorylates the p70 ribosomal S6K (S6 kinase) at its hydrophobic motif (Thr389), whereas mTORC2 phosphorylates PKB (protein kinase B) at its hydrophobic motif (Ser473). In the present study, we report that widely expressed isoforms of unstudied proteins termed Protor-1 (protein observed with Rictor-1) and Protor-2 interact with Rictor and are components of mTORC2. We demonstrate that immunoprecipitation of Protor-1 or Protor-2 results in the co-immunoprecipitation of other mTORC2 subunits, but not Raptor, a specific component of mTORC1. We show that detergents such as Triton X-100 or n-octylglucoside dissociate mTOR and mLST8 from a complex of Protor-1, Sin1 and Rictor. We also provide evidence that Rictor regulates the expression of Protor-1, and that Protor-1 is not required for the assembly of other mTORC2 subunits into a complex. Protor-1 is a novel Rictor-binding subunit of mTORC2, but further work is required to establish its role.
Pearce
Laura R
LR
MRC Protein Phosphorylation Unit, School of Life Sciences, MSI/WTB Complex, University of Dundee, Dundee DD1 5EH, Scotland, UK. l.r.pearce@dundee.ac.uk).
Huang
Xu
X
Boudeau
Jérôme
J
Pawłowski
Rafał
R
Wullschleger
Stephan
S
Deak
Maria
M
Ibrahim
Adel F M
AF
Gourlay
Robert
R
Magnuson
Mark A
MA
Alessi
Dario R
DR
D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D020868:Gene Silencing; D006801:Humans; D011485:Protein Binding; D020033:Protein Isoforms; D011494:Protein Kinases / Q000378:metabolism*; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D058570:TOR Serine-Threonine Kinases
D002352:Carrier Proteins; D020033:Protein Isoforms; C492571:RICTOR protein, human; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D011494:Protein Kinases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases