Mammalian target of rapamycin complex 1 (mTORC1) activity is associated with phosphorylation of raptor by mTOR.
mTORC1 contains multiple proteins and plays a central role in cell growth and metabolism. Raptor (regulatory-associated protein of mammalian target of rapamycin (mTOR)), a constitutively binding protein of mTORC1, is essential for mTORC1 activity and critical for the regulation of mTORC1 activity in response to insulin signaling and nutrient and energy sufficiency. Herein we demonstrate that mTOR phosphorylates raptor in vitro and in vivo. The phosphorylated residues were identified by using phosphopeptide mapping and mutagenesis. The phosphorylation of raptor is stimulated by insulin and inhibited by rapamycin. Importantly, the site-directed mutation of raptor at one phosphorylation site, Ser(863), reduced mTORC1 activity both in vitro and in vivo. Moreover, the Ser(863) mutant prevented small GTP-binding protein Rheb from enhancing the phosphorylation of S6 kinase (S6K) in cells. Therefore, our findings indicate that mTOR-mediated raptor phosphorylation plays an important role on activation of mTORC1.
Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908, USA. lw6j@virginia.edu
Lifu
L
Wang
John C
JC
Lawrence
Thomas W
TW
Sturgill
Thurl E
TE
Harris
D000818:Animals; D002460:Cell Line; D006801:Humans; D051379:Mice; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D013379:Substrate Specificity / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases; D014157:Transcription Factors / Q000378:metabolism*
D010750:Phosphoproteins; D014157:Transcription Factors; D010768:Phosphoserine; D011494:Protein Kinases; C546842:MTOR protein, human; C546843:mTOR protein, mouse; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus