title: Characterization of PF-4708671, a novel and highly specific inhibitor of p70 ribosomal S6 kinase (S6K1).
abstract: S6K1 (p70 ribosomal S6 kinase 1) is activated by insulin and growth factors via the PI3K (phosphoinositide 3-kinase) and mTOR (mammalian target of rapamycin) signalling pathways. S6K1 regulates numerous processes, such as protein synthesis, growth, proliferation and longevity, and its inhibition has been proposed as a strategy for the treatment of cancer and insulin resistance. In the present paper we describe a novel cell-permeable inhibitor of S6K1, PF-4708671, which specifically inhibits the S6K1 isoform with a Ki of 20 nM and IC50 of 160 nM. PF-4708671 prevents the S6K1-mediated phosphorylation of S6 protein in response to IGF-1 (insulin-like growth factor 1), while having no effect upon the PMA-induced phosphorylation of substrates of the highly related RSK (p90 ribosomal S6 kinase) and MSK (mitogen- and stress-activated kinase) kinases. PF-4708671 was also found to induce phosphorylation of the T-loop and hydrophobic motif of S6K1, an effect that is dependent upon mTORC1 (mTOR complex 1). PF-4708671 is the first S6K1-specific inhibitor to be reported and will be a useful tool for delineating S6K1-specific roles downstream of mTOR.
authors: MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dow Street, Dundee, Scotland, U.K. l.r.pearce@dundee.ac.uk
authors: Laura R
authors: LR
authors: Pearce
authors: Gordon R
authors: GR
authors: Alton
authors: Daniel T
authors: DT
authors: Richter
authors: John C
authors: JC
authors: Kath
authors: Laura
authors: L
authors: Lingardo
authors: Justin
authors: J
authors: Chapman
authors: Catherine
authors: C
authors: Hwang
authors: Dario R
authors: DR
authors: Alessi
mesh_terms: D002460:Cell Line; D006801:Humans; D007093:Imidazoles / Q000737:chemistry / Q000494:pharmacology*; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes; D010766:Phosphorylation / Q000187:drug effects; D010769:Phosphothreonine / Q000378:metabolism; D010879:Piperazines / Q000737:chemistry / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D011506:Proteins; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000037:antagonists & inhibitors* / Q000378:metabolism; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D013379:Substrate Specificity / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D007093:Imidazoles; D046912:Multiprotein Complexes; C552719:PF-4708671; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011506:Proteins; D014157:Transcription Factors; D010769:Phosphothreonine; D000076222:Mechanistic Target of Rapamycin Complex 1; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D058570:TOR Serine-Threonine Kinases; C116919:mitogen and stress-activated protein kinase 1