title: Phosphorylation dynamics of eukaryotic initiation factor 4E binding protein 1 (4E-BP1) is discordant with its potential to interact with eukaryotic initiation factor 4E (eIF4E).
abstract: Mammalian target of rapamycin (mTOR) controls cellular growth and proliferation by virtue of its ability to regulate protein translation. Eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1) - a key mTOR substrate, binds and sequesters eIF4E to impede translation initiation that is supposedly overcome upon 4E-BP1 phosphorylation by mTOR. Ambiguity surrounding the precise identity of mTOR regulated sites in 4E-BP1 and their invariable resistance to mTOR inactivation raises concerns about phospho-regulated model proposed for 4E:4E-BP1 interaction. Our attempt to mimic dephosphorylation associated with rapamycin response by introducing phospho deficient mutants for sites implicated in regulating 4E:4E-BP1 interaction individually or globally highlighted no obvious difference in the quantum of their association with CAP bound 4E when compared with their phosphomimicked counterparts or the wild type 4E-BP1. TOS or RAIP motif deletion variants compromised for raptor binding and resultant phosphodeficiency did little to influence their association with CAP bound 4E. Interestingly ectopic expression of ribosomal protein S6 kinase 1 (S6K1) that restored 4E-BP1 sensitivity to rapamycin/Torin reflected by instant loss of 4E-BP1 phosphorylation, failed to bring about any obvious change in 4E:4E-BP1 stoichiometry. Our data clearly demonstrate a potential disconnect between rapamycin response of 4E-BP1 and its association with CAP bound 4E.
authors: Department of Biotechnology and Bioinformatics, Science Block, Ground Floor University of Kashmir, Srinagar, Jammu and Kashmir 190006, India.
authors: Mehvish
authors: M
authors: Showkat
authors: Department of Biotechnology and Bioinformatics, Science Block, Ground Floor University of Kashmir, Srinagar, Jammu and Kashmir 190006, India.
authors: Mushtaq A
authors: MA
authors: Beigh
authors: Department of Biotechnology and Bioinformatics, Science Block, Ground Floor University of Kashmir, Srinagar, Jammu and Kashmir 190006, India.
authors: Basharat B
authors: BB
authors: Bhat
authors: Department of Biotechnology and Bioinformatics, Science Block, Ground Floor University of Kashmir, Srinagar, Jammu and Kashmir 190006, India.
authors: Asiya
authors: A
authors: Batool
authors: Department of Biotechnology and Bioinformatics, Science Block, Ground Floor University of Kashmir, Srinagar, Jammu and Kashmir 190006, India. Electronic address: andrabik@uok.edu.in.
authors: Khurshid I
authors: KI
authors: Andrabi
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D001798:Blood Proteins / Q000494:pharmacology; D018797:Cell Cycle Proteins; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D001798:Blood Proteins; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D039561:Eukaryotic Initiation Factor-4E; D010750:Phosphoproteins; C031024:torin; C546842:MTOR protein, human; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; C448901:ribosomal protein S6 kinase, 70kD, polypeptide 1; D020123:Sirolimus
keywords: 4E; 4E-BP1; Rapamycin; S6 kinase; mTOR