title: PI3K/mTORC2 regulates TGF-β/Activin signalling by modulating Smad2/3 activity via linker phosphorylation.
abstract: Crosstalk between the phosphatidylinositol 3-kinase (PI3K) and the transforming growth factor-β signalling pathways play an important role in regulating many cellular functions. However, the molecular mechanisms underpinning this crosstalk remain unclear. Here, we report that PI3K signalling antagonizes the Activin-induced definitive endoderm (DE) differentiation of human embryonic stem cells by attenuating the duration of Smad2/3 activation via the mechanistic target of rapamycin complex 2 (mTORC2). Activation of mTORC2 regulates the phosphorylation of the Smad2/3-T220/T179 linker residue independent of Akt, CDK and Erk activity. This phosphorylation primes receptor-activated Smad2/3 for recruitment of the E3 ubiquitin ligase Nedd4L, which in turn leads to their degradation. Inhibition of PI3K/mTORC2 reduces this phosphorylation and increases the duration of Smad2/3 activity, promoting a more robust mesendoderm and endoderm differentiation. These findings present a new and direct crosstalk mechanism between these two pathways in which mTORC2 functions as a novel and critical mediator.
authors.affiliation: Department of Surgery and Cancer, Institute of Reproductive and Developmental Biology, Imperial College London, Du Cane Road, London W12 0NN, UK.
authors.forename: Jason S L
authors.initials: JS
authors.lastname: Yu
authors.affiliation: Department of Surgery and Cancer, Institute of Reproductive and Developmental Biology, Imperial College London, Du Cane Road, London W12 0NN, UK.
authors.forename: Thamil Selvee
authors.initials: TS
authors.lastname: Ramasamy
authors.affiliation: Department of Surgery and Cancer, Institute of Reproductive and Developmental Biology, Imperial College London, Du Cane Road, London W12 0NN, UK.
authors.forename: Nick
authors.initials: N
authors.lastname: Murphy
authors.affiliation: Department of Surgery and Cancer, Institute of Reproductive and Developmental Biology, Imperial College London, Du Cane Road, London W12 0NN, UK.
authors.forename: Marie K
authors.initials: MK
authors.lastname: Holt
authors.affiliation: Department of Surgery and Cancer, Institute of Reproductive and Developmental Biology, Imperial College London, Du Cane Road, London W12 0NN, UK.
authors.forename: Rafal
authors.identifier: 0000000302118435
authors.initials: R
authors.lastname: Czapiewski
authors.affiliation: Department of Surgery and Cancer, Institute of Reproductive and Developmental Biology, Imperial College London, Du Cane Road, London W12 0NN, UK.
authors.forename: Shi-Khai
authors.initials: SK
authors.lastname: Wei
authors.affiliation: Department of Surgery and Cancer, Institute of Reproductive and Developmental Biology, Imperial College London, Du Cane Road, London W12 0NN, UK.
authors.forename: Wei
authors.initials: W
authors.lastname: Cui
mesh_terms: D028341:Activins / Q000378:metabolism*; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D053595:Embryonic Stem Cells / Q000378:metabolism*; D004707:Endoderm / Q000166:cytology; D057809:HEK293 Cells; D006801:Humans; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D020239:Receptor Cross-Talk; D051896:Smad Proteins, Receptor-Regulated / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D028341:Activins; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes; D019869:Phosphatidylinositol 3-Kinases; D051896:Smad Proteins, Receptor-Regulated; D058570:TOR Serine-Threonine Kinases; D016212:Transforming Growth Factor beta