10779/crick.11549547.v1 Brintha Selvarajah Brintha Selvarajah Ilan Azuelos Ilan Azuelos Manuela Platé Manuela Platé Delphine Guillotin Delphine Guillotin Ellen J Forty Ellen J Forty Greg Contento Greg Contento Hannah V Woodcock Hannah V Woodcock Matthew Redding Matthew Redding Adam Taylor Adam Taylor Gino Brunori Gino Brunori Pascal F Durrenberger Pascal F Durrenberger Riccardo Ronzoni Riccardo Ronzoni Andy D Blanchard Andy D Blanchard Paul F Mercer Paul F Mercer Dimitrios Anastasiou Dimitrios Anastasiou Rachel C Chambers Rachel C Chambers mTORC1 amplifies the ATF4-dependent de novo serine-glycine pathway to supply glycine during TGF-β1-induced collagen biosynthesis. The Francis Crick Institute 2020 Anastasiou FC001033 MET-ack 0601 Biochemistry and Cell Biology 2020-01-08 16:58:06 Journal contribution https://crick.figshare.com/articles/journal_contribution/mTORC1_amplifies_the_ATF4-dependent_de_novo_serine-glycine_pathway_to_supply_glycine_during_TGF-_1-induced_collagen_biosynthesis_/11549547 The differentiation of fibroblasts into a transient population of highly activated, extracellular matrix (ECM)-producing myofibroblasts at sites of tissue injury is critical for normal tissue repair. Excessive myofibroblast accumulation and persistence, often as a result of a failure to undergo apoptosis when tissue repair is complete, lead to pathological fibrosis and are also features of the stromal response in cancer. Myofibroblast differentiation is accompanied by changes in cellular metabolism, including increased glycolysis, to meet the biosynthetic demands of enhanced ECM production. Here, we showed that transforming growth factor-β1 (TGF-β1), the key pro-fibrotic cytokine implicated in multiple fibrotic conditions, increased the production of activating transcription factor 4 (ATF4), the transcriptional master regulator of amino acid metabolism, to supply glucose-derived glycine to meet the amino acid requirements associated with enhanced collagen production in response to myofibroblast differentiation. We further delineated the signaling pathways involved and showed that TGF-β1-induced ATF4 production depended on cooperation between canonical TGF-β1 signaling through Smad3 and activation of mechanistic target of rapamycin complex 1 (mTORC1) and its downstream target eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1). ATF4, in turn, promoted the transcription of genes encoding enzymes of the de novo serine-glycine biosynthetic pathway and glucose transporter 1 (GLUT1). Our findings suggest that targeting the TGF-β1-mTORC1-ATF4 axis may represent a novel therapeutic strategy for interfering with myofibroblast function in fibrosis and potentially in other conditions, including cancer.