TGF-β Promotes Metabolic Reprogramming in Lung Fibroblasts via mTORC1-dependent ATF4 Activation
| Autor: | Gökhan M. Mutlu, G. Gokalp, Leah J. Witt, Robert B. Hamanaka, Lucas M. Kimmig, Parker S. Woods, Recep Nigdelioglu, Angelo Y. Meliton, Yufeng Tian, Rengul Cetin-Atalay, E.M. O'Leary, Kaitlyn A. Sun |
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| Rok vydání: | 2020 |
| Předmět: |
0301 basic medicine
Pulmonary and Respiratory Medicine Clinical Biochemistry Glycine mTORC1 Mechanistic Target of Rapamycin Complex 1 Activating Transcription Factor 4 mTORC2 Phosphatidylinositol 3-Kinases 03 medical and health sciences Oxygen Consumption 0302 clinical medicine Stress Physiological Transforming Growth Factor beta Fibrosis Serine medicine Humans Integrated stress response Lung Molecular Biology PI3K/AKT/mTOR pathway Original Research Chemistry TOR Serine-Threonine Kinases ATF4 Cell Biology Fibroblasts medicine.disease Mitochondria Cell biology 030104 developmental biology 030228 respiratory system Collagen Glycolysis Proto-Oncogene Proteins c-akt Signal Transduction Transforming growth factor |
| Zdroj: | Am J Respir Cell Mol Biol |
| ISSN: | 1535-4989 1044-1549 |
| Popis: | Idiopathic pulmonary fibrosis is a fatal interstitial lung disease characterized by the TGF-β (transforming growth factor-β)–dependent differentiation of lung fibroblasts into myofibroblasts, which leads to excessive deposition of collagen proteins and progressive scarring. We have previously shown that synthesis of collagen by myofibroblasts requires de novo synthesis of glycine, the most abundant amino acid found in collagen protein. TGF-β upregulates the expression of the enzymes of the de novo serine–glycine synthesis pathway in lung fibroblasts; however, the transcriptional and signaling regulators of this pathway remain incompletely understood. Here, we demonstrate that TGF-β promotes accumulation of ATF4 (activating transcription factor 4), which is required for increased expression of the serine–glycine synthesis pathway enzymes in response to TGF-β. We found that induction of the integrated stress response (ISR) contributes to TGF-β–induced ATF4 activity; however, the primary driver of ATF4 downstream of TGF-β is activation of mTORC1 (mTOR Complex 1). TGF-β activates the PI3K-Akt-mTOR pathway, and inhibition of PI3K prevents activation of downstream signaling and induction of ATF4. Using a panel of mTOR inhibitors, we found that ATF4 activation is dependent on mTORC1, independent of mTORC2. Rapamycin, which incompletely and allosterically inhibits mTORC1, had no effect on TGF-β–mediated induction of ATF4; however, Rapalink-1, which specifically targets the kinase domain of mTORC1, completely inhibited ATF4 induction and metabolic reprogramming downstream of TGF-β. Our results provide insight into the mechanisms of metabolic reprogramming in myofibroblasts and clarify contradictory published findings on the role of mTOR inhibition in myofibroblast differentiation. |
| Databáze: | OpenAIRE |
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