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Published on: August 13, 2013
mTORC1 Promotes T-bet Phosphorylation To Regulate Th1 Differentiation
Olesya Chornoguz1,2,3,4, Robert S Hagan1,2,3,5, Azeb Haile1,2,3
1Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21287.
Mice lacking Rheb, an mTORC1 activator, show reduced IFN-γ secretion due to impaired T-bet phosphorylation. This study identifies novel phosphorylation sites on T-bet regulated by mTORC1, impacting Th1 differentiation.
Area of Science:
- Immunology
- Cellular Biology
- Molecular Biology
Background:
- CD4+ T cells are crucial for adaptive immunity.
- Th1 differentiation is essential for controlling intracellular pathogens.
- IFN-γ secretion by Th1 cells is critical for immune responses.
Purpose of the Study:
- To investigate the role of mTORC1 signaling in regulating T-bet phosphorylation.
- To identify specific phosphorylation sites on T-bet affected by mTORC1.
- To elucidate the mechanism by which mTORC1 controls Th1 differentiation.
Main Methods:
- Targeted mass-spectrometry (multiple reaction monitoring) was used to quantify T-bet phosphopeptides.
- Analysis of Rheb-deficient CD4+ T cells and rapamycin-treated cells.
- Alanine mutagenesis of T-bet phosphorylation sites.
Main Results:
- Six T-bet phosphorylation sites were identified, four of which are regulated by mTORC1.
- Simultaneous mutation of three mTORC1-dependent sites significantly reduced IFN-γ expression.
- Mutant T-bet failed to recruit chromatin remodeling complexes to the Ifng gene promoter.
Conclusions:
- mTORC1 signaling directly regulates T-bet phosphorylation.
- T-bet phosphorylation is a novel mechanism controlling Th1 differentiation.
- mTORC1-dependent phosphorylation of T-bet is critical for Ifng gene activation.
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