TSC1 controls IL-1β expression in macrophages via mTORC1-dependent C/EBPβ pathway

Abstract

The tuberous sclerosis complex 1 (TSC1) is a tumor suppressor that inhibits the mammalian target of rapamycin (mTOR), which serves as a key regulator of inflammatory responses after bacterial stimulation in monocytes, macrophages, and primary dendritic cells. Previous studies have shown that TSC1 knockout (KO) macrophages produced increased inflammatory responses including tumor necrosis factor-a (TNF-a) and IL-12 to pro-inflammatory stimuli, but whether and how TSC1 regulates pro-IL-1b expression remains unclear. Here using a mouse model in which myeloid lineage-specific deletion of TSC1 leads to constitutive mTORC1 activation, we found that TSC1 deficiency resulted in impaired expression of pro-IL-1b in macrophages following lipopolysaccharide stimulation. Such decreased pro-IL-1b expression in TSC1 KO macrophages was rescued by reducing mTORC1 activity with rapamycin or deletion of mTOR. Rictor deficiency has no detectable effect on pro-IL-1b synthesis, suggesting that TSC1 positively controls pro-IL-1b expression through mTORC1 pathway. Moreover, mechanism studies suggest that mTORC1-mediated downregulation of the CCAAT enhancer-binding protein (C/EBPb) critically contributes to the defective pro-IL-1b expression. Overall, these findings highlight a critical role of TSC1 in regulating innate immunity by control of the mTOR1-C/EBPb pathway. Cellular & Molecular Immunology

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“…Quantitative real-time RT-PCR analysis Total cellular RNA was extracted from the differentiated and subsequently polarized macrophages using an EZNA MicroElute Total RNA Kit (Omega Bio-Tek). 70 The reverse transcription reaction was performed with oligo (dT) primers and AMV reverse transcriptase XL (Takara Bio, Shiga, Japan), and real-time PCR was performed using TB Green Premix Ex Taq (Takara Bio, Shiga, Japan). All primers used in the present study are listed in Supplementary Table 6.…”

Characterization and biological significance of IL-23-induced neutrophil polarization

“…The mRNA expression level of each gene was normalized to the housekeeping gene hypoxanthinephosphoribosyl transferase (HPRT), as reported previously. 33,37 For the inhibitor assay, cells were pretreated with various inhibitors for 30 min, and then treated with IL-23 for 12 h.…”

MTOR signaling is essential for the development of thymic epithelial cells and the induction of central immune tolerance

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