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

• DOI: 10.1038/cmi.2015.43
• Publication Date: 2015-05-25T13:56:23Z
• Authors: Tao Yang; Linnan Zhu; Yanhua Zhai; Qingjie Zhao; Jianxia Peng; Hongbing Zhang; Zhongzhou Yang; Lianfeng Zhang; Wenjun Ding; Yong Zhao
• Keywords: Mice, Knockout; 0301 basic medicine; 0303 health sciences; CCAAT-Enhancer-Binding Protein-beta; Macrophages; TOR Serine-Threonine Kinases; Tumor Suppressor Proteins; Interleukin-1beta; NF-kappa B; Mechanistic Target of Rapamycin Complex 1; Models, Biological; Tuberous Sclerosis Complex 1 Protein; Enzyme Activation; 03 medical and health sciences; Multiprotein Complexes; Animals; Mitogen-Activated Protein Kinases; Signal Transduction

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-α (TNF-α) and IL-12 to pro-inflammatory stimuli, but whether and how TSC1 regulates pro-IL-1β 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-1β in macrophages following lipopolysaccharide stimulation. Such decreased pro-IL-1β 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-1β synthesis, suggesting that TSC1 positively controls pro-IL-1β expression through mTORC1 pathway. Moreover, mechanism studies suggest that mTORC1-mediated downregulation of the CCAAT enhancer-binding protein (C/EBPβ) critically contributes to the defective pro-IL-1β expression. Overall, these findings highlight a critical role of TSC1 in regulating innate immunity by control of the mTOR1-C/EBPβ pathway.