The IKKâ related kinase TBK1 activates mTORC1 directly in response to growth factors and innate immune agonists

Abstract

The innate immune kinase TBK1 initiates inflammatory responses to combat infectious pathogens by driving production of type I interferons. TBK1 also controls metabolic processes and promotes oncogeneâ induced cell proliferation and survival. Here, we demonstrate that TBK1 activates mTOR complex 1 (mTORC1) directly. In cultured cells, TBK1 associates with and activates mTORC1 through siteâ specific mTOR phosphorylation (on S2159) in response to certain growth factor receptors (i.e., EGFâ receptor but not insulin receptor) and pathogen recognition receptors (PRRs) (i.e., TLR3; TLR4), revealing a stimulusâ selective role for TBK1 in mTORC1 regulation. By studying cultured macrophages and those isolated from genome edited mTOR S2159A knockâ in mice, we show that mTOR S2159 phosphorylation promotes mTORC1 signaling, IRF3 nuclear translocation, and IFNâ β production. These data demonstrate a direct mechanistic link between TBK1 and mTORC1 function as well as physiologic significance of the TBK1â mTORC1 axis in control of innate immune function. These data unveil TBK1 as a direct mTORC1 activator and suggest unanticipated roles for mTORC1 downstream of TBK1 in control of innate immunity, tumorigenesis, and disorders linked to chronic inflammation.SynopsisTBK1, an IKKâ related kinase that drives interferon production as well cancer cell proliferation and survival, phosphorylates mTOR to activate mTORC1 in response to EGF and innate immune agonists, suggesting unanticipated roles for mTORC1 downstream of TBK1 in control of innate immunity and tumorigenesis.TBK1 interacts with mTORC1 and phosphorylates mTOR on S2159 to increase its catalytic activity.Cells lacking TBK1 or expressing a mTOR S2159A allele exhibit reduced mTORC1 signaling in response to EGFâ receptor and TLR3/4 activation.Primary macrophages derived from genome edited mTOR S2159A mice exhibit reduced mTORC1 signaling in response to TLR3/4 activation.Primary macrophages treated with rapamycin as well as those derived from mTORS2159A mice produce reduced levels of IFNâ β due to impaired nuclear translocation of the transcription factor IRF3.Innate immune kinase TBK1â dependent activation of mTORC1 occurs in response to pathogen recognition and EGF receptor activation and drives interferon production, thus highlighting the role of mTOR for innate immunity.