Convergence of the Mammalian Target of Rapamycin Complex 1-and Glycogen Synthase Kinase 3-β-Signaling Pathways Regulates the Innate Inflammatory Response

The PI3K pathway and its regulation of mammalian target of rapamycin complex 1 (mTORC1) and glycogen synthase kinase 3 (GSK3) play pivotal roles in controlling inflammation. In this article, we show that mTORC1 and GSK3-beta converge and that the capacity of mTORC1 to affect the inflammatory response is due to the inactivation of GSK3-beta. Inhibition of mTORC1 attenuated GSK3 phosphorylation and increased its kinase activity. Immunoprecipitation and in vitro kinase assays demonstrated that GSK3-beta associated with a downstream target of mTORC1, p85S6K, and phosphorylated GSK3-beta. Inhibition of S6K1 abrogated the phosphorylation of GSK3-beta while increasing and decreasing the levels of IL-12 and IL-10, respectively, in LPS-stimulated monocytes. In contrast, the direct inhibition of GSK3 attenuated the capacity of S6K1 inhibition to influence the levels of IL-10 and IL-12 produced by LPS-stimulated cells. At the transcriptional level, mTORC1 inhibition reduced the DNA binding of CREB and this effect was reversed by GSK3 inhibition. As a result, mTORC1 inhibition increased the levels of NF-kappa B p65 associated with CREB-binding protein. Inhibition of NF-kappa B p65 attenuated rapamycin's ability to influence the levels of pro- or anti-inflammatory cytokine production in monocytes stimulated with LPS. These studies identify the molecular mechanism by which mTORC1 affects GSK3 and show that mTORC1 inhibition regulates pro-and anti-inflammatory cytokine production via its capacity to inactivate GSK3. The Journal of Immunology, 2011, 186: 5217-5226.