Convergence of the mammalian target of rapamycin complex 1- and glycogen synthase kinase 3-ß-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-ß converge and that the capacity of mTORC1 to affect the inflammatory response is due to the inactivation of GSK3-ß. Inhibition of mTORC1 attenuated GSK3 phosphorylation and increased its kinase activity. Immunoprecipitation and in vitro kinase assays demonstrated that GSK3-ß associated with a downstream target of mTORC1, p85S6K, and phosphorylated GSK3-ß. Inhibition of S6K1 abrogated the phosphorylation of GSK3-ß 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-κB p65 associated with CREB-binding protein. Inhibition of NF-κB 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 role of glycogen synthase kinase 3 in regulating IFN-ß-mediated IL-10 production.

The ability of IFN-ß to induce IL-10 production from innate immune cells is important for its anti-inflammatory properties and is believed to contribute to its therapeutic value in treating multiple sclerosis patients. In this study, we identified that IFN-ß stimulates IL-10 production by activating the JAK1- and PI3K-signaling pathways. JAK1 activity was required for IFN-ß to activate PI3K and Akt1 that resulted in repression of glycogen synthase kinase 3 (GSK3)-ß activity. IFN-ß-mediated suppression of GSK3-ß promoted IL-10, because IL-10 production by IFN-ß-stimulated dendritic cells (DC) expressing an active GSK3-ß knockin was severely reduced, whereas pharmacological or genetic inhibition of GSK3-ß augmented IL-10 production. IFN-ß increased the phosphorylated levels of CREB and STAT3 but only CREB levels were affected by PI3K. Also, a knockdown in CREB, but not STAT3, affected the capacity of IFN-ß to induce IL-10 from DC. IL-10 production by IFN-ß-stimulated DC was shown to suppress IFN-γ and IL-17 production by myelin oligodendrocyte glycoprotein-specific CD4(+) T cells, and this IL-10-dependent anti-inflammatory effect was enhanced by directly targeting GSK3 in DC. These findings highlight how IFN-ß induces IL-10 production and the importance that IL-10 plays in its anti-inflammatory properties, as well as identify a therapeutic target that could be used to increase the IL-10-dependent anti-inflammatory properties of IFN-ß.