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. Author manuscript; available in PMC: 2011 Oct 1.
Published in final edited form as: Semin Immunol. 2010 Oct;22(5):294–302. doi: 10.1016/j.smim.2010.04.013

Figure 2.

Figure 2

Foxo1 as a sensor for TCR and IL-7 signals in thymocytes. In mature T cells, IL-7 activates PI-3 kinase and Akt, thereby causing Foxo1 phosphorylation. As Foxo1 promotes IL-7Rα expression, IL-7-mediated Foxo1 phosphorylation contributes to repress IL-7Rα expression and thereby IL-7 signaling. In SP thymocytes, where Foxo1 also promotes IL-7Rα expression, both TCR signaling and IL-7 signaling potentially contribute to PI-3 kinase activation. This mechanism could have a ‘licensing’ function by preventing the terminal maturation of SP thymocytes unable to cease TCR signaling. In tumor cells, IKKβ has been shown to phosphorylate Foxo3 and prevent its nuclear translocation [145]; it is not yet known which stimulus activates IKKβ, and whether it also acts on Foxo1 in thymocytes or T cells.