Fig. 1

IL-7 induced intracellular signaling pathways. The non-hematopoietic cell-derived cytokine IL-7 has to combine with the IL-7R on the cell membrane to realize its biological activity. IL-7R complex is a transmembrane heterodimer consisting of two subunits, the ligand-binding IL-7 receptor α chain and the common signal-transducing γ chain (γc chain), which is shared by IL-7R, IL-2R, IL-4R, IL-9R, IL-15R, and IL-21R. JAK/STAT, PI3K-Akt, and MAPK signaling pathways are involved and have specific roles in IL-7-mediated functions. Upon IL-7 binding to its receptor, IL-7Rα, the α and γc subunits dimerize. This induces intracellular, non-receptor tyrosine kinases, Janus kinases (JAK) 1 and 3, to activate and mediate the IL-7 signaling transduction. To this end, the transcription factor Miz1 (Myc-interacting zinc finger protein 1) recruits JAK1 to IL-7Rα. This induces phosphorylation of JAK1 and JAK3, which in turn triggers STAT5 phosphorylation with subsequent dimerization to regulate gene expression, i.e., stimulate anti-apoptotic gene expression and inhibit pro-apoptotic gene expression. On the other hand, JAK1 and JAK3 phosphorylation leads to the activation of MAPK and PI3K-Akt signaling pathway as presented in the figure