FIG. 13.
Current model for IL-7R regulation of survival and proliferation. IL-7 binding to the receptor brings together the α and γc chains and their associated kinases, Jak1 (bound to Box1) and Jak3, respectively. The two kinases phosphorylate one another and increase their enzymatic activity. These kinases then phosphorylate Y449, which serves as a docking site for Stat5 and additional unknown proteins that are required for synthesis of Bcl2, cytosolic retention of Bax, and cell proliferation. A second pathway leads from Jak1 (independent of Y449) and induces phosphorylation of Bad, Stat1, and Stat3.