Background information
Interleukin 2 (IL2) receptor gamma chain (IL5212R gamma) is a cell surface glycoprotein expressed by a variety of leukocytes including T cells, B cells, NK cells, monocytes, macrophages, and neutrophils. IL2R gamma is also known as CD132, common cytokine receptor gamma chain, and gamma c. IL2R gamma forms complexes with other cell surface proteins including CD25 (IL2R alpha), CD122 (IL2R beta), CD124 (IL4R alpha), CD127 (IL7R), and others. IL2R gamma complexed with other cell surface proteins forms receptors for the cytokines IL2, IL4, IL7, IL9, and IL15. Acting through the IL2R gamma containing complexes, these cytokines regulate lymphocyte development and activation. Chemical cross linking experiments reveal that IL2R gamma is able to bind cytokines only when complexed with these other cell surface proteins. In addition to interacting with other cell surface glycoproteins, IL2R gamma associates with several cytoplasmic tyrosine kinases including JAK3 (Janus Kinase 3), JAK1, Syc, and Lyc. Cytokine binding to the IL2R gamma containing receptor complexes activates these tyrosine kinases. Once activated, these tyrosine kinases phosphorylate their associated receptors, creating docking sites for signaling molecules such as PI 3 kinase. The activated tyrosine kinases also phosphorylate downstream regulators including STAT3 (Signal Transducer and Activator of Transcription 3), STAT5, and STAT6. The various cytokines that bind to IL2R gamma containing receptor complexes exert their effects through unique repertoires of cytoplasmic signaling molecules. IL2, IL7, and IL9 exert their effects through cascades, which activate STAT3 and STAT5, while IL4 activates STAT6. IL2 and IL15 exert their effects through cascades, which activate the MAP kinase cascade. IL7 exerts its effects through a cascade that results in VDJ immunoglobulin gene rearrangement.
