RECENT ADVANCES IN THE UNDERSTANDING OF INTERLEUKIN-2 SIGNAL-TRANSDUCTION

Interleukin-2 is one of the critical cytokines that control the prolif eration and differentiation of cells of the immune system. The present article briefly reviews the current and recently established knowledg e on the intracellular signaling events that convert the initial inter action of IL-2 with its receptor into pathways leading to the various biological functions. A first step in IL-2 signaling is the activation of several protein tyrosine kinases that phosphorylate a large array of intracellular substrates including the receptor complex. Phosphoryl ated tyrosine residues within the receptor then serve as docking sites for multimolecular signaling complexes that initiate three major path ways: the Jak-STAT pathway controlling gene transcription, the Ras-MAP K pathway leading to cell proliferation and gene transcription as well , and the PI3-kinase pathway involved in antiapoptotic signaling and o rganization of the cytoskeleton. Finally, other recently identified an d presumably important tyrosine kinase substrates, whose significance is not yet fully understood, are described.