Figure 1.

Cytokine signaling via the JAK/STAT pathway and its regulation by SOCS proteins. Schematic representation of a cytokine (pink) binding to the extracellular portion of its cognate cytokine receptor (CytoR—gray), to cause activation of associated intracellular Janus kinases (JAK—blue), which mediate phosphorylation (P—purple) of tyrosine residues found on components of the receptor complex. These form docking sites for signal transducer and activator of transcription proteins (STAT—green), which also undergo phosphorylation to form STAT dimers. These translocate into the nucleus to activate transcription of target genes encoding effector proteins (orange) as well as SOCS proteins (red) that provide negative feedback regulation.