SOCS family proteins form part of a classical negative feedback system that regulates cytokine signal transduction. CIS is involved in the negative regulation of cytokines that signal through the JAK-STAT5 pathway such as erythropoietin, prolactin and interleukin 3 (IL3) receptor. Inhibits STAT5 trans-activation by suppressing its tyrosine phosphorylation. May be a substrate- recognition component of a SCF-like ECS (Elongin BC-CUL2/5-SOCS- box protein) E3 ubiquitin-protein ligase complex which mediates the ubiquitination and subsequent proteasomal degradation of target proteins. Stably associated with the tyrosine-phosphorylated IL3 receptor beta chain and tyrosine-phosphorylated EPO receptor (EPOR). By a subset of cytokines including EPO/erythropoietin. Expressed in various epithelial tissues. Abundantly expressed in liver and kidney, and to a lesser extent in lung. The tissue distribution of isoforms 1 and 1B is distinct. 3 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.
Molecular Function: protein binding; protein kinase inhibitor activity
Biological Process: cytokine and chemokine mediated signaling pathway; negative regulation of insulin receptor signaling pathway; negative regulation of JAK-STAT cascade; negative regulation of protein kinase activity; post-translational protein modification