SOCS family proteins form part of a classical negative feedback system that regulates cytokine signal transduction. SOCS3 is involved in negative regulation of cytokines that signal through the JAK/STAT pathway. Inhibits cytokine signal transduction by binding to tyrosine kinase receptors including IL6ST/gp130, LIF, erythropoietin, insulin, IL12, GCSF and leptin receptors (PubMed:10821852, PubMed:12754505, PubMed:9889194). Binding to JAK2 inhibits its kinase activity and regulates IL6 signaling (PubMed:12754505, PubMed:9889194). Suppresses fetal liver erythropoiesis (PubMed:10490101). Regulates onset and maintenance of allergic responses mediated by T-helper type 2 cells (PubMed:12847520). Probable 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 (By similarity).