SOCS family proteins form part of a classical negative feedback system that regulates cytokine signal transduction. SOCS1 is involved in negative regulation of cytokines that signal through the JAK/STAT3 pathway. Through binding to JAKs, inhibits their kinase activity. In vitro, also suppresses Tec protein-tyrosine activity (By similarity). Appears to be a major regulator of signaling by interleukin 6 (IL6) and leukemia inhibitory factor(LIF). Regulates interferon-gamma mediated sensory neuron survival. Implicated, through SOCS box binding, in ubiquitin-dependent protein degradation. High expression in thymus. Lower expression in lung and spleen.