The biology and mechanism of action of Suppressor of Cytokine Signaling 3 (SOCS3)

摘要

SOCS3 has been shown to be an important and non-redundant feedback inhibitor of several cytokines including LIF, IL-6, IL-11, CNTF, leptin and G-CSF. Loss of SOCS3 in vivo has profound effects on placental development, inflammation, fat-induced weight gain and insulin sensitivity. SOCS3 expression is induced by JAK/STAT signaling and it then binds to specific cytokine receptors (including gp130, G-CSF and leptin receptors). SOCS3 then inhibits JAK/STAT signaling in two distinct ways. First, SOCS3 is able to directly inhibit the catalytic activity of JAK1, JAK2 or TYK2 whilst remaining bound to the cytokine receptor. Second, SOCS3 recruits elongins B/C and cullin 5 to generate an E3 ligase that ubiquitinates both JAK and cytokine receptor targeting them for proteasomal degradation. Detailed in vivo studies have revealed that SOCS3 action not only limits the duration of cytokine signaling to prevent over-activity but it is also important in maintaining the specificity of cytokine signaling.