title: SOCS2 can enhance interleukin-2 (IL-2) and IL-3 signaling by accelerating SOCS3 degradation.
abstract: Cytokine responses can be regulated by a family of proteins termed suppressors of cytokine signaling (SOCS) which can inhibit the JAK/STAT pathway in a classical negative-feedback manner. While the SOCS are thought to target signaling intermediates for degradation, relatively little is known about how their turnover is regulated. Unlike other SOCS family members, we find that SOCS2 can enhance interleukin-2 (IL-2)- and IL-3-induced STAT phosphorylation following and potentiate proliferation in response to cytokine stimulation. As a clear mechanism for these effects, we demonstrate that expression of SOCS2 results in marked proteasome-dependent reduction of SOCS3 and SOCS1 protein expression. Furthermore, we provide evidence that this degradation is dependent on the presence of an intact SOCS box and that the loss of SOCS3 is enhanced by coexpression of elongin B/C. This suggests that SOCS2 can bind to SOCS3 and elongin B/C to form an E3 ligase complex resulting in the degradation of SOCS3. Therefore, SOCS2 can enhance cytokine responses by accelerating proteasome-dependent turnover of SOCS3, suggesting a mechanism for the gigantism observed in SOCS2 transgenic mice.
authors.affiliation: Infection and Immunity Group, Centre for Cancer Research and Cell Biology, Queens University, Belfast, UK.
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Tannahill
authors.forename: Joanne
authors.initials: J
authors.lastname: Elliott
authors.forename: Anna C
authors.initials: AC
authors.lastname: Barry
authors.forename: Linda
authors.initials: L
authors.lastname: Hibbert
authors.forename: Nicolas A
authors.initials: NA
authors.lastname: Cacalano
authors.forename: James A
authors.initials: JA
authors.lastname: Johnston
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000378:metabolism*; D007377:Interleukin-3 / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D007376:Interleukin-2; D007377:Interleukin-3; D012333:RNA, Messenger; D011994:Recombinant Proteins; C106643:SOCS2 protein, human; C106644:SOCS3 protein, human; C491409:Socs2 protein, mouse; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins