Re-examination of the Role of Suppressor of Cytokine Signaling 1 (SOCS1) in the Regulation of Toll-like Receptor Signaling

Suppressor of cytokine signaling 1 (SOCS1) is an obligate negative regulator of cytokine signaling and most importantly in vivo, signaling via the interferon-γ (IFN-γ) receptor. SOCS1, via its Src homology 2 domain, binds to phosphotyrosine residues in its targets, reducing the amplitude of signaling from cytokine receptors. SOCS1 is also implicated in blocking Toll-like receptor (TLR) signaling in macrophages activated by TLR agonists such as lipopolysaccharide (LPS), thus regulating multiple steps in the activation of innate immune responses. To rigorously test this, we isolated macrophages from Socs1-/- mice on multiple genetic backgrounds. We found no evidence that SOCS1 blocked TLR-activated pathways, endotoxin tolerance, or nitric oxide production. However, Socs1-/-;IFN-γ-/- mice were extremely susceptible to LPS challenge, confirming previous findings. Because LPS induces IFN-β production from macrophages, we tested whether SOCS1 regulates IFN-α/β receptor signaling. We find that SOCS1 is required to inhibit IFN-α/β receptor signaling in vitro. Furthermore, the absence of a single allele encoding TYK2, a JAK (Janus kinase) family member essential IFN-α/β receptor signaling, rescued Socs1-/- mice from early lethality, even in the presence of IFN-γ. We conclude that previous reports linking SOCS1 to TLR signaling are most likely due to effects on IFN-α/β receptor signaling. Suppressor of cytokine signaling 1 (SOCS1) is an obligate negative regulator of cytokine signaling and most importantly in vivo, signaling via the interferon-γ (IFN-γ) receptor. SOCS1, via its Src homology 2 domain, binds to phosphotyrosine residues in its targets, reducing the amplitude of signaling from cytokine receptors. SOCS1 is also implicated in blocking Toll-like receptor (TLR) signaling in macrophages activated by TLR agonists such as lipopolysaccharide (LPS), thus regulating multiple steps in the activation of innate immune responses. To rigorously test this, we isolated macrophages from Socs1-/- mice on multiple genetic backgrounds. We found no evidence that SOCS1 blocked TLR-activated pathways, endotoxin tolerance, or nitric oxide production. However, Socs1-/-;IFN-γ-/- mice were extremely susceptible to LPS challenge, confirming previous findings. Because LPS induces IFN-β production from macrophages, we tested whether SOCS1 regulates IFN-α/β receptor signaling. We find that SOCS1 is required to inhibit IFN-α/β receptor signaling in vitro. Furthermore, the absence of a single allele encoding TYK2, a JAK (Janus kinase) family member essential IFN-α/β receptor signaling, rescued Socs1-/- mice from early lethality, even in the presence of IFN-γ. We conclude that previous reports linking SOCS1 to TLR signaling are most likely due to effects on IFN-α/β receptor signaling. SOCS1 is a member of a family of proteins that regulate cytokine signaling pathways via inhibition of key tyrosine phosphorylation events on cytokine receptors and signaling molecules such as JAK family members (1Alexander W.S. Hilton D.J. Annu. Rev. Immunol. 2004; 22: 503-529Crossref PubMed Scopus (608) Google Scholar). The inhibitory effects of SOCS proteins are mediated by two domains found in all SOCS family members: an SH2 1The abbreviations used are: SH2, Src homology 2; SOCS, suppressor of cytokine signaling; STAT, signal transducer and activator of transcription; IFN, interferon; IL-12, interleukin-12; BMDM, bone marrow-derived macrophage; TLR, Toll-like receptor; LPS, lipopolysaccharide; TNF, tumor necrosis factor; ELISA, enzyme-linked immunosorbent assay; dsRNA, double-stranded RNA; ERK, extracellular signal-regulated kinase; JAK, Janus kinase. domain that can bind phosphorylated tyrosine residues and the SOCS box that functions as a ubiquitin E3 ligase and thus potentially directs substrate proteins to the protein degradation machinery (1Alexander W.S. Hilton D.J. Annu. Rev. Immunol. 2004; 22: 503-529Crossref PubMed Scopus (608) Google Scholar). Although the biochemical events associated with SOCS function are poorly understood, overwhelming genetic evidence has demonstrated multiple members of the SOCS family are essential for the regulation of specific cytokine signal transduction events in vivo. Mice lacking SOCS1 die 10–20 days after birth (2Marine J.C. Topham D.J. McKay C. Wang D. Parganas E. Stravopodis D. Yoshimura A. Ihle J.N. Cell. 1999; 98: 609-616Abstract Full Text Full Text PDF PubMed Scopus (454) Google Scholar, 3Alexander W.S. Starr R. Fenner J.E. Scott C.L. Handman E. Sprigg N.S. Corbin J.E. Cornish A.L. Darwiche R. Owczarek C.M. Kay T.W. Nicola N.A. Hertzog P.J. Metcalf D. Hilton D.J. Cell. 1999; 98: 597-608Abstract Full Text Full Text PDF PubMed Scopus (657) Google Scholar, 4Starr R. Metcalf D. Elefanty A.G. Brysha M. Willson T.A. Nicola N.A. Hilton D.J. Alexander W.S. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 14395-14399Crossref PubMed Scopus (380) Google Scholar). Dissection of the cellular and molecular mechanisms involved in the death of the Socs1-/- mice has revealed that SOCS1 is essential for the response of cells to IFN-γ and IFN-γ production (2Marine J.C. Topham D.J. McKay C. Wang D. Parganas E. Stravopodis D. Yoshimura A. Ihle J.N. Cell. 1999; 98: 609-616Abstract Full Text Full Text PDF PubMed Scopus (454) Google Scholar, 3Alexander W.S. Starr R. Fenner J.E. Scott C.L. Handman E. Sprigg N.S. Corbin J.E. Cornish A.L. Darwiche R. Owczarek C.M. Kay T.W. Nicola N.A. Hertzog P.J. Metcalf D. Hilton D.J. Cell. 1999; 98: 597-608Abstract Full Text Full Text PDF PubMed Scopus (657) Google Scholar). In the absence of SOCS1, IFN-γ levels rise, as does the responsiveness of cells bearing IFN-γ receptors (e.g. macrophages), causing an overwhelming inflammatory response that has been analyzed in great detail (1Alexander W.S. Hilton D.J. Annu. Rev. Immunol. 2004; 22: 503-529Crossref PubMed Scopus (608) Google Scholar). The key pathway involved in this complex pathologic process is the IFN-γ-mediated phosphorylation and activation of STAT1, the central signal transduction molecule required for IFN-γ signaling (3Alexander W.S. Starr R. Fenner J.E. Scott C.L. Handman E. Sprigg N.S. Corbin J.E. Cornish A.L. Darwiche R. Owczarek C.M. Kay T.W. Nicola N.A. Hertzog P.J. Metcalf D. Hilton D.J. Cell. 1999; 98: 597-608Abstract Full Text Full Text PDF PubMed Scopus (657) Google Scholar, 5Brysha M. Zhang J.G. Bertolino P. Corbin J.E. Alexander W.S. Nicola N.A. Hilton D.J. Starr R. J. Biol. Chem. 2001; 276: 22086-22089Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar). SOCS1 itself is a target of IFN-γ-induced gene expression and thereby can function to block IFN-γ signaling via a negative feedback loop (1Alexander W.S. Hilton D.J. Annu. Rev. Immunol. 2004; 22: 503-529Crossref PubMed Scopus (608) Google Scholar). Analysis of Socs1-/- mice intercrossed with mice bearing mutations in cytokine signaling pathways has additionally revealed that SOCS1 can regulate signaling from receptors other than the IFN-γR including those using the γc chain and the IL-12 receptor (6Chong M.M. Cornish A.L. Darwiche R. Stanley E.G. Purton J.F. Godfrey D.I. Hilton D.J. Starr R. Alexander W.S. Kay T.W. Immunity. 2003; 18: 475-487Abstract Full Text Full Text PDF PubMed Scopus (143) Google Scholar, 7Cornish A.L. Chong M.M. Davey G.M. Darwiche R. Nicola N.A. Hilton D.J. Kay T.W. Starr R. Alexander W.S. J. Biol. Chem. 2003; 278: 22755-22761Abstract Full Text Full Text PDF PubMed Scopus (106) Google Scholar, 8Cornish A.L. Davey G.M. Metcalf D. Purton J.F. Corbin J.E. Greenhalgh C.J. Darwiche R. Wu L. Nicola N.A. Godfrey D.I. Heath W.R. Hilton D.J. Alexander W.S. Starr R. J. Immunol. 2003; 170: 878-886Crossref PubMed Scopus (61) Google Scholar, 9Diehl S. Anguita J. Hoffmeyer A. Zapton T. Ihle J.N. Fikrig E. Rincon M. Immunity. 2000; 13: 805-815Abstract Full Text Full Text PDF PubMed Scopus (321) Google Scholar, 10Eyles J.L. Metcalf D. Grusby M.J. Hilton D.J. Starr R. J. Biol. Chem. 2002; 277: 43735-43740Abstract Full Text Full Text PDF PubMed Scopus (93) Google Scholar). This stands in contrast to the inhibitory effects of SOCS2 and SOCS3 that function to block a more limited number of cytokine signaling events (1Alexander W.S. Hilton D.J. Annu. Rev. Immunol. 2004; 22: 503-529Crossref PubMed Scopus (608) Google Scholar). A surprising set of results was recently published showing SOCS1 also regulates Toll-like receptor (TLR) signaling (11Nakagawa R. Naka T. Tsutsui H. Fujimoto M. Kimura A. Abe T. Seki E. Sato S. Takeuchi O. Takeda K. Akira S. Yamanishi K. Kawase I. Nakanishi K. Kishimoto T. Immunity. 2002; 17: 677-687Abstract Full Text Full Text PDF PubMed Scopus (552) Google Scholar, 12Kinjyo I. Hanada T. Inagaki-Ohara K. Mori H. Aki D. Ohishi M. Yoshida H. Kubo M. Yoshimura A. Immunity. 2002; 17: 583-591Abstract Full Text Full Text PDF PubMed Scopus (550) Google Scholar). TLRs are a group of 10–11 surface transmembrane proteins that contribute to the sensing of conserved microbial structures, such as lipopolysaccharide (LPS), detected by TLR4 or flagellin that signals through TLR5 (13Akira S. Takeda K. Nat. Rev. Immunol. 2004; 4: 499-511Crossref PubMed Scopus (6751) Google Scholar). TLRs function in higher order signaling complexes that lead, in part, to the rapid activation of NF-κB and MAP kinase signaling and the subsequent production of cytokines and chemokines by cells such as macrophages and dendritic cells (13Akira S. Takeda K. Nat. Rev. Immunol. 2004; 4: 499-511Crossref PubMed Scopus (6751) Google Scholar). The activation of TLR signaling is an essential and conserved mechanism to activate the innate immune system. The authors of the aforementioned papers established that the absence of SOCS1 caused increased lethality when mice were exposed to LPS and that TLR-stimulated macrophages from Socs1-/- mice nitric oxide with (11Nakagawa R. Naka T. Tsutsui H. Fujimoto M. Kimura A. Abe T. Seki E. Sato S. Takeuchi O. Takeda K. Akira S. Yamanishi K. Kawase I. Nakanishi K. Kishimoto T. Immunity. 2002; 17: 677-687Abstract Full Text Full Text PDF PubMed Scopus (552) Google Scholar, 12Kinjyo I. Hanada T. Inagaki-Ohara K. Mori H. Aki D. Ohishi M. Yoshida H. Kubo M. Yoshimura A. Immunity. 2002; 17: 583-591Abstract Full Text Full Text PDF PubMed Scopus (550) Google Scholar). that of SOCS1 in macrophages TLR4 signaling (11Nakagawa R. Naka T. Tsutsui H. Fujimoto M. Kimura A. Abe T. Seki E. Sato S. Takeuchi O. Takeda K. Akira S. Yamanishi K. Kawase I. Nakanishi K. Kishimoto T. Immunity. 2002; 17: 677-687Abstract Full Text Full Text PDF PubMed Scopus (552) Google Scholar, 12Kinjyo I. Hanada T. Inagaki-Ohara K. Mori H. Aki D. Ohishi M. Yoshida H. Kubo M. Yoshimura A. Immunity. 2002; 17: 583-591Abstract Full Text Full Text PDF PubMed Scopus (550) Google Scholar). on SOCS1 was to inhibit TLR signaling the in the TLR signal transduction by SOCS1 were However, SOCS proteins are established to target tyrosine phosphorylation the TLR signaling are by phosphorylation (13Akira S. Takeda K. Nat. Rev. Immunol. 2004; 4: 499-511Crossref PubMed Scopus (6751) Google the inhibition of TLR signaling to with of the events that TLR signaling. In previous established that SOCS1 expression is by TLR4 signaling via the effects of IFN-α/β A. J. 2000; PubMed Scopus Google Scholar). We using Socs1-/- mice and macrophages to for the that SOCS1 can regulate TLR signaling. The that is no evidence for such a for In we find that SOCS1 is a regulator of IFN-α/β signaling via effects of TYK2, a JAK family member required for IFN-α/β signaling. TLR signaling induces IFN-α/β from macrophages with LPS A. J. 2000; PubMed Scopus Google Scholar, K. M.J. Zhang S. J. T.A. M.J. Nat. Immunol. 2002; PubMed Scopus Google we that previous linking SOCS1 and TLR signaling are most likely mediated through the regulation of IFN-α/β signaling. mice were from and been in detail (2Marine J.C. Topham D.J. McKay C. Wang D. Parganas E. Stravopodis D. Yoshimura A. Ihle J.N. Cell. 1999; 98: 609-616Abstract Full Text Full Text PDF PubMed Scopus (454) Google Scholar). Socs1-/- mice on or been (2Marine J.C. Topham D.J. McKay C. Wang D. Parganas E. Stravopodis D. Yoshimura A. Ihle J.N. Cell. 1999; 98: 609-616Abstract Full Text Full Text PDF PubMed Scopus (454) Google Scholar, T. Tsutsui H. Fujimoto M. H. R. M. K. T. Nakanishi K. Kishimoto T. 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Immunol. 2001; PubMed Scopus Google Scholar). in macrophages was to the by and J. Immunol. 2000; PubMed Scopus Google Scholar). and levels were in the by after the LPS R. P.J. J. Immunol. 2002; PubMed Scopus Google Scholar). TLR to and in the of of in using macrophages from Socs1-/- mice SOCS1 was to regulate TLR signaling. In response to that the absence of SOCS1 TLR signaling, we established to test this We TLR signaling by the in Socs1-/- macrophages isolated from the bone of of two pathways of TLR the activation of NF-κB through the phosphorylation and degradation of and the activation of from Socs1-/- or macrophages were with LPS, or dsRNA, agonists of and by using specific for the phosphorylated of or ERK, the absence of SOCS1 no on the or on the of proteins We isolated from Socs1-/- mice on to to were in TLR signaling in the absence of were isolated from Socs1-/- mice on or and with LPS or and phosphorylation was as we found for Socs1-/- macrophages, to evidence to the that the absence of SOCS1 TLR signaling in of or does phosphorylation and degradation or phosphorylation on genetic that lethality caused by the absence of cells were isolated from or mice and to were with LPS or and analyzed as in the to are of two SOCS1 the of to the SOCS1 was an of production (11Nakagawa R. Naka T. Tsutsui H. Fujimoto M. Kimura A. Abe T. Seki E. Sato S. Takeuchi O. Takeda K. Akira S. Yamanishi K. Kawase I. Nakanishi K. Kishimoto T. Immunity. 2002; 17: 677-687Abstract Full Text Full Text PDF PubMed Scopus (552) Google Scholar, 12Kinjyo I. Hanada T. Inagaki-Ohara K. Mori H. Aki D. Ohishi M. Yoshida H. Kubo M. Yoshimura A. Immunity. 2002; 17: 583-591Abstract Full Text Full Text PDF PubMed Scopus (550) Google a pathway on the TLR and IFN-γ signaling. To test this, we isolated from Socs1-/- mice or mice inflammatory macrophages from Socs1-/-;IFN-γ-/- mice or from or Socs1-/- on or and with TLR agonists in the presence or absence of IFN-γ. levels were using the was in macrophages with TLR agonists and IFN-γ in However, the absence of SOCS1 to production in SOCS1 the of to when macrophages are exposed to LPS for to days and and with In macrophages, the is associated with a to The of macrophages after the has been to a of challenge, such as in that macrophages to endotoxin (11Nakagawa R. Naka T. Tsutsui H. Fujimoto M. Kimura A. Abe T. Seki E. Sato S. Takeuchi O. Takeda K. Akira S. Yamanishi K. Kawase I. Nakanishi K. Kishimoto T. Immunity. 2002; 17: 677-687Abstract Full Text Full Text PDF PubMed Scopus (552) Google Scholar). To test this, we using established J. Immunol. 2000; PubMed Scopus Google Scholar). were with LPS for or and for an of inflammatory cytokines were in the by In contrast to previous we find no evidence that the absence of SOCS1 the of macrophages to to endotoxin as by the inhibition of IL-12 or and by with Socs1-/-;IFN-γ-/- Mice to that Socs1-/- mice are susceptible to endotoxin (11Nakagawa R. Naka T. Tsutsui H. Fujimoto M. Kimura A. Abe T. Seki E. Sato S. Takeuchi O. Takeda K. Akira S. Yamanishi K. Kawase I. Nakanishi K. Kishimoto T. Immunity. 2002; 17: 677-687Abstract Full Text Full Text PDF PubMed Scopus (552) Google Scholar, 12Kinjyo I. Hanada T. Inagaki-Ohara K. Mori H. Aki D. Ohishi M. Yoshida H. Kubo M. Yoshimura A. Immunity. 2002; 17: 583-591Abstract Full Text Full Text PDF PubMed Scopus (550) Google Scholar). In mice were also more susceptible than that gene of to a in the response of the to We to test In we used Socs1-/- mice on an to the to mice than days of mice are more to LPS than A.L. P.J. Cell. Biol. 2003; PubMed Scopus Google Scholar). of and mice were and with LPS and A was the absence of IFN-γ signaling endotoxin L. S. P. D. M. J. PubMed Scopus Google Scholar). In with previous we found that mice with However, was no of in contrast to that of a single allele of on an increased lethality (11Nakagawa R. Naka T. Tsutsui H. Fujimoto M. Kimura A. Abe T. Seki E. Sato S. Takeuchi O. Takeda K. Akira S. Yamanishi K. Kawase I. Nakanishi K. Kishimoto T. Immunity. 2002; 17: 677-687Abstract Full Text Full Text PDF PubMed Scopus (552) Google Scholar). In contrast to previous that used limited of mice used mice with mice to that was no evidence for effects of on the to endotoxin SOCS1 IFN-α/β of Socs1-/-;IFN-γ-/- mice to endotoxin that SOCS1 was essential to regulate a of IFN-γ that was in the response to evidence for a of SOCS1 in regulating TLR signaling was we to a for SOCS1 in pathways to innate immune that contribute to endotoxin to LPS, macrophages levels of IFN-α/β that as an of macrophages, and dendritic all of contribute to the innate response to LPS A. J. 2000; PubMed Scopus Google Scholar, K. M.J. Zhang S. J. T.A. M.J. Nat. Immunol. 2002; PubMed Scopus Google Scholar). IFN-α/β production a in the regulation of the inflammatory response to LPS mice lacking mice lacking signals through the are to LPS that IFN-β signaling a in M. R. P. M. U. T. C. T. D. T. M. Nat. Immunol. 2003; 4: PubMed Scopus Google Scholar). Furthermore, TYK2, a JAK family member that regulates cytokine signaling from the is also involved in endotoxin mice are to LPS M. R. P. M. U. T. C. T. D. T. M. Nat. Immunol. 2003; 4: PubMed Scopus Google Scholar, K. K. A. T. K. M. Immunol. 2004; PubMed Scopus Google Scholar). we that SOCS1 regulate IFN-α/β signaling in activated macrophages through TYK2, and this for the lethality in Socs1-/-;IFN-γ-/- To test this, we isolated from Socs1-/- mice and with IFN-β and phosphorylation by We found that the absence of SOCS1 a in phosphorylation when macrophages are with IFN-β To this we Socs1-/- macrophages with IFN-γ or IFN-β for and the The in phosphorylation was We found that phosphorylation by IFN-β was increased in Socs1-/- cells with confirming the that SOCS1 is an of IFN-α/β signaling in to its essential in blocking IFN-γ signaling through the IFN-α/β receptor that of and we biochemical evidence for a of SOCS1 in regulating IFN-α/β signaling in macrophages, we genetic evidence for a of SOCS1 in regulating IFN-α/β signaling. We mice to mice lacking SOCS1, TYK2, and IFN-γ in The the IFN-γ allele to for the the from the SOCS1 (3Alexander W.S. Starr R. Fenner J.E. Scott C.L. Handman E. Sprigg N.S. Corbin J.E. Cornish A.L. Darwiche R. Owczarek C.M. Kay T.W. Nicola N.A. Hertzog P.J. Metcalf D. Hilton D.J. Cell. 1999; 98: 597-608Abstract Full Text Full Text PDF PubMed Scopus (657) Google Scholar, 5Brysha M. Zhang J.G. Bertolino P. Corbin J.E. Alexander W.S. Nicola N.A. Hilton D.J. Starr R. J. Biol. Chem. 2001; 276: 22086-22089Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar). effects of of on the lethality caused by SOCS1 were in the of mice of a single allele of rescued Socs1-/- mice that were also mice were and days after Socs1-/- mice are all the of and most die by days after is to the early effects of SOCS1 A was on mice that SOCS1 were die days from a from the Socs1-/- mice D. L. S. L. Alexander W.S. Proc. Natl. Acad. Sci. U. S. A. 2000; PubMed Scopus Google Scholar). We or mice that were and mice with of has to days This that of or two of can also inhibit the effects of IFN-γ in the that of lethality caused by the absence of This that SOCS1 regulates signaling and IFN-α/β of a of the of mice mice to mice to mice to number of mice in group to number of mice in group to number of mice in group to number of mice in group to The number of mice in group to in a results that SOCS1 no in TLR signaling. We found no evidence for effects of the absence of SOCS1 on signaling pathways for the of innate immune responses. In we found an for SOCS1 in regulating IFN-α/β signaling. This pathway most likely for effects of the absence of SOCS1 in LPS published (11Nakagawa R. Naka T. Tsutsui H. Fujimoto M. Kimura A. Abe T. Seki E. Sato S. Takeuchi O. Takeda K. Akira S. Yamanishi K. Kawase I. Nakanishi K. Kishimoto T. Immunity. 2002; 17: 677-687Abstract Full Text Full Text PDF PubMed Scopus (552) Google Scholar, 12Kinjyo I. Hanada T. Inagaki-Ohara K. Mori H. Aki D. Ohishi M. Yoshida H. Kubo M. Yoshimura A. Immunity. 2002; 17: 583-591Abstract Full Text Full Text PDF PubMed Scopus (550) Google linking SOCS1 to the inhibition of TLR signaling in We genetic and biochemical to that isolated from Socs1-/- mice or Socs1-/- mice on genetic TLR signaling to TLR This was was no evidence to that TLR signaling, a pathway by by SOCS all of bind via SH2 a for SOCS1 in regulating TLR signaling were in from SOCS1 in macrophages (11Nakagawa R. Naka T. Tsutsui H. Fujimoto M. Kimura A. Abe T. Seki E. Sato S. Takeuchi O. Takeda K. Akira S. Yamanishi K. Kawase I. Nakanishi K. Kishimoto T. Immunity. 2002; 17: 677-687Abstract Full Text Full Text PDF PubMed Scopus (552) Google Scholar, 12Kinjyo I. Hanada T. Inagaki-Ohara K. Mori H. Aki D. Ohishi M. Yoshida H. Kubo M. Yoshimura A. Immunity. 2002; 17: 583-591Abstract Full Text Full Text PDF PubMed Scopus (550) Google Scholar). genetic established that expression of SOCS family members to effects on cytokine and other signaling pathways (1Alexander W.S. Hilton D.J. Annu. Rev. Immunol. 2004; 22: 503-529Crossref PubMed Scopus (608) Google Scholar). the effects of SOCS1 on TLR signaling to a SOCS1 was also to regulate endotoxin (11Nakagawa R. Naka T. Tsutsui H. Fujimoto M. Kimura A. Abe T. Seki E. Sato S. Takeuchi O. Takeda K. Akira S. Yamanishi K. Kawase I. Nakanishi K. Kishimoto T. Immunity. 2002; 17: 677-687Abstract Full Text Full Text PDF PubMed Scopus (552) Google Scholar, 12Kinjyo I. Hanada T. Inagaki-Ohara K. Mori H. Aki D. Ohishi M. Yoshida H. Kubo M. Yoshimura A. Immunity. 2002; 17: 583-591Abstract Full Text Full Text PDF PubMed Scopus (550) Google Scholar). We found results using a rigorously endotoxin We that Socs1-/-;IFN-γ-/- mice were to In contrast to previous we find no evidence for effects of gene on endotoxin (11Nakagawa R. Naka T. Tsutsui H. Fujimoto M. Kimura A. Abe T. Seki E. Sato S. Takeuchi O. Takeda K. Akira S. Yamanishi K. Kawase I. Nakanishi K. Kishimoto T. Immunity. 2002; 17: 677-687Abstract Full Text Full Text PDF PubMed Scopus (552) Google Scholar). this from the of mice used by other and the of LPS on I. Hanada T. Inagaki-Ohara K. Mori H. Aki D. Ohishi M. Yoshida H. Kubo M. Yoshimura A. Immunity. 2002; 17: 583-591Abstract Full Text Full Text PDF PubMed Scopus (550) Google Scholar). In we used of mice using on mice are to endotoxin an for IFN-γ signaling in the in L. S. P. D. M. J. PubMed Scopus Google Scholar). We were thus that Socs1-/-;IFN-γ-/- mice were susceptible to LPS This that SOCS1 in the inflammatory other than the of IFN-γ or its signaling can the SOCS1 including of or J.L. Metcalf D. Grusby M.J. Hilton D.J. Starr R. J. Biol. Chem. 2002; 277: 43735-43740Abstract Full Text Full Text PDF PubMed Scopus (93) Google Scholar, T. Tsutsui H. Fujimoto M. H. R. M. K. T. Nakanishi K. Kishimoto T. Immunity. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). The absence of on a Socs1-/- that SOCS1 is a regulator of IL-12 signaling, this member is by the J.L. Metcalf D. Grusby M.J. Hilton D.J. Starr R. J. Biol. Chem. 2002; 277: 43735-43740Abstract Full Text Full Text PDF PubMed Scopus (93) Google Scholar). However, the also to activate the receptor and phosphorylation K. K. K. T. A. M. M. A. K. S. S. H. K. K. T. T. S. Immunity. 2000; 13: Full Text Full Text PDF PubMed Scopus Google Scholar, K. Tsutsui H. K. K. T. A. K. T. H. T. H. T. S. K. Nakanishi K. M. 2002; PubMed Scopus Google Scholar). is also used by the an in the response to or mice are to LPS M. R. P. M. U. T. C. T. D. T. M. Nat. Immunol. 2003; 4: PubMed Scopus Google Scholar, K. K. A. T. K. M. Immunol. 2004; PubMed Scopus Google Scholar). on we that a target of SOCS1, the of Socs1-/-;IFN-γ-/- mice to To test this, we isolated macrophages from Socs1-/- mice and with IFN-β and is activated phosphorylation of the We found that phosphorylation is in this biochemical evidence that SOCS1 an obligate in IFN-α/β signaling in to its established in IFN-γ signaling. in cells that SOCS1 was of phosphorylation from the M.M. K. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar). However, using the authors also SOCS3 inhibit and IFN-γR signaling M.M. K. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google a of SOCS by subsequent in cells and mice (1Alexander W.S. Hilton D.J. Annu. Rev. Immunol. 2004; 22: 503-529Crossref PubMed Scopus (608) Google Scholar). we genetic evidence that is involved in SOCS1 function by showing that Socs1-/- mice can rescued by the absence of a single allele of and that of can the of is to from IL-12 and IFN-α/β in this of can also Socs1-/- mice from early lethality J.L. Metcalf D. Grusby M.J. Hilton D.J. Starr R. J. Biol. Chem. 2002; 277: 43735-43740Abstract Full Text Full Text PDF PubMed Scopus (93) Google Scholar). This also does the effects of the absence of on the of mice to and to IFN-γ. is that the of and mice effects on IFN-γ in the that the mice to the inflammatory response that in the absence of SOCS1, in to specific effects on IL-12 and IFN-α/β signaling as as cytokine receptors that In we find that SOCS1, an protein that binds in its targets, does regulate TLR signaling, a set of pathways by that SOCS1 regulates IFN-α/β signaling through effects on and that previous effects of SOCS1 on TLR signaling are more likely the of or with IFN-α/β by TLR signaling. This pathway a target in the for of the inflammatory response and thereby a target for We K. for the of the mice and Alexander for results to