Jak/Stat Signaling: IL-6 Receptor Family

• 
• Description
• Reviews
• Key
• Download PDF
• Product Pathways

Search this pathway for protein information from PhosphoSitePlus^®, our expert-curated knowledge base of protein phosphorylation and other post-translational modifications.

Pathway Description:

Jaks and Stats are critical components of many cytokine receptor systems, regulating growth, survival, differentiation and pathogen resistance. An example of these pathways is shown for the IL-6 (or gp130) family of receptors, which co-regulate B cell differentiation, plasmacytogenesis and the acute phase reaction. Cytokine binding induces receptor dimerization, activating the associated Jaks, which phosphorylate themselves and the receptor. The phosphorylated sites on the receptor and Jaks serve as docking sites for the SH2-containing Stats, such as Stat3, and for SH2-containing proteins and adaptors that link the receptor to MAP kinase, PI3K/Akt, and other cellular pathways.

Receptor-bound Stats phosphorylated by Jaks dimerize and translocate into the nucleus to regulate target gene transcription. Members of the suppressor of cytokine signaling (SOCS) protein family dampen receptor signaling via homologous or heterologous feedback regulation. Jaks or Stats can also participate in signaling through other receptor classes, as outlined in the Jak/Stat Utilization Table.

Deregulated signaling of IL-6 is seen in the pathogenesis of autoimmune diseases, inflammation, and cancers such as multiple myeloma and prostate cancer. Stat3 can act as an oncogene and is constitutively active in many cancers. In prostate cancer and multiple myeloma, signaling from the IL-6R involves cross talk with Epidermal Growth Factor Receptor (EGFR) family members. IL-6 also induces anti-apoptotic signals, which may contribute to oncogenesis. One target gene is a Bcl-2 family member, Mcl-1.

Janus kinase mutations are major molecular events in human hematological malignancies. A unique somatic mutation in the Jak2 pseudokinase domain (V617F) occurs in >90% of polycythemia vera patients, and in a large proportion of essential thrombocythemia and idiopathic myelofibrosis patients. This mutation results in the pathologic activation Jak2 kinase, which leads to malignant transformation of hematopoietic progenitors. Several Jak3 pseudokinase domain mutations, present in some patients with acute megakaryoblastic leukemia, also render Jak3 constitutively active. Somatic acquired gain-of-function mutations in Jak1 have been discovered in approximately 20% of adult T-cell acute lymphoblastic leukemia.

Somatic activating mutations in Jak1, Jak2 and Jak3 have been identified in pediatric acute lymphoblastic leukemia (ALL) patients. Jak2 mutations have been detected around pseudokinase domain R683 (R683G or DIREED) in Down syndrome and pediatric B-ALL patients, where they are also associated with translocations or mutations (F232C) in the CRLF2 gene, which codes for the thymic stromal lymphopoietin receptor (TLSP) receptor. Although TLSP was thought to signal via other Jaks, it appears that mutant Jak2 and TLSPR cooperate to promote oncogenesis in a fraction of pediatric ALL.

Selected Reviews:

• Constantinescu SN, Girardot M, Pecquet C (2008) Mining for JAK-STAT mutations in cancer. Trends Biochem. Sci. 33(3), 122–31.
• Haan C, Kreis S, Margue C, Behrmann I (2006) Jaks and cytokine receptors--an intimate relationship. Biochem. Pharmacol. 72(11), 1538–46.
• Murray PJ (2007) The JAK-STAT signaling pathway: input and output integration. J. Immunol. 178(5), 2623–9.
• O'Sullivan LA, Liongue C, Lewis RS, Stephenson SE, Ward AC (2007) Cytokine receptor signaling through the Jak-Stat-Socs pathway in disease. Mol. Immunol. 44(10), 2497–506.
• Xu D, Qu CK (2008) Protein tyrosine phosphatases in the JAK/STAT pathway. Front. Biosci. 13, 4925–32.
• Yoshimura A (2006) Signal transduction of inflammatory cytokines and tumor development. Cancer Sci. 97(6), 439–47.
• Yu H, Pardoll D, Jove R (2009) STATs in cancer inflammation and immunity: a leading role for STAT3. Nat. Rev. Cancer 9(11), 798–809.

We would like to thank Prof. Stefan N. Constantinescu, Ludwig Institute for Cancer Research, Brussels, Belgium, for contributing to this diagram.