Two Different Epitopes of the Signal Transducer gp130 Sequentially Cooperate on IL-6-Induced Receptor Activation

Abstract

Cytokines are key mediators for the regulation of hemopoiesis and the coordination of immune responses. They exert their various functions through activation of specific cell surface receptors, thereby initiating intracellular signal transduction cascades which lead to defined cellular responses. As the common signal-transducing receptor subunit of at least seven different cytokines, gp130 is an important member of the family of hemopoietic cytokine receptors which are characterized by the presence of at least one cytokine-binding module. Mutants of gp130 that either lack the Ig-like domain D1 (ΔD1) or contain a distinct mutation (F191E) within the cytokine-binding module have been shown to be severely impaired with respect to IL-6 induced signal transduction. After cotransfection of COS-7 cells with a combination of both inactive gp130 mutants, signal transduction in response to IL-6 is restored. Whereas cells transfected with ΔD1 do not bind IL-6/sIL-6R complexes, cells transfected with the F191E mutant bind IL-6/sIL-6R with low affinity. Combination of ΔD1 and F191E, however, leads to high-affinity ligand binding. These data suggest that two different gp130 epitopes, one on each receptor chain, sequentially cooperate in asymmetrical binding of IL-6/IL-6R in a tetrameric signaling complex. On the basis of our data, a model for the mechanism of IL-6-induced gp130 activation is proposed.

Constitutively Active Mutant gp130 Receptor Protein from Inflammatory Hepatocellular Adenoma Is Inhibited by an Anti-gp130 Antibody That Specifically Neutralizes Interleukin 11 Signaling

“…The binding of IL-6 and IL-11 to gp130 is mediated by the D1 domain of gp130 via site III of IL-6/IL-11 and the CBM of gp130 via site II of IL-6/IL-11 (17). A gp130 receptor lacking the Ig-like domain 1 (gp130⌬D1) is functionally inactive because gp130⌬D1 cannot form homodimers because of the missing binding site III for IL-6/IL-11 (18). To answer the question whether the D1 domain is crucial for the biological activity of gp130⌬YY, we genetically deleted the D1 domain from gp130⌬YY-myc (named gp130⌬D1⌬YY-myc) and generated Ba/F3-gp130-gp130⌬D1⌬YY-myc cells (Fig.…”

Human Primary Keratinocytes Show Restricted Ability to Up-regulate Suppressor of Cytokine Signaling (SOCS)3 Protein Compared with Autologous Macrophages

“…Downstream of the IL-27 receptor both STAT1 and STAT3 are activated and coordinate the pleiotropic effects of IL-27 on a variety of different cell types of the innate and adaptive immune systems (2,(5)(6)(7). Initially, IL-27 was identified to act as a Th1 polarizing mediator (6,8), a well known function of IL-12 family members. By acting directly on naive T cells it sensitizes CD4…”

An Essential Role for gp130 in Neointima Formation Following Arterial Injury

“…The IL-6 family of cytokines uses gp130 as an integral part of their cognate receptor complex in mediating its cellular effects. 6,7 To test whether IL-6 activates gp130 in VSMCs, quiescent cells were treated with and without IL-6 (20 ng/mL) for the indicated times and an equal amount of protein from control and each treatment was analyzed for gp130 tyrosine phosphorylation via immunoprecipitation using anti-gp130 antibodies followed by immunoblotting with anti-PY20 antibodies. IL-6 stimulated tyrosine phosphorylation of gp130 in a time-dependent manner in VSMCs ( Figure 3A, top).…”

“…2,4,5 The IL-6 family of cytokines mediates its cellular effects via the signal transducer gp130. 6,7 IL-6, on binding to its soluble receptor, leads to homodimerization and activation of gp130. 7 Activated gp130 recruits nonreceptor tyrosine kinases such as Jaks.…”