The Cytoplasmic Tyrosine Motifs in Full-Length Glycoprotein 130 Have Different Roles in IL-6 Signal Transduction

Abstract

The function of the signal-transducing receptor subunit glycoprotein 130 (gp130) in the IL-6-receptor complex has previously been studied using carboxyl-terminal deletion mutants or a truncated molecule of ∼60 membrane-proximal amino acids (containing box 1 and box 2) linked to the individual gp130 tyrosine motifs. However, the redundancy of the tyrosine motifs within the cytoplasmic part of gp130 has been neglected. Here we describe the analysis of the function of the individual cytoplasmic tyrosine residues of gp130 in the context of the full-length receptor protein in IL-6 signaling as measured by STAT activation, acute phase protein induction, and stimulation of proliferation. Add-back receptor mutants containing only one cytoplasmic tyrosine have been generated and tested for their efficiency in IL-6 signal transduction. Our studies revealed that tyrosine motifs which have been described to recruit STAT proteins are not equivalent with respect to their potential to activate STAT factors and acute phase protein gene promoters: the two distal tyrosines, Tyr905 and Tyr915, of gp130 were more potent than Tyr767 and Tyr814. Surprisingly, Tyr905 and Tyr915 mediate acute phase protein gene promoter activation stronger than the wild-type receptor containing all six cytoplasmic tyrosine residues. In contrast, Ba/F3 cells stably transfected with add-back receptors containing Tyr767 or Tyr905 were more sensitive to IL-6-induced proliferation than cells expressing the other add-back receptor mutants. Thus, the tyrosine residues in the cytoplasmic part of gp130 were found to contribute differentially to IL-6 signal transduction in the full- length gp130 protein.

IL-1β Induces IL-6 Expression in Human Orbital Fibroblasts: Identification of an Anatomic-Site Specific Phenotypic Attribute Relevant to Thyroid-Associated Ophthalmopathy

“…Its activation is mediated through multiple, nonequivalent gp130 motifs (56). Following binding to gp130, STAT3 becomes phosphorylated at Tyr 705 , leading to dimerization (57,58).…”

Dual Function of Interleukin-1β for the Regulation of Interleukin-6-induced Suppressor of Cytokine Signaling 3 Expression

“…To be able to specifically stimulate the population of transfected cells, we co-transfected expression vectors for chimeric receptors composed of the extracellular part of the EpoR and the transmembrane and cytoplasmic part of gp130. These well established receptors allowed us to analyze gp130-dependent signaling in response to Epo (26,31). In Fig.…”

Analysis of IL-6-mediated growth control of myeloma cells using a gp130 chimeric receptor approach

“…Indeed, numerous studies have documented the feasibility of chimeric receptor systems in a variety of cell types. 10,21,24,25 Although a chimeric receptor system has not been previously used to directly study IL-6-stimulated myeloma cell growth, IL-3-dependent Ba/F3 murine pre-B cells transfected with human gp130 displayed a proliferative response upon stimulation with soluble IL-6R and IL-6. This system further demonstrated that Ba/F3 cells only required a 61-amino acid region of gp130 proximal to the transmembrane region in the proliferative response to IL-6 and soluble IL-6R.…”

“…10,[19][20][21][22][23] The altered extracellular domain of the chimera allows receptor activation via a ligand that normally induces no cellular response thereby allowing definition of the requisite signaling intermediates engaged by the cytoplasmic domain of the receptor of interest. The success of this approach is critically dependent on activation of the chimeric receptor in the absence of an interaction with endogenous wild-type receptor (ie gp130).…”