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Signal transduction of IL-6, leukemia-inhibitory factor, and oncostatin M: structural receptor requirements for
D Anhuf1, M Weissenbach, J Schmitz
1Department of Biochemistry, Rheinisch-Westfälische Technische Hochschule (RWTH), Aachen, Germany.
Abstract:
Stimulation of the IL-6R complex leads to Src homology domain containing tyrosine phosphatase 2 (SHP2) recruitment to the receptor subunit gp130 and its subsequent tyrosine phosphorylation. SHP2 is a two-SH2 domain-containing protein tyrosine phosphatase that is activated by many cytokines and growth factors. SHP2 counteracts the activation of transcription factors of the STAT family and the induction of IL-6-responsive genes. Tyrosine 759 of gp130, the signal transducing subunit of the IL-6R complex, is essential for the phosphorylation of SHP2. Mutation of tyrosine 759 to phenylalanine leads to an enhanced inducibility of IL-6-dependent genes. Here we demonstrate that no further tyrosines in the cytoplasmic part of gp130 are required for the phosphorylation of SHP2. We also tested whether the tyrosine 759 motifs in both subunits of the gp130 dimer are required for SHP2 association and tyrosine phosphorylation. Interestingly, one SHP2-recruiting phosphotyrosine motif in a single chain of the gp130 dimer is sufficient to mediate SHP2 association to the gp130 receptor subunit and its tyrosine phosphorylation as well as to attenuate IL-6-dependent gene induction. Furthermore, we show that repression of gene induction via Y759 does not require the presence of the SHP2 and STAT recruitment sites within the same receptor subunit, but within the same receptor complex. The Y759 motif in gp130 also attenuates gene induction mediated by the oncostatin M and leukemia inhibitory factor receptor complexes, which both contain gp130 as the shared subunit.
Insights
Interleukin-6 receptor (IL-6R) complex stimulation recruits and phosphorylates SHP2 phosphatase. A single Y759 motif in gp130 is sufficient for SHP2 binding and IL-6 gene induction attenuation.
Area of Science:
- Cellular signaling pathways
- Molecular biology
- Immunology
Background:
- The Interleukin-6 receptor (IL-6R) complex is crucial for cellular responses mediated by IL-6.
- Stimulation of the IL-6R complex involves the recruitment and phosphorylation of Src homology domain containing tyrosine phosphatase 2 (SHP2) to the gp130 receptor subunit.
- SHP2 plays a role in counteracting STAT transcription factors and IL-6-responsive gene induction.
Purpose of the Study:
- To investigate the role of tyrosine 759 (Y759) of gp130 in SHP2 recruitment and phosphorylation.
- To determine if other tyrosines in gp130 are necessary for SHP2 phosphorylation.
- To elucidate the requirement of Y759 motifs in gp130 dimers for SHP2 association and IL-6 signaling attenuation.
Main Methods:
- Site-directed mutagenesis of gp130 tyrosine residues.
- Analysis of SHP2 recruitment and tyrosine phosphorylation.
- Assessment of IL-6-dependent gene induction.
- Investigation of receptor complex stoichiometry.
Main Results:
- Mutation of Y759 to phenylalanine enhances IL-6-dependent gene induction, highlighting Y759's inhibitory role.
- No other tyrosines in the cytoplasmic domain of gp130 are essential for SHP2 phosphorylation.
- A single Y759 phosphotyrosine motif in one gp130 chain is sufficient for SHP2 binding, phosphorylation, and attenuation of IL-6-induced gene expression.
- Repression of gene induction by Y759 does not require SHP2 and STAT recruitment sites on the same subunit, but within the same receptor complex.
- The Y759 motif in gp130 also attenuates gene induction mediated by related receptor complexes (Oncostatin M and Leukemia Inhibitory Factor).
Conclusions:
- Tyrosine 759 of gp130 is a critical site for SHP2 recruitment and phosphorylation, negatively regulating IL-6 signaling.
- The presence of a single Y759 motif within the gp130 dimer is sufficient to mediate SHP2-dependent attenuation of IL-6-induced gene expression.
- This regulatory mechanism involving Y759 and SHP2 is conserved across related cytokine receptor complexes sharing the gp130 subunit.