Intracellular signaling prevents effective blockade of oncogenic gp130 mutants by neutralizing antibodies

Abstract

BackgroundShort in-frame deletions in the second extracellular domain of the cytokine receptor gp130 are the leading cause of inflammatory hepatocellular adenomas (IHCAs). The deletions render gp130 constitutively active. In this study we investigate the intracellular signaling potential of one of the most potent constitutively active gp130 mutants (CAgp130) found in IHCAs.ResultsTrafficking and signaling of CAgp130 were studied in stably transfected cell lines that allowed the inducible expression of CAgp130 fused to fluorescent proteins such as YFP and mCherry. In contrast to the predominantly highly glycosylated gp130 wild type (WTgp130), CAgp130 is preferentially found in the less glycosylated high-mannose form. Accordingly, the mutated receptor is retained intracellularly and therefore less prominently expressed at the cell surface. CAgp130 persistently activates Stat3 despite the presence of the feedback inhibitor SOCS3 but fails to activate Erk1/2. De novo synthesized CAgp130 signals already from the ER-Golgi compartment before having reached the plasma membrane. Cell surface expressed and endocytosed CAgp130 do not significantly contribute to signaling. As a consequence, Stat3 activation through CAgp130 cannot be inhibited by neutralizing gp130 antibodies but through overexpression of a dominant-negative Stat3 mutant.ConclusionCAgp130 and WTgp130 differ significantly with respect to glycosylation, trafficking and signaling. As a consequence of intracellular signaling pharmacological inhibition of CAgp130 will not be achieved by targeting the receptor extracellularly but by compounds that act from within the cell.

The mitochondrial-derived peptide humanin activates the ERK1/2, AKT, and STAT3 signaling pathways and has age-dependent signaling differences in the hippocampus

“…Although TFA-mediated ERK activation may lead to a substantial amount of ERK phosphorylation in the presence of SC-144, there is still the possibility that another receptor instead of GP130 may be involved in ERK phosphorylation in response to humanin (Figure 7). In fact, HEK293 cells have altered IL-6 signaling due to their lack of soluble IL-6R [38]. IPA pathway analysis suggested that a receptor tyrosine kinase (RTK) including EGFR and ErbBR may be involved in the humanin-mediated signaling pathway.…”

Interleukin-6: Biology, signaling and strategies of blockade

“…because of elimination of the di-leucine motif) exhibit stronger IL-6 dependent signaling [133]. Intracellular signaling from internalized wild type receptors have not been observed so far, although oncogenic mutants of gp130 signal from the ER-Golgi compartment or from early endosoms before reaching the plasma membrane [134,135]. Because feedback inhibition and desensitization of IL-6-induced signaling does not depend on receptor internalization but on SOCS3 protein expression [116,133], the impact of IL-6-induced receptor internalization on the quantity or quality of IL-6-signaling is still not well understood (Fig.…”

Soluble gp130 prevents interleukin-6 and interleukin-11 cluster signaling but not intracellular autocrine responses

“…Viral IL-6 from human herpesvirus 8 signals intracellularly (24,25). Moreover, intracellular signaling also occurs downstream of constitutively active gp130 variants (26,27). In the case of intracellular complex formation of IL-6:IL-6R:gp130 and signal initiation from within the endoplasmic reticulum (ER)-Golgi network (Fig.…”