Augmenter of Liver Regeneration (ALR) alters IL-6 signaling in liver cells by affecting IL-6 receptor subunits gp80 and gp130

Interleukin 6 (IL-6) is the main trigger of the acute-phase response (APR) following tissue damage, infection or inflammation. Augmenter of liver regeneration (ALR), a co-mitogen expressed in different organs, is mostly known for its hepatotrophic properties. Previously we have uncovered ALR’s dual signalling impact on hepatic APR. While exogenously-applied ALR attenuates, endogenously-overexpressed ALR enhances IL-6-induced signal transduction. Here we aim to elaborate the molecular mechanism behind these observations by in vitro experiments. HepG2 cells (w/o stable sfALR expression, HepG2-sfALR) were treated with IL-6 in presence or absence of recombinant ALR (rALR). Western-blot analysis revealed, that phosphorylation of members of IL-6 receptor signalling cascade (pJAK2, pJAK1, pSHP2) was enhanced in HepG2-sfALR cells upon IL-6 induction, while treatment with rALR attenuated their activation. Furthermore, analysing cell culture supernatants performing ELISAs we found reduced levels of the soluble IL-6 receptor subunits, sgp80 as well as sgp130, in HepG2-sfALR, whereas rALR-treatment slightly increased both in HepG2 cells. Additionally, HepG2 cells revealed diminished gp80 expression after rALR treatment which might explain the attenuated IL-6 signalling. Less expression of gp80 and increased sgp80 levels might be due to enhanced shedding by metalloproteinases (ADAM17, ADAM10), but could not be confirmed for ALR-treated cells. Analysis of the cell surface expression of gp80 will be determined by FACS. IL-6 receptor unit gp130 is mainly transcriptionally regulated and therefore mRNA expression of membrane-bound and sgp130 forms will be analyzed by quantitative RT-PCR. Our preliminary results reveal that ALR impacts IL-6 signalling at least by affecting expression of IL-6 receptor subunits.

Publication History

Article published online:
26 January 2022